Poster Abstracts
X-class flares released during the peak of the decline phase of SC24, a descriptive study
Abdel HADY, Ahmed
Eruptive X-class flares occurring during the peak and decline phases of the solar cycle 24 are stronger than those of the solar cycle 23. We notice that the solar cycle 24 is the weakest in the last 100 years. The last two cycles are very weak compared to other cycles, except for the Dalton Minimum cycles 4, 5, 6 and 7; which indicates the appearance of a new Dalton minimum during 23, 24, 25 and 26. During the last 5 solar cycles, a new peak has appeared releasing high energetic particles and X-class solar flares which are called the secondary peak or the double peak of the solar cycle.The aim of this descriptive study is to follow the X-class flares released during the peak and decline phase of SC24, once they are released, to compare it with other solar cycles.The causes of the release of such eruptive storms, through the year 2014, during the double peak of the solar cycle 24 are also discussed.
A coordinate-independent characterization of a black hole shadow
Abdujabbarov, Ahmadjon
We provide a general formalism to describe the shadow as an arbitrary polar curve expressed in terms of a Legendre expansion. Our formalism does not presume any knowledge of the properties of the shadow, e.g. the location of its centre, and offers a number of routes to characterize the distortions of the curve with respect to reference circles. These distortions can be implemented in a coordinate-independent manner by different teams analysing the same data. We show that the new formalism provides an accurate and robust description of noisy observational data, with smaller error variances when compared to previous approaches for the measurement of the distortion.
Optical properties of a braneworld black hole
Abdujabbarov, Ahmadjon
We study optical properties in terms of weak and strong (retrolensing) gravitational lensing around a black hole on the brane. The black hole is described by the Reissener-Nordström metric, where the electric charge is replaced by the Weyl tidal charge which acts in consonance with mass. It is, therefore, expected that gravitational lensing effects would be enhanced by the tidal charge, and that is what we verify. We also study the shadow of a braneworld black hole in plasma and show that the tidal charge increases the size of the black hole shadow. We finally consider energy emission from the hole by thermal radiation which is also increased due to tidal charge.
Magnetic fields of spherical compact stars in modified theories of gravity
Abdujabbarov, Ahmadjon
The stellar magnetic field configuration and solutions of Maxwell equations in the external background spacetime of a magnetized spherical stars in the Horava-Lifshitz gravity and in modified f(R) gravity are studied. The star is modeled as a sphere consisting of perfect highly magnetized fluid with infinite conductivity and frozen-in magnetic field. With respect to solutions for magnetic fields found in the Schwarzschild spacetime star in modified gravity theories, enhancing corrections are added to the exterior magnetic field. The energy losses through magnetodipolar radiation of the rotating magnetized compact star within alternative gravity theories is also considered. The question of whether these models can be considered as an alternative theory for general relativity is also discussed through astrophysical application of the obtained magnetodipolar energy loss formula. Finally we analyze the role of general relativistic effect on the decay of a neutron star’s magnetic field in modified theories of gravity.
An UXor among FUors: Extinction-related Brightness Variations of the Young Eruptive Star V582 Aur
Abraham, Peter
V582 Aur is an FU Ori-type young eruptive star in outburst since ~1985. The eruption is currently in a relatively constant plateau phase, with photometric and spectroscopic variability superimposed. Here we will characterize the progenitor of the outbursting object, explore its environment, and analyze the temporal evolution of the eruption. We are particularly interested in the physical origin of the two deep photometric dips, one that occurred in 2012 and one that is ongoing since 2016. We collected archival photographic plates and carried out new optical, infrared, and millimeter-wave photometric and spectroscopic observations between 2010 and 2018, with a high sampling rate during the current minimum. Besides analyzing the color changes during fading, we compiled multiepoch spectral energy distributions and fitted them with a simple accretion disk model. Based on pre-outburst data and a millimeter continuum measurement, we suggest that the progenitor of the V582 Aur outburst is a low-mass T Tauri star with average properties. The mass of an unresolved circumstellar structure, probably a disk, is 0.04 M ?. The optical and near-infrared spectra demonstrate the presence of hydrogen and metallic lines, show the CO band head in absorption, and exhibit a variable Ha profile. The color variations strongly indicate that both the ~1 yr long brightness dip in 2012 and the current minimum since 2016 are caused by increased extinction along the line of sight. According to our accretion disk models, the reddening changed from A V = 4.5 to 12.5 mag, while the accretion rate remained practically constant. Similarly to the models of the UXor phenomenon of intermediate- and low-mass young stars, orbiting disk structures could be responsible for the eclipses.
The nature of radio and optically variable radio sources
Abrahamyan, Hayk
We have cross-correlated NVSS and FIRST radio catalogues having radio flux measurements at the same 1.4 GHz frequency to benefit from repeated observations from both catalogues, which give more accurate positions and fluxes and more important, reveal large differences between the two measured fluxes, thus allowing to establish radio variability. 79,382 radio variables have been revealed, including 6301 with flux differences at 1.4 GHz larger than 15 mJy, 1917 with flux differences > 45 mJy and 260 with flux differences > 200 mJy. By using a special technique (Mickaelian & Sinamyan 2010, Mickaelian et al. 2011) we have revealed 2425 optically variable objects out of 6301 radio sources. We have divided 2425 radio sources with both high radio and optical variability into four categories. 1206 (19%) out of 6301 radio sources have activity types from available catalogues and 619 (25.5%) out of 2425 radio sources with at the same time radio and optical variability have activity types from available catalogues. In addition, 279 radio sources out of 2425 have high variability in optical range. We have established their activity types when available. We have studied the IR fluxes and colours for the 6301 variable radio sources. Colour-colour diagrams show that most of the “unknown” sources are galaxies. We also have retrieved the activity type for 110 (42%) out of 260 extremely high variable radio sources.
Galaxy evolution in groups observed by the Integral Field Spectrograph MUSE, a dynamical approach
Abril Melgarejo, Valentina
Galaxies are strongly affected by their environment, various mechanisms seem to occur in dense environments to remove gas efficiently from galaxies. In particular, Star forming quenching and the build up of the red sequence happen earlier in dense environments than in field (e.g. Peng et al. 2010). The goal of this project is then to understand the impact of the environment on galaxy mass assembly mechanisms and on the establishment of the Hubble sequence observed in the local Universe. The influence of the environment seems to begin to be effective between z = 0 and z = 1, when cosmic star formation begins to decrease.Studying spatially resolved and integrated properties of star forming galaxies at z<1, may help in better understanding the various processes responsible for the transition. However, up to now all this kind of studies have been performed independently from the environmental effects and in the high galaxy mass regime due to the sample structures and/or observational limitations. This project is based on the exploitation of a unique sample from GTO MUSE VLT observations targeted on groups between 0.3 <z <1,="" complemented="" for="" all="" the="" groups="" with="" hst="" images.="" current="" morpho-kinematic="" analysis="" has="" been="" performed="" on="" sample="" consisting="" so="" far="" in="" ~="" 330="" galaxies="" inside="" at="" different="" redshifts.="" we="" make="" special="" emphasis="" a="" sub-sample="" of="" 100="" z="" 0.7="" which="" obtained="" preliminary="" results="" their="" tully-fisher="" relationship.the="" spatially="" resolved="" kinematics,="" can="" better="" constrain="" processes="" galaxy="" mass="" assembly="" and="" provides="" clues="" how="" baryons="" are="" accreted="" dark="" matter="" halos.="" comparison="" similar="" studies="" low="" density="" environments="" will="" ultimately="" allow="" to="" probe="" impact="" environment="" evolution="" mechanisms="" galaxies.<="" p="">
</z></z></z></z></z></z>
NOC Activity in Nepal
Acharya, Jayanta
Nepal is least develop country lies in between two big country India and China. Despite the favorable climatic and geographical conditions, research and development of the astronomy in Nepal is very limited.To increase the astronomical awareness there should be activities in School and Public Places. Our activities aware not only to children but also to the school teachers parents and locals people in a practical way. If a children is interested in astronomy he/she continue their study in astronomy. They conduct research and development in this field.In this poaster we are showing how are are doing Astronomical activities and increasing interest for the students for the future astronomer.Key words: Astronomy, School,
Astronomy Education and outreach for Earthquake affected Nepali students.
Acharya, Jayanta
Nepali Culture has many strong believe in communicating the Astronomy. There are some superstition. People think anything happen uncertain they blame some heavenly planets stars or Moon. Still people think earthquake is just because of the planets positions. Many reputed News paper journalists goes to the local priests to ask about future earthquake and any other changes. We organized a Astronomy Activities for the Earthquake affected students in three different places Gorkha, Nuwakot and Kathmandu most earthquake affected district in Nepal. there was 8.2 magnitude earthquake in 2015, and Hundreds of thousands of people their school going children were made homeless with entire villages flattened, across many districts of the country by the earthquake. Centuries-old buildings including many schools were destroyed. We thought Astronomy may help them to forget the fear of the earthquake because of it will be unique and new for their school activities. We are focused our activities in the one, school which are most affected in Nepal. In my talk I would like to explain and how we did Authentic and scientifically explained about earthquake through Astronomy education and outreach.Keywords: Astronomy, Earthquake, Telescope.
Determining effects of telescope spatial resolution with synthetic observations of galaxy simulations
Acharyya, Ayan
How well can we recover metallicity gradient in galaxies, given telescope limitations? We produce realistic synthetic IFU data cubes from Enzo simulations of star forming disk galaxies, by including the effects of telescope resolution and instrumental noise, to understand the observation of metallicity gradients. We conduct a parameter study to specifically investigate the effect of spatial resolution and signal-to-noise ratio (SNR) on inferred metallicity gradient. I will present our new MAPPINGS photoionization models of HII regions and the steps involved to produce the mock data cubes. I will also discuss the results and their implications on the metallicity gradient measurements currently being carried out as part of large IFU surveys like SAMI. We find that, at a given spatial resolution the accuracy of the inferred gradient saturates to a “best possible” value, irrespective of how high the SNR is. The magnitude of this accuracy depends on the true gradient and the metallicity diagnostic used. I will also discuss the effects of imposing a SNR threshold criteria. In future, we plan to use other hydrodynamical simulations with different underlying physics, to generate our mock observations. Comparing the different mock observations with real IFU observations will help us constrain the physical processes in the observed galaxies.
Multiplicity Among Young Stellar Objects in Orion A
Ackerl, Christine
The initial multiplicity properties of stars carry the footprints of the mechanisms involved in their formation. Additionally, multiplicity also plays an important role in planet formation or even habitability. It is therefore inevitable to study under which circumstances stars form alone or in multiples and how their separations evolve over time. While multiplicity among main sequence stars is already well established (e.g. Duquennoy & Mayor 1991) this is not the case for young stellar objects. Studies concentrating on young binaries are mostly carried out for relatively small populations and in very distinct environments, for that reason, the results are ambivalent and leave unanswered questions. For example, whether and how does initial stellar multiplicity depend on environmental conditions? In order to provide a more complete picture, a statistically significant sample of young binaries that covers an entire star forming region with diverse physical conditions is needed. Using the Vienna Survey in Orion (Meingast et al. 2016) we are able to present the largest known sample of young visual binaries towards one single star forming cloud, the rich and nearby star forming region Orion A. The survey provides high-quality seeing limited ESO-VISTA images and JHKs-photometry for ~800,000 sources and covers a vast range of different star forming environments, from well known dense clusters to isolated (Taurus-like) environments towards the southern end of Orion A. Our sample is sensitive to separations > 300 AU and is about an order of magnitude larger when compared to previous studies in this region (e.g. Kounkel et al. 2016).
Space Mission Geometry for Almost Every Purpose
Acton, Charles
Every space mission needs some form of space geometry–positions, velocities, orientations and more–from the very earliest design stages through the analysis of science or other results that may extend to many years after the end of operations. These kinds of space geometry computations can be rather difficult to make given that everything is moving or rotating; given that a number of reference frames and coordinate systems come into play; given that estimates of size, shape and orientation of target bodies are frequently revised; and given that several time systems are used. Realizing the challenges and also the importance of making accurate space geometry computations, NASA established an organization–the Navigation and Ancillary Information Facility (NAIF) to implement a multi-mission, enduring process, named SPICE1, for computing space mission geometry. SPICE comprises both ancillary data files, called “kernels,” and a suite of software used to produce those kernels and to compute derived quantities such as altitude, latitude/longitude, lighting angles, etc. from the data contained within the kernels. The SPICE software is available in six languages, and for most popular computing environments. The software is extensively documented and throughly tested; tutorials and training classes on its use are offered. NASA offers SPICE free of charges, export restrictions and licensing arrangements: literally anyone, worldwide, can obtain and use the SPICE components. This presentation will provide examples of where and how SPICE has and is being used and it will look to the future of SPICE–what new capabilities are being added and where it might be helpful in new solar system engineering and science activities.1Spacecraft, Planet, Instrument, Camera-matrix, Events
A 3.5-million Solar Masses Black Hole in the Centre of the Ultracompact Dwarf Galaxy Fornax UCD3
Afanasiev, Anton
The origin of ultracompact dwarfs (UCDs), a class of compact stellar systems discovered two decades ago, still remains a matter of debate. Recent discoveries of central supermassive black holes in UCDs likely inherited from their massive progenitor galaxies provide support for the tidal stripping hypothesis. At the same time, on statistical grounds, some massive UCDs might be representatives of the high luminosity tail of the globular cluster luminosity function. Here we present a detection of a 3.5±1.4 × 106 MSun black hole (1s uncertainty) in the centre of the UCD3 galaxy in the Fornax cluster, that corresponds to 4% of its stellar mass. From Jeans dynamical modelling of the UCD3 internal kinematics obtained with the SINFONI spectrograph at the ESO Very Large Telescope using adaptive optics, we rule out the zero black hole mass at the 3s confidence level. This is the fourth supermassive black hole found in a UCD and the first one in the Fornax cluster. Similarly to other known UCDs that harbour black holes, UCD3 hosts metal rich stars enhanced in a-elements that supports the tidal stripping of a massive progenitor galaxy as its likely formation scenario. We estimate that up to 80% of luminous UCDs in galaxy clusters host central black holes. This fraction should be lower for UCDs in groups, because their progenitors are more likely to be dwarf galaxies, which do not tend to host very massive black holes upon formation.
Visualisation: where data meets insight
Afonso, Ana
One of the most regular activities that we are required to do in Astronomy is to present our data to others (such as papers, talks, etc). However, how well are our plots highlighting the results? I would like to demonstrate some examples of how to (and how not to) show astronomical data results and share some of tips and tricks to produce high quality and efficient ways to make data understandable to everyone.
Galaxy clusters mergers, shocks and turbulence: what are the effects on galaxy evolution?
Afonso, Ana
Galaxy populations in relaxed clusters are dominated by ellipticals. However, little is known about the effect of disturbed clusters on galaxy evolution. Merging clusters represent an extremely violent environment permeated by Mpc-wide shock waves and cluster-wide turbulence. Stroe et al. (2016) completed the first narrow-band survey of Ha emitters in a sample of low-redshift clusters sampling a range of masses and relaxation states. The results have shown that relaxed environments have 25 times fewer Ha emitters when compared to merging clusters. What drives this reversal of typical environmental trends and how could shocks and turbulence trigger star formation in cluster galaxies remains unclear. Multi-object spectroscopic observations have been obtained using VLT/VIMOS and WHT/AF2 in order to efficiently follow-up star-forming galaxies and AGNs uniformly selected in relaxed and merging clusters. This allowed us to measure the precise redshift, powering source, metallicity, electron density and ionization parameters of these sources as well as to correlate the optical spectroscopic properties with the galaxy morphologies. Given the similarities between low-redshift disturbed clusters and high-redshift protoclusters, this unique study not only provides an excellent opportunity to connect observations and theory but it may also provide important clues to the evolution of galaxies at high-redshift analogs.
On the UV compactness and morphologies of typical Lya emitters from z~ 2 to z~ 6
Afonso, Ana
Lya is, intrinsically, the strongest nebular emission line in actively star-forming galaxies (SFGs), but its resonant nature and uncertain escape fraction limit its applicability. The structure, size, and morphology may be key to understand the escape of Lya photons and the nature of Lya emitters (LAEs). In Paulino-Afonso et al. (2018) we investigate the rest-frame UV morphologies of a large sample of ~4000 LAEs from z~2 to z~6, selected in a uniform way with 16 different narrow- and medium-bands over the full COSMOS field (SC4K, Sobral et al., 2018). From the magnitudes that we measure from UV stacks, we find that these galaxies are populating the faint end of the UV luminosity function. We find also that LAEs have roughly the same morphology. The median size, ellipticities, Sérsic index, and light concentration show little to no evolution. LAEs with the highest equivalent widths are the smallest/most compact. In a scenario where galaxies with a high Lya escape fraction are more frequent in compact objects, these results are a natural consequence of the small sizes of LAEs. When compared to other SFGs, LAEs are found to be smaller at all redshifts. The difference between the two populations changing with redshift, from a factor of ~1 at z=5 to SFGs being a factor of ~2-4 larger than LAEs for z=2. This means that at the highest redshifts, where typical sizes approach those of LAEs, the fraction of galaxies showing Lya in emission should be much higher, consistent with observations. In this era of new and upcoming cutting-edge facilities, linking the theoretical perspectives and numerical simulations with the observational studies of the properties of the LAEs across the Universe seems to be a key to understand reionization and early stages of galaxy formation.
Understanding the cold circumgalactic medium around galaxies
Afruni, Andrea
The circumgalactic medium (CGM) of galaxies consists of a multiphase gas with components at very different temperatures, from 10^4 to 10^7 K. It constitutes the interface between the interstellar medium and the intergalactic medium (IGM) and modelling its kinematics and dynamics is critical for our understanding of the role of feedback and gas accretion in galaxy evolution. Moreover, the large amount of mass of this gas suggests that it can contain a significant part of the galaxy ‘missing baryons’. The most puzzling component of this medium is the low-temperature (T~10^4 K) material detected via UV-optical absorptions towards background QSOs. The ubiquitous presence of this material has recently been established both around star-forming and early-type galaxies, but the origin, dynamics and fate of this medium are still unclear. We have modelled this cold gas as an inflow of clouds from the IGM to the central galaxies and compared our model predictions with the observations of the COS-Halos collaboration. We found that in massive early-type galaxies the observed kinematics is only reproduced if the cold CGM clouds are destroyed by the hydrodynamical interactions with the hot gas and do not reach the central galaxies, explaining in this way the quenching of these passive galaxies. On the contrary, in low-mass star-forming galaxies the models successfully reproduce the kinematics with cold CGM clouds reaching the inner regions and accreting onto the central galaxies. This scenario suggests that the fate of the cold CGM has a crucial role in the evolution of star formation in galaxies. Moreover, through the comparison with the observations, our models allow us to give an estimate of the mass of the cold CGM gas in galaxies, resulting to be a significant part of the total galaxy baryonic mass.
X-ray reprocessing: Through the eclipse spectra of high and low mass X-ray binaries with XMM-NEWTON
Aftab, Nafisa
Study of X-ray reprocessing is one of the key diagnostic tool to probe the environment in X-ray binary systems. Difficult aspect to study X-ray reprocessing is the presence of primary radiation from the compact star along with the reprocessed radiation. Eclipsing X-ray binaries make an ideal condition to study reprocessed X-rays, as the X-rays detected during eclipse are purely reprocessed while the primary X-rays are blocked by the companion star. We carried out first comprehensive studies of X-ray reprocessing with a number of eclipsing High Mass X-ray Binary and Low Mass X-ray Binary (HMXB and LMXB) systems during and outside eclipse with XMM-NEWTON EPIC pn. Comparing eclipse and out-of-eclipse spectra of these sources we have found ample diversity in the X-ray reprocessing characteristics in HMXBs, even in the same source at different epochs the variation is quite large. In spite of having much weaker wind environment, the flux ratio of out-of-eclipse to eclipse in LMXBs is in a range comparable to the HMXBs. The analysis shows very strong Iron ka emission line during eclipse phases in most of the HMXBs and week or no Iron emission lines in LMXBs. Equivalent width of Iron emission lines in Supergiant Fast X-ray Transients (SFXTs) are large during eclipse, similar to that in Supergiant HMXBs (SgHMXBs). There are some significant system to system differences. For example low equivalent width of Iron ka emission line in HMXB Cen X-3 during eclipse, very week Iron emission line in HMXB SMC X-1, comparable out-of-eclipse to eclipse flux ratio in LMXB AXJ 1745.6–2901 irrespective of intensity state etc. Overall we try to infer the wind and accretion disk characteristics, which are the reprocessing agents in the HMXB and LMXB systems respectively.
On the basins of convergence of the libration point in the axisymmetric restricted five-body problem: Convex case
Aggarwal, Rajiv
In the resent paper, we have numerically explored the fractal basins of convergence associated with the libration points in the axisymmetric restricted problem of five-bodies. The four bodies are supposed to be in axisymmetric central configurations as discussed by Érdi and Czirják (2016) and the dynamics of the fifth body moving under the gravitational influence of them are analyzed. We have considered the convex case which is one of the cases of the three basic axisymmetric central configurations proposed by Érdi and Czirják. This can be visualized by taking a system of three masses on a straight line and then dividing one of the masses into two equal halves to put them up and down in such a manner that the resulting four point masses configuration is symmetric about the x-axis. The convex case is taken into consideration which can be obtained by splitting the central mass to form a four-sided polygon. We have also unveiled numerically the domain of convergence corresponding to libration points by using the multivariate version of the Newton-Raphson iterative scheme. The correlations between the basins of convergence associated with libration points and the required number of iterations corresponding to it are also presented and discussed in detail. The present numerical analysis reveal that the evolution of the attracting domains in this dynamical system is enormously complicated but worth studying issue._x005F References:_x005F Érdi, B., Czirják, Z.: Central configurations of four bodies with an axis of symmetry. Celest. Mech. Dyn. Astron. 125(1), 33–70 (2016) _x005F Gao, C., Yuan, J., Sun, C.: Equilibrium points and zero velocity surfaces in the axisymmetric restricted five-body problem. Astrophys Space Sci. 362:72 (2017)
Large-scale distribution of hot gas from Sunyaev-Zeldovich
Aghanim, Nabila
The distribution of ionised hot gas in the cosmic structure was recently unveiled through measurement of the Sunyaev-Zeldovich (SZ) effect by Planck satellite over the whole sky. I will review the main results showing how SZ effect probes the multi-scale distribution of hot gas from halos to the largest structure in the Universe.
Variability of magnetically-dominated jets in blazars and gamma ray bursts
Agnieszka, Janiuk
The fastly variable accretion flows are found in a number of different types of astrophysical black hole sources. At largest scales, they are present in the cores of active galaxies.In the radio-loud objects, such as blazars, the variability of the inflow can be transmitted to the outflow properties. In these sources,the relativistic jets are pointing to our line of sight.In addition, many similarities are found between the jet physics in blazars and in gamma ray bursts.The latter are observed from extragalactic distances, butoperate at smaller scales, within the stellar-mass accreting black holes and in collapsing star's environment.Observational studies have shown an anticorrelation between minimum variability time scale and Lorentz factor of the emitted jet.Motivated by those observational properties of black hole sources, we investigate the accretion inflow and outflow properties,by means of numerical GRMHD simulations.Our two-dimensional magneto-hydrodynamical models are computed in full General Relativity, implemented with the code HARM. The properties ofmagnetic fields and their role in evolution in the flows are studied in detail.The blazar jet is Poynting-dominated, and powered by the Blandford-Znajek mechanism which can extract energy from a rotating black hole. This mechanism is nowwell known and tested in the purpose of a jet launching, but observations are showing variability in the jet emission. Multiple shocks that collide in the jet,can lead to multiple emission episodes and can account for the fluctuating light curve. A reasonable interpretation of this effect is that the variabilityobserved in the jets can directly reflect the central engine variability. The latter is tightly related to the action of magnetic fields in the center of thegalaxy.
Relativistic Astrophysics in Uzbekistan
Ahmedov, Bobomurat
It is necessary to underline that during the last twenty years due to the help and assistance of the international scientific community there was a great success in the development and establishment of new well functioning and competitive scientific groups specialized in general relativity and relativistic astrophysics in Uzbekistan (Tashkent), Kazakhstan (Astana and Almaty), Kyrgyzstan (Bishkek). The great achievements are made in Uzbekistan (the most populated Central Asian republic), and together with our European and South Asian collaborators, we have obtained interesting results on Relativistic Astrophysics of Compact Gravitational Objects published in more than one hundred papers in the refereed journals with the involvement of European, Central and South Asian scientists.
SCALAR AND ELECTROMAGNETIC PERTURBATIONS OF NONSINGULAR NONROTATING BLACK HOLES IN CONFORMAL GRAVITY
Ahmedov, Bobomurat
We study scalar and electromagnetic perturbations of a family of nonsingular nonrotating blackhole spacetimes that are solutions in a large class of conformally invariant theories of gravity.The effective potential for scalar perturbations depends on the exact form of the scaling factor.Electromagnetic perturbations do not feel the scaling factor, and the corresponding quasinor- malmode spectrum is the same as in the Schwarzschild metric. We find that these black hole metrics arestable under scalar and electromagnetic perturbations. Assuming that the quasi- normal modespectrum for scalar perturbations is not too different from that for gravitational perturbations,we can expect that the calculation of the quasinormal mode spectrum and the observation withgravitational wave detectors of quasinormal modes from astrophysical blackholes can constrain the scaling factor and test these solutions.
PLASMA MAGNETOSPHERE OF OSCILLATING AND ROTATING MAGNETIZED NEUTRON STARS
Ahmedov, Bobomurat
We discuss a number of analytical studies, aimed at adding the influence of oscillations experienced by a pulsar/magnetar on its plasma magnetopshere. We show that particular modes ofoscillations may considerably increase the pulsar/magnetar luminosity and apply the obtainedtheoretical results on the plasma magnetosphere of oscillating and rotating neutron stars i) topropose a qualitative model for the explanation of the phenomenology of intermittent part timepulsars, ii) to study the conditions for radio emission in rotating and oscillating magnetars byfocusing on the main physical processes determining the position of their death lines, i.e. ofthose lines that separate the regions where the neutron star may be radio loud or radio quiet, iii)to explain the subpulse drift phenomena adopting the space-charge limited ow model and comparingthe plasma drift velocity in the inner region of pulsar magnetospheres with theobserved velocity of drifting subpulses.
Observability of Ancient Historical Solar Eclipses in East Asia
Ahn, Sang-Hyeon
Historical records on solar eclipses in the dynastic chronologies in East Asian history have been precious data to infer the rate of change of Earth’s rotation. However, modern calculations prove that a significant fraction of those records did not happen and that some of them had too small obscured fraction to be observed with bare-eyes. Even when the eclipse time and magnitude was given in a quantitative manner, those values do not agree with modern calculations. Hence, there has been dispute on whether they were predicted or really observed. Similarly, the totality of Ji-eclipses in ancient Chinese history has been suspected. Recently the concept of Ji-eclipse was proposed not to be exactly coincided with the modern terminology of total eclipse. Instead, it was pointed out that the eclipses whose magnitude were larger than ~0.8 were called as Ji-eclipses in the ephemeris calculations. Hence, additional descriptions such as daytime appearance of stars/planets, twilights, or arc-shaped solar disk are more concrete evidence on the totality of the eclipse records. Here in this poster the observability of ancient historical eclipse records was tested. In particular, the 1,200-year-long records, by 1000 CE, of both Chinese and Korean records were analyzed. We focused on the facts that solar eclipses can be recognized when the solar disk can be observed with bare-eyes when sun is setting or rising, and also that solar eclipse can also be observed with bare-eyes when the eclipse magnitude was nearly total. Considering atmospheric extinction, we checked the observability. As one consequence, the Korean records, having merely simple description that there was a solar eclipse and their date mostly overlapped with Chinese records and so having been suspected as being copied from Chinese chronologies, were proved to be original records of Korean astronomers rather than mere copy of Chinese records.
X-ray variations of one changing-look quasar
Ai, Yanli
We report the changing-look quasar which went through a dramatic outburst, during which its X-ray flux increased by an order of magnitude after an increase of its optical/mid-infrared continuum flux. With the appearance of broad optical emission lines, this changing-look quasar provide us with important insights about the quasar physics.
Multiple paths of deuterium fractionation in protoplanetary disks
Aikawa, Yuri
Molecular D/H ratios, such as HDO/H2O, are higher than the elemental D/H ratio in the primordial material in the Solar System, as well as in Earth’s ocean. This rather ubiquitous deuterium enrichment could originate in chemical reactions in cold environment such as molecular clouds and outer regions of protoplanetary disks, where the difference in zero-point energies between the normal and deuterated isotopologs stands out. While molecules are already deuterated in molecular clouds, the high D/H ratios of molecular ions indicate that deuteration proceeds in disks, as well. Spatial distributions of line intensities vary among deuterated species, which suggests that they have different deutration paths. Observations, however, show that their distributions also vary among disks. Motivated by these observations, we calculated a gas-grain chemical reaction network in protoplanetary disks to investigate the major deuteration paths and their dependence on disk parameters such as grain size and turbulence. Our network model includes spin-state chemistry, which is known to affect deuteration. We found multiple paths of deiuterium fractionation; exchange reactions with D atoms, such as HCO+ + D, are effective in addition to those with HD. If grains are small, freeze-out is severe in the cold midplane, while the disk surface is shielded from UV radiation to be relatively molecule-rich, which tends to make the radial distribution of molecular column density flat. As grains grow, photodissociation dominates in the disk surface, while gaseous molecules in the midplane are enhanced and contribute to line emissions. Turbulent diffusion transports D atoms and radicals at the disk surface to the midplane, and stable ice species in the midplane to the disk surface. The effects of turbulence on chemistry are thus multifold. We also derive the analytical formulas for abundances of H3+, HCO+, N2H+ and their deuterated isotopologues in the cold midplane.
The Life of The Young Sun: Biogenic Conditions on the Early Earth and Mars
Airapetian, Vladimir
The physical environments of the young Sun can provide important clues for the origin of life on the early Earth and the potential for life on early Mars. According to recent observations of young stellar solar-like stars, our 0.7 Gyr-old Sun was a magnetically active star exhibiting frequent and energetic flares, coronal mass ejections (CMEs) and fast and dense wind, and thus extreme space weather environments. These extreme events should have impacted the atmospheres of the early Earth and Mars. In order to reconstruct space weather from the young Sun, we employed a data driven three-dimensional magnetohydrodynamic Alfvén Wave Solar Model applied for k1 Cet, the best known young Sun’s proxy. Alfvén waves launched at the chromosphere dissipate into heat forming a hot and dense corona that emits intensively in EUV and X-ray bands and a fast and dense bi-modal wind.The fast wind emanating from the polar regions of the star interacts with slow wind associated with streamer belt and forms co-rotating interaction regions (CIRs) that develop into shocks. We also discuss our recent models of super-Carrington CMEs from the young Sun. The application of a 3D global magnetospheric models suggests that CME and CIR induced dynamic pressures and magnetic fields significantly perturbed the magnetospheres of the early Earth & Mars exposing 70% of their surfaces to energetic particles. Solar energetic particles accelerated on CIR and CME induced shocks could have contributed to the rise of prebiotic chemistry and the origin of life on these planets.
Analysis of data modern astrometric catalogues in GAIA era.
Akhmetov, Volodymyr
The new big catalogues of proper motion were created using of GaiaDR1 data. The names of these catalogues are HSOY, UCAC5, GPS1 and PMA. Using three or more catalogues in Wielen method it is easy to estimate the external accuracy of each of them. The random errors of stellar proper motions had been calculated based on the common objects from HSOY, UCAC5, GPS1 and PMA catalogues. From a comparison of PMA data with same stars from the UCAC5, GPS1 and HSOY catalogues, the equatorial components of the mutual rotation vector of these coordinate systems were determined. The angular velocities of mutual rotation of the PMA and UCAC5, HSOY, GPS1 reference frames change within range from 0.2 to 2.0 mas yr-1. The estimation of systematic and random errors of the stellar proper motions of the PMA, HSOY and GPS1 catalogues in the faintest magnitude range had been done via an analysis of formal proper motions of extragalactic objects are containing in these catalogues. Also, comparisons of stellar proper motions of these catalogues with Gaia DR2 data was planned to carry out, when it will be released.
Automated reduction of the photometric observations using CoLiTecVS
Akhmetov, Volodymyr
The main aim of the work is performing the automated reduction of the photometric observations in CCD-images during the variable stars research using CoLiTecVS. This is a new tool, which is able to do the following: images calibration using bias-, dark- and flat-frames, background alignment, inverse median filtration, stars identification, cross identification with astrometry catalogues, ensemble differential photometry. The result of CoLiTecVS processing is a light curve of the investigated object. The process is fully automated and can be run online during the observations. The method for estimating of brightness of the investigated star includes the following operations: selection of the comparison stars according to the proximity by distance, brightness and spectral class; excluding the comparison stars with anomaly error of instrumental brightness; calculating the brightness of the comparison stars and its reduction into the base frame; selection of the best combination of comparison stars by a minimum of the brightness RMS; calculating the brightness of the investigated star on the each frame. We've investigated the possible influence of non-linearity of median filtering on the photometry results. We didn't find measurable influence. Contrary – the background brightness equalization by inverse median filter usually provides better results as classical flat-field calibration. The photometry of constant stars obtained by CoLiTecVS was compared with the values obtained by conventional reduction process. We are working on the algorithm for automated processing to improve the photometric accuracy.
Microlensing and time delays in gravitational lensed quasars
Akhunov, Talat
Gravitational lensing offers a unique tool to study the mass distribution of the lens, the structure of the light source as well as the physics of the Universe. However, any signi?cant contribution to these endeavours requires some continuous and detailed investigations of each known gravitational lens system. Therefore, we conducted optical monitoring of the gravitationally lensed systems H1413 + 117, B1422 + 237, PG1115 + 080, SBS1520 + 530, FBQ0951 + 2635 at the Maidanak Observatory in Uzbekistan for a long time. Thus, we obtained long-term series of observations, the photometric analysis of which gave us the following results.H1413+117: we analysed the V- and R-band light curves and V–R colour variations of the A–D components which show short- and long-term brightness variations correlated with colour variations. We have derived the new values of the time delays: ?tAB =-17.4 ± 2.1, ?tAC =-18.9 ± 2.8 and ?tAD = 28.8 ± 0.7 days (B and C are leading, D is trailing). We propose to characterize two kinds of micro-lensing events: micro-lensing for the A, B, C components corresponds to typical variations of ~10-4 mag/d during all the seasons, while the D component shows an unusually strong micro-lensing effect with variations of up to ~10-3 mag/d during 2004 and 2005.PG 1115+08: we found new values of the time delays in this GLS: ?tBA = 4.4±3.2, ?tAC = 12.0±2.5 and ?tBC = 16.4±3.5 days and that A1+A2 lensed components of the system might have undergone microlensing.B1422+237: we were able to get light curves for A,B and C lensed components which show us both activity of the source-quasar and presence of microlensing.FBQ0951+2635, SBS1512+530: we obtained light curves that show small-amplitude intrinsic variations of the quasar on time scales of about 100 days (in SBS1520+530). Variable magnitude di?erence between the images of the quasars shows the presence of microlensing variations in these systems.
The 3D map astro/geo tour with your fingertips
Akihiko, Tomita
I present the example of the practice of the fingertip virtual tour of prefecture-level living area map and discuss future development of this activity. Once a year, I visit the half-day indoor activity for visually impaired children of mostly primary school ages, organized by a nonprofit organization “Picture Books for Visually Impaired and Weak Eyesight Children,” Osaka, Japan. This presentation is the report of the activity in 2017. I made 15 cm x 15 cm 3D map with height emphasized by five, 250 km x 250 km Kansai area in Japan using numerical data by Geospatial Information Authority of Japan. Using this 3D map as the mold, plaster replica was prepared for each of all the participants including about a dozen visually impaired children and their brothers and sisters, parents, and staff. Though the 3D printer has become common, it is still expensive and not easy to handle. The plaster replica making is easy and quite inexpensive. The 3D printer work was made in the university, and the plaster work was made by parents and activity staff on site. The Kansai area shows many rows of the north-south direction mountain ridges parallel to each other. This means that a great compression force is acting in the east-west direction on the plate of this area. We can understand why we have so many earthquakes in this area. The participants understand that planetary geological mechanism contributes to maintaining the Earth environment. Children shouted, “Interesting!” and parents enjoyed understanding the nature of the planet. We already have numerical map data around the world. Children can learn about other countries through their fingertip trip, which can help connect children across the borders of countries and language. We also have numerical map data of other worlds in the solar system. Children regardless of the eyesight can share the “grand tour” of the solar system and can understand each world’s nature and history by reading scientifically the surface information.
Retention of Small Charged Dust in Planet Forming Disks
Akimkin, Vitaly
Dust evolution in disks around young stars is a key ingredient to the global disk evolution and accompanying planet formation. The mutual sticking of initially small grains is not straightforward and may be hampered by several processes. This includes dust grain bouncing, fragmentation, electrostatic repulsion and fast drift to the central star. In this study we aim at theoretical modeling of the dust coagulation coupled with the dust charging and disk ionization calculations. We show that the electrostatic barrier is a strong restraining factor to the dust coagulation in the micrometer size regime. While the sustained turbulence helps to overcome the electrostatic barrier, dust fluffiness limits its potential. Coulomb repulsion may keep a significant fraction of dust at 1-10um size range in vast regions of protoplanetary disks.
NOC activities at Syria
AlAssiry, Mohamad
The poster present the NOC activities at Syria
M1-92 revisited: the chemistry of an ejected common envelope
Alcolea, Javier
M1-92, Minkoswi's Footprint, is a 0.9 Mo pPN around a B-type post-AGB source. Previous IRAM Plateu de Bure 13CO 2-1 observations showed that this nebula is the result of a brief but huge mass-loss event that occurred 1200 yr ago. Using the IRAM 30m MRT, we have have conducted a very sensitive spectral line survey of M1-92, the observations almost fully covering the 3mm, 2mm, and 1.3mm bands. We have detected, for the first time in this source, numerous molecular species such as HCN, HNC. CN. CS, NS, SiO, SO, SO2, H2S, including the cations HCO+, N2H+, and SO+. These species include tracers of PDR chemistry and of shock chemistry, indicating that both processes are presently active in the source. More recently, some of the detected lines have been observed with sub-arc-second resolution, using the IRAM NOEMA 9-element array. Combining single dish and (old and new) interferometric data, we have determined the abundance of the most relevant species in the different parts of the pPN. Most relevant, C17O and C18O observations suggest a very shocking result: the derived [17O]/[18O] ratio indicates that, according to standard nucleo-synthesis models, the initial mass of the central star was 1.8 Mo. This is in agreement with the high mass of the nebula, but in contrast with the relatively low [12C]/[13C] ratio and the O-rich chemistry of the source. We suggest that all these results can be reconciled if we assume that the copious mass loss event occurred 1200 yr ago, which resulted in the formation of the present nebula, was also responsible for the premature ending of the AGB phase of the star. This would have prevented the 3rd dredge-up to occur, and so the source would have escaped from its transformation into a carbon rich source. If this hypothesis this is correct, and depending on the prevalence of such events, we may have to revise our knowledge on stellar yields from AGB stars.
Primordial Mass and Density Segregation in a Young Molecular Cloud
Alfaro, Emilio J.
We analyse the geometry of the Pipe Nebula, drawn by the distribution (Q-spatial parameter) and hierarchy (spatial segregation) of column density peaks previously detected and catalogued. By analysing the mass and volume density of the cores, we determine that both variables shown to be spatially segregated and highly structured. Given the early evolutionary state of the Pipe Nebula, our results suggest that both, mass and volume density segregations, may be primordial, in the sense of appearing in the early phases of the chain of physical mechanisms which conform the star-formation process. We also propose that volume density, and not mass, is the pararameter that most clearly determines the initial spatial distribution of the pre-stellar cores.
Statistics of the relative orientation between magnetic fields in clumps and filaments
Alina, Dana
Star formation seems to be more efficient inside filamentary structures of molecular clouds. The role that the magnetic field plays in this process can be revealed using polarimetric data. We have performed a statistical analysis of the relative orientation between the plane-of-sky magnetic field and the filaments associated with the Galactic Cold Clumps - the very cold condensations of ISM that could host regions of star formation. We have separated polarization parameters components of the filaments and their background using thin optical medium assumption, and the filaments have been detected in the Planck data using the Rolling Hough Transform algorithm. Alignment properties depend on the density of the filaments but also on the density of the filaments’ environment. We find both parallel and perpendicular alignment between the matter structures and the magnetic field inside the Planck Cold Clumps situated in high density environments while there is mostly parallel alignment inside the filaments if the clumps contribution is omitted.
The formation of massive binaries as a result of the dynamical decay of trapezium systems
Allen, Christine
We study the dynamical evolution of 10 multiple systems of trapezium type with very massive components. As initial conditions we take the planar positions, transverse velocities, distances and masses from the best observations found in the literature. Radial velocities and z-positions are not available, but were modeled by Monte Carlo simulations. Our results show that the dynamical lifetimes for these systems are extremely short, shorter than the evolutionary lifetimes of their massive components. Only assuming much larger masses for the components both lifetimes become comparable. These results are similar to the dynamical lifetimes we found previously for the minicluster associated with the B component of the Orion Trapezium and for the Orion Trapezium itself. The end result of the simulations is usually a close massive binary, sometimes a triple system.
The relevance of old measures for studies of the dynamical evolution of trapezium systems
Allen, Christine
Studies of the internal motions in multiple systems are necessary to understand their dynamical evolution. Carefully selected historical measures of the separations and position angles have proved to be important to construct dynamical evolution models of trapezium systems, because in spite of their relatively low accuracy, they provide a long time baseline. We have successfully used historical measures for such studies. We discuss as examples the dynamical evolution of the Orion Trapezium, and that of ten additional massive trapezia with sufficient historical data. We find extremely small dynamical lifetimes for all of these systems, comparable to those we found earlier for the minicluster associated with the B component of the Orion Trapezium.
FORTY-FOUR YEARS OF REVISTA MEXICANA DE ASTRONOMIA Y ASTROFISICA: ITS IMPACT ON THE LATIN AMERICAN ASTRONOMICAL COMMUNITY
Allen, Christine
After 44 years of continuously publishing the Revista Mexicana de Astronomía y Astrofísica, we cast a short retrospective view on its history emphasizing its regional impact.RMxAA was founded in 1974. The journal has published original research papers in all areas of astronomy, astrophysics and related fields. Until 1994 RMxAA also published the proceedings of astronomical conferences held in Mexico and Latin America. Since 1995 a Series devoted exclusively to such proceedings was founded, RMxAC, Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias.All papers submitted to RMxAA are strictly refereed. RMxAA is included in the most important international indexes. Both publications are fully integrated into the ADS. Their contents have always been freely available to the general public. This ensures a wide international visibility, comparable to that of the best astronomical journals.The impact factor of RMxAA has varied over the years, mostly as a consequence of small number statistics. The average impact factor is about 2.4, greater than that of all but a few Latin American scientific journals.The editorial independence of RMxAA, the fact that there are no page charges for authors, and that the printed version is distributed free of charge to astronomical libraries all over the world has contributed to the development of astronomy, especially in Latin America. The Conference Series has published the proceedings of IAU Latin American Regional Meetings (LARIM), as well as those of Astronomía Dinámica en Latino América (ADeLA) and other astronomical meetings in the region, thus stimulating regional astronomical development and collaboration.
Improving your research reproducibility with the Astrophysics Source Code Library
Allen, Alice
Astrophysics research relies on software and all robust science requires transparency and reproducibility, yet the computational methods used in our discipline are often not shared or are difficult to find. In recent preliminary research, 40% of the software used in the 2015 papers we examined did not offer source code and restricting the reproducibility of this research. The Astrophysics Source Code Library (ASCL. ascl.net) registers astrophysics research source codes that have been used in refereed research, benefiting the field in numerous ways, including increasing the discoverability of software and making the published research record more robust. With over 1,700 codes, the ASCL is the largest indexed resource for astronomy research codes in existence. This free online registry was established in 1999 and is indexed by ADS and Web of Science. ASCL registration allows your software to be cited on its own merits and provides a citation method that is trackable and accepted by all astronomy journals and journals such as Science and Nature. This presentation covers the benefits of registering astronomy research software with the ASCL, upcoming changes that will enable greater software discovery initially for NASA software and potentially for software funded by other organizations, changes to the ASCL and ADS that benefit researchers, and our research into software use in astronomy.
Revisiting the solar flux predicted by model photospheres
Allende Prieto, Carlos
One of the big successes of the theory of model atmospheres is the ability of models to approximately reproduce the observed disk-integrated solar flux from the near-UV to the mid-infrared. In this presentation I will present recent calculations to quantify how good this agreement is for state-of-the art theoretical models of the solar photosphere.
The cold gas reservoir feeding a distant interacting young radio galaxy
Allison, James
While some radio galaxies show stong emission lines in the optical, characteristic of an active galactic nucleus (AGN), others do not. We have substantial circumstantial evidence that this dichotomy is the result of the mode in which gas is accreted onto the nucleus. However, the exact mechanisms by which high and low excitation radio galaxies are nourished can only be determined through direct observation of the gas. A powerful method for measuring the kinematics of gas deep into the centres of radio-loud AGN is through detection of the HI 21-cm hyperfine and CO rotational lines in absorption. The Australian Square Kilometre Array Pathfinder (ASKAP), in its commissioning and early science phase, has been very successful in detecting HI absorption in powerful radio galaxies at intermediate cosmological redshifts. In followup observations using ALMA we have detected 12CO(2-1) absorption in PKSB1740-517, a young luminous radio galaxy at z=0.44 that has likely undergone a recent interaction with its companion galaxies. I will discuss the results of this work, including how we can disentangle the line-of-sight ambiguities from absorption and what we learn about the system by combining the ASKAP, ALMA and multiwavelength ancillary data.
Investigating Transient Events in Active Stars
Alvarado Gomez, Julian David
Stellar magnetic fields completely dominate the environment around late-type stars. They are responsible for driving the coronal high-energy radiation (e.g. EUV/X-rays), the development of stellar winds, and the generation of transient events such as flares and coronal mass ejections (CMEs). While considerable progress has been made for the first two processes, our understanding of the eruptive behavior of active stars is still very limited. This information is critical as these phenomena can have a strong or even catastrophic impact on planetary systems. This is of particular importance during the early stages of evolution where they can become the dominant factor in determining the physical properties around late-type stars. In this context, I will present the initial results of a joint observational and numerical project, aimed at studying the properties of eruptive phenomena in active stars. The first aspect comprises the analysis of simultaneous observations of X-ray and white light flares of young stars, acquired with the Chandra and Kepler (K2) telescopes. On the numerical side, I will present detailed 3D MHD simulations of CMEs in active stars, developed using one of the latest models employed for space weather forecasting in the solar system. These results will be discussed in the general solar-stellar context, taking into account the observed properties of the magnetic fields in which they develop.
Far Beyond the Sun: Mapping the Magnetic Cycle of the Young Solar-Analog iota Horologii
Alvarado Gomez, Julian David
A former member of the Hyades cluster, iota Horologii (? Hor) is a ~625 Myr old Sun-like star which displays the shortest coronal activity cycle known to date (PCYC ? 1.6 yr). Apart from the Sun, this X-ray activity cycle is also the only one identified on a single star so far. The link between the activity cycles and the characteristics of the surface magnetic field is a fundamental piece of information to understand the origin of stellar magnetism in late-type stars. Here we present the initial results of a long-term observing campaign aimed at studying the evolution of the magnetic cycle of ? Hor, using ground-based high-resolution spectropolarimetry. Using the technique of Zeeman Doppler Imaging (ZDI), we have successfully detected non-simultaneous large-scale polarity reversals associated with the azimuthal and the radial components of the magnetic field, over the course of the activity cycle of the star. Moreover, using state-of-the-art 3D Magneto-Hydrodynamics (MHD) simulations, each recovered ZDI radial field map help us to self-consistently model the coronal structure, stellar wind, and astrospheric conditions around the star. These models will be compared with simultaneous X-ray monitoring of the corona using XMM-Newton (AO-16), and with stellar wind diagnostics from HST (Cycles 25 & 26).
Galactic context to local star formation: the local neighborhood in the Gaia era
Alves, Joao
Gaia will revolutionize our view of the local galactic neighborhood not only for the precise measurements of its stellar content but also for the exquisite 3D view of the local ISM. In this contribution, I will focus on the interplay between local massive stars and molecular cloud complexes (d < 500 pc) where resolved star formation can be studied, from dense core formation to circumstellar disk dissipation. We will start by describing the newly discovered Blue Streams, their validation from ground-based spectroscopic data and Gaia data, and how these streams are impacting the structure of both the diffuse and dense star-forming ISM. We will present Herschel maps of the nearby complexes and show evidence that stellar feedback from the streams plays a fundamental role not only in assembling but also shaping filaments and cores, as well as driving most of the observed turbulence. We will argue that the Blue Streams, because of their massive star content proximity to Earth, can have an impact on life on the planet. I will end by pointing to a large NIR survey of the local complexes carried out in Vienna (VISIONS visions.univie.ac.at) that together with Gaia data will allow for the first 3D space motion map of the local star-forming ISM, opening a new window on ISM dynamics.
The detailed chemical abundance pattern of the metal-rich Galactic globular cluster NGC 6366
Alves-Brito, Alan
Globular cluster (GC) stars have been known to display chemical inhomogeneities (multiple populations) in their light elements (Li, CNO, Na, Al, Mg and F). While this chemical pattern is likely primordial, there is no consensus about the nature of the polluters, with intermediate-mass Asymptotic Giant Branch (AGB) stars, fast rotating massive stars, massive interacting binaries and supermassive stars being some of the candidates. In this work, we present chemical abundances for a sample of eight red giants in the metal-rich GC NGC 6366, which has been little studied in the literature. We have used high quality data (R > 40,000; S/N > 60) obtained at the VLT (8.2 m) and CFHT (3.6 m) telescopes. The abundances for light and heavy elements were obtained through equivalent widths and spectrum synthesis of individual atomic lines, using the MOOG stellar line analysis program, together with 1D Kurucz’s stellar atmosphere models. The derived abundances were compared with those obtained for stars in different environments (field and GCs). Our outcomes suggest that NGC 6366 is a monometallic GC ([Fe/H] = -0.60 ± 0.03), presenting a very short extension in its Na-O anticorrelation. After taking literature’s results into account, the Na-O diagram shows a barely detectable, if any, Na-O anticorrelation. Also, there is no evidence of Mg-Al anticorrelation and no star-to-star variation in Al in our sample. Abundance ratios of heavier elements, as Ba and Eu, as well as the similarities between the [Eu/Fe] and [a/Fe] ratios, lead us to believe that the primordial composition of NGC 6366 is dominated by objects with short time-scale, likely Type II SNe, with mild contribution of AGBs. None of the elements measured present star-to-star variation greater than the uncertainties, which means that NGC 6366 is chemically homogeneous.
Explorers of the Universe: university and school creating new pathways.
Alves-Brito, Alan
The project “Explorers of the Universe: university and school creating new pathways" is an Outreach Program (popularization and scientific communication) from the Department of Astronomy of the Institute of Physics at the Federal University of Rio Grande do Sul, in Porto Alegre, Brazil. Launched in 2012, the project has an interdisciplinary, interinstitutional and interprofessional character. The goals are twofold: (i) to promote the training of Physics undergraduate students, especially future teachers of the Brazilian basic education system and (ii) to contribute to the scientific literacy of school students of Porto Alegre and its Metropolitan Region. The program is focused on young people living in regions of high social and economic vulnerability. It intends to improve the quality of education and to articulate the school-university dialogue by proposing new educational public policies. Workshops and activities promoted by the Program aim to integrate the outreach actions to the teaching and basic research programmes at the University, where undergraduate students have the opportunity of creating and executing thematic workshops. The Program encourages undergraduate students to: practice creative thinking through science; develop the passion for the dark-sky observing; and develop scientific argumentation alongside different agents (teachers, school managers, pedagogues, social workers) in formal and non-formal learning environments.
Astronomy for Development in Brazil: education and the intersection of gender, race, ethnicity and class in STEM.
Alves-Brito, Alan
Brazil is Latin America’s largest country in area and one of the most populous countries in the world, with approximately 210 million people. It is also a former Portuguese colony, displaying a highly diverse population that includes indigenous, descendants of African slaves and European settlers. Brazil accounts for approximately 90% of the world’s population who speaks Portuguese. For more than 350 years, the country was the focus of a strong Atlantic slave trade, importing more enslaved Africa people than any other country and being the last country in the Western world to abolish the slavery system. South America’s most influential country, Brazil presents a strong economic power. However, throughout its history, Brazil has been a country with a high level of inequality. Over the past few years it has made major strides in its efforts to raise millions out of poverty, but the gap between rich and poor remains high. In this work, I will discuss how Astronomy, which is a multidisciplinary field, can fascinate people of different ages and cultures, occupying a prominent place among the basic sciences to guarantee global development in the 21st century. I will show and discuss how some of our projects in Brazil, focused on Educational Astronomy, are changing the reality in this country by promoting the intersection of gender, race, ethnicity and class in STEM (science, technology, engineering, and math) fields.
Analysis and Design of a Prototype Low Frequency Radio Telescope
Aminaei, Amin
Radio astronomy is generally linked to the massive giant dishes while an important part of discoveries and breakthrough sciences is actually achieved by small low-frequency radio telescopes. At the selected frequency band, tens of MHz, the structure of antenna is light-weight and the physical size of the antenna is in the order of meters. Also, the analog and digital modules are commercially available and data processing can be done at low cost. Using a commercial digital board and compact analog module including an optimized antenna, analysis and design of a prototype low-frequency radio telescope is proposed. The radio telescope consists of a co-centered orthogonal antenna with extendable arms being capable of basic radio interferometry. It can be used as a stand-alone station where basic radio astronomy and atmospheric observations are feasible. Atmospheric phenomena such as scintillation and monitoring Sun and giant planets would be typical case studies. It can be also used as an ad-hoc element of a large-based array of the radio interferometrs at the same frequency band for fundamental astronomy observations. * Please also consider the presentation for Focus Meetings: FM15, Astronomy for Development whichever is more relevant
An update on the progress of the SKA band 5 feed system
Aminaei, Amin
In accordance with the global effort for the development of the Square Kilometer Array (SKA) dish prototype, we report on the current status of the SKA band 5 Single Pixel Feed (SPF) system. The SKA band 5 is initially designed for the frequencies of 4.8-15.3 GHz and it’s been proposed to expand the upper limit to 25 GHz and higher which suits the study of the planet formation and exobiology. The performance of critical components of the prototype SPF is currently being validated. A prototype of the cryostat has been manufactured and the cryogenic system is being tested. It should maintain the temperature at the level of 20 K while connected to the heat load of the horn feeds. Also, we address the corresponding RF chain measurements, EMI testing, and progress on the development of a digital Feedback Package Controller (FPC) for SPF band 5 system.-On behalf of the SKA Oxford Team
Deep high-resolution imaging of the field around nearby stars of the Ursa Major moving group
Ammler-von Eiff, Matthias
Results from a search for low-mass companions in the vicinity of 20 nearby Ursa Major group members are reported. The Ursa Major open cluster is the nucleus of this group and coincides with the Big Dipper constellation. Other members are spread over the entire sky and share a common space motion. The selected targets of high proper motion pass the background field quickly so that any comoving companion could be identified easily. The targets are also nearby and young so that low-mass companions would be bright in the near-infrared and separated well from the stellar image. The observations were taken with NAOS-CONICA at the ESO VLT in the Ks band using a semi-transparent coronagraph. The consolidated results of this survey have been published recently.The survey achieved a brightness contrast of typically 13-15 mag and was sensitive to objects as faint as 20 mag at separations between a few arcseconds and up to 25 arcseconds from the star. This is as close as several astronomical units for the nearby eps Eri and up to 600 au and more for the most distant targets. More than 200 faint background sources were identified. We will discuss the observations in the light of similar ground-based direct imaging campaigns and other recent studies of the UMa group.High-resolution imaging is not only a key technique to detect giant planets in wide orbits around nearby stars but is also essential for the follow-up of transit candidates from missions like TESS and PLATO. These monitor wide fields at low spatial resolution so that additional observations are needed to distinguish contaminating sources close to the actual targets. Even though NAOS-CONICA has already been decommissioned, the results presented are considered relevant to the ground-based follow-up of TESS and PLATO targets as those will be bright, potentially nearby, and may display significant proper motion.
Flybys versus Mergers: Contributions to the Spin-Orbit Alignment of Dark Matter Halo Pairs
An, Sung-Ho
Recent observations reveal that the spin of a galaxy is often aligned with the orbital angular momentum of its companion. Using cosmological N-body simulations, we investigate the relative contributions of the merger and flyby to the spin-orbit alignment of galaxy pairs. We examine a sample of dark-matter halo pairs with the similar masses to the Milky Way (11.6 < Log Mhalo/Msun < 12.4), the mass ratios from 1:1 to 1:3 (major interactions), and the separations smaller than a sum of their virial radii (R12 < R1,vir + R2,vir). The result shows that the dark-matter halo has its spin preferentially aligned with its companion’s orbital angular momentum (i.e., the prograde interaction), corroborating previous studies. We find that while both the merger and flyby interactions lead to the increase in the angular momentum of galaxies, mergers make a greater contribution than flybys, leaving stronger spin-orbit alignment (fprograde = 0.75) than flybys (fprograde = 0.60).
Metallicity Mapping of the Milky Way with Large Photometric Surveys
An, Deokkeun
We present a metallicity map of the Milky Way Galaxy within 10 kpc from the Sun, based on extensive sets of ugriz photometry from the Sloan Digital Sky Survey (SDSS), the Southern Galactic Cap u-band Sky Survey (SCUSS), and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). We obtain metallicities for individual stars by applying a set of stellar isochrones, which have been calibrated against observations of main-sequence stars in clusters and tested using spectroscopic data. Our metallicity scale has been further checked using Gaia priors for relatively nearby stars. Our metallicity map has a continuous spatial coverage and thus is less susceptible to sampling bias, and can be used as an independent check on results from recent spectroscopic survey data. Combining with proper motion measurements from Gaia, our metallicity estimates reveal a long tail of stars with retrograde rotation in the Galactic halo. These stars exhibit systematically lower metallicities than those in prograde rotation, consistent with previous findings based on smaller photometric data samples.
Sub-galactic regions on the galaxy-wide scaling relations: the example of the ULX-rich galaxies NGC 3310 and NGC 2276
Anastasopoulou, Konstantina
We present results from Chandra observations of the X-ray starburst galaxies NGC 3310 and NGC 2276. We detect 30 discrete sources with luminosities above 2.0x1038 erg/s in NGC 3310, and 19 discrete sources with luminosities above 1.0x1038 erg/s in NGC 2276. The majority of the sources have photon indices of 1.7-2.0, typical for X-ray binaries. Both galaxies have large numbers of ultra-luminous X-ray sources (ULXs): 14 for NGC 3310 concentrated on the circumnuclear star-forming ring and north spiral arm, and 11 for NGC 2276 with the brighter ones on the west side of the galaxy which is compressed due to harassment by the intra-group medium it is moving into. We find for both galaxies that the ULX-hosting areas show excess X-ray luminosity with respect to the general scaling relations between X-ray binary luminosity, SFR, and stellar mass. On the other hand, other regions of the galaxies either agree or fall below these scaling relations. This indicates that sub-galactic regions do not necessarily follow the galaxy-wide scaling relations. The significant deviation from the average galaxy-wide scaling relation can be attributed to either age or metallicity variations between sub-galactic regions, with the former being more likely. Such differences in age could be the origin of the scatter we observe in the low SFR regime of the LX-SFR scaling relations.
Carbon Enrichment in the Early Universe
Andersen, Johannes
Carbon-enhanced extremely metal-poor (CEMP) stars are our richest source of information on carbon (C) in the early universe. CEMP stars are of two basic varieties, with or without enrichment of elements synthesized by the slow neutron-capture process – CEMP-s and CEMP-no stars; each is associated with the inner and outer (most metal-poor; [Fe/H] < -3.5) halo populations, respectively. Canonically, CEMP stars were considered to be the result of local binary mass transfer, and much effort was invested in models according in this paradigm. However, Hansen et al. (2016a,b) showed that only ~80% of the CEMP-s stars are binaries, the CEMP-no stars and ~20% of the CEMP-s stars were single. Thus, C in these stars has been synthesised in a different object and implanted across interstellar space in the natal clouds of today’s CEMP stars, and both fast-rotating primordial stars and ‘faint’ supernovae have been invoked as possible progenitors. In a recent review, however, Höfner & Olofsson (2018) discuss whether combined radiation and pulsation pressures could eject C dust from a single star, obviating the need for a binary companion. Spectroscopic log g-s are uncertain for CEMP stars, so there is doubt if they are ‘normal’ giants or AGB stars. Gaia DR2 should yield actual log L values to tell, and the photometry should have sufficient precision and time coverage to confirm or refute the reality of the 3-400-day pulsations suggested by earlier radial-velocity work.
Binary Population Synthesis with Markov-chain Monte Carlo
Andrews, Jeff
Nowhere is our understanding of binary evolution challenged more than in the formation of the merging double neutron stars (DNS) recently detected by gravitational wave observatories. Yet, exactly because these systems are so sensitive to binary evolution physics, they have the most potential to constrain theory. These constraints are traditionally placed using binary population synthesis, a method that, despite its potential, has difficulty generating sufficient statistics because merging DNSs are exceedingly rare; only a small fraction of simulated systems evolve into binaries similar to those observed. I will introduce a fundamentally new approach to studying stellar binary populations that employs a Markov-chain Monte Carlo algorithm to efficiently explore the binary evolution parameter space. In addition to being substantially more efficient than traditional methods for studying high mass binaries, this technique seamlessly incorporates observational constraints and their corresponding uncertainties. As a test case, I apply this method to model the population of high mass X-ray binaries in the Large Magellanic Clouds. Finally, using this approach I will demonstrate what we can learn about the formation and evolution of the merging compact objects detected by LIGO.
RAMSES II - Raman Search for Extragalactic Symbiotic Stars
Angeloni, Rodolfo
Symbiotic stars (SySt) are long-period interacting binaries composed of a hot compact star - generally a white dwarf (WD) - an evolved giant star, and a tangled network of gas and dust nebulae. SySts represent unique laboratories for studying several astrophysical phenomena and their reciprocal influence. They are also among the most promising candidates as progenitors of SNIa.Presently, we know 252 SySt in the Milky Way and 62 in external galaxies. However, these numbers are still in striking contrast with the predicted population of SySt in our Galaxy that, according to different estimates, may oscillate between 10^3 and a few 10^5. The actual SySt population is thus a key issue that needs further investigating.One of the reasons for this embarrassing discrepancy between SySt population synthesis models and observations also stems from the fact that the SySt group has been historically defined on the basis of purely spectroscopic criteria. Because of many other stellar sources mimicking SySt colors, no photometric diagnostic diagram has so far demonstrated the ability to unambiguously identify a SySt, thus making the recourse to costly spectroscopic follow-up still inescapable.The two intense Raman OVI bands at 6830Å and 7088Å, however, are so unique to the symbiotic phenomenon that their presence is considered a sufficient criterion for classifying a star as symbiotic, even when the donor star is not directly visible through optical spectroscopy. In this poster we present the early results from RAMSES II (Raman Search for Extragalactic Symbiotic Stars), a Gemini/GMOS Upgrade Project funded by AURA, which makes use of the Raman OVI 6830Å band as a powerful photometric tool to identify new SySt within and beyond the Galaxy.
Youth Engagement with Astronomy
Anjos, Sara
Science communication research has raised multiple questions about the interaction between science and the public. Some concern the production of scientific knowledge in context, whereas others are related to how knowledge is transposed, transferable and rebuilt, depending on individual and social needs and experiences, and on the representations of science each individual or public group has, to mention just a few.Clarifying these and other questions that have arisen in the Science-Technology-Society (STS) field is without any doubt important, as science (and its applications) occupies a crucial place in society and in the way people live and understand the world.One of the recurring themes is how the public understands and engages with science, based on science literacy studies and their implications in the promotion of public participation in Science and Technology (S&T) decisions. Constructivist research has problematized science and processes of knowledge production by examining how people experience science in their lives and how scientific achievements are embodied in social relations. On the basis of such reasoning, alternative forms of problematizing science literacy have emerged.This research falls within that approach, by carrying out a study to evaluate Science Communication and Informal Science Education activities, focusing on the astronomy field. Particularly for the youngest, one of the aspects highlighted in the discussion about the relationship with science is fundamentally implicated on the design of a common social future, which implicates choices as consumers, the aspiration to academic and professional careers and participation on public life, as citizens.
Orientation of the spins of thin galaxies
Antipova, Aleksandra
We present a preliminary analysis of the orientation of the spins of edge-on galaxies relative to the elements of the large-scale structure of the universe, such as groups, clusters and filaments of galaxies. In this work, we use the Revised Flat Galaxy Catalog, compiled by Karachentsev I.D. et al. (1999). This catalog contains 4236 flat galaxies with an axes ratio greater than 7. This allows us to identify galaxies of late types (Sc, Sd) visible from the edge. For edge-on galaxies, we can determine the orientation of the spin with high accuracy. Currently at the 6-meter Russian Telescope (BTA - Big Telescope Alt-azimuth) we study the rotation curves of 160 superthin edge-on galaxies. The program is fulfilled on 70%. From these data we determine the angular momentum and examine the orientation of the spins of galaxies relative to the surrounding structures.
Thermal conductivity of porous dust aggregates
Arakawa, Sota
The thermal conductivity of dust aggregates is a key parameter in planetary science, including thermal evolution of minor planets and comets. However, the porosity dependence of thermal conductivity for highly porous aggregates is not yet thoroughly understood.We numerically investigated the thermal conductivity of fluffy dust aggregates. In our calculation, we used the snapshot data of N-body simulations of static compression in the periodic boundary condition and determined the temperature structure and heat flux of the porous dust aggregates.We derived an empirical formula for the solid thermal conductivity as a function of the filling factor of dust aggregates. The results reveal that the solid thermal conductivity is approximately proportional to the square of the filling factor. For the case of dust aggregates with the filling factor in the range of 0.1-0.5, our results are well consistent with the experimental data. Moreover, we also found that the solid thermal conductivity is significantly lower than previously assumed for highly porous aggregates whose filling factor is lower than 0.1. In light of these findings, we will reexamine the thermal histories of small planetary bodies.
Astronomy in Serbia and Serbia in the International Astronomical Union
Arbutina, Bojan
We briefly discuss the history of membership and the current position of Serbia inside the International Astronomical Union. We give an overview of astronomy education, research and public outreach in Serbia. Some statistics is presented concerning the number and gender of BSc, MSc and PhD students that graduated/obtained their degree in astronomy/astrophysics from the Department of Astronomy, Faculty of Mathematics, University of Belgrade. Due attention is paid to the most important scientific/educational institutions in Serbia in which the majority of astronomers are employed as well as various research topics investigated.
Mildly Super-Eddington mode of X-ray pulsars
Arefiev, Vadim
We consider observational appearances of several X-ray pulsars and discuss possible application to the modern models of X-ray emission generation in accreting pulsars with strong magnetic field. In particular we consider the arising limitations on properties of accretion column, based on found results.
Oxygen abundance gradients in nearby galaxies and the performance of strong-line methods
Arellano-Córdova, Karla Ziboney
We study the abundance gradients implied by the direct, temperature-based, method and several strong-line methods using optical spectra obtained by different authors for H II regions in the galaxies M31, M33, M81, M101, and NGC 300. We find that the direct method and the P method introduce large dispersions around the gradient, of 0.11-0.25 dex, whereas the ONS, C, O3N2, and N2 methods lead to lower dispersions, in the range 0.06-0.11 dex. The differences in dispersion can be explained by considering the sensitivity of each method to line ratios such as [O II] 3727/Hbeta and [N II] (6548 + 6584)/5755, which are susceptible to observational problems. In those galaxies that have better determinations of the oxygen abundance gradient with the direct method, the C method provides gradients that are more consistent with the ones based on this method. We explore further the performance of strong-line methods using a sample of 168 spectra of H II regions with measurements of two temperatures, Te[N II] and T[O III], compiled from the literature. We confirm that the C method provides better estimates of the oxygen abundance, with differences with respect to the direct method that are lower than 0.2 dex for most of the objects in the sample. The other strong-line methods introduce larger differences and a dependence of these differences on the degree of ionization. Finally, we analyze the temperature structure of our sample of H II regions and derive a new set of temperature relations between Te[N II] and T[O III], which can be used whenever one of these temperatures is not measured.
TolTEC: a large-format polarimetric millimeter imaging camera for the 50m Large Millimeter
Aretxaga, Itziar
TolTEC a large-format (~7000 detector) imaging polarimeter in construction for the 50m Large Millimeter Telescope, is the result of a consortium of 7 institutions in the USA, Mexico and the UK. TolTEC will provide the capability to conduct surveys at 1.1, 1.4 and 2.1mm and detect point-like and extended sources in large areas ranging to hundreds of square degrees to unprecendented depths. Here we present a review of the construction status and plans to conduct four legacy surveys, starting in 2019: The Clouds-to-Cores Legacy Survey that explores the collapse of giant molecular clouds into star-forming cores ; The Fields in Filaments Legacy Survey is designed to probe the distribution of magnetic fields in filaments as traced by the polarization of dust; The Ultra-Deep Survey of Star-forming Galaxies is a confusion-limited survey which ties the entire Luminous Infrared Galaxy population from redshifts 2 to 10 directly to their optical counterparts; and The Large Scale Structure Survey probes the relationships between the spatial distribution of star forming galaxies and large scale structure and provides a detailed view of clusters and their substructure via the Sunyaev-Zeldovich (SZ) effect.
Observing in the past thanks to the Gaia astrometric reference star catalogue
Arlot, Jean-Eudes
The arrival of the Gaia astrometric reference star catalogue is not only a giant step in the astrometric accuracy allowing to measure new unknown small motions of solar system objects but also to observe in the past with today accuracy. In fact, accurate astrometry is performed since about one century after the use of photographic plates. The measures made at the time of the old observations used old reference catalogues, the accuracy of which being between 500 mas and one arcsec. We will show how we are making new measures and new reductions of photographic plates thanks to the Gaia reference catalogue allowing to provide valuable data and pre-discoveries of recently observed objects.
The ephemerides and astrometric database for natural planetary satellites
ARLOT, Jean-Eudes
The former working group “Motions and observations of the planetary satellites” fulfilled its tasks and all astrometric observations together with several ephemerides are now provided to the astronomical community. However, some problems are not solved: the databases of observations are in different format contrarily to the asteroid database which adopted a standard format. In spite of the different sources of types of observations, it will be useful to choose a standard format (linked with VO) in order to make easier the research for improving the dynamical models and ephemerides. A discussion should be made in Division A and Commission X2 Ephemerides to decide on standards to be applied in the future.
Understanding internal structure of planetary satellites through astrometry
ARLOT, Jean-Eudes
The internal structure of the natural planetary satellites have an influence on the motion of these objects. Careful observations may lead to constraints on this structure. However, in spite of the high accuracy of recent space probe observations, the observations are not made on a sufficient interval of time to put into evidence the effects due to the internal structure. These effects are cumulative and we need long period observations. In order to solve that problem, we digitized old photographic plates and reduced them with the Gaia reference star catalogue providing old data with today accuracy. This method is very promising for the understanding of the formation, evolution and structure of the natural planetary satellites.
Sloshing in its cD halo: MUSE kinematics of the central galaxy NGC 3311 in the Hydra I cluster
Arnaboldi, Magda
We aim to identify the main structural components of the Hydra I cD galaxy NGC 3311 to investigate the connection between the central galaxy and the surrounding stellar halo. We produce maps of the line-of-sight velocity distribution (LOSVD) moments from a mosaic of MUSE pointings covering NGC 3311 out to 25 kpc. Combining deep photometric and spectroscopic data, we model the LOSVD maps using a finite mixture distribution, including four non-concentric components that are nearly isothermal spheroids, with different line-of-sight systemic velocities V, velocity dispersions σ, and small (constant) values of the higher order Gauss-Hermite moments h3 and h4._x005F The kinemetry analysis indicates that NGC 3311 is classified as a slow rotator, although the galaxy shows a line-of-sight velocity gradient along the photometric major axis. The comparison of the correlations between h3 and h4 with V/σ with simulated galaxies indicates that NGC 3311 assembled mainly through dry mergers. The σ profile rises to ≃ 400 km s-1 at 20 kpc, a significant fraction (0.55) of the Hydra I cluster velocity dispersion, indicating that stars there were stripped from progenitors orbiting in the cluster core. The finite mixture distribution modeling supports three inner components related to the central galaxy and a fourth component with large effective radius (51 kpc) and velocity dispersion (327 km s-1) consistent with a cD envelope. We find that the cD envelope is offset from the center of NGC 3311 both spatially (8.6 kpc) and in velocity (ΔV = 204 km s-1), but coincides with the cluster core X-ray isophotes and the mean velocity of core galaxies. Also, the envelope contributes to the broad wings of the LOSVD measured by large h4 values within 10 kpc. We conclude that the cD envelope of NGC 3311 is dynamically associated with the cluster core, which in Hydra I is in addition displaced from the cluster center, presumably due to a recent subcluster merger.
Observational Properties of Miras in the KELT Survey
Arnold, Robert
We present a catalog of the observed properties of Mira variable stars detected with the KELT survey. Asymptotic giant branch (AGB) stars were identified in KELT using their 2MASS and WISE colors, and their variability properties were determined from KELT data. Of the 21279 KELT AGB objects, over 700 Mira variables were identified. Here we present their observed periods, luminosities, and temperatures that will place important constraints on future theoretical work on the effect convection has on pulsation periods and stability.
PERTURBING EFFECTS OF CORIOLIS AND CENTRIFUGAL FORCES IN THE RESTRICTED FOUR-BODY PROBLEM WITH ALL OBLATE PRIMARIES
Arora, Monika
The present paper explores the e ect of the perturbations of Coriolis and Centrifugal forces in the restricted four-body problem when all the primaries are oblate in the Lagrange equilateral triangle con guration. We have numerically investigated the number of libration points, viz. the in-plane and out of plane and investigated their stability. Zero velocity curves have also been drawn and the regions of motion have been explored for various values of the Jacobi constant. Newton Raphson basins of attraction have also been drawn and investigated.
The role of metallicity in high mass X-ray binaries
Artale, Maria Celeste
In the last decade, different observational and theoretical studies indicate that the number and X-ray luminosity of high mass X-ray binaries (HMXBs) are directly correlated with stellar metallicity. Previous work claims that metal-poor progenitors are more likely to produce brighter HMXBs. In this work, we test this correlation with metallicity by using population synthesis models and exploring the mechanisms that may produce this dependence. We also investigate the HMXBs population in galaxies by implementing the results from population synthesis models into the galaxy catalogs from state-of-the-art galaxy formation models.
The chemical fingerprint of Class I sources
Artur de la Villarmois, Eizabeth
The formation and evolution of protoplanetary disks are a fundamental ingredient in the process oflow mass star formation. In particular, Class I sources act as a ‘bridge’ between the deeplyembedded Class 0 sources and the emergence of protoplanetary disks, associated with Class IIsources. Thus, the study of Class I sources are of prime importance for our understanding of theformation and evolution of solar-type stars and their disks.In this work, we present an ALMA chemical survey of 10 Class I sources in Ophiuchus. Thecovered molecular transitions were chosen specifically to trace the kinematics of disk formation(i.e., C17O, H13CO+ and C34S) and the warm chemistry in the inner envelope or disk (i.e., SO2and CH3OH). The tracers reveal the chemistry and physics of the embedded disks, probing materialwith high temperatures and densities. In spite of a very high sensitivity, CH3OH is not detectedtoward any of these sources. This suggests that CH3OH gas only exists in a very thin layer betweenbeing frozen out as ice and photo-dissociated by UV radiation from the star. Furthermore, we findthat SO2 shows compact emission and the intensity correlates with the luminosity of the sources.Therefore, SO2 may be a better tracer of the warm gas and its associated chemistry in these sources.These observations show the existence of disk-like structures, associated with most of the sourcesof the sample, and highlight the differences in the physical structures between Class I sources andother stages of low-mass star formation.
A Study of Inner Disk Gas around Young Stars in the Lupus Complex
Arulanantham, Nicole
We present a study of molecular hydrogen at the surfaces of the disks around five young stars in the Lupus complex: RY Lupi, RU Lupi, MY Lupi, Sz 68, and TYC 7851. Each system was observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST), and we detect a population of fluorescent H2 in all five sources. The temperatures required for LyA fluorescence to proceed (T ~ 1500-2500 K) place the gas within ~15 AU of the central stars. We have used these features to extract the radial distribution of H2 in the inner disk, where planet formation may already be taking place. The objects presented here have very different outer disk morphologies, as seen by ALMA via 890 micron dust continuum emission, ranging from full disks with no signs of cavities to systems with large regions that are clearly depleted (e.g. TYC 7851, with a cavity extending to 75 and 60 AU in dust and gas, respectively). Our results are interpreted in conjunction with sub-mm data from the five systems in an effort to piece together a more complete picture of the overall disk structure. We have previously applied this multi-wavelength approach to RY Lupi, including 4.7 micron IR-CO emission in our analysis. These IR-CO and UV-H2 observations were combined with 10 micron silicate emission, the 890 micron dust continuum, and 1.3 mm CO observations from the literature to infer a gapped structure in the inner disk. This single system has served as a testing ground for the larger Lupus complex sample, which we compare here to examine any trends between the outer disk morphology and inner disk gas distributions.
Investigating Multiple Stellar Populations and Rotation in intermediate-age LMC star clusters
Asad, Randa
The extended main sequance turn off (eMSTO) has been observed in many intermediate-age star clusters. It's origin is still debatable, it could be due to multiple stellar popuations (MSP) or stelar rotation or other factors. We use a new approach to investigate the MSP scenario, as well as rotation in star clustes by means of integrated spectra. Our results are consistent with the results obtained from CMD studies. Our presentation will give details on each of the clusters studies and compare it with the CMD literature result.
Estimation of Magnetic Reconnection Rates and its association with Flare and CME’s
Ashish, Patel
We estimate the magnetic reconnection rates for 50 flares with flare class in the range of B to X based on GOES classification of solar flares observed with Solar Dynamics Observatory (SDO) during a period of 2011 to 2012. Parameters of reconnection namely inflow velocities, outflow velocities and the magnetic reconnection rates have been estimated. In order to calculate the inflow velocities, we analyzed flux measurements from HMI instrument onboard SDO which enables us to derive the dimensional reconnection rate. The outflow velocities are estimated using CME data which is available on the SOHO LASCO CME Catalogue (https://cdaw.gsfc.nasa.gov/CME_list/). Further, the ratio of the inflow and outflow velocities enables us to estimate the non-dimensional magnetic reconnection rate. We obtain the reconnection rates of the order of 10-2 to 10-4 from our observations. We have also attempted to establish a relation between the magnetic reconnection rate and the intensity class (GOES) of the flares.
Modelling Coronal Mass Ejections' propagation in the inner heliosphere: a case study using forecasting model EUHFORIA
Asvestari, Eleanna
Coronal Mass ejections (CME) are one of the principal contributors to space weather, and are potential hazard to human life and activity in space and on ground. They have thus been the focal point of forecasting models aiming to accurately predict their arrival time at target, as well as their magnetic field configuration, which in the case of Earth-directed CME determines their geoeffectiveness. EUHFORIA is a data-driven magnetohydrodynamic model tracing the evolution of CME and CME-driven shocks through realistic background solar wind conditions. Its advantage over other similar models is that it employs a magnetic flux rope concept to model Interplanetary CME (ICME). To assess this new aspect of EUHFORIA two case-studies of well observed CME are being analysed and the modelled results are being compared to observations. The selection criterion for the two cases is that the CME is encountered by at least two well-separated spacecraft and exhibits flux rope signatures at both. One of the selected CME was encounter by Venus Express and STEREO-A, which were radially aligned at the time of the CME passage. The secont CME analysed was encountered by MESSENGER and WIND, which were longitudinally separated by 30 degrees. The choice of candidates will allow us to comprehensively evaluate the accuracy and utility of the employed flux rope modelling approach, not only in terms of radial evolution of the CME but also in modelling different parts of the propagating structure.
Optical properties of the black hole:shadow
Atamurotov, Farruh
The shape of the silhouette (shadow) can be used to test the corresponding theory of gravity for describing physical processes in the vicinity of a supermassive black hole. We have investigated how the size and apparent shape of the black hole is distorted due to the black hole’s parameters by analyzing unstable circular orbits, i.e.,. We adopted two observables, the radius Rs and the distortion parameter δs, characterizing the apparent shape; we found that the shape of the shadow is affected by the value of the rotation parameter and so on. The motion of photons around axially symmetric rotating black hole were considered with different parameters of the black hole.
Tracing the gas, dust and ice evolution in planetary systems with SPICA
Audard, Marc
SPICA, an infrared space mission operating in the mid and far-infrared has recently been selected for further study in the frame of ESA’s M5 call. SPICA will carry SAFARI, an infrared spectrometer operating from 34 to 230 µm (R˜300-11000), POL, an imaging polarimeter at 100, 200, and 350 µm, and SMI that will provide imaging spectroscopy with R˜100 and full-band slit-fed spectroscopy at R˜100-2,000 from 17 to 36µm, and R˜28,000 from 12 to 18µm. The SPICA telescope will be cooled down to about 8K, effectively suppressing most of the satellite's infrared thermal background, which will allow us to reach down to very low fluxes. SPICA will provide spectroscopic capabilities at a high sensitivity of 2-15 x1e-20 W/m2 (5s/1hr), about two orders of magnitude deeper than Herschel. One of the core science topics addressed by SPICA is "Tracing the gas, dust and ice evolution in planetary systems”. We present this topic to demonstrate the capabilities of SPICA.
Probing the gas fuelling and outflows in nearby AGN with ALMA
Audibert, Anelise
Feeding and feedback in active galactic nuclei (AGN) play a very important role to gain a proper understanding of galaxy formation and evolution. The interaction between activity mechanisms in the nucleus and their influence in the host galaxy are crucial for the feedback and gas fuelling of the black hole (BH). Winds and outflows produced by the AGN can eject or heat the gas, terminate the star formation and through the lack of fuel for accretion, quench the black hole activity. Recent discoveries of massive molecular outflows have been promoting the idea that winds may be major actors in sweeping the gas out of galaxies, in agreement with theoretical predictions of AGN-driven winds models. AGN are fuelled by accretion of material onto the SMBH and the gas component can form stars on its way to the central engine. By studying the molecular gas in galaxy disks we want to understand: (i) how the star formation and nuclear activity are fuelled and what are the timescales involved, since both process rely on a common cold gas supply, but in different timescales? (ii) what are the mechanisms driving gas from the disk towards the nucleus, removing its large angular momentum and forming large non-axisymmetric perturbations?Our goal is to probe these phenomena by probing the gas inside the central kpc in nearby AGN. This has recently been possible due to the unique ALMA spatial resolution and sensitivity. We present a study of the morphology and kinematics of the cold dense gas in a sample of 5 nearby Seyfert/LINER nuclei at the unprecedented spatial resolution of 0.06-0.09” (3-10 pc), part of a new ALMA follow-up of the NUGA (NUclei of GAlaxies) program. NUGA is a high-resolution (0.5-1”) CO survey of 25 low luminosity AGN performed with the IRAM PdBI that has revealed smoking gun evidence of gas funnelling into the nucleus in 1/3rd of the sample, suggesting that galaxies may be alternating periods of fuelling and starvation.
Ecliptic-poles Stellar Survey (EclipSS)
Ayres, Thomas
The Ecliptic-poles Stellar Survey (EclipSS) currently is collecting far-ultraviolet spectra (115-143 nm), with HST's ultra-sensitive Cosmic Origins Spectrograph (COS), of a sample of 49 F2-K2 dwarf stars in the North and South ecliptic polar regions, to further advance studies of magnetic activity among cool Main sequence stars similar to the Sun. The ecliptic poles are favored places for several current and up-coming astronomical survey satellites, including Gaia (astrometry), TESS (exoplanets and asteroseismology), and eROSITA (coronal X-rays). These instruments scan along lines of ecliptic longitude, and thus accumulate their deepest exposures close to the ecliptic poles. The EclipSS targets were selected to be bright enough for eROSITA, not too bright for TESS, and just right for COS. The combined photometric (starspots), asteroseismic, FUV, and X-ray measurements will provide wholistic information concerning rotation periods, sizes, masses, metallicities, ages, activity levels, and coronal properties to inform community-wide efforts to explore stellar activity and its underlying magnetic engine, the Dynamo.
Searching for extended circumgalactic halos around galaxies
Azanha, Luiz
A full understanding of the galactic halo physical properties is an important missing piece in the picture of galaxy formation and evolution. The circumgalactic halo of a galaxy is important given that it may represent the reservoir of gas for future star formation. Radio observations of spiral galaxies using the 21cm-line of hydrogen show that galaxies have typically extended disks of neutral hydrogen which show a sharp edge. Beyond this point the galaxy may be dominated by ionized gas. This ionization may be caused either by the ultraviolet radiation from the galaxy itself or by ultraviolet background radiation. Detecting a hydrogen ionized halo gives us information about the total baryonic mass in galaxies and also about galaxy evolution. This detection is also a valuable as an indirect probe of the UVB radiation, which carries information about the cumulative history of star formation and AGN activity. This project is part of S-PLUS, a photometric survey of the southern hemisphere, which uses 12 bands, 5 SDSS broad and 7 narrow bands, designed to study stars and nearby galaxies. One of the filters covers Ha, which is the emission line related to recombination in ionized hydrogen. We will stack images of nearby galaxies using this sample, separating by morphology and stellar masses. A careful continuum subtraction will be necessary, using one or more broad band images. We expect to detect Ha emission from the halo, which is a direct detection of an ionized hydrogen gas. We will present our partial results.
Gaia DR1 Evidence of Disrupting the Perseus Arm
Baba, Junichi
We have discovered a clear sign of the disruption phase of the Perseus arm in the Milky Way using Cepheid variables, taking advantage of the accurately measured distances of Cepheids and the proper motions from Gaia Data Release 1. Both the Galactocentric radial and rotation velocities of 77 Cepheids within 1.5 kpc of the Perseus arm are correlated with their distances from the locus of the Perseus arm, as the trailing side is rotating faster and moving inward compared to the leading side. We also found a negative vertex deviation for the Cepheids on the trailing side, -27°.6, in contrast to the positive vertex deviation in the solar neighborhood. This is, to our knowledge, the first direct evidence that the vertex deviation around the Perseus arm is affected by the spiral arm. We compared these observational trends with our N-body/hydrodynamics simulations based on a static density- wave spiral scenario and with those based on a transient dynamic spiral scenario. Although our comparisons are limited to qualitative trends, they strongly favor the conclusion that the Perseus arm is in the disruption phase of a transient arm.
AGN torus properties investigated by the 4.7 micron CO absorption band
Baba, Shunsuke
In the active galactic nucleus (AGN) unified scheme, the central engine is supposed to be surrounded by a toroidal dusty material, so-called AGN torus, which is responsible for the obscuration of the radiation from the nucleus. The unified scheme of AGNs requires verification of the existence of AGN torus and investigation of its nature possibly linked with the surrounding environment. However, the small physical scale of the torus prevents us from direct spatially-resolved observations of it applicable for a large sample of AGNs. Instead, spectroscopy of near-infrared absorption lines can, with thermal radiation from a compact region heated by the nucleus as the background continuum, effectively resolve the foreground material and examine its physical states. On the basis of this approach, we observed the 4.7 micron CO absorption band (v=1<-0, DeltaJ=+/-1) in nearby (z<0.07) 47 infrared galaxies with the AKARI satellite. Many of the sample galaxies showed large column densities (N_H~10^23 cm-2) and high temperatures (several x 100 K) through the CO band profile. Such a large column of warm gas is difficult to be attained via UV and shock heating and probably heated by X-ray from an AGN. The distribution of the gas column density against the 14-micron luminosity used as an indicator of the AGN luminosity was qualitatively consistent with the obscured fraction determined in X-ray observations. This consistency supports the assumption that the CO absorption likely probes the region dominated by X-ray. We also found that AGN-starburst composites showed on average larger column densities than Seyfert 2s. This result suggests that the obscuration by an AGN torus is also effective in a composite and that the torus is geometrically thicker than that in a typical Seyfert. This difference may reflect the AGN-starburst connection that supernovae in a circum-nuclear disk assist the formation of a thick torus.
Seeking for magnetic fields in rotating disks/jets around young stars
Bacciotti, Francesca
We have started a project with ALMA for a combined study of rotation and magnetic properties in disks and jets around low mass young stars. _x005F The motivation is to test the models of magneto-centrifugal launch of jets along the magnetic field lines that thread the disk. This mechanism is relevant for star formation, as the associated magnetic braking of the disk allows the extration of angular momentum from teh system and the accretion of disk material onto the central star._x005F Our plan is to use the polarimetric capabilities of ALMA to determine the magnetic configuration _x005F in systems with rotating jets and disks. In these cases, in fact, we expect to find strong ordered magnetization in the first ten of AU from the source._x005F We have recently obtained ALMA Band 7 polarimetric data for the young systems DG Tau and CW Tau, two T Tauri stars for which the rotation properties of jet and disk are well known. _x005F The analysis of these data reveals, however, that dust self-scattering concurs strongly with the magnetic configuration to the determination of the polarization patterns._x005F We present here the first results of the project, illustrating the different interpretations. Even in the case in which magnetic alignement is weak, the polarization configuration can be a powerful tool for the diagnostics of the dust properties in disks.
A conception of proto-sun disk with high angular momentum evolution
Bagrov, Alexander V.
The Standard Planetary Cosmogony describes the evolution of protoplanetary nebula that remained near the young Sun. Its specific angular momentum j must be less than rotation stability limit for a single star with mass M¤: j ≤ 1.7·1017(M/M¤)2/3 cm2·s-1. On the other hand, minimal angular momentum required for the creation of a double star is 10 times more. When the specific angular momentum of the protostellar nebula is slightly less than j ≤ 1.7·1018(M/M¤)2/3 cm2·s-1, rotation of the nebula will stop its accretion to the center before the gathered mass will be enough to become a star. In this case, the protostellar nebula turns into a flat rotating disc. Dust particles in the disc will play a role of an effective refrigerator, so all material of the disc has to be cold. Gases in the disc will stop turbulence, so all particles will be on circular Keplerian orbits. All particles will have nearly exact Keplerian velocities with negligible differences produced by temperature. This will lead to a diffusion shift of low-speed particles to the center of the protostellar disc. So the mass of the central part of the disc will be steadily increasing without acquiring angular momentum. Eventually, the concentrated mass will be enough for producing a star, and the opacity of the central gaseous globe will lead to the heating of its inner part, which is necessary for the nuclear synthesis. Hence a star in the center of a fast rotating disk will have long rotation period.
Interstellar striders as migrating bodies through planetary systems
Bagrov, Alexander V.
In 2011 at least 10 “free-floating planets” with roughly the mass of Jupiter were detected with gravitational microlensing. October 19, 2017, using the Pan-STARRS1 telescope in Hawaii astronomers discovered a small “interstellar strider” named ‘Oumuamua that crossed our Solar system luckily near to the Earth to be detected by survey telescope. Taking in account sensitivity of the telescope, visible velocity of the discovered object and a volume of space, where it was detected, the researchers supposed that such an interstellar body can penetrate into an inner part of the Solar system each year._x005F There are many reasons to believe that in the interstellar space may exist bodies much larger than ‘Oumuamua, though they will occur rarer. This assumption automatically will lead to a simple idea, that some of the interstellar striders can collide with bodies of our planetary system. If interstellar striders are “primordial” planetezimales lost by extrasolar planetary systems, they are ordinary comet nuclei that consist of frozen volatiles and dust. When they hit, say, the Earth, they can produce large flat collision craters (“astroblems”). All volatiles from the hitter will totally evaporate, and dust particles from comet nucleus will be the same as the dust of Earth soil. So no footprints of interstellar origin of hazardous hitter will be preserved. If 10-km sized interstellar strides are 100 times less rare than 1-km ‘Oumuamua, the probability of their direct collision with the Earth will be about 1 event in 100000 years. It may be only coincidence, but the time between the appearance of huge astroblems on the Earth surface is about 100000 years too. Hence we may suppose that interstellar striders play their own role in the evolution of the Solar planetary system.
Outlying H-alpha blobs in SDSS IV MaNGA
Bait, Omkar
We have discovered a population of 28 outlying H-alpha emitters which appear as unresolved blobs in the SDSS IV MaNGA integral field unit (IFU) survey. These could be candidate dwarf galaxies with high specific star formation rates (sSFRs). We have used the recently released stellar population and ionized gas emission maps, derived using the Pipe3D pipeline, to visually identify H alpha emitting regions with no underlying optical continuum emission in deep imaging from the DECam Legacy Survey or Beijing-Arizona Sky Survey. Moreover, these H-alpha blobs have velocities which are different from the velocity map of the host galaxies. Starting from a sample of $\sim 2700$ MaNGA galaxies in the Data Release 14, we identify 28 outlying H-alpha emitting blobs. We make apertures around these blobs and calculate the total fluxes around various emission lines to study their location on the Baldwin Philip and Terlevich (BPT) diagram, which shows that all of them are photoionised due to star formation. We also estimate their total star formation rates (SFR) and metallicities using the integrated emission lines. We use the non-detections in the optical continuum as an upper limit on the absolute magnitude in the B band ($M_B$) of these candidate dwarf galaxies and compare them with the well known $M_B$-SFR and $M_B$-metallicity relations. We found that these galaxies have very high sSFRs compared to the local volume dwarfs. Some of the dwarf galaxies could belong to the faint end of the blue compact dwarfs (BCDs), blue diffuse dwarfs (BDDs), or tidal dwarf galaxy (TDGs) populations. However, the metallicites of these dwarfs galaxies shows that they are either consistent with or have lower metallicities than the standard $M_B-metallicity$ relation. Hence, we can at least rule out the possibility of them being TDGs.
On the interdependence of galaxy morphology, star formation, and environment in massive galaxies in the nearby Universe
Bait, Omkar
Using multi-wavelength data, from UV-optical-near-mid IR, for $\sim$6000 galaxies in the local Universe, we study the dependence of star formation on the morphological T-types for massive galaxies ($\log M_*/M_\odot \geq 10$). We find that, early-type spirals (Sa-Sbc) and S0s predominate in the green valley, which is a transition zone between the star forming and quenched regions. Within the early-type spirals, as we move from Sa to Sbc spirals the fraction of green valley and quenched galaxies decreases, indicating the important role of the bulge in the quenching of galaxies. The fraction of early-type spirals decreases as we enter the green valley from the blue cloud, which coincides with the increase in the fraction of S0s. This points towards the morphological transformation of early-type spiral galaxies into S0s which can happen due to environmental effects such as ram-pressure stripping, galaxy harassment, or tidal interactions. We also find a second population of S0s which are actively star-forming and are present in all environments. Since morphological T-type, specific star formation rate (sSFR), and environmental density are all correlated with each other, we compute the partial correlation coefficient for each pair of parameters while keeping the third parameter as a control variable. We find that morphology most strongly correlates with sSFR, independent of the environment, while the other two correlations (morphology-density and sSFR-environment) are weaker. Thus, we conclude that, for massive galaxies in the local Universe, the physical processes that shape their morphology are also the ones that determine their star-forming state.
Extended H-alpha emitters in the outskirts of galaxies in SDSS IV MaNGA
Bait, Omkar
We have discovered a sample of 13 extended H-alpha emitters (xHAEs) which lie away from the optical disc of host galaxy in the SDSS IV MaNGA integral field unit (IFU) survey. We have used the recently released stellar population and ionized gas emission maps, derived using the Pipe3D pipeline, to visually identify H-alpha emitting regions away from the host galaxy and having no underlying optical continuum emission in deep imaging from the DECam Legacy Survey or Beijing-Arizona Sky Survey. Starting from a sample of $\sim 2700$ MaNGA galaxies in the SDSS Data Release 14, we identify 13 outlying xHAEs. We make apertures around these xHAEs and calculate the total fluxes around various emission lines to study their location on the Baldwin Philip and Terlevich (BPT) diagram, which shows that they are photoionised due to an active galactic nuclei (AGN) or a mixture of both an AGN and star formation. We argue that these xHAEs are Hanny's Voorwerp like objects. In particular, we argue that they are fainter counterparts of the Voorwerp, since unlike the Hanny's Voorwerp which have such strong emission line flux that they were discovered in the broad band continuum imaging, our xHAEs do not have any bright optical counterpart.
The reconfinement of AGN jets
Bamford, Thomas
The relativistic jets associated with active galactic nuclei (AGN) are capable of propagation over multiple length scales, extending up to a few billion initial jet radii. This remarkable stability can be understood in terms of the interaction of the jet with its surrounding environment. In particular, jet expansion associated with a decreasing external pressure can lead to causal disconnectivity across the jet, suppressing global instabilities. In at least some AGN jets, the external pressure eventually drives a reconfinement shock into the jet axis establishing causality across the jet once more. Past this reconfinement point the jet is therefore subject to global instabilities and will eventually become fully disrupted and turbulent. In 1997 Komissarov and Falle proposed a semi-analytic model predicting the position of the reconfinement point. This model is explored in more detail for different atmospheres. Strong deviations are found for steeply declining power law atmospheres, with the model significantly underestimating the reconfinement scale.
A comparison of planetary embryos collision outcome in binary and single star systems : perfect merging versus a more realistic model.
Bancelin, David
By now, observations of exoplanets have found nearly 90 binary star systems hosting 125 planets. We expect these numbers to increase as 50 – 70 % of the main sequence stars in the solar neighbourhood are members of binary or multiple systems. The planetary motion in binary star systems depends strongly on both the parameters of the stellar system (i.e. stellar separation and eccentricity) and the architecture of the planetary system (i.e. number of planets and their orbital behaviour). In case a terrestrial planet moves in the so-called habitable zone (HZ) of its host star, the habitability of such a planet depends on further requirements among which the amount of liquid water on its surface is certainly a crucial factor.Models of planetary formation either in single or binary star systems favour a merging approach to estimate the outcome of collisions occurring between Moon-to-Mars-sized embryos during the early stage of planetary formation. As a consequence, the size and water content of the body resulting from a collision are systematically overestimated because of the assumption of perfect merging.In our study, we simulate collisions of same-sized embryos (either Moon or Mars size) initially placed in the region between 0.9 and 1.1 au which are perturbed by a giant planet of Jupiter mass and a secondary star. In these simulations, we derive statistics for the impact velocities and angles. Our results show that in comparison with a corresponding single star systems, the impact velocities are significantly higher in binary star systems in case the giant planet and the secondary star induce a secular resonance in the studied area.Combining our results with more realistic collisions simulations using a GPU 3D-SPH (Smooth-Particles Hydrodynamics) code, we find for both single and binary regimes, a significant loss of water and material especially at low impact velocities when the impact angle is less than 45°.
SEARCH FOR EXOPLANETS AROUND NORTHERN CIRCUMPOLAR STARS: HD 18438 and HD 158996
Bang, Tae-Yang
We have conducted Search for Exoplanet around Northern circumpolar Stars (SENS program since 2010 over seven years using the high-resolution Bohyunsan Observatory Echelle Spectrograph (BOES) at the 1.8m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We have accumulating precise radial velocity (RV) measurements for 224 target stars, and so far found seven exoplanets and more potential exoplanet candidates. As exemplary cases, we report the analyses on HD 18438 and HD 15899. Both show long-period RV variations, 719 days for HD 18438 and 820.2 days for HD 158996. We checked the chromospheric activities using Ca ii H and H_ lines, HIPPARCOS photometry and line bisectors to identify the origin of the observed RV variations. In the case of HD 18438, we conclude that the observed RV variations with period 719.0 days are likely to be caused by the pulsations because the periods of HIPPARCOS photometric and H_ EW variations for HD 18438 are similar to that of RV variations in Lomb-Scargle periodogram, and there are no correlations between bisectors and RV measurements. In the case of HD 158996, on the other hand, we did not find any similarity in the respective periodograms nor any correlation between RV variations and line bisector variations. In addition, the probability that the real rotational period can be as longer than the RV period for HD 158996 is only about 4.3%. Thus we conclude that observed RV variations with a period of 820.2 days of HD 158996 are caused by a planetary companion, which has the minimum mass of 14.0 MJup, the semi-major axis of 2.1 AU, and eccentricity of 0.13 assuming the stellar mass of 1.8 MSun. HD 158996 is so far one of the brightest and largest stars to harbor an exoplanet candidate.* BTY is supported by BK21 Plus of National Research Foundation of Korea.
Intermediate-Mass Black Hole Feedback in Dwarf Galaxies: a View from Cosmological Simulations
Barai, Paramita
Black holes are usually observed to be of stellar-mass or supermassive. By natural extension, there should be a population of Intermediate-Mass Black Holes (IMBHs: with mass between 100 to 106 Msun) in the Universe; which has started to been observed. An exciting claim has been made recently by Silk, J.(2017, ApJ, 839, L13): that there can be IMBHs at the centers of essentially all old Dwarf Galaxies. Early feedback by IMBHs in gas-rich dwarf galaxies at z = 5 - 8, can potentially solve multiple dwarf galaxy problems (e.g. core-cusp, number) within the Lambda-cold-dark-matter cosmology.We are performing Cosmological Hydrodynamical Simulations to test the case for IMBHs in Dwarf Galaxies. Our simulations employ the 3D TreePM SPH code GADGET-3, and include metal cooling, star formation, chemical enrichment, supernova feedback, AGN accretion and feedback (Barai, P. et al. 2016, MNRAS, 461, 1548). We are simulating small (2 Mpc)3 cosmological volumes with periodic boundary conditions, starting from z = 100. Black Holes of mass 1000 Msun are seeded inside halos when they reach a mass of 107 Msun. The black holes grow by accretion of gas from their surroundings and by merger with other black holes, and consequently eject feedback energy. We analyze the simulation output in post-processing to study the growth of the first IMBHs. We quantify the impact of IMBHs on their host Dwarf Galaxies; especially the effects on star formation in terms of negative or positive feedback.Our conclusions, based on numerical simulation results, support the phenomenological ideas made by Silk(2017). IMBHs at the centers of dwarf galaxies can be a strong source of feedback to quench star-formation and generate outflows. At the same time, these IMBHs form the missing link between stellar-mass and supermassive BHs.
Particle Acceleration, Turbulence and Multi-Wavelength Radiation in Blazar Jets
Baring, Matthew
Jets in blazars are an excellent forum for studying acceleration at relativistic MHD shocks, since this process is likely to spawn the highly-variable emission seen across the electromagnetic spectrum from radio to gamma-rays. Our recent work on combining multi-wavelength leptonic emission models with complete simulated distributions from shock acceleration theory has resulted in new insights into plasma conditions in blazar jets, likely to apply to radio galaxies as well. This has demonstrated the ability to infer the plasma density, and suggested the interpretation that turbulence levels decline with remoteness from jet shocks, with a significant role for non-gyroresonant diffusion. In this paper, we extend this program to a two-zone time-evolving construction, modeling together both extended, enhanced emission states from larger radiative regions, and prompt flare events in select Fermi-LAT and TeV blazars. A prime goal is to ascertain whether such flares are truly associated with prompt shock acceleration activity in relatively confined regions. The results illustrate how parametric degeneracies in shock acceleration conditions can lead to refined determinations of the plasma density and particle diffusion character in blazar jets.
Discovery of two new hot Jupiters: WASP-163 b and WASP-170 b
Barkaoui, Khalid
We present two new hot Jupiters, WASP-163 b and WASP-170 b, discovered by the WASP-South survey [Pollacco et al. 2006]. We performed a combined analysis of radial velocity data obtained with the CORALIE spectrograph mounted on the 1.2 m Euler-Swiss telescope [D. Queloz et al. 2001] and follow-up transit observations with the TRAPPIST-North [M. Gillon et al. 2017], TRAPPIST-South [M. Gillet et al. 2011; E. Jehin et al. 2011], NITES [McCormac et al. 2014] and Euler telescopes, to determinate the system parameters (K. Barkaoui et al. in prep). WASP-163 b and WASP-170 b are slightly larger than Jupiter while being about twice more massive, and are in short orbits (<3 days) around bright (V<13) solar-type stars. The radii of WASP-163b and WASP-170b are well reproduced by classical models of irradiated giant planets [J. J. Fortney et al. 2017]. This discovery made use of a new 60 cm robotic telescope, TRAPPIST-North, installed in spring 2016 at Oukaimeden Observatory in Morocco. It is an instrumental project led by the University of Liege (Belgium), in collaboration with the Cadi Ayyad University of Marrakech (Morocco), that is, like its southern twin TRAPPIST-South, totally dedicated to the observations of exoplanet transits and small bodies of the solar system.
MHD turbulence, self-gravity and radiative cooling effects on star formation regions
Barreto M. dos Santos, Lucas
In spite of being the focus of intense investigation for several decades, the comprehension on how star formation (SF) occurs is still a great challenge. In our galaxy, it is well known that stars are formed in dense regions within giant molecular clouds. The total internal pressure (thermal plus magnetic) in the clouds is, in general, large enough to prevent its gravitational collapse and an external agent, like turbulence driven by supernova shocks, spiral waves or stellar winds may be necessary to provoke the formation of high density, supersonic regions that may in turn collapse to form stars or an entire group of them. In this work we present three-dimensional MHD simulations of star formation regions considering the effects of radiative cooling and self-gravity in the overall process of ISM turbulence evolution and clouds collapse. Several models involving different regimes of super to sub-Alfvenic turbulence have been considered. In general lines, the results reveal the formation of elongated filaments with a few star-forming cores mainly at the confluence of the filaments, resembling, e.g., the recently observed features of the ISM by Hershel and CCAT at mm wavelengths. A detailed statistical analysis aiming at the characterization of several observable quantities, like the probability density function (PDF), the core mass function (CMF), the density power spectrum, and the overall magnetic field orientation in the filaments as a function of their size and scales will be also presented. In particular, we find that at large scale, more diffuse regions, the overall magnetic field orientation is parallel to the filaments while at smaller, denser regions, where self-gravity confinement prevails, the magnetic fields are in general perpendicular to the filaments, in consistency with observations. Finally, we will present direct comparisons of the simulations with selected regions of Hershel, CCAT and PLANCK foreground.
Direct Calibration of Gaia Photometry for White Dwarf Stars on the HST Flux Scale
Barstow, Martin
Gaia photometry is calibrated with respect to a large ensemble of stars of many differing spectral types. We have used a large sample of pure hydrogen DA white dwarfs, with well-defined temperatures and gravities, to compute synthetic photometry for these stars using the Gaia DR2 band passes. By comparing observed and synthetic Gaia G, BP and RP photometry it is possible to define zero points and magnitude off sets that link Gaia magnitudes with the HST photometric scale.
PROPERTIES OF HEAVY TRANSURANIUM ELEMENTS BY R-PROCESS NUCLEOSYNTHESIS DURING EXPLOSION OF SUPERNOVA TYPE II : A THEORETICAL PERSPECTIVE
BARUAH, RULEE
Nuclear astrophysics has come up as a very important topic in recent times due to the report of many new super heavy and ultra heavy elements formed in laboratories. Here we discuss a model for production of heavy elements along the rapid neutron capture (r-process) path during explosion of supernova type II. For most of the heavy and superheavy elements produced here, the experimental information is largely scarce. So a theoretical approach is considered essential for gathering information on the nuclei produced in such environments. _x005F Stars in the mass range 10-30 M⊙ evolve to form iron cores of 1.3 to 1.6 M⊙. These iron cores collapse according to well known instabilities, photodisintegration and electron capture. During collapse an outward bound shock wave forms in the matter falling onto the nearly stationary core. The conditions behind the shock at 100 to 200 km are suitable for neutrino heating . This neutrino heating blows a hot bubble above the protoneutron star and is the most important source of energy for Supernova Explosion. The most interesting evolution occurs as temperature falls from 1010 K to 109 K. Another astrophysical parameter needed for our analysis is neutron number density which we take to be greater than 1020 cm-3 . Along the path , the experimental data of observed elements matches our calculated one . It produced heavy neutron-rich nuclei with A > 240. Unlike high densities, at low density of 1020 cm-3 and T9 = 2.0 , the path contains all the elements as observed. Heavy transuranium elements (Z = 93-95) and their beta decay rates are obtained at densities >1020 cm-3 and are found to be in agreement with the experimental values of Audi et al (2003). It is found that the beta decay rates are much higher than the corresponding electron capture rates at the same classical condition. the_x005F Key words : R-process, nucleosysthesis, supernova, beta decay
OBSERVATION OF SOLAR ACTIVE REGION 12403
Batmunkh, Batbayar
In some works it was shown that, sudden disappearances of filaments have correlations with the phenomenon of coronal mass ejections. Also, some filament generates a low-power flare. Thus, it can be seen from many studies that filament plays an important role in the mechanism of occurrence of flares of some types. In this paper H-alpha observations of the solar active region (NOAA 12403), obtained at the coronograph of the astronomical observatory "Khurel togoot" of Mongolia, are presented. The filament in AO12403 after some time its appearance and length changed, that is, the intensity or its brightness decreased, and more accurately, some part of this filament became almost invisible. After that almost in its place there was a flare, moreover, it was very stable, and its glow lasted for a long time intensive. It can be seen that in this case the eruption of the filament and the appearance of the flare have a direct relationship with each other and, possibly, a magnetic field has been restructured.
On the formation of black holes in High-mass X-ray Binaries
Batta, Aldo
High-mass X-ray binaries (HMXRBs), such as Cygnus X-1, host some of the most rapidly spinning black holes (BHs) known to date. However, spin measurements from LIGO events produced by the mergers of binary black hole systems with masses ranging from 7 to 36 solar masses have low effective spins, consistent with low spin values. Assuming that the BH spin comes from the direct collapse of the star, we study the evolution of BH properties (mass and spin) as it accretes shells of infalling material from 1D stellar profiles with different rotation. When feedback from the formation of an accretion disk around the BH is included, the integrated feedback is large enough to unbind the collapsing star. If this energy is efficiently deposited into the infalling layers the collapse of the star will be halted, yielding BHs less massive and with a smaller spin that the one expected from the entire collapse of the star.
Magnetic fields at the epoch of reionization
Battaner, Eduardo
We detected magnetic fields with strengths of the order of 10-8 G at the epoch of Reionization. These were identified by using CMB data to obtain Faraday Rotation at both, the map and the spectrum level. The multipole region of about l<12 and the lack of correlations with either, galactic emissions (Faraday rotation, synchrotron and dust) or with CMB anisotropies and lensing, support our identification.
A THEORY AND SIMULATION-BASED CONVECTIVE BOUNDARY MIXING MODEL FOR AGB STAR EVOLUTION AND NUCLEOSYNTHESIS
Battino, Umberto
The s-process nucleosynthesis in Asymptotic Giant Branch (AGB) stars depends on the modelling of convective boundaries. I present models and s-process simulations that adopt a treatment of convective boundaries based on the results of hydrodynamic simulations and on the theory of mixing due to gravity waves in the vicinity of convective boundaries, where Hydrodynamics simulations suggest the presence of Convective Boundary Mixing (CBM). In this work I apply a CBM model purely motivated by simulations and theory, with no finetuning by hand "a priori" to match observations, to 1D stellar evolution models with initial mass M = 2 and M = 3 solar masses , and with initial metal content around the solar value. This mixing is affecting the Ne22(gamma,n)Mg25 activation and the s-process efficiency in the C13-pocket. The theoretical results are in good agreement with observations: at the end of the AGB evolution, we obtain an s-process production 0.36<[s/Fe]<0.78 and -0.23<[hs/ls]<0.45, which is consistent with spectroscopic observations of C-rich AGB stars.
A Coordinated Approach for Planetary Science with Astrophysics Assets
Bauer, James
Planetary Science has benefited greatly from observational platforms whose highest priorities have not originally emcompassed the studies of bodies within our solar system. The first measurements of X-rays from giant planet aurorae and comets, the discovery of comet and asteroid dust trails, and the largest surveys of asteroid and comet diameters were the results of observations using assets originally intended for astrophysical studies. The great observatories: Hubble Space Telescope, Spitzer Space Telescope, and Chandra X-ray observatory, have done a comprehensive array of planetary science investigations, as well as other smaller missions (e.g. WISE, Kepler, SWIFT, etc). Additionally, future assets, such as JWST and LSST, will make further rich contributions and are considering moving target observations in their planning and operational phases. Findings by NASA planetary assessment groups in 2017 encouraged the further use of astrophysics assets by planetary scientists, and the formation and definition of the necessary capabilities for these platforms to support planetary science. To that end, the NASA Planetary Science Division has constituted a group to investigate and receive input as to the desired functionalities of future astrophysics assets, with the long-term idea of providing a list of these faculties to inform future missions during the early technical design phases. We will present the progress and preliminary findings from the activities of this group in its efforts to compile a uniform set of basic capabilities and to maximize the yield of Solar System science with future Astrophysics assets.
Refueled and shielded - the early evolution of Tidal Dwarf Galaxies
Baumschlager, Bernhard
We present, for the first time, numerical high-resolution simulations of young tidal dwarf galaxies (TDGs), including a self-consistent treatment of the tidal arm in which they are embedded. Thereby, we do not rely on idealised initial conditions, as the initial data of the presented simulation stem from a galaxy interaction simulation. We compare these embedded models with those ones ususally applied but isolated from the tidal arm. Here we demonstrate the importance of the tidal-arm gas reservoir on the evolution of TDGs as gas can be accreted and is available for subsequent conversion into stars. During the initial collapse of the initially Jeans unstable proto-TDG, with a duration of a few 100 Myr, the evolutions of the embedded and isolated TDGs are indistinguishable. Significant differences appear however after the collapse has halted and the further evolution is dominated by the ongoing accretion of material from the surroundings of the TDGs. The inclusion of the tidal arm in the simulation of TDGs results in roughly a doubling of the gas mass and gas fraction, an increase in stellar mass by a factor of 1.5 and a ~5 times higher star formation rate (SFR) compared to the isolated case.Such high SFR leads to compact young blue star-dominated dwarf galaxies (DGs) which will survive supernova feedback and lateron either dissolve from the mature galaxy as ilolated dwarf ellipticals or when keep bound probably develop to the type of faint compact DGs found as satellites around massive cluster galaxies.
Dynamical Effects of Detected Giant Planets on the Habitable Zone in Binary Star Systems
Bazso, Akos
We present a survey of binary star systems with detected circumstellar extrasolar planets. The sample includes stars with separations up to 500 au. The presence of a Jupiter-like giant planet gives rise to a variety of gravitational interactions. Such interactions include mean-motion resonances (MMR) as well as secular resonances (SR). Secular resonances often entail highly eccentric motion. We use a semi-analytical method to find the locations of SRs, which are basically determined by the orbital precession frequencies of the massive bodies. For the systems at hand we investigate three possible orbital configurations of the giant planet: it is located either (1) exterior to the habitable zone (HZ) like in the solar system, (2) interior to the HZ like in case of Hot Jupiters, or (3) right inside the HZ. From the perspective of additional habitable terrestrial planets the last configuration is unpleasant. For the first configuration we demonstrate that there is always an SR interior to the giant planet's orbit. Under certain circumstances – depending on the system's architecture – this SR might fall into the HZ and cause highly eccentric motion of terrestrial planets. If additional MMRs are active this could even lead to the ejection of the terrestrial planet from the system. The second configuration is more safe in terms of SR, but including general relativistic perturbations SRs are possible, too. Generally, giant planets exterior to the HZ are less favourable in binary star systems. The majority of planets in our sample belongs to the second configuration, though, so we predict a fair chance to observe additional terrestrial planets in the HZ.
Binary Star Systems with Circumstellar Habitable Zones Affected by Resonances
Bazso, Akos
Extrasolar planets have been detected in a vast diversity of orbital configurations. Among them, wide separation binary star systems with circumstellar extrasolar giant planets have been shown to successfully form terrestrial planets in the host star's habitable zone (HZ). We focus on binary star systems with stellar separations from 20 AU up to several hundreds of AU. In this study we demonstrate that under suitable circumstances secular resonances (SR) might fall into the HZ and cause highly eccentric motion of terrestrial planets. We analyse the circumstances for which an SR is present in the HZ, and show the dependence on various system orbital and physical parameters. By applying a combination of simple analytical models we determine the orbital precession frequency of the giant planet and relate it to the corresponding frequencies of test planets in the HZ. We focus on the spectral type of the host star for different HZ ranges, and treat the orbital distance and eccentricity of the secondary star (which are often poorly constrained from observations) as free parameters. Our study shows that for any given location of the giant planet there exist configurations in which an SR appears somewhere in the HZ. Even for relatively distant secondary stars the giant planet's precession frequency might push terrestrial planets in the HZ to become eccentric. In summary, in wide binary systems with a giant planet exterior to the HZ, secular perturbations can affect the HZ. These perturbations drive terrestrial planets to more eccentric orbits, which increases the insolation received by the planet and could lead to uninhabitable conditions on the planet.
Curating Space Museums via Intersectional Design
Bazzi, Wael
My research examines the reinvention of the modern space museum not as an accommodation of historical artefacts, but as a platform for intersecting creative, entrepreneurial, educational and cultural innovations and influences of the space sector under one roof. Thus, the focus of the space museum shifts towards highlighting the greater good afforded to society (and humanity) by the space complex’s capacity for embracing and shaping the future, as opposed to nostalgically ruminating the past. To successfully achieve this, the proposed museum would need to undergo bi-annual turnover or up-cycling of its exhibits to match recent discoveries made in the space science community, as well as mediums of dissemination such as VR. To curate meaningful content for such a museum requires the close collaboration of multidisciplinary scientists and humanists with an intimate understanding of developments in cosmological, physical and aerospace science, as well as current affairs. In designing such exhibits, a team of creative technologists capable of suggesting avant-gard mediums of expression and experimentation would be rotated on the curation board alongside their fellow educators and scientists.By employing intersectional and trans-disciplinary design in their curation process, space museums benefit from a range of innovative and cost-effective advantages that outshine conventional models of public outreach and curation.I hypothesise that this method of curation will shift the dialogue about the role of Space Science in everyday public life, precisely by engaging head on with other cultural institutions, and may well lead to other previously unexplored collaborations. Through interactive art and sensory stimulation technology, the space museum offers a framework for putting space scientists in the front-seat of science communication, cultural engagement, and public outreach.
Starburst Dwarfs: the Super Star Clusters Form at Filament Hubs
Beck, Sara
The ”starburst” in starburst dwarfs is usually in one or a few super star clusters. These young clusters include the most extreme star formation in the local Universe; they hold up to 106M? of stars younger than 5 Myr in a few pc3, and one such deeply embedded cluster can dominate the total luminosity of the galaxy. What triggers the starburst activity? In what environment do these clusters form? How do these intense concentrations of young OB stars interact with their embed- ding clouds? To answer these questions, we use ALMA, the SMA, the JVLAand TEXES (a high–resolution mid-infrared spectrometer) to observe molecules, ions and dust in nearby starburst dwarfs. Typical spatial and spectral resolution are ˜ 5 pc and ˜ 4 km/s . We find that the starforming clouds are hot and dusty, and appear as distinct filaments. In NGC 5253 the bright embedded cluster is accreting a massive filament, and in He 2-10 the young clusters have formed where several filaments meet in a ’hub’. In some galaxies we see ionized gas escaping from the embedded ionized nebulae in slow pressure-driven flows.
New results on the magnetic field in M31
Beck, Rainer
The magnetic field of M31 is very regular, preserving its direction along a ring-like structure in the disk. This is regarded as the first and best evidence so far for the action of a large-scale dynamo in spiral galaxies. The regular field leads to fast diffusion of cosmic rays and prevents the formation of a radio halo of detectable surface brightness. The magnetic field in the central region is inclined to the disk and of opposite direction, indication of a major merger event in the past. New Effelsberg surveys at 11.1, 6.2, and 3.6 cm allowed us to derive maps of synchrotron emission, magnetic field strengths, and Faraday rotation with improved resolution and accuracy. M31 became the cornerstone to investigate the nonthermal properties of spiral galaxies.
Seismic Probing of the first dredge-up event and tidal interactions in red-giant binaries
Beck, Paul
Binaries in spectroscopic systems provide a homogeneous set of stars. Differences between parameters, such as age or initial conditions, which otherwise would have strong impact on the stellar evolution and blur the comparison on a star-to-stars basis, can be neglected. In this poster, we present the comprehensive analysis of KIC9163796, constituted of two red giants of ~1.4±0.1Mo. The masses of the two components differ only by 1.5±0.5%. We show that both stars are located in the short-lived phase of the first dredge up on the red-giant branch, when the convective envelope reaches the deepest penetration into the star. While asteroseismology allows to characterise the primary component well, the large difference in lithium abundance between the two otherwise very similar components is used to test stellar evolutionary models. From a study of tidal interactions in the ensemble of red-giant binary systems, we conclude that the close resemblance of the surface rotation and orbital period is a coincidence and does not correspond to a sign of spin synchronisation. The comparison of the rotation period inferred from asteroseismology and surface rotation indicates that the convective envelope is rotating rigidly.Evidence for the detection of the power excess of the secondary component in the composite power spectrum is presented. Therefore, KIC9163796 is one of the prototypes of binary systems with two oscillating red-giant components. Such seismic systems, which offer many constraints, can be employed as benchmark object to be use to calibrate evolutionary models and stellar ages.Related papers:Beck, Kallinger, Pablovski, et al. 2018a, A&A 612, A22Beck, Mathis, Gallet, et al. 2018b, MNRAS, under revision
Tracking the distribution of small dust grains through UV photometry
Beitia-Antero, Leire
Small (sizes < 0.5 microns) dust grains and large molecules, such as Polycyclic Aromatic Hydrocarbons, are very sensitive to short wavelengths. In particular, the ultraviolet (UV) range is of special importance because it contains the strongest feature of the extinction curve at short wavelengths: the 2175A bump or UV-bump. Studying the relative fraction of small to large dust grains allows to detect the regions on which dust coagulation is taking place or small dust grains are being destructed. We have combined GALEX NUV photometry with 2MASS infrared extinction maps to study the global distribution of small dust grains in the Orion Molecular Cloud as well as in the nearby, in projection, Rosette cloud. Evidence of variations in the strength of the UV bump has been found in the densest regions and also in heavily irradiated areas.
Update to the Whole Heliosphere Interval (WHI) Solar Reference Spectrum
Béland, Stéphane
As part of the 2008 Whole Heliosphere Interval (WHI) efforts, a new Solar Irradiance Reference Spectra (SIRS,) near solar minimum, was determined from 0.1 nm to 2400 nm using a combination of satellite and sounding rocket observations. The WHI campaign covered the solar Carrington Rotation 2068 (20 March to 16 April 2008) and included a Quiet Sun period (10 - 16 April 2008).We are presenting an update to the SIRS using the latest version of the various data products used initially as well as a different time range for the Quiet Sun to reflect the observed period of Solar minimum.
Omega Centauri: HST internal kinematics
Bellini, Andrea
We look at the internal kinematics of the multiple stellar populations of the globular cluster ? Centauri in an external Hubble Space Telescope (HST) field located at about 3.5 half-light radii from the center of the cluster. Thanks to the over 15-yr long baseline and the exquisite astrometric precision of the HST cameras, well-measured stars in our proper-motion catalog have errors as low as ~10 µas yr-1, and the catalog itself extends to near the hydrogen-burning limit of the cluster. We show that second-generation (2G) stars are significantly more radially anisotropic than first-generation (1G) stars. The latter are instead consistent with an isotropic velocity distribution. In addition, 1G stars have excess systemic rotation in the plane of the sky with respect to 2G stars. We show that the six populations below the main-sequence (MS) knee identified are associated with the five main population groups recently isolated on the upper MS in the core of cluster. Furthermore, we find both 1G and 2G stars in the field to be far from being in energy equipartition, with ? 1G=-0.007+/- 0.026 for the former and ? 2G=0.074+/- 0.029 for the latter, where ? is defined so that the velocity dispersion s µ scales with stellar mass as s µ proportional to m-? . The kinematical differences reported here can help constrain the formation mechanisms for the multiple stellar populations in ? Centauri and other globular clusters.
Omega Centauri: Multiple Populations Galore
Bellini, Andrea
We take advantage of the exquisite quality of the Hubble Space Telescope to distill the main sequence of ? Cen into its constituent populations. To this end, we restrict ourselves to the five most useful filters: the magic “trio” of F275W, F336W, and F438W, along with F606W and F814W. We develop a strategy for identifying color systems where different populations stand out most distinctly, then we isolate those populations and examine them in other filters where their subpopulations also come to light. In this way, we have identified at least 15 subpopulations, each of which has a distinctive fiducial curve through our five-dimensional photometric space. We confirm the MSa to be split into two subcomponents, and find that both the bMS and the rMS are split into three subcomponents. Moreover, we have discovered two additional MS groups: the MSd (which has three subcomponents) shares similar properties with the bMS, and the MSe (which has four subcomponents) has properties more similar to those of the rMS. We examine the fiducial curves together and use synthetic spectra to infer relative heavy-element, light-element, and helium abundances for the populations. Our findings show that the stellar populations and star formation history of ? Cen are even more complex than inferred previously.
Photometry of high-albedo outer main-belt asteroids
Belskaya, Irina
The parameters characterizing magnitude phase dependences of asteroids are found to be very similar for objects belonging to the same composition type. The discovered correlation of the photometric parameters such as the amplitude of the opposition effect and phase slope on albedo gives an alternative way to estimate asteroid's albedo (Belskaya and Shevchenko, Icarus 197, 94, 2000). Thus, the measurement of magnitude-phase dependence of an asteroid can provide complimentary information on its albedo and composition type. We present new photometric observations of the selected asteroids from the outer part of asteroid belt. The asteroids were selected based on their high values of radiometric albedos given by the WISE and/or AKARI infrared surveys. Our aim is to compare their magnitude phase dependences with those from the inner part of asteroid belt and to provide an independent check of surface albedo and composition type of these asteroids. Knowledge of the fraction of high-albedo asteroids in the outer asteroid belt where majority of asteroids have low albedo surfaces is important for understanding the formation and evolution of our Solar system.
The Arab Astronomical Society (ArAS): Developing Astrophysics Research in the Arab World
Benkhaldoun, Zouhair
The Arab Astronomical Society (ArAS) was officially created during the constitutional assembly held in Marrakech (Morocco) on November 30, 2016. ArAS is composed of a group of Arab researchers and students in the field of astrophysics who aim to develop research in this field in the Arab world (22 countries). ArAS is working on bridging the gap between the Arab astrophysicists in the Arab world and those around the world by organizing collaborative workshops, international scientific meetings, offering scholarships, and developing graduate programs in astrophysics. ArAS is working on establishing scientific infrastructure in the Arab world by training advanced undergraduate and graduate students in astrophysics and stimulating the built of new telescopes on the best sites in the Arab world. This will be accomplished through the hosting of specialized schools in astrophysics, facilitation of students' and postdocs training in international research centers and universities, the establishment of prizes in astronomy to honor leading Arab scientists in astronomy and to motivate young people to present distinctive works in astronomy.We present here the main goals of ArAS, its Strategic Plane at short, medium, and long term, as well as the organizational structures that will enable us to achieve our goals. We present methods and platforms to disseminate astronomy in the Arab World through the Arab Scientific Community Organization. We give as well, some information we could gather about the situation of astrophysics research at the Arab countries in term of astrophysics institutions and astronomical observatories they hosted.
Transiting Exoplanets and Their Atmospheres in the Era of James Webb Space Telescope: What We expected for the Systems like TRAPPIST-On/Seven Planets?
Benkhaldoun, Zouhair
Among the thousands of known exoplanets, the few of them that transit bright nearby stars have had the highest impact on our overall understanding of the large planetary population hosted within our galaxy. This is because their detailed characterization (mass, size, orbit, atmosphere, obliquity, etc.) can be measured with existing observational technology. The last decade saw the first observational constraints on the atmospheric properties of short-period planets transiting nearby stars, including the first firm detections of molecular signatures in exoplanetary atmospheres. These pioneering studies, performed with space and ground-based instruments, have provided initial glimpses at the atmospheric chemical and molecular composition, vertical pressure-temperature profiles, albedos, and circulation patterns of extrasolar worlds. The next major step is undoubtedly the upcoming launch of the James Webb Space Telescope (JWST), the Transiting Exoplanet Survey Satellite and CHaracterising ExOPlanet Satellite. These space-borne missions will offer an unprecedented capability to study of these nearby transiting exoplanets. JWST is particularly important, since it will provide large aperture, a heliocentric orbit, and continuous wavelength coverage from 0.6 to 28 microns. It should be powerful enough to make possible detailed atmospheric characterization not only of hot Jupiters but also of smaller planets. This sample will include more temperate terrestrial planets recently found orbiting in the habitable of nearby very-low-mass red dwarfs. The TRAPPIST-North Telescope Located at the Oukaimeden Observatory in Morocco contributed critical data to discovery of TRAPPIST exoplanetary system orbiting the TRAPPIST-1 red dwarf star. We propose to present a discussion about the scientific information we expected to gather from JWST data set in the observations of the Trappist-1 system in advance of the congress that we intend to organize in Marrakech on this subject in 2020.
Atlas Dark Sky Reserve: Towards the creation of the First Dark Sky Reserve in North Africa
Benkhaldoun, Zouhair
In 2016, Morocco organized the United Nations Climate Change Conference (COP22) in Marrakech. Following this conference, Morocco, like other countries, has made the commitment to become a major player in the fight against pollution. In this context, the Atlas Dark Sky project was born and today it becomes a reality and a project in progress. In fact, the broad spectrum of impacts of light pollution is directly related to pollution and thus global warming. To cite only one example, taking measures against light pollution will reduce the energy bill of the countries and consequently reduce their contribution to the carbon emission.In this poster, we will present the Atlas Dark Reserve project, a project that aims to create the first Dark Sky reserve in North Africa and the biggest one in the world. The Observatory of Oukaïmeden located at the Atlas Chain in Morocco will be the central region of this reserve. Dark Sky Communities will be composed of about 120 villages and cities located in a diameter of 80 km from the central region. We will present our Strategic Plan (2018-2021) to create Atlas Dark Sky reserve in Morocco.
MAPPINGS photoionization models of H II regions in dwarf irregular galaxies
Bensch, Katarzyna
Star-formation has a direct influence on chemical abundances of galaxies. Gas-rich dwarf irregular galaxies (DIGs) are less chemically evolved and therefore are great laboratories for detailed studies of chemical evolution. Their star-formation histories are simpler than those of massive galaxies. Especially isolated DIGs are important sources for understanding star-formation. They have been formed and evolve far from dense cluster centres and the gravitational influences of massive companions. The isolation allows us to study star-formation that originates purely from evolutionary processes of the pristine IGM in galaxy environments. We use Integral Field data to study 7 metal-poor DIGs with VLT/VIMOS and 13 isolated gas-rich DIGs from the SIGRID sample obtained with WiFeS. The H II emission suggests ongoing star-formation for the past 5 Myr. Metallicity estimates for HII regions of DIGs are one of the most important tools towards an understanding of galaxy evolution since those studies require a precise metallicity calibration. We derive theoretical models using the MAPPINGS photoionization modelling code to predict theoretical emission line ratios at different values of metallicity and ionization parameters. The detection of multiple emission lines of H, O, N, Ne, He, S, and Fe allows us to use and compare different line-ratio grids to study the metallicity of the different HII regions. We investigate their resolved chemical composition, paying special attention to the metallicity-age connection. We discuss the problems arising from the limitations of simple geometric models and depletion of elements onto dust. The spatially resolved star formation history is consistent with the predictions from the models over the several hundred million years.
??Mean field dynamo in dwarf galaxies
Bera, Prasanta
Dwarf galaxies are generally faint but these are highly abundant in number count. Some of these galaxies (e.g. NGC 1569, IC 10, NGC 4449) show a strong large-scale magnetic field of strength about 10µG or more. The presence of an ordered strong magnetic field with similar strength in spiral galaxies is considered to be generated from the seed magnetic field by the dynamo action due to the differential rotation in the disk plane. On the other way, the strength of the differential rotation is small in a dwarf galaxy hence does not usually prefer large-scale dynamo. From the study of mean field dynamo in a thick disk, we find that the resistive dissipation is effectively less due to thicker vertical height. It can generally explain the strong ordered magnetic field in the dwarf galaxies.
Following the trail of water from interstellar space to inhabited planets with the Origins Space Telescope
Bergin, Edwin
The Origins Space Telescope (OST) is one of four mission concepts that NASA is exploring in advance of the next decadal survey in the United States. OST has tremendous relevance for tracing the origins of the stars, planets, and life from first light to present day. In this talk I will describe the latest mission concept, which will have a circular 5.9m aperture with a cryogenically-cooled telescope. The instruments will cover wavelength ranges from 5 to 400+ microns and include both spectrographs and imagers. In the mid-infrared, a purpose-built spectrometer will constrain the atmospheric composition and thermal structure of temperate Earth-size worlds via the transit technique with the goal of detecting two distinct biomarkers (methane and ozone), along with water and CO2. This suite of molecules will determine whether the atmospheres of these potentially habitable worlds are in disequilibrium -- the signature of life. With its tremendous spectral grasp and superb sensitivity, OST will survey water, both gas-phase and ice, toward as many as a thousand sources spanning all evolutionary stages of star and planet formation from molecular clouds to YSOs to planet-forming disks. OST will possess the capability to measure the water's distribution in planet forming disks through observation hundreds of lines from the ground state lines that probe beyond waters iceline to higher energy transitions that emit only from interior to the snowline. OST can also sample the water content via a combined study using a unique far-IR tracer of the highly uncertain disk gas mass, hydrogen deuteride. I will also discuss how OST will transform our knowledge of the origin of Earth’s water by extending the sample of cometary bodies with detections of the D/H fingerprint by over an order of magnitude.
LIGHT, WATER, LIFE: THE SEARCH FOR NEW WORLDS IN THE GALAXY. AN EDUCATIONAL PROJECT AT REGIONAL LEVEL IN ITALY
Bernagozzi, Andrea Ettore
Progetto Diderot, devised, proposed and realised by the Fondazione CRT of Turin (www.fondazionecrt.it), is one of the leading high-level educational initiatives in Italy. During the school year 2017-18, it included for the first time a project line devoted to astronomy, thanks to the collaboration with the Astronomical Observatory of the Autonomous Region Aosta Valley (www.oavda.it). The topic is one of the most intriguing fields in current science: the search for alien worlds and their comparison with the Solar System. This entails a multidisciplinary approach that exploits the fascination of cosmos to span fields as diverse as maths, physics, chemistry, Earth sciences, biology, as well as history, philosophy, literature and the arts.From November 2017 to April 2018, the activities of the project have reached more than 6.000 students in the Italian regions of Piedmont and Aosta Valley. The proposed activities are:Teaching Unit 1: “Let’s colour the planets”, for the primary school (age 6-10)Teaching Unit 2: “Let’s pack the suitcase for space”, for the middle school (age 11-13)Teaching Unit 3: “A thousand billion planets”, for the secondary school (age 14-18)An optional follow-up activity has also been proposed to middle and secondary schools; it asked the students to lay down a scientific report.The project required a sizeable logistic and educational effort in order to organise the activities held in hundreds of classes during 6 months, and to figure out the best strategies to pass down the scientific contents. Our presentation describes the project’s origin, how the contents have been devised, the methods developed to impart them, and the feedback got from the students. In the next school years, the project is expected to collect valuable information about the relationship between the school and research domains and to help us assess the impact that astronomy-based activities have on school curricula.
The International Virtual Observatory Alliance
Bertocco, Sara
At the beginning of 2000s, astronomers had the dream to realize a Virtual Observatory, i.e. a system allowing scientists to access and analyze data coming from different astronomical instruments (telescopes, space missions and simulations) and archives as they are taken from a unique observatory. To achieve this result, it was needed to build a world wide infrastructure able to provide access to data coming from different instruments and stored in different archives, giving scientists the ability to discover, analyze and combine real and simulated data. This can be done making data and archives interoperable and accessible in a seamless way.The International Virtual Observatory Alliance (IVOA), formed in 2002, is the organization that debates and agrees the technical standards that are needed to make the VO possible. It also acts as a focus for VO aspirations, a framework for discussing and sharing VO ideas and technology, and body for promoting and publicizing the VO.21 national and international VO project actually participate in the IVOA, that has the mission to “facilitate the international coordination and collaboration necessary for the development and deployment of the tools, systems and organizational structures necessary to enable the international utilization of astronomical archives as an integrated and interoperating virtual observatory".The IVOA encourages observatories, universities, and astronomy projects worldwide to become involved in the VO as data, information, and computational service providers, and as consumers of the enriched, multiwavelength view of the Universe.In this poster we describe IVOA organization and current status of the VO in terms of tools, available data and standards. We present also the IVOA tools and activities developed for astronomy outreach and education.
Assessing the NUV variability of stars across the spectral sequence
Bertone, Emanuele
Intensity and variability of the stellar ultraviolet radiation is one of the main variables that affect the space weather of planets and determine their conditions of habitability.We present a thourough study of the variability of stars of all spectral types in the near ultraviolet band (NUV), by using data from the GALEX-CAUSE survey of the Kepler field.The whole Kepler field was observed in the NUV band (1771-2931 angstrom), during 46 days in 2012 AugustSeptember, using 300 GALEX orbits, funded by Cornell University (PI J. Lloyd). We constructed a large photometric catalog of light curves of more than 400,000 stars of all spectral types, that we used to determine the flux variability as a function of spectral type.Through the use of diagnostic diagrams we are also able to characterize the kind of variability of these objects. Preliminary results indicates a median NUV flux variability of 11% for solar analogs.
New eyes on planet-disk interactions
Bertrang, Gesa H.-M.
The circumstellar disk around the Herbig Ae/Be star HD169142 is a well-studied object which shows structures on multiple wavelength ranges. Moreover, HD169142 harbors the most promising proto-planet candidate._x005F We present new SPHERE/ZIMPOL data which distinctly deviate from the established picture developed for this object. Based on these new observations as well as high-resolution ALMA observations and further archival data, we built a new model for this disk. These new eyes, namely SPHERE and ALMA, in combination with 3D radiative transfer simulations strongly indicate that we are witness to previously undetected planet-disk interactions in HD169142.
Magnetic fields and polarimetry in planet-forming disks
Bertrang, Gesa H.-M.
Understanding the physical processes in planet-forming disks is vital for the understanding of planet formation. It has been predicted that magnetic fields are an important factor on a wide range of these mechanisms, such as the migration of planet(esimals) and the mere evolution of disks. Yet, observational constraints are still pending. In the classical picture, (sub-)mm continuum polarization is the tracer for magnetic fields in disks. Aspherical dust grains, whose thermal emission is intrinsically polarized, get aligned by the magnetic field due to radiative torques. In recent years, however, this picture has been challenged. New theoretical studies show that (sub-)mm continuum polarization can also be created by scattering of the thermal dust emission or arise from aspherical grains which are aligned by the radiation field rather than the magnetic field. These three mechanisms trace fundamentally different physics in protoplanetary disks, yet, their polarization predictions are not clearly distinguishable. I will give an outlook on how to disentangle the sources of continuum polarimetry with ALMA by applying spectro-polarimetry, and present the first predictions for linear line polarization in disks.
Laboratory simulation of astrophysical jets within facilities of Plasma Focus type
Beskin, Vasily
A laboratory simulation of astrophysical processes is one of the intensively developed areas of plasma physics. A new series of experiments has been launched recently on the Plasma Focus type facility in NRC Kurchatov Institute. The main goal is to study the mechanisms of the jet stabilization, due to which it can propagate at distances much greater than their transverse dimensions. The experiments with stationary gas filling revealed regimes in which a narrowly collimated plasma jet was formed, the head of which was no wider than several centimeters at jet propagation distances of up to 100 cm. The PF-1000 (IFPiLM, Warsaw, Poland) and KPF-4 (SFTI, Sukhum, Abkhazia) experiments are aimed at creating profiled initial gas distributions to control the conditions of plasma jet propagation in the ambient plasma. Estimations of the dimensionless parameters, i.e. the Mach, Reynolds, and Peclet numbers which were achieved during the experiments, showed that the PF-facilities can be used for the YSO jets modelling. Thefuture experiments, which can allow one to understand the nature of the stable plasma ejections observed in many astrophysical sources, are discussed.
Radio pulsar alignment/counter-alignment - final test?
Beskin, Vasily
At present, there are theoretical models of radio pulsar evolution that predict both the alignment, i.e. evolution of inclination angle between magnetic and rotational axes to zero degree and its counter-alignment, i.e. evolution to 90 degree. At the same time, both models describe well the pulsar distribution on the P–P diagram. For this reason, up to now it was impossible to determine the braking mechanisms since it was rather difficult to estimate the evolution of the inclination angle for individual pulsar based on observations. In this poster, we demonstrate that the statistics of interpulse pulsars can give us the key to solve the alignment/counter-alignment problem as the number of interpulse pulsars drastically depends on the evolution of the inclination angle.
Faint Dwarf galaxies in nearby WINGS clusters: photometric characterization
Bettoni, Daniela
In the cores of galaxy clusters there is a population of lows-mass stellar systems such as dwarf Early-type galaxies, ultra-compact dwarf galaxies (UCDs) and ultra diffuse dwarf galaxies. We present here the photometric and morphological characterization of this population of objects using deep CFHT images of a sample of clusters belonging to the WINGS survey (0.04<z<0.06).we study="" only="" galaxies="" that="" are="" spectroscopically="" confirmed="" members="" of="" the="" cluster.="" population="" dwarfs="" ranges="" from ="" ~30%="" for="" more="" rich="" clusters="" to ="" ~5-6%="" less="" ones.="" we="" found="" a="" red="" and="" blue="" discuss="" their="" properties="" in="" comparison="" with="" cluster="" characteristics.="" finally="" this="" sample="" compared="" data="" from="" nearby="" as="" virgo="" coma.="" implications="" mechanisms="" formation="" dwarf="" systems="" briefly="" discussed.<="" p="">
</z<0.06).we></p>
Quasar activity in the neighboring Universe
Bettoni, Daniela
We analyzed the properties of the close environments of a sample of low redshift quasarsto investigate the role of interactions for triggering and fueling the QSO phenomenon.We present the results of an extensive spectroscopic campaign at GTC and NOT telescopes in La Palma aimed at deriving the properties of companion galaxies of quasars anddetecting signatures of recent star formation both in the host galaxies and in the companion galaxies.The sources are drawn from a large (~400) sample of (z<0.4) quasars extracted from the SDSS "Stripe 82" for which we previously investigated the host galaxies and the large scale environments properties.We found that the close (<100 kpc) companion galaxies are often associated to the QSO but only a modest recent star formation is present. The implications for the mechanisms ofnuclear activity are briefly discussed.
Elemental abundances of primary stars in Sirius-like systems: Constraints on pollution from AGB stars
Bharat Kumar, Yerra
Study of primary stars lying in Sirius-like systems with various masses of WD companions and orbital separations is one of the key aspects to understand the origin and nature of Barium (Ba) stars, wherein enhanced carbon and/or s-process elements are suggested through mass transfer from AGB companions. We have analysed chemical composition of 21 FGK primaries, including dwarfs and giants, systematically using good quality high resolution spectra. Three Ba dwarfs are discovered which provides the first direct evidence of Ba dwarfs are with WD companions. On the other hand, absence of s-process enrichment is observed in stars even their companion WD mass is large enough to produce these elements during their TP AGB phase. Surface abundances of s-process elements in our sample are compared with AGB models of respective masses estimated from their WD masses. Results suggest s-process enrichment in sample Ba dwarfs follow McClure hypothesis similar to Ba giants. A few conclusions are drawn from this study: large mass of WD (>0.51 Msun) is not only the sufficient condition to form a Ba star, orbital separation is not main constraint to differentiate between strong and mild Ba stars, and different levels of s-process abundances among Ba stars may not be dominated mainly by the metallicity.
Time-series analyses of Cepheid and RR Lyrae variables in the wide-field variability surveys
Bhardwaj, Anupam
Stellar variability studies are undergoing a renaissance with many large ongoing or soon to start surveys that focus on exploring time-domain in addition to multi-wavelength and wide-area approach. Cepheid and RR Lyrae are pulsating variable stars that are both primary standard candles and tracers of the stellar populations and structure of the host galaxy. These variables provide a unique opportunity to explore strong constraints for stellar pulsation models by an extensive comparison of theoretical and observed light curves and their pulsation properties. We present a detailed light curve analysis of Cepheid and RR Lyrae variables with the largest observational dataset derived from the time-resolved wide-field variability surveys. A quantitiative and multiwavelength comparison with the theoretical models, generated from the stellar pulsation codes, provides stringent constraints for the input parameter space, such as the mass-luminosity relations, to the pulsation models. We further discuss the impact of convective efficiency and opacity in pulsation models on the light curve structure and pulsation properties of Cepheid variables. We will also present results of Cepheid and RR Lyrae stars from the near-infrared time-series surveys of the Large Magellanic Cloud (LMCNISS) and the Milky Way (VVV) and discuss multiband Period-Luminosity relations and their application to extragalactic distance scale. In the era of ELT(s), these fundamental tests between theory and observations will be more feasible and will help in advancing our understanding of the theory of stellar evolution and pulsation.
Solar variability and climate change – an Empirical Analysis
bhargawa, asheesh
Sun in the main source of energy for our planet therefore even a slight change in its output energy can make a huge difference in the climatic conditions of the Earth. The rate of energy coming from the Sun (solar irradiance) might affect our climate directly by changing the rate of solar heating of the Earth and atmosphere and indirectly by changing cloud forming processes. In the present paper, based on stability test of the Vector autoregressive (VAR) model, we have used impulse response functions and variance decomposition method for the analysis of climate variability. We have examined the possible connection between the solar irradiance and some climate indicators, viz., the global temperature anomaly, the global mean sea level, global sea ice extent and the global precipitation anomaly since last forty years (1978-2017). We have noticed that these parameters have shown changing patterns during the last few decades. In addition, we have also tried to find the role of atmospheric carbon dioxide as a greenhouse gas in the climate change. Considering global surface temperature anomaly (land + sea) as the most important indicator of clime change and using the impulse response function analysis and variance decomposition method, we have tried to answer the questions whether the climate system is subjecting to a solar irradiance shock or what is the contribution of rise in CO2, etc?
Studying the high redshift universe combining JWST and the power of gravitational lensing
Bhatawdekar, Rachana
Exploring the very first galaxies is one of the major contemporary problems in astronomy. We do not know when the first galaxies formed, nor how their formation occurred. The James Webb Space Telescope (JWST) will be launched between March and June of 2019 and will search for the First Light objects in the redshift range of z=10-15. Reaching these galaxies will be routine with JWST, however, until then, our best chance to study these systems is through deep observations of lensing clusters with the Hubble Space Telescope (HST) by using them as `Cosmic Telescopes'. Therefore, to extend its reach even farther beyond its technical capabilities before JWST is launched, the HST is observing six massive clusters of galaxies as gravitational lenses to find the faintest and earliest galaxies in the Universe, ~10-100 times fainter than any previously studied, as a part of the Hubble Frontier Fields (HFF) program. In this talk, I will present how we detect and examine the objects behind HFFs lensing cluster MACSJ0416.1-2403, Abell 2744 and their parallel fields. We have developed a novel method to subtract the massive galaxies from these clusters, allowing for a deeper and cleaner detection of the faintest systems. We present a photometric study of distant z>5 galaxies using all 10 bands available for Frontier Fields (HST, Spitzer and K-band). From this, we have derived the first galaxy stellar mass function (GSMF) at z > 5 for Frontier Fields program. I will further discuss how these results reveal new information on the faint-end of the mass function from the faintest galaxies at high-z, unveiling the potential science that can be done with JWST data.
The evolution of galaxy stellar mass functions at z = 6-9 in the Hubble Frontier Fields
Bhatawdekar, Rachana
Exploring the very first galaxies is one of the major contemporary problems in astronomy. We do not know when the first galaxies formed, nor how their formation occurred. The James Webb Space Telescope (JWST) will be launched between March and June of 2019 and will search for the First Light objects in the redshift range of z=10-15. Reaching these galaxies will be routine with JWST, however, until then, our best chance to study these systems is through deep observations of lensing clusters with the Hubble Space Telescope (HST) by using them as `Cosmic Telescopes'. Therefore, to extend its reach even farther beyond its technical capabilities before JWST is launched, the HST is observing six massive clusters of galaxies as gravitational lenses to find the faintest and earliest galaxies in the Universe, ~10-100 times fainter than any previously studied, as a part of the Hubble Frontier Fields (HFF) program. In this talk, I will present how we detect and examine the objects behind HFFs lensing cluster MACSJ0416.1-2403, Abell 2744 and their parallel fields. We have developed a novel method to subtract the massive galaxies from these clusters, allowing for a deeper and cleaner detection of the faintest systems. We present a photometric study of distant z>5 galaxies using all 10 bands available for Frontier Fields (HST, Spitzer and K-band). From this, we have derived the first galaxy stellar mass function (GSMF) at z > 5 for Frontier Fields program. I will further discuss how these results reveal new information on the faint-end of the mass function from the faintest galaxies at high-z, unveiling the potential science that can be done with JWST data.
Multi-wavelength intraday variability studies: what do they tell us about blazar Jets?
Bhatta, Gopal
Intraday variability studies are the most important, if not the only, tools to explore the physical processes occurring at the innermost blazar regions which are not resolved by any current instruments. In this presentation, we report the results of intraday variability in the optical (BVRI bands) and hard X-ray band (3-79 keV) in a number of blazars consisting of both BL Lacs and flat spectrum radio quasars. In the optical microvariability studies of low-synchrotron peaked blazars S5 0716+714 and BL Lac, we observed many interesting features such as rapid variability, large variability amplitude, presence of characteristic timescales, bluer-when-brighter achromatic behavior, and single power-law power spectral density. In 31 NuSTAR observations of 13 blazars, using spectral and timing analysis, we found similar features consistent with the ones from the optical studies. In addition, in BL Lacs we estimated the Lorentz factor of the population of highest energy electrons emitting synchrotron emission, and whereas in flat-spectrum radio quasars, using external Compton models, we estimated the energy of the lower end of the injected electrons to be a few Lorentz factors. In addition, we find that the low flux state exhibit more rapid variability in contrast to the previously reported results showing high flux states displaying rapid variability. In both the studies, the size of the emission regions estimated using variability timescales turn out to be an order magnitude smaller than the gravitational radius of a typical black-hole masses between 10^8-10^9 solar masses which are believed to be harbored by the radio-loud AGN. The results of the studies suggest that these low-amplitude rapid variability might originate as a result of magnetohydrodynamical instabilities near the base of the jets triggered by the processes modulated by the magnetic field at accretion disc.
WFIRST Microlensing Exoplanet Characterization with HST Follow up Astrometry
BHATTACHARYA, APARNA
More than 50 planets are discovered with the different ground based telescopes available for microlensing. But the analysis of ground based data fails to provide a complete solution. To fulfill that gap, space based telescopes, like Hubble space telescope and Spitzer are used. My research work focuses on extracting the planet mass, host star mass, their separation and their distance in physical units from HST Follow-up observations. I will present the challenges faced in developing this method.This is the primary mass measurement method to be used for NASA's top priority project (according to 2010 decadal survey) Wide Field InfraRed Survey Telescope (WFIRST) Exoplanet microlensing space observatory, to be launched in 2025. The unique ability of microlensing is that with WFIRST it can detect sub-earth- mass planets beyond the reach of Kepler at separation 1 AU to infinity. This will provide us the necessary statistics to study the formation and evolution of planetary systems. This will also provide us with necessary initial conditions to model the formation of planets and the habitable zones around M dwarf stars.
Developing Astronomical Skills in Nepal
Bhattarai, Suresh
Developing Astronomical Skills in Nepal (DASN) is a new initiative at Nepal Astronomical Society (NASO) designed for undergraduate students in Nepal. It aims to motivate undergraduate students for project works in space science/astronomy/astrophysics and help during their project/research work.This paper aims to share the progress of the initiative and highlights the importance of the Information and Communication Technology (ICT) for the implementation of this challenging initiative in Nepal. The challenges we faced during the communication to different colleges for the participation will also be shared. Our strategic approach to have active role of each colleges of the participants in the initiative will be explained. It will also share how we are integrating this program to promote capacity building in each of the seven federal states of Nepal.
Spatial variations of scattering polarization signatures at sugranular scales
Bianda, Michele
The scattering polarization signals measured in the Sr I 460.7 nm spectral line on the solar disk are usually an average over a surface area exceeding the typical granular size. Variation in intensity and orientation of the magnetic field plus spatial and temporal variations in the plasma properties are expected to cause variations in the amplitude and orientation of the scattering polarization measured at subgranular scales. The Hanle effect and anisotropies in the radiation field are the origin of these modifications. The measurement of these variations is challenging, because high polarimetric precision and high spatial resolution are needed at the same time. However, the diagnostic potential of these measurements is promising. We report here first successful observations performed using the ZIMPOL polarimeter at the GREGOR solar telescope on Tenerife.
The Future of Astronomy Education: A Teaching Tool for Visually Impaired Students
Bieryla, Allyson
Astronomy education and observational astronomy labs, in particular, have been lacking resources to accommodate students with visual impairments. We have adapted our observational astronomy lab at Harvard University to accommodate students with a visual impairment. Using sound and thermoform printing technologies, we have capabilities to allow student’s with a visual impairment to participate in labs at the same time as the other students. In particular, we developed a device using arduino technology that converts light to sound. We tested this device during this past summer’s total solar eclipse and streamed the data live on the Internet for people around the world to experience the event. We are now adapting our arduino device to incorporate color using RGB filters. This device will produce different timbres for different wavelengths of light that can then be used to distinguish different temperatures. The device is handheld, easy to program and inexpensive to reproduce (< $50). It is also fitted to mount on a telescope for nighttime observing. The design schematic and code will be open source and available for download.
Full-Disk CII Mapping of the Star Forming Nearby Disk Galaxy NGC6946 with SOFIA/FIFI-LS
Bigiel, Frank
Our poster presents results from our analysis in progress of one of thefirst, complete CII maps at high (15") resolution across the entire starforming disk of the nearby spiral galaxy NGC6946. This data set fromFIFI-LS onboard SOFIA allows us to study CII emission and key ratios,like CII-to-CO (a tracer of the CO-dark gas) or CII-to-TIR (a measure of thephotoelectric heating efficiency), across the galaxy disk and as a functionof local conditions (dust properties, radiation field, etc.). By means ofstacking the large number of independent spectra provided by the full diskmapping data, we also perform high significance arm-interarm comparisonsof these quantities to study the impact of dynamical environment. Finally,we compare CII emission to accurately calibrated, canonical SFR tracers(e.g. H-alpha+IR) and assess its use as a star formation rate tracer acrossdisk galaxies.
Stellar feedback in the Blue Compact Dwarfs ESO338-IG04 and Haro 11
Bik, Arjan
Luminous blue Compact galaxies are local strongly star-forming dwarf galaxies. They host dozens of super star clusters and are considered to be analogues of high redshift dwarf galaxies. These galaxies give us the unique laboratories to study the effect of feedback from super star clusters on the interstellar medium, determine the conditions under which they become Lyman continuum leakers and help probing the role that high-redshift dwarf galaxies play in the re-ionization of the universe.We present deep optical integral field spectroscopy with VLT MUSE of two local blue compact dwarf galaxies ESO 338-IG04 and Haro 11. The MUSE datasets reveal that the galaxies are embedded in extended halos of ionized gas. Analyses of the ionized gas, using optical forbidden emission lines, reveal that Wolf-Rayet dominated super star clusters are responsible for creating ionization channels extending all the way to the edges of the halo, possibly facilitating the escape of Lyman Continuum photons. We also find evidence for chemical enrichment by the Wolf-Rayet stars.In particular we find evidence for supernovae induced feedback in the shape of a superbubble and a galactic scale outflow in ESO 338. Analysis of the spatially resolved BPT diagram reveals the presence of shocks around the central starburst as well as the location where the outflow meets the more quiesence gas in the galaxy halo.Finally, using the high quality MUSE observation of local dwarf galaxies, we present simulated observations for ELT/MOSAIC of dwarf galaxies at redshift 1-2 in order to determine what physical parameters of the halo we can derive at those redshifts with the next generation of telescopes.
The missing V-type NEAs
Birlan, Mirel
The missing V-type NEAs.Birlan, M. (1,2), Nedelcu D.A. (2,1), Sonka, A.(2,3), Dumitru, B(1,2,3).1) Institut de Mecanique C ´ eleste et des Calculs des ´ Eph ´ em´ erides, CNRS UMR8028, Paris Observatory, PSL Research University, 77 av Denfert Rochereau, 75014 Paris cedex, France e-mail: Mirel.Birlan@obspm.fr2) Astronomical Institute of Romanian Academy, 5-Cut¸itul de Argint, 040557 Bucharest, Romania3) Faculty of Physics, Bucharest University, 405 Atomistilor str, 077125 Magurele, Ilfov, RomaniaThe orbital distribution of the known V-type NEAs cannot explain the June peak we observe in the number of HED (howardite, eucrite, diogenite) falls (Birlan et al A&A, 581, 2015). Giving that all the NEAs with MOIDs smaller than 0.1 AU are a potential source of meteorites (Olsson-Steel, Icarus, 75, 1988) we ran using SpeX/IRTF facility a NIR spectroscopic survey of NEAs with MOID < 0.1 AU and orbits that are approaching Earth around June. Basaltic NEAs at the origin of meteor showers associated with HED falls provide important constraints on the large differentiated parent bodies of V-type asteroids. This works presents the results of the survey with the emphasis on spectroscopic and dynamic characterization of 2 PHAs: (4953) 1990 MU and (192563) 1998 WZ6.
Time lag in transient HMXB, and other disk accreting sources
Bisnovatyi-Kogan, Gennagy
Model is developed for time lag between maxima of the source brightness in different wave-lengths, during a transient flash of luminosity, connected with a short period of increase of themass flux onto the central compact object. A simple formula is derived for finding the time delayamong events in different wavelengths, valid in general for all disk accreting cosmic sources. Inclose binaries with accretion disks the time lag is connected with effects of viscosity defining aradial motion of matter in the accretion disk. The validityof these model is shown by comparison with observations of several galactic accretingsources.
Imaging spectroscopy of decimetric type-III bursts by MUSER
Bisoi, Susanta Kumar
The energy released during flares accelerates particles somewhere in the lower corona, which can be located and best studied using radio observations of electron beams detected in the decimetric frequency range. However, due to the limited imaging available at this frequency range, particularly 500-1000 MHz, the exact location of electron acceleration and so the flare energy release has still remained poorly known. Using the low frequency array of Miangtu Spectra Radio Heliograph (MUSER), operating at the frequency range 400-2000 MHz with the capabilities of high temporal (25 to 200 ms), spatial (1.3 to 50 arcsec) and spectral (25 MHz) resolution, in combination with microwave, hard X-ray (HXR) and extreme ultra-violet observations, we investigated decimetric type III bursts observed, in the frequency band 400-700 MHz, at the start of a GOES C2.3 flare that erupted on 20 June 2015. The obtained high time cadence images of MUSER show that the radio burst sources are propagating along different coronal loops and are located far from the site of HXR and microwave sources. Most of the decimetric type-III bursts are identified as either reverse slope bursts or spikes with the brightest type-III emission occurring at the very start, which clearly suggest they are associated with the primary energy release sites. Also, the different spatial locations of the bursts, as identified from MUSER images, show that the energy release is fragmentary in nature.
Pulsar Search Collaboratory
Blumer, Harsha
Pulsar Search Collaboratory (PSC), funded by the National Science Foundation (NSF), is a collaborative research program between Green Bank Observatory (GBO) and West Virginia University (WVU). Through the PSC, we are building a nationwide community engaging high-school students, their teachers, and undergraduate mentors to search for pulsars (rapidly rotating neutron stars) using data collected with the 100-m Green Bank Telescope (GBT). In the process, the students learn about observational radio astronomy, radio frequency interference, pulsar timing, and data analysis procedures. The primary goals of the PSC are to stimulate student interest in Science-Technology-Engineering-Math (STEM) careers, to prepare teachers in implementing authentic research with students by training them within a professional scientific community, and to promote student use of information technologies through online activities and workshops. The pulsars discovered by the PSC students will be used for fundamental advances such as for testing of general relativity, constraining neutron star masses, or detecting gravitational waves. Here, we present the strategy and challenges of implementing the program and the scientific and educational research results thus far.
Constraints on repetitions and source location from Parkes observations of the Lorimer Burst
Blumer, Harsha
Fast radio bursts (FRBs) are highly dispersed, transient sources of radio pulses with durations of a few milliseconds. The origin of FRBs still remains unknown, although mechanisms involving neutron stars are often posited as they are consistent with the implied energetics. The Lorimer Burst, or the first FRB 010724, was discovered by Lorimer et al. (2007) using archival data from the 64-m Parkes radio telescope pulsar survey at 1.4 GHz. This event had a peak flux density of > 30 Jy and duration of ~5 ms. Since then, tens of these events have been observed with only one FRB 121102 (the “repeater”) showing repetitive burst activity. It is not clear whether the repeater is the prototype of FRBs or is a member of a unique source class. To determine this, we revisited FRB 010724 with the Parkes telescope to search for any repeated bursts. We present our results from this search and, making assumptions about FRB 121102, place strong constraints on the distance, amplitude distribution, and repetition rate from this source.
All-sky Medium Energy Gamma-ray Observatory (AMEGO)
Blumer, Harsha
The gamma-ray energy range from a few hundred keV to a few hundred MeV has remained largely unexplored since the pioneering but limited observations by COMPTEL on the CGRO (1991-2000). Fundamental astrophysics questions can be addressed by a mission in the MeV range, from astrophysical jets and extreme physics of compact objects to a large population of unidentified objects. To address these questions, we are developing the concept of AMEGO: All-sky Medium Energy Gamma-ray Observatory, within the NASA Probe class mission, to investigate the energy range from 300 keV to >10 GeV with good energy and angular resolution and with continuum sensitivity approaching a factor of 20-50 better than previous measurements. AMEGO will be capable of measuring both Compton- scattering events at lower energies and pair-production events at higher energies and will enable spectrometric measurements of nuclear lines. AMEGO will contribute to our understanding of the mechanism of GRB, pulsars and blazar jets operation, as well as be an excellent facility for the search for gravitational wave counterparts to binary mergers including at least one neutron star, which are thought to produce short duration GRBs.
Impact of the interstellar medium on processes on Earth
Bochkarev, Nikolai
Impact of the interstellar medium on processes on EarthN.G.Bochkarev Sternberg Astronomical Institute of Moscow State University The paper discusses possible impacts of the interstellar matter (ISM) on processes on Earth, first of all those, which may affect the Earth biosphere. ISM parameters, determining the degree of penetration of galactic cosmic rays, interstellar atoms and ions into the Solar system and their impact on Earth varies considerably as the Sun moves through different ISM regions. In some cases the impact may provoke severe environment changes substantial for the life on Earth.
LONG-TERM SPECTRAL VARIABILITY OF AGNs WITH BROAD EMISSION LINES IN OPTICAL RANGE
Bochkarev, Nikolai
We use our 10-20 year long spectral and photometric observations of optical variability for investigations of the physics and kinematics of AGN central parts, i.e. the emission regions which are close to the super-massive black hole. Here we give an overview of the results of our analysis of AGN optical spectral variability in a sample of AGNs with broad emission lines including radio-laud ones.
Searching for new white dwarf pulsators for TESS
Bognár, Zsófia
We present the results of our survey searching for new white dwarf pulsators for observations by the TESS space telescope. We collected photometric time-series data on 14 white dwarf variable-candidates at Konkoly Observatory, and found two new bright ZZ Ceti stars, namely EGGR 120 and WD 1310+583. We performed the Fourier-analysis of the datasets. In the case of EGGR 120, which was observed on one night only, we found one significant frequency at 1332 microHz with 2.3 mmag amplitude. We successfully observed WD 1310+583 on eight nights, and determined 17 significant frequencies by the whole dataset. Seven of them seem to be independent pulsation modes between 634 and 2740 microHz, and we performed preliminary asteroseismic investigations of the star utilizing these periods. We also identified three new light variables on the fields of white dwarf candidates: an eclipsing binary, a candidate delta Scuti/beta Cephei and a candidate W UMa-type star.
The search for precursors of Solar System alikes in a high-mass star forming area
Bogner, Rebeka
Recent theories on the formation of the Solar System turned the attention to the study of low mass cloud cores in massive star forming regions. The Herschel satellite with its wavelength coverage could detect massive young stellar objects at all evolutionary stages and was able to detect the precursors of O and B stars. The Rosette Molecular Cloud (RMC) at 1.6 kpc from the Sun is a well-known area: the OB cluster NGC 2244 at the centre is blowing a cavity into it, resulting in an expanding HII region interacting with a high-mass star forming molecular cloud which has a highly filamentary structure with dense cores having a wide range of masses. These prestellar and protostellar cores were observed by Herschel and key core properties such as bolometric luminosity and mass were derived from its data. With the Effelsberg 100m telescope a sample of these cores - between 3-40 solar masses - were observed in NH3 (1,1) and (2,2) inversion lines. Ammonia is invaluable in deriving physical parameters of the dense gas such as gas temperature and optical depth, along with revealing the temperature structure it makes the study of core stability possible which are our aims to examine. Compared with Herschel measurements the differences between the dust and gas properties can be investigated. As the origins and evolution of low-mass stars in high-mass star forming environments is still unclear, with our selection of cores we are planning to gain insight - by searching for smaller fragments of cores and examining their properties - on the conditions in which low-mass stars can form in an environment dominated by the effects and feedback of massive star formation - as our Solar System might have originated from such a violent environment.
The TOP-SCOPE survey of Planck Galactic Cold Clumps: The 200 brightest compact sources of Planck
Bogner, Rebeka
The Planck all-sky submillimetre observations have made it possible to study Galactic cold clumps in diverse environments, to probe dust properties and to examine the earliest stages of star formation. The TOP-SCOPE joint survey program aims to statistically study the evolution of molecular clouds and the initial conditions of star formation in a wide variety of environments targeting around 2000 Planck Galactic Cold Cores (PGCCs) in CO isotopologues and around 1000 PGCCs in 850 micrometer continuum emission. In this work we carried out an investigation of the 200 brightest compact sources detected by Planck. These are not necessarily PGCCs, most of them are star forming; out of them 80 have been observed in SCOPE. Using Herschel and JCMT observations we investigated the dust properties of the cores, making column density and dust temperature maps. We also investigated the young stellar objects in the vicinity of the sources to examine their influence on such star-forming sites. We aim to compare the properties of this sample to PGCCs to see how star formation efficiency, clustering behavior and core masses evolve with time.
Close massive binary stars, BH mergers, and BH spins
Bogomazov, Alexey
Recently discovered bursts of gravitational waves provides a good opportunity to verify the current view on the evolution of close binary stars. Modern population synthesis codes help to study this evolution from two main sequence stars up to the formation of two final remnant degenerate dwarfs, neutron stars or black holes. To study the evolution of predecessors of BH mergers we use the "Scenario Machine" code. The scenario modeling allowed to describe the evolution of systems for which the final stage is a massive BH+BH merger. Our calculations show the plausibility of modern evolutionary scenarios for binary stars and the population synthesis modeling based on it. We discuss a possible values of spins of BH mergers, and give arguments in favour of different values of BH spins in BH mergers (low spin + low spin, high spin + high spin, low spin + high spin, etc).
Image Reduction, Detection and Validation of Asteroids using the NEARBY Pipeline
Boldea, Afrodita Liliana
We present a new pipeline software package dedicated to the automated detection of moving objects in astronomical surveys. The pipeline is being developed at the Technical University of Cluj Napoca in collaboration with the University of Craiova (Romania) under the frame of NEARBY project funded by the Romanian Space Agency. Primarily, the pipeline and related tools are planned to be used for the discovery of Near Earth Asteroids (NEAs), identification and reporting of astrometry of other asteroids appearing in each observed field. A comparative study between the performances of the NEARBY pipeline and other available software (such as Astrometrica and Canopus) is also presented.
Education and Science through Astronomy at the University of Craiova and Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering
Boldea, Afrodita Liliana
We present laboratory work aiming to develop practical skills ofuniversity students in order to grow their capacities of scientificanalysis and interpretation of real astronomical data using blendedlearning concepts and specific teaching methods of a virtualclassroom. The flexible didactic strategy includes an Inquiry-basedlearning (IBL) approach combined with some investigation and discoverymethods. Asteroid survey images have been used to generate and improvemodules of training lessons in computational astronomy dedicated tostudents and future teachers of sciences. The taught modules wereaddressed to a small number of students in computer science at the endof their second year of study, the activities being carried out partlyat the University of Craiova (May 2017) and the Horia Hulubei NationalInstitute for R&D in Physics and Nuclear Engineering (IFIN-HH) inMagurele (June 2017) during a three-week professional practiceinternship. This experimental approach of learning proved good resultsin very short term, the involved students acquiring very fast thenecessary skills to approach real astronomical data and computationalastronomy.
Multiwavelength phase curves for asteroid families in the SDSS Moving Object Catalogue
Bolin, Bryce
The surface properties of asteroids are thought to vary with asteroid taxonomy. Differences between the phase curves of asteroids are the result of the different surface light scattering properties of asteroids. Using multi-epoch observations of SDSS Stripe 82, we recover observations of ~25,000 asteroids in the SDSS filters, observed over a range of phase angles. We fit for the wavelength dependence of their phase curves determining these phase curves in the native magnitude system of SDSS which allows us to examine differences in phase curves and absolute magnitudes as a function of wavelength. In a joint analysis of field asteroids, we find a best-fit slope of the phase function that is nearly constant with wavelength in u, g and r bands at Gu, Gg and Gr ~0.2. At longer wavelengths the slope of the phase function increases to Gi and Gz ~0.25-0.3. All values are significantly larger than the nominal value of Gv = 0.15, suggesting a recalibration of the asteroid absolute magnitude system by ~0.1 magnitudes. We examine the standard 1--parameter (Bowell et al. 1988) and recent 2--parameter descriptions of the phase curves, finding nominal improvements using the 2--parameter family that is better able to model the "opposition surge" in apparent magnitude (Muinonen et al. 2010). By using the absolute magnitudes that result from this analysis, we are able to investigate the dependence of the phase curves on absolute magnitude H, and derive principal components of asteroid colors in Hg - Hr, Hr - Hi space. We independently examine asteroids thought to belong to orbital families, and find significant differences between the average phase curves of these families in the different sloan bandpasses. This lends strong credence to diversity in the surface regolith between asteroid families suggested by other studies examining the phase parameter relationship with taxonomy (Oszkiewicz et al.2011, 2012).
Jet formation revealed in post-AGB binaries
Bollen, Dylan
The presence of a binary companion is believed to be the main shaping agent for asymmetric Planetary Nebulae (PNe). The binary interactions induce jet formation which drives the non-spherical structures that we observe in PNe. This is an important feedback mechanism of dust and gas to the galaxy. However, the central regions of PNe are highly obscured. For this reason, we turn our focus to the PN-progenitors, namely post-Asymptotic Giant Branch (post-AGB) binaries. In our recent work, we find that the inner regions of these objects can be observed directly, making them important tracers for jet formation in evolved binary systems. In this talk, I will present our quantitative study on the origin and properties of high-velocity outflows in post-AGB binaries. By comparing a geometrical model of these systems with the observational data, we were able to deduce the jet geometry which revealed that the gaseous circum-companion disk is the origin of the fast outflow. Additionally, by studying the mass accretion rates and jet outflow momenta, we can determine how the changing conditions in the inflow and outflow affect the launching of these jets and their environment. These results are crucial to model binary post-AGB binaries and PNe. This is important to get a better understanding of the binary interaction physics, such that we can provide a more complete description of the further evolution of these systems and their impact on the surrounding environment.
Bridge of hot gas between pairs of clusters: case of A401-A399
Bonjean, Victor
Numerous studies have focused on galaxy-cluster pairs, to characterize and study the hot ionized gas in between them, usually using X-ray and optical data. I will present here the case of the cluster pair A399-A401, an exceptional system with a very hot and tiny filament in between. The high pressure in the filament allows us to study the properties of the gas with the tSZ effect from the Planck data. I will link these informations to the properties of the galaxies in the system, and show how the combination of these two tracers can reveal the nature and the history of this structure.
The recalibration of the UVES-POP stellar spectral library
Borisov, Svyatoslav
High-quality models of stellar populations are in great demand now – they are used to interpret galaxy and star cluster spectra to determine the age, metallicity and other properties. An essential ingredient of stellar population synthesis is a library of stellar spectra. This work is aimed at the recalibration of the UVES-POP library (Bagnulo et al., 2003) to improve flux calibration to the level of 2% or better which is a non-trivial task for multi-order Echelle spectra. We have re-reduced all UVES-POP spectra using the version 5.5.7 of the ESO UVES pipeline. We have designed and implemented an algorithm, which allows us to remove the ripples in regions where Echelle orders are stitched. These ripples are caused by shift of flat-fields and under- or oversubtraction of scattered light. We calculate the offset values using the minimization technique, and apply them to the intermediate data products of the ESO UVES pipeline, which are then fed back to the pipeline. We have also developed an approach to merge 6 UVES spectral chunks divided by gaps in the spectral coverage by using PHOENIX synthetic stellar atmospheres to predict the flux difference between the segments. At the end, we improved the flux calibration quality to 2% or better for 85% of 430 spectra in the library. These algorithms in future can become a part of the public UVES pipeline.
Magnetic field geometry and activity of sun-like stars
Boro Saikia, Sudeshna
Magnetic activity and stellar winds in sun-like stars are known to influence habitability conditions of an orbiting planet. Detailed observations and theoretical models of solar magnetic activity has been carried out in the past few decades. However magnetic field and stellar wind conditions in other Sun-like stars, with different stellar parameters, is not fully known. We investigated the magnetic activity and large-scale magnetic field geometry of 50 Sun-like stars as a function of effective temperature and rotation. The magnetic field geometry information, reconstructed using Zeeman Doppler imaging (ZDI), were taken from the literature. The complexity of the large-scale field and the fraction of poloidal and toroidal field strength is also determined. We show that the large-scale magnetic field of sun-like stars do not exhibit any drastic difference for stars with different effective temperature. On the other hand rotation plays an important role, where strong poloidal field is detected for slowly rotating stars. Our results are important to understand how the magnetic field geometries of sun-like stars can change the stellar wind conditions and affect the atmosphere of an orbiting planet.
The analogy of the K-correction in the topic of gamma-ray bursts
Borvák, Levente
It is well-known that there are two types of gamma-ray bursts (GRBs): short/hard and long/soft ones, respectively. The long GRBs are coupled to supernovae, but the short ones are associated with macronovae (also known as kilonovae), which can also serve as the sources of gravitational waves. Kilonovae occur during the merging of two neutron-stars. The neutron stars can be substituted by more massive black holes as well. Therefore, the topic of gamma-ray bursts (mainly that of short ones) and the topic of massive binaries, are strongly connected. In this contribution, the redshifts of GRBs are studied. The surprising result - namely that the apparently fainter GRBs can be, on average, at smaller distances - is discussed. In essence, the results of Mészáros et al. (2011, A&A, 529, A55) are verified using the newest samples of GRBs.
CO destruction in proto-planetary disk midplanes
Bosman, Arthur
CO has long been thought to be the best mass tracer for proto-planetary disks as it can be easily detected with ALMA in many disks. However, the inferred gas masses from CO in recent ALMAobservations seem to be inconsistent with their inferred dust masses. Inferred gas-to-dust ratios orders of magnitude lower than the ISM value. Herschel measurements of HD imply gas masses in line with gas-to-dust ratios of 100. This suggests that at least one additional mechanism, next to freeze-out andphotodissociation, is removing CO from the gas-phase. We have tested the suggestion that the bulk of the CO is chemically processed and that the carbon is sequester in less volatile species such as, CO2, CH3OH and CH4 in the dense, shielded midplane regions of the disk.Using our gas-grain chemical code we did a parameter exploration and followed the the CO abundanceevolution over a range of conditions representative of disk mid-planes. The impact of the chemical parameters, tunnelling efficiency and diffusion was also studied. A reduction of the total CO abundance by a factor of 10-50 is found at high densities between 15 and 30 K on timescales of 3 Myr assuming an ionisation rate of 10-17 per second. Main reactions are identified. The order of magnitude destruction of CO is robust against the assumption on the chemical parameters between 20 and 30 K. Below 20 K there is a very strong dependence in the CO abundance on the efficiency of H tunnelling.The finding that CO is efficiently destroyed between 20 and 30 K on a 3 Myr timescale is encouraging since most of the 13CO and C18O emission is expected to come from parts of the disk with temperatures within this range.
Where is the metallicity ceiling to form carbon stars?
Boyer, Martha
Carbon stars form easily at low metallicity due to efficient dredge up and a low surface abundance of oxygen that leads o C/O>1 in their atmospheres. At the AGB III meeting in Vienna, we presented a pilot program that targeted the inner disk of M31 and hinted at a metallicity ceiling above which carbon stars cannot easily form. Here, we present new HST observations in M31 that revisit the question of a metallicity ceiling for carbon stars. We targeted 20 fields across the disk, taking advantage of M31's metallicity gradient and diversity in stellar age. The results show a clear effect at the highest metallicity, with a drop in the C/M ratio of more than an order of magnitude from [Fe/H] = -0.2 to [Fe/H] = 0. These observations make use of the medium band filters on WFC3/IR, which are a powerful and efficient tool for identifying carbon stars in distant galaxies by sampling key near-infrared molecular features. To demonstrate the potential of this technique, I will also briefly discuss results from another program that uses the same observing strategy in nearby dwarf galaxies to identify dust-producing AGB stars. Finally, I will discuss how to do similar observations with JWST.
Flexible Variable Star Extractor - new software for semi-automatic variable star detection using CCD photometry
Breus, Vitalii
Over the years of using CCD photometry different techniques for identification of variable stars were developed, from traditional "blinking" and "scatter" searches to more complicated and fully automated solutions. One of the simplest algorithms is based on the dependency of noise level to mean brightness. According to the statistics, if all stars were constant, the dependence of standard deviation of brightness vs. mean brightness of an object would have a parabola-like shape. A variable star should have larger standard error than a constant object of the same mean brightness. However, this solution does not work well when the data is noisy due to different reasons and variable stars would appear in a heap of points at the diagram, and many constant stars with lack of data or outlying points will be located above the curve like they are variables. We developed few simple filters and criteria that allow reducing the impact of outlying points, imaging artifacts and low quality CCD frames without careful manual time series reduction. We implemented various variability detection indices including standard deviation, chi-squared test, median absolute deviation, robust median statistic, normalized excess variance, the von Neumann ratio calculated for final magnitudes obtained using multiple comparison stars method (Kim Y., Andronov I.L., Jeon Y., 2004) instead of classic V-C that allowed us to decrease the influence of the scatter of some particular comparison star on the light curves. As the result, the new software was developed (http://uavso.org.ua/varsearch/). It works with the data exported from C-Munipack. The program chooses the comparison stars automatically, processes all time series to get final light curves and calculates all available variable detection indices. The user-friendly interface allows plotting a two-channel diagram of any pair of indices and mean brightness of the star, choosing there outlying points and reviewing corresponds light curves.
Habitable zones of hot stars
Briot, Danielle
The classical figures of habitable zones versus stellar spectral types generally do not apply to hot stars. The aim of this study is to extend the determination of habitable zone to hot and very hot stars. We know that planets orbiting hot stars are hardly detected. The short life time of those planets does not probably allow very evolved life species. In addition, due to the short wavelength radiation of hot stars, atmospheres of potentially inhabited planets orbiting hot stars must be very opaque to photodissociative processes harmful to biomolecular links. We attempt to identify some possible niches for such life abodes.
Physical parameters of RSGs in the Local Group: probing the nature of dIrr galaxies with RSGs.
Britavskiy, Nikolay
In the last years, the red supergiants (RSGs) deserve particular attention in the studies of the galaxies in the Local Group. Their brightness in the near-IR colors together with a new generation of instruments and telescopes will allow to investigate the properties of host environment even with a non-resolved population of other types of stars. In our previous works (Britavskiy et al. 2014, 2015, in prep.) we identified 25 spectroscopically confirmed RSGs in 7 dwarf irregular (dIrr) galaxies in the Local Group. Namely in Sextans A, Sextans B, WLM, Pegasus, Phoenix, IC 10 and IC 1613. The next step is to characterize and connect the physical properties of RSGs with properties of the host dIrr galaxies. We will make a comprehensive overview of the RSG population and will discuss how to get their physical parameters and evolutionary status by using different methods and models in the different host environments. Moreover, on the other way around, we will make a first estimation of the expected RSG population at the given metallicity and star formation rate of each dIrr galaxy, which will make a bridge between the observed properties of RSGs and the nature of dIrr galaxies.
OJ287: Deciphering the “Rosetta stone of blazars”
Britzen, Silke
OJ287 is the best candidate Active Galactic Nucleus (AGN) for hosting a supermassive binary black hole (SMBBH) at very close separation. We present a re-analysis of 120 Very Long Baseline Array (VLBA) observations (at 15 GHz, MOJAVE survey) covering the time between Apr. 1995 and Apr. 2017. We find that the OJ287 radio jet is precessing on a timescale of ~ 22 yr. In addition, our data are consistent with a jet-axis rotation on a yearly timescale. We model the precession (24±2 yr) and combined motion of jet precession and jet-axis rotation. The jet dynamics and flux-density light curves can be understood in terms of geometrical effects. Disturbances of an accretion disk caused by a plunging black hole do not seem necessary to explain the observed variability. Although the SMBBH model does not seem necessary to explain the observed variability, a SMBBH or Lense-Thirring precession (disk around single black hole) seem to be required to explain the timescale of the precessing motion.
Formation, Processing and Properties of Nano-silicate Dust: A Bottom-up Computional Modelling Approach
Bromley, Stefan
Nanosilicates, although thought to be highly abundant [1], are difficult to characterise by experiment and observation due to their small size and corresponding non-bulk-like properties. We present a complementary approach to understanding the formation, structure and properties of nanosized silicate dust grains based on an atomistic bottom-up computational modelling [2]. Our approach is independent of assumptions based on bulk materials properties, is not limited to any particular chemistry or specific thermodynamic conditions, and provides a solid basis for kinetic modelling.Our approach can provide detailed and quantitative insights in three important areas. First, we provide a realistic account of circumstellar heteromolecular silicate dust formation [3] while highlighting deficiencies in classical nucleation theory accounts based on SiO aggregation [4]. Second, we give insights into the reactivity of nanosilicates with respect to their role as ice condensation nuclei [5,6] and their influence on H2 formation/dissociation [6,7]. Finally, we show how we can explicitly model detailed process of nucleation and growth from molecular precursors (e.g. SiO, Mg, H2O) of nanosilicates with diameters of up to 50 nm. A direct link between our models (with 10s to 1000s of atoms) and observation can be made via computing infrared spectra directly from the atomic vibrational modes in the nanoparticles.[1] Draine, B. T.; Li, A. Astrophys. J. 551 (2001) 807.[2] Bromley, S. T. ; Goumans, T. P. M. ; Herbst, E. ; Jones A. P.; Slater, B. Phys. Chem. Chem. Phys.16 (2014) 18623.[3] Goumans, T. P. M.; Bromley, S. T., Mon. Not. R. Astron. Soc. 420 (2012) 3344.[4] Gomez, J. C.; Plane, J. C.; Bromley, S. T.; Phys. Chem. Chem. Phys. 18 (2016) 26913.[5] Goumans, T. P. M.; Bromley, S. T., Mon. Not. R. Astron. Soc. 414, 1285 (2011).[6] Kerkeni, B; Bacchus-Montabonel, M-C.; Bromley, S. T., Mol. Astrophys. 7, (2017) 1.[7] Kerkeni, B.; Bromley, S T. Mon. Not. R. Astron. Soc. 435 (2013) 1486.
A tale of tails
Brosch, Noah
We present new and archival observations of diffuse, very faint surface brightness features in the multiple galaxy systems NGC5022+NGC5018+MCG-03-34-013, and the Hickson’s Compact Group 098. These consist of optical, near-IR and space-UV imaging and of reprocessed VLA observations. We propose that in the first system we see remains of a disrupted gas-rich dwarf galaxy in the form of ~140 kpc long gas, dust and stars filament, whereas in HCG098 the features represent the remains of a gas-poor dwarf merging with the two brighter galaxies of the group while producing a 170 kpc halo and a 150 kpc long tail. These observations and their interpretation shed light on the issue of dwarf galaxy accretion to build up more massive galaxies.
To Be or Not to Be: EHB Stars and AGB Stars
Brown, David
The formation and lives of EHB stars are linked to the lives of AGB stars by indications that such EHB/sdB stars might form in globular clusters with multiple populations (D’Antona et al., 2005) linked to AGB evolution. Various scenarios have been proposed by which EHBs may form. Binary hypotheses (Mengel, Norris & Gross 1976) posit that they form from the interaction of stars in a binary system via mass transfer, leaving either an EHB binary or a single EHB star, the result of a merger between two He WD stars (Han et al., 2002, 2003). Single star formation scenarios invoke either high stellar winds during the RGB phase of evolution (D’Cruz et al. 1996) before the He-flash, or a delayed He-flash after rapid mass loss (Sweigart 1997), or even mass loss during the HB phase itself (Yong et al. 2000). More recently, observations of multiple subpopulations in massive globular clusters (Piotto et al., 2005), such as ?-Centauri (Bedin et al., 2004), along with the detection of a Na-O anti-correlation (Carretta et al., 2006), suggest that single EHB stars might form from He-enhanced progenitors (D’Antona et al., 2005, 2008; Lee et al., 2005) in environments enriched by AGB ejecta. This scenario is one to be considered given the disparity in EHB/sdB binary fraction between the Galactic field (f~2/3; Maxted et al., 2001) and in globular clusters (f?0.04-0.14; Moni Bidin et al., 2011). The studies conducted by Han et al. (2002, 2003, 2007) have been able to provide a strong case for the binary formation of EHB/sdB stars in the Galactic field, but more work must be done to investigate how EHB stars, possibly in binaries, might be able to form in globular clusters. The results of simulations presented here are an extension of the simulations of Han et al. (2002, 2003), done for Z=0.02, to a diverse range of metallicities in order to see how binary channels in chemically diverse environments might contribute to the overall EHB population in globular clusters.
Modelling the viscous decretion discs of Be/X-ray binaries
Brown, Rory
Be/X-ray binaries are the largest observable population of HMXBs, making them a valuable tool for probing the physics of binary systems and compact objects. Even though there are well over 100 Be/neutron star binaries, there is only one confirmed Be/black hole binary. Previous theoretical work suggests this is not due to their formation but due to differences in X-ray luminosity. We use Smoothed Particle Hydrodynamics simulations to explore the differences between binaries with compact objects of varying mass. It is evident from these models that Be/X-ray binaries with black hole companions are harder to observe. These simulations are also applied to a specific case in Be/neutron star binaries, where the neutron star plunges directly through the disc, that leads to uncommon observational behaviours.
The spectral energy distributions of quasars
Brown, Michael
We present spectral energy distributions of quasars spanning from 0.1 to 35 microns, which can be used for photometric redshifts, k-corrections and modelling object selection. AGN photometric redshifts will be critical for key science with square kilometre array pathfinders and LOFAR, as many of the sources detected by these wide-field surveys won’t have spectroscopic redshifts. Our templates incorporate (but are not limited to) photometry and spectroscopy from FUSE, IUE, Hubble, SDSS, PanSTARRS, Skyampper, IRTF, GNIRS, XShooter, Akari, Spitzer and WISE. Our templates have higher spectral resolution and include spectral features that are often absent from quasar templates from the prior literature. We illustrate the utility of these templates by using them to generate photometric redshifts for AGNs in the Bootes field.
The discovery of an asymmetric detached shell around the "fresh" carbon AGB star TX Psc
Brunner, Magdalena
We present ALMA observations of the circumstellar envelope around the carbon AGB star TX Psc in molecular CO(2-1) emission, where we detect a previously not classified detached shell with filamentary structure and elliptical shape. Detached shells are in theory created through intense mass-loss episodes triggered by thermal pulses, where the mass-loss rate and wind velocity increases for a short period of time (typically a few 100 years). Up to now, all observed detached shells are found around carbon AGB stars and are of remarkable spherical symmetry. The elliptical shell around TX Psc is the first clear exception to that rule, with TX Psc being classified as rather "fresh" carbon star, that most likely has only experienced very few thermal pulses yet.The ALMA observations of molecular gas are consistent with Herschel/PACS observations of thermal dust emission, and the elliptical shape of the shell is almost certainly not caused by interaction with the surrounding interstellar medium, since a clear interaction front is visible in the Herschel/PACS images at slightly larger spatial scales, and the morphology of the present-day wind affirms the intrinsic ellipticity of the shell.We investigate and discuss the 3D structure of the CSE and its most likely formation scenarios, as well as the link of this peculiar detached shell to the AGB evolutionary status of TX Psc.
Herschel and the invisible end of the rainbow
Brunner, Magdalena
We present an overview on our latest science communication project on the discovery of the infrared radiation. This public outreach project is linked to a previous scientific project, focusing on the data analysis and processing of data taken by the Herschel space telescope, operating in the infrared. The Herschel space telescope is named after William Herschel, who discovered the infrared radiation in 1800 together with his sister Caroline Herschel, while trying to determine the detailed energy output of the sun in optical spectra, created through a simple prism. During the experiment, he placed multiple thermometers at different locations in the spectrum, to measure the energy output in the form of temperature increase. By chance, he placed the thermometer for comparative background temperature measurement in the area of infrared radiation of the spectrum, where no optical light could be perceived by eye.The thermometer measuring the infrared radiation proved to provide the biggest temperature increase, leading to Herschel following up on this discovery and realising that this invisible radiation still followed the classical optical behaviour of the visible light.Today, the realm of infrared radiation is not only an important one when it comes to study thermal emission from astrophysical objects, but also has countless major applications in daily life.With the presented science communication project, we will share these insights on the discovery and scientific as well as public application of the infrared radiation with the broad public by means of workshops, easily accessible and redistributable experiments, a short theatre production, an audio production, podcasts and a webpage. This project is a collaboration between several different groups of interest of the University of Vienna and associated public outreach partners.
The USNO-UKIRT K-Band Hemisphere Survey.
Bruursema, Justice
We introduce and present the status of the United States Naval Observatory (USNO) and UKIRT K-band Hemisphere Survey, currently underway using the Wide Field Camera (WFCAM) installed on UKIRT on Maunakea. This survey is a collaborative effort undertaken by USNO, the Institute for Astronomy, University of Hawaii, the Cambridge Astronomy Survey Unit (CASU), and the Wide Field Astronomy Unit (WFAU) in Edinburgh. In addition to the K-band survey, we hope to obtain H-band imaging for the same area. The principal objective of these surveys is to provide continuous northern hemisphere K- and H-band coverage over a declination range from δ=0° to +60° by combining over 12,700 deg2 of new imaging with the existing UKIRT Infrared Deep Sky Survey (UKIDSS), Large Area Survey (LAS), Galactic Plane Survey (GPS) and Galactic Cluster Survey (GCS). The expected 5-σ point source sensitivity is K~18.4 mag and H~18.9 mag (Vega); over three magnitudes deeper than the Two Micron All Sky Survey (2MASS). The combined survey data are meant to complement and combine with the recently obtained J-band UKIRT Hemisphere Survey (UHS) as well as complement the southern hemisphere VISTA Hemisphere Survey (VHS). In this contribution we discuss survey design, data acquisition and processing, calibration and quality control, and the current progress of the observations. The data obtained by these surveys will be made publicly available through the Wide Field Science Archive (WSA) maintained by the WFAU.
Modeling Low Mass Stellar Populations
Bruzual, Gustavo
Modeling low mass stellar populations, like clusters and dwarf galaxies, with population synthesis models requires that we evaluate the role played by stochastic fluctuations in the sampling of the IMF on the spectro-photometric properties of these sparse populations. Interacting binaries may also modify the integrated spectra of these systems depending on the final product of the binary interaction and on the frequency of binary stars. In this work we compare the relative importance of stochastic fluctuations and binary evolution on low mass galaxy properties as a function of the stellar IMF, population age, metallicity, and binary fraction. In most cases the effects of stochastic fluctuations dominate those produced by binary interactions. We explore and quantify the relative importance of these effects through cosmic times.
State of the Art Population Synthesis Models
Bruzual, Gustavo
We present state of the art population synthesis models that improve on the following aspects with respect to most available models. (a) Treatment of the UV spectral range, including new evolutionary tracks and updated treatment of the ionizing radiation emitted by the stellar population, including a new treatment of P-AGB evolution and emission spectra. (b) Improved treatment of TP-AGB stars that dominate the NIR spectral range. The number of these stars present in a stellar population has been calibrated carefully by comparison with observations of the LMC/SMC, and the spectra assigned to these stars include both the stellar emission and the emission from circumstellar dust. (c) Definition of new diagnostics to characterize the combined stellar and nebular emission and the cold ISM in galaxies. Models are available in a wide range of metallicity, from Z = 0 to Z = 0.06, and are ready to use to interpret the spectra of galaxies of any age at low and high redshift.
Far-Infrared Observations of the Circumnuclear Disk
Bryant, Aaron
At the centre of our galaxy lies a 3 x 10 M? supermassive black hole, Sgr A*. Surrounding this is a rich astrophysical laboratory of molecular clouds, dust concentrations and star clusters, a region with significantly raised ISM densities, magnetic fields, turbulences and other environmental effects. It is hence a paradox of youth that there also exists a population of massive young stars within 1 pc of the black hole, grouped into at least 2 rotating disks, subject to raised tidal forces that would normally inhibit star formation.Among the theories explaining the origin of this nuclear stellar cluster is that of a collision between two molecular cloud complexes, close to Sgr A*, enabling accretion at densities above the Roche limit. An obvious candidate for such a collision is the Circumnuclear Disk (CND), a clumpy ring of molecular gas surrounding Sgr A*, with an inner radius of ~1.5 pc and a mini-spiral of ionized gas flowing towards the black hole. However, various parameters of the CND remain unconstrained. Individual gas clumps have been characterized with a range of densities and temperature components, hence raising the question of whether these clumps are transient, or if they can surpass the Roche limit and survive to form stars in-situ. While the source of far-infrared excitation is believed to be the O/B stars of the nuclear stellar cluster, the effect of local heating and shocks cannot be ruled out.In order to attempt to address these open questions, we observed the CND at 10 far-infrared wavelengths with the Field Imaging Far-Infrared Line Spectrometer (FIFI-LS), aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). In this work we present selected fine-structure line flux and thermal continuum maps of the CND, and by modelling it as a PDR, derive its density and susceptibility to tidal forces. We also outline dynamical properties of the cold gas, and present a model explaining these features.
Wind production in active galactic nuclei
Bu, Defu
Observations of both Low-luminosity AGNs (LLAGNs) and Quasars show that wind is present. The accretion model for LLAGNs is hot accretion flow. I will talk about theory and numerical simulations of wind generation of hot accretion flow. In hot accretion flow, wind can be either magnetically or thermally driven. In the region inside the Bondi radius, wind can be driven by the combination of magnetic pressure gradient, gas pressure gradient and centrifugal forces. In the region around and outside Bondi radius, the flow is irradiated and heated by the central X-ray photons and wind can be thermally driven. I will also talk about theory and simulations of wind generated from Quasars. The accretion model for Quasar is standard thin disk. Wind can be either radiation pressure or magnetic driven in standard thin disk. The possible application of wind in AGN feedback study is also discussed.
A Comparison Study of LFQPOs in Neutron-Star and Black-Hole Low-Mass X-ray Binaries
Bu, Qingcui
We studied comparatively the properties of low-frequency quasi-periodic oscillations (QPO) in a sample of fourteen black-hole and four neutron-star low mass X-ray binaries observed by the Rossi X-ray Timing Explorer satellite. We examined the similarities between these two classes of systems in terms of the FWHM - frequency correlation of QPO fundamentals and harmonics. We find that the fundamentals and the harmonics of black holes are consistent with a frequency modulation, while the harmonics of neutron star systems suggests amplitude modulation. We also studied all the sources from our sample in the aperiodic variability amplitude - frequency diagrams. We find that systems with lower source luminosity are likely to have a higher total variability amplitude. We further use these diagrams to constrain the inclination for unknown-inclination neutron star sources.
Exploring the Role of Dwarf Galaxies at High Redshift through JWST NIRSpec+NIRCam Instrument Team GTO Observations
Bunker, Andrew
I will discuss the prospects for studying dwarf galaxies at high redshift with the James Webb Space Telescope (JWST). Since the initial discovery in 2003 of galaxies at z>6 (within the first billion years) using the Hubble Space Telescope and the Lyman break technique, it has become clear that the rest-frame UV luminosity function (LF) has a much steeper faint-end slope at high redshift than in the more recent past, and hence the fainter but more numerous galaxies dominate the UV photon production of the Universe. Faint galaxies below our current detection limits with Hubble may be responsible for reionzing the universe - although this calculation depends critically on the escape fraction of ionizing photons (which is currently unconstrained). JWST will revolutionise our understanding, by probing significantly fainter to better determine the LF faint end slope, and observing out to 5microns with NIRCam & NIRSpec to sample the rest-frame optical out to z~10. This will enable the stellar mass function to be determined as well as the rest-UV LF. Our JWST Advanced Deep Extragalactic Survey (JADES) is a joint program of the JWST/NIRCam and NIRSpec Guaranteed Time Observations (GTO) teams involving 950 hours of observation targetting the CANDELS GOODS-North and South fields (including the Ultra Deep Field). The deepest NIRCam images are 50ksec in 9 filters (from 0.9-4.5microns) and will cover ~46square arcmin down to AB~31mag (5sigma), with multi-object NIRSpec spectroscopic follow-up of 100ksec in the low-dispersion R=100 mode (1-5 microns) and observations at higher spectral resolution (R=1000 and 2700). Emission line ratios will determine extinction, metallicity, ionization parameter and the escape fraction of ionizing photons (by comparing the Balmer recombination lines with the rest-frame UV). Understanding the contribution of line emission will enable stellar population fits to the multi-wavelength photometry of dwarf galaxies at z>6 for the first time.
JWST Advanced Deep Extragalactic Survey (JADES) by the NIRSpec & NIRCam GTO instrument teams
Bunker, Andrew
I will present the JWST Advanced Deep Extragalactic Survey (JADES), a joint program of the JWST/NIRCam and NIRSpec Guaranteed Time Observations (GTO) teams involving 950 hours of observation, including a contribution from the GTO team of G. Rieke. We will target two well-studied fields with excellent supporting data (e.g. from HST-CANDELS): GOODS-North and South, including the Ultra Deep Field. The science goal of JADES is to chart galaxy evolution at z>2, and potentially out to z>10, using the rest-frame optical and near-IR though observations from 1-5microns. Multi-colour NIRCam imaging with 9 filters will enable deriving photometric redshifts and the application of the Lyman break technique out to unprecedented distances and magnitudes. NIRSpec multi-object spectroscopy (MOS) will measure secure spectroscopic redshifts of the photometrically-selected population, as well as stellar continuum slopes in the UV rest-frame, exploring the role of dust, stellar population age, and other effects. Measuring emission lines can constrain the dust extinction, star formation rates, metallicity, chemical abundances, ionization and excitation mechanism in high redshift galaxies. Coupling NIRCam and NIRSpec observations will determine stellar populations (age, star formation histories, abundances) of galaxies and provide the information to correct their broad-band spectral energy distribution for likely line contamination. Potentially we can search for signatures of Population III stars such as HeII. We will study the evolution of galaxy sizes and the luminosity function based on these spectroscopic redshifts, and determine the stellar mass density and star formation rate density over a wide range of redshifts. We can address the contribution of star-forming galaxies at z>7 to reionization by determining the faint end slope of the luminosity function and investigating the escape fraction of ionizing photons by comparing the UV stellar continuum with the Balmer line fluxes.
Optical identifications of high-redshift galaxy clusters from Planck Sunyaev-Zeldovich survey
Burenin, Rodion
We present the results of optical identifications and spectroscopic redshifts measurements for galaxy clusters from 2-nd \emph{Planck} catalogue of Sunyaev-Zeldovich sources (\emph{PSZ2}), located at high redshifts, $z\approx0.7$--$0.9$. We used the data of optical observations obtained with Russian-Turkish 1.5-m telescope (RTT150), Sayan observatory 1.6-m telescope, Calar Alto 3.5-m telescope and 6-m SAO RAS telescope (Bolshoi Teleskop Alt-azimutalnyi, BTA). Spectroscopic redshift measurements were obtained for seven galaxy clusters, including one cluster, PSZ2\,G$126.57\!+\!51.61$, from the cosmological sample of \emph{PSZ2} catalogue. In central regions of two clusters, PSZ2\,G$069.39\!+\!68.05$ and PSZ2\,G$087.39\!-\!34.58$, the strong gravitationally lensed background galaxies are found, one of them at redshift $z=4.262$. The data presented below roughly double the number of known galaxy clusters in the second \emph{Planck} catalogue of Sunyaev-Zeldovich sources at high redshifts, $z\approx0.8$.
Transfer and loss of water in hit-and-run collisions during late-stage planet formation
Burger, Christoph
Collision events between large, similar-sized bodies shape the final characteristics of (terrestrial) planets. Volatile material like water is particularly prone to collisional loss processes, due to its volatile nature, but also because it is preferentially found in the outer layers of colliding bodies. We studied transfer, loss and processing of water in collisions between planetary embryos in the late stages of planet formation, focusing on the peculiarities of hit-and-run collisions. This additional outcome regime emerges in rather grazing encounters between roughly similar-sized bodies and is characterized by two large post-collision objects, originating mainly from the two pre-collision bodies respectively. Besides the common figure of overall water loss, transfer between the two colliding bodies as well as their individual losses have to be considered in hit-and-run encounters._x005F For disentangling these effects we ran a suite of multi-material Smooth Particle Hydrodynamics (SPH) simulations including self-gravity, with varying impact velocity, impact angle and projectile-to-target mass ratio over the full range of reasonable values. We find overall water losses of up to 75% in the most energetic impacts, and much greater effects for the smaller body, which is often stripped of a large fraction of its volatiles while the larger body remains relatively unaltered. Therefore the cumulative effect of a sequence of such collisions can be expected to greatly reduce water contents of growing planets._x005F To additionally study the amount of water vapor production in connection to potential further losses of water vapor atmosphere, we also varied the total colliding mass. Results indicate that these additional losses are particularly important in collisions of ~Mars-sized embryos, where vapor production is already significant, but their gravity to prevent atmospheric losses is still weak.
The Athena WFI Science Products Module
Burrows, David
The Science Products Module (SPM), a US contribution to the Athena Wide Field Imager, is a highly capable secondary CPU that performs special processing on the science data stream. The SPM will have access to both accepted X-ray events packets and those that were rejected by the on-board event recognition processing. It will include two software modules. The Transient Analysis Module will perform on-board processing of the science images to identify and characterize variability of the prime target and/or detection of serendipitous transient X-ray sources in the field of view. The Background Analysis Module will perform more sophisticated flagging of potential background events as well as improved background characterization, making use of data that are not telemetered to the ground, to provide improved background maps and spectra. We will present the preliminary design of the SPM hardware as well as an overview of the software algorithms under development.
MopraCO – the CO Southern Galactic Plane Survey
Burton, Michael
The Mopra CO survey of the southern Galactic Plane (MopraCO) covers ~115°x2°, extending from Galactic longitude l = +257° – +11_x005F° and latitude b = ±1°_x005F. These data have been taken at 0.6 arcminute spatial resolution and 0.1 km/s spectral resolution, providing an unprecedented view of the molecular clouds and gas of the southern Galactic Plane in the 109–115 GHz J = 1–0 transitions of 12CO, 13CO and C18O.The data is being released in a series of papers (Burton et al 2013, Braiding et al 2015, Braiding et al 2018) in longitude ranges, plus selected regions of interest (Rebolledo et al 2016 for Carina, Blackwell et al 2018 for the Central Molecular Zone). The final survey fields will be taken during the 2018 austral winter.We present a series of velocity-integrated maps, spectra and position-velocity plots that illustrate Galactic arm structures and trace masses on the order of _x005F106 Msun per square degree. These data will be available from the Mopra CO website (www.phys.unsw.edu.au/mopraco/) and the PASA data store.
Spin evolution of supermassive black holes in simulations of galaxy formation
Bustamante, Sebastian
Supermassive black holes (SMBHs) at the center of galaxies grow their mass through two different channels: gas accretion and BH-BH coalescence. These processes lead not only to an increase of the mass, but also modify the spin of the SMBHs, which in turn, affects the accretion power that regulates star formation and gas cooling in the host galaxy. Thus, modelling the spin is an important step to better understand the co-evolution of BHs and their host galaxies. Spin evolution in the context of galaxy formation has been previously investigated mostly through post-processing approaches, with only few studies using self-consistent on-the-fly models. The latter is a necessary consideration to properly capture the effects on the radiative efficiency and the accretion power. In this work, we implement in the N-body, magneto- hydrodynamics code AREPO, a semi-analytical model of spin evolution coupled to the numerical output for the mass accretion rate and the angular momentum of accreted gas. The model assumes a geometrically thin warped alpha-disc which accretes mass and angular momentum from the surrounding gas. Addiontally, we propose a parametrisation for the fueling process, going from chaotic to coherent accretion. We have run a set of cosmological simulations with different configurations of these models. This allow us to quantify the impact of the gas angular momentum on BH spin evolution, which ultimately influences the BH population, BH mass scaling relations and galaxy morphology through BH feedback.
X-ray Reverberation from Black Hole accretion discs in Active Galactic Nuclei
Caballero-Garcia, Maria D.
X-ray reverberation mapping is a valuable technique for knowing the physical condition of the accreting black holes and the matter that surrounds them. Its potential grows also with the ongoing preparations of Athena mission as the large collecting area will be ideal for reverberation studies of AGNs. KYNREFREV is a widely used reverberation modelling tool for fitting X-ray lag spectra. Our main goal is to make fundamental improvements to our KYNREFREV model and use that improved model for time-lag spectra analysis of selected AGNs to constrain their corona geometries. In this talk we present our recent results obtained from the analysis of a sample of AGN in the context of the reverberation-nature interpretation of the X-ray soft-lags in the lamp-post geometry and provide some clues into future expected developments of the code based on our results.
Exoplanet phase curves at large phase angles.
Cabrera, Juan
At optical wavelengths, Titan's brightness for large Sun-Titan-observer phase angles significantly exceeds its dayside brightness. The brightening that occurs near back-illumination is due to moderately large haze particles in the moon's extended atmosphere that forward scatters the incident sunlight. Motivated by this phenomenon, here we investigate the forward scattering from currently known exoplanets, its diagnostics possibilities, the observational requirements to resolve it and potential implications. An analytical expression is derived for the amount of starlight forward scattered by an exponential atmosphere that takes into account the finite angular size of the star. We use this expression to tentatively estimate how prevalent this phenomenon may be. Based on numerical calculations that consider exoplanet visibility, we identify numerous planets with predicted out-of-transit forward-scattering signals of up to tens of parts per million provided that aerosols of ?1 µm size form over an extended vertical region near the optical radius level. We propose that the interpretation of available optical phase curves should be revised to constrain the strength of this phenomenon that might provide insight into aerosol scale heights and particle sizes. For the relatively general atmospheres considered here, forward scattering reduces the transmission-only transit depth by typically less than the equivalent to a scale height. For short-period exoplanets, the finite angular size of the star severely affects the amount of radiation scattered towards the observer at mid-transit.
WFC3/HST photometric calibration: color terms for the UV filters
Calamida, Annalisa
The two detectors of the Hubble Space Telescope Wide Field Camera 3 (WFC3) instrument, UVIS1 and UVIS2, have different quantum efficiencies, with the difference being larger in the ultra-violet regime. The two detectors' sensitivities also change differently with time, resulting in different count rate ratios as a function of the observing epoch for UVIS1 and UVIS2. Starting from 2016, a chip-dependent calibration was implemented by the WFC3 calibration pipeline, and new set of values for UVIS1 and UVIS2 inverse sensitivities were provided. The new chip-dependent inverse sensitivities were calculated by using photometry of three CALSPEC standard white dwarfs. However, for cooler (T < 20,000 K) and redder stars, the inverse sensitivities of the two WFC3 detectors are still different. I will present corrections to the inverse sensitivities of UVIS1 and UVIS2 for three ultra-violet filters, namely F218W, F225W, and F275W. These were derived by using multi-band observations of the globular cluster Omega Centauri and synthetic photometry for 72 CALSPEC standards. The corrections are provided as look-up tables as a function of stellar color and are available to WFC3 users.
Photometry and spectroscopy of a new set of faint spectrophotometric standard white dwarfs
Calamida, Annalisa
We present precise optical and near-infrared photometry and spectroscopy for 23 candidate spectrophotometric standard white dwarfs. The selected stars are homogeneously distributed in the Northern hemisphere and are all fainter than V ~ 16.5 mag. These network of stars, when established as standards, together with the three Hubble Space Telescope CALSPEC white dwarfs, will provide a set of spectrophotometric standards to directly calibrate data products from future surveys, such as LSST, Pan-STARRS, the Dark Energy Survey, JWST, WFIRST, to better than 1% accuracy. The new faint standard white dwarfs will have enough signal to noise in these photometric surveys to be measured accurately while they will avoid saturation.
Understanding the complex chemistry of solar-type protostars
Calcutt, Hannah
Complex organic molecules have been detected in every environment associated with star formation. Their detection is critical to understanding the chemical development of star-forming regions, as well as exploring the link between the early stages of star formation and the formation of Solar System bodies. Of particular interest to such studies is the detection of complex organic molecules containing nitrogen, owing to the significance nitrogen plays in the formation of life. Abundances of complex nitrogen-bearing organics have also been observed to vary significantly in different star forming regions, with this chemical differentiation even suggested as a tracer of protostellar evolution. With uncertain formation routes, however, and differing physical conditions between sources, the exact origin of this differentiation remains unclear. In this work, we present results from a survey of complex nitrogen-bearing organics towards the low-mass protostellar binary IRAS 16293-2422. We use ALMA observations from the Protostellar Interferometric Line Survey (PILS), to study nitrogen chemistry at an unprecedented spectral and spatial resolution in this source. We will present the key constraints this survey has placed on the formation routes for a number of molecules in this source, as well as constraints on luminosity, physical structure, and evolution.
Computation of Perturbations in Warm Inflation
Calderón, Jaime
This project looks at two different methods used to compute the curvature power spectrum in the Warm Inflation scenario. Each method is discussed in order to find the reason behind some discrepancies between them. Then, the apparent reason is pointed out, and a solution is presented by making use of the gauge invariance principle of General Relativity. Furthermore, we explore the differences by considering a quadratic and a quartic potential, with field-dependent and temperature-dependent dissipative coefficients. Moreover, a hypothetical thermal nature of the inflaton and gravitons is considered in the analysis, which resulted in an enhancement factor for the tensor perturbations yielding results not compatible with observations. Finally, in order to settle the inconsistencies for good, we repeat the analysis by using the equations of motion of the magnitudes involved in the inflationary dynamics, but in their gauge invariant form instead.
MOS spectroscopy of a z= 6.5 proto-cluster candidate galaxies
Calvi, Rosa
Galaxy clusters are the most massive gravitationally bound structures in the universe. They form in regions of enhanced dark matter density. The distribution of those structures at different redshifts tell us how the primordial density fluctuations evolve in a given cosmology. Hence, the detection of proto-clusters at very high-z sets important constraints on the cosmological models in use. We show the results of two runs of multi-object spectroscopic observations of the subset of candidate LAEs sources at z=6.5 that we could fit in one OSIRIS/GTC mask: the imaging observations, including the observing strategy, the data reduction and its analysis.
The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES): First Results
Cami, Jan
The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES) is Large Programmethat is collecting high-signal-to-noise (S/N) spectra of a large sample of O and B-type starscovering a large spectral range using the UVES spectrograph mounted on the Very LargeTelescope (VLT). The goal of the programme is to extract a unique sample of high-qualityinterstellar spectra from these data that represent different physical and chemical environments,and to characterise these environments in great detail. An important component of interstellarspectra are the diffuse interstellar bands (DIBs), a set of hundreds of unidentified interstellarabsorption lines that are commonly found in the spectra of reddened targets. With the detailedline-of-sight information derived from these high-quality spectra, EDIBLES will derive strongconstraints on the potential DIB carrier molecules. EDIBLES will thus guide the laboratoryexperiments necessary to identify these interstellar "mystery molecules", and will turn theDIBs into powerful diagnostics of their environments in our Milky Way Galaxy and beyond.Here, we will present some of our first results showing the unique capabilities of the EDIBLESprogramme.
Structure of meteoroids producing double-peaked light curves
Campbell-Brown, Margaret
The structure of small meteoroids (in the millimeter size range) can provide important information about their parent asteroids and comets. Faint meteors normally have symmetric light curves, but a small percentage of meteors show two distinct peaks. The Canadian Automated Meteor Observatory (CAMO) can resolve details of ablating meteors at meter scales. Of twenty-five observed double peaked light curves, all but one showed a single ablating object with very little wake. This is in contrast to the majority of CAMO meteors, of which 90% show long wakes or distinct fragments indicative of the shedding of significant mass in fragments. This contradicts the current model of double peaked light curves (Roberts et al., 2014), in which two separate fragmentation events are responsible for the two peaks.Roberts, I., Hawkes, R., Weryk, R. et al., 2014. Proceedings of Meteoroids 2013, Poznan, Poland, AM University Press, 155.
Communicating Astronomy with the Public 2018: efforts on bringing together the international astronomy communication community
Canas, Lina
Communicating Astronomy with the Public (CAP) Conferences series providesan open platform to exchange opinions and experiences regarding the latestchallenges in communicating astronomy with the public. Seeing CAP as an idealopportunity to bring the international astronomy community to Japan and todirectly experience the most recent national and Asian advances in the field,the National Astronomical Observatory of Japan (NAOJ) and Fukuoka City,continuing the efforts made in the past years in Astronomy communication inthecountry, embarked on a journey to host CAP 2018 edition in Japan.The organization wanted to give something back and contribute to amore significant percentage of Asian participants in the CAP bydirectly supporting young participants from Asia-Pacific countries andby having a national organizing committee that disseminated CAP conferencethroughout Japan, increasing national participation. The relationsestablished between different national and international stakeholdersinvolved in outreach and astronomy communication increased the visibility,reach and interest of the international community in participating in themeeting. Maximizing the overall participant experience by using the potentialof providing a unique cultural intake that Japan has to offer and how it canbroaden horizons and extend it to a valuable professional experience.As language barrier is still a divide to the internationalization ofmany Asian programs, CAP 2018 was presented with all the benefitsa face-to-face meeting can provide: strengthening relations and meeting newprofessionals in astronomy communication from Japan and the Asian community.CAP 2018 edition is one of the most diverse and largest CAP conferences everorganized and the work carried by the Local Organization on planning andimplementing, framing it in the Asia-Pacific context, focusing on the needsof the region and creating a chance to make a difference in Astronomycommunication for years to come.
IAU and the Public: IAU Office for Astronomy Outreach (OAO) Communications
Canas, Lina
The IAU OAO communications comprehend a set of ongoing tasks that contribute to the IAU direct interaction with the public. Its primary goal is to support the current outreach activities around the world by disseminating, promoting and encouraging outreach-related activities from and to the IAU. Examples of these tasks are managing the IAU Public Enquiries and FAQs, the IAU Social Media, the IAU Astronomy Outreach Newsletter, and the IAU Themes.The IAU OAO is in charge of answering public enquiries for IAU-related affairs, via email and IAU Social Media channels (Facebook and Twitter), thus allowing the IAU to build a dedicated dialogue with the public by using direct channels such as emailing, messaging, commenting, tweeting or retweeting. The IAU Social Media intends to promote public awareness of the IAU activities by sharing upcoming IAU conferences and symposia, information about the IAU Scientific Bodies activities, and updates from the IAU Office of Astronomy for Development (OAD) and the IAU OAO. The IAU Astronomy Outreach Newsletter is a community generated digital publication curated by the IAU OAO team to improve community building and disseminate commendable efforts, such as astronomy outreach and education activities and resources around the world. The IAU Themes featured on the IAU website, encompass the most popular topics related to astronomy and the IAU, triggered by the most frequently asked questions (FAQs) that the IAU has received over the years. The IAU OAO utilizes a set of digital platforms and their data analysis tools to manage the content and community response. How data is gathered from the different tools available, the importance of indicators and their subsequent analysis, are steps considered for each of these channels in order to maximize our audience reach, influencing the overall communications strategy of an organization such as the IAU.
OBSERVATION OF 44 (NYSA) ASTEROID BY IST60 TELESCOPE
Canbay, Remziye
In this study, the main-belt asteroid 44 (Nysa), which is also a known member of the Nysian asteroid family, was observed by ist60 telescope. The orbital elements were compared with MPO and NASA Horizons Web-Interface results and a light curve was created.
Imaging Red Supergiants with VLT/SPHERE/ZIMPOL
Cannon, Emily
In the red supergiant (RSG) phase of evolution massive stars show powerful stellar winds, which strongly influence the supernova progenitor properties and control the nature of the compact object that is left behind. Material that is lost in the stellar wind, together with that ejected in the final core collapse, contributes to the chemical enrichment of the local interstellar medium. The mass-loss properties of RSGs are however poorly constrained. Moreover, little is known about the wind driving mechanism. To provide better constraints on both mass-loss rates and physics, high angular resolution observations are needed to unveil the inner regions of the circumstellar environment, where the mass loss is triggered.Using the VLT-SPHERE/ZIMPOL adaptive optics imaging polarimeter, spatially resolved images of a small sample of nearby RSGs were obtained in multiple filters. From these data, we obtain information on geometrical structures in the inner wind, the onset radius and spatial distribution of dust grains, and dust properties such as grain size. As dust grains may play a role in initiating and/or driving the outflow, this could provide us with clues as to the wind driving mechanism.
Why are only a small fraction of quasars radio-loud?
Cao, Xinwu
It is still a mystery why only a small fraction of active galactic nuclei (AGNs) contain relativistic jets. A strong magnetic field is a necessary ingredient for jet formation, however, the advection of the external field in a geometrically thin disk is inefficient. Gas with a small angular velocity may fall from the Bondi radius {R}{{B}} nearly freely to the circularization radius {R}{{c}}, and a thin accretion disk is formed within {R}{{c}}. We suggest that the external magnetic field is substantially enhanced in this region, and the magnetic field at {R}{{c}} can be sufficiently strong to drive outflows from the disk if the angular velocity of the gas is low at {R}{{B}}. The magnetic field is efficiently dragged in the disk, because most angular momentum of the disk is removed by the outflows that lead to a significantly high radial velocity. The strong magnetic field formed in this way may accelerate jets in the region near the black hole, either by the Blandford-Payne or/and Blandford-Znajek mechanisms. We suggest that the radio dichotomy of AGNs predominantly originates from the angular velocity of the circumnuclear gas. An AGN will appear as a radio-loud (RL) one if the angular velocity of the circumnuclear gas is lower than a critical value at the Bondi radius, otherwise, it will appear as a radio-quiet (RQ) AGN. This is supported by the observations that RL nuclei are invariably hosted by core galaxies. Our model suggests that the mass growth of the black holes in RL quasars is much faster than that in RQ quasars with the same luminosity, which is consistent with the fact that the massive black holes in RL quasars are systematically a few times heavier than those in their RQ counterparts.
Jet production in black-hole X-ray binaries and AGN: mass feeding and advection of magnetic fields
Cao, Xinwu
Relativistic Jets are observed only in the low/hard and intermediate states of X-ray binaries (XRBs), and are switched off in the thermal state, but they appear to be present in both low-luminosity and luminous active galactic nuclei (AGNs). It is widely believed that strong large-scale magnetic fields is a crucial ingredient in jet production; such fields can be attained only through efficient advection from the outer disc. We suggest that geometrically thin accretion discs with magnetic outflows are present in luminous radio-loud AGNs; this is likely because the interstellar medium provides both mass and sufficient magnetic flux to the outer disc. Most angular momentum of such disc is removed by the outflows, and the radial velocity of the disc is significantly increased compared to viscous drift velocity. This facilitates efficient magnetic field advection through the disc to produce a strong field near the black hole in luminous AGNs, which helps launch relativistic jets. In XRBs, the magnetic fields of the gas from companion stars are too weak to drive outflows from outer discs. Jets are therefore switched off in the thermal state due to inefficient magnetic field advection in the disc.
The hydrodynamic evolution of the gas content in the dSph galaxy Ursa Minor induced by the feedback from types Ia and II supernovae
Caproni, Anderson
Dwarf spheroidal galaxies (dSph) of the Local Group share a similar characteristic nowadays: a very low amount of gas in their interiors. How these galaxies lost their gas contents during their evolution remains a matter of debate in the literature. In this work, we present results from a three-dimensional hydrodynamical simulation of the gas inside an object with similar characteristics of the classical dSph galaxy Ursa Minor. We evolved the initial galactic gas distribution over 3 Gyr, considering the effects of the types Ia and II supernovae, as well as a cored, static dark-matter gravitational potential. The instantaneous supernovae rates were derived from a chemical evolution model applied to spectroscopic data of the Ursa Minor galaxy. Our numerical simulation shows that the amount of gas that is lost due to supernovae feedback varies with time and galactocentric radius. The highest gas-loss rates occurred during the first 600 Myr of evolution. Our results also indicate that types Ia and II supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and probably in other similar dwarf galaxies), removing a fraction of at least 60 percent of the initial gas mass inside its tidal radius.
Study of cavities geometry for absolute radiometer
Carlesso, Franciele
The measurement of the Total Solar Irradiance (TSI) and its variations are very important to understand the influence of Sun’s radiant output on the Earth’s climate. Space-borne instruments have made TSI measurements continually and allowed advances in the TSI understanding. These measurements rely on active cavity radiometers, which use black interior surfaces to absorb incident sunlight. Black Ni-P was firstly applied in active cavity radiometers for measuring solar irradiance in TIM (Total Irradiance Monitor) instrument [1]. The development of an absolute radiometer is currently been done at INPE. We obtained black Ni-P by electroless deposition for application in the interior of the silver cavities. We used bidirectional reflectance distribution function (BRDF) data to describe the surface reflectance properties of the Ni-P film. The BRDF data were used in the geometry study of the absorber cavity in a ray tracing software - ZEMAX. These measures allowed cavities geometries optimization considering the characteristics of the black Ni-P produced at INPE. We intend to use this cavity in a bench prototype radiometer under development. The current status of the study and obtained results are presented in detail.[1] G. Kopp, Journal of Space Weather and Space Climate, 4, A14 (2014).
The Impact of Dust/Gas Ratios on Chromospheric Activity in Red Giant and Supergiant Stars
Carpenter, Ken
Stencel et al. (1986) analyzed IUE spectra of a modest sample of cool stars and found that such objects continue to produce chromospheres even in the presence of high dust levels in the outer part of their atmospheres. This reversed the previous results of Jennings (1973) and Jennings & Dyck (1972). We present here an extension of the Stencel et al. study to a larger sample of stars representing a broader range in dust/gas ratios, using archival IUE and HST data on both RGB and AGB stars. Surface fluxes in emission lines will be used to assess the chromospheric activity and obscuration by dust in each star, as those fluxes will follow a different pattern for reduced activity (temperature/density dependent) vs. dust obscuration (wavelength dependent). The goal is to assess the applicability of the Stencel et al. conclusions in a larger and more diverse sample of stars.
Unsupervised photometric galaxy clustering: Analysis of Euclid and DES bands with UPMASK
Carvalho, Ana
Galaxy Clusters are essential objects to study galaxy evolution as well as the dark sector of the universe. However, one of the biggest challenges of this study is to know which galaxies belong to the cluster and which galaxies are field galaxies, using the less possible ammount of a priori information on what a cluster is and not knowing the precision and accuracy of the individual distance of each galaxy. UPMASK, or Unsupervised Photometric Membership Assignment in Stellar Clusters, is a method created to study star clusters, when the distance is not known or poorly determined. This method uses heuristics and statistical analysis to separate a cluster from the field, without any basis on theoretical models, and consequently without strong a priori statements, of what a cluster is made of. It operates with minimal information from astrometry and photometry. In this poster we will show the results of a modified version of UPMASK optimized to study galaxy clusters. We present our findings about the potential of applying the UPMASK to the study of galaxy clusters without prior knowledge about their galaxy redshift or model distributions. We test the method using simulations that include the luminosity bands of DES and the forthcoming ESA/Euclid space mission.
The mass and light distributions in groups and superclusters of galaxies
Castejon Molina, Mirian
Through mass map reconstruction from weak gravitational lensing it is possible to recover the matter distribution of the large scale structure from measurements of galaxy shapes. This technique offers the possibility of detecting and probing mass concentrations by their gravitational effect on the rays of light coming from distant galaxies only, without relying on simplifying physical assumptions about the nature of that mass, making it a direct probe of dark matter. Those dark matter maps allow the determination of cosmological parameters and the identification of structures, such as groups, clusters and superclusters of galaxies. Mass maps are also particularly important to study the connection between dark and baryonic matter, through mass-to-luminosity ratio maps in diverse environments.The goal of this study is to investigate the relationships between peaks in mass and luminosity maps to understand the nature of substructures in superclusters of galaxies, and the mass distribution of fossil groups (those in which the central galaxy dominates the overall group luminosity).For this study we use CFHT images of five fossil galaxy groups in two bands (g, r) and Subaru observations of two galaxy superclusters in z~0.4 from Las Campanas Distant Cluster Survey (LCDCS) in four bands (g,r,i,z), both with excellent depth and quality.
Molecular gas reservoirs in Low Luminosity Radio Galaxies at z~0.4-2.6 in dense Mpc-scale environment
Castignani, Gianluca
At variance with powerful radio galaxies (RGs) Low Luminosity Radio Galaxies (LLRGs) represent the bulk of the RG population and are often associated with the brightest cluster galaxies (BCGs). LLRGs are in fact a precious tool to discover distant (proto-)clusters and can be effectively used to probe the effect of dense Mpc-scale environment on molecular gas, even close to the AGN. Molecular gas has never been searched for in the host galaxies of distant LLRGs, which show lower level of AGN activity and therefore resemble better normal galaxies than powerful RGs. We search for CO in a sample of five distant LLRGs, at z=0.4, 0.6, 0.9, 0.9, and 2.6, within the SDSS (at z<=0.6) and COSMOS (at z>=0.9) surveys. The LLRGs are detected at 24μm by Spitzer/WISE, which suggests significant ongoing star formation activity. Evidence of dense Mpc-scale environment is found for all five LLRGs by looking for overdensities of photometric redshifts around them. The two LLRGs at z=0.9 from COSMOS are also hosted in rich X-ray groups. By exploiting IRAM-30m telescope observations and assuming a Galactic CO-to-H2 conversion we set SNR=3 upper limits M(H2)<2e+09 Msun to the total molecular gas content associated with each of the four z<=0.9 LLRGs. Tentative SNR=2.3 detection of CO(7-6) is found for the remaining z=2.6 LLRG, corresponding to M(H2)=2e+10Msun. If the detection is confirmed at higher SNR with better sensitivity observations (e.g., NOEMA, ALMA) such z=2.6 LLRG would be the most distant proto-BCG ever detected in CO. Our observations suggest that highly star forming BCGs are rare. Our LLRGs are optimal targets for NOEMA/ALMA to distinguish between gas processing mechanisms occurring in distant BCGs such as gas stripping, cooling flows, or major mergers.
Galaxy And Mass Assembly: Bulge-disk decomposition of KiDS and VIKING data in the nearby universe
Casura, Sarah
Obtaining reliable structural parameters for the different components of galaxies is important for a wide variety of studies of galaxy properties and evolution. I will present our current work on the bulge-disk decomposition of around 13000 GAMA galaxies in the nearby universe (z<0.08) in all 9 optical and near-infrared bands covered by KiDS and VIKING. The galaxy profiling itself uses the 2-dimensional Bayesian profile fitting code ProFit (Robotham et al. 2016) while the preparatory work (image segmentation/source identification, sky subtraction, initial parameter estimates) is carried out using the sister package ProFound (Robotham et al. 2018). The local PSF is estimated using a combination of ProFound and ProFit to identify stars near the galaxy of interest and fit them with a Moffat function. These decompositions will be used to derive the stellar mass functions of bulges and disks and study the nature and distribution of dust in galaxy disks.
Extended parameter study of the self-similar relativistic MHD equations for black hole outflows
Ceccobello, Chiara
Jets are ubiquitous and reveal themselves at different scales and redshifts, showing an extreme diversity in energetics, shapes and emission, in objects such as X-ray binaries (XRBs) and active galactic nuclei (AGN), as well as young stellar objects (YSOs) and gamma-ray bursts (GRBs). Observations suggest that jets are an energetically important component, not only to the systems that host them, but also their larger surrounding environments, where they deposit a significant amount of energy that has been extracted from the accretion flow. Therefore, understanding the mechanisms responsible for the formation and emission of jets is a fundamental problem to be addressed. In this talk, I will present a new integration scheme to solve scale-invariant, relativistic and non-relativistic MHD equations describing collimated Blandford-Payne outflows.For the first time, jet solutions can be reconstructed from the disk mid-plane to downstream of the modified magnetosonic fast point, while smoothly crossing the three singular surfaces (modified slow/fast and Alfven surfaces).Relativistic solutions show a wide range of jet dynamics (jet Lorentz factor ~ 1-10) and geometric properties (i.e. shock height ~ 10^3 - 10^7 Rg), which is even more broadened by the inclusion of the non-relativistic solutions grid. Such diversity makes our model suitable for application to many different systems in which relativistic jets are launched.
Analytical solution for magnetized thin accretion disk in comparison with numerical simulations
Cemeljic, Miljenko
A magnetic extension of hydrodynamical solution for a thin accretion disk around a central star is obtained by using the method of asymptotic approximation. For the first time we add the energy equation in the asymptotic approximation. We compare the analytical results with the long-lasting resistive and viscous MHD axi-symmetric numerical simulations of the quasi-stationary disk.
New calibration of the Vilnius photometric system
Cepas, Vytautas
The medium-band seven-color Vilnius photometric system for many years was an important tool to determine interstellar reddenings and distances of single stars due to its ability to recognize stars of different spectral types in the presence of different interstellar reddenings. The Gaia mission now allows to determine distances of stars with much better accuracy at least up to 1 kpc. However, multicolor photometry, which allows the classification of stars as well as the determination of stellar temperatures, gravities, metallicities and interstellar reddenings, remains an important method for distant stars. Here we present a semi-empirical calibration of color indices of the Vilnius photometric system in terms of physical parameters of stars, taking into account that many new spectroscopic investigations were published recently. The calibration is based on photoelectric color indices of more than 2000 stars with known effective temperatures, Gaia distances, gravities and metallicities. The physical parameters of stars (Teff, logg, [Fe/H]) were sampled from several sources. We also use the stellar atmosphere models ATLAS to calculate synthetic color indices of stars of spectral types and luminosities which are not covered by photometric observations. Finally, we present the new code for the classification of stars observed in the Vilnius system. Keywords: techniques: photometric – Vilnius photometric system - stars: parameters
A New Method to Derive Star Formation Histories in Dwarf Galaxies
Ceponis, Marius
A new method to determine star formation histories of stellar systems, like dwarf galaxies, is presented. The method uses multicolour stellar photometry data of resolved stellar populations. Star formation histories are determined by comparing observed populations with artificially generated ones based on star counts in binned colour-magnitude diagrams. Parameters of synthetic populations are adjusted iteratively to match observations. 2D star formation distributions are acquired by summing-up Bayesian probabilities of stars to belong to various populations. The method has been extensively tested with synthetic galaxies and applied to recover 1D and 2D star formation history of young (t < 500 Myr) stellar populations in the dwarf irregular galaxy Leo A.
Metallic Line Doubling in the Spectra of the Variable R Scuti Star
chafouai, khadija
We conducted an observation campaign of the brightest and the most irregular RV Tauri star R Scuti. This observation campaign spanned over 26 days from June to November 2016 at the observatory in thehigh Atlas Mountains, at an altitude of 2700 m, in Morocco. The instrument set up includes two telescopes mounted on each other. For spectroscopy, a C14 was used along with an eShel spectrograph. Forphotometry, ASA 10 N was used with a QSI CCD camera were used with various color filters (U-B- V). High resolution spectra (R ˜ 12 000) obtained between 4289 Å and 7125 Å. In this work, we present theobservation of line doubling absorption in the spectra of the R Scuti variable star on the metal lines of FeI (?6546.245 Å, 6569,224 Å and ?6750.146 Å), and Ti II(?5188.7Å) around the phases ? = 1.18 and ? =1.70. We observed the splitting in the form of broadening of lines on the Ti I (?5866.46Å) in the same phases. This metal lines show two transitions, from the red component to the blue component and vice versa.
Non-Zeeman Circular Polarization of Molecular Spectral Lines in the ISM
Chamma, Mohammed
We searched archival data of the Submillimeter Array (SMA) for evidence of circular polarization in common molecular tracers, most notably CO. This circular polarization possibly arises from anisotropic resonant scattering (ARS) whereby background linear polarization signals are converted to circular polarization, as indicated by observations of Orion KL taken with the Caltech Submillimeter Observatory and of the supernova remnant IC443 taken with the IRAM 30m. We find circular polarization in NGC7538, IRC+10216 and Orion KL for transitions of CO, SiO and SiS to levels high enough to suggest that the presence of circular polarization in these spectral lines is widespread for such objects, and that the conversion of linear-to-circular polarization is common. This implies that measuring circular polarization is an important step when studying magnetic fields through the linear polarization of molecular spectral lines in the interstellar medium.
Raman and Thomson Wings around Balmer Lines in the Two S-Type Symbiotic Stars Z Andromedae and AG Draconis
Chang, Seok-Jun
Symbiotic stars are binary systems composed of a hot white dwarf and a mass losing giant. Broad wings around Balmer emission lines are found in many symbiotic stars including the two S-type symbiotic stars, Z Andromedae and AG Draconis. Monte-Carlo simulations are carried out to produce Balmer wings from Thomson scattering with free electrons and Raman scattering with atomic hydrogen. Thomson wings of Ha and Hß have the same widths in the Doppler space due to the cross section independent of wavelength. In contrast, Raman Ha wings are 3 times broader widths than Hß counterparts, which is attributed to the different cross sections and branching ratios. The half width at half maximum (HWHM) is proportional to Te1/2 for Thomson wings and NHI1/2 for Raman scattering. We present our spectra of Z And and AG Dra obtained with the Canada-France-Hawaii Telescope, where Ha wings are found to be broader than Hß wings indicative of significant contribution of Raman scattering to the formation of the Balmer wings.
The role of environment on the star formation history of disc galaxies
Chang, Ruixiang
NGC 2403, NGC 300 and M33 are three nearby pure-disc galaxies with similar stellar mass in different environments; they are benchmarks for understanding late-type spiral galaxies in different environments. The chemical evolution and growth of their discs are investigated by using the simple chemical evolution model, in which their discs are assumed to originate and grow through the accretion of the primordial gas, and the gas outflow process is also taken into account. Through a comparative study of the best-fitting model-predicted star formation histories for them, we hope to derive a picture of the local environment on the evolution and star formation histories of galaxies and whether or not the isolated galaxies follow similar evolution history. Our results show that these three galaxies accumulated more than 50 per cent of their stellar mass at z < 1. It can also be found that the metallicity gradients in isolated spiral galaxies NGC 2403 and NGC 300 are similar and obviously steeper than that in M33, when the metallicity gradients are expressed in dex R_25^{-1}. The similar metallicity gradients in NGC 2403 and NGC 300 indicate that they may experience similar chemical evolutionary histories. The principal epoch of star formation on the discs of NGC 2403 and NGC 300 is earlier than that on the disc of M33, and the mean age of stellar populations along the discs of both NGC 2403 and NGC 300 is larger than that of M33. Our results indicate that the evolution and star formation history of a galaxy indeed depend on its local environment, at least for galaxies with stellar mass of 10^{9.2}-10^{9.7} M_{?}.
The Spin-Rate Limits and the General Shape Distributions of Asteroid Families
Chang, Chan-Kao
Through a general survey of asteroid rotation, we can study the interior structure of a group of asteroid. For instance, the bulk density of an asteroid family can be estimated through their spin-rate limit and their general shape distribution are related to the strength of their interior structure. Although this kind of study is important, it was relatively untouched area in the last decade due to the difficulty in collecting asteroid light curves. However, with the advance of observation technology and computational ability, it is no longer impossible to collect a great number of asteroid light curves within a short period of time. Using the PTF (a wide-field time-series survey project), we have delivered more than 15,000 rotation periods of asteroids, and expect an order of magnitude more using the ZTF (the successor of the PTF with an upgraded camera of 47 square deg). Therefore, we are now able to conduct the aforementioned study more comprehensively and hope to bring a new aspect into asteroid family study.
Inflow-Outflow in the magnetosphere of a black hole
Chantry, Loic
The jets produced by AGN are extremely energetic natural phenomena and thus constitute a real laboratory of high energy physics. To describe the inner-spine jet of AGN in the context of ideal, stationary and axial-symetric MHD, we build a meridional self-similar model in Kerr metric. The choice of this metric is justified in order to describe the flow near the super-massive central black hole, and in particular to study the effects of its rotation. The model, characterized by 8 parameters, is based on a first order expansion of the governing general relativistic equations in the magnetic flux function around the symmetry axis of the system. The geometry of the self-similar solutions is not fixed in advance and is determined by transversal forces balance. These models takes into account the light cylinder effects.This complete treatment for an outflow in a Kerr metric allowed us to present four enthalpy driven solutions with different field geometries and Lorentz factors, wherein the contribution of the Poynting flux is rather small. The jet power and magnetic flux of the ultra-relativistic outflow solutions are of the same order as those determined from numerical simulations conducted by several groups.Furthermore, our model is able to describe both an incoming and outgoing flow at the level of the stagnation radius; at this radius, pairs are created from neutrinos or highly energetic photons coming from the disk. Coupling inflow and outflow models allows us to describe the MHD flow from the horizon of the black hole up to infinity. We can estimate the different energetic contributions of each of those processes: at the black hole level the energetic component coming from the Blandford-Znajek effect or the generalized Penrose mechanism, and the energetic input due to the creation of pairs. We discuss an ensemble of inflow solutions, emphasing features and topology for the magnetic field in the vicinity of the black hole.
Bayesian estimation and prediction of redshift-independent extragalactic distance errors
Chaparro, Germán
We present a methodology for estimating and predicting extragalactic distance errors in multi-measurement catalogs. Our estimation of errors is based on using well performing robust measures of the variance of the posterior distribution of extragalactic distance for individual galaxies. We apply those measures to the bootstrap sampled distribution that emerges when considering many distance estimations for individual galaxies with different distance determination methods. We create error data tables for galaxies in the Cosmiflows-3, HyperLEDA, and NED-D redshift-independent distance catalogs. Additionally, we are able to learn the systematics of the errors for distance determination with the TF relation and use this to create a Bayesian predictive model validated using a Bayesian p-value based on the Freeman-Tukey discrepancy measure. We use this model to predict missing/non-reported distance errors from the NED-D and HyperLEDA catalogs. Errors estimated or predicted in this work should be used in catalog-wide precision cosmology studies that require a full consideration of the true uncertainty of redshift-independent extragalactic distance determination.
Paths to a 30m+ Radio Telescope in Colombia
Chaparro, Germán
I will present current perspectives on the development of a 30m+ radio telescope in Colombia. One is the project of antenna conversion of two 32 m Intelsat-A dish antennas in Chocontá Earth Station belonging to the Telefónica telecommunications company. The second is a probabilistic approach to site testing for a millimeter-wave telescope based on legacy climate data and satellite imagery.
Equation of State of Quark Matter with Density Dependent B-parameter of anisotropic Strange Stars.
Chattopadhyay, Pradip Kumar
A class of relativistic solutions for compact cold stars with strange matter in a pseudo-spheroidal space-time is presented here. Considering strange matter equation of state namely, $p = \frac{1}{3}(\rho-4B)$, where $\rho$, $p$ and $B$ are energy density, pressure and MIT Bag parameter respectively, stellar models are obtained. In the presence of anisotropy with a pseudo-spheroidal geometry described by Vaidya-Tikekar metric stellar models are explored, where the Bag parameter varies with the energy density ($\rho$) inside the compact object. We determine the density dependence of $B$ for different anisotropy including isotropic case. It is noted that although $B$ varies with anisotropy inside the star, finally at the surface it attains a value which is independent of the anisotropy. The Bag parameter $B$ is found to increase with an increase in anisotropy for a given compactness factor $(M/b)$ and spheroidicity ($\lambda$). It is also noted that for a star with given mass and radius, the parameter $B$ increases with the increase of $\lambda$ and finally at large value of $\lambda$ it attains a constant value. We note that in this model equation of state (EoS) obtained from geometrical consideration with allowable value of ‘B’ is similar to that obtained by earlier investigators from consideration of micro-physics. The stability of the stellar models for compact stars with anisotropy in hydro-static equilibrium is also studied.
Maximum Mass of Relativistic Anisotropic Star in Higher Dimensions
Chattopadhyay, Pradip Kumar
A class of relativistic solutions of cold compact anisotropic stars in hydro-static equilibrium in the framework of higher dimensions using spheroidal geometry is investigated here. The solutions obtained with Vaidya-Tikekar metric are used to construct stellar models of compact objects and studied their physical features. The effects of anisotropy and extra dimensions on the global properties namely, compactness, mass, radius, equation of state are determined in terms of the spheroidicity parameter ($\lambda$). It is noted that for a given configuration, compactness of a star is found smaller in higher dimensions compared to that in four space-time dimensions. It is also noted that the maximum mass of compact objects increases with the increase of space-time dimensions (D) which however attains a maximum value when D = 5 for any spheroidicity parameter ($\lambda$), thereafter it decreases as one increases the number of extra dimensions (D). The effect of extra dimensions on anisotropy is also studied.
Generating magnetograms from Ca II K observations for irradiance reconstructions since the early 20th century
Chatzistergos, Theodosios
Models of irradiance reconstruction rely on data providing information about the evolution of the surface magnetism of the Sun. Magnetograms of the Sun are well suited for that purpose, however they exist for almost the same period as the direct measurements of irradiance.Full-disc observations made in the Ca II K line can potentially be used to reconstruct magnetograms since the early 20th century due to the corresponence of bright regions in Ca II K observations and magnetically strong regions found in magnetograms.Such a relation has been investigated by many studies, reporting however disparate results.Here we examine the relation between the magnetic field strength and the Ca II K emission with high-quality full-disc and near co-temporal SDO/HMI magnetograms and Rome PSPT Ca II K observations. These observations span half a solar cycle, enabling us to study the relation for different features and positions on the disc, as well as effects of solar activity on the relation.This obtained relation is then used to reconstruct unsigned magnetograms from the PSPT observations, which we can use to directly estimate the accuracy of the conversion.
Populations of accreting white dwarfs
Chen, Hai-Liang
Accreting white dwarfs are important for studies of SNe Ia, X-ray and UV emission of elliptical galaxies and nova population. We have modelled the formation and evolution of populations of accreting white dwarfs in different types of galaxies. I will show the results of X-ray and UV emission from accreting white dwarfs in elliptical galaxies and comparison of our results with observations of Chandra, SDSS . Moreover, I will talk about the properties of nova population in different types of galaxies.
Chemical reactions in interstellar medium
Chen, Tao
Polycyclic aromatic hydrocarbon (PAH) molecules are an important component of the interstellar medium (ISM) locking up ~10% of the elemental carbon. Understanding their characteristics and their dependence on local physical conditions is crucial in astrophysics._x005F Interstellar PAHs are assumed to form in processes akin to soot formation in the cooling ejecta of carbon-rich Red Giant stars as they flow from the stellar photosphere into the ISM. Subsequently, they are further processed for millions of years by photons of the interstellar radiation field. Driven by this astrophysical interest, large number of experiments and theoretical studies focusing on the reactions of PAHs have attracted much interest in recent years. Different processes are investigated, varying from sequential fragmentation, isomerization, ionization and molecular growth processes. Dedicated studies of the involved dissociation channels provide information on the molecular dynamics at play and this is interesting, both from an astronomical and physical chemical point of view. Particularly processes changing the nature of the carbon skeleton have been the topic of recent studies. In photodissociation regions in space, (large) PAHs (with more than 50 C-atoms) are considered starting points in the formation of other species, including fullerenes, carbon cages and smaller hydrocarbon chains. PAHs with functional side groups may also be important. Inside molecular clouds, PAHs are expected to be trapped in low temperatures (∼10 K) ice mantles, consisting mainly of H2O with traces of CH3OH, CO2, CO, and NH3. Photolysis of these complex ice mixtures is known to functionalize PAHs with alcohol, ketone, amino, methyl, methoxy, cyano/isocyano, and carboxyl groups, which is crucial for formation of complex organic molecules and enrichment of the molecular inventory in space. _x005F In this work, we review the recent experimental and theoretical studies on chemical reactions of the interstellar PAHs.
Variable dust in the inner disk of a Herbig Ae star spatially resolved by infrared interferometry
Chen, Lei
An essential step to understanding the evolution of protoplanetary disks is the study of objects that contain gaps or inner holes. The pre-transitional disk around the Herbig star HD 169142 exhibits multi-gap disk structure, differentiated gas and dust distribution, planet candidates, which make it a valuable target for a case study of disk evolution. An especially interesting phenomenon in the HD 169142 system is a fading at near-infrared wavelengths, which suggests that the inner sub-au dust is dissipating on an exceptionally short time scale of <= 10 years. Using near-infrared interferometric observations with VLTI/PIONIER, we studied the inner dust, constraining both its radial location and the dust grain size in the years 2011-2013, when the object was already in its near-infrared faint state. The observations with high spatial resolution of ?/B ~ 2 mas constrain the radial location of inner dust to be ~ 0.08 au from the central star. Combining the spatial information with radiative transfer modeling, we find the observations best interpreted with optically thin gray dust, with grain size larger than 1 micron. This information on grain size provides a hint of dust grain growth in this late-stage protoplanetary disk. However, an alternative model with optically thick dust, in which smaller grains are possible, is also discussed.While the near-infrared fading of the object happened on a time scale much shorter than the lifetime of a protoplanetary disk, we speculate that this fading is part of a series of flux fluctuations due to a combination of unsteady dust replenishing and short-term dust dissipation. We are carrying on follow-up studies of the object, aiming at constraining the dust properties at multiple epochs, in order to further reveal the mechanisms behind the near-infrared variability. Here, I report our study using PIONIER observations and I will also present some results from our latest follow-up measurements.
NIR interferometric observation of DG Tau with VLTI/AMBER: evidence of temporally varying obscuration
Chen, Lei
DG is a T Tauri star showing multi-wavelength variability from the optical to MIR. Using the near-infrared interferometor VLTI/AMBER, we studied the spatial structure of the object in near-infrared. A large part of K-band light are found to arise from outside of 0.5 au from the central star, suggesting an origin as scattered light instead of warm emission. This differs from a typical young star, in which the K-band light is dominated by direct stellar light and the warm emission from the disk rim, while scattered stellar light contributes only a small fraction (<20%). The K-band visibilities measured by our observations are dramatically lower than previous results from Keck Interferometor, suggesting that the object was experiencing changes in brightness distribution. We propose a scenario that the central star is obscured by temporally varying material. With this scenario we attempt to self-consistently interpret several phenomena: the high fraction of scattered light, the changes in brightness distribution, and the multi-wavelength variability.
Constraints on Estimation of Radius of Double Pulsar PSR J0737-3039A and Its Neutron Star Nuclear Matter Composition
Chen, Li
The aspect of formation and evolution of the recycled pulsar(PSR J0737-3039 A/B) is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram(– diagram) in the double pulsar system. Accepting the spin-down age as a rough estimate(or often an upper limit) of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.
The formation of WR+O systems in the SMC
Chen, Wang
Wolf-Rayed (WR) stars are Hydrogen deficient on top and believed to be the late evolutionary phase of massive stars. It is proposed that binary evolution should play a vital role in the formation of WR stars in the SMC due to weak stellar wind. However observations give a similar fraction of single WR stars and WR binaries in the SMC. There are twelve WR stars observed and five of them are in binaries. Among them AB8 is the only observed WO type star. In this work we explore the formation channel for three WR binary systems AB3, AB7 and especially AB8 using MESA. We estimate tens of thousands of binary models and try to find out the probable progenitors for these WR binaries. We check the influence of semi-convection, stellar wind and binary interaction. We compare the observations with our theoretical models using least square method and Bayesian analysis. We find that all of these three WR binaries can be reproduced with our current models. They will experience non-conservative mass transfer. For AB8, we prefer efficient semi-convection that can extend He burning lifetime and can extend the convective core during He burning phase. These will help to expose Carbon and Oxygen on top. Besides we also need to increase the commonly adopted stellar wind mass loss rate during WR phase in the stellar evolutionary code in order to reproduce AB8. We found that the reproduction of the normal WN stars AB3 and AB7 are insensitive to the adopted semi-convection parameter and the stellar wind.
Magnetic Field Alignment in Massive Protoclusters
Chen, Vivien
The influence of magnetic fields on dynamics and timescales of star formation remains an open question. The alignment of magnetic field with respect to mass accretion flow renders greatly different expectation for gas kinematics. Polarized emission arising from magnetically aligned dust grains in the mm/sub-mm wavebands is often used to map the 2D morphology of the 3D magnetic fields on the plane of sky. Although a pinched field morphology aligned with the outflow axis has been reported in a few massive porto-clusters, it remains unclear whether these cases well represent the rich diversity of forming clusters. As part of the SMA polarization legacy project, we have observed the polarized dust emission at 882um in the nearby (1.83 kpc) massive protocluster W3 IRS5 with an angular resolution of 2.7” (~5000 AU). W3 IRS 5 is a luminous proto-cluster with at least eight hyper-compact HII regions and makes a much younger analogue to the Trapezium system. Our polarization maps show a pinched morphology while the CO emission suggests two pairs of bipolar outflows. We have developed radiative transfer models to interpret the observed polarized dust emission. We are able to reproduce observed polarization pattern with a misaligned hourglass geometry of magnetic field. This suggests that the magnetic field does not necessarily remain well-aligned at scales of cluster formation. Comparison with the case of G240.31+0.07, which displays a well-aligned field morphology, will also be discussed.
Generating high-resolution anharmonic infrared spectrum with ab initio molecular dynamics simulations
Chen, Tao
As our knowledge on interstellar PAHs results mainly from infrared (IR) observations, much effort has been expended over the last three decades on determining IR spectra of PAHs and their dependence on the molecular characteristics. This has led to much insight in the characteristics of PAHs in space, including the importance of the PAH charge state and of the molecular edge structure. Conversely, this has been used to determine the physical conditions in the regions from which the PAH emission originates. Yet, the Near Infrared Spectrograph and the Mid-Infrared Instrument instruments on board of the James Webb Space Telescope (JWST) - to be launched in early 2019 - will open up the mid-IR spectral range to systematic studies of PAHs at high spectral resolution and this has great potential as a probe of the characteristics of the emitting PAHs and the physical conditions in ISM. Unfortunately, due to the difficulties in experiments, reliable and accurate laboratory spectra are missing, especially for the astrophysically relevant PAHs (50-100 C-atom). On the other hand, due to the low computational efficiency and intrinsic limitations of the algorithm, current quantum chemical calculations are not suitable for generating high resolution IR spectra of large PAHs. Therefore, in order to make progress in this area and to fully exploit the data to be expected from JWST, new and innovative method for generating high-resolution IR spectra of astrophysically relevant PAHs are urgently needed! In this work, ab initio molecular dynamics (AIMD) is introduced to study the spectroscopic signatures of astrophysically relevant species and their dependence on the molecular structures. AIMD is an efficient and versatile method that incorporates the anharmonic effects, ro-vibrational couplings and temperature effects in a natural way. This method allows for the first time a realistic simulation of the high-resolution anharmonic spectrum of PAHs with astrophysically relevant sizes.
Multi-channel Photometric Survey Telescope – Mephisto
CHEN, BINGQIU
Large-scale astronomical surveys have become a key in modern astrophysical studies, leading to new discoveries, and revolutionising our understandings about the origin and evolution of the Universe. The fast technological advances are changing the ways we view the sky, from snapshot taking by e.g., SDSS, to movie shooting by observing the same sky thousands of times in surveys, such as LSST. These developments open the possibility for us to probe the Universe from multiple dimensions. Based on the experiences of these surveys and make a step forward, we will build the first wide-field multi-channel ground-based telescope in the world, the Multi-channel Photometric Survey Telescope -Mephisto. Mephisto is designed to have a 1.6 m primary mirror and a 3.14 deg^2 field of view. It will be equipped with three CCD cameras, with a total of 1.4 Giga pixels. It will be able to image the sky in three filters (ugi or vrz) simultaneously. The goal of Mephisto is to yield real-time high-quality colours of astronomical objects with superb astrometric and photometric accuracies, and deliver for the first time a coloured movie of our Universe. Mephisto surveys will consist of two parts: the Northern ~26,000 deg^2 multi-channel photometric survey (Mephisto-W) and the multi-channel surveys of variables and transients with various cadences of time intervals from days to minutes (Mephisto-D, Mephisto-H and Mephisto-M). The unique feature of the real-time recording in multi-channels over large sky areas makes Mephisto extremely valuable in astrophysical studies, ranging from planets to cosmic structures.
Imaging the low frequency sky from a lunar orbit Interferometer
Chen, Xuelei
A lunar orbit radio interferometer array can observe the sky at very low frequency without being hampered by the refraction and absorption of the ionosphere, and the radio frequency interference (RFI)from the Earth could be shielded by the moon. However, for such array the usual synthesis imaging algorithm is not applicable: the field of view is very wide. and for each baseline, the Moon blocks part of the sky, but as the satellites orbit the Moon, both the direction of the baseline and the blocked sky change. Here we present an imaging algorithm based on solving the linear mapping equations relating the sky intensity to the visibilities. We show that by employing the natural progression of the oribital plane, the baselines fill a three dimensional space, which is useful in itself for breaking a mirror symmetry present for whole-sky primary beams. The algorithm is applicable and good maps could be reconstructed, even though for each baseline the sky blocking by the Moon is different.
A Study of Fermi-LAT GeV Gamma-Ray Emission toward the Magnetar-harboring Supernova Remnant Kesteven 73 and Its Molecular Environment
Chen, Yang
We report our independent GeV ?-ray study of the young shell-type supernova remnant (SNR) Kes 73, which harbors a central magnetar, and CO-line millimeter observations toward the SNR. Using 7.6 years of Fermi-LAT observation data, we detected an extended ?-ray source (“source A”) with centroid on the west of the SNR, with a significance of 21s in 0.1-300 GeV and an error circle of 5'.4 in angular radius. The ?-ray spectrum cannot be reproduced by a pure leptonic emission or a pure emission from the magnetar, and thus a hadronic emission component is needed. The CO-line observations reveal a molecular cloud (MC) at VLSR ~ 90 km s-1, which demonstrates morphological correspondence with the western boundary of the SNR brightened in multiwavelength. The 12CO (J=2-1)/12CO (J=1-0) ratio in the left (blue) wing 85-88 km s-1 is prominently elevated to ~1.1 along the northwestern boundary, providing kinematic evidence of the SNR-MC interaction. This SNR-MC association yields a kinematic distance 9 kpc to Kes 73. The MC is shown to be capable of accounting for the hadronic ?-ray emission component. The ?-ray spectrum can be interpreted with a pure hadronic emission or a magnetar+hadronic hybrid emission. In the case of pure hadronic emission, the spectral index of the protons is 2.4, very similar to that of the radio-emitting electrons, essentially consistent with the diffusive shock acceleration theory. In the case of magnetar+hadronic hybrid emission, a magnetic field decay rate >~1036 erg s-1 is needed to power the magnetar's curvature radiation.
Optical–Mid-Infrared Period–Luminosity Relations for W UMa-type Contact Binaries Based on Gaia DR 1: 8% Distance Accuracy
Chen, Xiaodian
W Ursa Majoris (W UMa)-type contact binary systems (CBs) are useful sta- tistical distance indicators because of their large numbers. Here, we establish (orbital) period–luminosity relations (PLRs) in 12 optical-to-mid-infrared bands (GBV RIJHKsW1W2W3W4) based on 183 nearby W UMa-type CBs with ac- curate Tycho–Gaia parallaxes. The 1s dispersion of the PLRs decreases from optical to near- and mid-infrared wavelengths. The minimum scatter, 0.16 mag, implies that W UMa-type CBs can be used to recover distances to 7% precision. Applying our newly determined PLRs to 19 open clusters containing W UMa-type CBs demonstrates that the PLR and open cluster CB distance scales are mutu- ally consistent to within 1%. Adopting our PLRs as secondary distance indicators, we compiled a catalog of 55,603 CBs candidates, of which 80% have distance estimates based on a combination of optical, near-, and mid-infrared photometry. Using Fourier decomposition, 27,318 high-probability W UMa-type CBs were selected. The resulting 8% distance accuracy implies that our sam- ple encompasses the largest number of objects with accurate distance within a local volume with a radius of 3 kpc available to date. The distribution of W UMa-type CBs in the Galaxy suggests that in different environments, the CB luminosity function may be different: larger numbers of brighter (longer-period) W UMa-type CBs are found in younger environments.
Forming and evolution history of M31 as revealed from LAMOST M31/M33 survey
CHEN, BINGQIU
Being the largest and most luminous galaxy of the Local Group, M31 hosts a variety of interesting targets including planetary nebulae (PNe), Hii regions, supergiants and globular clusters that are easily detectable with the LAMOST. Kinematic and elemental abundance studies of those objects in M31 provide important information of the chemical composition, kinematics and structure of M31 as well as the surrounding, extremely extended and complex stellar streams revealed by the recent deep imaging surveys, and are thus of great interest for the understanding of the assemblage history of the Local Group. As part of the LAMOST Spectroscopic Survey of the Galactic Anti-center, the LAMOST M31/M33 survey have observed M31, M33 and the vicinity fields, targeting foreground Galactic stars, accessible objects of special interests in M31 and M33, including the M31 bulge and disk, as well as background quasars. Kinematic properties of the M31 bulge and disk, Globular clusters and PNe, as well as the stellar population properties of the M31 bulge, disk and globular clusters are derived from their LAMOST spectra. We obtain the global velocity field and calculate corresponding rotation velocities of M31. The age metallicity distributions show that there are two groups in the halo of M31, one probably formed in situ in the halo in the early epoch of M31 with a rapid process. The second group probably come from disrupted dwarf galaxies accreted by M31 in the past. The bulge of M31 was formed in a early epoch, while the disk is relatively younger and the ages of some regions along the spiral arms can reach as young as less than 1Gyr.
An extremely low mid-infrared extinction law toward the Galactic Center and 4% distance precision to 55 classical Cepheids
Chen, Xiaodian
Distances and extinction values are usually degenerate. To refine the dis- tance to the general Galactic Center region, a carefully determined extinction law (taking into account the prevailing systematic errors) is urgently needed. We collected data for 55 classical Cepheids projected toward the Galactic Center region to derive the near- to mid-infrared extinction law using three different ap- proaches. The relative extinction values obtained are AJ /AKs = 3.005, AH /AKs = 1.717,A[3.6]/AKs = 0.478,A[4.5]/AKs = 0.341,A[5.8]/AKs = 0.234,A[8.0]/AKs = 0.321, AW 1/AKs = 0.506, and AW 2/AKs = 0.340. We also calculated the cor- responding systematic errors. Compared with previous work, we report an ex- tremely low and steep mid-infrared extinction law. Using a seven-passband ‘op- timal distance’ method, we improve the mean distance precision to our sample of 55 Cepheids to 4%. Based on four confirmed Galactic Center Cepheids, a solar Galactocentric distance of R0 = 8.1 ± 0.1 ± 0.2 kpc is determined, which is close to the limiting distance accuracy (3%) for Galactic Center Cepheids.
The Tianlai 21cm experiment
Chen, Xuelei
The Tianlai 21cm intensity mapping experiment is located in Hongliuxia, Balikun (Barkol) county in Xinjiang, China. Currently there is a cylinder array with three cylinder reflectors, and a dish array with 16 dishes. The aim of the pathfinder is to explore the 21cm observation and data processing techniques, which if successful can map out the large scale structure with high precision and fast speed, and by using the baryon acoustic oscillation features the dark energy equation of state can be constrained. I present the details of the experiment setup, the organization of the Tianlai international collaboration, and the progress of the Tianlai survey.
A search for thermonuclear burst spectral features with NICER
Chenevez, Jerome
Neutron stars are collapsed objects produced by supernova explosions of massive stars. They compress more than the Sun’s mass into a city-size volume, exhibiting some of the highest densities, spin rates, temperatures and magnetic fields that we can witness in the Universe. One of the key challenges in current research is the actual measurement of their mass and size ratio.Many neutron stars are observed in X-rays when they gravitationally attract matter from an orbiting stellar companion in a binary system. Type-I X-ray bursts are commonly detected that originate from the unstable thermonuclear burning of the accreted hydrogen and/or helium into heavier elements in the surface layers of neutron stars in low-mass X-ray binaries. The luminosity of the bursts does sometimes exceed the Eddington limit and temporarily drive the photosphere to large radii, which may lead to the ejection of nuclear burning ashes. The heavy elements thus exposed by thermonuclear explosions are supposed to engender absorption features in the X-ray burst spectra.The Neutron star Interior Composition Explorer (NICER) has been mounted on the International Space Station in summer 2017, and has since observed a number of X-ray bursters with both high timing and high energy resolutions. The soft (0.2-12 keV) energy passband of NICER is particularly well-suited for X-ray burst investigations.Detections in NICER burst spectra of photoionization edges from heavy elements are expected to display the thermonuclear burning and mixing processes under degenerate conditions. Moreover, the identification of gravitationally-redshifted edges would uniquely provide a measure of the neutron star compactness, and thus constitute a probe of the ultra-dense matter equation of state.
SCUBA-2 Observations of High-redshift Clusters/Protoclusters of Starbursting Galaxies Selected by Planck and Herschel
Cheng, Tai-An
Crossmatching between Planck and Herschel (HerMES and H-ATLAS surveys) data has revealed a number of candidate high-redshift clusters/protoclusters with starbursting galaxies. These starbursting galaxies are believed to be progenitors of quiescent and elliptical galaxies residing in cores of today's massive galaxy clusters. Hence studies of these starbursting protoclusters and their cluster galaxies are important in understanding the formation of clusters and cluster galaxies. In this talk we will present follow-up observations of 13 of our candidate starbursting protoclusters using SCUBA-2 at 850 micron on the JCMT. Combining other far-infrared instruments, such as Herschel-SPIRE, we have estimated the colours, number counts, photometric redshifts, etc., of these protocluster candidates. We found that these candidates are likely to be protoclusters of starbursting galaxies in their formation periods. Crossmatching with our multi-wavelength follow-up data also reveals their radio and optical/near-infrared properties, such as multiplicity, morphologies, and possible AGNs.
Evolving Models of Stellar Photospheric and Coronal Magnetic Fields
Cheung, Mark
We present results from an ongoing effort to model the evolving photospheric and coronal magnetic fields of cool stars. In this project, we run a series of surface flux transport (SFT) models of starspot evolution. SFT models are used as lower boundary conditions to drive evolving models of stellar coronal magnetic fields. The coronal magnetic fields are modeled by magnetofriction (MF), which allows us to construct force-free coronal fields evolving in response to starspot evolution. The combined SFT/MF simulations are used to synthesize dynamic Stokes spectra to serve as inputs for Zeeman Doppler Imaging (ZDI) inversions. Photometric light curves modulated by starspot evolution and stellar rotation are also synthesized. We report on tests of the validity of ZDI inversions for such models, and examine the correspondence between inferred stellar magnetic properties with the input SFT parameters governing flux emergence, differential rotation and turbulent dispersal. This project is part the Solar-Stellar Connection Focus Science Team funded by NASA's Living With A Star program.
The IAU National Outreach Contact network
Cheung, Sze-leung
The IAU National Outreach Contact (NOCs) networks started back in 2012, it is the structure within the IAU to coordiante worldwide outreach efforts. The network is managed by the IAU Office for Astronomy Outreach (OAO) hosted by the National Astronomical Observatory of Japan (NAOJ).This poster present the latest summary of the NOCs activites in the 80 countries in the NOC network. It form the basis of discussion for the panel discussion at the IAU FM14.
The Standardization Equation and Color Transformation Equation for BVRI & SDSS filter system of KMTNet at CTIO
Chiang, Howoo
In this poster, we present the optical band atmospheric extinction coefficient at CTIO (Cerro Tololo Inter-American Observatory) in 2015. CTIO lies many well-known telescopes while the atmospheric extinction coefficients are not available in online anymore since 2010’s. This observation was done by 1.6m telescope KMTNet (Korea Microlensing Telescope Network) which has both Johnsons-Cousins filters and SDSS filters (BVRI and griz band; KMTNet does not contain U and u band). In the 2015, we observed Landolt standards L95 and analyzed approximately 200 stars in BVRI and griz band and achieved the first order atmospheric extinction coefficients. KMTNet detector is mosaicked with 4 CCDs, providing a plate scale of 0.40 arcsec per pixel and a field of view of 2.0 by 2.0 degree on the sky. Then, we derived the first order standardization equation in the errors of 0.1~0.2 magnitude. We also have estimated the transformation equation between BVRI vs griz band, and compared the data with Johnsons-Cousins vs SDSS photometric system. Although that these results were performed with a single observation, it is notable that this work could fill up the blank data for CTIO observers around 2015.
Using Gaia to measure dynamics in AGB stars
Chiavassa, Andrea
Convection in AGB stars is a difficult process to understand because it is non-local and three-dimensional, and it involves non-linear interactions over many disparate length scales due to the low gravity and corresponding large pressure scale heights. In this context, global numerical hydrodynamical simulations of surface convection carried out with CO5BOLD are essential to a proper and quantitative analysis of the observations. Moreover, a grid of global models of the outer convective envelope and the inner atmosphere of AGB stars is now available (Freytag et al. 2017, A&A, 600, 137). I will present the benefit of the employment of these simulations to produce spectrophotometric and interferometric observables in the framework of next generation instruments (e.g., ESPRESSO@VLT and MATISSE@VLTI).
Diffuse post-starburst galaxies: a smoking gun of UDG formation via ram pressure stripping
Chilingarian, Igor
Ultra-diffuse galaxies (UDGs) is a recently identified galaxy type: they have sizes comparable to the Milky Way and stellar masses of about 1/1000 of it. Ultra-diffuse galaxies (UDGs) attracted a lot of attention as possible "dark galaxies" heavily dominated by dark matter, however, no dynamical mass estimates were done because of their extremely low surface brightness. We have recently found 13 gas free diffuse blue post-starburst (300-500Myr) galaxies without ongoing star formation in Coma and Abell2197, which, should they continue to evolve passively, will become UDGs in 5Gyr. Four of them exhibit tails of ram pressure stripped material visible in deep direct images. We followed up three galaxies spectroscopically with GMOS at the 8-m GEMINI-North telescope and Binospec at the 6.5-m MMT and recovered their major axis kinematics and stellar population properties out to 2 effective radii. All three galaxies show a nearly solid body rotation at moderate amplitudes (30-50 km/s). We performed Jeans axisymmetric modelling and showed that observed M/L ratios are consistent with only 30-50% of dark matter in addition to stars and, therefore, these objects are not "dark galaxies" but are normal intermediate to large-sized discs where the star formation was quenched by the ram pressure stripping.
RCSED – A VALUE-ADDED REFERENCE CATALOG OF SPECTRAL ENERGY DISTRIBUTIONS OF 800,299 GALAXIES IN 11 ULTRAVIOLET, OPTICAL, AND NEAR-INFRARED BANDS: MORPHOLOGIES, COLORS, IONIZED GAS, AND STELLAR POPULATIONS
Chilingarian, Igor
We present the value-added Reference Catalog of Spectral Energy Distributions of galaxies (RCSED),which contains homogenized spectrophotometric data for 800,299 low to intermediate redshift galaxies(0.007 < z < 0.6) selected from the spectroscopic sample of the Sloan Digital Sky Survey. Thecatalog is accessible from the International Virtual Observatory and is complemented with detailedinformation on galaxy properties obtained with the state-of-the-art data analysis. RCSED enablesdirect studies of galaxy formation and evolution during the last 5 Gyr. We provide tabulated colortransformations for galaxies of different morphological types and luminosities and analytic expressionsfor the red sequence shape in different colors. RCSED comprises integrated k-corrected photometryin up-to 11 ultraviolet, optical, and near-infrared bands published by GALEX, SDSS, and UKIDSSwide-field imaging surveys, the results of the stellar population fitting of SDSS spectra including best-fitting templates, velocity dispersions, parametrized star formation histories, and stellar metallicitiescomputed for instantaneous starburst and exponentially declining star formation histories, parametricand non-parametric emission line profiles and fluxes, and gas phase metallicities. The catalog alsoincludes the morphological classification by the Galaxy Zoo citizen science project and the bulge+diskdecomposition of SDSS images by Simard et al. We construct color–magnitude, Faber–Jackson,mass–metallicity relations, compare them with the literature and discuss systematic errors of galaxyproperties presented in our catalog. RCSED is accessible from the project web-site and via VirtualObservatory simple spectrum access and table access services using compliant client applications. Wedescribe examples of SQL queries against the database. Finally, we briefly discuss existing and futurescientific applications of RCSED and prospectives for the catalog extension to higher redshifts anddifferent wavelengths.
Galactocentric Dependence of Sulfur Isotope Ratios
Chin, Yi-nan
Element abundances generally consider an element without distinguishing between its different isotopes. From the point of view of nuclear physics, however, isotopes of the same element are formed differently and should be treated like different elements. Using optical spectroscopy, it is difficult to distinguish isotopes observationally. The measurement of abundances of each element involves several isotopes and thereby different paths of stellar nucleosynthesis. In practice, only the formation of the main isotope can be considered. Radio observations, however, provide a very reliable means to measure the abundance ratios between isotopes within the same element. The isotope formation thus can be studied by comparing the observations to the nuclear theory. Here we present our observation of the 4 different sulfur isotopes. The galactocentric dependences of their ratios are obtained and their formation is discussed.
Using Hilbert-Huang Transform to Resolve Quasi-Periodic Oscillations in Accreting Compact Object Systems
Chou, Yi
Quasi-periodic oscillations (QPOs) have been seen in many X-ray binaries and a few active galactic nuclei in X-ray band. Their broad peaks in the power spectra indicate that the oscillations are non-stationary in either or both frequency and amplitude. Time-frequency analysis techniques are able to track the evolution of QPO to further understand this phenomenon. We adopted the Hilbert-Huang transform (HHT) to resolve the QPOs in accreting compact object systems. In addition to tracking the evolution of the frequency and amplitude, the well-defined phases from the HHT allow us to produce precise modulation profiles and process phase-resolved spectral analyses. In this poster, we present our achievements in applying HHT to analyze the QPOs of several accreting compact object systems, including the low frequency QPOs in the black hole binaries XTE J1550-564 and GX 339-4, the millihertz QPO in the neutron star X-ray binary 4U 1636-53 and the QPO in the narrow-line Seyfert 1 galaxy RE J1034+396.
Popularizing “Non-Glamorous” Areas of Astrophysics like Solar Physics
Choudhuri, Arnab
Astrophysics is a branch of science which excites popular imagination and there has been a glorious tradition of popular science writing on astrophysics by both research astrophysicists and outreach professionals. Of late, however, we see a tendency which I find disturbing. While popular science books keep being written on certain glamorous areas like cosmology and black holes at an ever-increasing rate, many other important areas of astrophysics have been grossly neglected by popular science writers in the past few years. When the first popular science book on the phenomenology and the science of the 11-year sunspot cycle written by me:_x005F https://www.amazon.co.uk/Natures-Third-Cycle-Story-Sunspots/dp/0198807643/_x005F was published by Oxford University Press in the hardback priced at 25 GBP, I thought that nobody would buy a popular science book at this price. To my complete surprise, the book nearly sold out in two years and a paperback had to be printed. This shows that there is a demand for popular books on non-glamorous areas of astrophysics. Based on my experience with my book, I shall discuss how popular science books on such areas should be written. In my opinion, it is rather important to pick a central thread and develop a storyline around it, rather than presenting many topics in a piecewise manner. I shall also argue that it is important for research astrophysicists to take part in such initiatives, as it can sometimes be difficult for outreach professionals to decide the right storyline.
Constrain the atmospheric properties of Wasp-31b using models.
Chouqar, Jamila
Wasp-31b, is a planet of 0.48 Jupiter masses and 1.55 Jupiter radii, with orbital period of 3.4-day around a metal-poor, late-F-type, V = 11.7 dwarf star. This gives it a large atmospheric scale height that makes it a good target for transmission spectroscopy._x005F Previous works studied the presence of Potassium in this exoplanet. Sing et al (2014) present an optical and near-IR transmission spectra of the atmosphere of WASP-31b obtained with the HST and show the presence of a strong potassium line. In contrast Gibson et al (2017) reports a spectrum of the atmosphere of WASP-31b, obtained with the FORS2 instrument on the VLT and find that there is no strong potassium line. Here, we take the publish data of WASP-31b (the datasets from Sing and Gibson's papers) and using models, we try to find a case where both solutions are correct by considering different cloud scenarios._x005F _x005F _x005F _x005F _x005F _x005F _x005F _x005F _x005F _x005F _x005F _x005F
Evolution of multiplanet systems in 2D and 3D radiative disks
Chrenko, Ondrej
Dynamical evolution of an isolated low-mass protoplanet is driven by gravitational interactions with its natal protoplanetary disk. Proper migration modelling requires radiative hydrodynamics (RHD) in order to correctly account for the disk thermodynamics (e.g. Kley et al. 2009) and advection-diffusion phenomena occurring close to the protoplanet (e.g. Lega et al. 2014, Benitez-Llambay et al. 2015). However, only a limited number of RHD models involving multiple Earth-like (or even smaller) protoplanets have been constructed up to date.Here we study the evolution of such a multiplanet system within a radiative disk. First, we review the results of Chrenko et al. (2017), highlighting the importance of so-called hot-trail effect related (in this particular case) to the heating of protoplanets by pebble accretion. Specifically, we demonstrate how the hot-trail effect excites orbital eccentricities, increases frequency of close encounters, prevents resonant captures and allows for merging of protoplanets. The simulations are obtained using the 2D Fargo_Thorin code, and thus contain several inevitable caveats: The damping of orbital inclinations is not self-consistent but prescribed, the hot-trail does not affect inclinations, and vertical averaging fails to fully reproduce the flows in the vicinity of a protoplanet.We therefore present additional simulations in 3D using the Fargo3D code (Benitez-Llambay & Masset 2016) into which we implemented a solver of the radiation-gas energy equations (similar to Bitsch et al. 2013) and also the Rebound/IAS15 integrator (Rein & Spiegel 2015), capable of resolving close encounters and possible merging of protoplanets. We compare the results with the above-mentioned 2D modelling and discuss the differences. Additionally, the model is applied to the inner part of the disk in order to compare the properties of the synthetic systems with the observed close-in exoplanets.
Dwarf galaxies at high redshifts probed by absorption lines
Christensen, Lise
Absorption lines in background objects such as luminous quasars or gamma-ray bursts reveal clouds of intervening gas with relatively low metal enrichments out to high redshifts (z>5). During the past few years we have finally reached the consensus that the strongest Hydrogen absorption lines arise in disks or in the circum galactic medium of galaxies that randomly lie along the line of sight to background sources.Akin to the relation between stellar mass and metallicity seen in emission selected galaxies, we find a similar relation for absorption lines, i.e. the most metal-rich absorbers arise in relatively massive galaxies. Conversely, it means that the majority of absorbers that have around 10% solar metallicities arise in low-mass galaxies. Absorption line spectroscopy therefore harbours information on the physical nature of galaxies from low to high redshifts.I will present the connection between luminosity-selected and absorption-selected galaxies, and demonstrate how absorption lines give complementary information on the evolution of low-mass galaxies, and their circum galactic environment. Finally, I will describe how we can use absorption lines to probe the structure of the dark matter halos of dwarfs at intermediate to high redshifts.
Metallicity of the star formation
Chruslinska, Martyna
Metallicity is the second most important property, just after mass, determining the stellar evolution.It affects, among others, stellar winds and radii, also impacting the evolution of stars in binaries.As a consequence, in general the frequency of any stellar/binary evolution related phenomena (e.g. merger rates of double compact objects) will depend on metallicity.To correctly predict the rates of such events and confront them with observations, it is important to understand how the cosmic star formation is distributed across different metallicities and redshifts.In order to obtain this distribution and study how well constrained is it by current observations, we combine the available observational properties of star forming galaxies.One of the key ingredients in our study is the mass - metallicity relation, in particular its evolution with redshift and the amount of scatter present in this relation. We discuss how different choices allowed by observations affect our results.
Where did different characteristics of dwarf galaxies come from?
Chun, Kyungwon
We investigate cosmological evolution of isolated dwarf galaxies in the Lambda-Cold Dark Matter model. For this, we modified a cosmological hydrodynamic code, GADGET-3, in a way that includes gas cooling down to T~10 K, gas heating by universal reionization, UV shielding for high-density regions of nshield > 0.014 cm-3, star formation in the dense regions (nH > 100 cm-3), as well as mass, energy, and metal feedback by supernova explosion. We perform four different zoom simulations targeting dwarf galaxies whose total mass is ~1010 Msun. Although four galaxies have similar total mass at z=0, their morphologies, star formation activities, and baryonic properties are very different to each other. In this study, we aim to trace where the differences originate.
Star formation histories of the LEGUS dwarf galaxies
Cignoni, Michele
I will present the detailed recent star formation history (SFH) of dwarf galaxies between 3 and 12 Mpc from the Legacy ExtraGalactic UV Survey (LEGUS). This sample includes a variety of morphologies and densities, such as the diffuse and low density Holmberg II, the Magellanic irregular NGC4449 and the Blue Compact NGC1705. The SFHs are derived by comparing deep UV color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs. In order to assess the uncertainties related to stellar evolution modelling, two independent sets of stellar isochrones are used: PARSEC-COLIBRI and MIST. The SFHs derived with the two different sets of stellar models are consistent with each other, except for some quantitative details, attributable to their input assumptions. I will discuss how these SFHs compare with previous optical CMD studies and integrated SFR measurements (Hα and UV). Critical insights into the evolution of massive main-sequence and helium-burning stars will be also provided.
ASTERICS and the Challenge of Multi-Messenger Astrophysics
Cimo', Giuseppe
Multi-messenger astrophysics is a field rich in opportunities but also challenges. It requires collaboration and coordination within a global network of facilities. The scientific drive towards combining and aligning data from different facilities in order to comprehensively study multi-messenger and transient events requires interoperability between hybrid data streams with unprecedented time synchronization across locations distributed across the Earth. The current observational strategies need to be adapted to take into account commensal operations. Practically, new approaches to computing and data analysis by means of machine learning have to be implemented because of the data volume and the issues of complex scheduling of hundreds of antennas operating at different regimes. Aligned with this vision, the European Commission approved (in the framework Horizon 2020) the ASTERICS initiative -ASTronomy ESFRI and Research Infrastructure CluSter- to collect knowledge and experiences from astronomy, astrophysics and particle physics and foster synergies among existing research infrastructures and scientific communities, with the ambition of seeing them interoperate as an integrated, multi-wavelength and multi-messenger facility. In my contribution, I will present the efforts of the ASTERICS cluster towards the interoperability of the next generation of astronomical and (astro)particle physics facilities.
A near-infrared VISTA of the Small Magellanic Cloud
Cioni, Maria-Rosa
VISTA observed the Small Magellanic Cloud, as part of the VISTA survey of the Magellanic Clouds system (VMC), for six years (2010-2016). The acquired multi-epoch YJKs images have allowed us to probe the stellar populations to an exceptional level of detail across an unprecedented wide area in the near-infrared. In this contribution, I will review the VMC results obtained on the SMC focusing in particular on the most recent investigations of the parameters and distribution of its stellar populations. I am also going to present the first complete public VMC data release of the SMC.
AGN and Star Formation Feedback in Active Galaxies
Clavijo bohórquez, William Eduardo
Large scale, weakly collimated out?ows are very common in some active galaxies. In complex systems, where (SF) coexists with an active galactic nucleus (AGN), like in Seyferts, and probably dwarf galaxies and ULIRGs, it is unclear yet the relative role that the AGN and the SF play in the driving of the out?ows, which frequently exhibit persistent high-speed cold structures.In this work we present high-resolution 3D hydrodynamical and magnetohydrodynamical (MHD) numerical simulations of the formation of these out?ows considering both the feedback from the AGN outflow (with opening angles between 0 and 10 degrees), and the supernovae (SNe)-driven wind (including the contributions of type I and II).The results indicate that the presence of an AGN wind with large opening angles and of magnetic fields substantially a?ect the evolution of these systems. While magnetic ?elds help to preserve dense structures of the ISM which are swept by the SN and AGN outflows, the large-opening angle AGN wind may temporarily exhaust the gas near the nuclear region (thus extinguishing star formation) and account for the highest speed features in the wind at kpc scales, although these are not as cold as required by the observations. The SN-driven wind is the main responsible for the mass-loading of the outflows, while the AGN wind accounts for the highest speed component which reaches velocities up to a few 10,000 km/s. Finally, the implications of these findings in the framework of dwarf galaxies evolution will be also discussed.
The impact of the environment on the dust reservoir and star formation in local massive galaxies.
Concas, Alice
The star-forming properties of galaxies that reside in the dense cores of galaxy clusters are remarkably different from those in the field. Several observations confirm that quiescent early-type galaxies are much more prevalent in cluster cores whereas star-forming spirals dominate in the field. The dominant mechanism responsible for this bimodal distribution of galaxies in different environments, remains elusive. In this talk, I will present an observational investigation into the optical spectral properties of central massive galaxies: star formation and, dust reddening. For this purpose, I use the statistical power of the Sloan Digital Sky Survey to examine central galaxies across a wide range of host halo masses, from massive clusters to the lowest halo mass groups in the local Universe. I will show that galaxies in low mass halos groups (Mh < 1012.5 M?) have higher Balmer decrement and redder stellar continuum than galaxies in high mass halos group (1012.5 < Mh < 1013.5 and Mh > 1013.5 M?). Hence, galaxies in lower mass halos tend to be more dusty. The presence of an higher dust content in galaxies inhabiting lower mass halos could point to a higher amount of cold dense gas in such halos, as confirmed by the HI and CO observed in groups in the local Universe.
Jovian System as a demonstration of JWST’s capabilities for Solar System science: Status Update
Conrad, Albert
Our team will observe the jovian system, with the following scientific goals:Characterize Jupiter’s cloud layers, winds, composition, auroral activity, and temperature structure;Produce maps of the atmosphere and surface of volcanically-active Io and icy satellite Ganymede to constrain their thermal and atmospheric structure, and search for plumes; Characterize the ring structure, and its sources, sinks and evolution.We will present our progress to date in planning these observations and provide an update on our expectations.Our program will utilize all JWST instruments in different observing modes to demonstrate the capabilities of JWST’s instruments on one of the largest and brightest sources in the Solar System and on very faint targets next to it. We will also observe weak emission/absorption bands on strong continua, and with NIRIS/AMI we will maximize the Strehl ratio on unresolved features, such as Io’s volcanoes.We will deliver a number of science enabling products that will facilitate community science, including, e.g.: i) characterizing Jupiter’s scattered light in the context of scientific observations, ii) resolve point sources with AMI in a crowded field (Io’s volcanoes), and compare this to classical observations, iii) develop tools to mosaic/visualize spectral datacubes using MIRI and NIRSpec on Jupiter. Finally, our program will also set a first temporal benchmark to study time variations in the jovian system and any interconnectivity (e.g., through its magnetic field) during JWST’s lifetime.
Sizing up small bodies: New technologies, new challenges
Conrad, Albert
In recent years the exploration, characterization, and mapping of small bodies via remote sensing has continued at an ever-quickening pace. Advances in adaptive optics on bigger telescopes now allow researchers to study the shape of main belt asteroids like (16) Psyche at the resolution of a few kilometers from ground-based facilities [Drummond, et al (2018), Shepard, et al (2017)]. Spectrographs, optimized for the purpose, can determine the composition of small bodies as faint as 21st magnitude, in some cases only 50 meters in diameter [Reddy, et all (in prep)]. Advances in radar, stellar occultation, and light curve methods also continue; and all of these methods can often be combined to make accurate shape measurements of an increasingly large population of worlds that can be mapped [Carry, et al (2012)].With new technologies come new challenges, for example "big data" and complex data products that can only be interpreted by sophisticated software pipelines. In our presentation, we report on new methods and policies for meeting these challenges. In particular, we look at how the community is coping with the rapid increase in the reported measurements of small body properties; with special attention to those bodies that are the intended destination for spacecraft missions, such as the NASA Discovery Class mission to (16) Psyche.
Chemical Evolution and the formation of Planets on the primordial Universe
Corazza, Lia
We present a discussion about the relation between planet formation on the primordial universe and the cosmic chemical evolution. We developed a semi-analytical model that provides the evolution for 11 chemical elements since Pop III stars (Z = 0) started to die until the formation of Pop II stars with metalicity Z = 2.10-2 Zsolar . Results indicate that C, N and O could play a very important role on the formation of planets. By modelling the cosmic planet formation rate (earth-like and gas giants) estimated in [1] and the amount of metals removed from the interstellar medium in the formation process, we can investigate the role of chemical elements (mainly C, N and O) on the formation of planets since the universe was very young (about 180 Myr, z = 20). We are also able to briefly dicuss at what point the avaibility of metals in the universe could provide conditions to foster the formation of the first chemical building relevant to the appearance of life.[1] Zackrisson, E., Calissendorff, P., Gonzalez, J., Benson, A., Johansen, A., Janson, M. Terrestrial Planets across Space and Time. ApJ, 833. 2016.
Quantitative and Qualitative Evaluation Methods to Assess New Experiential Teaching Techniques in Astronomy Theatre
Corbally, Christopher
These evaluations assess a supplementary astronomy text book meant to be used in English, French, Spanish, and Portuguese. It exists now only in English, but it is advertised on Amazon France, and on Chinese web sites. Its approach to learning science is experiential. Students get up and assume roles in small plays or view them.Our poster displays a selection of evaluation methods and analytical techniques, based on four evaluations of the book, SPACE SCIENCE AND ASTRONOMY THEATRE. All evaluations involved live enactments of astronomy scripts:pre-design focus meetings; trial questions (with community group of adults with children);structured evaluation of 3 teaching packages using a series of data collected at 4 time points (for quantitative analysis); focus discussions (with Spanish-origin, American senior high school class);demonstration of a single package using evaluators, then students, in theatrical roles (with a junior college class); anddemonstration in a university astronomy class, Q & A (200 students).The poster includes methods of program evaluation and policy analysis that can help in demonstrating efficacy in same-country/multiple group, or cross-national settings.Policy analysis of astronomy organizations’ goals for a worldwide workforce. What do they need to know?Analysis of deficiencies in data on space science careers. Issues of gender and developing country origin.Planning data collection design in stages. Designing instruments congruent with available data types and desired analysis.Focus groups for different types of respondents. Include expert focus groups.Quantitative data collection and analysis (before/after; time series potentially for ANOVA when N is sufficient).Administrative records data review (record number, gender, age, year, special program).Analyze change in Self-report questions over time (“humanities” v. “science” student) (relative “affectedness”) (orientation to science positive/negative).
Cold dust and molecules across the M33 disk
Corbelli, Edvige
The dust-to-gas ratio across the M33 disk is presented and compared to the metallicities inferred viaoptical line emission. Despite the surface density of atomic gas is radially constant, the molecular gas surface densitytraced by CO line emission declines radially and implies a different radial trend of the dust-to-gas ratio thanwhat we expect from the metallicity gradient. Being M33 a close, well resolved spiral galaxy, the analysis of the localdust abundance, averaged over 50 pc regions, is used to investigate if dust formation and destruction processesvary as the physical conditions change across the disk. The other possibility is that the weakness of CO lines andthe absence of large molecular complexes lead to an underestimate of the molecular gas surface density in the outer disk as suggested by the shape of the probability distribution function, traced via dust, HI and CO emission.
Photometry and spectroscopy of cataclysmic variable stars
Cori, William
Cataclysmic variable (CV) stars is the topic of my doctoral thesis work, they are binary systems composed by a white dwarf and a red dwarf where the red one has filled its Roche lobe, so it is produced a mass flow from the red one to the white one through the first Lagrange point. I am addressing this topic with both photometry and spectroscopy.Photometric part is related to the measuring of the orbital period of these stars from light curves built from data acquired in our own university observatory (0.5 m OTA) implemented on 2015. From May through August of 2017 we have observed five stars: V893 Sco, CTCVj2118-3413, EI Psc, ASASSN-17hx, and V701 Tau, these are the first CV stars registered by our observatory; we will show the calculated orbital periods.Spectroscopic part is related with the finding of the characteristics of the components of the system from spectra obtained from several databases. Spectra of four stars have been gotten: HS 0220+0602 from ESO Data Archive, and SDSSJ121130.94-024954.4, SDSSJ222108.45+002927.7, and IR Com from Sloan Digital Sky Survey DR14. We will show the results obtained from our own fitting program.
The massive stars population of IC 10
Corral, Luis
Metal-poor massive stars are key to understand star formation and feedback process in the past Universe, extreme events like SLSN and GRBs, and possibly the properties of the First Generation of stars. The dwarf irregular galaxies of the Local Group make a large reservoir of these objects, with the advantage that their physical properties in various environments can be studied in detail.We present a catalog of massive stars and OB associations in IC10. We have identified 529 candidate massive stars meeting the photometric criteria that we have proven successful in IC1613 and Sextans-A. Our friends-of-friends clustering algorithm has detected 26 associations with 3 or more members, whose age spans from log(age)=6.19-7.05 dex. This census is particularly interesting as IC10 is currently undergoing a starburst phase, and it makes way to study metal-poor massive stars in the first such environment beyond the Magellanic Clouds.
The S0 road: a network of routes to create lenticular galaxies
Cortesi, Arianna
In this talk, I will present evidences that lenticular galaxies are a heterogeneous family, composed by stripped spiral galaxies, 'fossil groups', resulting from the accretiion of many small companions on a central galaxy, or primordial galaxies which formed at redshift around 2, through clumpy disk formation. These results are achieved combining several data sets, from planetary nebulae (PNS) and globular clusters (SLUGGS) kinematics of lenticular galaxies, living in the field and group environments, to observations of lenticular galaxies in the Hydra cluster, as obtained with the new multi-wavelengths survey SPLUS. While galaxy stripping and accretion, as possible formation scenarios of lenticular galaxies, have already been suggested and tested via simulations, the clumpy disk formation scenario is a new possible route to the formation of S0 galaxies, supported by simulations from K. Saha (IUCAA) and suggested by A. Romanowsky et al. (submitted to Science).
The Role of Shocks in the Detemination of Empirical Abundances for Type-I Planetary Nebulae
Costa, Roberto
Despite the growing use of photoionization models to derive chemical abundances of Planetary Nebulae (PNe), empirical abundances derived with the help of Ionization Correction Factors (ICFs) are still very useful for large samples where frequently no information on the central star is available for most nebulae. This work aims to investigate, in the light of new diagnostic diagrams, the role of shocks in the excitation/ionization of type-I PNe, and their relation with the empirical derivation of chemical abundances. We applied the diagnostics to NGC 2440 and NGC6302, both very well known, the first is multipolar with at least two bipolar components, and the second is bipolar. Our results indicate that shocks play a crucial role in both nebulae.The presence of shocks reinforces the flux of low ionization lines, and the results show that, for these nebulae, shocks are present indeed. This artificial reinforcement of low ionization lines can lead to wrong chemical abundances, when derived through ICFs, at least for type-I PNe. A comprehensive study of this effect, applied to a larger PNe sample and including all types, ideally a statistically complete sample, would be required to clarify this proposition.
New PARSEC-V2.0 stellar isochrones with alpha-enhanced mixtures and rotation
Costa, Guglielmo
We present a large set of rotating and not rotating evolutionary tracks for initial masses between0.1 and 350 solar masses. We discuss the method adopted to calibrate the free parameters associated with rotation and convective overshoot.We explore a wide range of metallicities and alpha elements partitionsand show how these parameters affect the Asymptotic Giant Branch phase.The corresponding isochrones will be soon available on-line.
Status of Astronomy in Namibia
Cotter, Garret
Southern Africa is becoming a beacon for astronomy throughout the electromagnetic spectrum: In all wavebands accessible from ground, the largest astronomical facilities are either operational or in the process of being set up in the region, see e.g. [1].The Southern African Large Telescope (SALT) in Sutherland (South Africa), measuring 11m in diameter, is the largest single optical telescope in the Southern hemisphere [2]. The deployment of the telescopes of the MeerKAT radio telescope, being the largest and most powerful radio telescope in the Southern hemisphere, has just completed [3]. The 64-dish MeerKAT telescopes will later develop into the Square Kilometre Array(SKA), the most sensitive radio telescope on Earth, utilizing outlier station all over Southern Africa [4]. The High Energy Stereoscopic System (H.E.S.S.) telescopes [5] in the Khomas highlands in Namibia are the largest and most powerful system of Cherenkov telescopes to study very high energy (E>100 GeV) gamma-rays. For its successor, the Cherenkov Telescope Array (CTA) [6,7], Namibia has been voted second of possible countries to host the Southern part [8,9].Against this background, the current situation of astronomical research and education in Namibia will be reviewed, specifically focusing on recent developments regarding growing collaborations with UK institutions.References[1] M. Böttcher, “The violent universe”, http://hdl.handle.net/10394/9632 [2] http://www.salt.ac.za[3] http://ska.ac.za/meerkat [4] http://ska.ac.za/about[5] https://www.mpi-hd.mpg.de/hfm/HESS[6] B.S. Acharya et al., “Introducing the CTA concept”, Astroparticle Physics, Vol. 43, p. 3-18 (2013)[7] http://www.cta-observatory.org[8] M. Backes, “Current Status of the Namibian bid to host the Cherenkov Telescope Array”, Proceedings of Science, PoS(HEASA2015)001 (2015)[9] https://www.cta-observatory.org/wp-content/uploads/2016/10/Paranal-and-La-Palma-Sites_07162015_v2_rev.pdf
Abundance Patterns in Herbig Ae/Be Stars
Cowley, Charles
The peculiar chemistry of some HAeBe stars is usually described as resembling the photospheric composition of the Lambda Boo stars, where the lighter CNO elements have normal or solar composition while the heavier elements are depleted. In Lambda Boo stars, this abundance pattern is closely related to the volatility of the elements, essentially to the condensation temperatures (Tc). The "Lambda Boo" abundance pattern is much too simplistic to describe modern results. The simplest abundance pattern in HAeBe stars shows a high correlation with Tc. However, unlike the canonical Lambda Boo pattern, the volatile elements may be significantly overabundant. Within the CNO elements themselves, large abundance anomalies can occur. Most puzzling is the behavior of intermediate volatiles, such as sodium and especially zinc. Simple mechanisms based only on Tc canot explain these anomalies.The magnetic fields of HAeBe stars are weaker and less common than in their low-mass congeners, the T Tauri stars. An understanding their magnetism combined with their chemistry should help to constrain theories of their formation and magnetospheric accretion histories.We remark on the difficulties and uncertainties in analyzing spectra often replete with emissions, and significant rotational broadening. Use of the Ca II K-line to determine spectral type, and thence E(B-V) is questionable. However, most HAeBe stars show diffuse interstellar bands, whose strengths can be related to E(B-V).
Nitrogen Chemistry in Exoplanetary Atmospheres - Prospects with JWST-MIRI
Cridland, Alex
While the carbon and oxygen content of exoplanetary atmospheres have been investigated both observationally and theoretically, the nitrogen content has been left largely untouched. Nitrogen is difficult to detect because its most abundant carrier is its (invisible) molecular form, and the infrared features of its other carriers (NH$_3$ and HCN) are often hidden among other, more prominent molecular features. With the James Webb Space Telescope our prospects of detecting nitrogen chemistry grows - particularly with its Mid-Infrared Instrument (MIRI). In this talk I will outline the connection between a planet's carbon-to-nitrogen ratio and the environment from which it formed by tracing the planet's formation history through an evolving astrochemical disk. Because nitrogen tends to be in the gas phase (typically N$_2$ or NH$_3$) within the planet forming region ($< 10$ AU) of the disk, it will be accreted directly into the atmosphere of a growing planet. Once in the atmosphere, nitrogen carrying species are subject to vertical transport, winds, and chemical processing which plays an important role in determining the viability of their detection. I will outline some preliminary work which focusses on the nitrogen photochemistry and vertical transport in Hot Jupiter atmospheres to explore the prospects of finding nitrogen carriers with JWST-MIRI. Since Hot Jupiters are highly irradiated by their host star, we find that the atmosphere will be driven far from the chemical state predicted by thermochemical equilibrium calculations.
Disks around FU Orionis-type young eruptive stars as viewed by ALMA in the dust continuum
Cruz-Saenz de Miera, Fernando
A long-standing problem of the general paradigm of low-mass star formation is the "luminosity problem": protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Orionis-type stars (FUors) are thought to be the visible examples for objects in the high accretion state. It is still debated what physical mechanism triggers the increased accretion in FUor disks and whether all young stars undergo FUor phases. Recently, more and more studies suggest that some FUor disks are smaller and less massive than previously believed (Liu et al. 2018, Cieza et al. 2018), but for many objects, disk properties are still largely unknown. Motivated by this, in the framework of the Structured Accretion Disks ERC project at Konkoly Observatory, we conducted a deep, high spatial resolution (down to 20 au) 1.3 mm dust continuum survey of 10 FUors with ALMA. Here we present the results of our survey, including basic disk parameters, such as mass, size, spectral slope, possible asymmetries, etc. We detected all targets with high signal to noise ratio, and most of them seem very compact. We compare our results with the requirements of outbursts in different theories. We also put our sample into context by comparing them with disk properties of non-outbursting sources from large ALMA surveys, to see whether FUor disks are special in any way or they are indistinguishable from the general disk population.
The effect of photoevaporation on the formation of planets in the habitable zone
Császár, Anna
An important research topic in astrophysics, which has a special interest not only for the scientificcommunity but also for all, is whether life may have evolved in some exoplanetary systems. The region of a planetary system, where water-based life could appear is called the habitable zone.In order to understand and numerically simulate planet formation one should investigate the time-evolution of protoplanetary disks being governed by gas accretion onto the star and photo-evaporation by the radiation of the central star. Using a 1D time evolving disk model (Lynden-Bell & Pringle, 1974, MNRAS 168, 603) we implement the formulae for X-ray photoevaporation provided by Owen et al. (2012, MNRAS 424, 1880). Beside the gravitational interactions between planets, planetary systems obtain their final orbital configuration by migration in the gas disk. Therefore we calculated the timescales for orbital decay, as well as the damping timescales for eccentricities and inclinations using the local physical parameters of the protoplanetary disks obtained during numerical simulations.Since a gap is forming in the disk as a result of photoevaporation, we particularly investigate its effect on the dynamical behavior of planets. This may have consequences as accummulating terrestrial planets in the habitable zone around the star, if the location of the gap overlaps with the habitable zone. One of the major goals of our research is to map the extent of this overlapping.
What tell close-in brown dwarfs about planetary system's evolution and formation?
Csizmadia, Szilárd
While there are thousands of transiting exoplanets (confirmed or suspected), transiting brown dwarfs are extremely rare and their number is well below 20. However, discovery of brown dwarfs in orbits with orbital period less than 10 days by CoRoT, Kepler, K2 and ground-based surveys caused a surprise because they are in the so-called 'brown dwarf desert' where their occurrence was not expected. Brown dwarfs are suspected to be just high mass giant-planets, the deuterium- or lithium burning are so episodic events that the brown dwarfs can be considered identical to giant planets in the mass-radius diagram (Hatzes and Rauer 2015). Accepting this picture, brown dwarf occurence rates should be studied jointly with the occurence rates of giant planets.Since small mass brown dwarfs may form in the same way as giant planets, close-in brown dwarfs can be test objects: are planet formation theories are generally valid for all mass ranges?Our study showed that the true frequency of brown dwarfs close to their host stars (P< 10 d) is estimated to be approximately 0.2% which is about six times smaller than the frequency of hot Jupiters in the same period range. This result was based on the CoRoT survey. We suspected that the frequency of brown dwarfs declines faster with decreasing period than that of giant planets. We presented an occurrence rate - binary separation relationship for brown dwarf-solar like star systems based on transiting, radial velocity and adaptive optic techniques, and discuss this relationship from a planetary system formation point of view. We point out that our predicted relationship was later fully confirmed by Kepler and by other radial velocity surveys.
Data-driven Astronomy Educcation and Public Outreach
Cui, Chenzhou
IAU Inter-Commission B2-C1-C2 WG Data-driven Astronomy Education and Public Outreach (DAEPO) was launched officially in April 2017. With the development of many mega-science astronomical projects, for example CTA, DESI, EUCLID, FAST, GAIA, JWST, LAMOST, LSST, SDSS, SKA, and large scale simulations, astronomy has become a Big Data science. Astronomical data is not only necessary resource for scientific research, but also very valuable resource for education and public outreach (EPO), especially in the era of Internet and Cloud Computing. IAU WG Data-driven Astronomy Education and Public Outreach is hosted at the IAU Division B (Facilities, Technologies and Data Science) Commission B2 (Data and Documentation), and organized jointly with Commission C1 (Astronomy Education and Development), Commission C2 (Communicating Astronomy with the Public), Office of Astronomy for Development (OAD), Office for Astronomy Outreach (OAO) and several other non IAU communities, including IVOA Education Interest Group, American Astronomical Society Worldwide Telescope Advisory Board, Zooniverse project and International Planetarium Society. The working group has the major objectives to: Act as a forum to discuss the value of astronomy data in EPO, the advantages and benefits of data driven EPO, and the challenges facing to data driven EPO; Provide guidelines, curriculums, data resources, tools, and e-infrastructure for data driven EPO; Provide best practices of data driven EPO. In the paper, backgrounds, current status and working plans in the future are introduced. More information about the WG is available at: daepo.china-vo.org
Habitable Zones around K and M Dwarfs
Cuntz, Manfred
One of the most fundamental topics of exobiology concerns the identification of stars with environments suitable for life. Although it is believed that most types of main-sequence stars might be able to support some forms of life (especially extremophiles), special requirements appear to be necessary for the development and sustainability of advanced life forms. The focus of this presentation is an assessment of ionizing radiation impact from dwarfs of spectral types K and M. Aspects taken into account include (1) the frequency of the various types of stars, (2) the rate of stellar evolution over their lifetimes, (3) the width of the circumstellar habitable zones (CHZs), (4) the strength and persistence of their magnetic dynamo generated X-ray—Extreme UV emissions, and (5) forcing associated with space weather. The advantages and shortcomings of K and M-type dwarfs are discussed in the view of observations and updated theoretical results.
Urania as 100 years old astronomical magazine, coeval of the IAU
Czart, Krzysztof
"Urania" is Polish popular astronomy magazine, one of the oldest in the world among present journals of this type. The first official issue was published in 1922, but the origins of "Urania" are even older, as in 1919 there were published a few issues of predecessor of "Urania" with the same title. So we can say that "Urania" and IAU are in the same age. The role of "Urania" has been changing during these 100 years, but "Urania" has been always very important entity for astronomical community in Poland, both professional and amateur. Thousands of pages contain a history record of astronomy in Poland, as well as progress of astronomy in the world, including IAU activities. Major part of articles in Urania is written by professional astronomers - they describe their own research, their own discoveries. During presentation we will also show how the magazine is doing in XXI century, in the era of internet and electronic media. Conclusions from our experience useful for international audience of astronomy professionals and astronomy communicators will be also presented. Publishers of "Urania" are the Polish Astronomical Society (organization of professional astronomers established in 1923) and the Polish Astronomy Amateurs Society (organization of astronomy amateurs established in 1919).
Astronarium TV series as an example of cooperation between astronomers and media
Czart, Krzysztof
Global video series produced by the IAU presenting astronomy in every member country? Maybe this idea is worth considering? We would like to present and inspiring example for other national societies gathered in IAU for developing TV series about astronomy in their countries and maybe also for the global video series by the IAU. "Astronarium" is a TV series in Poland about astronomy and space produced together by the Polish Astronomical Society (PTA) and the Polish Television (TVP). Over 50 episodes has been boradcasted since 2015 with audience many of them exceeding million viewers (per single episode). It is also available at YouTube with over 2 million views. Scientists (astronomers) often know from their experience that it is not easy to cooperate with journalists, especially from large, general media, like television. In "Astronarium" we succeed to break the barrier between these two "worlds". Very often if scientist appears in TV it is in the context of a news or as a part of a "show" program. In Astronarium astronomers have change to talk more about their work that in typical TV appearance of scientist. Our cameras have shown over a dozen scientific astronomical institutes in Poland and all over the world and about 100 scientists had a chance to present their reserach. We are also looking for volunteer translators among astronomers for subtitles for various languages. Astronarium is available at www.astronarium.pl and www.youtube.com/AstronariumPL.
AstroGPS - database of all astronomy and space related events with a mobile app
Czart, Krzysztof
There are various systems of events coordination on a global scale (for example supported by the IAU) or on national level. We would like to present the AstroGPS system which is about to start in Poland in 2018. AstroGPS is a mobile app and a web portal with database of all events related to astronomy and space which are organized in the country. These are events on nationwide, regional or local level, like conferences, workshops, prelections, astro shows, science festivals, emissions of radio or TV programs, contests, astro picnics, astro camps and many other events. AstroGPS has three main groups of users: society of people who are interested in astronomy and space, organizers of events and media (journalists). In can be very helpful also for schools and teachers. For all these groups it might help in their functioning and activities in astronomy-space related areas. AstroGPS can be inspiration for similar national systems in other countries or in future be a part of a global system of this kind in astronomy and space science.
On the long-term evolution of cyclotron lines in accreting neutron stars
D'Aì, Antonino
In my presentation I'll focus on two important open issues in the physics of accreting magnetized neutron stars: how the accretion flow settling on their surface affects the local topology of the magnetic field lines and how the secular evolution of the binary system depends on the dissipation rate of the NS intrinsic magnetic field.In the X-ray spectra of accreting NS binaries, the presence of the cyclotron resonant scattering features,indicates the intensity of the field in the region where the line is formed. This optically thick region can move in correlation, or anti-correlation, with the mass accretion rate, depending if a radiative shock is formed or not. In this way, cyclotron features probe the B-field intensity along the accretion column and, for spectra selected at the same level of luminosity but at different epochs, the field's evolution on longer time-scales. I will report on recent spectroscopic studies on cyclotron line features obtained from the Swift/BAT survey data for a set of high-mass binaries and what new clues they give for the current understanding of magnetic fields in accreting neutron stars [1,2,3].references:[1] A. D'Aì, G. Cusumano, M.Del Santo, V.La Parola, A.Segreto, 2017, MNRAS, 470, 2457[2] G. Cusumano, V. La Parola, A. D'Aì, et al., 2016, MNRAS, 460, L99[3 ]V. La Parola, G. Cusumano, A.Segreto , A.D'Aì, 2016, MNRAS, 463, 18
Inspiring Stars
D'Antonio, Maria Rosaria
Inspiring Stars” is an itinerant international exhibition promoted by the International Astronomical Union (IAU) to disseminate world initiatives addressing inclusion at outreach, didactic, and professional level in astronomy with the ultimate goal of evolving from levelling the playing field to equal participation.This poster presents a historical context of inclusion in the field of astronomy at professional, didactic and outreach endeavours. The authors present an informal survey of multi-sensorial methods at research, education and outreach in the field and approach the lack of formal comparable data regarding inclusion in the science of astronomy. “Inspiring Stars” is a collaborative experience where resources related to astronomy Research, Communication and Development are collected, via an open call around the world and combined in a unique display. The IAU aims for this exhibit to become a joint effort by the community and for the community. Inclusive both in goals and practices, the exhibition will change and grow with the communities it visits - assimilating best practices around the world, and for the community - by incorporating and disseminating different local efforts and strengthening global ties between the communities. This poster further presents a work in progress, framework of bridging activities and inclusion in the social context, that may provide inspiring stars the potential to document and motivate the generation of comparable data on inclusion in astronomy.
Rotation measure asymmetry reveals a precession of the AGN outflow in a Seyfert galaxy.
Damas-Segovia, Ancor
Feedback on galactic-scales is an important question in studies of cosmic evolution of galaxies. It is believed that AGN driven jets and/or stellar winds plays an important role in driving materials away from galactic discs. In this regard, we demonstrate that radio polarization studies of galactic outflows can help to distinguish between various driving mechanisms. New broad band polarimetric observations from the CHANG-ES project of the galaxy NGC 4388 with the JVLA showed extended features in the radio polarized intensity of this Virgo galaxy. In this work we show how a jet precession model can well explain the complexity of these nuclear outflows and allows us to infer physical parameters of this ejection like velocity, inclination, period, and total time of ejection. For the first time, the direction of the outflow with respect to the line of sight is introduced into this model and compared to the observed rotation measures (RMs) of the nuclear outflow, showing good agreement between the modeled RMs and the polarization radio observations. Furthermore, this precession model, combined with polarimetric radio observations, could serve as a tool for studying the interaction of nuclear outflows with their environments.
Galactic rotation curve beyond the solar circle out to R0+10 kpc
Dambis, Andrey
We use the sim 12000 O-A-type star sample in the Galactic anticenter direction from the catalog of Monguio et al. (2013, 2014) with photometric distances (zero point calibrated via TGAS trigonometric parallaxes) and other parameters determined from Stroemgren photometry and proper motions from UCAC5 and GPS1 catalogs to analyze the run of the Galactic rotation curve and periodic variations of rotation velocity due to spiral density waves in the Galactocentric distance interval from R0 to R0+10 kpc. We find the smoothed rotation curve to be almost flat in the Galactocentric distance interval considered with a small depression of circular velocity at R0+3 kpc. When Gaia DR2 data becomes available, the analysis will be repeated including the trigonometric-parallax based recalibration of the photometric distance scale for the objects considered.
OBSERVATION OF THE SOLAR GREEN LINE OF 5303Å
Damdin, Batmunkh
Spectral lines of the solar corona were observed with the coronagraph telescope equipped with the spectrograph. The diameter of the objective is 20 cm, and the focal length is 400 cm. The spectrograph with the dispersion of 16.4Å/mm was used. Observations were conducted from 1964 to 1985. Among these lines, a very bright l5303Å of Fe XIV line was observed. For the processing of this line, the system of equations of statistical equilibrium for the Fe XIV ion of the solar corona is solved. Seven energy levels of the Fe XIV ion are considered taking into account the equations of ionized equilibrium. In the system of equations of statistical equilibrium, an attempt is made to take into account the macroscopic velocity of matter in the corona. The calculated and observed intensities in the line are compared. The Menzel coefficients of the populations of these levels are determined. From this calculation it can be seen that the populations of these levels are very much divergent in comparison with the thermodynamic equilibrium when macroscopic velocities are taken into account.
Monitoring of optical magnitudes of quasars in line with the link ICRF - Gaia CRF
Damljanovic, Goran
We collected the optical magnitudes, mostly V and R, of 47 QSOs during two and half years (period mid-2013 - end of 2015) using ground-based telescopes. These QSOs were chosen for the link ICRF - future Gaia CRF. The instruments are: two TAROT telescopes, the Telescope Joan Oro (TJO, robotic one), and 6 telescopes in the region Serbia-Bulgaria-Austria. In Serbia, it is the 60 cm ASV one (Astronomical Station Vidojevica). The 60 cm (Belogradchik ) telescope, 2 m one (Rozhen Observatory), 50/70 cm Schmidt-camera (Rozhen) and 60 cm one (Rozhen) are in Bulgaria. The 1.5 m Leopold Figl instrument is in Austria. We wanted to investigate the variability of QSOs and to compare ground-based values with Gaia G-mag. To do that we use our V and R data and suitable transformation to get the G mag of observed QSOs. The light curves of some QSOs are presented here, but it is not possible to compare our values with the Gaia DR1 ones because until now there has been no corresponding epoch for each Gaia G magnitude. Only, there is the_x005F average G value. We hope that information will exist in the next Gaia realization.
Atmospheric characterisation of directly imaged exoplanets with JWST/MIRI
Danielski, Camilla
The James Webb Space Telescope will be the next major space facility to characterise the atmosphere of exoplanets. Of particular interest is the Mid-Infrared Instrument (MIRI) which will give access, for the first time, to the 5 - 28 µm part of the spectrum of young giant exoplanets at a wide enough angular separation from their host star to be observed by direct imaging.Retrieving the precise set of parameters of these objects, such as luminosity, temperature, surface gravity, mass, and age is extremely important as it supplies information about the initial entropy of the planets and hence it allows us to shed light on their formation mechanism. The new extreme adaptive optic cameras (e.g., SPHERE, GPI) are already providing excellent constraints on these parameters, but the spectral range in which they operate is limited to near infrared so that the uncertainties are still significant. Observations taken on a longer wavelength range are mandatory for reducing them. In this context MIRI will play a key role allowing, in conjunction with shorter wavelength measurements, the exhaustive characterisation of the exoplanetary atmospheric properties.Additionally, MIRI will give us the opportunity to probe for the first time the presence of ammonia in the atmosphere of the coldest known young giants. Notice that the ammonia spectral signature is a further useful indicator of equilibrium and temperature in the planetary atmosphere.In this work we simulate the MIRI coronagraphic observations for a set of 8 known directly imaged exoplanetary systems by using the Exo-REM model. For each planet we estimated the signal-to-noise of MIRI coronagraphic observations as a function of various observing telescope conditions. Subsequently we derive the accuracy to which the exoplanetary parameters can be determined when adding MIRI observations to existing near-infrared ones. Finally we provide the significance of the ammonia detection.
Unravelling the sulphur chemistry of AGB stars
Danilovich, Taïssa
Sulphur is the tenth most abundant element in the universe and its behaviour in terms of what molecules it forms has been seen to vary for different types of AGB stars. There are clear differences across chemical types, with CS forming more readily in the circumstellar envelopes of carbon stars, while SO and SO2 have only been detected in oxygen-rich stars. However, we have also discovered differences in sulphur chemistry based on the density of the circumstellar envelope (as traced by mass-loss rate divided by expansion velocity). For example, the radial distribution of SO is drastically different between AGB stars with lower and higher density circumstellar envelopes. H2S can be found in high abundances towards higher density oxygen-rich stars, whereas SiS accounts for a significant portion of the circumstellar sulphur for higher density carbon stars. We will discuss these differences across AGB stars and what this implies for the chemical evolution of the circumstellar envelope. Studies of post-AGB stars show us that sulphur is not significantly depleted onto dust during the AGB phase, making it a good tracer of changing circumstellar chemistry across the AGB.
Partnerships in Public Outreach with Planetary Defense and Near Earth Objects
Daou, Doris
NASA and its partners maintain a watch for Near-Earth Objects (NEOs), asteroids and comets that pass within Earth’s vicinity, as part of an ongoing effort to discover, catalog, and characterize these bodies and to determine if any pose an impact threat. NASA’s Planetary Defense Coordination Office (PDCO) is responsible for:Ensuring the early detection of potentially hazardous objects (PHOs) – asteroids and comets whose orbits are predicted to bring them within 0.05 astronomical units of Earth's orbit; and of a size large enough to reach Earth’s surface – that is, greater than perhaps 30 to 50 meters;Tracking and characterizing PHOs and issuing warnings about potential impacts;Providing timely and accurate communications about PHOs; andPerforming as a lead coordination node in U.S. Government planning for response to an actual impact threat.The PDCO collaborates with other U.S. Government agencies, other national and international agencies, and astronomers around the world. The PDCO also is responsible for facilitating communications between the science community and the public should any potentially hazardous NEO be discovered. In addition, the PDCO works closely with the United Nations Office of Outer Space Affairs and the Committee on the Peaceful Uses of Outer Space to support international collaborations on Near Earth Objects. The PDCO is NASA’s representative as a leading member of the International Asteroid Warning Network (IAWN) and the Space Missions Planning Advisory Group (SMPAG), multinational endeavors endorsed by the United Nations for an international response to the NEO impact hazard, established and supported by the space-capable nations. In this paper, we provide an overview of the office’s many and varied planetary defense endeavors. In this presentation, we will discuss strategies for communicating with the Public and opportunities for more collaborations for a global and a national communications effort.
CCD photometry and light curve analysis of new discovered short period eclipsing binary system KAO-EGYPT J200046.39+054747.7
Darwish, Mohamed
New CCD photometric study is presented for the newly discovered binary system KAO-EGYPT J200046.39+054747.7._x005F Observations of the system were obtained in the V, R and I colors with the 2Kx2K CCD attached to 1.88m Kottamia optical telescope. New times of light minima and new ephemeris were obtained. The physical and geometrical parameters of the system were determined using PHOEBE 0.31. The final results show that the system is A-type WUMa with an overcontact configuration and a high fill-out ratio about 69%.The evolution status for the system along ZAMS and TAMS was also discussed.
Foreground Subtraction in redshifted 21cm Observations - Simulations and Observations
Datta, Abhirup
Observations of HI 21 cm transition line is an important and promising probe into the cosmic Dark Ages and Epoch of Reionization. Detection of this redshifted 21 cm signal is one of the key science goal for several upcoming and future low frequency radio telescopes like Hydrogen Epoch of Reionization Array (HERA), Square Kilometer Array (SKA) and Dark Ages Radio Explorer (DARE). One of the major challenges for the detection of this signal is the accuracy of the foreground source removal. At these frequencies the signal is largely dominated by bright foregrounds which are four to five orders of magnitude stronger than the redshifted signal.In addition, the ground based experiment are affected by the human generated RFI , like the FM band, and Earth’s ionosphere.The diffuse galactic synchrotron emission is expected to be the most dominant foreground. Several novel techniques have been explored already to remove bright foregrounds from both interferometric as well as total power experiments. Also, several telescopes have been used to characterise the foregrounds both in the northern and southern hemispheres. Here, we present results from both simulations with novel techniques as well as real observations with the SKA pathfinder for India, the uGMRT. In this presentation, we discuss results from a) Observations with the uGMRT in order to constrain nature of the foreground sources near the redshifted 21cm signal from Epoch of Reionization, and b) application of Artificial Neural Network to detect the faint 21cm global signal in presence of the strong foregrounds as well as imperfect instrument.
Galaxy Transformation from Flyby Encounters
Davis, Christina
Galaxy flybys are transient encounters where two halos interpenetrate and later detach. Although these encounters are surprisingly common, their dynamical effects have been largely ignored. Here, we study demographics of flybys within the Illustris Simulation to find out how common these interactions are at various halo mass ranges, and examine their dynamical properties. To characterize changes made by the flybys on the halo or the inner galaxy, we measure changes in structural properties after the encounter. Using a machine learning approach, we find which dynamical properties are important for predicting the changes in the observables.
APEX spectral scan of the M-type AGB star R Dor
De Beck, Elvire
Our current insights into the circumstellar chemistry of AGB stars are largely based on studies of carbon-rich stars and stars with high mass-loss rates. In order to expand the current molecular inventory of evolved stars we carried out a spectral scan of the nearby, oxygen-rich star R Dor, a star with a low mass-loss rate (~10-7 Msun/yr), using the APEX telescope. The spectrum of R Dor is dominated by emission lines of SO2 and the different isotopologues of SiO. We also detect CO, H2O, HCN, CN, PO, PN, SO, and tentatively TiO2, AlO, and NaCl. Sixteen out of approximately 320 spectral features remain unidentified. Among these is a strong but previously unknown maser at 354.2 GHz, which we suggest could pertain to H2SiO, silanone. With the exception of one, none of these unidentified lines are found in a similarly sensitive survey, performed with the IRAM 30m telescope, of IK Tau an oxygen-rich AGB star with a high mass-loss rate (~5x10 -6 Msun/yr).Radiative transfer models for five isotopologues of SiO (28SiO, 29SiO, 30SiO, Si17O, Si18O) provide constraints on their fractional abundance and radial extent. We derive isotopic ratios for C, O, Si, and S and estimate that, based on our results for 17O/18O, R Dor likely had an initial mass in the range 1.3-1.6 Msun, in agreement with earlier findings based on models of H2O line emission. From the presence of spectral features recurring in many of the measured thermal and maser emission lines we tentatively identify up to five kinematical components in the outflow of R Dor, indicating deviations from a smooth, spherical wind.
In search of the fundamentals of dust formation around evolved stars with the Origins Space Telescope
De Beck, Elvire
The origins Space Telescope (OST) is a mission concept for a new far-infrared space observatory developed through a community-led study sponsored by NASA in preparation for the 2020 Astronomy and Astrophysics Decadal Survey. I will introduce the OST concept, thereby focusing on two science cases related to dust around evolved stars that we developed for the proposed instruments. The first case proposes high-spectral resolution heterodyne observations of the hot, highly excited gas close to the star in order to trace the depletion of different gas-phase species and constrain the fundamental dust-condensation and growth processes. The second case proposes lower-spectral-resolution, but higher sensitivity observations of the CO ladders towards evolved stars in a number of nearby galaxies, providing unprecedented estimates of gas-mass-loss rates in these populations. Combined with sensitive observations of the dust content, this will provide the most reliable dust-to-gas ratios to date, constraining the dust-formation efficiency at different metallicities.
In search of the fundamentals of dust formation around evolved stars with the Origins Space Telescope
De Beck, Elvire
The origins Space Telescope (OST) is a mission concept for a new far-infrared space observatory developed through a community-led study sponsored by NASA in preparation for the 2020 Astronomy and Astrophysics Decadal Survey. I will introduce the OST concept, thereby focusing on two science cases related to dust around evolved stars that we developed for the proposed instruments. The first case proposes high-spectral resolution heterodyne observations of the hot, highly excited gas close to the star in order to trace the depletion of different gas-phase species and constrain the fundamental dust-condensation and growth processes. The second case proposes lower-spectral-resolution, but higher sensitivity observations of the CO ladders towards evolved stars in a number of nearby galaxies, providing unprecedented estimates of gas-mass-loss rates in these populations. Combined with sensitive observations of the dust content, this will provide the most reliable dust-to-gas ratios to date, constraining the dust-formation efficiency at different metallicities.
Unveiling the Hyades with Gaia
de Bruijne, Jos
We study the Hyades open cluster using Gaia DR2 data complemented by Hipparcos-2 data for bright stars not contained in DR2. By assuming that all cluster members move with the mean cluster velocity to within the velocity dispersion, we compare the observed and expected motions of the stars, based on Gaia DR2 astrometry and radial velocities, to determine individual cluster membership probabilities. Our membership list extends the Gaia DR1-based list at the faint end by many magnitudes. This membership forms an invaluable basis for a continued assessment of the cluster, for instance using Gaia DR2 photometric data.
Magritte: a new multidimensional accelerated general-purpose radiative transfer code
De Ceuster, Frederik
Radiative transfer plays a key role in the dynamics, the chemistry and the energy balance of all kindsof astrophysical objects. It provides the radiative pressure to drive stellar winds, it affects the chemistrythrough various photoionization and photodissociation reactions, and it can very efficiently heat or coolvery specific regions in the wind. Therefore it is essential in modelling these objects to properly accountfor all radiative processes and their interdependence. This however can be complicated by i) an intricate3D geometrical structure shielding or exposing specific regions to radiation, ii) the scattering by dust orfree electrons, and iii) the mixing in frequency space due to Doppler shifts caused by velocity gradientsin the medium. The tight coupling between radiative transfer and the often very specialized and diversedynamical and chemical models furthermore requires a modular code that can easily be integrated.To address these needs we will present Magritte: a new multidimensional accelerated general-purposeradiative transfer code. Magritte is especially designed to have a well scaling performance on variouscomputer architectures. Appended with a dedicated chemistry and thermal balance module it can self-consistently calculate the temperature field, chemical abundances and level populations. Magritte is adeterministic ray-tracing code that obtains the radiation field by solving the transfer equation along afixed set of rays originating from each grid cell. It iteratively accounts for scattering and treats the fullfrequency space. This allows us to self-consistently model the chemistry and energy balance in stellarwinds and perform synthetic observations. We will apply Margritte by post-processing snapshots ofhydrodynamical wind and bowshock simulations and will present its integration in self-consistent hydro-chemical AGB wind models.
A new perspective for understanding the Hyperbolic Meteors type after interstellar object Oumuamua discovery
DE CICCO, MARCELO A
Hyperbolic meteors are a subset of meteoroids encountering the Earth's atmosphere, which some of them could have an interstellar origin, characterized by orbital elements possessing a<0 and e>1. Hyperbolic meteors have been identified in many meteors surveys [1,2]. Maria et.al [2] calculated a total number of 484 hyperbolic orbits from 64,650 meteors within the SONOTACO catalogue [4], representing 3.28% of all orbits.There are often significant errors when estimating heliocentric velocities of a meteor due to inaccuracy of measurements, pertubation from recent close planetary encounters, and solar radiation that could generate false hyperbolic orbits in the parameters estimated. After accounting for these, there still remains a small fraction of hyperbolic solutions that could still be interstellar meteoroids, as demonstrated by Maria [2] with an upper frequency limit of 1 in 1000 meteors.After the discovery of the first confirmed extrasolar object crossing our Solar System, 1I/2017 U1 ('Oumuamua), on 2017 October 19 [3], the discussion was renewed about the presence of such objects, suggesting the previous number density may be understimated.Thus a meteor surveillance system that improves hyperbolic identification for meteoroid candidates through the use of better measurement accuracy for heliocentric velocity, will help obtain orbital information with higher reliability and be used as a way to search for signatures of parent objects with extrasolar origins. With reliable orbital data, a better estimate for the number density of interestellar objects could be achieved.[1] Hajduková, M., Kornoš, L., and Tóth, J. (2014). Frequency of hyperbolic and interstellar meteoroids. Meteoritics and Planetary Science, 49:63–68.[2] Meech, K.J., Weryck, R., Micheli, M., et al. (2017). A brief visit from a red and extremely elongated interstellar asteroid.Nature, 552:378.[3] SonotaCo. (2009). A meteor shower catalogue based on video observations in 2007–2008. WGN 37:55–62.
MULTIFRACTAL SIGNATURES OF GRAVITATIONAL WAVES DETECTED BY LIGO
de Freitas, Daniel Brito
We analyze the data from the 4 gravitational waves signals detected by LIGO through the lens of multifractal formalism using the MFDMA method, as well as shuffled and surrogate procedures. We examine the capability and robustness of this method to detect structural signatures made by different physical origins potentially present in gravitational waves. The quadratic form of multifractality spectrum demonstrates entire gravitational waves signal detected by LIGO have essentially multifractal nature and the source of this multifractality is mainly devoted to strong correlation which is another universality of these gravitational waves. However, an anomalous behavior occurs with the multifractal origin when the signal is divided into two regimes defined by the time where the variation in left side diversity takes a jump. We identified two regimes of multifractality in the strain measure of the time series by examining long memory and the presence of nonlinearities. The moment used to divide the series into two parts separates these two regimes and can be interpreted as the moment of collision between the black holes. Our main result is an empirical relationship between the variation in left side diversity and the chirp mass of each event, denoting that chirp mass is correlated to multifractal structure of gravitational wave time series. This empirical relation indicates that there exists a deterministic factor related to amount of stellar matter converted in energy when the coalescing supermassive binary black holes merger occurs.
Spectral evolution of Hydra A jets: relativistic MHD-spectral simulations
de Gouveia Dal Pino, Elisabete
We present our study of the spectral evolution of the bright jet knots and the flaring zones of the iconic radio source Hydra A. The key features we focus are that the knots with gradually increasing brightness along downstream and significantly bright flaring zones. First, we developed an axisymmetric jet-intracluster medium interaction model utilising the relativistic magnetohydrodynamic module of the publicly available code PLUTO. The parameter space of the jet and the cluster environment is set based on our previous study (Nawaz et al.) of the source. The key feature of our model is that the bright jet knots of Hydra A are formed when over-pressured supersonic jets interact with the environment through a series of reconfinement shocks. In order to produce realistic emission map, we further developed a spectral evolution code. Here, we track the evolution of a distribution of non-thermal particles both spatially due to advection along the jet and energetically due to adiabatic process and synchrotron cooling. Preliminary results of the calculation of surface brightness of the simulated Hydra A jets show that in the early stage the knots are gradually brighter due to increasing downstream magnetic pressure.
The Role of Turbulence, Gravity and Magnetic Fields in High-Mass Star Formation from HOPS Clumps
de Gouveia Dal Pino, Elisabete
We used ‘the H2O Southern Galactic Plane Survey’ (HOPS) to study dense regions of gas in the southern Galactic plane that are likely to form stars. We used HOPS NH3(1,1) data to define the positions of dense cores/ clumps of gas. Other tracers we studied from HOPS are NH3(2,2), NH3(3,3), H2O maser, H69a and HC3N. By analysing spectra of all the clumps, we measured and derived physical parameters to understand these clumps. We investigated how different physical parameters are correlated to shed some light on the physical events the clumps have experienced. Further, we performed virial analysis, investigated Larson’s relationships among HOPS clumps and mass-size distribution. We discussed the role of turbulence, gravity and magnetic fields in high-mass star formation from HOPS Clumps. The results from our current study suggest that the gravitationally bound clumps are an effect of global or Galactic scale turbulence according to Larson’s laws. Using mass-size plane we found that most of our clumps are high-mass star forming. We also observed two streams of clump-clusters in the mass-size plane - one lies in the virialised and high-mass star forming zone, the other one lies in the non-virialised low mass star forming zone.
Simultaneous Multi-band Transit Observations of Low Density Hot Jupiters
de Leon, Jerome
Observations of transiting exoplanets provide an invaluable window into the nature of exoplanet atmospheres. Characterizing an exoplanet atmosphere especially from the ground using meter-class telescopes however remain difficult. A promising method to detect broad atmospheric features is to search for Rayleigh scattering signature using multi-band photometry in the optical wavelengths. For this study, we used OAO/MuSCAT to conduct simultaneous multi-band observations of several transiting systems hosting low-density hot Jupiters including HAT-P-12b, HAT-P-14b, and WASP-21b. Our goals are (1) to improve the transit parameters of these systems, and (2) to search for broad spectral features such as Rayleigh scattering signature in the optical wavelengths. The derived transit parameters are in good agreement with previous results. Comparing the measured transit depths with the spectrum model for each planet, we found that our achieved photometric precision is not enough to robustly distinguish between the two atmospheric models. However, we found that HAT-P-12b and HAT-P-44b spectra are consistent with Rayleigh scattering. On the other hand, we found a positive slope for WASP-21b which cannot be explained by either atmospheric models. Motivated by our results, we consider future multi-epoch observations of these systems as well as search for new targets feasible for detecting broad atmospheric features using MuSCAT and MuSCAT2.
Visible spectra of ETNOs using the 10.4m Gran Telescopio Canarias
de Leon, Julia
The so-called extreme trans-Neptunian objects (ETNOs) are very distant minor bodies presenting orbits with semi-major axes larger than 150 au, and perihelion distances larger than 30 au. Due to their distance, there are less than 30 ETNOs discovered so far, the first one identified in 2000. This is a very interesting population that is currently generating some debate about the possibility on the existence of a yet-to-be-discovered planet in the outer regions of our solar system (Planet X). With the aim of shedding some light to this controversy, we initiated a spectroscopic survey in 2016 to obtain visible spectra of ETNOs using the unique capabilities of the 10.4-meter Gran Telescopio Canarias (GTC), located at the El Roque de Los Muchachos Observatory, in the island of La Palma (Spain). Here we present our most recent results and the current status of this spectroscopic survey.
Wavelet analysis applied to light curves of binary systems from CoRoT space mission
de Lira, Suzierly
Binary systems are key environments to study the fundamental properties of stars. In this work, we analyze 99 binary systems identified by the CoRoT space mission. From the study of the phase diagrams of these systems, our sample is divided into three groups: those whose systems are characterized by the variability relative to the binary eclipses; those presenting strong modulations probably due to the presence of stellar spots on the surface of star; and those whose systems have variability associated with the expansion and contraction of the surface layers. For eclipsing binary stars, phase diagrams are used to estimate the classification in regard to their morphology, based on the study of equipotential surfaces. In this context, to determine the rotation period, and to identify the presence of active regions, and to investigate if the star exhibits or not differential rotation and study stellar pulsation, we apply the wavelet procedure. The wavelet transform has been used as a powerful tool in the treatment of a large number of problems in astrophysics. Through the wavelet transform, one can perform an analysis in time-frequency light curves rich in details that contribute significantly to the study of phenomena associated with the rotation, the magnetic activity and stellar pulsations. In this work, we apply Morlet wavelet (6th order), which offers high time and frequency resolution and obtain local (energy distribution of the signal) and global (time integration of local map) wavelet power spectra. Using the wavelet analysis, we identify thirteen systems with periodicities related to the rotational modulation, besides the beating pattern signature in the local wavelet map of five pulsating stars over the entire time span.
Studying dwarf galaxies up to very high redshift using gamma-ray bursts
de Ugarte Postigo, Antonio
Long duration gamma-ray burst are produced by the explosive death of short lived, very massive stars. Thanks to their extreme luminosities, they can be detected at basically any redshift (being the spectroscopic record z=8.2). Consequently, they are good tracers of the star formation throughout the Universe’s history. They can be detected and their redshifts measured independent of their host luminosity. In fact, many of the hosts of GRBs have been found to be dwarf galaxies that would have been missed in regular galaxy surveys. In this sense, GRBs are one of the few and most efficient methods of studying dwarf galaxies at very high redshift.Here I will present a study of the properties of the galaxies in which gamma-ray bursts are produced. I will do so from different perspectives: From their inside, through absorption spectroscopy, which allows us to measure the composition, dynamics and structure of cold gas within the galaxy. From their emission spectra, when the galaxies are bright enough (typically up to z=3.5), which allows us to use strong line diagnostics. From spectral energy distribution studies, which allows us to determine host galaxy properties up to higher redshifts (up to z~5).The datasets used for this work include the SHOALS sample of GRB host galaxies (the most extensive sample to date) and the GRB spectra stored in the GRBSpec database that we manage, including data from FORS and X-shooter at the 4x8.2m VLT (Chile) and OSIRIS at the 10.4m GTC (Spain).
The K-band (24 GHz) Celestial Reference Frame
de Witt, Aletha
A K-band (24 GHz) celestial reference frame of 825 sources covering the full sky has been constructed using 461K observations from 55 observing sessions from the VLBA and HartRAO-Hobart. Observations at K-band are motivated by their ability to access more compact source morphology and reduced core shift relative to observations at the historically standard S/X-band (2.3/8.4 GHz). The factor of three increase in interferometer resolution at K-band should resolve out source structure which is a concern for AGN centroid stability. K-band median precision is now better than the ICRF-2 precision (for common sources) thereby raising the question of which frame is more accurate. The accuracy of the K CRF is quantified by comparison of 707 sources in common with the current S/X-band producing wRMS agreement of 86 micro-arcseconds as in RA cos(Dec) and 123 micro-arcseconds in Dec. There is evidence for systematic errors at the ~100 micro-arcsecond level. The success of the Gaia optical astrometric satellite motivates work to tie the radio and optical frames. K-band data and Gaia Data Release-2 data give a frame tie precision of ~15 micro-arcsecond (1-sigma, per 3-D rotation component). If K-band precision can be pushed below ~20-30 micro-arcsecond, the K frame has potential to produce a tie to Gaia that is superior to S/X due to reduced astrophysical systematics at K relative to S/X.
Gaseous metal oxides and hydroxides tracing the formation of AGB dust grains.
Decin, Leen
The gas-phase elements Ca, Fe, Mg, Si and Ti are depleted w.r.t. the solar abundances in diffuse clouds. The formation of metal oxides and metal hydroxides and of dust species is suggested as major cause for this depletion. We have used the ALMA telescope to perform a high-sensitivity scan between 335 and 362 GHz of the stellar wind of two oxygen-rich Asymptotic Giant Branch (AGB) stars, IK Tau and R Dor. A particular aim of the observing programme was to detect metal oxides and metal hydroxides (AlO, AlOH, FeO, MgO, MgOH), some of which are thought to be direct precursors of dust nucleation and growth. During this presentation, we focus on two aspects. We report on the potential first detection of FeO (v=0, Omega=4, J=11-10) in the wind of an AGB star (being R Dor) and discuss its formation and depletion mechanisms. Secondly, we show that for both stars, only ~2% of aluminium is locked up in AlO, AlOH, and AlCl, and that each of these species is detected well beyond the main dust condensation region. This proves that the aluminium dust condensation is not 100% efficient. We will discuss how the current proposed scenario of aluminium dust condensation poses a challenge if one wishes to explain both the dust spectral features in the spectral energy distribution(SED), in interferometric data, and in polarized light signal. We postulate that large gas-phase (Al2O3)n-clusters (n>34) can be the potential agents of the broad 11 micron feature in the SED and interferometric data and we explain how these large clusters can be formed.
Alien visitors rule cosmic makeup
Decin, Leen
After decades of failures and misunderstandings, scientists have solved a cosmic riddle — what happens to the tons of dust particles that hit the Earth every day but seldom if ever get discovered in the places that humans know best, like buildings and parking lots, sidewalks and park benches. The answer? Nothing. Look harder. The tiny flecks are everywhere, all over the roof. The morphology of these flecks - micrometeorites - is a first hint of their extraterrestrial origin, the determination of their chemical makeup is the decisive making body. But how is that cosmic dust formed? What important clues on stellar winds are hidden in these extraterrestrial flecks? What do these microscopic samples supported by astronomical observations tell us about the future evolution of our own Sun? In this talk, I will discuss how interdisciplinary research linking astronomy and chemistry – `astrochemistry’ – can reveal the true formation pathways of these little grains.
The brightness variations of Boyajian's star: Dusty planetesimals, temperature variations, or something else?
Deeg, Hans
KIC 8462852, also known as the Boyajian's star, was observed by the Kepler mission during 4 years. During that time, this star underwent several events of strong brightness variations that are unlike that of any other known astronomical object. Since 2017, an intense ground-based observing campaign has been under way to closely survey this target for further brightness variations. The coverage of several minor such variations from both multicolor photometry and spectrophotometry showed that these events have a color-signature. This observation is compatible with the hypothesis by Neslušan & Budaj of a pool of dusty planetesimals that may occasionally pass close to the star. Their optically thin dust shroud might then generate the observed colors. However, while current observations support this scenario, they do not prove it. Alternative explanations for the star’s behavior will be revised, and in particular, variations in the temperature of the stellar surface will be evaluated for their compatibility with the observations. Furthermore, an update on the observing campaign of Boyajian’s star will be given, possibly with input from new data acquired in the first half of 2018.
Internal dynamics of dwarfs around the Milky Way
del Pino, Andres
Dwarf galaxies in the Local Group have been consistently studied over almost a century now. Numerous data have been collected about their stellar content, line-of-sight velocities, and many of their internal structural parameters. However, it has not been until the last decade when the tangential velocities of their stars (proper motions) have been also within reach. For the moment, only the unparalleled astrometric precision of the Hubble Space Telescope has allowed to derive the bulk proper motions of some dwarf galaxies, providing the appropriate rest frame for analyzing their internal dynamics. With the advent of GAIA, new data is becoming available, opening the door to state-of-the-art dynamical studies. In this talk we will present new internal dynamics results for dwarfs making use of these recent observations and novel analysis techniques.
UX Orionis phenomenon in protoplanetary disks seen face-on
Demidova, Tatiana
The direct observations of protoplanetary disks showed that many images of the disks had a large-scale asymmetry. Such an asymmetry may be observed even if a protoplanetary disk is seen face-on. The inhomogeneous distribution of the matter or anistropic illumination of the disk surface can be responsible for the asymmetry. The perturbations in the disk can be caused by the orbital motion of a massive planet or substellar companion. Streamsofmatter, densitywaves and vortixes may arise in the disk and affect the photometric properties of the disk. For instance, the variable circumstellar extinction is produced in the disks seen edge-on or at the small angle to the line of sight (UX Ori phenomenon). Theinnerpartofthediskmay bewarpedbecauseoftheinclinationofthecompanionorbittothediskplane. The warp prevents the spread of stellar radiation in some direction. The effect can be observed in optical and NIRspectrum because only the surface layer heats up and cools quickly enough for the rotating disk.To research the phenomena we consider the model of an young star with a protoplanetary disk and a low-mass companion (q = M1:M2= 0.1), which orbit is inclined to the disk plane. Thesetofthemodelsofsuchasystem was calculated forthewiderangeoftheparametersbySPHmethod, with taking into account the temperature distribution along the radius and height. On the basis of hydrodynamic modelswe simulated the optical and NIRimagesof protoplanetary disks seen face-on. The simulations show the outer part of the disk has the bright and shadowed domains, located not symmetrical with respect to the line of nodes. The shape and size of the shadow depend on the model parameters. For all models the bright and dark domains do not follow the companion, but make small amplitude oscillations with respect to the some direction. The properties of the described model open new opportunities of searching low-mass companions in the vicinity of young stars.
Resonant multi-lane patterns in circumbinary young debris disks
Demidova, Tatiana
Formation of resonant multi-lane patterns in circumbinary young debris disks with planets is considered in a set of representative massively simulated models. We find that the long term-stable resonant patterns are generically formed, shepherded by embedded planets. The patterns are multi-lane, i.e., they consist of several concentric rings. Statistical dependences of their parameters on the planetary orbital parameters are recovered. Relevant additional massive simulations of planetesimal disks in systems with parameters of Kepler-16, Kepler-34, and Kepler-35 are accomplished and described. We find that co-orbital patterns generically form in systems with moderate orbital eccentricities of the binary's and planetary orbits (like in Kepler-16 and 35 cases). We argue that any observational identification of characteristic resonant ring-like patterns in disks of the considered class may betray presence of planets shepherding the patterns. This work was supported by the Russian Foundation for Basic Research (projects Nos. 17-02-00028-a)
Water delivery to the TRAPPIST-1 planets
Dencs, Zoltan
Three of the seven rocky planets (e, f, and g) in TRAPPIST-1 system orbit in the habitable zone of the host star. As a result, water can be in liquid state at their surface being essential for life. Recent studies suggest that these planets began to form beyond the snowline, where they could gather water. However, water frozen in asteroids may be lost due to frequent collisions during the formation of planets. A potential water delivery event resembling to the late heavy bombardment in the Solar System, can reproduce the water reservoir on these planets. To simulate this water delivery process, we ran a series of N-body simulations incorporating the seven known planets and a putative planet whose mass are in the range of 5 M_Earth-50 M_Earth orbiting beyond the snowline embedded in a water-rich asteroid disc. We used our own developed GPU-based N-body integrator, HIPERION to model the dynamics of half a million asteroids interacting with the expanded planetary system. To test long-term stability of the expanded system, we applied IAS15 integrator for 10^8(10^7) orbits of the innermost(outermost) known planet. Expanded systems with the putative planet orbiting beyond 0.17 au are all found to be stable. We found that the longevity of the accretion events occurring on planets increases with the orbital distance of the accreting planet. The amount of asteroid accreted also increases with the accreting planet's orbital distance and decreases with the distance and orbital inclination of the perturber. The highest accreted-to-initial number of asteroids measured in stable systems is maximum 5% in total, 1.5% for the habitable planets, and peaks at 3.5% for TRAPPIST-1h, supporting the idea that it can host significant amount of water. By applying a plausible assumption for the water mass contained by the unperturbed asteroid belt, the amount of water accreted by TRAPPIST-1h can reach several 10% of planet mass.
Observational evidence that asteroids formed big
Dermott, Stanley
A century ago Hirayama discovered the clustering of asteroid orbital elements, revealing that some asteroids are in families originating from the disruption of a few large primordial bodies. However, the asteroids now classified as family members constitute a minority of the asteroids in the main belt. Here we show that the non-family asteroids in the inner belt have orbital inclinations that increase and orbital eccentricities that decrease with increasing asteroid size. These correlations can be accounted for if both the non-family and the family asteroids originate from the disruption of a small number of large asteroids. Separating the non-family asteroids into halo and non-halo asteroids allows us to estimate that 85% of all the asteroids in the inner main belt originate from the Flora, Vesta, Nysa, Polana and Eulalia families with the remaining 15% originating from either the same families or, more likely, a few ghost families. These new results imply that we must seek explanations for the differing characteristics of the various meteorite groups and the near-Earth asteroids in the evolutionary histories of a few, large, precursor bodies. These results also support the model that asteroids formed big through the gravitational collapse of material in a protoplanetary disk.
How Sensitive are Global Coronal Magnetic Fields to Active Regions Emerging in Different Locations?
DeRosa, Marc
Global coronal magnetic field models are used as the basis for modeling the structure and dynamics in the heliosphere, including those associated with forecasting space weather. However, the coronal field models depend (critically, sometimes) on the photospheric magnetic maps used as lower boundary conditions, and the lack of contemporaneous photospheric field observations of all 360 degrees of longitude and the polar fields represents a significant source of uncertainty. The study presented here examines how often, and by how much, the coronal field models are affected by the emergence of new bipolar active regions, by inserting idealized bipolar active regions into existing synoptic charts and assessing the resulting changes in potential field models of the coronal field. It is found that flux emerging at some longitudes causes a greater amount of disruption than at others, and this effect is especially pronounced when the dipole moment of the emergent region is out of alignment with the pre-existing large-scale configuration.
The contrast performance of the NIRSpec micro shutters and its impact on integral field observations
Deshpande, Anurag
The Near Infrared Spectrograph (NIRSpec) instrument is one of the four scientific instruments aboard the James Webb Space Telescope (JWST). NIRSpec can be operated in Multi-Object Spectroscopy (MOS), Fixed-slit Spectroscopy (FS), and Integral Field Spectroscopy (IFS) modes; with spectral resolutions from 100 to 2700. Two of these modes, MOS and IFS, share the same detector real estate and are mutually exclusive. Consequently, the micro-shutters (MS) used to select targets in MOS mode must all be closed when observing in IFS mode. However, due to the finite contrast of the MS, there is still some amount of light passing through them even when they are closed. This light creates a low, but significant, parasitic signal, which can affect IFS observations. Here, we present the work carried out to study and model this signal. Firstly, we show the results of an analysis to quantify its levels for all NIRSpec spectral bands and resolution powers. We also show how these results were combined with signal to noise considerations to help consolidate the observation strategy for the IFS mode and to generate guidelines for designing observations. In a second part, we report on the results of our work to model and subtract this signal. We describe the model itself, its derivation, and its accuracy as determined by applying it to ground test data.
The International Astronomical Union and the Arab World: Bridging Communities in Science and Outreach
Determann, Jörg Matthias
Over the last hundred years, the International Astronomical Union has played a crucial role in bridging communities and developing space science and outreach in the Arab world. Algeria was, as part of France, a founding member of the IAU in 1919. Egypt joined the Union in 1925, and other Arab countries followed suit in the second half of the 20th century. Lebanon first joined in 1954, Iraq in 1976, and Morocco and Saudi Arabia in 1988. Individual IAU members were also important, especially for countries such as Iraq, which at times were at the margins of the international scientific community. In 2010, no Iraqi institution, but seven individual astronomers were still members of the IAU. Especially active was Athem Alsabti, who had first joined the union in 1976. After leaving Iraq during the late 1990s, he became part of the IAU’s Program Group for the World-Wide Development of Astronomy. In honour of his work, the IAU named the asteroid 10478 Alsabti after him in 2001. The collaboration between IAU members on different continents has been essential for outreach and the training of astronomers in the Arab world. Zdenek Kopal at the University of Manchester attracted many students from Egypt, Iraq, and Libya between 1950s and 1980s. Kopal and his colleagues initiated the International Schools for Young Astronomers, which have been supported by the IAU. In 1967, the University of Manchester hosted the first of these schools with twelve students, including two from Egypt. Subsequently, Egypt and Morocco each hosted two International Schools for Young Astronomers between 1981 and 2004. While military conflicts and light pollution have formed significant challenges, increasing numbers of science museums, booming amateur clubs and arid mountains in the region provide opportunities for future outreach. Collaboration with local science fiction societies could further contribute to fascination for astronomy among people with limited access to planetaria or telescopes.
The CHANG-ES view of NGC 4666
Dettmar, Ralf-Juergen
We present CHANG-ES VLA data of the nearby superwind and starburst edge-on spiral galaxy NGC 4666, which is a member of a small group of galaxies in a distance of 27.5 Mpc. The observations were carried out at two different radio frequencies (1.5 GHz and 6 GHz) and with all polarization products. With these data the magnetic field strength as well as the magnetic field configuration in the halo and the disk is investigated. Further analysis of the rotation measure (RM) values along the disk of the galaxy (from RM-synthesis) reveals reversing magnetic fields within the magnetized disk. To our knowledg this is the first report of a field reversal in the disk of an external galaxy.
Comparing Hubble Space Telescope's ACS/WFC and WFC3/UVIS photometry
Deustua, Susana
A study was undertaken to compare the Hubble Space Telescope's ACS Wide Field Camera (WFC) photometry to that of the WFC3 UVIS imaging channel in eight similarly named passbands corresponding to the broadband filters F435W (ACS/WFC), F438W (WFC3/UVIS), F475W, F555W, F606W, F625W, F775W, F814W and F850LP. We present the results of this study, which may be of interest for science programs that use both ACS and WFC3. The consistency of the photometric calibration of ACS/WFC and WFC3/UVIS is within +/- 1%. Comparing the ACS/WFC to WFC3/UVIS mean flux for stars having a range of spectral types shows a color dependence for all filters except for F814W.
Origins of small NEO impactors
Devillepoix, Hadrien
Understanding the asteroid analogues to meteorite types is a major objective in planetary science over the next decade. Fireball networks across the world endeavour to deliver fresh meteorite samples with known pre-impact orbits by observing the luminous entries in the atmosphere. Although these pre-entry orbits can be reasonably accurately measured, they cannot directly be traced back to asteroid parent families, as long stochastic processes are involved in the delivery mechanism.Several studies have modeled the delivery of meteorites to Earth by studying the distribution of large Near-Earth asteroids (discovered and characterised by telescopes), and infer what source regions particular meteorites are more likely to come from, by forward propagating clones of these large NEO populations. This method has issues because the NEO model used is mass dependent. For instance, LL chondrites represent only 8% of falls whereas Near-Earth space is thought to be composed of over 30% LL chondrite-type asteroids. Granvik et. al. (2016) developed a new size dependent NEO model, but it is limited by what telescopes can detect, and is far from covering decimetre-scale, the typical size of meteorite dropping meteoroids.To better understand these size dependent processes, we propose to study the origin of decimetre-scale NEO material, through a purely data-based approach. We integrate backwards clones of the meteoroid pre-entry orbits, and calculate the provenance probabilities from the source regions. Such results are statistical in nature, therefore a large meteoroid collecting network area is required.The Desert Fireball Network has been built over the past 3 years to become the largest fireball network in the world, and has already recovered 3 meteorites with calculated orbits (out of the ~30 overall). Thanks to its collaborations with 13 institutions in 6 countries, it will soon cover 2% of the Earth with a distributed network of 200 autonomous observatories.
Estimating the mass and energy of primary cosmic rays above 100 TeV
Dey, Rajat K
This analysis aims to determine the mass composition and energy of cosmic rays at energies above 100 TeV based on the lateral distribution of extensive air showers. Here, we propose quite a few air shower observables for reconstructing the mass and energy of the primary particles. The present reconstruction uses a detailed Monte Carlo simulation for cosmic ray induced air showers in KASCADE and NBU types surface arrays of particle detectors. Some of the observables obtained from the analysis of simulated data are used to infer the nature of the primary particles via comparisons to KASCADE and/or NBU data. It is expected that the determination of primary energy of a cosmic-ray shower may deliver a better accuracy compared to standalone analysis using shower size or S600 or S500 or Npe etc, owing to strong fluctuations in the EAS development. Moreover, the present study may enable to discriminate between hadronic cosmic rays and primary gamma rays, and to measure the cosmic ray all-particle energy spectrum.
Leptonic origin of TeV-PeV neutrinos and gamma rays in newly born millisecond pulsars
Dey, Rajat K
Newly born millisecond pulsars could be treated as efficient accelerators of electrons. In the framework of the Langmuir-Landau-Centrifugal Drive (LLCD); a two step process, it was found that electrons in the pulsar magnetosphere may gain enormous amount of energy (EeV) from its spin-down energy. In the present work we concentrate on the aftermath of the acceleration era in the star's magnetosphere where these EeV electrons/positrons might produce PeV neutrinos via various reaction channels. We also expect gamma ray events if we investigate some of the effects of the electromagnetic radiation from these EeV electrons. Here, we estimate PeV neutrinos and gamma ray fluxes, with a view to explain the PeV neutrino events detected in IceCube and thereby settle down their possible origins.
Stacking analysis of the HERITAGE data to statistically study far-IR dust emission from evolved stars
Dharmawardena, Thavisha
By fitting the mid-IR SEDs of evolved stars in the LMC and SMC with GRAMS grid of radiative transfer models (Sargent et al., 2011; Srinivasan et al., 2011), Riebel et al., 2012 and Srinivasan et al., 2016 has estimated the dust budget in these galaxies. These fits may not account for cold dust, emitting in the far-IR, and may thus underestimate the dust-production rate (DPR). Herschel data can be analysed for cold dust emission in excess of the predictions from fits to the mid-IR SEDs (Boyer et al., 2012). However, due to confusion with background emission from the interstellar medium (ISM) and Herschel’s limited spatial resolution only 35 of the tens of thousands of Spitzer-identified evolved stars in the LMC and SMC have identified counterparts in the Herschel HERITAGE point source catalogue (Jones et al., 2015).In order to determine the presence of a cold dust component in a statistical sense, we revisit the Herschel HERITAGE data of the LMC and SMC using a method of image stacking similar to what is commonly used in extragalactic observational studies (e.g. Schreiber et al., 2015). We improve the signal-to-noise of the cold dust emission by using postage-stamp sized chunks of the Herschel HERITAGE maps and co-adds the cutouts to derive the photometric flux at each wavelength for the sources included in the co-added stack.Results of the stacking analysis can be used to detect the presence of an additional dust component, and therefore refine the dust budget estimates of Riebel et al., 2012 and Srinivasan et al., 2016 for the same sample. They will also allow us to test the predictions of FIR flux by the GRAMS models. The SED of the average additional cold dust component can then be analysed to adjust the average dust-production rate.With the tens of thousands of evolved stars at our disposal, we can divide the sample into sub-categories, such as by chemistry, mass-loss rates, initial mass for which to investigate the presence of cold dust.
Bringing billions together under the Sun
Dhurde, Samir
Networking together astronomy communicators and the more than a billion people in the country is a major task in the role of the IAU NOC India. We present the activities that were conducted in India during the last year. Since India is a tropical country, sharing climactic as well as social conditions with about 100 countries close to the Tropics, accounting for 40% of the world's population, the activities we present, could thus be relevant to many others. In particular we focus on the "Zero Shadow Day" activity which brings forth amazing and enabling outreach possibilities on the days when the sun’s rays are perpendicular at noon. Being inexpensive and appealing to all age groups, these provides a good chance to talk about astronomy and do some daytime activities even in remote places. The sharing and suggestions would appeal to astronomy communicators from many parts of the world, to come together under one simple, but not commonly celebrated event.
Ultra Diffuse Galaxies: a formation scenario
di cintio, arianna
A large number of Ultra-Diffuse Galaxies (UDGs) has been detected over the past few years, both in clusters and in isolation. UDGs have stellar masses typical of dwarf galaxies but effective radii of Milky Way-sized objects, and their origin remains puzzling.Using hydrodynamical zoom-in simulations from the NIHAO project we show that UDGs form naturally in dwarf-mass haloes, as a result of episodic gas outflows associated with star formation. The simulated UDGs live in isolated haloes of masses 1010-11Msun, have stellar masses of 107-8.5Msun, effective radii larger than 1 kpc and dark matter cores. Remarkably, they have a non-negligible HI gas mass of 107-9Msun, which correlates with the extent of the galaxy.Gas availability is crucial to the internal processes that form UDGs: feedback driven gas outflows, and subsequent dark matter and stellar expansion, are the key to reproduce faint, yet unusually extended, galaxies.This scenario implies that UDGs represent a dwarf population of low surface brightness galaxies and that they should exist in the field.Several predictions and comparisons with stat-of-the-art observational data will be presented. Amongst other, we will show that the largest isolated UDGs sistematically contain more HI gas than less extended dwarfs of similar M*, corroborating our proposed formation scenario.
Evolved stars of Local Group galaxies IC10 And IC1613
Di Criscienzo, MArcella
Evolved stars are drivers of galactic chemical enrichment and evolution. In particular, asymptotic giant branch (AGB) stars play a crucial role in the determination of the recent star formation history. Being main dust manufacturers, they are also essential to understand the stellar contribute to the dust budget of the environment where they form. A multi-wavelenght approach, that includes near and mid-IR infrared observations to detect the dust-enshrouded AGB stars, is fundamental to achive these goals. Currently, resolved mid-infrared stellar population studies of galaxies are limited to nearby galaxies (d<1.5Mpc). James Webb Space Telescope (JWST) will revolutionize this field by vastly expanding the volume over which this kind of studies can be conducted. Waiting for the launch of JWST, our group has started a project on the interpretation of evolved stars in the DUSTiNGs targets (Boyer et al., 2015) starting with the dwarf galaxies IC10 and IC1613. In this talk I will show how our models of thermally-pulsing AGB stars, that also describe the dust-formation process in the wind, are able not only to characterize in term of mass and metallicities their AGB population but also to retrive important information about their star formation histories and dust production rate.
A joint image-visibility study of the Sunyaev-Zeldovich effect at high resolution
Di Mascolo, Luca
The Sunyaev-Zeldovich effect (SZE) represents an ideal tool for studying the formation of galaxy clusters. First of all, it is indeed well-known that, due to the redshift-independence of the SZE surface brightness, it can provide an exceptional view on large-scale structures at high redshifts. Second, the SZE signal is sensitive to different thermodynamic properties of the hot electrons within clusters than X-ray emissions. A comparison of SZE and X-ray observations can thus provide a wealth of information on the dynamical and thermal state of the intracluster medium. This is the result of the numerous merger events and accretions of substructure a galaxy cluster has undergone during its growth, and its study can give an insight into the cluster formation history.Nevertheless, such investigation requires a combination of high-resolution, high-sensitivity data and accurate modeling of galaxy cluster morphology. To date, ALMA is the only instrument capable of providing measurements of the SZE signal with an angular resolution of ~5 arcsec. However, imaging of interferometric data may be strongly biased by the specific choice of the deconvolution technique. Moreover, the determination of a transfer function (instrument response) for accounting for large-scale filtering and missing flux is a non-trivial task. In order to avoid such issues, it is then more advisable to work directly in visibility space. On the other hand, bolometric data can complement interferometric measurements by adding information on the large-scale properties of galaxy clusters.For these reasons, we developed a joint image-visibility MCMC modeling pipeline for the determination of 2D parametric models of cluster SZE signal. As a test case, we applied this tool to the well-known galaxy cluster RX J1347.5-1145. I will discuss the recent results from the joint analysis of Planck, BOLOCAM, MUSTANG-2, ACA and ALMA data.
The new age of big data astronomy… digital assets!
Diamond, Joseph
The Square Kilometre Array (SKA) project is an international effort involving 20 countries on 5 continents to build the world’s largest radio telescope, and with that comes its own challenges of processing, storing and distributing large amounts of astronomical data. However, a smaller challenge of its own is coordinating a global communications effort, and the management of the digital assets a global, distributed project like the SKA produces. How to obtain assets from different countries and partners? How to ensure they meet the required high-level quality? How and where to store them? How to share them with partners around the world and distribute them to various audiences?Building on the theme of how organisations develop and coordinate astronomy information and the dissemination of their resources, this talk focuses on the increasing need for communications teams to adopt Digital Asset Management (DAM) systems to gather and manage increasing amounts of diverse resources and media products and distribute them to relevant stakeholder groups. DAM systems can also help streamline workflows and improve the communications & efficiency of distributed communications teams to maximise productivity.
Exploring data multimodally
Diaz, Wanda
The Universe is a vast ocean of Bigdata where we are deeply submerged. In this poster we present newly developed multimodal perception techniques for the exploration of big data. Techniques were applied by a single user to measurements from Ulyses, and a constellation of satellites following different shocks from the Sun to Earth. This poster also presents the next step consisting of carefully designed perception experiments to test effectiveness of techniques on variety of users.
Effective and Simple Hand Held Multimodal Tool to Monitor Infrared Emissions
Diaz Merced, Wanda
Interpretation of the atmospheric emission data based on infrared (IR) absorptions in laboratory spectrophotometers fails to account for the very long path that radiation from the planet surface must take to reach the top of the atmosphere. The photons (and other particles and molecules absorbed by CO2) emitted from the Earth surface never reach the top of the atmosphere. We may say the absorption is saturated. We have developed a low cost device consisting of an arduino with a IR sensor to introduce the citizen scientist to these concepts. Mainly this device intendes to provide an effective low cost method for everyone to engage in the scientific processes inherent in the science of astronomy. Taking advantage of the total solar eclipse our technique was piloted from two different locations inside the totality path in Kentucky United States. We are hoping to create a way that will help to listen and compare for time periodicities in the local IR emission brightness using this very simple device (~short-period oscillations in intensity). Using this low cost device could help to introduce the citizen scientist to the exploration of the state of our local low altitude surface atmosphere ( low altitude Troposphere). We present an adaptation of the classical FFT to the screen reader capability , analog to the sound conversion from time domain to frequency domain by the ear the learner may use classical FFT to find periods have an idea of the energy content of our near surface altitude troposphere. This poster presents the low cost device designed at the Harvard University, the techniques employed to gather the data at the Kentucky school for the blind and at Morehead State University , and testing performed during the eclipse from the Athlone School for the blind in South Africa.
Kinematics of Quenched Dwarf Galaxies: Differentiating Quenching Mechanisms Across Environments
Dickey, Claire
While it has long been understood that both environmental and internal processes play important roles in quenching galaxies, the relative importance of the two categories remain poorly understood, particularly for low-mass galaxies. In this work, we look for signatures of external vs internal quenching of low-mass quenched dwarf galaxies in isolation and cluster environments by examining stellar kinematics derived from high-resolution optical spectroscopy. In particular, we investigate the lowest-mass quenched galaxies which exist in isolation (M* = 10^(9-9.5) M_sun; Geha et al., 2012). These galaxies may represent the lowest stellar mass population in which internal feedback effects are still able to quench galaxies. We compare this sample to corresponding quenched galaxies in the Virgo Cluster within our mass range of interest, as well as a sample of low-mass star forming galaxies in isolation. All 40 galaxies in our study were observed with the Keck/ESI spectrograph, making this a uniquely self-consistent dataset across a range of environments and star formation rates. We find that isolated quenched and star forming galaxies show kinematics consistent with being rotationally-supported, while cluster galaxies are primarily dominated by random motions. Based on the existence of distinct kinematic signatures of isolated vs cluster dwarf galaxies, we constrain the nature and efficacy of feedback processes for quenching galaxies at low stellar masses.
Synoptic maps of high-latitude filaments for solar cycle 24 observed by the Chromospheric Telescope
Diercke, Andrea
The Chromospheric Telescope (ChroTel) at the Observatorio del Teide, Tenerife, Spain observes the entire solar disk since 2011 in three different chromospheric wavelengths: Ha, Ca II line, and He I. The instrument records full-disk images of the Sun every three minutes in these different spectral ranges. In addition, the telescope records filtergrams in He I, scanning the line at seven different wavelength points so that chromospheric Doppler velocities can be measured. Although, ChroTel does not observe the Sun daily, a long data set of 746 days (2012-2016) with observations is publicly available in the data archive. This covers the rising and decaying phase of solar cycle 24. We started analyzing the ChroTel time-series and created synoptic maps of the entire observational period in all three wavelength bands. The synoptic maps contain, among others, information about the number, location, area, and orientation of the filaments. The number and the location of filaments follows the solar activity cycle. We focus in our study on large-scale filaments, polar crown filaments, and high-latitude filaments and their propagation towards the pole, which is known as 'dash-to-the-pole'. Furthermore, other properties of the filament can be determined from this data set such as length, width, and lifetime, which can be statistically analyzed throughout the cycle.
Stark broadening data for post AGB and AGB stars - STARK-B Database, a node of Virtual Atomic and Molecular Data Center (VAMDC)
Dimitrijevic, Milan S.
Stark broadening of spectral lines is produced by the perturbation of emitting/absorbing atom or ion by interactions with surrounding charged particles. The corresponding Stark broadening parameters, line width and shift, are needed for different applications in Astrophysics (e.g., for stellar atmospheres modelling, analyzis and synthesis of stellar spectra, radiative transfer calculations, abundance determination...), Physics and for industrial plasmas. In atmospheres of hot, massive post AGB stars this is the principal pressure broadening mechanism. It can be of interest and for AGB stars, for subphotospheric layers investigation and modelling. In the case of analysis and synthesis of spectral lines with large principal quantum number, Stark broadening could be non negligible even in deep layers of atmospheres of AGB stars. If needed, Stark broadening parameters can be found in STARK-B database (http://stark-b.obspm.fr), a collaborative project between the "Laboratoire d'Etude du Rayonnement et de la matière en Astrophysique'' (LERMA) of the Paris Observatory and CNRS, and the Astronomical Observatory of Belgrade. We will describe STARK-B as database is on 20. August 2018 . It contains widths and shifts of isolated lines of atoms and ions due to electron and ion impacts (Stark broadening parameters) determined theoretically in more than 150 papers by Dimitrijević, Sahal-Bréchot, and colleagues. We note that STARK-B is one of 33 databases with different atomic and molecular data needed for stellar plasma investigation and modelling within Virtual Atomic and Molecular Data Center (VAMDC – www.vamdc.eu), which will be also described shortly.
Monitoring Solar Activity Variations with High-Resolution Sun-as-a-star Spectroscopy
Dineva, Ekaterina
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) is a state-of-the-art, thermally stabilized, fiber-fed, high-resolution spectrograph for the Large Binocular Telescope (LBT) at Mt. Graham, Arizona. Typically theLBT with its large light-gathering power feeds starlight to PEPSI. However, the spectrograph can also be fed with sunlight from the Solar Disk-Integrated (SDI) telescope. Synoptic solar observations with PEPSI/SDI produce daily spectra with high signal-to-noise ratio, providing access to unprecedented, quasi-continuous, long-term, disk-integrated spectra of the Sun with high spectral and temporal resolution. The observed spectra contain a multitude of photospheric and chromospheric spectral lines in the wavelength range of 380-910 nm. We develop tools to monitor and study solar activity on different time-scales ranging from daily changes, over periods related to solar rotation, to annual and decadal trends. Strong chromospheric absorption lines, like the Ca II K & H lines, are powerful diagnostic tools for solar activity studies, since they trace the variations of the solar magnetic field. Currently, we are developing a data pipeline for extraction, calibration, and analysis of the PEPSI/SDI data. We compare the SDI data with daily spectra from the Integrated Sunlight Spectrometer (ISS), which is part of the NSO Synoptic Optical Long-Term Investigation of the Sun (SOLIS) facility. This allows us to validate SDI data quality and precision. We present result for the Ca II K & H lines, including details of the wavelength and flux calibration. First results combined with Ca II K line activity index are discussed in the context of synoptic full-disk images and magnetograms.
Sun-as-a-star Observations of the 2017 August 21 Solar Eclipse
Dineva, Ekaterina
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) is a state-of-the-art, thermally stabilized, fiber-fed, high-resolution spectrograph for Large Binocular Telescope (LBT) at Mt. Graham, Arizona. During day-time the instrument is fed with sunlight from the 10-millimeter aperture, fully automated, binocular Solar Disk-Integrated (SDI) telescope. The observed Sun-as-a-star spectra contain a multitude of photospheric and chromospheric spectral lines in the wavelength range of 380 – 910 nm. One of the advantages of PEPSI is that solar spectra are recorded in the exactly same manner as nigh-time targets. Thus, we can compare solar and stellar spectra directly.PEPSI/SDI recorded 116 Sun-as-a-star spectra during the 2017 August 21 solar eclipse. The maximum obscuration observed was 61.6% . The spectra were taken with a spectral resolution R ˜ 250,000, and an exposure time of 0.3s. The high-spectral resolution enables us studying subtle changes in the spectra while the Moon passes the solar disk. The Sun-as-a-star spectra are affected by changing contributions due to limb darkening and the solar differential rotation profile, and to a lesser extend by the presence of active regions on the solar surface. We investigate the temporal evolution of the chromospheric Na D1 and D2 lines, derive bisector yielding height-dependent information, and compare observations with synthetic line profiles.
Evolution of the broadband spectrum of accreting millisecond X-ray pulsar SAX J1808.4-3658 during its 2005 outburst
Ding, Guoqiang
Using the data the from RXTE satellite, we investigate the evolution of the broadband spectra (3-200 keV) of accreting millisecond X-ray pulsar (AMXP) during its 2005 outburst. With a multicomponent model consisting of a blackbody, a thermally comptonized component, a relativistic disk emission line, a multicolour disk blackbody component, and a power law, the spectra are fit statistically well. Our spectral analyses suggest that during the stages with relatively high source luminosity, the accretion disk is present and the disk resides between the neutron star (NS) and the co-rotation radius, while the disk emission disappears during the low luminosity stages. It is likely that the “propeller”effect takes place in the rapid drop stage, based on which the estimated NS surface magnetic field strength is about 108 G. During the disk accretion episodes the NS is heated and, however, it is cooling when the disk accretion stops. Comparing the spectral fitting parameter and luminosity of this AMXP with those of Z and Atoll sources, we argue that the comptonization region should be transparent to the NS emission for producing the X-ray pulsations in NS low mass X-ray binaries, and the intermediate mass accretion rate might be another requirement for generating X-ray pulsations. Type I X-ray bursts are detected during the outburst, which comforms that the compact object in this system is a NS.
Herschel observations of the HH211 protostellar system
Dionatos, Odysseas
The birth of Sun-like stars is a complex process where several physical processes are involved but whose respective roles are not yet clear. On the one hand, the young stellar object accretes matter from a collapsing envelope. The gravitational energy released in the process heats up the material surrounding the protostar, creating warm regions enriched in complex organic molecules. On the other hand, the presence of angular momentum and magnetic fields leads to the formation of circumstellar disks and the ejection of matter, in the form of collimated jets and wide-angle outflows. In the time-domain, accretion is most likely episodic causing sudden increases in the luminosity of the system and providing, along with the ejecta, energetic feedback to the system.Mid- and far-infrared observations of the environment around embedded protostars reveal a plethora of high excitation molecular and atomic emission lines. A number of different mechanisms for the origin of these lines have been proposed, including shocks induced by protostellar jets and radiation by the embedded protostar interacting with its immediate surroundings. We will report on one of the most dramatic cases, the HH211 protostellar system, where all processes can be seen in action. Due to its pristine appearance, HH 211 stands out amongst the youngest, best-studied outflows which has made it become a text-book example. Being very young and relatively compact (estimated dynamical timescales are less than 500 yr), it has a rather simple and well-defined geometry consisting of a central young stellar object, nearly symmetric outflows and two bright terminal shocks at the opposite outflow ends. Despite the apparent symmetry, analysis of Herschel spectral-line mapping observations demonstrates that the emission around the source and the two terminal bowshocks is dominated by diverse processes that will be detailed in our presentation.
Observations of the Ultraviolet-Bright Star Barnard 29 in the Globular Cluster M13 (NGC 6205)
Dixon, William
We have analyzed FUSE, COS, GHRS, and Keck/HIRES spectra of the UV-bright star Barnard 29 in M13. Fits to the star's optical spectrum yield Teff = 20,000 ± 100 K and log g = 3.00 ± 0.01. Using modern stellar-atmosphere models, we are able to reproduce the complex shape of the Balmer Ha feature. We derive photospheric abundances of He, C, N, O, Mg, Al, Si, P, S, Cl, Ar, Ti, Cr, Fe, Ni, and Ge. Barnard 29 exhibits an abundance pattern typical of the first-generation stars in M13. We see no evidence of significant chemical evolution since the star left the RGB; in particular, it did not undergo third dredge-up. Previous workers found that the star's FUV spectra yield an iron abundance about 0.5 dex lower than its optical spectrum, but the iron abundances derived from all of our spectra are generally consistent with one another and with the cluster value. We attribute this discrepancy to their use of model atmospheres with a finite microturbulent velocity and fitting routines that allow the stellar continuum level to be a free parameter in the fit. By comparing our best-fit model with the star's optical magnitudes, we derive a mass M*/Msun = 0.41 – 0.50 and luminosity log L*/Lsun = 3.25 – 3.34, depending on the cluster distance. Comparison with stellar-evolution models suggests that Barnard 29 evolved from a ZAHB star of mass M*/Msun ~ 0.50, a value close to the boundary between the extreme and blue horizontal branches.
Revealing the line-of-sight structures of Taurus Molecular Cloud 1
DOBASHI, Kazuhito
In this presentation, we introduce a new method to probe into the line-of-sight structures of dense molecular clouds using the HC3N (J=5–4) and CCS(JN=43–32) lines at 45 GHz, and demonstrate results of an application to Taurus Molecular Cloud 1 (TMC-1). In TMC-1, the CCS line is moderately optically thick, and the HC3N line consists of two optically thin hyperfine lines (F=4–4 and 5–5) and three optically thick hyperfine lines (F=6–5, 5–4, and 4–3). The point of the method is to utilize the optically thin lines to identify distinct velocity components, and to utilize the optically thicker lines to infer their relative locations along the line-of-sight by solving the radiative transfer. Using the Z45 receiver and the PolariS spectrometer installed in the NRO 45m telescope (HPBW~40”), we obtained spectral data of these emission lines toward the cyanopolyyne peak in TMC-1. About 30 hours integration with these instruments brought us wonderful spectral data with a very high velocity resolution and sensitivity of 0.0004 km s-1 and 40 mK, respectively. Analyses of the optically thin hyperfine lines of HC3N indicate that there are four distinct velocity components with a narrow line width (≤0.1 km s-1) at VLSR=5.727, 5.901, 6.064, and 6.160 km s-1, which we call A, B, C, and D in the order of increasing radial velocity, respectively. Further radiative transfer analyses of the optically thicker CCS line as well as of the other hyperfine lines of HC3N show that the four velocity components are lying along the line-of-sight in the order of A, B, C, and D from far side to near side to the observer, for which we conclude that TMC-1 is shrinking, moving inward as a whole. Additional analyses based on the 13CO(J=1–0) and C18O(J=1–0) data, which are available in the data archive of the Nobeyama Radio Observatory, also support this conclusion.
SkyQuery: web service for fast cross-matching of the largest astronomical catalogs
Dobos, Laszlo
Fast and accurate cross-identification of astronomical survey catalogs is fundamental for multi-wavelength astronomy. While pre-computed pairwise cross-match catalogs exist for the largest surveys, it is often necessary to match one’s own observations with multiple large catalogs or re-run the cross-identifications with different parameters, hence cross-matching is never a one time operation. Here we present the latest version of SkyQuery, a publicly available web service which provides remote access to a large selection of survey catalogs and a scalable implementation of a Bayesian algorithm capable of full-catalog matching.SkyQuery is a scalable system implemented on the top of a cluster of database servers. It allows form-based and SQL-query-based formulation of cross-match jobs including fast spatial filtering based on the analytical description of spherical regions. SkyQuery is accessible via a web interface and a restful web service for which a Python wrapper library is provided.SkyQuery is fully integrated with the SDSS SkyServer and the new SciServer developed at the Johns Hopkins University. SciServer provides, among others, single sign-on, MyDB (permanent database space for user data), MyScratch (terabytes of database and file space for data staging) and most importantly, SciServerCompute, a remote access Jupyter facility that enables data processing without the requirement of downloading the large data sets.SkyQuery is accessible at voservices.net with an existing SDSS SkyServer account or after free registration.
Characterizing the effect of emission lines on photometric redshift estimation
Dobos, Laszlo
We present the results of our study on the performance and capabilities of empirical and template-based photometric redshift estimation techniques for samples containing strong emission line galaxies. In order to artificially control the photometric error and emission line contribution of our test data set, we developed a stochastic mock catalog generation algorithm. The algorithm can provide a large number of synthetic spectra and magnitudes with high signal-to-noise ratio, as well as match the physical and observational parameter distribution of any input spectroscopic galaxy sample. Instead of running the computationally expensive stellar population synthesis and nebular emission codes, our algorithm generates realistic spectra with a statistical approach, and as an alternative to attempting to constrain the priors on input model parameters, works by matching output observational parameters. Our technique can successfully reproduce the observed color indices and the BPT diagram. By using such a mock catalog, we investigated the behavior of empirical photometric redshift estimation methods in the four dimensional color index space of the SDSS u, g, r, i, z filter set. While photo-z is clearly limited by the photometric error and not the color index degeneracies, one interesting finding is that at low redshift, the presence of emission lines is responsible for resolving the degeneracies and this is one important reason why empirical methods outperform template fitting significantly. Template fitting photo-z methods should use a wide range of templates to fit the colors of low redshift emission line galaxies, or even better, use a two step photo-z estimation technique to first estimate the redshift empirically and fit the colors with templates of a constant redshift to calculate the K-correction and other parameters.
Viscous-warp instability in accretion discs
Dogan, Suzan
Accretion discs are the essential ingredient for a wide range of astrophysical phenomena, including star and planet formation, X-ray binaries and active galactic nuclei. Through several different effects, discs can warp. If a warp in a disc is too large, the disc can break apart into two or more distinct planes. Further if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. Disc tearing has been shown to occur in discs inclined to the spin of a central black hole, in circumbinary discs around misaligned central binary and in circumprimary discs misaligned with respect to the binary orbital plane. As disc tearing promotes markedly enhanced and variable accretion, it has significant implications for a variety of astrophysical systems: e.g. outbursts in X-ray binaries and fuelling SMBH binaries. The criterion for disc tearing has previously been derived simplistically by comparing the viscous torque with the precession torque. In this work, focusing on the diffusive regime, we investigate the stability of warped discs to determine the precise criterion for an isolated disc to break. The instability appears in the form of viscous anti-diffusion of the warp amplitude which leads to a discontinuity in the disc angular momentum. The physics of ‘the viscous-warp instability’ can be understood as a combination of two terms: 1) a term which would generally encapsulate the classical Lightman-Eardley instability in planar discs but is here modified by the warp to include and 2) a similar condition acting on the diffusion of the warp amplitude. This instability underlies the process of disc tearing which has capacity to dramatically alter the instantaneous accretion rate and observable properties of the disc on short timescales. I will present a comprehensive analysis of ‘the viscous-warp instability’ and the emergent growth rates and their dependence on disc parameters.
A wide-field CMOS camera "Tomo-e Gozen"
Doi, Mamoru
The Tomo-e Gozen Camera (Tomo-e) is a wide-field imager with 84 CMOSimage sensors, being built for the 1.05-m Kiso Schumidt telescope. Tomo-e covers ~20 square degrees on the sky, and can monitor ~7,000 squaredegrees every 3 hours down to V ~ 19 magnitude. We present the designand expected performance of Tomo-e, as well as evaluated carachteristicsfrom comissioning data of Tomo-e Q1 (21 sensors).
Spectral analysis of the magnetic field evolution in the ICM
Dominguez-Fernandez, Paola
The origin of the observed magnetic fields in the intracluster medium remains to be unclear. Nevertheless, there are two plausible scenarios that can be able to explain the corresponding radio observations: a primordial scenario where magnetic fields were generated in the very early Universe during phase-transitions, or an astrophysical scenario were magnetic fields were generated by starbursts or AGNs and later on spread into the ICM. Supporting the first scenario, we study the evolution of magnetic fields in a major merger scenario coming from a cosmological MHD simulation made with ENZO (The ENZO collaboration et al. 2013) where the initial magnetic field seed gets amplified via a turbulent dynamo during structure formation. Since this is the first cosmological simulation of the ICM that resolves the magnetic dynamo action (Vazza et al. 2018), we are able to make an analysis of the magnetic power spectra following closely the dynamo theory predicted first by Kazantzev's theory (Kanzantzev 1967).
Astronomy Education and Outreach 2030
Doran, Rosa
We all grew up listening to the classical statement: “The world changed so much”. Well, this has never been more true than in recent times. The same cannot be said about the way we educate and build the science literacy and in particular astronomy literacy of inhabitants of this planet. In the digital era information is something that surrounds us and is available at anytime and anywhere. Schools have to become a hub for the future of communities and communities have to be a strong nest for future generations. Astronomy has always been the trigger for changes, the unifying truth below and above all of us. Nonetheless it is not always recognized as a strong aggregator of science literacy opportunities, as source of change and innovation that often dictates innovation paths for the future. In this presentation we would like to share a few innovative ideas that can put astronomy in the centre stage by building from its legacy and moving towards the jobs of the future. We know that 80% of the jobs in 2030 are not invented yet, that 50% of existing jobs will no longer exist by then. Now is the time to plan the role of Astronomy by building on its existing legacy and paving the way for future generations. In this presentation we intend to present the open schooling movement that is emerging in Europe. Schools are becoming beacons for their local communities and by using the Design Thinking strategies their communities are becoming strong partners in the design of future generations.
Making Tycho Brahe's Sky Accessible to Future Astronomers
Dorch, Bertil F.
We have digitized and analyzed three rare books that provides a unique insight into how astronomical observations were recorded at Tycho Brahe's observatory on the island of Hven, as well as information on the scholarly communication among astronomers in Europe at the time of Tycho. The astronomical books are History Coelestis (Albert Curtz, 1672), Epistolarum Astronomicarum (Tycho Brahe, 1596), and a rare copy of De Nova Stella (Tycho Brahe, 1572). Besides creating freely available and searchable digital ePub ebook copies of the three books, enabling in effect easy and open access to the sky as recorded by Tycho, we have performed a non-destructive X-ray fluorescence (XRF) spectrometric analysis of one of the books, Epistolarum Astronomicarum containing a correspondence between Tycho Brahe and Wilhelm of Hessen: the book is a direct illustration of how astronomers perceived the sky in the late 16th century. This copy of Epistolarum Astronomicarum is particularly interesting because it was printed on Tycho's Hven. Furthermore, the book is wrapped in an even older piece of colorful parchment dating from the Middle Ages, a so called fragment. Based on the XRF analysis we are able to draw conclusions on the composition of the fragment, which turns out to contain substantial amounts of e.g. mercury (Hg). Future work includes further chemical analysis of the books and fragments, as well as a systematic extraction and digitization of the astronomical observations recorded in e.g. Historia Coelestis.
Interactions of solid bodies with atmospheres of protoplanets
Dorfi, Ernst
During the formation of earth-like planets within protostellar disks the accretion of solid bodies plays an essential role in shaping the final planet. Usually the deposition of kinetic energy is simplified by the accretion luminosity L = GMplMacc/Rpl when the bodies, in-falling at a rate of Macc release their kinetic energy at the planets radius Rpl. We investigate this process in more detail because the protoplanets embedded in the gaseous disk are characterized by an extended atmospheres up to the Hill radius. We have developed a simple model for tracking the mass loss, the temperature structure and the break-up of an incoming planetesimal. Even solid bodies of sizes up 10km are stopped or melt by the frictional dissipation and explode into smaller fragments during their flight. In such cases the atmospheric gas is directly heated well above the planetary surface located at Rpl. In addition to this thermal input the release of dust particles modifies the opacity and thereby the overall stratification and extension of the planetary envelope. A large number of computations show how a size distribution of planetesimals generate a vertical heat source depending on the total accretion rate, the velocities at the Hill radius as well as the properties of the planetesimals. We further discuss the influence of the accretion history of planetesimals during building up the final core mass.
Planetesimals role in habitability of TRAPPIST-1 planets
Ðošovic, Vladimir
Minor planets (aka asteroids and comets) are widespread in the solar system, and theobservational evidence suggests that similar planetesimal objects exist also in other planetary systems. Existence of minor planets is also predicted by planet formationmodels. These remaining planetesimals may however play a very important role for ahabitability of the planets within a planetary system. In this work we investigated the role of a hypothetical planetesimal belt locatedclose to the snow line in the Trappist-1 system. We performed N-body simulations to estimate theflux of the small objects towards the planets, focusing on two possible consequences ofthis transport.First, we analyzed the amount of water that may by transported by icy planetesimalsto planets.Second, we estimated the impact risk for each planet, and discussed how these mayaffecthabitability of the planets within the Trappist1 system. Our results showed that during the early phases of the system formation, flux of theplanetesimals from the belt to the region of planets may be significant under certain conditions,allowing significant amount of water to be transported to the planets. The transportis mainly caused bymean motion resonances, although in some cases secular resonances may play acritical role. During the later phases, the flux is significantly reduced, making the impact riskfor potentially habitable planets very small. This is primarily because the non-gravitationaleffects are inefficient in the systems around dwarf stars.
Concept study of the LiteBIRD satellite for CMB B-mode polarization
Dotani, Tadayasu
LiteBIRD is a next generation scientific satellite aiming to detect the footprint of the primordial gravitational wave in a form of polarization pattern called B-mode in the Cosmic Microwave Background (CMB). LiteBIRD is a candidate for JAXA's strategic large mission in Japan under the close collaboration with NASA, ESA, and Canada. It is planned to be launched in the latter half of 2020s with an H3 launch vehicle. The goal of LiteBIRD is to measure the tensor-to-scalar ratio (r) with precision of delta r < 0.001, which is enough to test representative inflationary models. It will cover the frequency range of 34-448 GHz with two telescopes and scan the whole sky from the Sun-Earth Lagrangian point L2. A 3-year full sky survey will achieve a sensitivity of 2.5 micro-K-arcmin with an angular resolution of 30 arcmin around 100 GHz. We will describe the current status of the concept design of LiteBIRD with its scientific goal in the poster.
IONIZING CLUSTERS AND OLD CLUSTERS IN THE HEXAGON LIKE BARRED GALAXY NGC7020
Dottori, Horacio
NGC 7020 is one of the few barred galaxies that present hexagonal ring central structure with ansae at two of its extremes, pointing to the existence of well populated hexagon-like regular orbits surprinsingly centered with the nucleus.The hexagon circunscribes a bunch of young clusters that present Ha emission. Outwards, at the border of the disk appears a circular ring that is also populated with HII regions.In order to study the young stellar population traced by its HII regions, we imaged NGC 7020 with narrow band filters centered at Ha and nearby continuum with GEMINI-S+GMOS-S. SEXTRACTOR was used to find more than 200 HII regions. We determined Ha fluxes and line equivalent width, which allows to model the regions and determine their ages with STARBURST 99.We determined that the external ring is populated with HII regions younger than 8 million years, while the regions circusncribed bye the hexagonal ring are sistematically older. The disk at intermediate scale does not presents HII regions and the ansae do not show Ha emission.We discuss a possible mechanism to form both sets of HII regions in a single event, since no satellites are observed in the neighborhood.About 500 older clusters are also detected with u',g',r',i' imagery. This material is being analised.H. Dottori, R. Diaz, G. Gimeno, A. Bianchi & O. Carneiro
Influence of the void environment on chemical abundances in dwarf galaxies and implications for connecting star formation and halo mass
Douglass, Kelly
We study how the void environment affects the chemical evolution of galaxies in the universe by comparing the oxygen and nitrogen abundances of dwarf galaxies in voids with dwarf galaxies in denser regions. Using spectroscopic observations from SDSS DR7, we estimate the oxygen, nitrogen, and neon abundances of 887 void dwarf galaxies and 666 dwarf galaxies in denser regions. We use the Direct Te method for calculating the gas-phase chemical abundances in the dwarf galaxies because it is best suited for low metallicity, low mass (dwarf) galaxies. A substitute for the [O II] λ3727 doublet is developed, permitting oxygen abundance estimates of SDSS dwarf galaxies at all redshifts with the Direct Te method. We find that void dwarf galaxies have slightly higher oxygen and neon abundances than dwarf galaxies in denser environments. The opposite trend is seen in both the nitrogen abundance and N/O ratio: void dwarf galaxies have slightly lower nitrogen abundances and lower N/O ratios than dwarf galaxies in denser regions. Our mass-N/O relationship shows that the secondary production of nitrogen commences at a lower stellar mass in void dwarf star-forming galaxies than in dwarf star-forming galaxies in denser environments. We also find that star-forming void dwarf galaxies have higher HI masses than the star-forming dwarf galaxies in denser regions. The lower N/O ratios and smaller stellar mass for secondary nitrogen production seen in void dwarf galaxies may indicate both delayed star formation as predicted by ΛCDM cosmology and a dependence of cosmic downsizing on the large-scale environment. The shift toward higher oxygen abundances and higher HI masses in void dwarf galaxies might be evidence of larger ratios of dark matter halo mass to stellar mass in voids than in denser regions.
The Secular Evolution of the Sun's Rotation and the Solar Energetic Photon and Particle Radiation Environment
Drake, Jeremy
Recent years have witnessed a growing realisation that energetic photon and particle radiation plays a crucial role in the formation and evolution of planets, and possibly in the origin of life itself. The Sun's energetic radiation output has decreased by several orders of magnitude since its beginning as a T Tauri star. The radiation environment through time is determined by the Sun's magnetic activity, which in turn both depends on and controls its rotation rate. Here, we show how new insights into stellar magnetic field morphology lead to a new predictive model of stellar winds and rotation evolution that matches observed rotation rates of Sun-like stars of all ages and allows us to determine the energetic photon and particle radiation of the Sun and stars through history.
First Constraints on Empirical Mass-Loss Rates from Magnetic O-stars using Ha Emission
Driessen, Florian
Over the past decade, large survey programs have revealed that roughly 10 % of all massive main-sequence stars harbor large-scale, strong, and organized surface magnetic fields. However, such massive stars also experience powerful starlight-driven wind outflows. Due to the presence of magnetic fields these stellar outflows are consequently magnetically confined. In the case of slowly rotating O-stars being studied in this work, stellar wind material along closed field loops falls back onto the stellar surface due to a cooled downflow. Yet, the transient suspension of material within the loops leads to statistically overdense regions centered at the magnetic equator. The emerging structure, known as a Dynamical Magnetosphere (DM), results in rotational phase modulations of key diagnostic wind lines such as Ha.Using full 3D radiative transfer together with an analytic description of DMs, this poster will present the first results regarding the derivation of empirical mass-loss rates from magnetic O-stars. We infer the mass loss rate by fitting the synthetic Ha emission to observations, a procedure quite analogous to what is being done when deriving mass-loss rates for non-magnetic O-stars, except for the rotational modulation. Obtaining such empirical constraints are of critical importance since the mass-loss “quenching” of the magnetic field is also predicted to have significant effects on the further evolution of the star, e.g., magnetic braking. Moreover, recent results have even suggested Galactic magnetic massive stars to be possible progenitors of “heavy” stellar-mass black holes such as those that led to the ground-braking detection of gravitational waves by the LIGO-Virgo consortium.
First Constraints on Empirical Mass-Loss Rates from Magnetic O-stars using Ha Emission
Driessen, Florian
Over the past decade, large survey programs have revealed that roughly 10 % of all massive main-sequence stars harbor large-scale, strong, and organized surface magnetic fields. However, such massive stars also experience powerful starlight-driven wind outflows. Due to the presence of magnetic fields these stellar outflows are consequently magnetically confined. In the case of slowly rotating O-stars being studied in this work, stellar wind material along closed field loops falls back onto the stellar surface due to a cooled downflow. Yet, the transient suspension of material within the loops leads to statistically overdense regions centered at the magnetic equator. The emerging structure, known as a Dynamical Magnetosphere (DM), results in rotational phase modulations of key diagnostic wind lines such as Ha.Using full 3D radiative transfer together with an analytic description of DMs, this poster will present the first results regarding the derivation of empirical mass-loss rates from magnetic O-stars. We infer the mass loss rate by fitting the synthetic Ha emission to observations, a procedure quite analogous to what is being done when deriving mass-loss rates for non-magnetic O-stars, except for the rotational modulation. Obtaining such empirical constraints are of critical importance since the mass-loss “quenching” of the magnetic field is also predicted to have significant effects on the further evolution of the star, e.g., magnetic braking. Moreover, recent results have even suggested Galactic magnetic massive stars to be possible progenitors of “heavy” stellar-mass black holes such as those that led to the ground-braking detection of gravitational waves by the LIGO-Virgo consortium.
Volatile Links between IRAS16293-2422B and 67P/C-G
Drozdovskaya, Maria
Comet 67P/Churyumov-Gerasimenko has been studied with in situ measurements by various instruments (ROSINA, COSAC, VIRTIS, MIRO) aboard the Rosetta spacecraft, which show that the comet has a rich molecular inventory and that there are complex relationships between various species. These data are one of the best probes of the innate protosolar disk that evolved into our modern day Solar System. Similar chemical richness, including large complex organic species, extends beyond the Earth and our Solar System as attested by countless observations towards high- and some low-mass protostars. One of the best-studied low-mass systems is IRAS16293-2422, which is thought to be analogous to the earlier phases of our Solar System. The region has been surveyed with the large unbiased ALMA Protostellar Interferometric Line Survey (PILS), which allowed its study with an unprecedentedly wide spectral range at high spectral and spatial resolutions. Thereby, its full chemical inventory and the spatial distribution of the detected species could be uncovered. This ALMA data on IRAS16293-2422 can be used to probe the extrasolar chemical content and the Rosetta measurements of 67P/C-G as a Solar System diagnostic. By deriving relative ratios for simple and complex organic molecules, direct comparisons can be drawn between the two to go after the origins of the chemical content of our Solar System. In this talk, results of such a comparative study will be presented, based on relative ratios of major and minor volatile species to access the degree of relative complexity stemming from common parent species. These results give clues to the different radicals available in the ices for subsequent synthesis of larger molecules, shedding light on the dominant pathways to chemical complexity and the physical conditions that optimize such enrichment. The carried out comparative work between protostars and 67P/C-G gives hints on the uniqueness of the ingredients to life.
A systematic survey of grain growth in discs around post-AGB binaries with PACS and SPIRE photometry
Dsilva, Karan
It is now well established that post-AGB binary systems are often surrounded by long-lived, stable circumbinary discs. The spectral energy distributions (SEDs) of these systems show a near-IR excess, making it a powerful tool to shortlist potential evolved binary systems. Interferometric studies have confirmed the very compact nature of the circumstellar material and infrared spectroscopy shows the dust grains in the disc are highly processed. Interaction between the circumbinary disc and the central system might impact the evolution of the system, and hence it is important to understand the evolution of the disc._x005F _x005F Previous studies of individual post-AGB binaries have shown that large grains are required to model the observed sub-millimetre flux. Here we present a systematic survey of 50 galactic post-AGB binary systems. Using data from Herschel (PACS/SPIRE), we extend the SEDs to sub-millimetre wavelengths and use the slope of the SED (called the spectral index) as a diagnostic tool to probe the presence of large grains. We observe a large diversity in spectral indices which means that we observe discs with varying degrees of dust processing. Using a Monte Carlo radiative transfer code (MCMax), we create a large grid of models to quantify the observed spectral indices. Our models include a self-consistent treatment of scattering as well as dust-settling._x005F _x005F The present study presents a uniform analysis of the diverse circumbinary discs around post-AGB binary systems and uses the presence of large grains in the disc as a proxy for evolution._x005F _x005F Keywords: stars: AGB and post-AGB – circumstellar matter – binaries: general – techniques: photometric – infrared: stars
Unravelling M31's accretion history
DSouza, Richard
M31, our nearest large galactic neighbour, offers a unique opportunity to test how mergers of dwarf galaxies affect galaxy properties. M31's stellar halo caused by the tidal disruption of dwarf satellite galaxies is the best tracer of the galaxy's accretion history. Here we use cosmological models of galaxy formation to show that M31’s massive and metal-rich stellar halo containing intermediate age stars implies that it merged with a large (M* ~ 2.5 x 10^10 M_sun) galaxy ~2 Gyr ago. The simulated properties of the merger debris help to interpret a broader set of observations of M31’s stellar halo and satellites than previously considered: its compact and metal-rich satellite M32 is the tidally-stripped core of the disrupted galaxy, M31’s rotating and flattened inner stellar halo contains most of the merger debris, and the giant stellar stream is likely to have been thrown out during the merger. This merger may explain the global burst of star formation ~2 Gyr ago in the disk of M31 in which ~1/5 of its stars were formed. Moreover, M31’s disk and bulge were already in place before its most important merger, suggesting that mergers of this magnitude do not dramatically affect galaxy structure. This merger may also hypothetically explain the corotating plane of satellites of M31.
The radial metallicity gradients in the Galaxy thick disk from LAMOST data
Du, Cuihua
Based on the G/K-type giant stars from LAMOST data release 4, we study the radial and vertical metallicity gradients of the Galactic thick disk. The thick disk stars are identified kinematically and chemically. Our study shows positive radial metallicity gradients d[Fe/H]/dR~0.014 in the inner disk (R<8 kpc ) and negative d[Fe/H]/dR~ -0.005 in the outer disk (R>8 kpc) in 1<|z|<3 kpc. But both gradients get smaller in the range of |z|>3 kpc. In addition, we also derive the vertical metallicty gradients of d[Fe/H]/dz ~-0.08, -0.07, -0.04 with 4 kpc<r<8 kpc,="" 8="" kpc<r<12="" kpc="" and="" 12="" <r<16="" respectively.="" we="" think="" that="" the="" chemical="" radial="" gradient="" might="" be="" a="" signature="" remaining="" from="" primordial="" population="" of="" disk="" stars.="" possibly="" this="" different="" gradients="" between="" inner="" outer="" conform="" to="" inside-out="" formation="" scenarios="" galactic="" disk.<="" p="">
</r<8></p>
Uncovering the unknown population of disk galaxies hosting large-scale radio emission
Duchesne, Stefan
It is uncommon to find dusty disk galaxies hosting powerful AGN, and so large-scale radio emission (> 100 kpc) is not typically seen from such galaxies. However, in rare circumstances this is observed and the alignment is not likely by chance. The number of disk galaxies hosting large-scale radio emission is steadily growing, with new detections resulting from dedicated searches or found serendipitously. Here we present the serendipitous detection of two such sources, and discuss their properties within the context of other disk galaxies hosting large-scale radio emission. We also present new Australia Telescope Compact Array and Murchison Widefield Array data of the emission surrounding NGC 1534. The number of sources currently detected is now sufficient to suggest the presence of an as yet unstudied population of radio galaxies. This suggests that further dedicated searches utilising various current and upcoming radio surveys in combination with optical surveys will shed light on the statistics and optical and radio properties of this largely unstudied class of objects.
Large-scale magnetic field of the accretion disks of T Tauri stars
Dudorov, Alexander
We investigate the large-scale magnetic field in the accretion disks of young stars [1]. Our MHD model of the accretion disks include equations of Shakura and Sunyaev, induction equation with Ohmic diffusion, magnetic ambipolar diffusion, buoyancy and the Hall effect, equations of thermal and shock ionization.Our calculations show that the magnetic field in the accretion disks of young stars has complex geometry. The magnetic field has quasi-azimuthal geometry in the inner regions, where thermal ionization operates. Magnetic buoyancy hinders amplification of the magnetic field in this region. Inside the ``dead’’ zones, the magnetic field geometry is quasi-poloidal due to efficient Ohmic diffusion. Depending on the ionization intensity and dust grains parameters, magnetic field can have quasi-radial or quasi-azimuthal geometry in the outer disk regions, where magnetic ambipolar diffusion hinders amplification of the radial component of the magnetic field. The Hall effect leads to transformation of the toroidal magnetic field into the poloidal one near the borders of the ``dead’’ zones.Our model predicts that magnetic field strength near the inner boundary of the disks of T Tauri stars is 10-100 G, which is comparable with the stellar magnetic field. Typical magnetic field strength at 3 au is 0.1-1 G, in agreement with measurements of meteorites remnant magnetism. Plasma beta is not constant throughout the disk, according to our model.We made synthetic maps of dust emission polarized due to the dust grain alignment by the magnetic field. We show that the ‘dead’ zones can appear in the polarization maps as the regions with the reduced values of polarization degree.References1. Khaibrakhmanov S., Dudorov A., Parfenov S., Sobolev A. MNRAS. 2017. V.464. P.586.
Exploring Dwarf Galaxy Evolution
Dunn, Jacqueline
Dwarf galaxies are the most numerous galaxies in the universe, yet little is definitively understood about their formation and evolution. Different studies have used varying definitions for the dwarf galaxy types, and these varying criteria are partially responsible for the conflicting conclusions reached in previous studies. Some studies have found evidence for environmental effects on the evolution of dwarf galaxies, while others have not. Additionally, previous studies have proposed an evolutionary link between dwarf irregular and dwarf elliptical galaxies, while others found no evidence of such. The nature and existence of the so-called dwarf spiral galaxies are still heavily debated. This project seeks to explore the properties of dwarf galaxies spanning a range of morphological type, luminosity, physical size, and surrounding environment (i.e. group / field galaxies). The goal of this project is to determine the range of exhibited properties for each type of dwarf galaxy using available ultraviolet, visible, and near-infrared imaging and spectroscopy. Similarities in visible, broadband colors support the proposed evolutionary link dwarf irregular and dwarf elliptical galaxies when the range of brightness of the samples is constrained to the fainter galaxies. Here, comparisons amongst a sub-sample of dwarf irregulars, dwarf ellipticals, and dwarf spirals will be presented using archival ultraviolet, visible, and near-infrared imaging and spectroscopy. The effect of limiting the comparisons to the fainter sample members will be explored, as well as the effect of limiting the comparisons to the brighter sample members, with the goal of better constraining the definitions of the various dwarf sub-types for current and future comparisons.
Astronomy from the Moon: Galaxy First Light Imaging and Global Astronomy Outreach
Durst, Steve
Astronomy from the Moon as a new frontier for astrophysics has attracted explorers, scientists, and educators throughout the Space Age, and its realization offers new opportunities for 21st century global / interglobal learning and knowledge, consistent with International Astronomical Union astronomy education development._x005F _x005F The International Lunar Observatory Association (ILOA) series of missions to the Moon aims for Galaxy First Light Imaging._x005F _x005F As did Apollo's first image of Earth from the Moon, acquiring and transmitting the first image of the Milky Way / Galaxy Center taken from the Moon could provide inspiration for people worldwide, expand human understanding of the Cosmos, and advance 21st century science education in every class._x005F _x005F The ILO-1 mission to the Moon South Pole / Malapert Mt., as well as a possible ILO-X precursor aboard a Moon Express lander, will prioritize Galaxy imaging, along with a full range of astronomy observations, for the use and benefit of the worldwide Galaxy Forum network._x005F _x005F The ILOA Galaxy Forum program, to expand galaxy awareness and the understanding of humanity's place in the universe, has hosted thousands of science teachers, students, astronomers and interested citizens in 80+ Galaxy Forums at 25+ locations in Hawai`i, USA, Canada, China, India, Southeast Asia, Japan, Europe, South Africa, Chile and Brazil since the first Galaxy Forum in July 2008._x005F _x005F The ILOA Galaxy Map © designed to inspire and educate, is usually given free to Galaxy Forum participants and demonstrates that Moon-based galaxy / astronomy observation and research is consistent with IAU programs bringing many scientific communities together.
Strongly variable water maser associated with a Sun-like protostar
Dutkowska, Katarzyna
Water plays an important role in the cooling process of the gas in low-mass, solar-type protostars (Karska et al. 2013). Far-infrared emission of water is associated with jets / outflows and can be used to determine the shock type, its velocity, and the pre-shock density of the medium. Water maser emission at 22 GHz is also linked to regions with active jets and abundant high-density gas (e.g. Furuya et al. 2001). Here, we report a strongly variable water maser at 22 GHz towards L1448 IRS 2 detected with Torun 32 m radiotelescope. The source shows a strong variability both in the line strength and the profile features. This is uncommon in masers from low-mass protostars. Comparison of the radio and infrared observations can provide useful tools in understanding of the processes linked to this kind of sources.ReferencesKarska, A., Herczeg, G. J., van Dishoeck, E. F., et al. A&A, 552, A141 (2013)Furuya T et al., ApJ, 559, pp. L143-L147 (2001)Tobin et al., ApJ, 818, pp. 36 (2016)
Can the planetary system HD 141399 harbor habitable planets?
Dvorak, Rudolf
Our aim was to find whether terrestrial planets could have been formed in the habitable zone of the 4 planet system of HD 141399 (found by Vogt et al (2014)). The system consists of 4 gas giants with approximately 0.5 to 1.4 Jupiter-masses orbiting between 0.4 and 5 AU. In our investigations we concentrated on the habitable zone around the late K-type star.In numerical n-body simulations with initially 500 bodies with masses between 0.5 to 2 Moon-masses we let the bodies interact with the gas giants and each other and monitored the growth by collisions and merging. In our initial conditions we also took care of the possible water content of the protoplanets with respect to theirlocation in the 'habitable ring' between the gas giants HD 141399 c and HD 141399 d.It turned out that after millions of years terrestrial planets on stable low eccentric orbits can be formed in the habitable zone of HD 141399 containing a high enough amount of water to make these planets capable of supporting life.
Women in Astronomy Nepal: Its Initiatives and Challenges
Dwa, Manisha
Women in Astronomy Nepal-WIAN is a special initiative at Nepal Astronomical Society (NASO) started in 2015. It aims to act as a forum where women who are doing science or has interest in science can come and explore the possibilities of knowing the universe. The initiative has mainly three programs: Women in Outreach, Women in Science Award and Publication. Women in Outreach proposed to allow women/girls more access to our outreach activities in Nepal. Similarly, Women in Science Award aims to provide better exposure to the Nepali women student and young professionals working in the field of STEM (Science, Technology, Engineering and Mathematics). The initiative proposed to work on the publications of poster/flyer/Book highlighting the contribution of women in Nepal and abroad to STEM to their respective society leading their contribution to global community.This paper will present the status of female participations in our four major projects: Universe Awareness (for primary level or basic level students), All-Nepal Asteroid Search Campaign (for all level of students), National Astronomy Olympiad (for high school students-school level) and Developing Astronomical Skills in Nepal (for undergraduate level students-university level). Also, the challenges while working for women in a country like Nepal will be highlighted. It will also share the impacts of its program to national and international community in brief.
Massive Star Mass-Loss Revealed by X-ray Observations of Young Supernovae
DWARKADAS, VIKRAM
Massive stars lose a considerable amount of mass as they evolve through various phases during their lifetime. Despite years of observations and modelling, the amount of mass lost is still debated. When the star explodes as a supernova, the resulting supernova shock wave expands in the medium created by the stellar mass-loss. The resulting X-ray emission from the star, if it is thermal in origin (as it is about half the time), depends on the square of the density of the ambient medium. The density can be related to the mass-loss rate of the progenitor star. Thus, the X-ray emission can be used to probe the magnitude of the stellar mass-loss in the decades or centuries before the star's death. If the emission is non-thermal it can still set limits on the mass-loss rate. The X-ray lightcurve of the supernova can provide information regarding both the magnitude of the mass-loss as well as its evolution in time before core-collapse. In a few cases, detailed modelling can provide highly accurate results.We have aggregated together data available in the literature, or analysed by us, to compute the X-ray lightcurves of almost all young supernovae (SNe) that have been detected in X-rays. Currently we have about 60 SNe spanning all the various types, but the database is expanding rapidly. The lightcurves span 12 orders of magnitude in luminosity. We use this library of lightcurves and spectra to explore the mass-loss rates of massive stars that collapse to form supernovae, including red supergiants, Wolf-Rayet stars, binary, and unidentified progenitors. The mass-loss rates are lowest for the common Type IIP supernovae, but increase by several orders of magnitude for the highest luminosity X-ray supernovae. The highest mass-loss rates, and the mass-loss evolution, differ considerably from that predicted by stellar evolution models. The range of mass-loss rates, and implications for the mass-loss from massive stars, will be discussed.
A Hydrodynamic Modeling of Atmospheric Escape and Absorption Line of WASP-12b
Dwivedi, Navin Kumar
A systematic and self-consistent modeling of stellar wind (SW) interaction with upper atmosphere of WASP-12b exoplanet has been performed. We assume that the planet is weakly magnetized and therefore the intrinsic planetary magnetic field is not considered in the model. The model includes the basic hydrogen chemistry and describes the expansion of the planetary upper atmosphere and mass loss due to stellar XUV radiative heating. The interaction of the escaping planetary wind with the background plasmas is also included. The two case-scenarios of the planetary material escape and interaction with the SW have been modeled for different XUV radiations and SW parameters, namely the case with formation of a shock (without the inclusion of tidal force) and the stream formation case (with the account of tidal force). The obtained results show that in case of slow SW and without an account of the tidal force, a shock is formed around the planet because of its high orbital velocity, which dominates in the background plasma speed. In this case, the planetary mass loss is controlled completely by the stellar radiation flux. In the second case, the mass loss is mainly due to the gravitational interaction effects. The dynamics of MgII ions was modeled with three different sets of SW parameters and XUV flux values under a realistic Sun-like star condition. The results appear in good agreement with the observations, but do not reveal any signature of early ingress.
Tracing the early planet formation with molecular lines: chemo-dynamical simulations of vortex structures in protoplanetary disks.
Dzyurkevich, Natalia
The infraread observations of dust in protoplanetary disks show us spectacular structures like numerous gaps, vortices and spirals. In order to explain those, both the planet formation and the planet presence are considered. Molecular lines provide information about disks that is complementary to dust continuum observations.We use a reduced chemical network containing main carbon- and sulfur-bearing species to find the molecular species which can be sensitive to the presence of vortex in the protoplanetary disk. We merge the reduced chemical network and state-of-the-art radiative hydrodinamical code to perform the chemo-dynamical simulations of planet-bearing and planet-forming sites.
The Emerging Paradigm for Galaxy Evolution - the Role of the ELTs
Eales, Stephen
The current paradigm for galaxy evolution is based largely on the result of optical surveys, which imply there are two distinct classes of galaxy: star-forming galaxies on a galaxy 'main sequence' and 'passive' or 'red-and-dead' galaxies. The existence of these two classes has the fundamental implication that there must be some catastrophic quenching process that converts a galaxy from the star-forming class to the passive class. The recent Herschel surveys, however, revealed a very different picture. The Herschel results show there is a single, continuous, curved Galaxy Sequence, with galaxy morphology and star-formation efficiency gradually changing along it. This discovery removes the need for a catastrophic quenching process and implies that galaxy evolution is a much gentler business. The Herschel surveys have also revealed rapid galaxy evolution at a very low redshift, which is difficult to explain because dark-matter halos are only growing very slowly at low redshift. The galaxies responsible for this evolution have red optical colours and strong 4000 Angstrom breaks, implying large masses of old stars, but have high star-formation rates, and they are almost certainly the fairly recent ancestors of the red-and-dead early-type galaxies in the Universe today. This important population at redshifts of only ~0.2-0.3 offers a real opportunity to study the process by which the star formation in an early-type galaxy gradually shuts off. Observations of this population with the ELTs will have a resolution of ~15 pc, less than the size of a giant molecular cloud and much better than will obtained for galaxies at 'cosmic noon' (z~1-3). In this talk, I will discuss some of the ways in which it will be possible to use the ELTs to study the kinematics, physics and chemistry of this relatively nearby population, effectively observing galaxy evolution in action.
The major merger origin of the Andromeda II kinematics
Ebrova, Ivana
Prolate rotation (i.e. rotation around the long axis) has been reported for two Local-Group dwarf galaxies: Andromeda II, a dwarf spheroidal satellite of M31, and Phoenix, a transition type dwarf galaxy. The prolate rotation may be an exceptional indicator of a past major merger between dwarf galaxies. We showed that this type of rotation cannot be obtained in the tidal stirring scenario, in which the satellite is transformed from disky to spheroidal by tidal forces of the host galaxy. However, we successfully reproduced the observed Andromeda II in controlled, self-consistent simulations of mergers between equal-mass disky dwarf galaxies on radial or close-to-radial orbit. In simulations including gas dynamics, star formation and ram pressure stripping, we are able to reproduce more of the observed properties of Andromeda II: the unusual rotation, the bimodal star formation history and the spatial distribution of the two stellar populations, as well as the lack of gas. We support this scenario by demonstrating the merger origin of prolate rotation in the cosmological context for sufficiently resolved galaxies in the Illustris large-scale cosmological hydrodynamical simulation.
The spectroscopic evolution of PSR J2032+4127 gamma-ray binary during its periastron passage.
Echevarria, Juan
We present the results of our optical monitoring of PSR J2032+4127 gamma-ray binary around its periastron passage on November 13th, 2017. The compact object in the binary is a highly magnetized neutron star (B~1012 G) that follows an extremely eccentric orbit around the Be star MT91{213} companion. The PSR J2032+4127 is a long orbital-period (49 years) transient lying at a close distance of 1.33 kpc, which makes it an ideal observational target.We observed PSR J2032+4127 with the 2.1m telescope from San Pedro Mártir observatory (México) using the Boller & Chivens spectograph. Our monthly monitoring campaign covered the timeframe from September to December so that we could follow the evolution of the system before, during and after the periastron. In this poster we will present our preliminary results of the observations, focusing on the evolution of the H-alpha profile as well as paying special attention to any characteristic features that may evolve during the passage.The study of this binary close to its periastron passage broadens our knowledge about how interaction works in gamma-ray binaries, and gives us new insights on the accretion physics at play in these kinds of systems.
Features of Long-Term Changes in Areas of Large Sunspots Groups in Solar Activity Cycles 12-24
Efimenko, Volodymyr
We analyze the Greenwich catalog data on areas of sunspots in the thirteen last cycles of solar activity (http://solar.science.msfc.nasa.gov/greenwich/). Namely such parameter was analyzed in papers by Babij et al. [2011], Efimenko and Lozitsky [2016], Nagovitsyn and Pevtsov [2016], and Mandal and Banerjee [2016]. This conclusion follows from consideration of integral distributions for diameters of great sunspots (50-90 Mm) for cycles Nos. 12-24.The main results are following: (a) the average value of the index of the power-law approximation is 5.4 for the last 13 cycles; (b) there is no secular trend of index changes, and (c) there is reliable evidence of Hale's double cycle (about 44 years). Since this indicator reflects the dispersion of the spot diameters, the results obtained show that the convective zone of the sun generates embryos of active regions in different statistical regimes which change with a cycle of about 44 years.ReferensesBabij V.P., Efimenko V.M., Lozitsky V.G. Kinematics and Physics of Celestial Bodies. V. 27, ?4, P.191-196. 2011.Efimenko V., Lozitsky V. Bull. Kyiv. Nation. Univ., Astronomiya. ? 53. ?. 52-55. 2016.Nagovitsyn Yu.A., Pevtsov A.A. Astrophys. J. V. 833, ? 1. id. 94. 6 pp. 2016.Mandal S., Banerjee D. Sunspot sizes and the solar cycle: analysis using Kodaikanal white-light digitized data // The Astrophys. J. Lett. V. 830, ? 2. article id. L33, 6 pp. 2016.
Habitable Zones in Binary Star Systems: New Analytic Estimates
Eggl, Siegfried
A large fraction of stars in our galactic neighborhood have close stellar companions. Whether or not terrestrial planets can retain Earth-like conditions in such systems largely depends on the interplay between stellar radiation, orbital dynamics and a planet’s “climate interia.” The latter is a measure of how quickly a planet’s climate adapts to time dependent radiative orbit forcing. In this contribution I present new analytic estimates that accurately predict the existence and extent of dynamically stable habitable zones in binary star systems by fully accounting for the interaction between the stars and the planet. Analytically derived habitable zone borders are, furthermore, compared to current state-of-the-art climate simulations using 3D General Circulation Models (GCMs).
Superbubbles and triggering of star formation in nearby dwarf irregular galaxies
Egorov, Oleg
Dwarf irregular (dIrr) galaxies provide the best environment for studying the influence of supernovae and stellar winds onto the ISM leading to creation of the superbubbles and large HI supershells. Thanks to thick solid-body rotating discs, such structures grow to a large sizes (up to several kpc) and live longer than in spiral galaxies. The interaction of the HI supershells might trigger a new burst of star formation in a galaxy, while the influence of ongoing star formation in their rims might lead to dissolution of the HI structures. Here we present the results of long-term observations of several nearby dIrr galaxies made with a scanning Fabry-Perot interferometer and narrow-band filters performed at the 6-m telescope of SAO RAS. An analysis of the ionized gas morphology and kinematics in star forming regions of these galaxies allowed us to identify a number of expanding superbubbles, as well as a lot of filament-like ionized structures. We show that star formation in the observed galaxies mainly take place in the unified complexes with sizes of several hundreds pc inside the rims of giant HI supershells. A certain signs of star formation propagation within these complexes, as well as its triggering at the scales of the whole complexes, are detected.
Gas metallicity distribution in polar-ring galaxies
Egorov, Oleg
Polar-ring galaxies are common among the multi-spin composite systems. The different mechanisms of their formation were proposed: a major dissipative merging, a tidal accretion from gas-rich companion, a cold accretion of pristine low-metallicity gas along a filament. We performed a long-slit spectroscopy of the sample of polar-ring galaxies selected from Sloan-based Polar Ring Catalog at the 6-m SAO RAS telescope. We analyzed the mechanisms of gas excitation and gas chemical abundance distribution in the sample galaxies. No any significant metallicity gradient was observed. In most cases our results allowed us to rule out the cold accretion scenario, for which we could expect the gas chemical abundance of the polar disc much lower in comparison with the main disc of the galaxy.
Study of galaxies in the Eridanus void.
Egorova, Evgeniya
We present a sample of 66 galaxies belonging to the equatorial part (Dec.= –7?, +7?) of the large so called Eridanus void. Our main goal was to study systematically the evolutionary parameters of the void sample (metallicity and gas content) and to compare the void galaxy properties with their counterparts residing in denser environments. Besides the general galaxy parameters, compiled mainly from the literature, we present the results of the dedicated observations to measure the oxygen abundance O/H in HII-regions of void galaxies with the 11-m SALT telescope (SAAO) and the 6-m telescope BTA (SAO), as well as the O/H estimates derived from the analysis of the SDSS DR7 spectra. We use this O/H data to build for our sample the relation log(O/H) versus MB, which we compare with that of the ‘reference’ sample of similar type galaxies from the Local Volume. We find a clear evidence for the substantially lower average metallicity of the Eridanus void galaxies. This result well matches the conclusions of our recent similar study for galaxies in the Lynx-Cancer void.
Search for evidence of gas accretion onto late-type disc galaxies in void environment: NG428 case
Egorova, Evgeniya
In our study, we are searching for imprints of gas accretion onto galaxies residing in voids. The void environment is favorable for distinguishing between different sources of accreted gas. Accretion events could result in the decrease of metallicity in certain regions, kinematical perturbations, and star formation on the periphery of galaxies. We compiled a sample of void galaxies with intermediate luminosities that reveals unusual and perturbed appearance; some of them also have relatively low metallicity for their luminosity in comparison with the standard relation. To examine the hypothesis of gas accretion onto these galaxies, we use the Fabry-Perot interferometer data in the Ha-emission line along with the long-slit spectral data obtained with the SAO RAS 6-m telescope (Russia) and deep optical photometry performed with the 2.5m SAI MSU telescope (Russia) along with the data available in open archives (SDSS, WISE, etc.). Radial distributions of the ionized-gas metallicity are constructed. Here we present the results for NGC 428---the central member of a loose group residing in the Eridanus void. Our data prove the existence of an accreted warped gaseous disk in this galaxy.
Accretion and ejection coupling during the giant flares of Cygnus X-3
Egron, Elise
Cygnus X-3 is a high-mass X-ray binary (HMXB) that consists of a compact object wind-fed by a Wolf-Rayet star. The nature of the compact object is still uncertain, but a black hole seems to be favored. Cyg X-3 is the brightest microquasar at radio frequencies, showing giant radio flare episodes with uncommon flux densities up to 20 Jy. These spectacular and rare events give unprecedented opportunities to better understand the relationship between accretion state and jet launching mechanisms, and to compare the effect of accretion geometry (companion star, orbital parameters) to other HMXBs. After more than five years of quiescent state (0.1-0.2 Jy), Cyg X-3 underwent two giant flares in September 2016 and April 2017. These events occurred a few weeks after the source performed a transition to the quenched radio state (< 0.03 Jy). A transition from the ultra-soft X-ray state to a harder X-ray state was clearly visible at the onset of the giant radio flares, together with a gamma-ray emission registered with AGILE and Fermi/LAT. The radio emission of the two last giant flares was monitored with SRT (64-m) and Medicina (32-m) in order to follow the evolution of the flare on a hourly scale. Rapid flux variations were observed at high radio frequencies (18-25 GHz) at the peak of both flares, together with a rapid evolution of the spectral index (from 0.4 to 0.6 with S ? ?^(-a) in less than 5 hours. This is the first time that such fast variations are observed, giving support to the evolution from optically thick to optically thin ejecta in expansion moving outwards from the core.
First X-ray look at Green Peas
Ehle, Matthias
Cosmic reionisation of the Universe played an important role in the galaxy formation and their observability. The source of the ionising radiation is, however, not yet clearly determined: it could be due to strong AGN activity or due to tremendous star formation. Whether ionising radiation from high star-forming galaxies can escape to the intergalactic medium is being discussed.Green Peas represent a class of compact high star-forming galaxies that have recently shown signatures of the escape of the ionising flux. We present first measurements of Green Peas in the X-ray domain to constrain their flux at high energies. We found that the X-ray flux is about an order of magnitude larger than expected from the standard relation between the X-ray flux and the star formation rate. Our results indicate that Green Peas galaxies produce more high-energetic flux than other starforming galaxies, and can therefore be considered as sources with potentially large and significant ionising radiation escape.
RCW98: a dust enshrouded HII region
Ehlerová, Sona
We present observations of the warm ionized gas in the HII region RCW98 and combine them with images of this region at other wavelengths (dust, CO and HI). Using the thin shell approximation we construct the simple model of this warm bubble and compare it with the radiation and mechanical energy released by young stars inside the HII region.
The Next Generation Fornax Survey (NGFS): The Central Dwarf Galaxy Population
Eigenthaler, Paul
We present a photometric study of the rich dwarf galaxy population in the core region (? rvir/4) of the Fornax galaxy cluster based on deep u'g'i' photometry from the Next Generation Fornax Cluster Survey (NGFS). All imaging data were obtained with the Dark Energy Camera mounted on the 4-meter Blanco telescope at the CTIO. We identify 258 dwarf galaxy candidates with luminosities -17 ? Mg' ? -8 mag, corresponding to typical stellar masses of 9.5 ? log M? /M? ? 5.5, reaching ~3 mag deeper in point-source luminosity and ~4 mag deeper in surface-brightness sensitivity compared to the classic Fornax Cluster Catalog. Based on the present NGFS data and the comparison with other stellar systems from the literature, we discuss the implications of our findings for galaxy stellar mass assembly over a stellar mass range of 5?log(M?/M?)?12. We find that over the sampled stellar mass range several distinct mechanisms of galaxy mass assembly can be clearly identified: i) dwarf galaxies assemble mass inside the half-mass radius up to log M? ˜ 8.0, ii) a regime of isometric mass assembly in the range 8.0 ? log M?/M? ? 10.5, and iii) massive galaxies assemble stellar mass predominantly in their halos at log M? ˜ 10.5 and above.
A new Python interface for the spectroscopic data analysis.
El jariri, Youssef
Recently we have carried out a campaign of measurements of spectra of variablestars at the Oukaimeden observatory. To analyse thousands of spectra, we developed agraphical interface under Python. Spectroscopic study of variable stars is based on theacquisition of data in the observatory, and their storage in fit files. We treat thisdata digitally to make them exploitable and graphically representable, for this purposewe use the special software or scripts developed by the astrophysicists. To facilitateanalysis and meet our needs, we developed a graphical interface using Python, we usingthe Tkinter module to represent graphically our spectroscopic data. This interfaceisable toplot figures of our spectra on 1D, and as a superposition on 1D and 2D. Thus, thisinterface can determine the necessary parameters in the spectroscopic study of short-period variable stars; such as the pulsation phase, the Blazhko phase, the correction ofthe heliocentric velocity... Moreover, we can use this interface to convert the pre-treatedfit files into text filesas well as to create Excel tables containing the calculatedparameters. This interface is easy, fast to use, andcan provide high quality figures.
AstroCamping Project In Djerba: First step to develop Astronomy in Tunisia
El Yazidi, Mayssa
Tunisia is a country located in the North of Africa, on the coast of the Mediterranean Sea and also on the edge of the Sahara Desert, It is the seat of several national museums which exhibits archaeological pieces ranging from Roman mosaics to Islamic art and that's give it a very special cultural value.Unfortunately, in Tunisia there are no professional astronomical observatories, or dedicated professional instruments for this field of science. However, there are several telescopes used in the context of cultural and associative activities and for general public events.A project that can link the uncontaminated beauties of our Country with the natural passion for astronomy is the Astro Camping in Djerba . The island of Djerba is a renown touristic attraction, far from noise and light pollution, an ideal place to look for new adventures and new experiences. The Astro Camping in Djerba, is indeed a proposed project based on two different displines: Astronomy and Tourism. This project is structured over four to five days during which several scientific activities are offered together with parties and musical events. During the day tourists can visit the island of Djerba with boats, visit museums, exhibitions, monuments, and health resorts. At night there will be astronomical observations with telescopes placed near the beach, looking at the stars, the MilkyWay and enjoying the very good quality of the sky : an excellent opportunity for Astrophotography. In this way tourists can enjoy the two beauties of Djerba: the charm of the blue sea, the fresh air and also the observation of the universe, galaxies and the deep starry sky...The evenings will be animated by quizzes, games and theater sessions for the children.This Astro camping project has already been tested by a small group of students in August 2018, and it was a very successful experience.
AstroCamping Project In Djerba: First step to develop Astronomy in Tunisia
El Yazidi, Mayssa
Tunisia is a country located in the North of Africa, on the coast of the Mediterranean Sea and also on the edge of the Sahara Desert, It is the seat of several national museums which exhibits archaeological pieces ranging from Roman mosaics to Islamic art and that's give it a very special cultural value.Unfortunately, in Tunisia there are no professional astronomical observatories, or dedicated professional instruments for this field of science. However, there are several telescopes used in the context of cultural and associative activities and for general public events.A project that can link the uncontaminated beauties of our Country with the natural passion for astronomy is the Astro Camping in Djerba . The island of Djerba is a renown touristic attraction, far from noise and light pollution, an ideal place to look for new adventures and new experiences. The Astro Camping in Djerba, is indeed a proposed project based on two different displines: Astronomy and Tourism. This project is structured over four to five days during which several scientific activities are offered together with parties and musical events. During the day tourists can visit the island of Djerba with boats, visit museums, exhibitions, monuments, and health resorts. At night there will be astronomical observations with telescopes placed near the beach, looking at the stars, the MilkyWay and enjoying the very good quality of the sky : an excellent opportunity for Astrophotography. In this way tourists can enjoy the two beauties of Djerba: the charm of the blue sea, the fresh air and also the observation of the universe, galaxies and the deep starry sky.This Astro camping project has already been tested by a small group of students in August 2018, and it was a very successful experience.
Morphology of stellar populations in the Magellanic Clouds from the VMC Survey
El Youssoufi, Dalal
Located at approximately 50 and 60 kpc, the Magellanic Clouds represent the nearest interacting pair of galaxies to the Milky Way. Due to their proximity to our own galaxy, resolved stellar populations and ongoing star formation, the Magellanic Clouds have been targets of intensive research for many years, making them a rather useful laboratory for studying galaxy interactions in a near-field cosmological context. Their morphology, dynamics, and evolution are highly complex and must have been heavily influenced by their interaction with each other as well as with the Milky Way. Tidal forces caused structural changes in the galaxies and so the study of their morphology and structure is important to understand the effect of these interactions. Traced by different stellar populations, the morphologies of the Magellanic Clouds show different properties, different tracers and methods also yield centres that are not mutually consistent.The VISTA near-infrared survey of the Magellanic System (VMC) offers the deepest YJKs band photometry across the Magellanic Clouds up to date, going all the way down to Ks=20.3 (Vega) at S/N=10 with a sensitivity corresponding to the bottom of the red giant branch population. We are using the VMC to investigate the spatial distribution of stellar populations of different ages across the Magellanic Clouds. We also determine the centroids of each stellar population. In this contribution, I will present the result of these studies that allow us to trace substructures possibly related to the interactive history of the Magellanic Clouds.
Gaseous clumps, accretion bursts, and the prospects of giant planet formation in gravitationally unstable protostellar disks
Elbakyan, Vardan
Planets form in gaseous and dusty disks around young stars. A possible scenario for giant planet formation is disk gravitational instability and fragmentation. We use high-resolution grid-based numerical hydrodynamics simulations to compute the formation and long-term evolution of gravitationally unstable protostellar disks around solar-mass stars. We show that gaseous fragments that have formed in the outer regions of a protostellar disk (> 100 AU) through disk fragmentation may later become perturbed by other fragments or disk structures, such as spiral arms, and quickly migrate toward the central star (during ~ few 103-104 years). During inward migration, the fragments first gain mass (up to several tens of Jupiter mass), but then quickly lose most of it through tidal torques when approaching the star. Part of the lost material can be accreted on the central star causing an FU-Ori-type luminosity outburst. This mass loss, or tidal downsizing, helps the fragments to halt their inward migration at a distance of a few tens of AU. The resulting fragments are heavily truncated both in mass and size compared to their wider-orbit counterparts, keeping only a dense and hot nucleus. During the inward migration, the central temperature in these fragments may exceed the molecular hydrogen dissociation limit (~2000 K) and the central region of the fragment can collapse into a gas giant protoplanet. We argue that FU-Orionis-type luminosity outbursts may be the end product of disk fragmentation and inward fragment migration, ushering the formation of giant protoplanets in the inner parts of protostellar disks.
Gaseous clumps, accretion bursts, and the prospects of giant planet formation in gravitationally unstable protostellar disks
Elbakyan, Vardan
Planets form in gaseous and dusty disks around young stars. A possible scenario for giant planet formation is disk gravitational instability and fragmentation. We use high-resolution grid-based numerical hydrodynamics simulations to compute the formation and long-term evolution of gravitationally unstable protostellar disks around solar-mass stars. We show that gaseous fragments that have formed in the outer regions of a protostellar disk (> 100 AU) through disk fragmentation may later become perturbed by other fragments or disk structures, such as spiral arms, and quickly migrate toward the central star (during ~ few 103-104 years). During inward migration, the fragments first gain mass (up to several tens of Jupiter mass), but then quickly lose most of it through tidal torques when approaching the star. Part of the lost material can be accreted on the central star causing an FU-Ori-type luminosity outburst. This mass loss, or tidal downsizing, helps the fragments t o halt their inward migration at a distance of a few tens of AU. The resulting fragments are heavily truncated both in mass and size compared to their wider-orbit counterparts, keeping only a dense and hot nucleus. During the inward migration, the central temperature in these fragments may exceed the molecular hydrogen dissociation limit (~2000 K) and the central region of the fragment can collapse into a gas giant protoplanet. We argue that FU-Orionis-type luminosity outbursts may be the end product of disk fragmentation and inward fragment migration, ushering the formation of giant protoplanets in the inner parts of protostellar disks.
Exploding granules in the atmosphere of the Quiet Sun
Ellwarth, Monika
We studied the temporal evolution of exploding granules and dark dots in the quiet Sun. We characterised the events with simultaneous observations of spectropolarimetric data from the Interferometric Bidimensional Spectrometer, high cadence images from the Rapid Oscillations in the Solar Atmosphere instrument, and slitjaw images as well as slit spectra from the Interface Region Imaging Spectrograph. The data from these various instruments include several photospheric and chromospheric lines allowing us to perform a height-dependent analysis.The intensity and Doppler velocities of the Fe I 6173 Å and Ca II 8542 Å lines in the core and at the edge of the exploding granule and in dark dots were studied. We also used a local correlation tracking method to obtain the horizontal velocities in the photosphere and determined the effective magnetic fields by the centre-of-gravity method. Additionally, MLT_4, a multiple-level pattern recognition code, was used for granulation tracking to determine the size, growth and lifetime of granules.We can confirm earlier reported values of the down flow velocity in the granule centre and the expansion rate of exploding granules. Preliminary analysis of the chromospheric Ca II 8542 Å and Ca II K lines indicate localized heating above the dark centre of the exploding granule seen in photospheric diagnostics, with a time delay of 1-2 minutes.
Understanding historical observations of solar diameter
Emilio, Marcelo
Historically the earliest estimates of the solar radius were obtained by Aristarchus in 270 BC. The historical value of 900° was contrasted long afterwards by measures of Auwers (1891) and by Schur and Ambronn (1896), using a heliometer. The value obtained by Auwers, subtracted from the "irradiation correction", is 959",63 that was the adopted value until the IAU 2015 resolution B3. Different authors analyzed sets of measurements of the solar diameter arrived in opposite conclusions. Among them, Gilliland (1981) studying a data set, distributed over 258 years, such as meridian observations, Mercury transit and solar eclipses, evidenced the existence of an 11-year modulation, in addition to a secular variation of 76 years. Toulmonde (1997), analyzing measurements obtained through eclipses and transit of Mercury, compared to more modern techniques obtained with astrolabes, intends that the variations found are only due to the advance in the precision, and therefore due to optical effects, improved with the advance of observational and instrumental techniques. The Michelson Doppler Imager aboard the Solar and Heliospheric Observatory made the first space-based time series of the variations of the solar size (Kuhn et al. 2004; Bush et al 2010) as well absolute measurements of the solar diameter using Mercury (Emilio et al. 2012) and Venus transit (Emilio et al. 2015). The Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory improved the accuracy to measure the solar limb and made possible to variations caused by p modes oscillations. In this work we show the difficulties to analyze historical observations of solar diameter. An intrinsic problem in this kind of measurements are the systematic errors. The definition of a same point in the limb darkening function, earth atmosphere and changes in the instrumentation are among the factors that need to be consider when comparing solar diameter time-series.
Astrobiology education for teachers in Brazil
Emilio, Marcelo
In Brazil astrobiology education is rarely observed, despite the growing development of astrobiology as a science. In this work we seek to identify the importance of astrobiology for the formation of Science and Biology teachers in Brazil, as well as to recognize the knowledge and attitudes of undergraduate students of biological sciences, who attend astrobiology classes. The information was collected through the application of a questionnaire, consisting of closed (multiple choice) and open (descriptive) questions. With the questionnaire we sought to identify what astrobiology represents for the investigated students (N = 20). The knowledge that students have about astrobiology is divided into five categories: Science that studies / finding life in the Universe; Science that studies the origin of life; Science that studies the evolution of life; Science that seeks to identify biomolecules in space; Science that links Astronomy to Biology. The students associated astrobiology primarily with remote sensing of life and the interaction between life and astrophysical events. The attitudes that academics have regarding astrobiology are satisfactory, 55% of those surveyed believe that this Science is important for the training of science and biology teachers, and 45% believe it to be very important. When asked about the scientific knowledge of astrobiology, 55% of the students believe that they will use this knowledge in their professional life, and 40% said that they will certainly use it. With this work we recognize astrobiology as a structuring part of the formation of science and biology teachers, in addition to its importance for the academic in formation.
Nitrogen-included carbonaceous Compounds (NCC): Laboratory-synthesized organics as the probable candidate for the carrier of the UIR bands observed in dusty classical novae
Endo, Izumi
The unidentified infrared (UIR) bands have been observed ubiquitously in various astrophysical environments. PAHs (polycyclic aromatic hydrocarbons) are often used as a likely candidate of the band carriers to interpret the behavior of the observed UIR bands, however, our knowledge on the true carriers of the UIR bands is still limited. We have experimentally synthesized Nitrogen-included Carbonaceous Compounds (NCC) by exposing Quenched Carbonaceous Composites (QCC; Sakata et al. 1983, Nature, 301, 49) to nitrogen plasma via 2.45 GHz microwave discharge and examined its infrared properties. Infrared absorption spectra of NCC exhibit a broad feature around 7.9µm, which is remarkably similar to the “Class C” UIR bands observed at classical novae (e.g., V2361 Cyg). Our plasma chemical vapor deposition (CVD) method to synthesize NCC well simulates the process of dust formation/evolution in nova outburst ejecta. In the process of dust condensation in stellar ejecta from evolved stars, nitrogen inclusion into carbonaceous dust can naturally occur. Moreover, a high nitrogen content in nova shells is often reported (Dalgarno & Escalante 1989, RMxAA 18, 184). The N/C ratio (atom) of NCC is 4.1-5.3% from the measurement with EA/IRMS (Elemental Analyzer/Isotope Ratio Mass Spectrometer) at JAMSTEC (Japan Agency for Marine-Earth Science and Technology). X-ray Absorption Near Edge Structure (XANES) analysis of NCC indicates that amine and imine structures are included in the NCC. We conclude that the 7.9µm feature of NCC is attributed to aromatic and/or aliphatic amine. The remarkable similarity between the infrared properties of NCC and the UIR bands observed in classical novae suggests that the NCC, which has amine structure and contains N/C=4-5% of N atoms, is a strong candidate of the carrier of the UIR bands formed around some dusty classical novae. We will also discuss a potential link between NCC and Insoluble Organic Matter (IOM) in meteorites.
The loss of large amplitude pulsations at the end of AGB evolution
Engels, Dieter
OH/IR stars are thought to belong to the more massive part of the AGB and early post-AGB population, and are obscured due to optically thick dusty envelopes. The envelopes harbour luminous 1612 MHz OH maser emission, which can be used to monitor the stellar variability. The stars are either large amplitude variables with periods up to 7 years, or show small or even no amplitude variations. This dichotomy in the variability behaviour is assumed to mark the border between the AGB and the post-AGB evolutionary stages. As both groups are apparently disjunct, the cessation of large amplitude pulsation must occur over a very short period (<<1000 years). A current monitor program (https://www.hs.uni-hamburg.de/nrt-monitoring) of a sample of several dozen OH/IR stars made with the Nancay Radio Telescope at 1612 MHz, tries to find objects in transition and to describe their variability properties. We consider the fading out of pulsations with steadily declining amplitudes as a viable process. Promising candidates are presented in this Poster.
Photometric properties for a carbon star DARWIN model grid
Eriksson, Kjell
We have computed a new grid of Radiation HydroDynamic models for carbon-rich AGB-stars with the DARWIN code, this time using size-dependent dust opacities (instead of using the small particle approximation) but otherwise like the grid in Eriksson et al. 2014 (A&A 566, A95). The main results of this modification are that the mass-loss rate vs outflow velocity relation is rather unaffected and that the dust condensation degree is roughly halved.The photometric properties of the grid, as computed by the COMA code, will be presented. Specifically, synthetic magnitudes in the Johnson-Cousins BVRI and the Johnson-Glass JHKLL'M systems were calculated.
Ultra-luminous X-ray sources as neutron stars propelling and accreting at super-critical rates in high-mass X-ray binaries
Erkut, M. Hakan
Ultra-luminous X-ray sources (ULXs) are thought to be a heterogeneous group consisting of either the intermediate mass black holes accreting matter at critical (Eddington) rates or stellar mass black holes or neutron stars accreting matter at super-critical rates. There is growing evidence following the discovery of pulsating ULXs that accreting neutron stars in high-mass X-ray binaries (HMXBs) form a subclass and might even be common within the present population of ULXs. The earliest stage of HMXBs may harbor rapidly rotating neutron stars propelling out the matter transferred by the massive companion. The newly born ULXs may therefore emerge as super-critical propellers manifesting super-Eddington luminosities through the spin-down power transferred by the neutron-star magnetosphere to the accretion disk. In this picture, pulsating ULXs appear as super-critical mass-accreting descendants of non-pulsating young ULXs. We present this evolutionary scenario within a self-consistent model of magnetosphere-disk interaction and discuss the implications of our results on the spin and magnetic field of the neutron star.
Testing one-zone chemical evolution models against hydrodynamics simulations of Local Group dwarf galaxies
Escala, Ivanna
We can potentially distinguish between different star formation and mass growth histories by applying galactic chemical evolution models to detailed observations of chemical abundances in dwarf galaxies. However, typical shortcomings of one-zone chemical evolution models, such spatial chemical homogeneity, may limit the predictive power of such models. We test the ability of one-zone chemical evolution models to match predictions from cosmological, hydrodynamics simulations of dwarf galaxies from the Feedback in Realistic Environments (FIRE) project in the mass range M$_{\star}$($z$ = 0) $\sim$ 7 $\times$ 10$^{5}$ - 2 $\times$ 10$^{8}$ M$_{\odot}$. Building off ofthe Kirby et al. chemical evolution model, which incorporates gas accretion, supernovae-driven mass loss, and tracked abundances from Types Ia and II supernovae, we introduce additional physics (e.g., alterations to the Ia delay time distributions, enriched gas accretion events) to improve agreement with the FIRE simulations. We determine the best-fit model parameters for the simulated dwarf galaxies using Markov chain Monte Carlo methods, and derive their star formation and mass growth histories from their simulated $\alpha$-element abundance patterns. Additionally, we apply the chemical evolution model to observed chemical abundances in Milky Way and M31 satellite galaxies to compare model predictions against observations. By contrasting results from chemical evolution models with the known evolutionary history of the simulated dwarf galaxies, we quantify the degree to which one-zone models can reliably be applied to Local Group dwarf galaxies.
Crossed-nutation effect of a Poincaré non-rigid Earth model
Escapa, Alberto
There is no theory accounting for the crossed-nutation effect for the non-rigid Earth. Crossed-nutation is a second order effect in the sense of perturbation theories arising from the coupling between the lunisolar nutations and the gravitational potential generating them. Although current IAU nutation model IAU 2000 (Mathews et al. 2002) tried to incorporate this effect in its formulation, its treatment presents some deficiencies. First, since the crossed-nutation is constructed from the rigid theory (Souchay et al. 1999), it lacks from the part associated with the Oppolzer terms. This part might play a relevant role at the micro arc second level due to the resonances of the fluid core. Second, the derived Poisson terms in IAU 2000 can be misleading. The reason is that the transfer function approach used to construct IAU 2000 is linear, whereas the crossed-nutation effect is intrinsically non-linear, so its application to derive these terms is more than doubtful. These issues can be solved by extending the Hamiltonian theory of the non-rigid Earth to the second order._x005F We present the first of such extensions (Getino et al. 2018) for a non-rigid Earth model composed of a rigid mantle enclosing a fluid core, the so-called Poincaré model. In particular, to run a parallel way to the rigid Earth, it has been necessary to modify previous results (Getino 1995) in order to find a canonical set of variables suitable for performing the cumbersome second order analytical computations._x005F The formulation of the Hamiltonian of the system in this new canonical set has allowed us to obtain the crossed-nutation effect through the Hori perturbation method. It has been found that there are marked differences, relevant at the micro arc second level, with respect to the rigid model. This fact represents a big difference with respect to the first order results where the nutations of the angular momentum axis are independent of the Earth interior structure.
Slichter modes of celestial bodies through a variational formalism
Escapa, Alberto
Some bodies of the solar system are thought to have a subsurface global fluid layer. Indeed, it is the case for the Earth, but other planets like Mercury or some icy satellites may also share this situation._x005F A particular feature of this kind of bodies is that the barycenters of its solid constituents can perform differential displacements. This internal dynamics has commonly an oscillatory nature. It was considered for the first time in the Earth case by Slichter (1961). Hence, the denomination of Slichter modes for referring to its different normal or oscillation modes. The Slichter modes of other bodies have received less attention in spite of the fact that, if excited, their observation might provide an indirect proof of the existence of an internal fluid layer or constrain its dimensions._x005F We revise the necessary steps to implement the variational formalism (Escapa & Fukushima 2011, 2015) to solve this kind of problems. Its main advantage is that the solids and the fluid are considered as a single dynamical system. Its dynamics is obtained from the Lagrangian, involving the computation of the kinetic and potential energies of the solids and the fluid. The dynamics of the fluid, in these circumstances, is captured by solving a Neumann problem that just depends on the dynamical state of the solids (Lamb 1916). Hence, the fluid-solid interaction is automatically incorporated into the kinetic energy of the system without needing the computation of the pressure field of the fluid._x005F The theory is exemplified by applying it to two different models of three-layer structures: in the first, both solid constituents are undifferentiated whereas in the second one the inner core is assumed to be differentiated. It allows us to discuss the dependence of the Slichter mode on the rheological properties of the model, as well as to compare the Slichter modes of different celestial bodies. Applications to different models of Mercury, Europa, Titania, Oberon, etc. are provided.
Using barium stars to constrain binary interaction in systems containing stars with convective envelopes
Escorza, Ana
It is estimated that about half of the stars in the Galaxy have a companion which, at specific stages, can strongly affect their evolution. A rich zoo of objects can emerge from these interactions, ranging from thermonuclear novae, supernovae type Ia, or gravitational wave sources, to less energetic systems such as sub-dwarf B stars, barium stars or cataclysmic variables. Therefore, binary interaction plays a fundamental role in understanding stellar evolution and the chemical evolution of the Galaxy.During evolution, interactions increase when one of the components evolves to giant dimensions. We focus on chemically peculiar barium (Ba) stars, which are main-sequence or giant stars formed due to binary interaction when a former AGB companion (now a dim white dwarf) polluted them with enriched s-process matter. A long-standing problem, however, is that their observed orbital properties cannot be accounted for by models, so their formation is not well understood. Additionally, a second phase of interaction may occur when the Ba dwarf climbs the red giant branch (RGB), complicating this picture.In this contribution, we present new binary evolution models computed with the state-of-the-art code BINSTAR investigating the change of the orbital elements of Ba stars during their ascent of the RGB. We have accumulated large statistics for these systems: more than 400 Ba stars have recently been placed on the HR diagram, orbital elements for many systems have been accurately determined, and we expect a natural link between Ba dwarfs and Ba giants. Using information from dwarf systems, we have created a grid of models with different initial conditions (eccentricities, periods, masses, wind prescriptions and tidal efficiencies) to explore possible interaction mechanisms that would lead to the formation of the Ba giant orbits that we currently observe. Our ultimate goal is to obtain a better quantified understanding of binary interaction physics with convective primaries.
Modeling instrumental systematics in exoplanets transmission spectras using Gaussian Processes
Estrela, Raissa
Several transiting exoplanets, from Hot Jupiters to Super-Earths, are having their atmospheres investigated using the most powerful technique to date: transmission spectroscopy. This technique measures the wavelength-dependent absorption of starlight by the planet's atmosphere during a transit revealing the atmospheric composition. However, instrumental systematics can significantly affect the transmission spectra leading to some spurious detections. This is an important issue that has been overlooked in the scientific community due to the presence of instrumental systematics produced by many instruments (Hubble/NICMOS, FORS2, etc). The recently introduced technique of using Gaussian Processes (GP), also widely used in machine learning and Bayesian regressions, has been successfully used to model systematic or correlated noise and to infer accurate planet-to-star ratios and realistic precisions. In this work we develop a technique using such GPs to better analyse systematic trends in exoplanet transmission spectra taken in either MOS/MXU modes caused by the GRIS_600z grism of FORS2. Our method can provide an effective tool to interpret transmissions signals in future observations with other telescopes in the presence of instrumental systematics.
Ammonia in carbon rich stars
Etmanski, Bartosz
Ammonia has been found to exists in circumstellar envelopes of evolved starsin amounts that exceed predictons of the current chemical models for C-rich AGB stars.HIFISTARS Team clearly detected the ground-state rotational transition NH3 JK = 10 -- 00at 572.5 GHz in envelopes of few C-rich AGB stars, including earlierdetection in IRC+10216. We present results of the non-LTE radiativetransfer modelling conducted with the goal to derive NH3 abundances in these sources. The model of ammonia includes IR radiative pumping via ?=1 vibrationalband at 10 µm. Theoretical predictions of the model are applied forthe analysis of excited rotational ammonia lines available for some of thesources, in particular for IRC+10216.
ALMA Study of the Envelope and Outflow Rotation in the young Classs 0 Protostar B335
Etoh, Yuki
To reveal how protoplanetary disks, precursors of planetary systems, are formed around protostars, we have analyzed ALMA archival data of the young Class 0 protostar B335. We have identified the rotating motion of molecular gas around the protostar, furthermore, a sign of the flip of the rotational vector, “counter-rotation”. These results should reflect the earliest stage of the disk formation around B335. The molecular outflow as seen in the 12CO (2-1) emission in B335 consists of small (~100 au) “bullets” and symmetric “parabolas” along the east-to-west direction. The moving velocities of the bullets reach ~200 km s-1, much faster than typical velocities of molecular jets driven by low-mass protostars. The dynamical time of those jets is estimated to be as short as 15 years. Those results indicate the possibility that we will be able to obtain real time movie of the motion of the bullets with additional ALMA observations. Furthermore, both of the bullets and parabola exhibit rotation, implying the extraction of the rotational angular momenta from the circumstellar disk. In this presentation, we will report these results and discuss the anticipated results which will be obtained with the future ALMA observations.
Time Domain processing and analysis of the photometric Gaia Data
Eyer, Laurent
The data processing of the Gaia mission is an enormous challenge due to the amount of data to be curated, its interdependence, the scanning law and instrument artefacts. This does not concern only the astrometric solution, but also the calibration and processing of different types of photometric or spectroscopic time series. Assigned to nearly 1.7 billion celestial sources, the Gaia photometric times series represent over 119 billion photometric measurements (SM, G, BP, RP, and subsets of per-CCD data) that were processed for the Gaia Data Release 2. We analysed these data with a unique mixture of statistical and machine learning methods, run on a parallel platform developed and hosted at the Gaia Data Processing Centre in Geneva with distributed database Postgres-XL as a newSQL data backbone.
Ultraluminous X-ray sources
Fabrika, Sergei
The origin of ultraluminous X-ray sources (ULXs) in external galaxies whose X-ray luminosities exceed those of the brightest black holes in our Galaxy by hundreds and thousands of times is mysterious. The X-ray spectra indicate a presence of hot winds in their accretion disks. The new results were discovered, ULX-pulsars and high-velocity outflows up to 0.2c. They are in accordance with the super-Eddington accretion. Here we analyze the variability properties of only five ULXs which show flat-topped noise (FTN) and QPO in their X-ray power density spectra. In each ULX the mass accretion rate may vary up to 3-4 times, and with decreasing the accretion rate (reduction the spherization radius), the hardness ratio and luminosity increase, FTN and QPO may dissapear. We may potentially measure the black hole masses using X-ray luminosities. However, the strongest evidences come from optical spectroscopy. The spectra of the ULX counterparts are very similar to that of SS433 and WNL type (late nitrogen Wolf-Rayet stars) or LBV (luminous blue variables) in their hot state. We find that the spectra do not originate from WNL/LBV type donors but from strong winds in the accretion disks, which have similar physical conditions as the stellar winds from these stars. The results suggest that the bona-fide ULXs have supercritical accretion disks.
Ultraluminous X-ray sources
Fabrika, Sergei
The origin of ultraluminous X-ray sources (ULXs) in external galaxies whose X-ray luminosities exceed those of the brightest black holes in our Galaxy by hundreds and thousands of times is mysterious. Their X-ray spectra indicate a presence of hot winds in their accretion disks. The new results were discovered, ULX-pulsars and high-velocity outflows up to 0.2c. They are in accordance with the super-Eddington accretion. Here we analyze the variability properties of the only five ULXs which show flat-topped noise (FTN) and QPO in their X-ray power density spectra. In each ULX the mass accretion rate may vary up to 3-4 times, and with decreasing the accretion rate (reduction the spherization radius), the hardness ratio and luminosity increase, FTN and QPO may dissapear. We may potentially measure the black hole masses using X-ray luminosities. However, the strongest evidences come from optical spectroscopy. The spectra of the ULX counterparts are very similar to that of SS433 and WNL type (late nitrogen Wolf-Rayet stars) or LBV (luminous blue variables) in their hot state. We find that the spectra do not originate from WNL/LBV type donors but from strong winds in the accretion disks, which have similar physical conditions as the stellar winds from these stars. The results suggest that the bona-fide ULXs have supercritical accretion disks.
Studying gas-rich dwarf galaxies with the minihalo model
Faerman, Yakov
Over the last decade, sensitive surveys in the 21-cm have revealed a population of isolated Ultra-Compact High-Velocity HI Clouds (UCHVCs). Some of these objects were suggested as potential dwarf galaxy candidates. Deep optical observations have been carried out to search for associated stellar populations, and have lead to the discovery of several ultra-faint dwarfs (Leo P, Pisces A & B, SECCO 1), allowing mass and distance measurements. Together with other dwarf galaxies in the Local Volume, they allow us to address various problems, such as star formation in different regimes, physical processes important for structure formation and evolution, and maybe provide hints for the nature of dark matter (DM). However, many HI-selected galaxy candidates may harbor only small numbers of stars or none at all.In our work we develop methods to study the properties of dwarf galaxies and galaxy candidates using 21-cm observations. We model their gas distributions using the minihalo model (Sternberg, McKee and Wolfire 2002), as gas clouds in hydrostatic equilibrium in DM halos, heated and ionized by the metagalactic radiation field. In Faerman, Sternberg and Mckee 2013 we show that high-resolution 21-cm observations (such as those carried out by Adams et al. 2016) can be used to estimate (presently unknown) distances to the UCHVCs. Alternatively, if the distances to them are measured by some other method, HI column density profiles can be used to constrain the DM halo properties. We use 21-cm observations of Leo T as a test case for our methods. In a follow-up work (Faerman, Goettlib and Sternberg, in prep.) we model new, deep HI observations of Leo T (Adams and Oosterloo, in press) to estimate the pressure of the intergalactic medium in the Local Group. Application of our methods to future 21-cm observations from instruments such as EVLA, APERTIF, ASKAP and SKA will allow us to realize the potential of gas-rich, ultra-faint galaxies as astrophysical laboratories.
Warm/Hot Galactic Coronae
Faerman, Yakov
X-ray absorption studies of QSO sightlines provide evidence for a hot gas (~1e6 K) corona around the Milky Way in the form of highly ionized oxygen (OVII and OVIII). Extended structures of hot gas around galaxies are also suggested by galaxy formation theory and numerical simulations. Recent observations of OVI absorption in the UV show the existence of warm gas around L* galaxies in the low redshift universe. Due to the challenging nature of the observations, many questions remain open. Where exactly does the gas reside and what are its properties? What is the extent and the total mass of the corona? These questions are important to our understanding of galaxy evolution properties and are linked to a number of other topics such as star formation and stellar feedback, properties of dwarf galaxies and IGM gas accretion onto galaxies. We construct unified models (isothermal and adiabatic) for the warm/hot corona which successfully reproduce a wide range of observations (UV, X-ray and other). In our models, the corona is a large-scale structure, extending to the virial radius of the MW, and has a significant gas mass, ~1e11 M_sun. Such coronae may serve as galactic gas reservoirs, enabling prolonged periods of star formation and providing a solution to the galactic "missing baryons" problem in the Local Universe.
BRIDGING THE GENDER GAP IN STEM THROUGH GIRLS' ASTRONOMY CAMP, ABUJA -AN OAD FUNDED PROJECT
Fagbemiro, Olayinka
This project addressed first, the challenge of lopsidedness in the elementary school enrolment. We decided to host an astronomy camp for girls because of the issues associated with girl-child education in northern Nigeria. The term ‘girl-child’ refers to a female between the ages of 6-18 years. The gender apartheid places the girl-child in a disadvantaged position, where her potentials are suppressed and self-actualization is not achieved. The girl therefore, becomes a victim of a pre-existing socio-cultural male exaggerated superiority. Furthermore, on the account of gender, girl-children are subjected to all multiple forms of oppression, exploitation and discrimination. Girl-child education has then become a major issue of concern in most developing countries of the world today, especially in sub-Saharan Africa, where a large number of young girls do not attend school. According to UNICEF (2007), the global figure for out-of-school children is estimated to be 121 million, out of which 65 million (approximately 53.8%) were girls and over 80 percent of these girls live in sub-Saharan Africa. The northern Nigeria have the country’s worst girl child education, highest female illiteracy, highest adolescent girl marriage, highest under 15 child bearing, and highest risk of maternal death and injury. The scorecards underline the links between poor educational attainment for girls, forced marriage of underage children, and under age child bearing. The project encouraged the female children to aspire to STEM just as much as their male counterparts and also to encourage parents to enrol their female children and also aspire for them to be great scientists in the nearest future just like many of the female instructors that participated in the project. The focus is on the female children in other to bridge the gap the exists between male and female children enrolment particularly across the northern part of Nigeria.
Characterization of high z quasar hosts in the ELTs era.
Falomo, Renato
Quasars represent our main lighthouses to explore the high z Universe and to investigate the processes of formation of galaxies and their central supermassive black holes over the cosmic time.The characterization of the key parameters as the galaxy mass, size, morphology and their close environments are nowdays hindered by the limited spatial resolution and sensitivity of the present instrumentation. We investigate here the expected capabilities of the future observations obtained with near-IR adaptive optics imagers foreseen for Extremely Large Telescopes. Detailed simulations are presented to evaluate the accuracy of those observations, under different observing conditions (seeing, strehl, PSF stability, background, etc.), to characterize the main properties of the galaxies hosting an active nucleus in the early Universe.
Feeding and Feedback in the most luminous, heavily dust-obscured quasars
Fan, Lulu
The massive galaxies and their central supermassive black holes (SMBHs) co-evolution scenario proposes that a gas-rich major merger can trigger the central starburst and feeding the SMBH accretion, and then star formation has eventually been quenched by quasar feedback. In this evolutionary sequence, dust-obscured quasars could represent the critical transition phase between starburst and unobscured quasars, and are perfect candidates for studying the feeding and feedback of luminous quasars. We studied the physical properties of a recently discovered population of hyper-luminous, heavily dust-obscured quasars in WISE all-sky survey (so-called Hot DOGs). Their bolometric luminosities can exceed 1014 Lsolar, which make them be among the most luminous objects in the universe (Fan et al. 2016b). The high merger fraction has been found with HST imaging, supporting the merger-triggered feeding scenario (Fan et al. 2016a). Molecular gas, as the feeding fuel, has been detected in three Hot DOGs with recent ALMA observations (Fan et al. 2018b). Our ALMA CO line observations also show the possible evidence of gas-rich merger and outflow in these objects. The stellar masses of their hosts are expected to be massive, which is supported by our case study (Fan et al. 2018a). The extreme features of Hot DOGs can be related to their dense environment (Fan et al. 2017). With the NIR and narrow-line imaging, we are investigating the environment around two targeted Hot DOGs (Fan et al. in prep). However, only a tip of an iceberg of the mystery of the heavily dust-obscured quasars has been revealed due to the observational limitation. With the superb abilities of NIR/MIR imager and spectrograph mounted on ELT, it will be a golden time to reveal the comprehensive properties of these population in the transition stage, such as measuring BH masses, decomposing the host contribution, studying the surrounding large scale structure.
The halo of the Andromeda Galaxy probed with planetary nebulae
Fang, Xuan
It is now widely accepted that large galaxies grow in mass through continual accretion of smaller ones. These galaxy mergers result in a smooth, extended halo of loosely bound stars surrounding the central galaxy. Remnants of the cannibalized galaxies also exist in the halo in the form of various substructures like the stellar streams. Previous wide-field photometric surveys already revealed numerous stellar streams in the outer halo of the Andromeda Galaxy (M31), a nearby large spiral system that resembles our Milky Way in morphology. In order to study the properties of these substructures and backtrace the merger history of M31, we have been obtaining deep spectroscopy of planetary nebulae (PNe) that are associated with the halo streams of M31, using the 10.4m Gran Telescopio Canarias (GTC). We found that all bright PNe in M31 so far targeted by our GTC spectroscopy are metal-rich (nearly solar oxygen) and mostly evolved from low-mass (<2 solar mass) stars that formed ~2 to 5 Gyr ago; they probably have different origins from the underlying, smooth, mostly metal-poor halo of M31. In this contribution, I will report our new findings of this project, discuss the possible origin of these halo PNe, and elucidate their significance in the context of the current grand picture, that M31’s giant halo is a result of complex galactic interactions and merger processes.
Next-generation ultra-stable lasers for optical clocks and space-time metrology
Fang, Bess Yiyuan
Recent progress in time and frequency metrology has led us to optical clocks with unprecedented performance. One of the key constituent of these clocks is the ultra-stable lasers whose fractional frequency fluctuations are typically around one part in 10^16 today, hindering further improvement of the stability of optical clocks. Frequency-locking a laser to a spectral hole in rare-earth doped crystals at cryogenic temperature has been shown to be a promising alternative to the more traditional use of high finesse Fabry-Perot cavities when seeking a laser with a very high short term stability. We demonstrate here a novel technique for achieving such stabilization, based on generating a heterodyne beat-note between a master laser and a co-propagating slave laser whose dephasing caused by propagation near a spectral hole generate the error signal of the frequency lock. The master laser is far detuned from the center of the inhomogeneous absorption profile, and therefore exhibits only limited interaction with the crystal despite a potentially high optical power. The demodulation and frequency corrections are generated digitally with a hardware and software implementation based on a field-programmable gate array and a Software Defined Radio platform, making it straightforward to address several frequency channels (spectral holes) in parallel. Our technique can potentially improve the frequency stability of stablized lasers by orders of magnitude, thereby improving the performance of optical clocks and related time and frequency distribution.
Promoting Science Communication with 5 Senses
Farmanyan, Sona
The present study is proposed to introduce the methods and for promoting science communication with all our 5 senses. We will show how to present space related topics to general public with our 5 senses and how to gain new enthusiasts of the Universe. The basic processes of communication that explain how different publics deal with scientific information will be analyzed and we will apply these insights so as to help improve communication practices in the field of science. Special focus will be given on the science-society relationship and the usage of the persuasive and effective means like science museums, science exhibitions, science festivals, science cafes and pubs, public lectures, talks and discussions, scientific journalism and scientific tourism. We will suggest science communicators to use entertainments including humor, storytelling and metaphors. Scientists even can be trained in some of the techniques used by actors to improve their communication for acting in science shows. Science communication may also be realized by websites and social media platforms. The positive outcome of the usage our 5 sense in science communication such as the rejection of superstitious beliefs, astrology and numerology will be pointed out. We conclude with future tendencies of science communication and benefits of the scientists and young researchers who are actively involved in science outreach activities.
Identification and age estimation of asteroid pairs and clusters
Fatka, Petr
We will present a method for identification of young (age < ~2 Myr) genetically related asteroids and estimation of the time of their separation. Assuming a gentle break up event (e.g., by rotational fission), the studied paired or clustered asteroids had very low relative velocities at the time of separation, on an order of 1 m/s, and their distances in the space of mean orbital elements are still rather low at present. We identified candidate pairs by calculating the probability of that they are a random orbital coincidence of two unrelated asteroids from the background asteroid population. For candidates with low probability of being a random couple, we performed backward integrations of their geometric and Yarkovsky orbital clones, looking for close and slow encounters between them. The geometric clones were generated to cover the normal matrix of the orbital solution of given asteroid, and to each clone we gave a randomly selected value of drift in semimajor axis due to the Yarkovsky effect in the range of possible values for the given asteroid’s size. By analyzing the close and slow clone encounters, we confirmed reality of the studied asteroid pair or cluster and estimated the time of their formation. We will overview the method and show our results for 13 asteroid clusters and almost 100 asteroid pairs. We will also point out a few most interesting cases of very young asteroid pairs and an asteroid cluster that underwent a cascade disruption.
An upper limit on the energy density of the gravitational wave background and on variations of the gravitational potential measured with the pulsar timing.
Fedorova, Viktoriya
Timing of millisecond pulsars gives a possibility to establish an upper limit on the energy density of the gravitational wave background and on variations of the gravitational potential in the vicinity of the Solar System. Measurements are based on pulsar timing observations at Parkes observatory in 1995 — 2010. The fractional instability of the difference of the pulsar ensemble and the terrestrial time scales PTens−TT(BIPM2011) at the interval 15 yr σz = (0.6 ± 1.6)·10−15. This value corresponds to the upper limit of the energy density of the stochastic gravitational wave background Ωg h2 ∼10−10 and variations of the gravitational potential ∼ 10−15 at frequency 2 · 10−9 Hz.
Are Low-Luminosity AGN powered by Compact Jets?
Fernández Ontiveros, Juan Antonio
The vast majority of AGN belong to the low-luminosity class (LLAGN): they exhibit a low radiation efficiency (L < 1042 erg/s; L/Ledd < 10-3) and the absence of the big blue bump in their spectrum, a signature of the accretion disc. For a sample of nine prototype nearby LLAGN, a multi-wavelength dataset including radio, IR, optical/UV and X-ray measurements with a few tenths of arcsec resolution has been collected. The high-angular resolution SEDs allow us to isolate the true nuclear emission and avoid the contamination from the underlying host galaxy. The main results are: i) the mid-IR bump, indicative of thermal emission from the torus, is missing in LLAGN; ii) the continuum emission of these nuclei is largely described by a self-absorbed synchrotron spectrum, suggesting that jet emission dominates the overall energy output in these objects; and iii) the far-UV continuum, inferred from photoionisation simulations, is in agreement with the extension of the power-law continuum observed in the IR-to-optical range. The very steep slope found in the power-law continuum -with a spectral index in the 1-3 range- suggests that a large number of LLAGN are powered by young and compact jets with either very high radiative losses or thermalised electron distributions at their base.
Asteroid mass determination with INPOP planetary ephemerides
fienga, agnes
In this poster we will give new results obtained with our latest INPOP planetary ephemerides. We will specifically focused on the determination of about 200 asteroid masses. We will explain the method and compare these evaluations with those obatined by other methods. Finally we will try to propose some possible interpretation in terms of densities.
Astrometry of geodesic satellites with GAIA
fienga, agnes
In this poster we will present first results obtained with a trtacking campaign of mainly GNSS satellites simultaneously with the Meo laser tracking facility and the C2PU telescope both at the Calern site.CCD images of the satellites were obtained during the laser tracking sessions and flashes of the laser reflections are visible. In using these flashes, astrometry was obtained in using the GAIA DR1 and accurate angular positions related to the GAIA reference frames were obtained.
Grid of realistic CSPNs atmosphere models
Fierro-Santillán, Celia
We present a grid of stellar atmosphere models, covering the region of the Central Stars of Planetary Nebule (CSPNs) in the H–R diagram. The models were calculated using the stellar atmosphere code CMFGEN ( Hillier and Miller 1998) in ABACUS supercomputer . The parameter space has 6 dimensions: surface temperature of the star, also called the effective temperature (Teff ), luminosity (L), metallicity (Z), and three stellar wind parameters, the exponent (ß) of the wind velocity law, the terminal velocity (Vinfinity), and the volume filling factor (Fcl ). The input parameters to the models were taken from the evolutionary traces of Miller Bertolami (2017), producing realistic models of atmospheres, which can be used as input to photoionization codes such as CLOUDY (Ferland et al. 1998)
Reducing spectral analysis time: Mega-database of CMFGEN models and FITspec for automatic fit of O type stars
Fierro-Santillán, Celia
We obtained the stellar parameters of a sample of O type stars using a database of 40 000 stellar atmospheres models in a six-dimensional space together with automatic adjustment tools. The spectra were obtained with the 2.1 m telescope of the OAN in San Pedro Mártir, México. The models were calculated in the cluster ABACUS of the Laboratorio de Matemática Aplicada y Cómputo de Alto Desempeño ABACUS-CINVESTAV. We use the CMFGEN code (Hillier & Miller 1998) to calculate the models and FITspec code (Fierro et al. In prep.) for the automatic fit of spectra; which performs a quantitative spectroscopic analysis based on the equivalent widths of He I, He II, and Balmer lines, reducing the time needed for the spectral analysis from months to hours, optimizing in this way the calculations.
The Girls' Day at the Museum of Astronomy
Figueiró Spinelli, Patrícia
As it is widely known, the percentage of women in the so-called hard sciences is significantly lower than the number of men. Science and gender equality are both vital to achieve sustainable development throughout the world. As such, United Nations Educational, Scientific and Cultural Organization (UNESCO) is encouraging worldwide efforts to overcome gender disparities. The Girls' Day at the Museum of Astronomy and Related Sciences (MAST, Portuguese acronym) in Rio de Janeiro, Brazil, is one of such initiatives. It has the aim of discussing about the persisting inequality in science with its participants, bringing women scientists and girls together as well as presenting the beauties of science through astronomy outreach activities. In its four editions, the attendance of the event was very satisfactory and the discussions raised in during the promoted roundtables were inspiring. These debates were transmitted on-line and followed by hundreds of viewers. In this talk, we will discuss the most important aspects of the events and lessons learnt. We will also reflect upon the role of science museums in creating equitable experiences for its public, including contemporany discussions in its agenda without losing the evidence of how our culture and knowledge evolve.
GalileoMobile - 10 years of itinerant astronomy
Figueiró Spinelli, Patrícia
GalileoMobile is an itinerant, non-for-profit outreach project that shares astronomy with communities worldwide. Since its inception in 2008, GalileoMobile has reached 1,400 teachers and 16,000 students, donating more than 100 telescopes and organizing public events for more than 2,500 people in 14 countries. GalileoMobile shares astronomy across the world in a spirit of inclusion, sustainability, and cultural exchange to create a feeling of unity under the same sky. GalileoMobile's 10 years' journey has been remarkable from its very beginning, when we had our first meetings to prepare our contribution to the International Year of Astronomy. Since then, we have envisioned astronomy as a tool to bring people together, overcoming cultural and political difference, and this is exemplified by our latest project “Columba-Hypatia: Astronomy for Peace” in Cyprus, in 2017. It also encouraged peace and mutual understanding by acknowledging, alongside modern scientific views, traditional knowledge related to astronomy and the cosmovision of the communities visited. In this respect it is important to highlight the continuous work of the project with indigenous communities in Brazil. Over the past 10 years, GalileoMobile has collaborated with the major astronomical organizations worldwide and has been identified by the European Commission as an example of Best Practices in Science Education for Responsible Citizenship (European Union 2015). The project has also inspired different organizations and individuals to organize similar initiatives in countries such as India, Nepal, Colombia, Dominican Republic and Chile. With 3 documentaries about our expeditions, the project also considers the importance of audiovisual media to share our experience with a wide audience. In this talk, we will present major achievements and lessons learnt and discuss our plans for the 10th anniversary celebration, as well as the future of GalileoMobile.
Our Solar Siblings: Connecting students, teachers, scientists, amateurs and projects through robotic telescopes
Fitzgerald, Michael
Our Solar Siblings (OSS, www.oursolarsiblings.com) is an astronomy education project based in Australia but accessible internationally. It has five main goals (authentic use of science data by students, student understanding of the universe, student understanding of science, student attitudes towards science and enabling student research). These are addressed with three main approaches, A) facilitating in-class use by everyday teachers, B) Direct and indirect mentoring of student research projects and C) providing support and development for other similar projects and approaches around the world. The first two approaches have been covered in detail elsewhere before, but in this presentation, the third approach is presented as a model in bridging different communities and connecting scientists and teachers for education and outreach purposes.Our Solar Siblings (OSS) openly provides materials, mentoring, guidance, self-paced training material and support to multiple endeavours across the globe as well as access to a customized data product pipeline for optical data designed to provide accessible, usable, science-grade data to teachers and student researchers. Frequently, customized add-ons or forks from this pipeline are created to facilitate new ideas and/or streamline the administration for non-OSS projects. OSS’s more-than-citizen-science project, the “Local Lyrae Survey” will be presented, the follow-up projects for Kepler eclipsing binaries and TESS exoplanets undertaken by other projects but supported by OSS and the Pro-Am partnerships that are being developed through increasing the data quality and homogeneity of multiple streams of amateur data is presented. How research scientists have been involved at a high level in all of this will also be outlined as well as the simple portal that facilitates research scientist outreach and teacher usage of robotic telescopes.
astroEDU Core Project: Provision of K-10 Activity Collections for Common Curriculum Goals
Fitzgerald, Michael
With the recent completion of a major review (Salimpour et al. 2018) of the curricula around of the OECD countries, China and South Africa, we can now identify common astronomical themes that run through most formal school curricula in the developed world. Here we present the first astroEDU Core Project: To create a collection of activities and related teacher training materials for the common astronomy elements of primary and junior high school.This presentation outlines the project and launches a call-out to research astronomers and astronomy educators alike to contribute to a themed collection of activities and training materials. astroEDU intends to provide a complete set of coherent activities that could be used in elementary and junior high schools worldwide. In doing so, astroEDU aims to support IAU Office of Astronomy for Development activities in promoting development of astronomy education programmes internationally.Activities submitted are peer-reviewed by an educator and a professional astronomer which provides credibility to the activities. astroEDU activities are open-access in order to make the activities accessible to educators around the world while letting them discover, review, distribute and remix the activities. astroEDU is endorsed by the International Astronomical Union meaning each activity is given an official stamp by the international organisation for professional astronomers.
Long-Term evolution of planetary system in stellar clusters
Flammini Dotti, Francesco Maria
Most stars, and perhaps even all stars in the Galaxy, form in crowded stellar environments. Most of such star forming regions typically dissolve within ten million years, while others remain bound stellar groupings for hundreds of millions to billions of years, and then become the open clusters or globular clusters that are present in our Milky Way galaxy today. It is commonly accepted in that a large fraction of stars in the Galaxy hosts planetary companions; even binary star systems are known to host exoplanets. To understand the origin and dynamical evolution of exoplanet systems, it is necessary to carefully study the effect of their environments, i.e., that of the star forming region in which they formed and in which spent their first millions of years, and that of the Galactic field, open cluster, or globular cluster in which they spend the remaining part of their lives. Our study combines theoretical estimates with state-of-the-art numerical simulations. Here, we present the initial results of our numerical study of the evolution of planetary systems in star clusters, in which we model the effects of neighbouring stars and the external Galactic tidal field on existing planetary systems. We aim to study a wide variety of planetary systems and surrounding environments, to obtain a comprehensive picture of the conditions under which external perturbations are important or negligible. To carry out our simulations, we combine the planetary systems N-body evolution code REBOUND with the NBODY6++ star cluster evolution code in the AMUSE multi-physics environment. With our study we will be able to constrain the effect of external perturbations of different environments on the planets and debris structures of a wide variety of planetary systems, which may play a key role for the habitability of exoplanets in the Universe.
Bar effects on abundance profiles in spirals
Florido, Estrella
We will present results obtained from the analysis of abundance profiles in spirals. These are based on a compilation of spectroscopic published data on HII regions in nearby spirals. In particular, we will focus on the central abundances and gradients in barred and unbarred galaxies separately, for both the oxygen and the nitrogen-to-oxygen abundance ratio.
The Juno gravity science experiment
Folkner, William
The Juno spacecraft entered orbit around Jupiter in July 2016 in a 53-day orbit. At closest approach to Jupiter, perijove, measurements of the Doppler shift of the Juno radio signal are made by the NASA Deep Space Network. These measurements have been used to estimate the Jupiter gravity field, tidal response to the Galilean satellites, and the precession and nutation of the Jupiter spin axis. Doppler data from the first few perijoves provided estimates of the low-order even zonal harmonics that provided significant improvements on previous estimates from Pioneer, Voyager, and Galileo missions. Subsequent date showed clear evidence of odd low-order zonal harmonics, that are explained by the zonal winds observed from images of the cloud tops extend to a depth of 3,000 km. The estimated harmonics provide significant constraints on the interior structure of Jupiter. We report on the current status of the gravity estimates and the expected results from the rest of the mission duration.
The maser emitting structure and time variability of the SiS lines J=14-13 and 15-14 in IRC+10216
Fonfria, Jose Pablo
AGB stars are important contributors of processed matter to the ISM. However, the physical and chemical mechanisms involved in its ejection are still poorly known. This process is expected to have remarkable effects in the innermost envelope, where the dust grains are formed, the gas is accelerated, the chemistry is active, and the radiative excitation becomes important. A good tracer of this region in C-rich stars is SiS, an abundant refractory molecule that can display maser lines, very sensitive to changes in the physical conditions. We present high angular resolution interferometer observations (HPBW>0.25") of the v=0 J=14-13 and 15-14 SiS maser lines towards the archetypal AGB star IRC+10216, carried out with CARMA and ALMA to explore the inner 1" region around the central star.The observations reveal a complex emitting structure with three major components: (1) two blue- and red-shifted strong spots, (2) an elongated component around the systemic velocity, and (3) a weaker extended emission. We have modeled the observations in detail with a 3D radiation transfer code finding that they cannot be reproduced only by thermal emission. About 75% of the total emission is modeled by several maser spots with different velocities and a thin shell-like maser structure, necessary to reproduce the extended emission. The remaining 25% is thermal emission.These observations have been complemented with a spectral monitoring of several SiS lines carried out with the IRAM 30m telescope every 14 days from 2015 to present. The intensity of some spectral maser components strongly depend on the stellar pulsation while other maser components show a mild variability. We also discovered a significant phase lag of ~0.2 between the maser and the NIR light-curves.The innermost envelope of IRC+10216 is a quite complex region substantially affected by the evolution of the central star. This and future works about this region will shed light on the matter ejection problem.
The origin of the angular momentum of galaxies: cosmological tidal torques plus the Coriolis force
Font, Joan
We present a theoretical model which can contribute to the observed relation between the specific angular momentum in galaxies and their masses. The most recent observations point to a scenario in which, after recombination, the matter was organized around voids, which acquired rotation by tidal torque interaction. Subsequenctly a combination of the effects of the gravitational collapse of gas in protogalaxies and teh Coriolis forcé due to the rotation of the voids produced the rotation of spiral galaxies. Then the tidal interactions between those objects in the shells of the voids far away from the void rotation axis interact with higher probability with others similarly situated in a neighbouring void, offer a mechanism for transforming some of the galaxies into ellipticals, yielding objects with low net angular momentum, the ellipticals. The model gives an explanation for those observations which suggest a tendency of galatic spins to align along the radius vectors pointing towards the centres of the voids for ellipticals, and parallel to filaments and sheets in the void surfaces for spirals. Furthermore, while in simpler tidal torque theory the angular momentum supplied to galaxies diminishes drastically with cosmic expansion, in this model the Coriolis force due to void rotation ensures almost continuous angular momentum supply. Using the Emmy Noether theorem in Lagrancian Mechanics we obtain a theoretical relation between the angular momentum of galaxies and cosmic time, comparing our results with numerical models and observations.
Bar-disk angular momentum coupling: implications for disk evolution
Font, Joan
We use pattern speeds which are well measured, using the Font-Beckman method, for both the bars and the spiral arm systems of a sample of 79 disk galaxies to explore the dynamical relation between the two systems. There is a close correlation between the two pattern speeds. For a sub-set of objects where the Outer Lindblad Resonance of the bar system coincides with the corotation radius of the spiral system, this correlation is 0.96, and for the full set of objects the correlation is 0.81, for the relation Omegaspiral = 0.5Omegabar. We also plot the ratio of the bar pattern speed to that of the outer disk (defined at R25) against the ratio bar mass: disk mass, showing that the more massive the bar the more slowly it rotates relative to the outer disk. By comparing the rate of change of the angular velocity of the bar with the rate of change of its angular momentum we show clearly that the bars in our galaxies are being systematically braked by angular momentum transfer to the outer disc and/or dark halo. Using simulations it should be possible to quantify the two effects separately.
A Multi-Frequency Radio Continuum Study of the Magellanic Clouds
For, Bi-Qing
We present the first SKA precusor Murchison Widefield Array (MWA) radio continuum maps of the Magellanic Clouds. In this talk, we discuss the overall radio continuum morphology between 76 and 227 MHz and compare them_x005F with neutral hydrogen maps, 1.4 GHz continuum maps and optical images. We also measure the integrated flux densities and derive the global spectral indices. Variation of diffuse emission is noticeable across the Large Magellanic Cloud (LMC) but absent across the bar of the Small Magellanic Cloud (SMC). The radio spectral index maps reveal distinctive flat and steep spectral indices for the HII regions and supernova remnants, respectively. We find strong correlation between HII regions and Halpha emission. Using a new 150 MHz--Halpha relation as a star-formation-rate indicator, we estimate global star formation rates for the LMC and SMC, respectively. Information regarding data release will be provided.
Boosting the Lya line in Pop III Galaxies from Stochastic IMF Sampling
Forero-Romero, Jaime
The sensitivity of the Lya flux to the high-energy end of the galaxy spectrum makes it subject to stochastic sampling of the IMF. Stochasticity introduces a dispersion in the predicted nebular line fluxes around the deterministic value by as much as a factor of ~4. Stochastic sampling also affects the expected Equivalent Width making it possible to have an EW as high as ~3 times the deterministic value. Stochastic models seem to be required for a proper interpretation of future distant galaxy detections to be made with facilities such as JWST and other large, groundbased telescopes.
Deep Time Astronomy: the next 5000 years
Forero-Romero, Jaime
Some evidence of astronomical measurements can be traced to 5000 years in the past. What can we hope for in the next 5000 thousand years? To bring that future closer to us, I will present some current scientific cases that will benefit from a continous data taking effort for the next 5000 thousand years. After summarizing these cases I will present the possible challenges that lie ahead for this undertaking in terms of facilities, technologies and data curation.
Application of method FAIR to identify mean motion resonances in the Kuiper belt
Forgács-Dajka, Emese
Mean motion resonances (MMRs) play an important role in shaping the dynamics of the planetary and the Solar system bodies. MMRs in the Solar system usually occur between a planet and small bodies, e.g. the members of the Hilda group of asteroids are in a 3:2, while the Trojan asteroids are in a 1:1 MMR with Jupiter. MMRs between terrestrial planets and particular members of the asteroid family Hungaria can also be found. The existence of the Kirkwood gaps clearly indicates, the dynamical structure of the main belt is shaped by the MMRs between the asteroids and Jupiter. There are many Kuiper belt objects that are locked in various MMR with Neptune, such as the plutinos sharing their orbits with Pluto.Based on the geometrical meaning of the resonance variable, an efficient method has been introduced and described in our recent paper (Forgács-Dajka, Sándor & Érdi, 2018), by which mean motion resonances can be easily find without any a priori knowledge on them. The efficiency of this method - named FAIR - is clearly demonstrated by using known exoplanets engaged in mean motion resonances, and also some members of different families of asteroids and Kuiper belt objects being in mean motion resonances with Jupiter and Neptune, respectively. In this research we systematically apply the method FAIR to the Kuiper belt objects to identify the dynamically relevant MMRs between them and Neptune or Uranus. Our investigation may help to find possible new families of Trans Neptunian Objects in resonance with the outer gas giants.
Time dependent properties of sunspot groups
Forgács-Dajka, Emese
The daily area of sunspots and sunspot groups is one of the most important parameters used to characterize the development of spot and spot groups. The area of the spot groups is tightly connected to their magnetic flux (Wang & Sheeley, 1989), hence its time dependence reflects the development of the magnetic field of the Sun, consequently the growth and decay of spot groups significantly affect the strength and topology of magnetic structures within the Sun’s atmosphere. Analysis of the phases of spot development is essential to understand the magnetic topology of the Sun, the evolution of the solar cycle and the hidden mechanisms driving it. For a comprehensive review of earlier work related to the analysis of spot development and decay, and the characteristics of spot groups, see e.g. van Driel-Gesztelyi & Green (2015).Here we apply hierarchical Bayesian modeling to analyze the time dependence of spot group areas in a large sample composed of various databases spanning 130 years. For a carefully selected but unbiased sample, we modelled the time evolution of spot group areas with a skew-normal distribution to determine the existence of any asymmetry in spot growth/decay. Our primary selection criterion guarantees that only spot groups with a well-defined maximum area are taken into account. We analyzed the covariance of the resulting model parameters and their correlations with the physical parameters of the sunspots and the ongoing solar cycle.
Studying the influence of "rogue" sunspots on solar activity using sunpot database
Forgács-Dajka, Emese
Hathaway (2010) gives a comprehensive overview of observations and phenomenological interpretation of the solar cycle via sunspot numbers and other indicators of solar activity. The variations of sunspot numbers from cycle to cycle are generally attributed to the variations of the internal magnetic field generated by the Sun. Even though this assumption seems very plausible, it is important to note that to date, the mechanism, by which the magnetic field generated by the dynamo emergence on the surface in the form of solar spots of concentrated flux, is not precisely understood. The correlation between the internal magnetic field and sunspot numbers is far from linear and the concept of the 11/22 year activity cycles can no longer be supported, since the amplitude and envelope of the periods vary from cycle to cycle and the duration of the periods spans the range of 9 to 14 years. Various papers discuss the possibilities of explaining the solar cycle on the basis of dynamo models, see Charbonneau (2010) for a review, and a wide range of precursor models exists which attempt to predict the amplitude and/or time scale of the upcoming cycle based on measurements of the surface magnetic field, see Hathaway et al. (1999). Cameron et al. (2014) showed that some individual sunspots, which appear at unusual locations and times or show an unusual configuration, can affect the further course of solar activity. Nagy et al. (2017) found that certain statistically outlying, „rogue” sunspots can even lead to the total wipe-out of the cycle. The aim of our investigation is to statistically analyze various databases of sunspot data for the last 130 years and identify the possibly „rogue” spots and uncover the connections between their emergences and the properties of other spots of the ongoing and the upcoming cycles.
Correspondence of Many-flavor Limit and Kaluza-Klein Degrees of Freedom in the Description of Compact Stars
Forgács-Dajka, Emese
However, there is no direct observation of the inner structure of a compact star, some physical properties like the measured mass-radius relation, moment of inertia, rotation period, magnetic field and the soon-to-be-available gravitational wave observations support to build and parametrize realistic equations of state (EoS) in the non-perturbative and high-density QCD (Quantum Chromodynamics) regime. We present the correspondence between (non)-interacting multi-hadron fermion star equation of state in the many-flavor limit and the degrees of freedom of a Kaluza – Klein compact star. Many flavors can be interpreted in this framework as one extra compactified spatial dimension with various, more-and-more massive hadron state excitations. The effect of increasing the degrees of freedom was investigated on the equation of state and in connection with the mass-radius relation, M(R). This theory led us to check gravitational theories beyond the post-Newtonian case. Here, we also present whether we would be able to measure the effect of these extra dimensions by gravitational wave detectors in the future.
Interactions of Supermassive Black Holes with Hot Baryons in Galaxies, Groups, and Clusters
FORMAN, WILLIAM
Supermassive black holes (SMBHs) play key roles in galaxy, group, and cluster evolution. This is most clearly seen in the “fossil record” that is imprinted in the gas rich atmospheres of early type galaxies, groups, and clusters by powerful SMBH outbursts. We will discuss the outburst history of M87 as chronicled in its radio and X-ray images and the implications of these outbursts for heating gas-rich environments. Based on a simple shock model of M87’s 12 Myr old outburst, we will present the properties of the outburst including its age, total energy, and duration. We conclude by describing a future X-ray mission, Lynx, whose sub-arcsecond angular resolution would allow us to study the evolution of SMBHs and hot, X-ray emitting atmospheres from high redshifts to the present.
IGR J16318-4848 : optical and near-infrared spectroscopy of the most absorbed B[e] supergiant X-ray binary with VLT/X-Shooter
Fortin, Francis
The supergiant High Mass X-ray Binary IGR J16318-4848 was detected by INTEGRAL back in 2003 and distinguishes itself by its high intrinsic absorption and B[e] phenomenon. It is the perfect candidate to study both binary interaction and the environment of supergiant B[e] stars. We report on VLT/X-Shooter observations from July 2012 in both optical and near-infrared, which provides unprecedented wide-range, well-resolved spectra of IGR J16318-4848 from 0.5 to 2.5µm. Adding VLT/VISIR and Herschel data, the spectral energy distribution fitting allows us to further constrain the contribution of each emission region (central star, irradiated rim, dusty shell). We derive geometrical parameters using the numerous emitting and absorbing elements in each different sites in the binary. Various line shapes are detected, such as P-Cygni profiles and flat-topped lines, which are the signature of outflowing material. Preliminary results confirm the edge-on line of sight and the equatorial configuration of expanding material, along with the detection of a potentially very collimated polar outflow. These are evidences that the extreme environment of IGR J16318-4848 is ideal to get a better grasp of highly obscured High Mass X-ray Binaries.
Spectroscopic identification of INTEGRAL high-energy sources using VLT/ISAAC
Fortin, Francis
INTEGRAL has been observing the gamma-ray sky for 15 years and discovered over 900 high-energy sources of various nature (Bird et. al 2016). They are mostly AGNs (369) and X-ray binaries (348). However, more than 200 of them still lack a precise identification. We thus aim to better constrain their nature in order to improve the census on binaries, which could then be compared with population synthesis models. We performed near-infrared photometry and spectroscopy with VLT/ISAAC in July 2012 on 15 INTEGRAL sources, and identified them by comparing their spectral features to nIR atlases. In particular, deriving the spectral type of donor stars allowed us to constrain the exact nature of several binaries. Our sample is mostly composed of AGNs (5) and Cataclysmic Variables (5), along with X-ray binaries (2 BeHMXB and 2 LMXB). Especially, some of the CVs we found appear to have a companion star which may have depleted its atmosphere. These results are the first step to further studies which will focus on deriving various parameters in binaries using spectral modelisation.
Spinning galaxies into shape
Foster, Caroline
Combining kinematic maps and imaging data for a generous sample of galaxies from the Sydney-AAO Multi Integral field (SAMI) Galaxy Survey, I empirically measure the relationship between the intrinsic (3D) shape of galaxies and spin. Most galaxies are oblate axisymmetric with varying degrees of intrinsic flattening. Low spin systems have a higher occurrence of triaxiality and high spin systems are more intrinsically flattened and axisymmetric._x005F I argue that angular momentum plays a fundamental and primary role in shaping galaxies. Based on outer balance in dynamical support, I further suggest that at fixed spin, the visual morphology (e.g. presence of spiral arms) is likely set by other processes such as gas content and merger history.
Central Stars of Planetary Nebulae in Galactic Open Clusters: Providing additional data for the White Dwarf Initial-to-Final-Mass Relation
Fragkou, Vasiliki
The accurate (<10%) distances of Galactic star clusters, as defined from color-magnitude diagrams, allow precise determination of the physical parameters of any physically associated Planetary Nebula (PN) and also that of its central star (CSPN). Theoretical cluster isochrones can be used for the determination of the PN progenitor's mass and age, while photometry of its CSPN strongly constrains its intrinsic luminosity and mass given the known distance. The mass of the progenitor star can be related to the PN's chemical characteristics, determined from spectroscopic measurements and furthermore, provides additional data for the widely used white dwarf (WD) initial-to-final mass relation (IFMR). The IFMR is crucial for tracing the development of both carbon and nitrogen in entire galaxies. To date there is only one PN (PHR1315- 6555) confirmed to be physically associated with a Galactic Open Cluster (ESO 96 -SC04). This cluster has a turn-off mass ? 2.2 M?. Our deep HST photometry was used for the search of the CSPN of this unique PN and in this work, we present our results.
Ionized gas metallicity in galaxies from the GASP survey
Franchetto, Andrea
This work is performed in the context of GAs Stripping Phenomena in galaxies with MUSE (GASP) survey. The high-quality spectroscopic data provided by MUSE allow a spatially-resolved study of the ionized gas chemical abundance. This work aims to compare the gas-phase metallicity properties of 10 disk galaxies with no morphological anomalies and 12 gas-stripped galaxies with evident signs of unilateral debris and gas tails. The chemical abundance of the ionized gas is estimated analyzing the emission line fluxes in star-forming regions using the theoretical calibrator pyqz based on photoionization models.The analysis of the metallicity distribution derived in this work confirms that the normal galaxies are characterized by a clear negative gradient. Moreover, the gas-stripped galaxies also exhibit a negative metallicity gradient in the main galaxy body, though it is flatter, that continues in the gas tails. This suggests that the gas-removal process in these galaxies, mainly the ram-pressure stripping, eradicates the gas proceeding outside-in.This work focuses also on the dependence of the metallicity on the global and local properties of galaxies, finding that the local chemical abundance of normal galaxies presents a clear correlation with the stellar mass density, while in gas-stripped galaxies there is a mismatch between these quantities.The results in this work allow to improve the knowledge of the ram-pressure mechanism demonstrating that the gas-phase metallicity can trace the gas-stripping history.
Icy-Grain Aggregation at the Earliest Stages of Planet Formation
Fraser, Helen Jane
Water is incorporated into protoplanetary disks in the form of icy interstellar grains, dominated by amorphous water ice. Ice provides most of the mass available for planet formation beyond the snowline, and the eventual water content of terrestrial-type planets depends upon this reservoir. The first stage of terrestrial planet formation is the accumulation of icy nm to mm-sized interstellar grains into mm-grains, held together by van der Waals forces; dm to m scale ‘pebbles’ then clump together through streaming instabilities and form gravitationally-bound ‘pebble clouds’. However, the collisional properties of icy aggregates in the mm – dm range are currently entirely unknown; hypo-velocity collisions between icy grains under these conditions are thought to be key to building up a critical mass of icy ‘pebbles’; the ice structure, phase and surface properties may also be relevant.We have studied the outcomes of low-velocity binary collisions between dust or icy grains in parabolic-flight experiments, showing that dust fragments more easily when 'cold', that mm to cm-sized icy grains bounce rather than stick in hypo-velocity collisions, and chemical impurities cannot aide ice sticking. We have exploited the ISIS neutron scattering source to understand the molecular- and mesoscale- structure of interstellar water ice. Our findings demonstrate why there are such a variety of collisional outcomes in laboratory experiments on "ice grain sticking". In conditions far from those found in protoplanetary disks, surface wetting and structure dominate the collisional outcomes. Conversely, under low density and temperature conditions the icy particle surfaces remain intact. By looking at sublimation and outgassing of the icy grains we are building a picture of the complex interplay of icy grains and the gas and dust, right at the "snow zone" where the critical onset of planet formation occurs.
Ice Mapping in the JWST Era: Unveiling the Frozen Unvierse
Fraser, Helen Jane
Our cycle 1 JWST proposal builds on our AKARI ice-mapping programme, which showed the distribution of H2O CO and CO2 ices in 12 pre-stellar cores. After H2 gas, interstellar ices constitute the largest molecular reservoir in star-forming regions. By observing interstellar ices we probe the synergy between the gas-phase and the solid-state, scrutinising the feedback mechanisms that dominate physical and chemical processes during star- and planet-formation.JWST offers unprecedented spectral resolution and sensitivity to observe interstellar ices, through their NIR and MIR absorption features, which correspond to the stretching and bending modes of the functional groups of the ice molecules. The band-profiles reflect both the formation and evolutionary history of the ices. Our JWST observations will follow up on six key outcomes from our AKARI ice-mapping programme;the development of unique techniques to extract ice abundances from slit-less spectroscopy observations, being extended to NIRCAM and NIRSPEC MSA observations,ice column densities not following the “more is more” adage across 100 – 1000 AU scales in extincted regions of pre-stellar cores – JWST will test this from cloud edges to heavily extinct regions,ices have been detected on lines of sight outside molecular clouds – an observation for which there is not yet any explanation,extending ice spectroscopy from the NIR to MIR region, allowing additional chemical information to be obtained by concurrently observing bending and stretching modes of ice features,detecting “secondary” ice species such as CH3OH and NH3 for which some evidence exists in the AKARI spectra; similarly follow-up of the upper-limit detections of HDO and 13-C species,resolving ice spectral features such that direct comparisons to laboratory spectra can be made, and comparison with gas and dust observations can enhance our understanding of the chemical history of a region.
On cylindrically symmetric solutions of polarized radiative transfer equation
Freimanis, Juris
While modelling astronomical objects in general, and envelopes of AGB stars in particular, only numerical solutions of radiative transfer equation (RTE) can give realistic pictures of real objects. However, analytic solutions of RTE (and other equations of mathematical hysics) for simplified, symmetric model cases are desirable as tests of correctness and precision of computer programs. Besides, sometimes astronomical objects can be looked upon as approximately having some particular symmetry, and analytic solution of RTE can be used for evaluation purposes.Continuum radiation from dust envelopes of AGB and post-AGB stars is often polarized due to form and morphology of the envelope, orientation of dust grains and asymmetry of the primary sources of radiation. Polarization gives valuable astrophysical information, and solution of RTE without accounting for polarization is basically incorrect.Some exact model solutions of monochromatic polarized RTE in homogeneous isotropic mirror-symmetric medium, in case if the radiation field has cylindrical symmetry, are reviewed in this report. Cylindrically symmetric Green's function for infinite medium is mentioned, stressing its complexity. Cylindrically symmetric inner eigenfunctions of RTE are presented as much simpler alternative, which can be used if the scattering medium (e.g. dust cloud) is a homogeneous cylinder of infinite length but finite radius, and the medium is irradiated from outside. It is proven that cylindrically symmetric homogeneous polarized RTE has solutions (eigenfunctions) indexed by asymptotic azimuthal index (AAI) adopting arbitrary integer values. There are at least one convergent inner eigenfunction and one divergent formal outer eigenfunction for each value of AAI; clear analytic expressions are given for them. If the modulus of AAI does not exceed 3 then these are the only eigenfunctions of cylindrically symmetric RTE.
SEARCHING FOR MID-INFRARED EXCESS IN EVOLVED STARS
Freire da Silva, Danielly
Debris discs are commonly detected orbiting main-sequence stars, but little is known regarding their fate as stars evolve along the subgiant and giant stages. Nevertheless, the literature reports a few studies show strong evidence on the presence of mid-IR excess in G and K stars of luminosity class III, using photometric data from the Two-Micron All-Sky Survey (2MASS) and GLIMPSE catalogues and, more recently from WISE space borne. While the origin of these excesses remains uncertain, it is plausible that they arise from debris discs around these stars. The present study brings an unprecedented survey in the search for mid-IR excess among single and binary F, G and K-type evolved stars of luminosity classes IV, III, II and Ib. For this study, we use WISE and 2MASS photometric data for a sample of 3000 evolved stars, complete up to visual magnitude of 6.5. As major results, we found that the frequency of evolved stars showing mid-IR WISE excess increases from the luminosity classes IV and III to luminosity classes II and Ib. In addition, there is no clear difference between the presence of IR excess in binary and single stars for all the analyzed luminosity classes.
Revealing the true nature of radio AGN above redshift 4 that mimic blazars
Frey, Sándor
Previous high-resolution observations with the European Very Long Baseline Interferometry Network (EVN) uncovered three blazar candidates at redshifts z>4 that show radio structures completely unexpected for active galactic nuclei (AGN) with relativistically beamed jets closely aligned to our line of sight. These sources were selected based on their broad-band spectral energy distribution (SED) typical for blazars. All of them turned out to have significant radio emission resolved out with the EVN on ~1-10 milliarcsecond scales, while they show multiple components on ~5-10 arcsec scales. Here we present new images made with the electronic Multi-Element Remotely Linked Interferometer Network (e-MERLIN) at 1.6 and 5 GHz frequencies to constrain the geometrical and physical properties of these puzzling objects. These observations could countribute to the understanding of the apparent deficit of known misaligned radio AGN at very high redshifts.
High-resolution radio detection of the gamma-ray blazar candidate J1331+2932
Frey, Sándor
When looking for evidence for gamma-ray flaring activity in the stellar binary system DG CVn, recently Loh et al. (2017) found a transient source using Fermi Large Area Telescope data. However, since simultaneous flaring of DG CVn was not reported at any other waveband that time, the background quasar J1331+2932 fell under suspicion as the possible source of the gamma-rays. Among the gamma-ray emitting extragalactic sources, blazars constitute the most populous group. Milliarcsecond-resolution radio interferometric observations are the best suited for providing the ultimate evidence to discriminate between a blazar and non-blazar radio-emitting active galactic nucleus. We observed J1331+2932 with the European Very Long Baseline Interferometry Network at 5 GHz. We discuss our findings here.
Using proper motions to constrain the origin of galaxies
Fritz, Tobias
Due to their proximity, the globular clusters and dwarf galaxiessatellites of the Milky Way can be observed in great detail from theirresolved stars. Proper motions can provide crucial information on theorigin of several of these systems. In this talk we present results usingground based images and Gaia DR2 data to measure the proper motion ofglobular clusters and dwarf galaxies in the halo of the Milky Way. Due toits orbit and metallicity, we find that the Pyxis globular cluster did notform in-situ, but it was likely accreted from an unknown, likely destroyeddwarf galaxy more luminous than M_V=-10. Furthermore, we find that theultra faint Segue 1 was not a satellite of known dwarf galaxies moreluminous than M_V=-8.8 and therefore likely formed on its own without being"a satellite of a satellite". In case of Gaia DR2 data, we concentrate onthe recent discovered ultra-faint galaxies to explore their possibleassociated to the Magellanic clouds and use them to make inferences ontotal mass of the Magellanic clouds.
HI Gas component in dwarf galaxies in the view of semi-analytic models
Fu, Jian
In this talk, we will show our recent progress on semi-analytic models of galaxy formation, which mainly focus the HI gas component in low mass galaxies. Our models based on the SAMs codes L-Galaxies and run on the Aquarius haloes and ELUCID halos to study the local dwarf galaxies, and we use the presciprtions related to interstellar surface densities, metallicities and UV back ground field to calculated the HI gas components in ISM. We show that:(1) Our models can fit the HI mass function from ALFALFA to very low mass end, and the low mass end of HIMF is very sensitive to the physical processes in low mass satellites, e.g SN feedback, ram pressure stripping.(2) Our models predict a lot of gas rich low mass dark galaxies, which may offer opportunities for future HI 21cm survey in neary by galaxies by FAST and SKA-1.(3) The tight correlation between HI disk size and HI mass can be extended to very low mass range (MHI~107Msun), we find that is mainly caused by the transition between atomic gas and molecular gas.(4) The minor mergers processes between HI rich satellites and central galaxies contribute a large fraction of HI source in gas accretion.
Detection of unknown objects in Bayer’s Uranometria
Fujiwara, Tomoko
The development of observational instruments provides us the benefit of understanding astronomical phenomena. However even with the most advanced technologies, it is impossible to know transient phenomena that have already passed or celestial objects that have quite long-term variability. Surviving historical archives are important observational data that tell us situations of each star of their times. The goal of this study is to find unknown objects recorded in historical records and to understand transient phenomena. It would be possible to discover supernovae, novae or long-term variable stars, etc.Uranometria (the full title: Uranometria: omnium asterismorum continens schemata, nova methodo delineata, aereis laminis expressa) is an astronomical document composed of a star catalogue and star charts. It is compiled by Johanne Bayer (1572-1625) and published in Augsburg in 1603. In his catalogue, 1169 stars of 60 constellations (Ptolemy's original 48 and 12 of the southern sky) are listed by each constellation in order of magnitude (1-6), and with its designation known as a Bayer’s name. Uranometria contains 51 star charts; 48 figures of Ptolematic constellations and one displayed 12 new southern constellations. The last 2 charts are northern and southern hemispheres. On these charts, more than 1500 stars are drawn in ecliptic coordinates (ep=1600).Using observational results by Hipparcos, we compared these detected coordinates with modern star catalogues and identified objects recorded in Uranometria. Even after taking into consideration of the systematic error, we found some of them could be unknown objects. In this paper, we present Bayer’s Uranometria and unknown stars, and discuss characteristics of these objects.
Seasonal variation of radial brightness contrast of Saturn's rings viewed in mid-infrared by Subaru/COMICS
Fujiwara, Hideaki
To investigate the mid-infrared (MIR) characteristics of Saturn’s rings, we collected and analyzed MIR high spatial resolution images of Saturn’s rings obtained in January 2008 and April 2005 with COMICS mounted on Subaru Telescope, and investigated the spatial variation in the surface brightness of the rings in multiple bands in the MIR. We also composed the spectral energy distributions (SEDs) of the C, B, and A rings and the Cassini Division, and estimated the temperatures of the rings from the SEDs assuming the optical depths. We find that the C ring and the Cassini Division were warmer than the B and A rings in 2008, which could be accounted for by their lower albedos, lower optical depths, and smaller self-shadowing effect. We also find that the the C ring and the Cassini Division were considerably brighter than the B and A rings in the MIR in 2008 and the radial contrast of the ring brightness is the inverse of that in 2005, which is interpreted as a result of a seasonal effect with changing elevations of the sun and observer above the ring plane.
Numerical computation of gravitational field of infinitely-thin axisymmetric disc with arbitrary surface mass density profile and its application to preliminary study of rotation curve of M33
Fukushima, Toshio
We developed a numerical method to compute the gravitational field of an infinitely-thin axisymmetric disc with an arbitrary surface mass density profile (Fukushima 2016, MNRAS, 456:3702). We evaluate the gravitational potential by a split quadrature using the double exponential rule and obtain the acceleration vector by numerically differentiating the potential by Ridders' algorithm. The new method is of around 12 digit accuracy and sufficiently fast because requiring only one-dimensional integration. By using the new method, we show the rotation curves of some non-trivial discs: (i) truncated power-law discs, (ii) discs with a non-negligible center hole, (iii) truncated Mestel discs with edge-softening, (iv) double power-law discs, (v) exponentially-damped power-law discs, and (vi) an exponential disc with a sinusoidal modulation of the density profile. Also, we present a couple of model fittings to the observed rotation curve of M33: (i) the standard deconvolution by assuming a spherical distributin of the dark matter and (ii) a direct fit of infinitely-thin disc mass with a double power-law distribution of the surface mass density. Although the number of free parameters is a little larger, the latter model provides a significantly better fit. The Fortran 90 program package of the new method named "xvrot.txt" is freely available from the author's web site: https://www.researchgate.net/profile/Toshio_Fukushima
Precise and fast computation of gravitational field of general finite body and its application to gravitational study of asteroid Eros
Fukushima, Toshio
In order to obtain the gravitational field of a general finite body like Ryugu inside its Brillouin sphere, we developed a new method to compute the field accurately (Fukushima 2017, Astron. J., 154:145). First, the body is assumed to consist of some layers in a certain spherical polar coordinate system and the volume mass density of each layer is expanded as a Maclaurin series of the radial coordinate. Second, the line integral with respect to the radial coordinate is analytically evaluated in a closed form. Third, the resulting surface integrals are numerically integrated by the split quadrature method using the double exponential rule. Finally, the associated gravitational acceleration vector is obtained by numerically differentiating the numerically integrated potential. Numerical experiments confirmed that the new method is capable of computing the gravitational field independently of the location of the evaluation point, namely whether inside, on the surface of, or outside the body. Also, it can provide sufficiently precise field values, say of 14--15 digits for the potential and of 9--10 digits for the acceleration, respectively. Furthermore, its computational efficiency is better than that of the polyhedron approximation. This is because the computational error of the new method decreases much faster than that of the polyhedron models when the number of required transcendental function calls increases. As an application, we obtained the gravitational field of 433 Eros from its shape model expressed as the 24x24 spherical harmonic expansion by assuming the homogeneity of the object.
Episodes of Ionospheric Disturbances caused by Solar Activity Probed using km-wave Terrestrial Radio Signals
G A, Shanmugha Sundaram
A disturbed condition in the Earth's ionosphere region involved with propagation of terrestrial VLF radio signals (kilometric wavelengths) had registered its characteristic signatures in the dynamic spectral records obtained during 16 April 2015. The reason for such features in the spectrogram data can be attributed to the impact of solar energetic particles (SEP) on the outer layers of the ionosphere that coincide with the propagation paths of terrestrial long wave radiation. These were studied using the multi-hop propagation model. Points of_x005F reflection in the ionosphere directly above specific locations above the Earth where thereby determined. Total electron content (TEC) values for such regions were obtained from interpretation of the global positioning system (GPS) data at these locations. From a comparisons of such results during periods when the Sun was quiescent and active, the magnitude of ionosphere disturbance contributed by one of several types of active solar events has been determined. The work reported here is based on the impact of a large-scale geomagnetic storm (Kp=6) on the TEC. VLF radio signals from transmitter locations operated by the United States Navy near Lualualei, Hawaii (geomagnetic latitude 21o 25' 13.38" N, geomagnetic longitude 158o 9' 14.35" W) and by France at Rosnay (geomagnetic latitude 46o 42' 47" N, geomagnetic longitude 1o 14' 39" E) were monitored closely to understand the extent of this ionospheric impact.
The COSPAR Capacity Building Programme – Today and Tomorrow
Gabriel, Carlos
The COSPAR Capacity Building Programme (CBP) started in 2001 with the organisation of highly practical workshops in developing countries with the aim of encouraging (young) scientists from those regions to use scientific data from space missions. In 2009 a Fellowship associated to the workshops has been added as a fundamental component of the CBP. The Programme today is covering a large number of disciplines related to space sciences, with a cadence of 3 workshops per year. The three workshops taking place this year are in the fields of infrared and sub-mm astronomy, solar physics and space weather, showing how wide is the scope of the CBP. A key in the success of the CBP is the strong engagement in it of internationally high ranked scientists as well as of the space agencies ESA, NASA and JAXA.A reorganisation of the Panel takes place in 2018 during the COSPAR GA in April, surely an opportunity to improve the activities, especially in the way of evaluating the impact the Programme is having in development countries. Ideas and on-going initiatives hereabout will be exposed and discussed.
Hen 3-160 - the first symbiotic binary with Mira variable S star?
Galan, Cezary
Hen 3-160 is reported in Belczynski et al.’s (2000) catalogue as symbiotic binary system with M7 giant donor. Using V and I-band photometry collected over 14 years we have found from that the giant is a Mira variable pulsating with 242.5-day period. The period-luminosity relation locates Hen 3-160 at the distance of about 9.5 kpc, and its Galactic coordinates (l=267.7, b=-7.9) place it ~1300 pc above the disc. This position combined with relatively high proper motions (pmRA=-1.5 mas/yr, pmDEC=+2.9 mas/yr; Gaia DR2) indicates that Hen 3-160 has to be a Galactic halo object. Our red optical and infrared spectra show the presence of ZrO and YO molecular bands that appear relatively strong compared to the TiO bands. Here we propose that the giant in this system is intrinsic S star, enriched in products of slow neutron capture processes occurring in its interior during AGB phase which would make Hen 3-160 the first symbiotic star with Mira variable S star.
A binary system through the planetary region: the journey of Typhon-Echidna
Galiazzo, Mattia
Only 2 trans-Neptunian binaries (TNBs) are known as Neptune-crosser bodies: (42355) Typhon-Echidna and (65489) Ceto-Phorcys. We present here the temporal evolution of theTyphon-Echidna binary system through the outer and inner planetary systems. Using numer-ical integrations of the N-body gravitational problem, we explore the orbital evolutions of 500 clones of Typhon, recording the close encounters of those clones with planets. We analyse the effects of those encounters on the binary system. As results, we find that only ˜ 22% of the encounters with the giant planets were strong enough to disrupt the binary. This binary system has an ˜ 3.6% probability of reaching the terrestrial planetary region over a time scale of approximately 5.4 Myr. Close encounters of Typhon-Echidna with Earth and Venus also happen, however with a low probability (˜ 0.4%). The past orbital evolution of the system in the last 100 Myr shows that Typhon might have spent most of its time as a TNB crossing the orbit of Neptune. Finally, as main result, our study of the Typhon-Echidna orbital evolution illustrates the possibility that large binary cometary bodies (larger than about 40 km) coming from a remote region of the outer Solar System might enter the terrestrial planetary region preserving their binaritythroughout the journey.
A census of low mass stars in different associations at different ages states.
Galindo Guil, Francisco Jose
We have study the study 12 young open clusters.Membership is determined using a multi-wavelength photometric and proper motions approach, obtained data from public surveys and archival data: $B_T V_T$ and proper motions from Tycho-2,proper motions from TGAS and HSOY, $griz$ from SDSS, $JHK_s$ from 2MASS, $W_1W_2W_3W_4$ from WISE, $gri$ from INT-WFC, $iz$ from CFHT-12K, from $UBV$ KPNO-MOSAIC and $J$ from KPNO-NEWFIRM.In addition, we have followed-up some memberships using spectroscopy data with CAHA-TWIN, GTC-OSIRIS and archival data from SDSS.It is the first time, for these clusters that IMF is studied so deep and using Gaia distances
Dense molecular gas in dwarf galaxies: views from the outer disks and M33
Gao, Yu
The dense molecular gas mass, traced by HCN J = 1-0, linearly correlates with the far-infrared (FIR) luminosity (~ star formation rate, SFR) for essential all star-forming systems near and far. The spatially resolved FIR-HCN correlation in the spiral disks of galaxies, a local star formation law in terms of dense molecular gas across the disks, is also established, to be essentially same as that established from the Galactic cloud cores and that of global galaxies. Such tight linear SFR - dense molecular gas correlations suggest that the SFR depends linearly uponthe mass of dense molecular gas. This is drastically different from the traditionally established Kennicutt-Schmidt (K-S) laws that relate the total gas and SFR in galaxies as there are no unique correlations in these K-S laws. Will this FIR-HCN correlation be still valid and applicable in dwarf galaxies? The difficulty in detecting CO in dwarf galaxies with ALMA already implies that it is almost impractical in detecting the HCN emission in more a few dwarf galaxies. Nevertheless, HCN observations in M33 and the outer disks of star-forming galaxies, e.g., M51, indeed show that the dwarf galaxies should follow the same linear FIR-HCN correlation over 10 order-of-magnitude. Finally, we also report the progress of our efforts in ALMA observations of dense gas in a nearby dwarf galaxy.
Analysis of KOI 2700b: the second exoplanet with a comet-like dusty tail
Garai, Zoltán
Close-in exoplanets are subjected to the greatest star-planet interactions. This interaction may have various forms. In certain cases it may cause formation of a comet-like dusty tail. The Kepler object KOI 2700b was discovered recently as the second exoplanet with such a comet-like tail. It exhibits a distinctly asymmetric transit profile, likely indicative of the emission of dusty effluents and reminiscent of KIC 12557548b, the first exoplanet with a comet-like dusty tail. Our scientific goal is to verify the disintegrating-planet scenario of KOI 2700b by modeling its light curve and to put constraints on various tail and planet properties, as was done in the case of KIC 12557548b. We would like to understand better how the disintegration works at this uninhabitable planet, especially what is the typical particle size in the dusty tail, how big is the planet solid body and how fast is the mass loss from the planet. We obtained the phase-folded and binned transit light curve of KOI 2700b, which we subsequently iteratively modeled using the radiative-transfer code SHELLSPEC. We modeled the comet-like tail as part of a ring around the parent star and we also included the solid body of the planet in the model. During the modeling we applied selected species and dust particle sizes. We also analyzed the systematic evolution of the light curve and searched for possible long-term orbital period changes of KOI 2700b. We confirmed the disintegrating-planet scenario of KOI 2700b. Furthermore, via modeling, we derived some interesting features of KOI 2700b and its comet-like tail.
Dwarf Irregular Galaxies and Massive stars: the beginning of a beautiful friendship
Garcia, Miriam
The comunity of massive stars is thrilled about Local Group dwarf irregular galaxies (dIrr). They are a wealthy reservoir of metal-poor massive stars that provide us with unique insight on their medium-to-high redshift relatives, allowing us to assess feedback through cosmic history and to interpret the farthest, most energetic SNe and GRBs. Along the way, we are becoming interested in the recent star-formation history and initial mass-function of the host dIrr's, their chemical evolution, their gas and dust content, and the interplay with hot massive stars. This poster is a showcase of some results on the galaxies that are attracting most of our attention, to stimulate interaction and future collaborations/sinergies between both communities.
Prospecting the wind properties of IGR J16320-4751 with XMM-Newton and Swift
García, Federico
We present the results of a detailed study of the spectral evolution of the obscured NS-HMXB IGR J16320-4751 based on an orbital monitoring performed by XMM-Newton and Swift/BAT. By means of the hard X-ray data from Swift/BAT we re-calculated the ephemeris of the source, updating its reported orbital period. Based on the temporal evolution of the source revealed by the light-curves of each observation performed by XMM-Newton, we generated time-resolved spectra that we fitted using an absorbed comptonization and gaussian Fe Ka, XXV and Kß emission lines. We found that the spectral evolution is mainly governed by variations in the absorption column density, associated to the position of the NS along its orbit. Finally, assuming a typical wind profile for the supergiant star we simultaneously model the evolution of the hard X-ray light curve and the observed absorption column to constrain the eccentricity and inclination of the binary system, helping to better understand the behavior of these obscured sources.
Sciences and audiences along the last century: the impact of Astronomy Education
García, Beatriz
Just as in the past the development of the natural sciences and in particular of astronomy changed the history of humanity, if we think about the role of our discipline towards the future, it shows its enormous power in the field of education, due to the possibility of awakening interest in very varied audiences and, within the framework of the enormous progress made in the technologies related to astronomy, many of them of daily use, the role of the astronomer in the framework of the era of Communications acquires fundamental importance In this presentation, we will try to make a journey through the different ways of presenting the astronomical topics for different audiences over the last 100 years, but, in turn, we will show some specific achievements, associated with education programs of the discipline. and the impact produced by proposals that are at the same time rigorous in terms of content, but that also appeal to the development of the human being in an integral manner, within the framework of citizen science activities. For this research, we have taken into account the uninterrupted development of the NASE program, which has performed 104 courses in 23 countries on all the Globe in different languages, and has involved 4966 secondary teachers in the last 8 years.
NASE and the Cultural Astronomy: the rescue of the "every day" Astronomy
García, Beatriz
Astronomy is a discipline that involves several areas of knowledge, Physics, Chemistry Mathematics and, ultimately, Biology, seem to be the most important. However, from the past of the human being this discipline has developed as a cultural manifestation and is part of the collective unconscious. Therefore, it is one of the sciences to which people approach more easily, without taking into account the exact or natural sciences that sustain their concepts._x005F Astronomy is present in everyday life, we measure time, observe the phases of the Moon, orient buildings to take advantage of sunlight or improve heat exchange with the environment, we refer to Universal Time, the zero meridian or the equinox. Astronomy is part of the culture and as such, should be rescued. NASE explores the potential of cultural astronomy in the middle level classes through the training of teachers who become mediators between scientists and students._x005F In this presentation we present the achievements of the inclusion of topics of Cultural Astronomy, Astronomy in the City or Arqueoastronomy in the NASE courses from the rescue of the records of native peoples or present in the cities where the workshops have been given, after almost a decade of continuous development of the Program in 23 countries around the world.
The Pierre Auger Observatory: impact of the interactive approach to communicate the Science with the public
García, Beatriz
The Pierre Auger Observatory is the biggest facility in the world devoted to the detection and study of ultra high energy cosmic rays. Ever since its start, at the end of XX century, the Observatory was focussed not only to work at the frontiers of the scientific knowledge but also to serve as a reference on education and outreach. Within the frame-work of the Design Thinking, a proposal from Stanford University in the 1970s, the tools of the trans-media storytelling or multi-platform storytelling and the available applications, including enhanced reality, are used in the redesign of the Visitor Center of the Observatory in Malargue, Argentina. In this presentation, we will show how to attract visitors to the new Visitor Center and analyze the impact of this interactive new approach to communicate the Science with the public._x005F Note: This presentation is on behalf of Pierre Auger Collaboration
NOC activities at Argentina
García, Beatriz
The poster present the NOC activities at Argentina
Design Thinking in Astronomy Education: a case study
García, Beatriz
In general terms, Design Thinking (DT) is a methodology inspired by the design process that was born at Stanford University in the 70s of the 20th century._x005F Essentially aims to solve the needs of people, using technologically possible tools, without losing sight of innovation. For this, 5 basic steps can be defined, applicable to almost all human activities in which innovation is centered on the person: empathize, define, devise, prototype and evaluate._x005F The DS allows finding solutions to learning problems, proposing simple and low cost activities, adapted to students. In certain aspects, it is based on the redesign of the student's educational experience, based on their qualities, interests, experiences, feelings. Each school, each course, each student has singularities and this type of approach to teaching takes them into account. Each step is adapted to the needs and times of the students, who change continuously._x005F The DT Methodology was applied in Argentina at the Physics and Astronomy space of a last year of secondary school, with students between 16 and 18 years old._x005F From the main themes that emerged from the initial dynamics in the year, based on the development of 2 techniques: brainstorming and mood board, such use exotic objects: black holes, stars of neutrons, stars in general, exoplanets or planets, and questions like how the Universe evolves? what is the Big Bang? ) the steps followed were guided by the premisses: imagine, build, share, evolve, to reach a final product to be exhibited and presented to all the school community._x005F This presentation shows the results of the application of this methodology and the final products, consisting of posters and modules with augmented reality, for which new software and different applications for cell phones were used.
The journey of organic matter during stellar evolution: a laboratory approach
Gavilan, Lisseth
The evolution of organic matter begins from its formation in the interstellar medium until its incorporation in planetary systems. During their life cycle, organics are continuously impacted by energetic sources like stellar photons, electrons, particles and cosmic rays. Ionizing radiation can impact the molecular properties of organics but also their optical and molecular properties. Our goal is to quantify these changes via laboratory simulation experiments compared to astronomical observations.We present the first results of this study using the COsmic SImulation Chamber (COSmIC) experimental facility at NASA Ames dedicated to the study of neutral and ionized molecules and nanoparticles under the low temperature and high vacuum conditions that are required to simulate various space environments such as diffuse interstellar clouds, circumstellar outflows and planetary atmospheres. The COSmIC experimental setup is composed of a Pulsed Discharge Nozzle (PDN) expansion, that generates a plasma in the stream of a jet-cooled supersonic expansion (50-150 K), coupled to two high-sensitivity-, complementary in situ diagnostics: a cavity ring down spectroscopy (CRDS) and laser induced fluorescence (LIF) systems for photonic detection, and a Reflectron Time-Of-Flight Mass Spectrometer (ReTOF-MS) for mass detection in real time. We use this setup to synthesize analogs of interstellar organic dust and to characterize the molecular component in situ. We also characterize the solid carbonaceous particles ex-situ via spectral and solid-state diagnostics. By comparing these to observed dust spectra, we expect to shine light on their journey alongside stellar evolution.
Interactive Planetarium Presentations that Support a Personal Understanding of the Cosmos
Gelderman, Richard
Hardin Planetarium is one of the many science museums around the globe that provide an important forum for supporting informal educational opportunities for those who otherwise have turned away from science. We collaborate with international partners interested in live, interactive presentations that are explicitly designed to actively engage people who don’t otherwise connect with science education opportunities. People never recognized as academic achievers are typically the ones most appreciative of highly interactive presentations. Examples of our most successful initiatives include planetarium shows founded on audience participation. Our Star Stories version of the seasonal night sky tour never mentions the “accepted” constellation names from any culture, but instead has them connect the stars into patterns from their imagination. Groups of audience members share the story they come up with about the pattern they see in the stars, and the planetarium leader weaves each story into a uniquely original star-hopping connection of that evening’s sky. Audience members in our Lives of the Stars show choose any star in the evening sky, whereupon the planetarium leader shares some particular information about that object and how it ties into broader astrophysical explanations of cycles of stellar evolution in our Galactic neighborhood.
GALAXY ANGULAR MOMENTUM ESTIMATION WITH All CONVOLUTIONAL NEURAL NETWORKS
Genel, Shy
We present a convolutional neural network design that is trained to measure the specific angular momentum of galaxies from the IllustrisTNG cosmological hydrodynamical simulation. We generate intensity and kinematics maps from the stellar component as well as the star-forming gas of tens of thousands of galaxies with stellar masses 10^9-10^12 solar masses at a variety of redshifts. A fraction of these images are fed into the neural network as a training set, and a fraction is used to then measure its performance, for various image generation parameters such as pixel size. We find that this method is able to measure the specific angular momentum of the simulated galaxies to a degree that is competitive with existing methods, opening the door for possible accurate measurements of real galaxies.
The environmental dependence of the subsolar initial mass function
Gennaro, Mario
Understanding whether the Initial Mass Function (IMF) varies with environment will advance our detailed understanding of star formation and provide an empirical foundation for interpreting the observations of star-forming galaxies throughout cosmic history.In particular, very low-metallicity systems, like Local Group ultra-faint dwarfs, provide clues towards understanding the conditions in which stars formed in the early Universe, before the epoch of re-ionization.I will present recent results from both optical and near-infrared HST observations that probe the stellar populations of 6 nearby ultra-faint Milky Way dwarf satellites down to 0.4 (optical, using ACS) and 0.2 (near-IR, using WFC3) solar masses. Our analysis suggests that the IMF slope of such objects is flatter than that in the Milky Way. We observe a correlation between the IMF slope and the metallcitiy of the galaxies, with the most metal-poor ones having a more bottom-light IMF, i.e., fewer low-mass stars, relative to the Milky Way. Moreover, there is large variance in the IMF shape among the 6 galaxies observed in the optical.Obtaining measurements reaching well below the Milky Way IMF turnover mass of 0.5 Msun is very costly with HST, and feasible only for the closest UFDs.Near-future missions like JWST and WFIRST will help us probe an even smaller mass regime, reaching close to the hydrogen burning limit.
The seed factor: a way to understand the blazar GeV emission
Georganopoulos, Markos
The question of if the blazar GeV emission comes from leptonic or hadronic processes is still unclear. For leptonic models the distance of the GeV emission site is still debated. We present a way to approach these issues and we show some preliminary results.
Revealing a gap in the protoplanetary disk of DI Cha A with mid-infrared interferometry
Gerják, Tímea
DI Cha A is the brightest component of a quadruple stellar system in the Chamaeleon star forming region. It is a G2-type T Tauri star at a distance of 200 pc, possessing a circumstellar disk.We studied the structure of the disk using archival high spatial resolution mid-infrared interferometric observations obtained with the VLTI/MIDI instrument, and also multi-wavelength photometric data. We applied radiative transfer modeling with the RADMC-3D software package using a two-component model, which contains a halo and a disk component. We found that the inner radius of the mid-infrared emitting disk is 1.5 au, far larger than the dust sublimation radius, indicating the presence of a gap. For the halo the best fitting outer radius is 0.4 au.From this we conclude that the disk of DI Cha A can be classified as a (pre-)transitional disk, possibly indicating ongoing planet formation within.
Dust evolution in the circumstellar disk of the unclassified B[e] star HD 50138
Gerják, Tímea
We have studied the disk of the unclassified B[e] star, HD 50138, in order to find indications for the evolutionary status of the object (whether it is a young Herbig object or a main-sequence star).Using high spatial resolution 8-13 µm interferometric measurements by VLTI/MIDI we analyzed the size, time-variability and the 10 µm silicate feature.By fitting simple disk models, we determined the inclination and mid-IR size of the disk, thus confirming the former result from less observations. We analyzed the mid-IR temporal variability of different regions of the disk, and concluded that it is not experiencing significant changes over time.We also studied the mid-IR silicate feature, by determining the feature amplitude and the 11.3/9.8 µm flux ratio. The latter parameter is a good indicator of the grain size and crystallinity. The shape of the feature suggests the presence of crystalline silicate grains. We found that the inner disk spectra show weaker silicate feature with larger 11.3/9.8 µm flux ratio compared to the outer disk spectra, indicating larger dust grains in the inner disk. This can be caused by dust evolution, which is also observed in a number of pre-main sequence systems.
Origin and early development stage of solar active regions
Getling, Alexander
The early development stage of active region (AR) 12548 is investigated using observational data of 20–26 May 2016 from the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO). In view of our “strategic” aim of comprehending the sunspot-formation processes, we discuss here the adequacy of the model of the rising loop of a strong-magnetic-flux tube. To this end, we compare the simultaneously measured full-vector magnetic and velocity fields using a Spaceweather HMI Active Region Patch (SHARP).We managed to pick up the very conception of the bipolar magnetic region (BMR) to within a time interval of about 20 min. The leading polarity is found to originate as a compact, isolated feature with a fountainlike magnetic-field structure against the background of a distributed trailing-polarity field and a downflow. The leading and the trailing polarity exhibit a strong asymmetry between their evolution patterns: the leading magnetic element starts developing from a noise-level field strength and reaches a strength of about 2500 G in one day and a half, while the trailing-polarity magnetic element, which had initially a strength of almost 1000 G, grows more slowly and becomes weaker than the leading element. The magnetic fluxes of the two polarities vary in a similar way. No strong horizontal magnetic field is observed in the BMR between the growing leading and following magnetic elements. Also, neither clear-cut material upflows between these sunspots nor remarkably strong horizontal divergent flow is noted. Moreover, small-scale upflows and downflows are mixed, and downflows even dominate at the early evolutionary stage. An intact pattern of supergranulation and mesogranulation is observed over the location area of the growing BMR and around it. Thus, as in the previously analysed AR 11313 (9–10 October 2011), the evolution pattern of AR 12548 strongly disagrees with that definitely predictable based on the rising-tube model.
Multiscale structure of convection due to particularities of thermal stratification
Getling, Alexander
Solar convection controls the processes of magnetic-field structuring, thus affecting the variety of active phenomena. A superposition of cellular convection structures widely differing in their scales (granules, mesogranules, supergranules, giant cells and possibly mini-granules) is characteristic of the solar convection zone, understanding the nature of structural organization of solar convection being thus an important problem of solar physics. In view of the ultimate aim of finding physical factors responsible for the multiscale structure of solar convection, we consider only one of such conceivable factors – the thermal stratification due to a temperature-dependent thermal diffusivity. We carry out three-dimensional numerical simulations of convection in a horizontal fluid layer based on an extended Boussinesq approximation admissive of thermal-diffusivity variations. These variations are assumed to be of a form producing a specific static temperature profile, with the temperature gradient being much greater in its magnitude near the upper layer surface than in the remaining portion of the layer; however, the layer is everywhere convectively unstable. Both free-slip and no-slip boundary conditions at the top layer surface are considered; the bottom boundary is assumed to be rigid. The simulated velocity and temperature fields are analysed using Fourier techniques and computational-homology methods. For both boundary-condition types, the well-developed flow appears as a superposition of cellular convection motions of three scales. In contrast to the largest cells filling the whole layer thickness, smaller cells are localised near the top layer boundary and advected by the larger-scale flows. On the whole, the flow pattern is qualitatively similar to solar-convection pattern formed by supergranules, mesogranules and granules.
GK Car and GZ Nor: Two depleted low-luminosity Galactic RV Tauri stars
Gezer, Ilknur
We present a chemical abundance analyses of two RV Tauri stars GK Car and GZ Nor, on the basis of high-resolution optical spectra obtained with the UVES spectrograph mounted on the 8m UT2 Kueyen Telescope of the VLT array at the Paranal Observatory of ESO in Chili. With an [Fe/H]=-1.32 and a [Zn/Ti]=+1.24 for GK Car and a [Fe/H]=-2.08 and a [Zn/Ti]=+0.77 for GZ Nor, both stars show depletion of refractory elements in their photospheres. Using ASAS photometry, the accurate pulsation periods have been obtained via period analysis. The pulsations of the stars have been used to obtain their luminosities and distances via the PLC relation (Manick et al. 2016). The distance of GK Car is 4.9+/-0.4 kpc and its luminosity is 1800+/-250 Lsun. While for GZ Nor the distance is 10.2+/-0.9 kpc and the luminosity is 2100+/-300 Lsun. RV Tauri stars classified as post-AGB objects by Jura (1986) to show large IR-excess due to thermal emission from circumstellar matter. The luminosity of a post-AGB object is typically expected between 3000 and 10000 Lsun (Van Wickel, 2003). Also, Bertolami (2016) has recently published a detailed grid of post-AGB sequences computed with updated micro and macrophysics. His study shows that new post-AGB models are even 0.1 to 0.3 dex more luminous than the models of similar mass in the older grids (Vassiliadis & Wood 1994; Blöcker 1995a). Recent surveys in the SMC and LMC, a new class of dusty objects termed as "post-RGB" objects have been discovered by Kamath et al (2015b). These objects are evolved, dusty objects and their stellar parameters are very similar to post-AGB objects, except that they have lower luminosities (100-2500 Lsun) than a post-AGB star. These stars very likely evolve off the RGB because of a strong binary interaction process already occurring on the RGB. In this context, GK Car and GZ Nor might be classified as post-RGB stars. This also would imply that they both are binaries which interacted on the RGB (or AGB).
Star forming activity and chemical evolution of the IC10 dwarf galaxy
Gholami, Mahtab
Star forming activity and chemical evolution of the IC10 dwarf galaxyMahtab Gholami1, Atefeh Javadi2, Jacco Th. van Loon3, Habib Khosroshahi2, Mohammad Taghi Mirtorabi1 and Elham Saremi2,4.1 Physics Department, Alzahra University, Vanak, 1993891176 Tehran, Iran2 School of Astronomy, Institute for Research in Fundamental Sciences (IPM), PO Box 19395-5531 Tehran, Iran3 Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG, UK4 Physics Department, University of Birjand, Birjand 97175-615, Iran Amongst the dwarf galaxies in the Local Group, the isolated irregular one, IC10 is one of the most interesting galaxies, with strong star forming activity and the highest density of Wolf-Rayet stars. Undergoing a starburst phase, having numerous HII regions and being bright in all wavebands, makes it an exquisite galaxy to study the internal and external processes that continue to affect dwarf galaxies 14 Gyr since the Big Bang. In this study, we present a new deep and precise optical monitoring survey of IC10 using the Isaac Newton Telescope (INT) with the wide field camera (WFCAM). We performed observations at nine epochs spaced between three to four months apart between 2015 and 2018. We identified Long Period Variable stars (LPVs) and Asymptotic Giant Branch stars (AGBs) to determine the star formation history and chemical evolution of IC10.
Massive stars as progenitors of merging black hole binaries
Giacobbo, Nicola
The recent detection of gravitational waves has proven the existence of massive stellar black hole binaries (BHBs), but the formation channels of BHBs are still an open question. Population-synthesis codes are one of the most powerful tools to investigate the origin of BHBs. In this talk, I describe my new code MOBSE, which is an updated version of the widely used binary population synthesis code, BSE (Hurley et al. 2002). In MOBSE, I have included the most recent models of star evolution, wind mass-loss and core-collapse supernovae, which are the key ingredients to determine the fate of massive stars. Based on the results of MOBSE, I show that only massive metal-poor stars (Z < 0.002) can be the progenitors of gravitational-wave events like GW150914. Finally, I show that most of the binary systems leading to the formation of BHBs pass through the common envelope phase and through a high-mass X-ray binary phase.
Preparing for JWST: a detailed simulation of a MOS deep field observation with NIRSpec
Giardino, Giovanna
With the largest mirror ever to fly in space and a suite of state-of-the-art instruments, JWST willprovide unique data to address key questions about the formation and evolution of galaxies. The multi-object spectrograph (MOS) mode of NIRSpec, in particular, will enable the simultaneous measurement of up to ~200 spectra, over the wavelength range 0.6 - 5.3 micron, of large samples of high red-shift galaxies (up to z ~ 10), for the first time. This powerful instrument mode, however, requires careful planning of the observations and good understanding of the processing steps to go from the detectors' count-rate images to background subtracted, calibrated spectra.To support the community in preparing NIRSpec MOS programs and getting ready to analyze the data, we present here a set of simulations closely mimicking the deep spectroscopic observations that will be performed as part of the JADES survey, a joint effort of the NIRCam and NIRSpec GTO teams. The simulations are made possible by the NIRSpec Instrument Performance Simulator software. This tool consists of two main components: a Fourier Optics wave propagation module coupled with a detailed parametric model of the instruments and a detector module reproducing the response of NIRSpec's two H2RG sensors. The targets for the simulations were selected from the JAGUAR Catalog (Williams et al. 2018).The simulation data package delivered here include the 72 count-rate images corresponding to the exposures break-down of one of the two NIRSpec deep-field spectroscopic programs of the JADES survey, consisting of three dither pointings, for 5 different instrument configurations (low and medium resolution over the entire NIRSpec wavelength range, and high resolution over 2.9-5.3 micron), plus the extracted, background subtracted, spectral traces for each of the 370 targets and corresponding 2D-rectified spectra and calibrated 1D spectra, as well as the mock astronomical data used as the simulation input.
Solar Physics from Unconventional Viewpoints
Gibson, Sarah
We explore new opportunities for solar physics that could be realized by future missions providing sustained observations from vantage points away from the Sun-Earth line (SEL). These include observations from the far side of the Sun, at high latitudes including over the solar poles, or from near-quadrature angles relative to the Earth (e.g., the Sun-Earth L4 & L5 Lagrange points). Such observations fill known holes in our scientific understanding of the three-dimensional, time-evolving Sun and heliosphere, and have the potential to open new frontiers through discoveries enabled by novel viewpoints.
Detection of the Progenitors of Be X-ray Binaries
Gies, Douglas
Be stars are rapidly rotating, non-supergiant B-type stars that ejectequatorial disks. Many of these stars may have been spun up throughmass transfer in a close binary system, in which case the formermass donor star is now a hot, stripped-down, subdwarf. There are a few known cases of Be stars with hot subdwarf (sdO) companionsthat were discovered through International Ultraviolet Explorer (IUE) spectroscopy.Here we report on the search for Be+sdO candidates using archival FUV spectra from IUE.Our search strategy involves calculation of a cross-correlation funtion (CCF)of each observed spectrum with a model spectrum for T_eff = 45 kK,the typical value for the known subdwarf companions. We collected IUEspectra for 264 targets, and selected for closer examination thosewith a CCF peak greater than three times the background CCF noise.We applied two selection criteria to select candidate Be+sdO binaries:targets showing a significant and narrow CCF feature (with a half-width muchsmaller than the projected rotational velocity of the Be star) andalso displayed radial velocity shifts indicative of orbital motion. We identified eight candidate systems that met both criteria plusfour other candidate systems with strong peaks but too few spectrato confirm orbital motion. These are important targets for follow upspectroscopy. The new plus known Be+sdO binaries comprise about 6% of the sample.This fraction is consistent with the idea that we only find sdO companionsin their relatively short and bright evolutionary stage of He-shell burning,while the majority of He-core burning companions are too faint to detectwith current methods. The subdwarf component in some of these systemsis destined to explode as a H-deficient supernova and leave a neutron starremnant. This is the stage of the Be X-ray binaries, the most commonkind of massive X-ray binary.
Millimetre polarization in a disk around a massive protostar
Girart, Josep M.
Here we present deep, 40 milliarcsecond agular resolution, 1.14 mm, polarimetric, ALMA observations towards, the massive protostar driving the HH 80-81 radio jet. The observations resolves the disk oriented perpendicular to the radio jet, with a radius of the ~290 au at 1.7 kpc distance. The continuum brightness temperature, the intensity profile and the polarization properties clearly indicates that the disk is optically thick for a radius of R>170 au. The linear polarization pattern indicates that is dominated by self-scattering. We discuss the effects of self-scattering and radiaton alignment of elongated grains for dust continuum polarimetrics observations aimed to study magnetic fields.
Acoustic astronomy for blind people
Girola Schneider, Rafael
The aim of this project is to offer blind people or people with diminished visual abilities the opportunity to experience the night sky and its celestial bodies through sound. For this, astronomical data were used of the twenty-five brightest stars observable from the Earth, which were related to sound parameters, by synthesis and sound processing. At work, groups of students participated who simulated visual difficulties. The experiences were carried out in the aulic space of the subject of Physics at the National University of Tres de Febrero (UNTREF), where a group of specialists in sound and electronic arts, performed the acoustics of astronomical events, through sound computing programs and instrumentation. Also in the Cielos del Sur Theme Park, city of Chivilcoy, province of Buenos Aires, during the Conference on Teaching and Dissemination of Astronomy. In both practices, the same equipment and the same environment were used. Each installation had a button controller that triggered the sound of each particular star, allowing them to be heard separately or generating a composition of multiple simultaneous sounds. The technologies used were Ableton Live 9, Star API DataBase Json, The 26 Brightest Stars DataBase and a Launchpad controller.Keywords: Stars, Fundamental Parameters, No Seer, Acoustics,
Application of fuzzy logic in the study of exoplanets
Girola Schneider, Rafael
: In recent years, the number of exoplanets discovered involves the use of computer codes that allow us to differentiate both the environmental characteristics of the star system and those that are intrinsic to the exoplanet. In a scenario of uncertainty about the reliability of the data to ensure that an exoplanet may or may not have consistent physical conditions for the development of life, we use a computational tool that works with a fuzzy logic code, which provides a mechanism for Inference, and a mathematical framework that allows to model the uncertainty of cognitive processes, elaborating formal tools for its treatment. In a set of environmental contexts of exoplanets, the research group needs to distinguish reliable results, when the uncertainty of the measures generates an ambiguity in the decision making, reach a consensus to classify or accept a result that is not entirely reliable if other usual techniques are applied. For example, error bars for mass, temperature and atmospheric models. This paper shows how fuzzy logic can be useful in making decisions from ambiguous predicates, using a fuzzy computer code, obtaining numerical data associated with indeterminate variables.Keyword: Exoplanets, Fuzzy logic, Models, classification.
Application of fuzzy logic in the study of the variety of galaxies in the universe
Girola Schneider, Rafael
According to the most recent observation techniques, the great variety of galaxies existing in the near universe, shows the complexity of the physical processes responsible for their formation and evolution. The observations show the properties of galaxies that are at different distances. A model that explains the evolution of galaxies for different distances must be consistent in order to reproduce the local universe, since it represents the end point of evolution. As a continuation of the work on fuzzy logic in the context of the classification of galaxies, the theoretical and practical foundations of a method for the study of sky surveys are presented, in different wavelengths, analyzing the relationships between the properties of the stars, gas and dust that make up the galaxies at different times, using the information obtained (type, age, redshift) as validation measures for the optimal determination of stellar clusters, using fuzzy logic algorithms.
Immersed Moonlets and the lifetime of Saturn's ring arcs
Giuliatti Winter, Silvia
Data obtained by Cassini spacecraft showed the existence of three tiny moons around Saturn Anthe, Methone and Aegaeon coorbital to planetary arcs. The existence of these systems is assign to corotation eccentric resonance (CER) with the satellite Mimas: 10:11 to Anthe's arc, 14:15 to Methone's arc and 7:6 to G ring arc (Aegaeon's arc). A corotation resonance m+1:m is responsible to create m sites where the particles will be azimuthally trapped. This can explain the existence of the planetary arcs. Based on the results presented by Madeira et al. (2018, in press) which shows that the main contribution of Aegaeon is to act as a sink for the arc population, we propose that the 7:6, 14:15 and 10:11 CER regions present only one arc (the other sites are empty) because the other sites would have tiny moonlets which help to clean these regions populated by micrometer sized particles.The numerical simulations were performed using the Mercury integrator package (Chambers 1999). The dynamical system ir formed by Saturn and its gravitational coefficients (J2, J4 and J6), Mimas, tiny moons and a set of ring arc particles.Our results showed that without dissipative forces the particles remain confined in the sites for more than 100000years. If the arcs are formed by micrometer sized particles, the effects of the solar radiation force reduce this lifetime for less than 1000 years. The gravitational effects of a tiny moon immersed in the arc help to reduce its lifetime. The mass production due to collisions between interplanetary debris onto the surface of the moons can not supply the arc with micrometer sized particles in order to maintain it in a steady state. Therefore the arcs seem to be transient features even in a presence of tiny moons. We will discuss the size of the tiny moons and its role in the lifetime of the arcs.The authors thank CNPq (309714/2016-8) and Fapesp (2016/24488-0) for the financial support.
Comet Plates in the SAAO Archives
Glass, Ian
The archival plate collection at the South African Astronomical Observatory, which incorporates that of the former Royal Observatory, Cape of Good Hope, contains numerous images of transient phenomena, particularly of comets. The latter number over 900 and date from the late 19th century to the late 20th.One of the first comets to be photographed was the Great Comet of 1882. Several early images of this exist, taken by amateur photographers and or with experimental photographic telescopes. The presence of background stars led David Gill to propose photography as the most efficient means for producing the Southern counterpart to the Bonner Durchmusterung, namely the Cape Photographic Durchmusterung.The plates in the collection are mostly16 × 16 cm and were taken with the Astrographic (Carte du Ciel), McClean, and MRM telescopes.We will present further information on the collection and current conservation work as well as showing some example prints.
Measuring Magnetic Fields from Water Masers in the Synchrotron Protostellar Jet in W3(H2O)
Goddi, Ciriaco
Magnetic fields are invoked to launch, drive, and shape jets in both low- and high-mass protostars, but observational data on the spatial scales required to assess their role in the protostellar mass-loss process is still scarce.We report full polarimetric VLBA observations of water masers towardsthe Turner-Welch Object in the W3(OH) high-mass star formingcomplex. This object drives a synchrotron jet, which is quiteexceptional for a high-mass protostar, and is associated with astrongly polarized water maser source, W3(H2O),making it an optimal target to investigate the role of magnetic fieldson the innermost scales of protostellar disk-jet systems.The linearly polarized emission from water masers provides clues on the orientationof the local magnetic field, while the measurement of the Zeemansplitting from circular polarization provides its strength.The water masers trace a bipolar, biconical outflow at the center of the synchrotron jet.Although on scales of a few thousand AU the magnetic field inferredfrom the masers is on average orientated along the flow axis, onsmaller scales (10s to 100s of AU), we have revealed a misalignmentbetween the magnetic field and the velocity vectors, which arises fromthe compression of the field component along the shock front.Our measurements support a scenario where the magnetic field would evolve fromhaving a dominant component parallel to the outflow velocity in thepre-shock gas, with field strengths of the order of a few tens of mG(at densities of 107 cm-3), to being mainly dominated by theperpendicular component of order of a few hundred of mG in the post-shock gaswhere the water masers are excited (at densities of 109 cm-3).The general implication is that in the undisturbed (i.e. not-shocked)circumstellar gas, the flow velocities would follow closely themagnetic field lines, while in the gas shocked by the prostostellarjet the magnetic field would be re-configured to be parallel to the shock front.
Theoretical Modelling of Chromospheric Emission Lines for Solar Spectral Irradiance Through The Solar Activity Cycles 21-23
Göker, Ümit Deniz
In our previous work, we indicated the close connection of the classes of sunspots/sunspot groups (SGs), facular areas and plage regions with the solar spectral irradiance (SSI) from the negative correlation between international sunspot number (ISSN) and chromospheric emission lines. From this work, we found that the intensity of Fe II (298.5 nm line) ion in the last solar minimum were higher than the two previous solar minima 21 and 22. The variability of Fe II ion 298.5 nm line is in close connection with the facular areas and plage regions, and the sizes of these solar surface indices play an important role for the SSI variability, as well. So, the velocity of particles of these ions increase with decreasing density of the medium and increasing plage surface. Increasing velocity causes an increase in the acceleration and the intensity of the particles. In this work, we introduce a theoretical model for the relation between the size of the plage regions and chromospheric emission lines.
Infrared light curves of dusty & metal-poor AGB stars
Goldman, Steve
The effects of metallicity on both the dust production and mass loss of evolved stars have consequences for stellar masses, stellar lifetimes, the progenitors of core-collapse supernovae, and the origin of dust in the ISM. With the DUST in Nearby Galaxies with Spitzer (DUSTiNGS) survey, we have discovered samples of dusty evolved AGB stars out to the edge of the Local Group, reaching metallicities down to 0.6% solar. This makes them the nearest analogs of AGB stars in high-redshift galaxies. We present new infrared light curves of the dustiest AGB stars in 10 galaxies from the DUSTiNGS survey and show how the infrared Period-Luminosity (PL) relation is affected by dust and by metallicity. These results have implications for the efficiency of AGB dust production at high-redshift and for the use of the Mira PL relation as a potential distance indicator.
Mid-IR spectroscopic observations of the dustiest AGB stars in the Galaxy
Goldman, Steve
We have used the VISIR spectrograph at the Very Large Telescope to target 21 of the most luminous and heavily-obscured oxygen-rich evolved AGB stars in the galaxy. Low resolution N-band (8 - 13 um) spectroscopy was used to target the 10 µm silicate feature. The sample, with a median luminosity of ~10,000 solar luminosities and a median mass loss rate of ~10-4 solar masses per year, has shown higher mass loss rates than previous Galactic and Large Magellanic Cloud samples, given their luminosities. These results, along with expansion velocities from previous OH maser detections, have been used to test and refine the wind-driving and mass loss mechanisms. Our new spectra have also allowed us to study the dust composition and geometries of these sources.
YORP classification of asteroids revisited
Golubov, Oleksiy
We analyze the YORP evolution of asteroid rotation states depending on their shapes, and discover yet unknown symmetries between different components of the YORP effect. We find a simple theoretical background behind the phenomenological classification of asteroids into four types depending on their YORP behavior by Vokrouhlický and Capek (2002, Icarus 159, 449). Although it has long been known that the obliquity component of YORP can change sign as the rotation rate increases (Capek and Vokrouhlický, 2004, Icarus 172,.526), we find that the number of sign alterations is always even, so that the signs of YORP at very slow and very fast rotation rates is always the same. The points of sign alteration can serve as YORP equilibria and attractors. Unexpectedly, it turns out that even a symmetric asteroid can experience the obliquity component of the YORP effect. We also describe the simplest and most generic evolutionary tracks of asteroids, as well as more subtle effects capable of changing the topology of the evolutionary trajectories and creating stable rotational equilibria for asteroids.
Dark Skies Rangers: a flagship to bridge the gap between schools and communities
Gomes, Nuno
A large network of European schools is currently being created in the framework of the Open Schools for Open Societies (OSOS) H2020 project. The main goals of OSOS are to enable schools to become hubs for science communication in their local communities, to be incubators of exploration and invention, to be accelerators of innovation and to promote open schooling.Dark Skies Rangers (DSR), one of the flagships of OSOS, is a project focused on fighting the light pollution and giving back starry skies to the worldwide populations. It tries to create awareness for the impact of light pollution in our economy, in security, in ecosystems and in human health, thus meeting the goal of protecting dark and quiet skies of the IAU Strategic Plan for the 2020-2030 decade. DSR is being used as an accelerator for OSOS, i.e., an idea that facilitates the transition from a traditional teaching system to an open schooling model, where students identify problems within their local communities and carry out scientific projects with the aim of solving them.In this talk we will present OSOS and will focus on DSR, describing several examples of how communication efforts being implemented in Portuguese schools are affecting the behaviour of local communities, authorities and policy makers towards the creation of awareness for the problematic of light pollution, and designing innovative solutions.
The impact of kinematics on the SFH of the Herschel Reference Survey (HRS)
GOMEZ LOPEZ, Jesus Alberto
The Herschel Reference Survey (HRS) is a complete K-band-selected, volume-limited sample of 323 nearby galaxies spanning a wide range in morphological type and stellar mass. Gathering and analyzing high-resolution 2D Perot-Fabry spectroscopic H-alpha data for the star forming objects of the sample is providing a complementary kinematical information to the sample. I have been actively participating in a long-term observing campaign started in December 2015 and scheduled for 3 years, at the 1.93m telescope at OHP observatory with GHASP instrument, and at the 2.1m telescope in SPM Observatory using the PUMA instrument. Combined with multifrequency data spanning the whole electromagnetic spectrum (from UV GALEX to far-IR Herschel, including HI and CO), and multizone chemo-spectrophotometric models of galaxy evolution as well as with the CIGALE SED fitting code, these data are necessary to study the role played by velocity rotation and turbulence down to kpc scales in the process of star formation occurring in normal late-type galaxies. This is being done by comparing the radial variations of the star formation activity of galaxies, corrected for dust attenuation using infrared data, and modulated by the variation of the rotational velocity, to the gas surface density of the galaxies. The multifrequency dataset in hour hands will allow us to determine in a self consistent way, and with unprecedented precision, the 2D-distribution of the different galaxy components (atomic, molecular, dust masses), the dust attenuation, the typical age and metallicity of the different stellar populations and several other properties critical for the study of the radial variation of the star formation history of these galaxies.
Dense star formation in metal-poor galaxies: an ALMA perspective
Goncalves, Thiago
In this talk, I will present the result of an observational project using ALMA to investigate the properties of the molecular gas in low-redshift (z~0.2) ultraviolet-luminous galaxies. These objects are extremely dense, highly star-forming and very metal-poor compared to other galaxies of similar stellar mass at the same redshifts, justifying their use as analogues to distant main-sequence galaxies in an attempt to understand the interplay between gas and star formation under similar conditions in the early universe. We have observed the most metal-poor objects in our sample, in order to determine whether metallicity plays a role in CO emissivity of the molecular regions in galaxies down to 10^9 solar masses. Our four non-detections, with stringent upper limits, show that CO is severely depleted, even under turbulent conditions. We discuss the implication for observations of sub-L* galaxies at high redshift, which are considerably more metal-poor than objects with similar stellar masses in the local universe.
Quenching or bursting? Physical processes in green valley galaxies and the star formation acceleration
Goncalves, Thiago
One of the main open questions in contemporary astrophysics is how galaxies quench star formation. The observed color bimodality is a strong indication that galaxies do not passively exhaust their gas reservoirs, instead requiring an active process that shuts down star formation over short timescales. In this talk I will show recent results by our group measuring quenching timescales of galaxies in different epochs and of different types, supporting the idea that some processes are more efficient for quenching star formation. I will also present a new technique combining spectroscopic and photometric indices that allows for a measurement of the time derivative of the star-formation rate, i.e. the star formation acceleration. This new measurement has strong potential for impact on studies of galaxy evolution, comparing for example the quenching timescales of galaxies with and without AGN activity. Nevertheless, it depends strongly on high signal-to-noise spectra of the continuum in nearby and distant galaxies. In that context, I will discuss how a deep spectroscopic survey with multi-object spectrographs in next generation telescopes, such as MOSAIC, could help us extend such studies to the peak of star formation activity in the universe, around z~2.
AGN vs starburst: growing a black hole in a compact star-forming galaxy
Goncalves, Thiago
In this talk, I will present the result of a recent observational project using ALMA to investigate the properties of the molecular gas in low-redshift (z~0.2) ultraviolet-luminous galaxies. These objects are extremely dense, highly star-forming and very metal-poor compared to other galaxies of similar stellar mass at the same redshifts, justifying their use as analogues to distant main-sequence galaxies in an attempt to understand the interplay between gas and star formation under similar conditions in the early universe. We have observed one object in this sample with high spatial resolution, comparing data from CO emission and hydrogen recombination lines down to a resolution of ~400 pc, allowing for a detailed analysis of the conversion of gas into new stars. In particular we are able to compare star formation laws in individual clumps and the surrounding ISM, highlighting the difference between star formation efficiencies in each environment within the galaxy. More specifically, we can investigate in extreme detail the central star-forming region where AGN activity is present (as indicated by x-ray observations), although the bolometric luminosity of this region is dominated by star formation activity. This presents a unique opportunity to investigate the establishment of the m-sigma relation in central bulges while star formation is still active.
Astronews: scientific journalism in developing countries
Goncalves, Thiago
Astronomy is undoubtedly an attractive field and presents a major opportunity to promote science anywhere in the world. Nevertheless, this is a major challenge in developing countries, where investment in outreach is small, and the inflow of information from press offices in wealthier nations is dominant. The end result is a lack of awareness and/or interest in science, or alternatively an impression of monopoly in scientific discoveries by developed economies. In this talk I will present a Brazilian project started in 2017 and financed by the IAU Office of Astronomy for Development that aims to address the problem. More specifically, we have created a working group dedicated to promoting national science, acting as liaison between the academic community and the press, with a goal to raise public awareness, attract new talents, and hopefully encourage economic development through investment in science. I will discuss the challenges faced thus far, the strategies used in establishing contact with journalists and our recent attempts to expand the project to other Latin American countries.
A step further on the physical, kinematic and excitation properties of PNe
Gonçalves, Denise R.
Planetary nebulae (PNe) are known to be photoionized objects. However they also have small-scale, low-ionization structures (LIS) with different behaviour in terms of excitation. We are only now starting to answer why most LIS have lower electron densities than the PN shells hosting them, and whether or not their intense emission in low-ionization lines is the key to their main excitation mechanism. Therefore, can LIS line ratios, chemical abundances and kinematics enlight the interplay between the different excitation and formation processes in PNe? Based on the spectroscopic analysis of five PNe that possess LIS, we confirm that all nebular components have comparable electron temperatures, whereas the electron density is systematically lower in LIS than in the surrounding nebula. We also confirm that there is no chemical abundance contrast between LIS and other PN components. More importantly, by using diagnostic diagrams from shock models, we demonstrate that LIS's main excitation is due to shocks, whereas the other components are mainly photoionized. We propose new diagnostic diagrams involving a few emission lines ([N II], [O III], [S II]) and log(fshocks/f*), where fshocks and f* are the ionization photon fluxes due to the shocks and to the central star ionizing continuum, respectively. The new diagrams clearly separate the structures of the PNe in photo- and shock-excited components, also defining a region where both mechanisms play a role.
A candidate of pulsar binary with orbital period of 14 minutes
Gong, Biping
Up to date, the shortest orbital period of radio pulsar binaries is 95 minutes. Here we point out that tidal effect occuring on pulsar binaries with short orbital period can perturb the orbital elements resulting in abnormal orbital modulation, which make such binaries more difficult to find. Abnormal timing residual of PSR B0919+06 is thus simulated by tidal effect occurring on an ultra-compact binary, which predicts that it is a candidate of ultra-compact binary of orbital period of 14 minuted with a companion star of white dwarf star. Applying such a new approach to other binary candidates could allow us to find some interesting ultra-compact binaries.
High sSFR galaxies: Main Sequence outliers or the new "normal" at high-z?
Gonzalez, Valentino
The main sequence of star forming galaxies has become one of our maintools to study galaxy evolution. This Mstar vs. SFR correlation holdsfor most star forming galaxies throughout the history of the Universe,so much so, that we often call galaxies belonging to the MS, "normal".This is especially true at high-z when most galaxies were actively starforming. While Mstar estimates are fairly robust, the SFR is moresensitive to the many assumptions that go into SED modeling. At z~2, SEDmodeling with standard assumptions yields a small fraction (<25%) ofgalaxies that are better fit with extreme models having very high sSFR,low extinction, and young ages (<30 Myr). The fraction of outliers isespecially high among dwarf galaxies (log(m/msun)<8) and at high-z.Depending on the assumptions the majority of sources at z~6 could beoutliers, bringing into question our use of the term "normal galaxy". Itis possible that the extreme models are just an artifact of SED modelingdue to unsuitable modeling assumptions. For example, the typical SFH ofthese galaxies could be very different to the ones assumed in standardmodels. Other more interesting alternatives include a higher fraction ofbinarity in their stellar populations and/or a top heavy IMF. All ofthese alternatives point to producing more high-energy photons per unitstar formation which has important consequences for the study of cosmicreionization. Unfortunately, broad band photometric data is not adequateto constrain these alternatives but some faint spectroscopic signatures in thefar UV spectrum of galaxies could be key. A few studies have shown thepresence of high ionization emission lines (HILs) in the UV spectrum ofthese MS outliers. In this presentation we will show preliminaryresults in our systematic search for HILs in MS outliers and theconsequences it has for SED modeling and galaxy evolution, cosmicreionization, and future observability with JWST and thirty meter classtelescopes
Tracers of stellar mass loss: Mid-IR colors and surface brightness fluctuations
Gonzalez-Lopezlira, Rosa Amelia
I present integrated colors and surface brightness fluctuation magnitudes in the mid-IR, derived from stellar population synthesis models that include the effects of the dusty envelopes around TP-AGB stars. The models are based on the Bruzual & Charlot CB* isochrones; they are single-burst, range in age from a few Myr to 14 Gyr, and comprise metallicities between Z = 0.0001 and Z = 0.04._x005F I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with higher than fiducial mass-loss rate are needed to fit the mid-IR colors of ``extreme" single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5 um and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediate age populations, between 100 Myr and 2-3 Gyr. Observations with the upcoming JWST should be able to resolve global changes in the mass-loss rate of a stellar population, and actually resolve whether a relation between metallicity and mass-loss exists.
Rapid evolution of the SS 433 system with relativistic jets
Goranskij, Vitaly
The eclipsing system SS 433 (V1343 Aql) with moving emission lines in the spectrum consists of an A4-A8 giant (Gies et al., 2002) and a neutron star (Goranskij, 2013). The moving components of Balmer and He I lines are formed by a pair of oppositely directed, highly collimated and precessing relativistic jets of gas moving with a velocity of 0.26 c. The orbital period of 13.082 day, the jet precession period 162 days, and jet nodding period 6.28 day are present in both photometric and spectroscopic data. The star is located in the center of radio structure W50 interpreted as a 10000-year old supernova remnant. We present the results of forty-year monitoring, which includes multicolor photometry and synoptic observations analyzed along with fragmentary spectroscopic and radio data. Photometry shows secular trend towards decreasing amplitudes of all periodic variations by about 40 percent. We observed episodes of eclipse disappearance during several orbital periods. We explain such episodes as consequence of a sporadically forming common envelope, when Roche lobe of the neutron star is overfilled. Then gas flows in the circumbinary extended and precessing disk (earlier described by Barnes et al., 2002) through the Lagrangian point L2. We observed also episodes of blocking the jets by the common envelope, the explosive ejection of the common envelope, and recovery of the jets. These phenomena suggest that the mass transfer from the A-type companion passes into a dynamical timescale.
Improving the X/S Reference Frame with the VLBA
Gordon, David
VLBA observations have enabled us to greatly improve the precisionof ICRF3, which will be presented for approval at the 2018 IAU meeting.Of the 3414 sources in the Second Realization of the InternationalCelestial Reference Frame (ICRF2), approximately 2/3 were singleepoch VLBA Calibrator Survey (VCS) sources that had average positionuncertainties nearly 5 times worse than the other 1/3. Several VLBAobserving campaigns since 2014 have been undertaken to re-observe thesefor ICRF3. Some 32 X/S 24-hr VLBA astrometry sessions have now been runand analyzed. For the sources in the original ICRF2 VCS class,formal position errors have been reduced by an average factor of nearly7. The VLBA observations have also included many other sources resultingin the addition of 436 new sources to the X/S reference frame for ICRF3.
Using Blue Straggler Binaries to Constrain AGB Mass Transfer
Gosnell, Natalie
Complete membership studies of open star clusters reveal that 25% of the evolved stars follow pathways in stellar evolution that are impacted by the presence of binary stars. Recent studies show that the majority of blue straggler stars, traditionally defined to be stars brighter and bluer than the corresponding main sequence turnoff, are formed through mass transfer from an Asymptotic Giant Branch (AGB) star onto a main sequence companion. We will present Hubble Space Telescope COS ultraviolet spectroscopy of WOCS 4540, a blue straggler-white dwarf binary in open cluster NGC 188 that formed through mass transfer from an AGB star onto a main sequence companion. The current cooling temperature of the white dwarf sets the timeline for the mass transfer history, and the mass of the white dwarf tells us the core mass of the AGB star at the end of mass transfer. The system must have experienced at least 60% mass transfer efficiency to create the blue straggler mass seen today. The existence of this binary in a well-studied cluster environment provides a unique opportunity to constrain both the pre- and post-mass transfer systems, improving our understanding of mass transfer and the interplay of AGB stars and binary dynamics.
The present situation of Nano-JASMINE and Small-JASMINE
Gouda, Naoteru
We are now focusing on the development of two missions; those are Nano-JASMINE and Small-JASMINE whose missions are complementary to Gaia mission.The Nano-JASMINE, with a primary mirror aperture of 5-cm, will produce scientific results based on the astrometric information of bright stars in the neighboring space. Nano-JASMINE will operate in zw-band (0.6~1.0 micron) to perform an all sky survey with a precision of 3 mas for positions, parallaxes and proper motions. The combination of the observational data from Nano-JASMINE and the Hipparcos Catalogue is expected to produce more precise data on proper motions (~0.1mas/yr) .We are making progress on a Launch Services Agreement for Nano-JASMINE with a company for small rockets.An additional plan is underway to launch Small-JASMINE, with a primary mirror aperture of 30-cm, in around 2024. Small-JASMINE will provide positions and parallaxes accurate to ~20 micro-as for stars, brighter than Hw=12.5 mag (Hw-band: 1.1 ~ 1.7 micron). Proper motion precision of ~20 micro-as/yr is expected. This satellite will engage in observations of a limited area around the Galactic nuclear bulge and certain specific astronomical objects. One example of the main scientific objectives is to clarify the dynamical structure of the Galactic nuclear bulge and search for observational relics of a sequential merger of multiple supermassive black holes to form Sgr A* at the Galactic center. We have been aiming at the realization of the Small-JASMINE mission as a mission of the small science satellite program (Medium Class mission) executed by JAXA. We should have multiple steps of reviews by JAXA. Small-JASMINE successfully passed the Mission Definition Review (MDR) and an international review which was executed as a part of a review of planning by the executive officer of ISAS/JAXA. We are now proceeding the further detailed investigation and technical demonstration tests to pass following reviews by JAXA.
GalRotpy: an educational tool to understand and parametrize the rotation curve and the gravitational potential of disc-like galaxies
Granados, Andrés
GalRotpy is an educational Python-based visual tool, which is useful to understand how is the contribution of each mass components to the gravita- tional potential of disc-like galaxies and in the corresponding rotation curve. The standard gravitational potential of disc-like galaxies can be built by the contribution of a Miyamoto-Nagai potential model for both bulge/core and thin disc together with an NFW (Navarro-Frenk- White) potential or Burkert (for cored density profile) potential for the Dark Matter halo. The GalRotpy tool can give a first approximation of the galaxy rotation curve using the following schemes: (i ) a bulge model, (ii ) a thin or thick disc (iii ) and an exponen- tial disc model for the stellar component and (iv ) a Dark Matter halo. The axisymmetric gravitational potential calculations are based on galpy package. After a brief review of gravitation potential theory, we focus on the construc- tion of the rotation curves of disc-like galaxies. We present two study cases, the rotation curves of NGC6361 and M33 galaxies. According to the results found, GalRotpy is useful to modelling rotation curves and to estimate realistic grav- itational parameters of galaxies. It can be used for the Milky Way galaxy and other extragalactic sources. Keywords: dark matter, gravitation, galaxies: kinematics and dynamics, galaxies: spiral, galaxies: fundamental parameters, methods: numerical
Intermediate luminosity optical transients: the case of Eta Carinae
Grant, David
Between the well studied classes of supernova explosions and nova eruptions, a large luminosity gap exists. Intermediate luminosity optical transients (ILOTs) are a diverse group of stellar systems, known to exhibit peak luminosities within this range and are becoming an evermore exciting class of laboratories for studying outflows and binary stellar evolution. I will present a detailed analysis of the massive stellar binary Eta Carinae, comprising a massive main-sequence star and a luminous blue variable that has erupted dramatically in its past: this system is often regarded as a supernova imposter. My investigations are based on optical spectroscopy from the Global Jet Watch observatories, giving highly time-resolved dynamical information, over a 4-year period, spanning periastron. This unique dataset allows us to elucidate the evolving dynamics of the system giving us insights into one of the most famous ILOTs known today.
Probing the physical conditions surrounding young star clusters: inferences from features of molecular, atomic and ionized species
Gregorio-Hetem, Jane
The scenario of star clusters formation can be better understood based on the detailed study of the dynamical conditions of the associated gas, clustering properties and effects of ionizing sources, among others. Our previous works revealed an exotic environment surrounding several young stellar groups. A study of fractal statistics of young clusters showed the stars distributed in filamentary sub-structures that were probably formed under supervirial conditions and feedback from massive stars (ionization, winds). The answer for questions raised from our previous results depends on the comparison among the distributions of molecular, atomic and ionized gas for a large sample of objects, which are investigated here by means of optical and infrared observations obtained with the SOAR and T80S telescopes for a selected sample of star clusters and associations. These observations provided a complete catalog with multiband photometric data for the members of the studied star-forming regions and clusters that were characterized according to the color-color diagrams and fluxes ratios, which are indicators of accretion rate, magnetic activity and the physical conditions of the nebular emission.
Magrathea: A proposal for a satellite mission on protoplanetary dust growth experiments
Greif, Jonas
The physics of particle growth in protoplanetary disks is still not fully understood, e.g. the growth gap between dust grains and mm-sized particles. Additionally, current methods cannot model the full complexity of interactions in this phase of planet formation. Therefore, experiments in microgravity are crucial to revealing the underlying physics. Previous experiments have several limitations in particular their short duration and constrained dimensions. Accurately representing the conditions in the protoplanetary disk, such as the dust particle mean free path and large spatial extent of the dust, longer duration experiments are needed.In order to create the best conditions for these experiments, here we present a concept satellite with a 6m3 chamber. The payload bay provides different measurements of ongoing collision processes, and samples of collision products. Its modularity and capacity is designed to carry several instruments in a carrousel, with 28 experiment canisters. Those experiments have a range of compositions (including Silicate and Fayalite, both with or without ice layers), and size distribution (between 1µm and 100mm), probing the conditions that could benefit grain growth. Each experiment will last up to one month allowing the record of approximately 106 collisions, with relative velocities of up to 5mm/s, obtaining statistically meaningful results.With the science objectives and requirements formulated, we consider the experiment phase will last up to 5 years. During that time external influences should be minimised, in respect to the structure, thermal control, and attitude control. Therefore, we suggest a 1000kg spacecraft solution, set on a 800km Sun-synchronous orbit. The mission would cost around 438MEuros.The full work was developed during 10 days of the 2017 Alpbach Summer School, by a group of fifteen young scientists and engineers, with various backgrounds, from all across Europe, with the support of two dedicated tutors.
Temperature-Dependent Laboratory Measurements of the Far-Infrared to Millimeter Opacity of Carbonaceous Dust-Analogues
Greif, Jonas
We are measuring and analysing the FIR- and THz- Spectra of pyrolysed micro-crystalline cellulose as an analogue of carbonaceous interstellar dust. We are using cellulose-powder with a crystal size of 20µm and are heating it up to temperatures of 1000°C. First results of the mass normalised extinction are presented and compared to Jäger et al. (1998). The temperature dependent measurements took place in a dry environment at cooling temperature between Tc=300K (room temperature;RT) and Tc=10K.Our aim is to assess carbonaceous dust analogues in terms of structure, nature and morphology. For theoretical and observational investigation we are going to determine their optical constants. Furthermore, we are going to calculate the emission cross section of particles with different geometries to compare them with the measured results.
Under One Sky: Women in Astronomy
Griffin, Elizabeth
Of all the sciences, astronomy is by far the most border-less in its activities, and the most advanced in its concepts of collaborating across borders. As this talk will outline, today's teams and groups are becoming mature enough to ignore gender differences and ethnic differences, and even across the past 50+ years' of IAU membership which I personally can chalk up, the IAU personnel, Commissions, and other bodies have reflected quite faithfully the same - albeit small-- quotas as found in its member_x005F institutions. There was space for the individual, and if one recalls the contributions by major players like Edith Muller, Giusa Cayrel, Anne Underhill and Charlotte Moore, I think it can be said that astronomy was, and knew it was, better off by giving such people the latitude that they deserved as scientists, rather than because they were women. When a meeting in Baltimore in 1988 was called to discuss "Women in Astronomy", the pressure came from the younger generations, who feared that the low percentages of tenured women would be allowed to continue in astronomy unnoticed, so they drew up the Baltimore Charter to draw attention to what certainly appeared to some as unfairness. Even though there could be no quick fixes to the situation, and the winds of change have been more like zephyrs than the cleansing gales that some hoped for, the percentage of women now rising up through the ranks is definitely on the increase, and is enjoying increasing ethnic diversity. Yes, problems still remain, but no community of skilled humans is perfect.
Trans-disciplinary re-use of historical stellar spectra
Griffin, Elizabeth
Ozone in the Earth's stratosphere has only been studied quantitatively since the early 1920s. Measurements have been carried out daily at a station in Switzerland since 1926, and constitute our only long-term continuous record of such data. Unfortunately, upgrades or corrections to the basic equipment which it used through the early decades were very susceptible to systematic errors when changes were carried out, as there were often rather insufficient back-ups planned. However, independent sources of ozone information are still badly needed, especially to help validate the early Swiss data in order to determine whether (as popularly supposed) ozone concentrations have always remained constant until acted on by an external force like released CFCs, or whether they underwent their own natural temporal changes, such as might mimic a small ozone "hole". Selected stellar spectra have proved vital in this connection, though tantalizingly so since the original ozone-measurements project is still unfinished through a lack of sufficient funding.
The Discovery and Properties of a Newly Discovered Compact Lensing Cluster CLIO at z=0.42: A unique JWST target
Griffiths, Alex
We present the results of a new study of a unique compact lensing cluster we name CLIO, at redshift z = 0.42, discovered through the GAMA survey using spectroscopic redshifts. Compact and massive clusters such as this are understudied, but provide a unique prospective on dark matter distributions and for finding background lensed high-z galaxies. The CLIO cluster was identified for follow up observations due to its almost unique combination of high mass and dark matter halo concentration, as well as having observed lensing arcs from ground based imaging. Using deep FORS2 and Spitzer imaging in combination with MUSE optical spectroscopy we identify 89 cluster members and background sources out to z = 6.49. We describe the physical state of this cluster, finding a strong correlation between environment and galaxy spectral type. We furthermore measure the total mass of CLIO to be 4 x 10^{14}$ solar masses . We build and present an initial strong-lensing model for this cluster, and measure a relatively low intracluster light (ICL) fraction of ~7%. Due to its strong potential for lensing background galaxies and its low ICL, the CLIO cluster will be a target for our 110 hour JWST `Webb Medium-Deep Field' (WMDF) GTO program.
FOSSILs in the Galactic Halo
Grillmair, Carl
We use a matched filter to detect compact groups of old, metal-poor stars that we term FOSSILs (Fragments of Old Stellar Systems In Limbo). With size scales on the order of 10 arcminutes, distances ranging from 2 to 200 kpc, and memberships ranging from a handful to several dozen stars, these FOSSILs stand out from the surrounding field and are presumably signatures of, or debris from, ancient star clusters and dwarf galaxies. They may be localized concentrations of stars within more extensive tidal streams, and in several cases may be the signatures of extant but heretofore undetected ultrafaint galaxies. Using magnitudes and colors from the Pan-STARRs survey, we detect 140 such FOSSILs at 5σ or greater in a 2200 square degree region in the vicinity of the north Galactic pole. Spectroscopic and astrometric follow-up of these FOSSILs will be required to determine the nature of these structures, deepen our understanding of the make-up and accretion history of the Galactic halo, and perhaps alleviate the missing satellites problem.
Observing Pop. III Stars with HARMONI and the E-ELT
Grisdale, Kearn
Instruments like HARMONI on the E-ELT will likely be able to observe the first spatially resolved spectra of the very earliest (z~10) galaxies. Contained within these spectra will be details of the very first and as of yet unobserved stars, i.e. Population III stars. Detecting the emission from Pop. III stars would provide significant insight into star formation, galaxy formation and evolution in the early Universe. Using New Horizon, an AMR-hydrodynamical cosmological simulation, in combination with published SEDs for Pop. III stars and full radiative transfer (i.e. the Yggdrasil Models and CLOUDY look-up tables respectively) I am able to compute and simulate the flux of the He II 1640Å line, a tracer of the presence of Pop. III stars, produced by the simulation. Mock observations of these galaxies can then be used to provide insight into whether these stars are observable and which of their physical properties will be determined by the HARMONI and E-ELT. In this talk I will demonstrate:How mock observations of Pop. III stars can be producedWhat physical properties of Pop. III stars can be determined from observationsHow such observations can be used to rule out different PopIII models when combined with real observations from the HARMONI on the E-ELT
Emission and Absorption lines: the keys to unlocking galaxy properties
Grisdale, Kearn
Within the the next decade, instruments like HARMONI on the E-ELT will routinely provide spatially resolved spectra of high redshift (z~2-3) galaxies. Analysis of these spectra, via both emission and absorption lines, will provide a detailed look into the physical properties of these early galaxies. We have developed a method for simulating the emission line flux in H-alpha for large number (~20) of galaxies found in New Horizon, an AMR-hydrodynamical cosmological simulation, at a range of different redshifts. Using this library of mock observations, we can start to look into the statistical properties of the galaxy population (e.g. distribution of v/sigma as a function of mass, luminosity, redshift). Furthermore, mock observations provide a means of testing different "sub-grid physics" in the cosmological models by making predictions of what observational signatures will result from different choices. These simulations will drive the development of key observing programmes for HARMONI.
Experimental light scattering by ultrasonically controlled small particles
Gritsevich, Maria
Electromagnetic scattering is a fundamental physical process that allows inferring characteristics of an object studied remotely. This possibility is enhanced by obtaining the light-scattering response at multiple wavelengths and viewing geometries, i.e., by considering a wider range of the phase angle (the angle between the incident light and the light reflected from the object) in the experiment. Planetary environments represent numerous examples of scattering media composed of particles. There is a fundamental difficulty, however, in bridging the gap between the light-scattering theory and experiment: while existing theoretical models can be used reliably to simulate scattering by a fixed finite object or random particles, thorough experimental work has mostly been performed with light scattered from surfaces. We present an overview of our newly developed 3D scatterometer — a setup for precise multi-angular measurements of light scattered by mm- to µm-sized samples held in place by sound. The measurements obtained with the scatterometer can be cross-validated against the modeled light-scattering characteristics of the sample, i.e., the intensity and the degree of linear polarization of the reflected light, calculated with state-of-the-art electromagnetic techniques.
Consequences of meteoroid impacts based on atmospheric trajectory analysis
Gritsevich, Maria
One of the important steps in the prediction of an impact threat to Earth raised by potentially hazardous asteroids is the understanding and modeling of the processes accompanying the object’s entry into the terrestrial atmosphere. Such knowledge enables characterization, simulation and classification of possible impact consequences. For observed meteor events the reconstructed atmospheric trajectory is the key to deriving the pre-impact meteoroid's orbit in the Solar System on one hand, while on the other hand, it is also required for dark flight simulations which enables to locate surviving meteorite fragments on the ground. Using dimensionless expressions, which involve the pre-atmospheric meteoroid parameters, we have built physically based parametrisation to describe the changes in mass, height, velocity and luminosity of the object along its atmospheric path. The developed model is suitable to estimate a number of crucial unknown values including the shape change coefficient, ablation rate, and surviving meteorite mass. The model is also applicable in the prediction of the terminal height of the luminous portion of flight and therefore, the duration of the fireball. Besides the model description, we demonstrate its application using the wide range of observational data from meteorite-producing fireballs appearing annually (such as e.g. the Annama, Košice, Neuschwanstein and Osceola fireballs) to larger scale impacts (such as the Chelyabinsk, Sikhote-Alin and Tunguska event). In particular, this approach enabled us to successfully recover the Annama meteorite based on the analysis of the fireball observed by the Finnish Fireball Network on 19 April 2014.
The longest period Long Period Variables in the Magellanic Clouds
Groenewegen, Martin
There are thousands of Long Period Variables known in the Magellanic Clouds mainly due to microlensing surveys like MACHO, EROS and OGLE. However these variability surveys in the optical miss the reddest stars on the asymptotic giant branch as high mass-loss rates will obscure them. We have used the multi-epoch nature of the VISTA Magellanic Cloud (VMC) survey in the K-band in combination with literature data to look for very red AGB star variables. We discuss the results of this program that has revealed several stars with Mira-like amplitudes and periods beyond 1000 days.
On the nature and mass loss of Bulge OH/IR stars
Groenewegen, Martin
We report on the succesful search for CO (2-1) and (3-2) emission associated with OH/IR stars in the Galactic Bulge. We observed a sample of 8 extremely red AGB stars with the APEX telescope and detected seven. The sources were selected at sufficient high galactic latitude to avoid interference by interstellar CO, which hampered previous studies of inner galaxy stars._x005F To study the nature of our sample and the mass loss we used VizieR and further literature study to collect photometric data and Spitzer IRS spectroscopy to construct the SEDs. In a first step we apply radiative transfer modelling to fit the SEDs and obtain luminosities and dust mass loss rates (MLR). Through dynamical modelling we then retrieve the total MLR and the gas-to-dust ratios. We derived variability periods of our stars from the VVV and WISE surveys. The luminosities range between approximately 4,000 and 5,500 Lsun and periods are below 700 days. The total MLR ranges between 10-5 and 10-4 Msun/yr. Comparison with the Vassiliadis & Wood (1993) evolutionary models shows that the progenitor mass is approximately 1.5 Msun, similar to the Bulge Miras and are of intermediate age (3 Gyr). If more massive OH/IR stars are rare in the Bulge this may explain the scarcity of Bulge carbon stars. The gas-to-dust ratios are between 100 and 400 and are similar to what is found for OH/IR stars in the galactic Disk. We will discuss the nature of this OH/IR population in view of the inner Galaxy stellar populations._x005F One star, IRAS 17347-2319, has a very short period of approximately 300 days which may be decreasing further. It may belong to a class of Mira variables with a sudden change in period as observed in some Galactic objects. It would be the first example of an OH/IR star in this class and deserves further follow-up observations.
The colours of AGB stars in the JWST filters
Groenewegen, Martin
In Groenewegen & Sloan (2017) we have fitted the SEDs and IRS spectra of almost 400 AGB stars in the Magellanic Clouds and determined luminosity, dust mass-loss rate, and dust properties._x005F This sample covers essentially all phases of AGB evolutions, from low to extreme mass-loss rates and for oxygen-rich and carbon-rich chemistry._x005F As a by-product we calculated the synthetic magnitudes in essentially all filters of the various JWST instruments. This may be helpfull in understanding the observations of resolved stellar populations.
A Sequential Estimation Approach to Determining Terrestrial Reference Frames
Gross, Richard
The Jet Propulsion Laboratory (JPL) is pursuing an approach to determining ITRF-like terrestrial reference frames based upon the use of a Kalman filter/smoother. Kalman filters are commonly used to estimate the parameters of some system when a stochastic model of the system is available and when the data contain noise. For the purpose of determining a terrestrial reference frame, the system consists of the positions and velocities of geodetic observing stations and associated EOPs along with their full covariance matrices. The data consist of time series of observed VLBI, SLR, GNSS, and DORIS station positions and EOPs along with the data measurement covariance matrices. In addition, measurements from ground surveys of the positions of reference marks of co-located stations are used as constraints to tie the technique-specific measurements to each other. JPL's Kalman filter and smoother for reference frame determination (KALREF) combines these measurements to determine ITRF-like reference frames subject to constraints imposed on the allowed evolution of the station positions. KALREF includes options to model the station motion as linear, linear and annual, or linear, annual, and semiannual. Through the use of stochastic models for the process noise, the station positions can be constrained to follow these models of the station motion (by setting the process noise to zero), to recover the observed station positions (by setting the process noise to a large value), or to follow a smoothed path (by setting the process noise to some intermediate value). The sequential estimation approach to determining terrestrial reference frames that is being pursued at JPL will be described along with its use to determine JTRF2014, JPL's realization of a terrestrial reference frame using the ITRF2014 input data sets.
Tiny SXR solar flares observed by SphinX
Gryciuk, Magdalena
The Solar Photometer in X-rays (SphinX) was designed to observe soft X-ray solar emission in the energy range between ~1 keV and 15 keV with the resolution better than 0.5 keV. The instrument operated from February until November 2009 aboard CORONAS-Photon satellite, during the phase of exceptionally low minimum of solar activity. Despite a very low activity 1604 small X-ray events have been recognized by semi-automatic inspection of SphinX light curves. The SphinX Flare Catalogue not only contains the time of maximum occurance, but also other ?are characteristics. Results of the statistical analysis of the catalogue data are presented.
Meteor detection from the Fireball Moroccan Network: First orbital results and links to parent bodies
guennoun, meryem
We are about to develop in Morocco, several stations of observations supplied with two different types of cameras (All-Sky cameras and oriented watec cameras). Three All sky cameras are already installed respectively in Beni Mellal, Oukaimeden and Meknès, and two watec cameras are installed in Oukaimeden and Marrakech. We are planning to expand our Network by installing more cameras in many other locations in Moroccan territory. In this work, we are going to present orbital results of the watec double station. We computed the direction of these two cameras using the method of Rendtel et al. (2014). The aim of this project is to compute meteor trajectories and find a link to their parent bodies. Several parent bodies were linked to observed meteors, such as the comet « swift Tuttle » during Perseids observations on 2014 year. One similarity with the 252P/LINEAR comet was linked to one orbit in the Sonotaco 2009 meteor database. Here we present our first results.
The impact of flares and CMEs on planetary atmospheres
Guenther, Eike
Recent studies have shown that planets in the mass-range between 2 and 400 MEarth have a huge spread in densities. Even planets of the same mass can have very different densities. How can this diversity be explained? In the first 100 million years of their evolution, planets are exposed to strong EUV and X-ray (XUV) radiation from the host star. Observations, and theoretical models have shown that such radiation can lead to the erosion of planetary atmospheres. This process naturally explains the diversity of planets: Planets with atmospheres have low densities, planets without atmospheres have high densities. If this idea of atmospheric erosion were correct, it would have important consequences for the habitability of planets, since planets without atmospheres cannot be habitable. The erosion of planetary atmospheres is particularly important for potentially habitable planets of M-stars, because they orbit at very short distances from the host stars were the erosion is particularly strong. In recent years it became clear that the quiescent XUV-radiation is usually not strong enough to erode the atmospheres of planets completely. However, very little is known about the impact of flares and coronal-mass ejections (CMEs) on planetary atmospheres within the first 100 million years of their evolution. The situation is particularly difficult for CMEs, as only very few such events in young M-stars have been observed. Thanks to the new instrumentation, it is now possible to determine the flare-rate for young M-stars, and to study also the CMEs. Using data obtained with the Kepler satellite, we determine the statistics of flares of more than 100 M-stars with an age of 17 Myrs, and determine the power-law index of the flare-distribution. We also obtained more than 1000 high-resolution spectra of active M-star to study the properties of CMEs, and compare them with CMEs observed on the Sun.
The AMBRE Project: r-process element abundances in the Milky Way thin and thick discs
Guiglion, Guillaume
Chemical evolution of r-process elements in the Milky Way disc is still a matter of debate. We took advantage of high resolution HARPS/UVES/FEROS spectra from the ESO archive in order to derive precise chemical abundances of 3 r-process elements Eu, Dy & Gd and also Ba abundance, for more than 1000 stars. The chemical analysis has been performed thanks to the automatic optimization pipeline GAUGUIN. Based on the [alpha/Fe] ratio, we chemically characterized the thin and the thick discs. We present and discuss chemical abundance patterns of such elements in both discs.
When our Sun was Young: Coronal X-ray, TR-Chromospheric UV Emissions, Flares and Winds of the Young Sun (and solar-type stars) and Effects on Hosted planets.
Guinan, Edward
Studies of young solar proxies (G0-G5 V stars), as part of the ``Sun in Time'' program, show that the young Sun was rotating over ten times faster than today. As a consequence, these young sola -type stars (including the young Sun) had vigorous magnetic dynamos and correspondingly strong coronal X-ray and EUV emissions and chromospheric FUV and UV emissions - up to several hundred times stronger than that observed for the present Sun. Also, observations of the youngest solar proxies indicate that the young Sun had frequent and powerful flares and most likely significant winds. This paper is an update of the earlier studies by Ribas et al. (2005: ApJ.,622, 680; Guinan and Engle (2009: IAUS, 258, 395) with the addition of data from more recent stellar wind and flare studies (see Guinan and Engle 2015: IAUGA 2255511; Airapetian & Usmanov 2016: ApJ, 817L.,24; Pognan et al. 2018: arXiv180205153 and references therein). This study focuses the first ~4.5 billion years of the Sun’s post-PMS life and also applies to other solar-type stars.The recent results of the `Sun in Time'' program will be discussed that show the decline of solar X-UV fluxes, winds and flares with slower rotation and increasing age. The determination of the flare energies and frequencies and stellar winds based on recent studies are presented. We present our most recent Age-Rotation-Activity relations for solar-type stars that also can be used in the study of other solar-type stars with planets (e.g. tau Ceti). Also briefly discussed are some of the major effects that the young Sun's strong magnetic activity had on the photoionization, photochemistry, and erosion of paleo-planetary atmospheres as well as on the development of life on these planets.This research is supported by grants from NASA and NSF which we gratefully acknowledge.
Growing Plants on Mars - Mars Gardens in the University: Growing Vegetables in Martian regolith simulant.
Guinan, Edward
Over the next few decades NASA and private enterprise missions such as SpaceX-Mars plan to send human missions to Mars with the ultimate aim to establish a permanent human presence on this nearby planet. For a self-sustaining colony on Mars it will be necessary to provide food by growing plants in heated/sheltered greenhouses. As part of an undergraduate student project in Astrobiology at Villanova University, experiments are being carried out, testing how various plants grow in the Martian regolith (soil). The plants are being grown and tested in Mars regolith simulant commercially available from The Martian Garden (TheMartianGarden.com). This Mars regolith simulant is based on Mojave Mars Simulant (MMS) developed by NASA and JPL for the Mars Phoenix mission. The MMS is based on the iron-rich Mojave Saddleback basalt. Additional reagents were added to this iron-rich basalt to bring the chemical content close to the actual Martian regolith. It is ~90% similar to regolith found on the surface of Mars - excluding poisonous perchlorates commonly found on actual Mars surface. Since Mars is 1.52 a.u. from the Sun, the ambient surface solar light insolation is about ~43% Earth.A wide variety of plants and vegetable are being grown and tested. These include carrots, spinach, dandelions, kale, soy beans, peas, onions, garlic, peanuts, Jerusalem artichokes, and of course potatoes, and sweet potatoes. In Spring 2018 barley and hops have been planted in the MMS in larger quantities with the hope of making Martian beer. Also earthworms and red worms have been introduced to test their viability. The worm castings (excrement) will be used to enrich the Martian soil. The results of this project will be discussed from an educational viewpoint as well as from usefulness in Martian botany research.We thank the Dept. of Astrophysics and Planetary Science (Villanova University) for financial support and the Biology Department for the use of their campus greenhouse.
Hypothesis of the massive planet on the periphery of the Solar System
Guliyev, Rustam
The present work reviews selected aspects of the Guliyev's hypothesis about the massive celestial body at a distance of 250-400 AU from the Sun as well as the factor of comets transfer. It is shown, that the conjecture of the point around which cometary perihelia might be concentrated, is not consistent. On the issue of perihelia distribution, priority should be given to the assumption that there is a plane or planes around which the concentration takes place. The search engine for such planes was applied to numerous cometary groups, separated by clusters T (discover date), e, q, H (absolute magnitude), Q, 1/aori, etc. A total of 24 comet groups were investigated. In almost all cases there are detected two types of planes or zones: the first one is very close to the ecliptic, another one is about perpendicular to it and has the parameters: ip = 86°, Ωp = 271.7°. The existence of the first area appears to be related to the influence of giant planets. The Guliyev's hypothesis says that there is a massive perturber in the second zone, at a distance of 250-400 AU. It shows that number of aphelia and distant nodes of cometary orbits in this interval (within statistical confidence) significantly exceeds the expected background. On the basis of collected cometary data, we have estimated orbital elements of the hypothetical planetary body: a = 337 AU; e = 0.14; ω = 57°; Ω = 272.7°; i = 86° Naturally, each value may contain some errors. In order to test the stability of such an orbit, the planet was integrated for 10 million years, assuming that its mass is about 10 Earth masses. The orbits of 33 comets (having aphelia and distant nodes 286-388 AU) are also integrated in the past for a million years in order to trace possible dynamic relationship with the planet. In doing so, we varied the mean anomaly of the planet from 0° to 360° by 10° in each cycle of numerical explorations.
Multi-wavelength Variability and QPOs in Blazars
Gupta, Alok
In the present poster, I will summarize our recent results based on multi-wavelength variability and QPOs detection in blazars.
GENERAL FEATURES OF THE SOLAR CYCLE 24
Gursoy, Fulin
In this study, using the data of Istanbul University Observatory, general features of the Solar Cycle 24 are presented.
Zooming into the AGN properties with Space VLBI
Gurvits, Leonid
Investigation of the physics of the AGN phenomenon requires, among other methods, ultra-high angular resolution, offered in radio domain by Very Long Baseline Interferometry (VLBI). The extension of VLBI into space with baselines exceeding the Earth diameter offers the highest achievable today angular resolution reaching single-digit microarcseconds. The Space VLBI mission RadioAstron which operates in orbit since 2011 completed the observational part of its AGN Survey project in 2017. The Survey sample includes 247 sources observed at 5 and partially 1.6 GHz over the total of 2000 hours. The observations were conducted in the non-imaging mode at the baselines ranging from several to 27 Earth diameters; the latter, at 6 cm wavelength provides the angular resolution of ~30 uas. Importantly, since the ability of an interferometer to tackle the highest brightness temperatures requires the longest physical length of a baseline, the RadioAstron offers a unique opportunity to measure directly the brightness temperatures exceeding the value of 1011.5 K, dictated by the Inverse Compton “catastrophe”. Indeed, such the ultra-high brightness has bee detected in several AGN. The presentation will discuss these results and their possible implications for the physics of the radio emission mechanism in AGN. Another result of the RadioAstron AGN Survey project is a pioneering detection of refractive scattering of radio emission in the interstellar medium. This is a long predicated phenomenon with manifestations reachable only with baselines exceeding the Earth diameter. We will discuss how the presence of refractive scintillations might impact estimates of physical parameters of AGN.The RadioAstron AGN Survey data are being analysed in concurrence with several ground-based observing programmes in radio and other domains of the electromagnetic spectrum. The presentation will review the current status of the overall RadioAstron AGN Survey data analysis and its perspectives
Dust in Clusters: Separating the Contribution of Galaxies and Intracluster Media
Gutierrez, Carlos
Analyzing Herschel data for a large sample clusters of galaxies up to redshift 0.70 strong constraints ontheir mean intracluster emission of dust have been obtained; withina radius of 5 arcmin centered in each cluster, the 95% C.L. limits obtained are 86.6,48.2, and 30.9 mJy at the observed frequencies of 250, 350, and 500 micras. From theserestrictions, and assuming physical parameters typical of interstellar media in theMilky Way, we have obtained tight upper limits on the visual extinction of backgroundgalaxies due to the intracluster media (ICM): AV(95% C.L.) <~ 10^(-3) mag. Strongconstraints are also obtained for the mass of such dust; for instance, using the dataat 350 mum we establish a 95% upper limit of <10^9 Msun within a circle with aradius of 5 arcmin centered in the clusters. This corresponds to a fraction of thetotal mass of the clusters of 9.5 × 10^(-6), and indicates a deficiency in thegas-to-dust ratio in the ICM by about three orders of magnitude in relation to thevalue found in the Milky Way. Computing the total infrared luminosity of the clustersin three ranges of redshift (0.05-0.24, 0.24-0.42, and 0.42-0.71) and two ranges ofmass (<10^14 and >10^14 Msun), respectively, a strong evolution of luminosity inredshift (L ~ z^1.5) for both ranges of masses is found. The results indicate a strongdeclining in star formation rate with time in the last ~6 Gyr.
Analytical studies of the dynamics of High-velocity clouds in the galactic halo of disk galaxies
Guzman, Consuelo Leona
Galactic evolution is strongly determined by outflows of hot baryons and infall of mainly neutral baryons, such as high velocity clouds (HVCs), which have been observed for many decades in the halo of our Milky Way. To describe the dynamics of HVCs analytically, Benjamin and Danly (1997) have solved numerically the equation of motion of a spherical cloud under the influence of gravity and drag force. Thus, they have been able to derive the terminal velocity of HVCs falling onto the Galactic disk. Here we show that their equation of motion can be solved analytically, by pure quadrature, so that even for more complicated and realistic gravitational potentials their dynamical behaviour can be studied in detail. The results presented here include a Miyamoto Nagai (1975) potential and an extended version by Barros et al. (2016). We show how the velocity changes as a function of height (also calculating the terminal velocity), including the Bernoulli effect, which leads to a lateral expansion of the HVC and thus to an increased drag. For a cloud falling into a density stratified halo from a distance of 5 kpc, supersonic velocities are reached at a height of 2.26 kpc, resulting in the formation of a bow shock. Using the model of Schulreich and Breitschwerdt (2011) we also calculate its precise position, as well as all the post shock fluid variables such as pressure, density and velocity. These analytical results will be compared to observations of Milky Way halo clouds.
Circumstellar structures around high-mass X-ray binaries
Gvaramadze, Vasilii
Many high-mass X-ray binaries (HMXBs) are runaway systems, travelling through space with high velocities. Stellar wind and radiation of donor stars in HMXBs along with outflows and jets from accretors interact with the local interstellar medium and, under proper conditions, produce curious circumstellar structures. I will report the detection of several such structures and discuss their possible origin.
ETV analysis of OGLE-IV eclipsing binaries
Hajdu, Tamás
We report a comprehensive study of the eclipse timing variation (ETV) of short periodic (P1< 5d) eclipsing binaries (EB) derived from the photometric survey OGLE-IV. From the 450,000 EBs we selected approximately 9000 binaries which we found suitable for further examination. We sorted and analyzed the potential hierarchical triple candidates in an automatic manner and identified about half thousand systems which O-C diagrams show light-travel-time effect (LTTE). There are several studies about evolution of close binary systems however, if there is a further component it can significantly influence the orbital evolution of the inner components also in the early stage of their state. The large number of these potential candidate systems found by us makes it possible to do a meaningful statistical analysis of the outer orbit to understand better its effects on the close binaries. We found that (i) there is a significant lack of triple systems where the outer period is less than 400 days; (ii) in our sample of candidates there is no system with outer eccentricity higher than 0,8 , although such high eccentricity is not theoretically impossible; (iii) the distribution of the outer eccentricity has a maximum around e2=0,4.
How Pulses in Short Gamma-Ray Bursts Constrain HMXRB Evolution
Hakkila, Jon
We present evidence that pulses in Short gamma-ray bursts (GRBs) originate from collisions between relativistically-ejected shells and slower-moving media (external shocks) rather than from collisions between shells of relativistically-ejected material (internal shocks). Using GRB/GW 170817A as a canonical example of a dying HMXRB system, we discuss how GRB pulse characteristics constrain the kinematics and structures of shocked regions produced in merging neutron star systems.
Selection Biases and Gamma-Ray Burst Pulse Structure
Hakkila, Jon
Faint gamma-ray burst (GRB) pulses exhibit smoother, less structured light curves than bright GRB pulses. We demonstrate how low photon detection rates, noisy detectors, energy-dependent pulse characteristics, and temporal binning can all combine to smear out pre-existing complex pulse structures, converting them into the observed smooth triple-peaked pulse behavior. We then study bright GRB pulse light curves to avoid the biases, discovering that GRB pulses are characterized by time-symmetric emission structures overriding hard-to-soft spectral evolution. We describe how these observations greatly constrain GRB models.
Inferring Progenitor Stellar Properties from Gamma-Ray Burst Pulse Characteristics
Hakkila, Jon
Pulses are the dominant form of prompt emission in gamma-ray bursts (GRBs). They are found in Short GRBs (merging compact systems), Long GRBs (collapsars), and x-ray flares (GRB afterglows). GRB pulses are characterized by triple-peaked light curves that evolve from hard-to-soft, with re-hardening occurring at or near the time of each peak; they are indicative of shocked material in relativistically expanding systems. Despite these similarities, Short GRB pulses differ from Long GRB pulses and x-ray flares in that they have shorter durations, shorter inter-pulse separations, and undergo more pronounced and rapid hard-to-soft spectral evolution. We discuss how these properties can be used to constrain characteristics of the GRB progenitors.
Differentially rotating white dwarfs with 2DStars
Halabi, Ghina
The effect of stellar rotation is particularly interesting in accreting white dwarfs (WDs). Accreted material from a companion can transfer substantial angular momentum, thus spinning-up the WD [1]. Over five decades investigations [2,3] have shown that rapid rotation has a large influence on the stability of zero temperature WDs. Using 2DStars [4], a two-dimensional stellar evolution code, we investigate the evolution of the rotation profile on the nuclear time-scale of a rapidly differentially rotating cold WD [5,6]. The aim is to determine whether super-MChandrasekhar WDs can be brought into solid-body rotation due to the dissipative effects induced by the electron and turbulent viscosity, and explode as SNe Ia. We employ a fully relativistic equation of state for cold degenerate matter and start with an internal rotation profile that ensures sufficient differential rotation to avoid immediate collapse. _x005F _x005F References_x005F [1] Durisen R. H., 1977, ApJ, 213, 145_x005F [2] James R. A., 1964, ApJ, 140, 552_x005F [3] Ostriker J. P., Bodenheimer P., 1968, ApJ, 151, 1089 _x005F [4] Halabi, Izzard, Tout, Jermyn & Cannon, 2017, MmSAI, 88, 319H_x005F [5] Yoon S.-C., Langer N., 2004, A&A, 419, 623_x005F [6] Ghosh P., Wheeler J. C., 2017, ApJ, 834, 93
Stellar feedback powering star-forming complexes in the Magellanic Clouds
Hamann, Wolf-Rainer
Clustered populations of massive stars have a big impact on their environment. They can create large structures like supergiant shells (SGSs) and superbubbles of shocked, X-ray emitting gas. The formation of such structures is the direct result of stellar feedback from the massive stars via strong ionizing radiation, stellar winds, and supernovae.Only detailed spectroscopic studies of the massive-star population can reveal the mechanisms that power their environment. We performed exemplary studies on star-forming regions in the supergiant shell SMC-SGS1 in the Wing of the SMC and in the complex N206 in the LMC, which encloses an X-ray 'superbubble'.We obtained many hundreds of spectra with VLT FLAMES of the massive star populations associated with each of the two mentioned complexes. Quantitative spectroscopic analyses were performed with the Potsdam Wolf-Rayet (PoWR) model atmosphere code, yielding the stellar and stellar-wind parameters. The PoWR models then provide the ionizing flux and the mechanical feedback from each massive star. Based on the total stellar feedback, the energy budget of the complexes is quantified and discussed. The star formation history is reconstructed from the distribution of stellar ages.The talk is focusing on massive stellar populations at different metallicities, obviously undergoing different modes of current star formation. The talk will highlight the role of feedback for the evolution of these dwarf galaxies.
Abundance and kinematics of the CGM as observed with MUSE
Hamanowicz, Aleksandra
Galaxies are constantly fed by the diffuse material from the intergalactic medium through the Circum - Galactic Medium (CGM). Strong outflows form SN or AGN feedback expel the enriched material back to the CGM. The physical properties of the CGM are still poorly unknown: is it a multi-phase medium, how powerful are inflows and outflows and how much mass is carried away by the galactic winds? We can probe these vast gaseous haloes around galaxies by studying absorbers detected in the spectra of the background bright quasars. To understand the dynamics of the system we combine the physical properties from the absorption features with the broader view of the absorber’s host and its environment by emission diagnostics, using the IFU spectroscopy.To address these questions we are studying a sample of absorber – quasar pairs with MUSE. In this talk I will present some preliminary results of this program, in particular focusing on the studies of the gas kinematics and metallicity and the general CGM properties of the quasar absorbers host galaxies, which in turn can help better constrain galaxy evolution models.
Hot Jupiters from Alternative High-eccentricity Migration Scenarios
Hamers, Adrian
One of the proposed formation origins of hot Jupiters (HJs) is high-eccentricity (high-e) migration. In high-e migration, the eccentricity of the orbit of a planet initially beyond the ice line is dynamically excited, leading to strong tidal dissipation occurring near periapsis and eventually resulting in a tight orbit. Previously studied secular variants of high-e migration involve an inclined and/or eccentric binary companion (star or massive planet). However, the predicted formation rates are too low compared to observations, by a factor of ~ 10. Therefore, alternative scenarios are needed. Recently, an alternative scenario was proposed by Lithwick & Wu involving secular chaos with three or more planets. This scenario can potentially produce many HJs because the initial conditions to achieve high eccentricities are less stringent compared to the case of an inclined binary companion. Until recently, studies of this scenario were limited to small phase space due to the prohibitive nature of direct N-body integrations. Here, we present a new secular method to study the long-term dynamics of hierarchical systems composed of nested orbits, with an arbitrary number of bodies and structure. We use this method to study the formation of HJs driven by secular chaos in multiplanet systems. Also, we consider scenarios in which HJs are formed through high-e migration in stellar triple systems, and discuss how secular evolution suggests the presence of unseen planetary companions to hot Jupiters in stellar binaries.
Galactic forces rule dynamics of Milky Way dwarf galaxies
Hammer, Francois
Dwarf galaxies populating the Galactic halo are assumed to host the largest fractions of dark matter,as calculated from their velocity dispersions. Their major axes are preferentially aligned with the VastPolar Structure (VPOS) that is perpendicular to the Galactic disk, and we find their velocity gradientsaligned as well. It suggests that tidal forces exerted by the Milky Way are distorting dwarf galaxies.Here we demonstrate on the basis of the impulse approximation that the Galactic gravitational accelerationinduces the dwarf line-of-sight velocity dispersion, which is also evidenced by strong dependencesbetween both quantities. Since this result is valid for any dwarf mass value, it implies that dark matterestimate in Milky Way dwarfs cannot be deduced from the product of their radius by the square oftheir line-of-sight velocity dispersion. This questions the high dark-matter fractions reported for theseevanescent systems, and the universally adopted total-to-stellar mass relationship in the dwarf regime.It suggests that many dwarfs are at their first passage and are dissolving into the Galactic halo. Itopens a promising way to estimate the Milky Way total mass profile at large distances.
Heavy puzzle pieces: Learning about the i process from Pb abundances
Hampel, Melanie
The large majority of elements heavier than iron are formed by the slow (s) and rapid (r) neutron capture processes. However, it has become clear that a neutron capture process operating at neutron densities intermediate to the s and r process (i process) gives rise to its own characteristic abundance pattern. This i-process pattern is successful at reproducing observed heavy-element abundances that could not be explained previously, e.g. those of carbon-enhanced metal-poor stars that show enrichments of s- and r-process elements (CEMP-s/r). The required high neutron densities may occur in the thermal pulses of Asymptotic Giant Branch (AGB) stars as a result of proton ingestion episodes. However, the sites of the i process are as yet unknown.Comparing theoretical predictions of i-process nucleosynthesis with the observed abundance patterns of CEMP stars and post-AGB stars in the Magellanic Clouds allows us to learn about the thermodynamic properties of possible i-process sites. In particular the Pb abundances may hold the key to solving this mystery because this is one element that is predicted to be significantly enhanced by the s process at low metallicities, in contrast to observations of post-AGB stars which only show low to moderate Pb enhancements. In this talk I will present the results of nuclear-network calculations of i-process nucleosynthesis in comparison to observations.
Spatial distributions of different metallicity groups in red giant branch of dwarf spheroidal galaxies
Han, Sang-Il
The Ca-by photometry of Galactic three dwarf spheroidal galaxies (Draco, Sextans, and Canes Venatici I) obtained from Subaru/Suprime-Cam is presented to study spatial distributions of the red giant branch (RGB) stars according to the metallicity. Due to the sensitivity of the Ca filter to the metallicity, metal abundance of the redder RGB stars in the hk index [=(Ca-b)-(b-y)] are larger than that of the bluer RGB stars and the width of the RGB in the hk index is broader than other colors. We show that the metallicity is correlated with the hk index from the comparison with theoretical isochrones as well as the spectroscopic data in the literature. This suggests that this index can serve as an alternative metallicity indicator and allow us to study the structural feature of different metallicity groups of stars for the relatively larger sample compared to spectroscopy. We present the spatial structure of metal-rich and metal-poor RGB groups defined from the hk index and discuss chemo-structural complexities in the context of dwarf galaxy formation theories.
Professional- Amateur Collaboration in the Scientific Observations of Total Solar Eclipses
Hanaoka, Yoichiro
Professional solar scientists and amateur astronomers in Japan have been energetically collaborated in the observation of the total solar eclipses in the last ten years. The collaboration has been producing scientific results, which have been published in scientific papers. The observation of the total eclipses has some advantages to let amateurs participate in as follows._x005F - The observation can be done with small telescopes._x005F - The multipoint observation can be realized. It helps to avoid the risk of the weather, and also enables to track the temporal variation of the corona_x005F - Wide range of amateurs, not only experienced ones but also beginners for the eclipse observation can contribute._x005F Therefore, the observation of the total eclipses is one of the most suitable targets to promote the participation of amateurs in scientific observations. Furthermore, because the astronomers from various nations gather to observe eclipses, it is expected that the more extensive collaboration is promoted by an international organization such as IAU. We will present our collaborative activities so far in our poster, and we would like to contribute to extending such activities.
Fragmentation of Filamentary Cloud Permeated by Perpendicular Magnetic Field
Hanawa, Tomoyuki
We examine the linear stability of a filamentary cloud permeated by a perpendicular magnetic field._x005F The model cloud is assumed to have a Plummer-like profile and to be supported against the self gravity_x005F by turbulence. The effects of turbulence is taken into account by enhancing effective pressure_x005F of a low density gas. We derive the effective pressure as a function of the density from the condition of the hydrostatic balance. When the radial density profile is broader, i.e., the index is smaller, the model cloud is more unstable against radial collapse. When the magnetic field is mildly strong, the radial collapse is suppressed. If the displacement vanishes in the region very far from_x005F the cloud axis, the model cloud is stabilized completely by mildly strong magnetic field. _x005F If the rearrangement of the magnetic flux tubes is permitted, the model cloud is unstable even_x005F when the magnetic field is extremely strong. The stability depends on the outer boundary condition. _x005F The growth rate of the rearrangement mode is smaller for a lower index. We also discuss the case when the initial magnetic field is oblique to the cloud axis.
Difference of the Gas Density Histograms in and out of spiral arms in Milky Way Galaxy
Handa, Toshihiro
Stars are formed from dense gas cores through the gravitational collapse. Before this stage less dense gas must be compressed and becomes denser. However, its mechanism is not clear. For example, Kennicutt-Schumidt law shows a correlation between amount of low density molecular gas traced by 12CO and star forming activity in a galactic scale, which means there should be some global relation between diffuse and dense gases. This is a way to understand “cosmic recycling of matter” completely. To address this issue directly we should investigate the density structure of the interstellar matter (ISM) in the galactic scale. Until now many investigators have focused on the spatial structure of ISM such as the core mass function. However, we make a statistical investigation, which ignores the local structure of ISM itself. This is another approach on the density structure. We call it “Gas Density Histogram (GDH)”, which is an observational counterpart of the probability density function (PDF) of the gas density of ISM if gas density structure is steady. We use “FOREST unbiased galactic imaging survey with Nobeyama 45-m telescope” (FUGIN), which is a large coverage survey in 12CO (1-0), 13CO (1-0), and C18O (1-0) with 15” resolution. Using the method of the kinetic distance estimation, we can also estimate the line-of-sight depth for each l-b-v voxel. Therefore, we can estimate the volume density of the voxel from the observed column density. The resultant GDHs show different shape from place to place in the Milky Way Galaxy; GDHs of the inter-arm regions show log-normal or similar to log-normal, but those in the spiral arm regions show log-normal with a bump in higher density or flat-top.
Probing the Solar Interior with Computational Helioseismology
Hanson, Chris
Despite the numerous successes of helioseismology, our ability to effectively image the deep convective interior of the Sun is still lacking. This is due to both a lack of understanding of the observations (e.g., center-to-limb effect) and underdeveloped modelling (e.g., accurate sensitivity maps of wave travel times shifts due to flows). Understanding the sensitivity of the observables (travel times, ring fits, holograms, etc.) due to flows requires excellent models of acoustic wave propagation within the solar medium and of the various sources of noise. In this talk we will present a computational approach to modelling numerous flow structures in the solar interior (e.g. meridional flow and supergranulation), exploring the sensitivity of observables to different models. We show that these flow structures can be recovered from the observables (the inverse problem), by enforcing mass-conservation through classical inversion techniques and machine learning.
A numerical investigation into the observable spin parameter
Harborne, Katherine
The observable spin parameter, λR, gives us a quantitative way to distinguish galaxy types according to how fast they rotate. This value is used quite frequently in many observational IFU studies. However, observations are always a 2-dimensional projection of a 3-dimensional object, which prompts the question – how well do the observed galaxy properties map to the true kinematic features?_x005F I have been developing a code to analyse numerical simulations of isolated galaxies, observing them as if using an integral field spectrograph, such as SAMI or MaNGA. The aim of this work is to quantify the levels of uncertainty in the spin parameter introduced by projection effects, beam smearing and measurement radius. As we have the original galaxy simulation, the modelled effects can be quantified for a range of galaxy structures by comparing the mock observables to the analytic form. Here, I will present the results of this work and introduce the code that has been developed, SimSpin.
Census of Lya, [OIII]5007, Ha, and [CII]158um Line Emission with ~1000 Low-mass Lyman Alpha Emitters at z=4.9-7.0 Revealed with Subaru/Hyper-Suprime Cam Survey
Harikane, Yuichi
We investigate Lya, [OIII]5007, Ha, and [CII]158um emission from 1,125 low-mass galaxies (typically M*~10^8 Mo) at z=4.9-7.0, composed of 1,098 Lya emitters (LAEs) at z=4.9-7.0 identified by Subaru/Hyper Suprime-Cam (HSC) narrowband surveys and 29 galaxies at z=5.148-7.508 with deep ALMA [CII]158um data in the literature. Fluxes of strong rest-frame optical emission lines ([OIII] and Ha) are constrained by significant excesses found in the Spitzer 3.6 and 4.5um photometry. At z=4.9, we find that the rest-frame Ha equivalent width and the Lya escape fraction positively correlate with the rest-frame Lya equivalent width, EW^0_Lya. The typical ionizing photon production efficiency of LAEs is logxi_ion/[Hz erg^-1]~25.5, significantly (60-100%) higher than those of LBGs at a given UV magnitude, indicating the significant role of these low-mass galaxies in the cosmic reionization. At z=5.7-7.0, there exists an interesting turn-over trend that the [OIII]/Ha flux ratio increases in EW^0_Lya~0-30 A, and then decreases out to EW^0_Lya~130 A. We also identify a ~3sigma negative correlation between a [CII] luminosity to star-formation rate ratio (L_[CII]/SFR) and EW^0_Lya. We carefully investigate physical origins of these relations with stellar-synthesis and photoionization models, and find that a simple anti-correlation between EW^0_Lya and metallicity explains self-consistently all of the relations of Lya, Ha, [OIII]/Ha, and [CII] identified in our study, indicative of the detections of the very metal-poor (~0.04 Zo) low-mass galaxies with EW^0_Lya~200 A.
Wikipedia for Astronomy: Improving a global resource for education and outreach
Harris, Hannah
Wikipedia is a common reference for students, scientists, the public, and anyone interested in astronomy. Due to its ubiquity when searching for information online, it is often the first resource a curious reader will encounter. Accurate astronomy-related content on Wikipedia enriches public understanding of astronomy, supports factual science journalism, and provides quality astronomy information in diverse languages. For astronomers, communicators, and educators, it matters what astronomical information is on Wikipedia, and whether or not that information is accurate and understandable. This poster summarizes the current state of astronomy on Wikipedia and how that information can be improved.
Kepler K2: A Search for Very Red Stellar Objects
Hartig, Erich
Continuing the analysis of Long Period Variables (LPVs) observed as part of the Kepler K2 mission we show the latest results. We found that the 'Kepler K2 High Level Science Product' (K2HLSP) 'Self-Flat-Field' method (K2SFF or SFF) corrected the instrumental effects best. An iterative fitting method using sinusoidal functions was developed and evaluated.Furthermore, we present a strategy to properly constrain periods longer than the observational time basis using rms-error minimization. To check the results of this method, we applied it to a 33 d long dataset (1560 data points) of EP 202070273 (Kepler K2 Campaign 0) for which a ground based period of 730 d is available. The output from our method, 763 d, is in excellent agreement.From the Kepler K2 Campaign 2 we analysed a total of 41 targets data that are suspected or known LPVs. The 77.48 d of observations provided roughly 3500 data points. We searched for the SFF sinusoidal fit at the global rms-minimum and compared the periods with the available ASAS periods. In this way we defined the error range which could be applied to the rest of the targets.The preliminary results are presented in the poster.
Dwarf Galaxies in the core of Coma Cluster
Hasan, Syed
Dwarf galaxies constitute 24% of the galaxies in the core of the Coma Cluster. In this talk, I present the correlation between structural properties and morphology of galaxies in the central region of Coma Cluster for 221 objects within the apparent magnitude range m < 19.5. The data is taken from the HST/ACS Coma Cluster Treasury Survey and Source Extractor Catalogue compiled by Hammer et. al. 2010. For cluster membership we have used photometric redshifts of Michard et. al. 2008 & Edwards et. al.,2002 and spectroscopic redshifts of SDSS DR9 catalog. From the investigation of correlations of effective radius, Sersic index, absolute magnitude and bulge to total light ratio, we find that giants constitute 73%, Dwarf galaxies constitute 24% and the remaining 3% are Spirals+Irr+Ring. We found that multiple component fits are best for giants and the single Sersic fit is best for Dwarfs & Spiral galaxies. We shall try to explain why the single Sersic fit is best for Dwarfs and what kind of stellar orbits do they correspond to.
A physically motivated dense-core extraction technique applied to Herschel/Planck observations
Hasenberger, Birgit
The evolution of dense cores in molecular clouds represents the earliest stage in the formation process of stars and planets. We are able to observe this stage by using multi-wavelength observations in the far-infrared and sub-mm range, which allow us to map nearby molecular cloud complexes in their entirety and resolve the core population embedded within them. However, the lack of a physically motivated definition of dense cores resulted in the development of a variety of algorithms designed to extract cores from observational data. In the most commonly used algorithms, core boundaries are based on the two-dimensional morphology of structures in the available maps, rendering the physical interpretation of results challenging. In addition, comparisons between studies of core samples are inherently problematic if different core extraction methods are employed.I will present a new method to define core boundaries observationally, based on the physical properties of the material in a molecular cloud. We model the flux distribution along the line of sight by taking into account the extent of structures on the plane of the sky. Subsequently, we can estimate the energy budget of cloud material in terms of its gravitational and thermal energy. The balance between these two contributions defines the boundaries of our cores. We illustrate the advantages and caveats associated with this approach by applying it to observations of the Pipe nebula by the Herschel and Planck satellites. We study in detail the derived core properties of this cloud, in particular the distribution of core masses.With this tool at hand, we are able to consistently define core samples in nearby molecular clouds, allowing us to compare core properties within individual clouds as well as between clouds. The development of a physically motivated core extraction algorithm thus represents an essential first step towards a deeper understanding of the processes involved in star formation.
Dwarf Galaxies and Cluster Environments
Hashimoto, Yasuhiro
We report an investigation of the properties of dwarf galaxies (Mr < -15) inside 26 clusters at z=0.15-0.25, using optical images taken with 34' x 27' field-of-view Subaru Suprime-Cam and the X-ray data from the Chandra archive._x005F Our goal is to help understand the relationship between the dwarf and giant galaxies, and between the dwarfs and their host clusters to eventually address a question of the formation and co-evolution of galaxies and their environments._x005F Our results include:_x005F 1. Investigation of the dwarf galaxy density distribution is sensitive to the background galaxies and the choice of colour selection of galaxies._x005F 2. Under-estimating of the background galaxy counts tends to mimic a `flat' distribution of dwarf galaxies over cluster-centric distance. _x005F 3. Approximately 40 - 60% of faint galaxies always remain undetected by the detection algorithm near the center of clusters, even after carefully treating the halo or extra diffuse light created by bright galaxies. The number of 'undetected' faint galaxies varies significantly from cluster to cluster, and even from pointing to pointing. Meanwhile, the distribution of blue (more than 0.3 bluer than cluster red sequence V-I colour) dwarf galaxies extends more to the outside_x005F 4. Dwarf galaxies extend up to 2 Mpc from the center in most clusters. Meanwhile, the distribution of blue (more than 0.3 bluer than cluster red sequence V-I colour) dwarf galaxies extends more to the outside compared to red dwarf galaxies._x005F 5. For a given colour, the spatial distributions of dwarf galaxies and giant galaxies become similar, once the accurate background correction is applied. Namely, the major contribution to the difference in the radial distribution comes from the colour, rather than the size, of galaxies._x005F 6. Relative to the NFW profile, all of the galaxy populations are showing a deficit near the cluster core (r < 0.3 Mpc). The deviation is the most significant for blue dwarf galaxies.
Space Weather on the Surface of Mars: Impact of the September 2017 Events
HASSLER, Donald M.
Although solar activity is declining as the Sun approaches solar minimum, a series of large solar storms occurred in September 2017 that impacted both Earth and Mars. This was the largest event seen on the surface of Mars since the landing of the Mars Science Laboratory (MSL) in 2012, and was also observed as GLE72 on Earth, making it the first event observed to produce a Ground Level Enhancement (GLE) on 2 planets at the same time! Due to the modulating effect of the Martian atmosphere and the magnetic cloud associated with the Coronal Mass Ejection (CME), the structure and intensity of the spectra observed at the surface are complex. We present the observations of this event obtained with the Radiation Assessment Detector (RAD) on MSL and discuss the implications for our understanding of such events and for mitigating the risk of space radiation and space weather for future human exploration.
Bridging the Gap of How One Feels about Large Facilities
Hayashi, Saeko
When you share common interest, you get friends. When you share common concerns, you become friends. When you sit together, you get better understandings. Even with people who have different views, we can work things out. That is what I believe, even when faced with strong oppositions against a proposal for a large facility to be built outside of my own country. And this is what I experienced – sitting in the same room, embrace the opportunity to face each other, I did find the overall concept is common._x005F Then how can we build common “ground”? The key is embedded in how we view the long -term future. Sometimes you encounter this argument, “not in my backyard” about the construction of big buildings or facilities. Then if the new project does not come to one’s neighborhood, that situation might lead to the loss of the livelihood there. I would like to discuss examples I witnessed which helped interactions between groups of opposite views. I do not have the desired outcome yet, but I believe the mutual understandings is one important key to make it come.
The Star-Formation History of the Early Universe as Revealed by Blind Searches for Far-infrared Emission Lines
Hayatsu, Natsuki H.
Using blind line searches to understand the cosmic star-formation history is one of the strategies that will be pursued by next-generation millimetre/sub-millimetre single-dish telescopes which will have high sensitivity and mapping speed. Before moving into such a new era, it is essential to develop a method to efficiently detect faint line-emitting sources whilst considering the completeness of source detection and contamination by false detections. Furthermore, in order to propose robust strategies for blind line searching, it is necessary to know to what extent we can constrain the luminosity function using existing ALMA archival data.In this presentation, we report the current status of tests using a blind line-searching method and show preliminary results using ALMA archival data. We discuss the detectability of line-emitting sources with various properties, e.g. peak flux, line width and spatial size, by injecting artificial sources into the ALMA data. To be as realistic as possible, this is done in the visibility plane, and we also investigate the effect of non-Gaussian noise. We compare the performance of the following three methods: (1) clump-finding and smoothing, (2) matched-filter analysis and (3) Bayesian analysis.We plan to apply our final results to various science cases for future observations, e.g. cross-checking the luminosity density using an intensity-mapping technique or estimating the redshift evolution of ionisation state or metallicity by combining with JWST or SPICA data. We plan to release our code as a CASA task.
Galactic Simulations of r-process Elemental Abundances
Haynes, Chris
We present the results of chemodynamical simulations with the inclusion of four different neutron capture processes: magneto-rotational supernovae, neutron star mergers, neutrino driven winds and electron capture supernovae. We examine both simple isolated gas discs and cosmological zoom-in simulations of a Milky way-type galaxy and compare the [Eu/Fe] and [Eu/O] evolution with recent observations, including the HERMES-GALAH survey. We find that neither electron capture supernovae or neutrino driven winds are able to adequately produce neutron capture elements to match observations. Both neutron star mergers and magneto-rotational supernovae are able to produce the elements in sufficient quantities; additionally we find that the scatter in [Eu/Fe] at low metallicity ([Fe/H] < -1) and the [Eu/O] slope at high metallicity ([Fe/H] > -1) give an important constraint on the r-process sites. Using these we predict that neither neutron star mergers or magneto-rotational supernovae are able to explain the observed europium abundances separately and can better match observations with a significant contribution from both.
Disentangling radio galaxy magnetism with the QUOCKA Survey
Heald, George
I will introduce the QUOCKA survey: QU Observations at Cm wavelength and Km baselines with the ATCA (Australia Telescope Compact Array). The aim of the QUOCKA survey is to provide a gold-standard set of broadband radio polarization spectra for active galactic nuclei (AGN) in the southern sky. QUOCKA will build on, and complement, the ASKAP POSSUM survey via targeted full-polarization imaging observations covering the 1-8 GHz range. The primary science goals are to: (i) characterise the internal magnetic field and plasma structure of radio lobes, jets, and their environments from exquisite broadband linear polarization spectra; and (ii) perform the first large-scale search for and characterisation of broadband circular polarization from radio galaxies. QUOCKA observations begin in mid-2018 with an initial sample of 250 radio galaxies selected from ASKAP Early Science fields. I will summarise the observational progress, demonstrate the data quality, and present initial results from the survey.
Disentangling radio galaxy magnetism with the QUOCKA Survey
Heald, George
I will introduce the QUOCKA survey: QU Observations at Cm wavelength and Km baselines with the ATCA (Australia Telescope Compact Array). The aim of the QUOCKA survey is to provide a gold-standard set of broadband radio polarization spectra for active galactic nuclei (AGN) in the southern sky. QUOCKA will build on, and complement, the ASKAP POSSUM survey via targeted full-polarization imaging observations covering the 1-8 GHz range. The primary science goals are to: (i) characterise the internal magnetic field and plasma structure of radio lobes, jets, and their environments from exquisite broadband linear polarization spectra; and (ii) perform the first large-scale search for and characterisation of broadband circular polarization from radio galaxies. QUOCKA observations begin in mid-2018 with an initial sample of 250 radio galaxies selected from ASKAP Early Science fields. I will summarise the observational progress, demonstrate the data quality, and present initial results from the survey.
IAU National Outreach Contact: Sri Lanka – Activities and Challenges
Heenatigala, Thilina
The IAU National Outreach Contacts (NOC) network was established in 2013 with the purpose of centralising global outreach efforts and to empower local representation. The IAU Office for Astronomy Outreach (OAO) acts as the central coordination point of the NOC network to support the projects at a national level.IAU NOC Sri Lanka is actively engaged in activities and spent time at the IAU OAO office at the National Observatory of Japan in Mitaka to strengthen the collaboration and to support projects. Like many nations, Sri Lanka has quite a few amateur and school based astronomical societies in several parts of the country. But currently there’s no research level astronomy or degrees at private or governmental institutions. However, there are currently about 10-15 professional astronomers from Sri Lanka working abroad and about 5 students pursuing astronomy for higher studies. In recent years, with the support of NOC, students could participate in IAU’s International School for Young Astronomers, International Space University, and other courses. While there’s a large interest in astronomy among public and students, there are quite a lot of challenges from traditional superstitious, astrology, and lack of options for higher studies in astronomy.This poster highlights the current astronomy activities of Sri Lanka, some of the major achievements and challenges the country face in further the astronomy education and research.
Standardising Teacher Training with 10 Years of Lessons from Galileo Teacher Training Programme
Heenatigala, Thilina
The Galileo Teacher Training Programme was launched in 2009 as a Cornerstone project of the International Year of Astronomy 2009 (IYA2009). The core concept of the programme is to train teachers around the world and to better equip them with right resources and knowledge to use astronomy as a tool in the classroom.During the almost 10 years of the period, the GTTP has trained and certified 20, 000 teachers around the world, while the programme has reached a total of more than 50, 000 teachers. The host organisation of GTTP, the Núcleo Interactivo de Astronomia (NUCLIO) alone has trained and certified about 5, 000 teachers in Portugal, while reaching about 10, 000. GTTP has trained teachers in collaboration with European funded projects; Discover the COSMOS, Inspiring Science Education, Go-Lab, Space Awareness, among others bringing the latest trends, tools and evaluation in teacher training in astronomy education. The programme has also collaborated with major partner organisations such as Global Hands-on Universe, European Space Agency, European Science Education Academy and Leiden University to create interdisciplinary training events.Combining these lessons learnt, evaluation and experience from the past decade, the programme will build a competency profile for teacher training in astronomy to be used in IAU activities in training teachers, OAD funded projects, OAO network, and affiliated projects. The core competencies will include developing, implementing, organising, and evaluating of teaching STEAM subjects using astronomy as a tool. The new GTTP methodology will represent the 21st-century skills for teachers as well as produce the highest quality of content reviewed by experts in the field. The characteristics of the competency profile will align and complement the framework of IAU strategic plan 2020-2030.
A detailed view of the tailed radio galaxy 3C 31 with LOFAR
Heesen, Volker
We present a deep, low-frequency radio continuum study of the nearby Fanaroff–Riley class I (FR I) radio galaxy 3C 31 using a combination of Low-Frequency Array (LOFAR; 30–85 and 115–178 MHz), Very Large Array (VLA; 290–420 MHz), Westerbork Synthesis Radio Telescope (WSRT; 609 MHz) and Giant Metre Radio Telescope (GMRT; 615 MHz) observations. Our new LOFAR 145-MHz map shows that 3C 31 has a largest physical size of 1.1 Mpc in projection, which means 3C 31 now falls in the class of giant radio galaxies. We model the radio continuum intensities with advective cosmic ray transport, evolving the cosmic ray electron population and magnetic field strength in the tails as functions of distance to the nucleus. For this we use models from SPINNAKER, the SPectral INdex Numerical Analysis of K(c)osmic-ray Electron Radio-emission, which is a computer program that calculates non-thermal radio spectral indices for 1D cosmic ray transport of pure advection and diffusion. We find that if there is no in situ particle acceleration in the tails, then decelerating flows are required that depend on radius r as v ~ r^beta (beta = -1). This then compensates for the strong adiabatic losses due to the lateral expansion of the tails. We are able to find self-consistent solutions in agreement with the entrainment model of Croston & Hardcastle, where the magnetic field provides ~1/3 of the pressure needed for equilibrium with the surrounding intracluster medium. We obtain an advective time-scale of ~190 Myr, which, if equated to the source age, would require an average expansion Mach number M ~ 5 over the source lifetime. Dynamical arguments suggest that instead either the outer tail material does not represent the oldest jet plasma or else the particle ages are underestimated due to the effects of particle acceleration on large scales. Hence, LOFAR reveals entirely unknown parts in one of the best-studied radio galaxies that are invisible at GHz-frequencies due to spectral ageing.
Galactic winds in nearby galaxies traced with radio continuum observations
Heesen, Volker
Galactic winds driven by cosmic rays (CRs) have since long been suspected to be an important ingredient in the evolution of galaxies, however, they have been proven elusive to detect observationally. This is possibly now about to change with the advent of sensitive low-frequency observations such as with the Low-Frequency Array (LOFAR), allowing us to see CR electrons far away from star-formation sites. They can be combined with new broadband, high-frequency observations such as with the refurbished Very Large Array (VLA), in order to study spatially resolved radio continuum spectra at matched angular resolution and sensitivity. On the modelling side there has been progress as well, both with numerical 3D simulations incorporating CR transport as well as with 1D semi-analytical models of CR-driven winds and of pure CR advection and diffusion. Here, we present results from our survey of nearby late-type spiral edge-on galaxies using archival data from a wide range of radio interferometers and single-dish telescopes as well as new observations at 140-MHz with LOFAR and 1.5- and 6-GHz observations from the CHANG-ES (Continuum Halos in Nearby Galaxies – an EVLA Survey) survey to explore the vertical CR transport in radio haloes. Early results are promising, with two types of haloes emerging: either they can be described as diffusion dominated, with diffusion coefficients in fair agreement with the Milky Way value, or they are advection dominated, with advection speeds within a factor of two in agreement with the escape velocity near the galactic mid-plane. This raises the possibility that winds are common in star-forming galaxies; they are visible as radio haloes extending over the entire disc and are related to processes connected to star formation. More work needed to better understand the relationship between cosmic rays and magnetic fields with other halo constituents such as the warm neutral, warm ionised, and hot ionised medium.
SPINNAKER - The SPectral INdex Numerical Analysis of K(c)osmic-ray Electron Radio-emission
Heesen, Volker
We present SPINNAKER, the SPectral INdex Numerical Analysis of K(c)osmic-ray Electron Radio-emission. This computer program calculates non-thermal radio spectral indices for 1D cosmic ray transport of pure advection and diffusion, which can be applied to vertical intensity profiles in the haloes of edge-on galaxies. We show that advection and diffusion lead to differently shaped radio spectral index profiles, with advection resulting in a linearly steepening radio spectral index with increasing distance from the star-forming mid-plane, while diffusion leads to a more parabolical shape where the steepening occurs only at heights 1-2 kpc above the disc. Corresponding intensity profiles for exponential magnetic field distributions are exponential for advection and more Gaussian for diffusion. Our radio continuum survey of nearby edge-on galaxies using new and archival data from the radio interferometers Australia Compact Array Telescope (ATCA), Very Large Array (VLA), Westerbork Synthesis Radio Telescope (WSRT) and from the 100-m Effelsberg and 64-m Parkes single-dish telecopes shows examples for both cases. Thus, galaxies can be either described as advection dominated, where advection speeds agree within a factor of two with the escape velocity near the galactic mid-plane, or they are diffusion dominated, where the diffusion coefficients are in good agreement with the Milky Way value. Hence, the study of vertical radio spectral index profiles in galaxies is helpful in many ways, especially to detect galactic winds; they are visible as radio haloes extending over the entire disc and are related to processes connected to star formation. SPINNAKER and the Python graphical user interface (GUI) for it, Spinteractive, are free to download. Spinteractive allows the user to interactively fit advection and diffusion models to vertical intensity profiles, but also incorporates an automatic search for the best-fitting parameters.
3C 294 revisited
Heidt, Jochen
3C 294 is a powerful FR II radio galaxy at z = 1.786 dominated by a Z-shaped structure with a relatively weak core at 6cm. The galaxy is associated with a large cloud of ionized gas aligned with the inner part of the radio structure. Due to its proximity to a bright 11th mag star it is an ideal target for observations with modern AO-systems. Previous AO-observations of 3C 294 have resolved this source in several subclumps perhaps in the process of merging. This is supported by an apparent overdensity of faint red galaxies in its vicinity. On the other hand, there are claims that 3C 294 consists of two active nuclei separated by a few kpc based on proper astrometry and acomparison with high-resolution X-ray data. Thus its evolutionary state and structure is complex and not yet fully understood. The findings described above are based on observations more than 15 years ago. Since then the AO-systems have become more advanced and the detectors more sensitive allowing observations of this sourcewith much better contrast and sensitivity than before. In this contribution we present and discuss a new data set of 3C 294 taken at the Large Binocular Telescope. In particular, we secured deep diffraction-limited JHK-images of 3C 294 accompanied by high-resolution (0.5" FWHM) JHK-images of its large-scale environment.The data set is complemented by deep optical spectra to search for signatures of a dual AGN.
X-raying the clumpy stellar wind in the high-mass X-ray binary Cyg X-1
Hell, Natalie
Supermassive O/B-type stars exhibit strong stellar winds. Due to instabilities the hot wind material is prone to fragment into clumps of colder and denser material. The detailed structure of the wind and the clump morphology are still not well understood. In high-mass X-ray binaries (HMXBs), where these stars are paired with a compact object, the interaction with the compact object alters the wind structure further.Cyg X-1 is a persistent black hole HMXB with a supergiant O9.7Iab type star whose strong stellar wind is focused onto the black hole. The black hole is powered by accretion of the clumpy wind and the resulting continuum radiation is a perfect backlighter to X-ray and study the properties of the focused stellar wind. As the clumps pass our line of sight to the black hole, they cause excess absorption visible as dips in the observed X-ray lightcurves. The absorbing material imprints characteristic spectral signatures onto the continuum radiation from the black hole, depending on density, temperature, ion content (including a wide range of charge states), and velocity of the material. High-resolution spectroscopy enables us to use plasma diagnostics of Doppler shifts and line ratios of these signatures to determine the properties of the absorbing material. Analysing and comparing these high-resolution spectra at periods of different absorption levels, corresponding to different phases of the wind, thus allow us to put constraints on the size, morphology and distribution of the clumps. Here, we present our results of the clump characterstics derived from gratings observations of Cyg X-1 and discuss them in comparison to findings from other methods and to predictions of wind models.Work by LLNL was performed under the auspices of the U.S. DOE under Contract No. DE-AC52-07NA27344.
The Evolution of Teacher Professional Development Workshops at McDonald Observatory
Hemenway, Mary K
Since 2001, McDonald Observatory has offered 1-10 Teacher Professional Development workshops on site in west Texas per year. Almost two thousand (elementary, middle, or high school) teachers attended workshops that provide hands-on/minds-on instruction in astronomy, related physical science, and earth science topics. Many activities are directly applicable in the teachers’ classrooms while others focus on improving teacher content knowledge. Most workshops include experience at the telescope, with the higher-level workshops using professional research telescopes and instrumentation. This paper will examine the development of the program and changes implemented to respond to teacher needs as science teachings standards have evolved through time. Recent evaluation results indicate that participants use the materials and activities within their classrooms, especially those that are easily implemented directly in the classroom, are low-cost, and hands-on. Teachers also identify the benefits and enjoyment of their unique interactions with professional astronomers and engineers with whom they interact as part of the program, and state that their confidence in teaching these scientific concepts is improved.
Black Hole mass measurements with ALMA
Henao, Lady
We will present the results of our project to use molecular gas emission to measure or constrain the mass of the supermassive black hole (SMBH) in a sample of nearby galaxies. Sample galaxies were selected to be those whose SMBHs are expected to have the largest angular 'sphere of influence' (SOI). We will present our high precision SMBH mass measurements in NGC 4751 and NGC 4945, and the implications of our (relatively highly resolved SOIs) results for SMBH constraints in galaxies whose SOIs are only partially resolved.
The NIRSpec Microshutter Array Planning Tool
Henry, Alaina
The JWST NIRSpec multi-object spectroscopy (MOS) mode provides multiplexing 0.6–5.3 micron spectroscopy capabilities over a 3.6' × 3.4' field of view. This mode uses tiny configurable shutters in the micro-shutter assembly (MSA) to acquire dozens to hundreds of spectra of astronomical targets within a single exposure. In order to facilitate planning and execution of observations with custom configurations, our team has develop the MSA Planning Tool (MPT). This first-of-its-kind MOS design software works around the unique features of the MSA (e.g. stuck shutters), to optimize observations and reach the most high-priority science targets. In this poster, I will present a quick-start guide to using the MPT, and provide hands-on training to interested users.
Raman-Scattered O VI 6825, 7082Å and C II 7023, 7053Å in the Symbiotic Nova RR Telescopii
Heo, Jeong-Eun
We present a high-resolution optical spectrum of the symbiotic nova RR Tel obtained with MIKE at Magellan-Claytelescope. RR Tel is a wide binary system of a hot white dwarf and a Mira with an orbital period of a few decades,where the white dwarf is accreting through gravitational capture of some fraction of material shed by the Mira.We find broad emission features at 6825, 7082, 7023, and 7053Å, which are formed through Raman scattering of far-UV O VI 1032, 1038, C II 1036 and 1037 with atomic hydrogen. Raman O VI 6825 and 7082 features exhibit clear double-peaked profiles indicative of an accretion flow with a characteristic speed ~40km/s. Raman C II features have a simple Gaussian profile of speed ~20km/s. We perform a profile analysis of the Raman O VI and C II features by assuming that O VI emission traces the accretion flow around the white dwarf with a representative scale of 1 AU whereas C II is formed in a much more extended region. A comparison of the restored fluxes of C~II 1036 and 1037 from Raman 7023 and 7053 and observed C~II 1335 an 1336 is consistent with the distance of RR~Tel $\sim 2 {\rm\ kpc}$ based on interstellar extinction of C~II.
Prestellar Core Collisions
Herbst-Kiss, Gabor
I will present simulations of prestellar core collisions using the smoothed particle hydrodynamics code GANDALF. We focus on changes of the angular momentum, the internal energy, and the mass before and after the collision of prestellar cores in the interstellar medium. In the timeline of star formation, a molecular cloud has to lose 6-7 orders of magnitude of its initial specific angular momentum to the final formed protostar. This loss happens in distinct stages due to certain processes (e.g. magnetic braking, fragmentation and turbulence). The first entities formed out of fragmenting filaments are structures of several Jeans masses. These objects with small seperation could collide in regions of high core density. Also colliding clouds and filaments were already identified (e.g. in the Pipe Nebula) which favor collision processes. To study the effects of these collisions on the loss of angular momentum, we use Bonnor-Ebert and truncated Plummer spheres in a variety of initial states. Therefore, a set of simulations with various initial seperation distances, masses, impact parameters, alignments of rotation axis and turbulence will be run. We analyze the transport of angular momentum during the collision and loss due to linear movement and dissipation resulting from the collision. The numerical study of collision scenarios presents the conditions set to form stable, virially bound and unbound objects and the initiation for collapse of prestellar cores. The resulting v_lsr gradient of the 2D projected core, the oscillation patterns and dissipated material after the merge will help in the identification and interpretation of real observed cores. We will show preliminary results on our first targets of cores in the Pipe Nebula.
Lyman Continuum Escape Channels in the HI Halo of SBS 0335-52E
Herenz, Edmund Christian
I will report on the discovery of ionised gas filaments in the circum-galactic halo of the extremely metal poor (Z/Zsun = 1/40) starburst galaxy SBS 0335-052E. Due to its compactness and low-metallicity this galaxy is considered a good analogue of high-redshift star-forming galaxies. Our observations with the MUSE integral field spectrograph reveal three ~10 kpc long and ~2 kpc wide filaments in Halpha and [OIII] down to surface-brightness levels of 10-19 erg/s/cm2/arcsec2. VLA 21cm observations show that the compact starburst is embedded in a giant HI halo, that would naturally absorb all Lyman continuum emission from the galaxies young stellar population. However, a combined analysis of the MUSE and the VLA data suggests that the newly detected filaments likely penetrate fully through the neutral circum-galactic medium. We therefore suggest that the filaments, created by star-formation driven feedback, act as Lyman continuum escape channels. If such narrow channels are a general feature of high-z starbursts, their ionising radiation output would be highly anistropic and concentrated to small solid angles. Accounting for this effect might be important when budgeting the ionising photon contribution from low-mass star-forming galaxies in reionising the universe.
MUS(E)ings on the Lyman Alpha Emitter Luminosity Function at z~3-7
Herenz, Edmund Christian
One of the drivers for the construction of the MUSE Integral Field Spectrograph at ESOs VLT was to determine the Lyman Alpha Emitter Luminosity Function (LALF) at redshifts greater than 3. Here we present recent LALF results from MUSE surveys, with a focus on the MUSE-Wide survey. We demonstrate the construction of the selection function for this survey, and we present different non-parametric, as well as parametric maximum-likelihood techniques to estimate the LALF. In particular, we find that by not taking the extended nature of Lyman alpha emitting galaxies into account, previous narrowband surveys understimated the number density of fainter galaxies in their samples by factors of up to 3. Moreover, we show evidence for an non-evolving observed LALF over the redshift range 3.1 < z < 6.7. We conclude by highlighting the need for combined evaluation of deep and ultra-deep MUSE observations with wide-field narrowband surveys in a homogenous statistical framework for an accurate determination of the high-z LALF.
Restarting activity in the nucleus of PBC J2333.9-2343
Hernandez-Garcia, Lorena
Under unification schemes, active galactic nuclei (AGN) can be explained by orientation effects. However, some sources show properties at different frequencies that led to incongruent classifications and cannot be explained by such unification scheme. This is the case of PBC J2333.9-2343; its optical spectrum is of a type 2 AGN but its X-ray spectrum does not show signs of absorption, and in the radio it has many features typical of a blazar but it is a giant radio galaxy. Using multiwavelength simultaneous data from XMM-Newton, San Pedro Mártir telescope and VLBA, we find that these classifications cannot be attributed to variability. We propose that PBC J2333.2343 is a blazar that has undergone a restarting activity episode in its nucleus. Interestingly, it has changed from being a radio galaxy to become a blazar, showing an exceptional change in the direction of the jet that, by chance, occurred in the plane of the sky. It also shows a change in the broad line region (BLR) clouds and increasing variability at all observed wavelengths and we have detected an outflow in its optical spectra.
Chemical evolution models for Leo A and IC1613.
Hernández-Martínez, Liliana
We have developed one-zone chemical evolution models (CEM) for two dIrr galaxies, analysing their chemical evolution in a cosmological context. One of our main constraints in our chemical evolution models is the star formation rate obtained from very deep observations. As part of our results, we are able to reproduce the metallic evolution estimated by observations. We have two main results: 1) from our CEM we can infer the mass assembly history (MAH) of each dIrr galaxy, and 2) we propose to include an outflow mainly driven by star formation, in order to reproduce the metallic evolution for Leo A while for IC 1613 the required outflow model must be more complex and ir would be explain in detail.
Iron-nickel distribution on experimental barred olivine-like chondrules
Hernández-Reséndiz, Patricia
Barred olivine chondrules (BO) are fully melted chondrules and they constitute less than 10% of chondrules in ordinary chondrites (Jones 2012). We have prepared in our laboratory experimental BO chondrule-like melts with the purpose of studying the formation processes of type IA BO chondrules, as well as their physical and chemical characteristics. Samples were melted with the help of a 50W CO2 laser emitting in the infrared at a wavelength of 10.6µm inside a vacuum chamber at 0.76atm. We measured the distribution of relevant elements present in chondrules in our experimental samples (Fe, Mg, Ni and Mn), in order to understand the origin of chemical zoning and the evaporation rates of Fe and Ni. The values obtained for the Fe coefficient suggest that the crystallization occurred after a significant amount of evaporation of FeO (~50% of the total FeO content for starting material). We highlight Fe-Ni particles present in our analogs, with a similar composition as reported inside chondrules of Semarkona LL3.0 chondrite, and explore the hypothesis that Fe-Ni grains may have formed at the melting stage of chondrule formation. If this hypothesis is valid, Fe-Ni abundances in metal grains inside natural chondrules can yield information about pressure, evaporation and cooling rates during chondrule formation.
Formation and Galactic Dynamic Evolution of Young Star Clusters
Hetem, Annibal
We present an analysis of a sample of clusters of young stars in order to investigate the inherent properties of clustering and dynamic evolution of stellar components. In previous works, we measured the parameter Q for a set of 25 clusters and the results were correlated with other properties of the spatial distributions determined through the King profile and show that almost half of these groups have a relation with the fractal dimension of their parental cloud. The statistical parameter Q was measured for the clusters and its correlations with the estimated fractal dimension for the projected near clouds are presented. There are also indications of the presence of substructures similar to those observed in the surrounding clouds. However, other clusters have a radial distribution that does not coincide with the structure of the clouds. These properties may lead to conclusions about the initial conditions of clusters formation (cold collapse or hot collapse), initial evolution (bound or not) and its expected galactic dynamic evolution (crossing time). These studies may give us information about the history of the influence of the Galaxy on clusters and how they were affected by their passage through their structures. In addition, present the application of new mathematical and numerical techniques with potentiality for use in models of filamentary structures.
Exploring the dawn of black holes with the Lynx X-ray concept mission
Hickox, Ryan
In recent years, extragalactic surveys have made great strides in tracing the growth and evolution of black holes and their connections to galaxies and halos over most of cosmic history, from the local Universe to redshift 2 and beyond. However, the deepest, distant Universe remains relatively unexplored, and important questions remain about the emergence of “seed” black holes at z > 6, and their evolution over the first few Gyr up to the epoch of peak activity at z ~ 2, much of which may be "hidden" by obscuring material. I will present a brief overview of our current understanding of distant AGN, and will discuss prospects for the future with upcoming facilities such as JWST, WFIRST, Athena, and Lynx. I will focus particularly on how the high throughput and exceptional angular resolution of NASA's Lynx X-ray concept mission can revolutionize our understanding of the growth of black holes, their host galaxies, and environments the early Universe. This work is supported in part by National Science Foundation CAREER award 1554584.
Massive star evolution : mixing processes, rotationally-induced mass loss, and mass-luminosity relationships.
Higgins, Erin
Massive star evolution remains ambiguous with respect to key physical processes, yet advancements in theoretical modelling are essential in understanding the progenitors of black holes and neutron stars. As we continue searching for gravitational wave events like GW150914, it will be crucial to understand the evolutionary channels which led to such an event. We study the dominant processes such as mass loss, convective overshooting and rotation with the aim of constraining physical parameters qualitatively through MESA evolutionary models. Our results highlight the necessity of rotational mixing since observed intermediate level nitrogen enrichments are unachievable with only mass loss and convective overshooting, employed as mixing processes. We calibrate our stellar evolution models for a range of objects and compare them to previous grids of models (such as Brott et al. 2011, Ekstrom et al. 2012).
Solo Dwarf Galaxy Survey: Exploring Isolated Dwarfs in the Local Group
Higgs, Clare
The Solo (Solitary Local) Dwarf Galaxy Survey is a volume limited sample of all nearby (< 3 Mpc) and isolated ( > 300 kpc from the Milky Way or M31) dwarfs, with wide-field g and i imaging. This survey uses resolved stellar populations to parameterize these low mass systems. Comparison to the well studied satellite dwarfs characterizes the evolutionary impact of a large galaxy in close proximity. The deep, wide field nature of this survey also lends itself to searching for substructure around these dwarfs, both globular clusters and possible faint satellites. I present a subset of the closest Solo dwarfs, all within the virial radius (approximately 1 Mpc) of the Milky Way. This sample has been characterized using consistent methods, despite the diversity in mass and size between these dwarfs. The analysis focuses on extended stellar structure and morphology, using resolved stellar populations. We then examine trends with star formation history, separation from a large host galaxy, and HI structure . This first subset emphasizes the unique challenges and advantages of this survey. In addition, I present a first look at a complete census of globular cluster candidates within these dwarfs. The Solo Survey provides detailed look at the extended structure of nearby dwarfs and aids in characterizing the evolution of galaxies in the faint limit.
Toward understanding origin of gas in debris disks
Higuchi, Aya
Debris disks have optically thin dust components around main-sequence stars. We reduced ALMA archival data of the debris disk candidates and derived the dust and gas mass assuming the ISM abundance of CO/H2=10-4. From the result, we found a good correlation between dust mass and age of the central star: dust masses decrease with age of central stars. We expected the similar trend that gas masses decrease with the age, but found no trend between them. We thus concluded the ISM abundance is not a good assumption to derive H2 mass for debris disks. In addition, recently, we have firstly detected [C I] emissions in the gaseous debris disks of 49Ceti and ßPictoris with the ASTE. If C/CO ratio can be obtained by observations, there is a possibility to estimate the amount of H2 using the chemical reaction of CO.
CHARACTERIZATION OF THE IMPACT OF AGN IN THE KINEMATICS OF A SAMPLE OF GALAXIES-CALIFA
Higuera G., Mario A.
Using techniques of integral field spectroscopy, it was made a study of the impact of AGN in its host galaxy, looking for kinematics of ionized gas of Ha, [OIII]5007 lines. There is evidence of a distortion in the velocity distribution field for objects with presence of an AGN. In order to develop the velocity field maps there was used a pipeline PIPE3D, which was elaborated by Sánchez, S.F. et al. 2016. There was found that in the central region of each working galaxy, there is evidence of higher kinematic speeds and higher dispersion speeds for the Ha and [OIII]5007 emission lines, compared with the velocities that were observed in the control galaxies. It can confirm the activity in the nuclear region due to the presence of an AGN. It was found a disturbance in the velocity distribution field of the host galaxy, an alteration of the kinematic axis and of the velocity field distribution, which is different than expected for ideal disk galaxies. In contrast, the control galaxies showed properties of rather continuous and symmetric velocity distribution, as well as the presence of a kinematic axis. A difference in the distribution of kinematic speeds of Ha was observed in the circum-nuclear region of active galaxies. In a first approximation the object NGC 5443, presents higher kinematic speeds of Ha and [OIII]5007, in the central region compared to those that were evidenced in non-active galaxies, being very similar to the distributions found in the work galaxies NGC 5971 and NGC 2410. The object NGC 5443 does not have records in the literature as a LINER type object or as an active galaxy. It can be inferred first, that the IFS in a first approximation, is a potential tool that allows to demonstrate the presence of an AGN in places where previously such evidence could not be found; and secondly, that the maps of the ionized gas kinematics trace the possible existence of an AGN that may or may not be identified by other methods of study.
The IAU 2000A Nutation Theory in a Binary-PCK Kernel
Hilton, James
The U.S. Nautical Almanac Office is constructing the IAU 2000A nutation theory ephemeris in a binary-PCK kernel for use in situations where speed of execution is critical. The nutation ephemeris will cover the time-span of the Jet Propulsion Laboratory's DE430 planetary ephemeris, JD 2287184.5-2688976.5 TDB (~1550.0-2650.0 CE). The method used in constructing this ephemeris also permits the evaluation of the instantaneous time rate of change of the nutation angles. Putting the theory in this format reduces the number of additions and multiplications required by about 2.75 orders of magnitudes each, and eliminates the need to evaluate any transcendental functions. The drawbacks of this representation are its limited time-span and the overhead of locating and reading the correct set of coefficients from the binary-PCK kernel. Extensive testing of numerous scenarios will be required to evaluate the true improvement in evaluation time. Currently, the conversion to a binary-PCK kernel is nearing completion. The project report at the General Assembly will include up-to-date information on testing this technique.
Exploring the Radio Continuum vs. Star Formation Rate Relation in Nearby Dwarf Galaxies
Hindson, Luke
The source of the radio continuum (RC) emission from normal star forming galaxies is directly linked to massive stars and can be used as an indicator of the star formation rate (SFR). This is seen observationally in the RC-SFR relation. This relationship may provide a robust, unbiased, and perhaps most importantly an extinction free tool for characterising the SFR in both the Local Universe and at high redshift in upcoming radio surveys with instruments such as the VLA, LOFAR, and SKA. In an effort to calibrate the relationship and understand its physical origin we have undertaken a sensitive, multi wavelength, high-resolution study using the VLA of a sample of 40 nearby dwarf galaxies (a proxy for early type galaxies) taken from the LITTLE THINGS survey. By combining our VLA observations with ancillary data including H-alpha, 24um, and the FUV we separate the radio continuum emission into its thermal and non-thermal components and compare these to the SFR. We use these results to calibrate the RC-SFR relation on scales from 200 to 700 pc, explore the equipartition magnetic field properties of the galaxies, and the intrinsic scatter in the RC-SFR relation.
The Structure of the Inner Circumstellar Shell in Miras
Hinkle, Kenneth
Stars undergo most of their mass loss on the AGB. While the overall process is understood many details remain that need further study. We report on spectra of near-infrared, low-excitation CO fundamental and first-overtone lines in three Miras. The observations are in time series spanning up to two decades. The temperature and velocity probed by the low-excitation CO lines are significantly different than that of the stellar photosphere measured by higher excitation lines. The low-excitation CO region undergoes aperiodic variations. The lines are shown to probe the structure of the circumstellar shell close to the star. By drawing from the extensive literature on multi-frequency observations of Miras we show how the low-excitation CO region is connected to the structure of the circumstellar region and the mass loss process.
Enrichment of heavy elements in chemo-dynamical simulations of dwarf galaxies
Hirai, Yutaka
Recent astronomical observations have shown that there are large star-to-star scatters in the abundances of r-process elements and increasing trend of Zn in extremely metal-poor stars. However, it is not yet clear how the early chemo-dynamical evolution of dwarf galaxies affects the abundances of heavy elements. Here we report that high-resolution N-body/smoothed particle hydrodynamics simulations of dwarf galaxies. We find that galaxies with star formation rates less than 0.001 solar masses per year reproduce the observed abundances of r-process elements assuming that neutron star mergers are the major astrophysical sites of r-process. On the other hand, r-process elements appear at a higher metallicity in galaxies with star formation rates greater than 0.01 solar masses per year. We also find that the ejecta from electron-capture supernovae contribute to stars with [Zn/Fe] > 0.5. The scatters of heavy elements mainly come from the inhomogeneity of the metals in the interstellar medium. We estimate that timescale of metal mixing is less than 40 Myr using heavy element abundances in metal-poor stars. This timescale is lower than that of typical dynamical times of dwarf galaxies. We also find that the r-process enhanced stars seen in the Milky Way halo are formed in halos with a size of ultra-faint dwarf galaxies by using our high-resolution cosmological zoom-in simulations. Our results demonstrate that the future observations of the abundances of heavy elements in extremely metal-poor stars using forthcoming facilities will be able to constrain the early chemo-dynamical evolution of the Local Group dwarf galaxies.
The Lifecycle of Dust and Metals in Low-Abundance Galaxies
Hirschauer, Alec
I will discuss the recent discovery of the extremely metal-poor star-forming galaxy Leoncino (~2% solar), among our most promising early-Universe analogues to date, and whose discovery heralds a boom in finding additional similar low-metallicity specimens. Studies of such nearby low-abundance galaxies reveal the importance of the effect of chemical composition on star formation and the lifecycle of dust and metals during the peak epoch of star formation in the Universe. I discuss plans to study the lifecycle of dust and metals with JWST GTO observations of the low-abundance star-forming galaxy NGC 6822 and the extremely metal-deficient blue compact dwarf galaxy I Zw 18. In preparation for these observations, I am investigating the dusty stellar populations in NGC 6822 including the dust-producing stars (e.g., asymptotic giant branch stars) and young stellar objects.
The formation of supermassive binary black holes in galaxy mergers
Ho, Yu-Heng
Using N-body simulations, we've investigated the formation of supermassive binary black holes(BBH) under different impact parameters, i.e. BBHs with different initial angular momentum, we've traced the individual supermassive black hole(SMBH) at an initial distance of 300 kpc, to the stage when the BBH becomes hard, the time scale of different stages has been estimated, and the relation between the orbital evolution and the properties of the stellar cores are discussed, also, the transfer of the angular momentum between the galaxy and the BBH is studied, we find that certain merger geometries of the galaxies do affect the lifetime of the BBH significantly, the duration time of the individual SMBH from entering the core of the merged galaxy towards forming a hard binary can be as long as 1.5 Gyr. Furthermore, in traditional loss-cone theory, triaxial systems are generally believed to be efficient towards removing the angular momentum of the BBH so that the binary can be driven into coalescence at the hardening phase, we find that this might not be the case for the early stage of the binary formation while dynamical friction still plays the dominant role of subtracting the BBH orbital energy. We conclude that the geometry of the merger as well as the structure of the galactic angular momentum also plays an important role of determining the lifetime of the BBH, the situation might be more complicated if, for example, multiple mergers or larger mass ratio between the SMBHs are considered.
New Insights in Interstellar Nanoparticles
Hoang, Thiem
Interstellar nanoparticles, including polycyclic aromatic hydrocarbons (PAHs), nanosilicates, and iron nanoparticles, are believed to play an important role in modern astrophysics. Mid-infrared emission from PAHs is widely used as a tracer of star formation activity. PAHs is also thought to be a leading carrier behind the long-standing mystery of Diffuse Interstellar Bands (DIBs). In this talk, I will discuss new insights into the crucial importance of interstellar nanoparticles. I will start with a review on anomalous microwave emission (AME) by rapidly spinning nanoparticles and the AME polarization, which is a critical challenge for constraining cosmic inflation via B-modes in cosmic microwave background (CMB) polarization. I will then present a new model of polarized emission from PAHs and discuss important implications for getting insight into the alignment physics of nanoparticles and for a potential new way of tracing magnetic fields via mid-IR polarimetry.
Spectroscopy of Spatially Resolved Exoplanets with JWST NIRSpec
Hodapp, Klaus
The NIRCam science team will use part of their guaranteed observing time to image exoplanets with the coronagraph in NIRCam, obtain transit spectroscopy with the slit-less prism spectroscopic mode of NIRCam, and use NIRSpec for integral field (IFU) spectroscopy of exoplanets that are spatially resolved from their parent Star.This poster describes the latter of these observing projects. Our goal is to obtain spectra in the 3.0 - 5.0 µm range, where most moderately young exoplanets are expected to be brightest, with sufficient resolution (R=1000 and SNR (>30) to allow a detailed comparison with model atmospheres.In the 3 - 5 µm range, JWST is uniquely capable for these observations. We will use the NIRSpec spectrograph with its integral field unit (IFU) to preserve as much information as possible about the residual speckle pattern. The primary component will be outside of the IFU, but its speckle pattern will dominate the read noise out to several arc-seconds separation. We plan on observing at two telescope role angles to subtract out the primary component PSF. The wavefront stability and precision of pointing of JWST are essential for these observations.There are only a small number of suitable spatially separated exoplanets currently known. It is important that we observe several of these with JWST early in its operation, so that we establish the techniques and demonstrate feasibility.
Revisiting Historical Novae
Hoffmann, Susanne
In our project we are studying historical reports of transient phenomena aiming at a catalogue of novae. Lists of historical nova candidates had been published before, for instance by Hsi 1957, Ho 1962, Clark & Stephenson 1976, Hasegawa 1980, Duerbeck 1986, Xu et al. 2000, and others – mostly collections of guest stars including much more phenomena. Our survey is a review and re-analysis of all those suggestions. A historically reported tailless "guest star" could in principle be a comet without visible tail, a nova, a supernova, a kilo- or macro-nova, or even a meteor._x005F By applying clear criteria to the different phenomena and by taking special care on transforming the old prosa text's information into modern coordinates for follow-up observations, we consider in particular those "guest stars" recorded with precise position and as having appeared for more than one night._x005F In our contribution, we review and discuss some suggestions of historical novae, such as "Nova Scorpius 1437" (Shara et al. 2017), CV BK Lyn as nova AD 101 (Patterson et al. 2013, Hertzog, 1986), and the guest star of AD 396 (Hertzog, 1986) regarding whether or not they fulfill genuine nova criteria and how well the position of the historical observation can be constrained._x005F _x005F
Analysing and Visualising MUL.APIN – a witness of Babylonian astrometry
Hoffmann, Susanne
The compilation of MUL.APIN has been canonical for more than a millennium and dates back before 1000 BCE. The first of two tablets contains of astronomical data like lists of heliacal rising dates, simultaneous risings and settings as well as constellations crossing zenith (the so called ziqpu-asterisms). Thus, the very first section of the text might also be a list of asterism and it is, therefore, called a star catalogue. Nevertheless, the list does not contain a single number to describe the position of a constellation. For the few single stars mentioned the position is given relative to their constellation. However, we think, we had been able to reconstruct the depiction of the Babylonian sky chart by this part of the text – within huge margins of error.Since it is also possible to use the data of risings and settings in Mesopotamia to map the reconstructed Babylonian asterisms on the celestial sphere, we wish to present a virtual 3D-image of the Babylonian globe.This leads to a new hypothesis: Using a globe like this, it appears very intuitive to obtain the data written in the second to sixth section of the first tablet of the series. Up to now, there had been many speculation, computations and guesses, why all dates of risings are multiples of 5 and how to interpret the lists's order. If they are read from a globe, all this is an automatic product: Positioning the globe on a certain date, it is easy to read the asterisms above the eastern and western horizons as well as the asterism following below the eastern horizon in soandso many days. Hence, the usage of a globe to compile the lists of MUL.APIN might explain many aspects in an easy way.Therefore, in our contribution, we do not only want to suggest a fulldome-visualisation of Babylonian constellations for modern planetariums but also a historically brave hypothesis of a Babylonian globe and encourage archaeologists to dig for it.
After 65 years dedicated to astrometric instrumentation, a Gaia successor is in sight
Høg, Erik
The astrometric foundation of astrophysics has been enormously improved by two ESA satellites that determined the positions, distances and motions of stars. I was fortunate to be at the right place and right time so that I could contribute towards various developments after beginning work as a student in 1953 at a new Danish meridian circle. These include the designs of: a new method of astrometry by photon counting for the Hamburg meridian circle in 1960; a new design for the Hipparcos mission in 1975; the Tycho experiment for the Hipparcos satellite in 1981; direct-imaging on CCDs for the Gaia mission in 1992; and most recently, a Gaia successor in 2013 that should be launched in about twenty years. In April 2017 ESA approved our proposal (Hobbs et al. 2016, arXiv 1609.07325) to study a Gaia successor with infrared detecting capabilities. That proposal was one of three selected out of 26 submitted in response to ESA's call for new "Science Ideas" to be investigated for feasibility and technological developments. The study by ESA has resulted in the focal plane with NIR sensors shown on the poster at lower right.
SOFA - Providing Standards via Software
Hohenkerk, Catherine
The Division A functional working group, Standards of Fundamental Astronomy (SOFA), continues its task of establishing and maintaining an accessible and authoritative set of algorithms and procedures that implement standard models used in fundamental astronomy. This poster highlights the current software collection that SOFA makes freely available in thirteen different areas; astrometry, time, precession-nutation, to name but a few. This will include the new routines that were added during the last triennium.
Multiband study of AGB stars in clusters
Hojaev, Alisher S.
The interest to AGB population which consists of evolved cool luminous low- to intermediate mass stars (0.6-10 Ms) and exhibits the late phase of life of solar-type stars as well is still growing these years. In the one hand, increasing data stream from the modern facilities and instruments revealing new or clarifying known properties of AGB stars, in the other hand, enhancing computer capabilities allow to high-performance 3D modeling of physical conditions and phenomena connected with AGB stars. Especial importance of red giants observations in AGB and pre-AGB stars stages is in application of their group properties (particularly, TRGB and RCG) to the modeling of stellar systems, particularly open and globular clusters, for example, to estimate the age of the system. For this purpose we have carried out multiband photometry for the large sample of open clusters on 0.6-1.5 m class telescopes at Maidanak, Byurakan, Lulin observatories. The group parameters for clusters were determined and discussed. The continuation of observational study of AGB stars is planned. One of the new and perspective observational programs in research of open, globular clusters and other stellar systems is a intermediate and narrow band photometry within the frame of international all-sky survey of northern hemisphere. Further we intend to obtain spectral and deep photometric data using modern adaptive 4 m class telescope to be created in Uzbekistan and has been intended to install at Maidanak observatory well-known by excellent conditions for astronomical observations (large amount of clear sky, high quality and stability of atmosphere optics, etc) and advantageous location for time domain astrophysical research.
H2 and HI clouds in dwarf galaxies
Hojaev, Alisher S.
Based on radio astronomy data available in special resources and using the data mining technology (aka, knowledge discovery in databases, KDD) the general catalog of extragalactic molecular and atomic hydrogen clouds and nebula was created and analyzed. Although the main part of such objects is located in spiral galaxies at different distances from the Milky Way Galaxy a few samples of dwarf galaxies also have such structural elements as well, according to the observational data. In accordance with the range of their masses and sizes as well as other physical parameters the observed clouds are of giant and hyper-giant molecular cloud class objects. The statistical and physical correlation analyses were made on clouds features and basic physical parameters. The results were compared with other types of galaxies where the molecular and atomic hydrogen clouds and nebula were ever observed. The gaseous clouds of both dwarf irregular galaxies and giant spirals are apparently located near the boundary of gravitational instability that promotes active star formation. The theoretical modeling of dynamical evolution of these galaxies as well as massive star formation in low [Fe/H] environment are also considered and discussed.
Exo-environment in solar neighborhood: from molecular gas to protoplanet disks
Hojaev, Alisher S.
Relying on the data of complex general catalog we compiled using the KDD method (knowledge discovery in databases), the 3-D distribution and physical properties of molecular clouds in local galactic environments of the Sun were analyzed. We also combined a detailed database of the star formation indicators and young-star populations in the solar neighborhood, and protoplanetary accretion disk evidences around CTTS and WTTS were considered and discussed. The search and detailed study of exoplanets and protoplanets on 4 meter fully adaptive telescope with laser-guide-star technology which is creating to install at Maidanak astrophysical observatory (Uzbekistan) having the perfect seeing conditions as well as an appropriate geographical localization to support the time-series observations as well as other time domain astronomy features are included into scientific program of the telescope and discussed in report.
Prospect science with modern 4 meter class telescopes
Hojaev, Alisher S.
According governmental initiatives to promote and enhance astronomical research in Uzbekistan, which do has deep roots and recognized achievements in ancient astronomy, the work has been started to create a 4-meter adaptive mirror telescope using the laser-guide-star wave-front correction technology. The telescope is intended to install at Maidanak astrophysical observatory well-known by perfect seeing conditions for astronomical observations (large amount of clear sky, high quality and stability of atmosphere optics, sharp FWHM of stellar image, etc.) as well as advantageous geographical location which makes it as a indispensable node for time domain astrophysical research. The international multi-messenger channels of observation are expected. The traditional for Maidanak observatory time-series observations are included into a preliminary scientific program of the telescope but they will be extended to much more deep level photometric and spectral data. The search and detailed study of exoplanets and protoplanets, exoplanet habitability issues, study of star formation in the Galaxy and in distant galaxies, optical identification and spectral survey of X-ray sources in galaxy clusters, transient phenomena such as gamma-ray bursts, supernovae, and compact mergers, especially optical and infrared afterglows of the gravitation waves emitters, are within the key multi-messenger sources. The necessary assistance from the IAU headquarter, its nodes and ELT community is described and discussed in the 4 meter telescope creation, its equipping with focal plane instrumentation and preparation of highly qualified astronomers who could be the local users for the advanced telescope. Possible synergy with other telescopes including that of extremely large class is considered.
Essay on astronomy outreach issues
Hojaev, Alisher S.
Outreach and wide popularization of astronomy among broad community, cooperation of professional astronomy researchers with amateur astronomers and citizen-science projects in astronomy are really important in era of globalization and significant growth of scientific discoveries and extremely large data flow (Big-data) in all fields of astronomy. The draft overview is presented on astronomy science and outreach in Uzbekistan from ancient to now and further including the new trends (triune complex of the scientific park, boarding school and professional research institute for astronomy, astronomy and aerospace summer camps, mass-media, etc.). The ideas are proposed to increase the outreach issues of open astronomy for public.
Toward new IAU Strategic Plan
Hojaev, Alisher S.
Coming closer to the completion of the first decadal (2010-2020) Strategic plan of the IAU on Astronomy for Development and preparing the new IAU Strategic Plan we should note the benevolent influence of IAU Office of Astronomy for Development (OAD) on convergence of astronomers and enhance their role in research, education and outreach. There are undoubted achievements, however, the OAD's role in promotion and supporting astronomy at regional and local level through international scientific and technological cooperation, the exchange of experts and assistance in the training of relevant specialists should be strengthened and enhanced. Until now, our colleagues of National Astronomical Observatories of Chinese Academy of Sciences (NAOC) together with astronomers of Ulugh Beg Astronomical Institute of Uzbek Academy of Sciences have renovated and modernized the 1 meter Zeiss telescope at Maidanak observatory (Uzbekistan) and we started deep halph-sky survey within international collaboration with NAOC, Xinjiang astronomical observatory (Chinese Academy of Sciences, China) and Steward observatory (University of Arizona, USA) in special SAGE intermediate- and narrow- band photometric system (developed by astronomers of NAOC). Recently, thanks to governmental efforts to promote and enhance astronomical research, which has deep ancient traditions and world-class achievements in Uzbekistan, a remarkable breakthrough in the development of astronomy and space sciences, education and their promotion is expected. A park of astronomy and aeronautics, an astronomical boarding school are being created, research has been started to create a 4-meter adaptive mirror telescope with laser correcting system. The necessary assistance and possible support from the OAD are described and discussed in the 4 meter telescope creation, the developing of the focal plane instrumentation and preparation of highly qualified astronomers who will be the local users for the advanced telescope.
Spatial and Temporal Correlations in the Interstellar Medium
Hollins, James
We apply correlation analysis to random fields in numerical simulations of thesupernova-driven interstellar medium (ISM) with the magnetic field produced bydynamo action, and compare the properties of simulated radio observables withthe physical components in the model.We consider the cold, warm, and hot phases of the ISM separately; theanalysis mostly considers the warm gas, which occupies the bulk of thedomain.The correlation scales of random magnetic field, density, and velocityare distinct at all heights in the warm phase.The correlation time of the random velocity is comparable to the eddy turnovertime, although it may be shorter in regions with a higher starformation rate.The random magnetic field is anisotropic, with the standard deviations ofthe $y$- and $z$-components enhanced compared to the standard deviationof the $x$-component.The anisotropy is attributed to the global velocity shear from galacticdifferential rotation, and locally inhomogeneous outflow to the galactichalo.The correlation length of Faraday depth along the is greater than thecorrelation lengths of both electron density and vertical magnetic field.Such comparisons may be sensitive to the orientation of the line of sight.Uncertainties of the structure functions of synchrotron intensity rapidlyincrease with the scale. This feature is hidden in power spectrumanalysis, which can undermine the usefulness of power spectra fordetailed studies of interstellar turbulence.
Building a Radio Astronomy Community
Hollow, Robert
Universities around the world are looking for programs to differentiate themselves from others and to equip their students for the challenges presented by new technologies and facilities. With the advent of new radio telescopes such as the Square Kilometre Array and FAST and the massive data sets such facilities will produce opportunities to expose, engage and train students are becoming important. In response to this need and building on the success of the innovative PULSE@Parkes education program for high school students CSIRO Astronomy and Space Science in Australia have been developing a new program; OPTIMUS.OPTIMUS (Observing with Parkes, Training and Introduction, Module for University Science) is a flexible package providing undergraduate and postgraduate students a hands-on introduction to radio astronomy observational techniques and data analysis, using pulsars initially as the context. It includes background educational material, tutorials, a virtual machine to allow students to install a complete package of relevant software tools, access to data and telescope time on the 64m Parkes radio telescope plus support and observer training. Initial topics for the program include pulsar timing and the search for gravitational waves, but will in time incorporate other topics within astronomy and astrophysics.We outline the approach taken in developing the program and describe some of the tools produced. Various ways in which users can engage with the program are identified and we discuss how the program has evolved in response to extensive engagement with potential stakeholders around the world. The program provides a model for other institutions to provide effective training and for them to partner and build a global community.
Rotating disks around M-type AGB stars
homan, ward
High-resolution observations of the circumstellar environments (CSE) of AGB stars reveals that companion-induced morphologies are common. High mass-loss rate C-rich winds occasionally exhibit convincing spirals, whereas O-rich environments seem to be less morphologically well-defined. We present a study on the morphology of the CSE of the M-type AGB star EP Aquarii, observed with ALMA (cycle 4). The data reveals a complex, nearly face-on equatorial density enhancement (EDE), enclosed by a bi-conical outflow. The EDE manifests primarily as a spiral, making this the first convincing detection of a spiral in an O-rich environment. The molecular emission also shows other peculiarities like rotation, potential mass-transfer and voids, all which suggest that a companion may be present. We deduce the position angle and inclination of the symmetry axis of the system, and conclude that the observable constaints favour the hypothesis that the EDE is dominated by a tangential velocity field, as opposed to a radial one. In addition, we also present recent findings of the CSE of R Doradus. Preliminary observations with ALMA (cycle 2) at coarse spatial resolution reveal that the innermost regions exhibits a spatial offset between the red and blue shifted emission for most observed molecules. We crudely model the highly compact 28SiO emission and show that it can be explained by a tilted rotating disk, with a tangential velocity governed by angular momentum conservation, and a small outward velocity field. Both EP Aqr and R Dor are semiregular variable stars. In combination with the recent observations and modelling results of the compact, edge-on, differentially rotating disk surrounding the nearby semiregular AGB star L2 Puppis, the increasing observational sample is revealing a potential relation between the pulsational classification of M-type AGB stars and their circumstellar morphology.
Chemical evolution model to derive metallicity distributions for each stellar population
Homma, Hidetomo
I have constructed a new chemical evolution model for dwarf galaxies and compares its results with the observed chemical properties of red giant branch stars (RGBs) and RR Lyrae (RRL) stars of Sculptor and Fornax dwarf spheroidal galaxies (dSphs). The detailed chemical abundances of RGBs of nearby dwarf galaxies have been measured by spectroscopic observations. Moreover, the metallicity distributions of RRL stars are estimated from the theoretical Period-Luminosity relations in literature and it is found that the mean metallicity of RRL stars are lower than that of RGBs. In order to investigate the metallicity distributions of RGBs and RRL stars, the chemical evolution model of this study adopts the Padova stellar evolution tracks and derives the metallicity distributions of RGBs and RRL stars, respectively. Moreover, in order to derive the consistent chemical evolution with the observed color magnitude diagrams, the model adopts the star formation histories estimated from the color magnitude diagrams. The resultant chemical evolution models represent the observed metallicity distributions of RGBs in Sculptor and Fornax dSphs, respectively. However, the mean metallicity of RRL stars of the model of Sculptor dSph is lower than that of the previous work. Since the metallicity of RRL stars estimated from the theoretical Period-Luminosity relations depends on the distance modulus, it is found that the distance modulus of Sculptor dSph are larger than that of the previous work in order to represent the metallicity distributions of RGBs and RRL stars, simultaneously. The distance modulus of Sculptor and Fornax dSph derived from the chemical evolution models are $19.67 ¥pm 0.08$ and $20.81 ¥pm 0.13$, respectively. These values are consistent with the other previous works.
MICHI: a Thermal-Infrared Instrument for the TMT : Four Key Science Drivers
Honda, Mitsuhiko
With the imminent launch of the JWST, the field of thermal-IR astronomy will enjoy a revolution. It is easy to imagine that all areas of IR astronomy will be greatly advanced, but perhaps impossible to conceive of the new vistas that will be opened. To allow both follow-up JWST observations and a continuance of work started on the ground-based 8m’s, we continue to plan the science cases and instrument design for a thermal-IR imager and spectrometer for early operation on the TMT. While JWST will have exceptional sensitivity over a wide field of view, TMT will offer superior spatial and spectral resolution, key to unraveling fundamental questions in nearly every field of astrophysics.We present our key science cases and the instrumentation plans, harnessing expertise across the TMT partnership. This instrument was proposed by the MICHI team as a second-generation instrument in the upcoming call for proposals.
Gemini Observations of Two Candidate Planetary Nebulae toward the Galactic Center
Hong, Jihye
We present high-resolution near-infrared (IR) spectra of two candidate planetary nebulae (PNe) that were serendipitously found toward the Galactic center (GC). Our spectra obtained using GNIRS on Gemini North reveal strong Br ? and He I recombination lines. In one of the targets, we confidently detect Pa ß and Pa ? emissions. Based on Br ? and Pa ß lines, we estimate a foreground extinction Av ~ 20 mag for SSTGC 588220 and Av > 28 mag for SSTGC 580183. Given the large foreground extinction toward the GC, our extinction estimates plausibly indicate that they are located at the GC distance. Along with the presence of high excitation emission lines such as [S IV], [Ne III], [Ne V], and [O IV] detected in the mid-IR spectra from the Spitzer Space Telescope, and the extended emission in the Pa a narrow-band image from the Hubble Space Telescope, our observations suggest that they are the first spectroscopically confirmed PNe in the GC.
Double irony in XXL North: A tale of two radio galaxies in a supercluster at z = 0.14
Horellou, Cathy
XXL is a multiwavelength extragalactic survey that is particularly well suited to study the interplay between active galactic nuclei (AGN), galaxies and clusters of galaxies, and the large-scale structure. Our aim is to use XXL to shed light on radio galaxies and their environment by investigating the two most spectacular radio galaxies in XXL North.We identified the two radio galaxies in a visual examination of the mosaic of XXL North obtained with the Giant Meterwave Radio Telescope (GMRT) at 610 MHz. Counterparts were searched for in other bands, from X-ray to the infrared, to characterize the host galaxies and their environment. Spectroscopic redshifts from the GAMA database were used to identify clusters/groups of galaxies and estimate their masses.Both radio galaxies are of FR I type and hosted by early-type, passive galaxies at a redshift of 0.14. The first radio source, named the Exemplar, has a physical extent of about 400 kpc; it is located in the cluster XLSSC112 that has a temperature of about 2 keV and resides in an XXL supercluster with eight known cluster members. The second radio galaxy, that we named the Double Irony because of its peculiar shape (two reversed question marks), has a physical size of about 900 kpc. The position of its core coincides with that of a cataloged point-like X-ray source, but no extended X-ray emission from a surrounding galaxy cluster was detected. However, from the optical data we determined that the host of the Double Irony is the brightest galaxy in a group that is younger, less virialized, and a few times less massive than the Exemplar's cluster. A Friends-of-Friends analysis showed that the Double Irony's group is a member of the same supercluster as the Exemplar.This work shows that radio galaxies can be used to identify galaxy clusters/groups that are missed in X-ray surveys.
Reliable detection and characterization of low-frequency polarized sources in the LOFAR M51 field
Horellou, Cathy
The new generation of broad-band radio continuum surveys will provide large data sets with polarization information. New algorithms need to be developed to extract reliable catalogs of linearly polarized sources that can be used to characterize those sources and produce a dense rotation measure (RM) grid to probe magneto-ionized structures along the line of sight via Faraday rotation.We have developed a computationally efficient and rigorously defined source-finding algorithm for linearly polarized sources.We used the calibrated data set from the LOw Frequency ARray (LOFAR) at 150 MHz centered on the nearby galaxy M51 to search for polarized background sources. We cataloged about 3000 continuum sources within 2.5 degrees of the center of M51. We made Stokes Q and U images centred on each source brighter than 100 mJy in total intensity and used RM synthesis to create Faraday cubes. For each source, the noise distribution function was determined; the peaks in polarized intensity in the Faraday spectrum were identified and the p-value of each source was calculated. Finally, the False Discovery Rate method was applied to the list of p-values to produce a list of polarized sources and quantify the reliability of the detections. Of the 201 sources that were searched for polarization, six polarized sources were detected confidently. This corresponds to a number density of one polarized source per 3.3 square degrees, or 0.3 source per square degree. Increasing the false discovery rate to 50 percent yields 19 sources. A majority of the sources have a morphology that is indicative of them being double-lobed radio galaxies, and the ones with literature redshift measurements have 0.5<z<1.0.we find="" that="" this="" method="" is="" effective="" in="" identifying="" polarized="" sources. in="" the="" future,="" we="" intend="" to="" develop="" it="" further="" and="" apply="" larger="" data="" sets="" such="" as="" lofar="" two-meter="" survey="" of="" whole="" northern="" sky,="" lotss,="" ongoing="" deep="" observations="" goods-north="" field.<="" p="">
</z<1.0.we></p>
Variability in Post-AGB Stars: Pulsation and Binarity in Proto-Planetary Nebulae
Hrivnak, Bruce
We have intensely monitored photometric variability in proto-planetary nebulae (PPNe) over the past 25 years and radial velocity variability over the past ten years. Pulsational variability has been obvious, in both the light and velocity, although the resulting curves are complex, with multiple periods and varying amplitudes. Nevertheless, consistent patterns have emerged that give insight into the structure and evolution of the stars. Observed periods range from 25 to 160 days, and the periods and amplitudes reveal evolutionary trends. Evidence for binarity is more elusive, with no clear evidence emerging from these long-term radial velocity or light curves. We will present our observational results to date for approximately 30 PPNe, and discuss these results, including the search for period changes that might help constrain post-AGB evolutionary timescales.
The Role of the Magnetic Field in the Molecular Inflow in the Central 10 pc of the Galactic Center - Implications From 850 micron Polarization Data
Hsieh, Pei-Ying
Utilizing James Clark Maxwell Telescope (JCMT) 850 micron dust polarization data, weinvestigate the configuration of the magnetic (B-) field in the circumnuclear disk (CND) of the Galactic Center (GC). Overall on a large scale, the B-field shows a clear predominantly toroidal morphology in the 2-pc ring rotating with respect to supermassive black hole SgrA*. In general, the observed B-field morphology is well described by a self-similar axisymmetric disk model where the radial infall velocity is one quarter of the rotational velocity. A detailed comparison with higher-resolution interferometric maps from the Submillimeter Array (SMA) further reveals that the B-field aligns with the neutral gas streamers where they are connecting to the CND. Moreover, the innermost observed B-field structure also appears to trace and align with the ionized mini-spirals located inside the CND. This suggests that there might be one underlying B-field structure that is connecting the CND with its streamers and the inner mini-spirals. An estimate of beta_Plasma~0.02-0.04 -- based on the global B-field morphology that constrains the azimuthal-to-vertical field strength ratio to be around 40 combined with a measurement of the azimuthal velocity -- indicates that the B-field appears dynamically significant towards the CND and also onwards to the inner mini-spirals.
The Fossil Nuclear Outflow in the Central 30 pc of the Galactic Center
Hsieh, Pei-Ying
In Hsieh+ (2015, 2016, ApJ), we report a new 1 pc (30?) resolution CS(J=2-1) line map of the central 30 pc of the Galactic center (GC), made with the Nobeyama 45 m telescope. We revisit our previous study of an extraplanar feature called the polar arc (PA), which is a molecular cloud located above SgrA*, with a velocity gradient perpendicular to the galactic plane. We find that the PA can be traced back to the galactic disk. This provides clues to the launching point of the PA, roughly 6x10^6 years ago. Implications of the dynamical timescale of the PA might be related to the Galactic center lobe at parsec scale. Our results suggest that, in the central 30 pc of the GC, the feedback from past explosions could alter the orbital path of molecular gas down to the central tenth of a parsec. In the follow-up work of our new CS(J=2-1) map, we also find that, near systemic velocity, the molecular gas shows an extraplanar hourglass-shaped feature (HG-feature) with a size of ~13 pc. The latitude-velocity diagrams show that the eastern edge of the HG-feature is associated with an expanding bubble B1, ~7 pc away from SgrA*. The dynamical timescale of this bubble is ~3x10^5 years. This bubble is interacting with the 50 km/s cloud. Part of the molecular gas from the 50 km/s cloud was swept away by the bubble to b=-0.2 degree (27 pc from SgrA*). The western edge of the HG-feature seems to be molecular gas entrained from the 20 km/s cloud toward the north of the galactic disk. Our results suggest a fossil explosion in the central 3 0 pc of the GC, a few 10^5 years ago.
Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center
Hsieh, Pei-Ying
The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2 pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides a unique opportunity to study SMBH accretion at subparsec scales. Our new wide-field CS(J = 2 - 1) map toward the Galactic center (GC) reveals multiple dense molecular streamers that originated from the ambient clouds 20 pc further out, and that are connected to the central 2 pc of the CND. These dense gas streamers appear to carry gas directly toward the nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up corotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei. The results were published in the astrophysical journal (2017, ApJ, 847, 3).
NOC activities at Myanmar
Htun, Boothee Thaik
The poster present the NOC acitivites at Myanmar
A Thick Atmosphere on Super-Earth 55 Cancri e
Hu, Renyu
One of the primary questions when characterizing Earth-sized and super-Earth-sized exoplanets is whether they have a substantial atmosphere like Earth and Venus, or a bare-rock surface that may come with a tenuous atmosphere like Mercury. Phase curves of the planets in thermal emission provide clues to this question, because a substantial atmosphere would transport heat more efficiently than a bare-rock surface. Analyzing phase curve photometric data around secondary eclipse has previously been used to study energy transport in the atmospheres of hot Jupiters. Here we use phase curve, Spitzer time-series photometry to study the thermal emission properties of the super-Earth exoplanet 55 Cancri e. We utilize a previously developed semi-analytical framework to fit a physical model to infrared photometric data of host star 55 Cancri from the Spitzer telescope IRAC 2 band at 4.5 µm. The model uses various parameters of planetary properties including Bond albedo, heat redistribution efficiency (i.e., the ratio between the radiative timescale and advective timescale of the photosphere), and atmospheric greenhouse factor. The phase curve of 55 Cancri e is dominated by thermal emission with an eastward-shifted hot spot located on the planet surface. We determine the heat redistribution efficiency to be ~1.47, which implies that the advective timescale is on the same order as the radiative timescale. This requirement from the phase curve cannot be met by the bare-rock planet scenario, because heat transport by currents of molten lava would be too slow. The phase curve thus favors the scenario with a substantial atmosphere. Our constraints on the heat redistribution efficiency translate to a photosphere pressure of ~1.4 bar. The Spitzer IRAC 2 band is thus a window into the deep atmosphere of the planet 55 Cancri e.
A formation mechanism of 4179 Toutatis-like elongated contact binary configuration
Hu, Shoucun
4179 Toutatis is a near-Earth asteroid with a bifurcated shape and an extremely slow tumbling rotation. The measurements from previous radar models and optical images acquired by Chang’e-2 spacecraft show that Toutatis has an elongated contact binary configuration, composed of two lobes (body and head), with the contact point located along the body’s long axis. We speculate that such configuration may have resulted from a low-speed impact between two components. In this work, we have performed a series of numerical simulations and further compared the results with the images captured by Chang’e-2, to examine the mechanism and better understand the formation of Toutatis. Herein we propose an scenario that an assumed separated binary precursor could undergo a close encounter with Earth, leading to an impact between the primary and secondary, and the elongation of the asteroid is caused by Earth’s tide. The precursor is assumed to be a doubly synchronous binary with a semi-major axis of 4 Rp (radius of primary) and two components are represented as spherical cohesionless self-gravitating granular aggregates. The mutual orbits are simulated in a Monte Carlo routine to provide appropriate parameters for our N-body simulations of impact and tidal distortion due to Earth. We employ the numerical package pkdgrav with a soft-sphere discrete element method (SSDEM) to explore the entire scenarios. The results show that contact binary configurations are natural outcomes under this scenario as long as using proper initial conditions, whereas the shape of the primary is almost not affected by the low-speed impact of the secondary. However, our simulations provide an elongated contact binary configuration best-matching to the shape of Toutatis at an approaching distance rp = 1.4 ~ 1.5 Re (Earth radius), indicative of a likely formation scenario for configurations of Toutatis-like elongated contact binaries.
White Light Flare Activities of Eclipsing Binary Systems in Kepler Field
Huang, Li-Ching
From 2009 to 2013, the Kepler space telescope obtained high-precision light curves of about 160,000 stars in a 115-square-degree field near Cygnus and Lyra. Among them, about 2800 eclipsing binary (EB) system were identified. The Kepler data are very useful in the study of large stellar flares that usually last half hour to 3 hours because of the availability of long-term light curves at 30-min cadence. Gao et al. (2016) found superflare events on 234 EBs. The primary stars of 66 of these Kepler EBs are G-type (Teff ~ 5340K-6040K), 69 are K-type (Teff ~ 3880K-5340K) and 7 are M-type (Teff ~ 2450K-3880K). It is interesting to note that 72.7% of the G-type EBs are detached Algol systems, 63.8 % of the K-type EBs are Algols, and for the M-type EBs, 100% are Algols. The EB light curves can be used to make a first estimate on the temperature ratios of the primary and secondary components from which their physical properties (i.e., radii and masses) can be derived according to stellar models. This method should be more accurate for the detached Algol systems. In this work, some preliminary results on the temperature ratio (T1/T2), radius radio (R1/R2) and mass ratio (q=m1/m2) of the 7 M-type EBs are discussed with a comparison to their corresponding flare activities.
On the origin of supergiant fast X-ray transients
Hubrig, Swetlana
A fraction of high-mass X-ray binaries are supergiant fast X-ray transients.These systems have on average low X-ray luminosities, but display short flaresduring which their X-ray luminosity rises by a few orders of magnitude. Theleading model for the physics governing this X-ray behaviour suggests that thewinds of the donor OB supergiants are magnetized. In agreement with this model,the first spectropolarimetric observations of the SFXT IGR J11215-5952 using theESO FORS2 instrument at the VLT indicate the presence of a kG longitudinalmagnetic field. Based on these results, it seems possible that the keydifference between supergiant fast X-ray transients and other high-mass X-raybinaries are the properties of the supergiant's stellar wind and the physics ofthe wind's interaction with the neutron star magnetosphere.
Studying the presence of magnetic fields in a sample of high-mass X-ray binaries
Hubrig, Swetlana
Previous circular polarization observations obtained with the ESO FORS1instrument at the VLT in 2007-2008 revealed the presence of a weak longitudinalmagnetic field on the surface of the optical component of the X-ray binaryCyg X-1, which contains a black hole and an O9.7Iab supergiant on a 5.6d orbit.In our poster we report on recently acquired FORS2 spectropolarimetricobservations of Cyg X-1 along with measurements of four additional high-massX-ray binaries.
Magnetic massive stars in star forming regions
Hubrig, Swetlana
One idea for the origin of magnetic fields in massive stars suggests that themagnetic field is the fossil remnant of the Galactic ISM magnetic field,amplified during the collapse of the magnetised gas cloud. A search for thepresence of magnetic fields in massive stars located in active sites of starformation led to the detection of rather strong magnetic fields in a few youngstars. Future spectropolarimetric observations are urgently needed to obtaininsights into the mechanisms that drive the generation of kG magnetic fieldsduring high-mass star formation.
An abundance analysis of AK Sco, a Herbig Ae SB2 system with a magnetic component
Hubrig, Swetlana
AK Sco is an SB2 system formed by two nearly identical Herbig Ae stars, withT_eff = 6500 K and log g = 4.5, surrounded by a circumbinary disk. This activelyaccreting system is of special interest among the pre-main-sequence binariesbecause of its prominent ultraviolet excess and the high eccentricity of itsorbit. Moreover, recent spectropolarimetric observations using HARPSpol indicatethe presence of a weak magnetic field in the secondary component. An abundanceanalysis of both components has shown that all elements have a solar abundancein the two stars, except for Li and Ba. These elements are enhanced by 2.2 and0.5 dex, respectively, in the A component and by 2.4 and 0.5 dex, respectively,in the B component.
ALMA Observations of Polarization from Dust Scattering in the IM Lup Protoplanetary Disk
Hull, Chat
We present 870 µm ALMA observations of polarized dust emission toward the Class II protoplanetary disk IM Lup. We find that the orientation of the polarized emission is along the minor axis of the disk, and that the value of the polarization fraction increases steadily toward the center of the disk, reaching a peak value of ~1.1%. All of these characteristics are consistent with models of self-scattering of submillimeter-wave emission from an optically thin inclined disk. The distribution of the polarization position angles across the IM Lup disk reveals that while the average orientation is along the minor axis, the polarization orientations show a significant spread in angles; this can also be explained by models of pure scattering. We compare the polarization with that of the Class I/II source HL Tau. A comparison of cuts of the polarization fraction across the major and minor axes of both sources reveals that IM Lup has a substantially higher polarization fraction than HL Tau toward the center of the disk. This enhanced polarization fraction could be due a number of factors, including scattering by larger dust grains in the more evolved IM Lup disk. However, our models yield similar maximum grain sizes for both HL Tau and IM Lup: on the order of 70 µm in both cases. This reveals continued tension between grain-size estimates from scattering models and from models of the dust emission spectrum, which find that the bulk of the (unpolarized) emission in disks is most likely due to millimeter (or even centimeter) sized grains.
Digital Archives as an Outreach Resource: The Role of the Observatory Librarian
Hunt, Sharon
Digital archives are an increasingly important resource for astronomy outreach in this digital age. They allow for the preservation and wide dissemination of the information found in images and documents and serve as an important knowledge repository for outreach professionals, research astronomers, and the public.Observatory librarians can play an important role in outreach activities through the creation and maintenance of these archives. To be useful, information must be organized, described, and made accessible. As specialists in the organization and retrieval of information, librarians offer many skills: familiarity with organizational schemes; practice describing materials through metadata, finding aids, and indexes; proficiency in assessing the needs of diverse communities; an understanding of individuals’ information-searching behaviors; and the capability to design effective user interfaces to databases.The National Optical Astronomy Observatory (NOAO) has a large collection of historical materials—reports, newsletters, photographs, films, correspondence, brochures, videos, guides—illuminating our nearly 60-year-long history and our programs. The observatory librarian in conjunction with outreach personnel is digitizing and organizing these visual and textual materials into digital archives accessible through our website. This digital archives project will enhance access to our informational materials and assist us in extending our outreach activities to diverse communities through digital means.
VLBA Imaging of ICRF 3 Sources
Hunt, Lucas
We present results from a Very Long Baseline Array (VLBA) campaign imaging sources used in the third realization of the International Celestial Reference Frame (ICRF 3). Imaging these sources allows us to determine spectral index, peak flux density, compactness and source structure index. This information is crucial to understanding source structure and variability which better allows us to determine if a source is suitable for inclusion in the ICRF and suitability as a phase reference calibrator.
The Evolution of Radio AGN in XXL-S
Huynh, Minh
The XXL is the largest survey ever with the XMM-Newton X-Ray telescope, comprising 6.9 MS spread over two 25 sq deg fields, the XXL-N and XXL-S. The main goals of the XXL project are to probe cosmology using galaxy clusters and to study galaxy evolution with a large sample of AGN. As part of the ongoing multiwavelength followup to achieve these science goals, radio observations at 2.1 GHz were obtained on the Australia Telescope Compact Array covering the full 25 sq deg of the southern field, XXL-S, reaching an rms noise of ~40 microJy with a resolution of ~5 arcsec. We identify 6287 radio sources down to 5 sigma over 25 sq deg, and find 4758 (75.7%) have an optical counterpart. Using a variety of multiwavelength diagnostics including X-Ray luminosities, MIR colours, SED fits, optical emission lines and radio luminosity, we classify the sources into three types: low-excitation radio galaxies (LERGs), high-excitation radio galaxies (HERGs), and star-forming galaxies (SFGs). We present AGN radio luminosity functions from the ATCA XXL-S for z = 0 to 1.3 and quantify the cosmic evolution of the LERG and HERG populations. Using scaling relations to convert radio jet power to kinetic energy, we also quantify radio-mode feedback across z = 0 to 1.3.
Mapping the Galaxy Distribution in and around Galaxy Clusters
Hwang, Ho Seong
Measurement of the mass distribution in galaxy clusters is an important test of structure formation models. Among many ways to map the matter distribution in clusters, three methods including galaxy redshift, weak lensing and X-ray surveys have been widely used. The three methods are complementary, and the combination of them is helpful for better understanding the assembly history of the cluster and understanding the systematics of each method. We present the results from extensive redshift surveys of nearby clusters focusing on the comparisons of galaxy distributions with the matter distributions from weak-lensing and/or X-ray surveys.
František Nušl, vicepresident of the IAU 1927-1935 and inventor of the circumzenithal telescope
Hyklová, Petra
The Czech astronomer František Nušl (1867-1951) was professor of mathematics, practical astronomy and geometrical optics at Prague Charles University. His scientific contribution to astronomy consisted mainly of inventing and constructing of new astronomical and geodetical instruments. Together with his friend Josef Jan Fric, founder of the Ondrejov Observatory, he developed and improved the circumzenithal telescope (1899-1903-1906-1922-1932), a portable instrument with a mercury horizon for determining the geodetic position using the Gauss method of equal altitudes. This instrument won the gold medal at the Exposition Internationale des Arts et Techniques dans la Vie Moderne in Paris in 1937. Nusl, independently on Ernst Öpik, invented the wobbling mirror for determining the velocity of meteors by visual observation, and constructed an unique guiding system for the Ondrejov astrograph etc. The organisational activities of Frantisek Nušl were considerably rich, too: He was one of the founders of the Czech Astronomical Society in 1917, in the years 1922-1948 he served as its president. From 1918 until his retirement in 1937 he was the director of the Ondrejov Observatory, 40 km south of capital city of Prague, lectured astronomy at the Prague university and held many popular lectures including regular courses in radio broadcasting. Frantisek Nušl was member of several commisions of international scientific unions; he organized the 3rd General Assembly of IUGG (International Union of Geodesy and Geophysics) in Prague 1927, and in IAU (International Astronomical Union) he was elected as Vice-President in the years 1928-1935. One can conclude that he was the main person who formed the Czech astronomy in the interwar period.
Students as Content Creators of Creative Astronomy Outreach
Ibrahim, Alaa
Outreach enriches education and lifelong learning, fulfills the broader impact of research, and strengthens the ties between educational/research institutes and their constituents, including society, alumni, and future students. Its impact includes motivating the next generations of scientists and engineers, enhancing STEM education outside traditional classroom setting, and being a catalyst to augmenting the science and technology workforce, a key factor to a competitive society. For nearly a decade and through project-based and community-based learning, students in introductory astronomy courses in Egypt become content creators of creative astronomy outreach material that are disseminated through visits to public schools, community centers, and during stargazing events. The projects range from building hands-on demonstrations to producing educational videos that communicate essential concepts in astronomy, challenge myths and misconceptions, and enhance the overall scientific literacy of the audience. The experience offers mutual benefit to students and the audience. Besides, it inspires new forms of activities that advance the practice of outreach itself, e.g. moving from Outreach 1.0 (Taking science events to the community at public) to Outreach 2.0 where the interaction between the outreach practitioners and the local community inspires new collaborative forms of outreach.References [1] The 95 Percent Solution, John H. Falk and Lynn D. Dierking, American Scientist 98(6):486493, 2010[2] Celebrating the Culture of Science, John Durant and Alaa Ibrahim, Science, Vol. 331, Issue 6022, pp. 1242, 2011[3] Bridging the Gap between Scientists and Society in the Arab World, Alaa Ibrahim, Nature Middle East, doi:10.1038[4] Our Community-Based Learning Projects, Vimeo.com/Science2Society
Student and Community Engagement in Astronomy Through Experiential Learning
Ibrahim, Alaa
Fulfilling the broader impact of research is an excellent opportunity for educational activities that connect scientists and society and enhance students and community engagement in STEM fields. Here we present the experience developed in this endeavor as part of our research and educational projects that introduced educational and outreach activities that included core curriculum course development for university students from various majors, community-based learning projects, citizen science and outreach programs to school students and community members. Through these activities, students worked with the project scientists on a variety of activities that ranged from citizen science and undergraduate research to running mass experiments and community awareness campaigns through the production of short documentaries and communicating them with stakeholders and target groups, including schools and TV stations. The activities enhanced students learning and the public awareness. It also connected effectively the project scientists with college and university students a well as wider segments of the society, which resulted in a host of benefits including better scientific literacy and appreciation to the role of scientists, promoting scientists as role models, sharing the values of science, and motivating future generations to pursue a career in science.
Is there a maximum mass for supermassive black holes?
Ichikawa, Kohei
Recent quasar surveys have revealed that supermassive black holes (SMBHs) rarely exceed a mass of MBH ~ a few * 1010 Msunduring the entire cosmic history. It has been argued that quenching of the BH growth is caused by a transition of a nuclear accretion disk into an advection-dominated accretion flow, with which strong outflows and/or jets are likely to be associated. We investigate the relationship between the maximum mass of SMBHs and the radio-loudness of quasars with a well-defined sample of ~ 105 quasars at a redshift range of 0 < z < 2, obtained from the Sloan Digital Sky Surveys DR7 catalog. We find that the number fraction of the radio-loud (RL) quasars increases above a threshold of MBH ? 2 x 109 Msun, independent of their redshifts. Moreover, the number fraction of RL quasars with lower Eddington ratios (out of all RL quasars), indicating lower accretion rates, increases above the critical BH mass. These observational trends can be natural consequences of the proposed scenario of suppressing BH growth around the apparent maximum mass of ~1010 Msun. The ongoing VLA Sky Survey in radio will allow us to estimate of the exact number fraction of RL quasars more precisely, which gives further insight into the quenching processes for BH growth.
Optical variations of selected LMXB and HMXB systems with neutron star
Icli, Tugce
Long-term and short-term photometric variation of the selected LMXBs and HMXBs with neutron star component are studied. We obtained new VRI observations of the selected systems by using 60cm Robotic telescope and 100cm telescope at the TÜBITAK National Observatory (TUG). We combined all the available observations of the systems with our new observations. Long- and short period light variation are discussed in this study.This study is supported by the Turkish Scientific and Research Council-TÜBITAK (117F118). We thank to TUBITAK for a partial support in using T100 and T60 telescope with project number 15AT60-776, 15CT100-916 and 17BT100-1204.
Optical variations of selected LMXB and HMXB systems with neutron star
Icli, Tugce
Long-term and short-term photometric variation of the selected LMXBs and HMXBs with neutron star component are studied. We obtained new VRI observations of the selected systems by using 60cm Robotic telescope and 100cm telescope at the TÜBITAK National Observatory (TUG). We combined all the available observations of the systems with our new observations. Long- and short period light variation are discussed in this study.This study is supported by the Turkish Scientific and Research Council-TÜBITAK (117F118). We thank to TUBITAK for a partial support in using T100 and T60 telescope with project number 15AT60-776, 15CT100-916 and 17BT100-1204.
Low Luminosity AGNs in the Local Universe
ikiz, tuba
Galaxies are known to contain black holes (e.g.Ferrarese & Merritt 2000), whose mass correlates with the mass of their bulge. A fraction of them also has an Active Galactic Nucleus (AGN), showing excess emission thought to be due to accretion of mass by the supermassive black hole at the center of the galaxy. It is thought that AGNs play a very important role during the formation of galaxies by creating large outflows that stop star formation in the galaxy (e.g. Kormendy & Ho 2013). The aim is to detect the fraction of Low Luminosity Active Galactic Nucleus (LLAGN) in the nearby Universe. At present, they are typically found using optical spectroscopy (e.g.Kauffmann, Heckman et al. 2003), who discuss the influence of the AGN on the host galaxy and vice versa. However, optical spectra are seriously affected by extinction in these generally very dusty objects, and therefore can only give us partial information about the AGN. I used a newly-found method, and apply it to the S4G(The Spitzer Survey of Stellar Structure in Galaxies) sample, a large, complete, sample of nearby galaxies, which I am studying in detail with a large collaboration, to detect the fraction of low luminosity AGNs, and to better understand the relation between AGNs and their host galaxy which is thought to be crucial for their formation. I will present the results of our study based on AGN fractions in nearby universe.
Titan’s polarization phase curves with Cassini/ISS
Ilic, Nikoleta
The sunlight reflected by Titan’s atmosphere is strongly polarized at phase angles near quadrature. This Rayleigh-like behavior has been a key clue for the understanding of the aggregate nature of Titan’s ubiquitous atmospheric haze. We are preparing Titan’s polarization phase curves with data collected with Cassini’s Imaging Science Subsystem. The Cassini/ISS dataset covers the spectrum from the UV to the NIR, and phase angles from nearly zero degrees (full illumination) to 150 degrees, thereby extending the observations made by the Voyager and Pioneer spacecraft decades ago. The Cassini/ISS dataset confirms the older trends in Titan’s polarization, but also shows new insight thanks to the relatively good phase sampling and to the availability of data at wavelengths affected by methane absorption. Since we now have spectrally-resolved phase curves in both brightness and polarization, we are investigating the optimal way to combine that information towards the optimal characterization of Titan’s atmosphere. The question is also relevant to the prospective characterization of exoplanets.
Binary nature of fast rotating Be star Pleione and the reflection to it's circumstellar disk evolution
Iliev, Lubomir
Pleione is a classical Be star well known with it’s cyclic transitions between Be-, shell- and normal B spectral phases.It’s nature as a binary system was discussed by McAlister et al. (1989), Gies et al. (1990), Luthardt & Menchenkova (1994) and Nemravova et al. (2010). We present results of the tracing the evolution of the dimensions of emitting regions of the circumstellar disk of Pleione connected with the binary nature of the star.
Early light curve of SN 1604 and constraints on its progenitor star system
Im, Myungshin
Type Ia supernova (SN Ia) is believed to occur due to the explosion of a white dwarf (WD) in a binary system. Yet, it is unclear if the companion star of the exploding WD is another WD or a non-degenerate star such as a main sequence or red giant star. Recently, the early light curve, the light curve one to two days within the explosion of SNe, is recognized as a powerful tool to estimate the size of the companion star. We apply this method on SN 1604, SN Ia, where an extensive daily light curve is available from Korean and European historical records. Our analysis shows that SN 1604 is a rather abnormal, faint SN Ia, and the early light curve is best explained with the presence of a companion star with the size of about 1 to 10 solar radius. This result suggests that SNe Ia with abnormal properties may originate from single degenerate binary systems.
Significant roles of accretion rings in X-ray binaries
Inoue, Hajime
X-ray light curves of three X-ray pulsars, Her X-1, LMC X-4 and SMC X-1, folded with their respective super-orbital periods, are shown to be well reproduced by a model that X-rays from a compact object towards us are periodically obscured by a precessing ring at the outermost part of an accretion disk around the central object. A situation is considered that matter from a companion star flows into a gravitational field of a compact star and initially forms a circular ring around the compact star under a balance between the centrifugal force and the gravitational force. A simple energetics-argument indicates that a precession of such a ring is possible to be excited. From the best fir parameters of the model fit to the super-orbital light curves, we see that the optical depth of the accretion ring is commonly around unity for Compton scattering and that the ring should suffer from a significant effect of X-ray heating from the central X-ray source. By considering why and how such an accretion ring is realized, the following evolution of the ring matter is suggested: Matter from the companion star initially forms a geometrically thick ring and accumulates there until the optical depth becomes around unity. Then, the matter in the thick ring gradually cools down under a balance between X-ray heating and radiative cooling, and shrinks to a geometrically thin ring at the cross section center of the ring. Angular momenta of the rotating matter are effectively transferred from the inside to the outside in the thin ring and the inside matter finally falls through a geometrically thin accretion disk towards the central compact object. This scenario on the outermost part of accretion disks can well explain several observational aspects of accreting X-ray binaries.
Spatially resolved emission line observations of galaxies at the reionization epoch
Inoue, Akio
One of the major science goals of extremely large telescopes (ELTs) is to explore the galaxy formation at the highest redshift. Emission lines from gasous nebulae in galaxies have a plenty of information about the physical and chemical conditions which are key ingredients to complete the galaxy formation theory. Especially, such information in a spatially resolved way is the Holy Grail. Therefore, every ELT will have its own integral-field spectroscopic instrument. Recently, we have successfully resolved the spatial distribution of far-infrared fine structure lines of [OIII] 88 micrion and [CII] 158 micron in a galaxy at z=7.15 with ALMA. Here, we present an emission line ratio map as a showcase for the future ELTs' integral-field spectroscopy targeting the rest-frame ultraviolet and optical emission lines in high-z galaxies.
Expansive Public Outreach in Thailand - Far and Wide
Insiri, Wichan
In Thailand, the network of astronomy has been a success as it has seen an expansive impact to the Thai society as a whole since the establishment of the National Astronomical Research Institute of Thailand (NARIT). We simply put the public as our priority. Innovation-driven economy is Thailand’s national agenda and astronomy has been one of the forces behind the success en route to the knowledge-based society. We have seen sharp increase in the awareness of science and technology as can be seen through the escalation of activities in relation to astronomy or even other fields of science and technology. This has also been felt through the surge of government’s spendings on research and development in science, technology and innovation in the past years. All combined, the climate of astronomy and its related fields together with public outreach and astronomy popularization have utilised all the resources in good use
An Origin of Accelerating Star Formation
Inutsuka, Shu-ichiro
Recent theoretical work on phase transition dynamics of ISM has shown that the formation of molecular clouds requires multiple episodes of supersonic compression. This finding enables us to create a scenario of molecular cloud formation as the interacting shells or bubbles in galactic scale. This picture naturally explains the accelerated star formation over many million years that was previously reported by stellar age determination in nearby star forming regions.
‘Intriguing’ scaling relations of dwarf irregular galaxies
Iorio, Giuliano
Scaling relations of galaxies represent an important benchmark for cosmological simulations and for theories of galaxy formation and evolutions. The properties of scaling relations for dwarf galaxies are still not well known due to the large uncertain on the estimate of dwarf properties. In this context, the kinematics of HI discs of dwarf irregular galaxies (dIrrs) represents a fundamental piece of information to explore certain scaling relations. Using robust estimates of the HI disc kinematics for a sample of 17 dIrrs, we present an analysis of three ‘intriguing’ scaling relations. We analysed the Baryonic Tully-Fisher relation and the Radial Acceleration Relation at the very low mass scales traced by dIrrs. We found that the relations found for the galaxies in our sample are compatible with what is found for more massive galaxies in contraposition with what is predicted by cosmological simulations. Finally, we found a clear correlation between the kinetic energy held in the HI turbulent motions and the star formation rate density of the dIrrs. Comparing this relation with the supernova explosions theories, we found that the turbulence in the HI discs can be sustained by the star formation activity assuming an average efficiency of about 30% in transferring the supernova explosions energy into the ISM.The results of this work represent relevant tests for galaxy formation theories and for cosmological simulations, moreover, they reveal the fundamental role of the star formation feedback in feeding the turbulence in the ISM.
Tidal fields and mass estimate of dSphs: the case of Sculptor
Iorio, Giuliano
The study of the dynamics of dwarf galaxies is one of the essential keys to understand their formation and their evolution. The dwarf spheroidal satellites of the Milky Way are close enough to be explored in details. In particular, it is possible to estimate the total matter content using the kinematics of the stars. The interpretation and the modelling of these data rely on equilibrium models in which we assume that the stellar kinematics is a genuine tracer of the galactic potential. However, these objects are orbiting in the tidal field of the Milky Way and it could be possible that the velocity dispersion is inflated by stripped stars along the line of sight. Therefore, the estimate of the dark matter content of these objects could be biased. In this talk, I will present detailed N-body simulations focused on the reproduction of the properties of the Sculptor dwarf spheroidal. Using the most recent and robust measurements of the proper motion of Sculptor and conservative assumptions on the Milky Way mass, we tuned the initial properties of the N-body realisation to reproduce the observed properties we see today. Finally, we analysed the final snapshot of the simulations as is done for real data.We found that, even in the worst case (closest epicentral passages), the kinematics of the stars in Sculptor is not affected by the tidal field of the Milky Way. Therefore, we conclude that the method commonly used to retrieve the mass in dwarf spheroidals are capable to return robust estimates of the total matter content of Sculptor.
The solar Lense-Thirring effect and BepiColombo
Iorio, Lorenzo
We analytically calculate the time series for the perturbations induced by a general disturbing acceleration on the mutual range and range-rate of two test particles A, B orbiting the same spinning body of mass M, angular momentum S, equatorial radius R and oblateness J2. We apply it to the general relativistic Lense-Thirring effect, due to the primary's spin S , and the classical perturbation arising from its quadrupole mass moment J2 for arbitrary orbital geometries and orientation of the source's symmetry axis. The Earth-Mercury range and range-rate are nominally affected by the Sun's gravitomagnetic field to the 10 m, 10-3 cm s-1 level, respectively, during the extended phase (2026-2028) of the forthcoming BepiColombo mission to Mercury whose expected tracking accuracy is of the order of about 0.1 m, 2 x 10-4 cm s-1. The competing signatures due to the solar quadrupole J2, if modelled at the 10-9 level of the latest planetary ephemerides INPOP17a, are nearly 10 times smaller than the relativistic gravitomagnetic effects.
Near-Earth object population and formation of lunar craters during the last billion of years
Ipatov, Sergei
We analyzed diameters of lunar craters in the region of the Oceanus Procellarum with age TOS<1.1 Gyr. The ratio rOS of the area of the considered region to the full surface of the Moon is 0.176. Based on the formula (16) from [1] we concluded that the diameter D of the crater that is produced by an impactor with a diameter di=1 km is 19.1 km and 18.4 km for the impact velocity equal to 19.3 km/s and 18 km/s, respectively. The number Nobs of craters with D greater than 18 or 19 km in the considered region is 49. The number N1 of near-Earth objects (NEOs) with diameter d>1 km is considered to be about 920. The characteristic time TE elapsed before a collision of a NEO with the Earth is estimated to be about 100 Myr (up to 120 Myr). The ratio pEM of probabilities of collisions of NEOs with the Earth to that with the Moon is about 20. Based on the above values we estimated the number of impacts of NEOs with d>1 km onto the considered lunar region as Nest=N1·rOS·TOS/(TE·pEM)˜920·0.176·1.1/(0.1·20)˜89. The ratio Nest/Nobs is 1.8. For greater values of TE and pEM, the ratio can be a little smaller, but probably it is still greater than 1.5. The above estimates show that the number Nobs of observed craters is less than the estimated number Nest, i.e. the mean value of TE·pEM calculated for the last billion of years could be greater than its present value, or N1 or TOS should be smaller for calculation of Nest. A recent catastrophic disruption of a large main-belt asteroid [2] could increase N1 compared to its mean value for a whole 1 Gyr interval. The difference in the values of Nest and Nobs can be also caused by that craters with a greater age less survive. Results of our analysis of the number of craters of different sizes are in accordance with the earlier conclusion that the number of impactors with a diameter d>Dp is proportional to Dp-2/3. [1] Werner S.C., Ivanov B.A. Treatise on Geophysics (Second Edition),2015,10,327–365. [2] Bottke W. et al. Nature, 2007,449,48-53
Formation of trans-Neptunian satellite systems at the stage of rarefied condensations
Ipatov, Sergei
The angular momenta used by Nesvorny et al. [1] as initial data in their calculations of contraction of condensations leading to formation of trans-Neptunian binaries could be acquired at collisions of two condensations that were moving before collisions in circular heliocentric orbits [2]. Initial angular momenta of condensations were not enough for formation of binaries. The parental condensation with radius close to its Hill radius that grew by accumulation of small objects could get the angular momentum at which a satellite system of a trans-Neptunian object could form. However, in this case the angular momentum of all satellite systems (e.g., binaries) would be positive. Actually about 40% of discovered trans-Neptunian binaries have negative angular momentum. Depending on heliocentric orbits of two colliding condensations, the angular momentum at their collision can be positive or negative. For the model of formation of binaries at the stage of rarefied condensations, I explained [3] the formation of prograde and retrograde rotation of discovered trans-Neptunian binaries, the inclinations of orbits of secondaries at different ratios of diameters of the secondary to the primary, the inclinations of orbits of secondaries at different orbital elements of heliocentric orbits of binaries, the separation distances at different heliocentric orbits, the orbits of binaries at different separation distances. The work was supported by the RFBR grant ? 17-02-00507 (angular momenta of condensations needed for formation of binaries) and by the Program of the Fundamental Studies of the Presidium of RAS N 28 as a part of Russian state program for GEOKHI N 00137-2018-0033 (origin of orbits of secondaries in binaries). [1] Nesvorny D. et al. Astron. J. 2010. 140. 785-793. [2] Ipatov S.I. Solar System Research. 2017. 51. 321-343. https://arxiv.org/abs/1801.05217. [3] Ipatov S.I. Solar System Research. 2017. 51. 409–416. https://arxiv.org/abs/1801.05254
Observing with CHEOPS: the CHEOPS Guest Observers Programme
Isaak, Kate
CHEOPS (CHaracterising ExOPlanet Satellite) is the first exoplanet mission dedicated to the search for transits of exoplanets by means of ultrahigh precision photometry of bright stars already known to host planets. It is the first S-class mission in ESA’s Cosmic Vision 2015- 2025. The mission is a partnership between Switzerland and ESA’s science programme, with important contributions from 10 other member states.Foreseen to be ready to launch at the very end of this year, CHEOPS will provide the unique capability of determining radii of planets in the super-Earth to Neptune mass range to 10% precision. It will also provide accurate radii for new planets discovered by the next generation of ground-based or space transit surveys (from super-Earth to Neptune-size). The high photometric precision of CHEOPS will be achieved using a photometer covering the 0.33 - 1.1um waveband, designed around a single frame-transfer CCD which is mounted in the focal plane of a 30 cm equivalent aperture diameter, f/5 on-axis Ritchey-Chretien telescope.20% of the observing time in the 3.5 year nominal mission will be available to the Community through the Guest Observers Programme that will be run by ESA. for the first year of observing will come out in Summer 2018.In this contribution I will give an overview of observing with CHEOPS, with a particular focus on the ESA-run CHEOPS Guest Observers Programme.
Dual-channel AGN feedback: the radiative-mode
Ishibashi, Wako
Two main modes of AGN feedback are known in nature: the radiative-mode and the jet-mode, which operate in different accretion states at different cosmic epochs. While jet-mode feedback has strong observational evidence, the radiative-mode is much more difficult to directly observe, due to obscuration. Yet, major progress has been made over the last few years, with powerful outflows on galactic scales being detected in radio-quiet AGNs. However, the physical mechanism actually driving the galactic outflows remains to be elucidated. We consider AGN feedback driven by radiation pressure on dust. We show that AGN radiative feedback can account for the observed outflow dynamics and energetics, provided that radiation trapping is properly taken into account. Such radiative feedback is capable of efficiently removing the obscuring dusty gas, and may thus provide a natural physical interpretation for the observed starburst-AGN co-evolutionary sequence. Furthermore, the propagation of radiation pressure-driven dusty outflows may even contribute to the metal enrichment of the circum-galactic medium. I will discuss how radiative-mode feedback may be equally important than jet-mode feedback in shaping the evolution of the host galaxy and surrounding environment.
Early Emission through Free Neutron Ejection in Binary Neutron Star Merger
Ishii, Ayako
Gravitational waves (GWs) from a binary neutron star merger (NSM) were observed by advanced LIGO and Virgo on August 2017 for the first time. Soon after the detection, electromagnetic follow-up observations were performed, and the electromagnetic counterpart was detected over the wide wavelength range. The first electromagnetic emission was detected at 10.9 h after the merger event. If the earlier emission from the NSM had been detected, it would have provided us with rich information about the NSM. For example, the ejected material from NSM may include free neutrons in the outermost layer. The layer might contribute the early emission through beta decay in a time scale of hours (Metzger et al. 2015). But the emission powered by decays of free neutrons is not fully understood because the existence of the free neutron layer was explored by smoothed particle hydrodynamics simulation with a small number of particles. We numerically investigate the possibility for the existence of the free neutron layer and the early emission through decays of free neutrons. We systematically study a wide parameter space of the size of the merging neutron stars and the energy involved in the shock waves. As a result, it is found that the mass of remaining free neutron is 10^{-7} to 10^{-6} Msun, which is smaller than the previously expected by more than two orders of magnitudes. This is due to the p(n, ?)d reaction, which was not taken into account in previous studies. We estimate that the total electromagnetic luminosity is about 4×10^{41} erg s^{-1} at ~30 min after the merger and that the emission has a peak in the ultraviolet wavelengths.
Growth of massive black holes in dusty clouds: impacts of relative velocity between dust and gas
Ishiki, Shohei
Recent observations have suggested the existence of a large amount of dust around supermassive black holes (SMBHs) in the early universe (e.g. Maiolino et al. 2004). In dusty clouds, the growth of black holes can be significantly regulated due to strong radiation force on dust grains. Yajima et al. (2017) recently showed that the accretion on to intermediate-mass black holes (IMBHs) in dusty clouds are significantly suppressed compared with dustless clouds because of the strong radiation force on dust grains. They, however, assumed that the dust and gas are completely coupled. This assumption might be invalid in the vicinity of black holes. The relative velocity between dust and gas is likely to have impacts on the accretion rate._x005F We here investigate the impacts of the relative motions of dust and gas on the accretion rate onto IMBHs with the mass of 105 Msun by using one-dimensional radiation hydrodynamic simulations in clouds with initial gas densities of nH = 10 and 100 cm-3. To investigate the effect of grain size on the gas accretion, we introduce two additional fluid components which describe large (0.1 μm) and small (0.01 μm) dust grains in the simulations as we did in Ishiki et al. (2018)._x005F We show that the accretion rate is reduced due to the radiation force. We show that the dust-to-gas mass ratio significantly changes in HII regions because of the relative motions of dust and gas. The decoupling of dust from gas alleviates the suppression of black hole growth compared with the complete coupling case. This effect may allow moderate growth of black holes even in dusty clouds.
How to ensure different organisations in different countries join forces to communicate one project
Isidro, Mathieu
The Square Kilometre Array (SKA) project is an international effort involving 20 countries on 5 continents to build the world’s largest radio telescope. One of its many challenges is coordinating a global communications effort to maximum effect and impact, both for the project as a whole and for its individual partners. With those partners in different timezones & continents with different interests, how do you ensure a joined-up approach across all project communications?Building on the theme of Finding Common Purpose and Implementing Coordinated Action, we will explore how we manage a global science & engineering partnership with communications colleagues spread over 20 timezones to best leverage local communications opportunities and support one another's strategic objectives while ensuring a strong brand and unified message for the project. Focusing on lessons learnt, we will discuss ways of working and workflows and highlight successes and challenges of some of the communication campaigns we have undertaken in the past five years.
Sunspot group tilt angles for cycles 19-24
Isik, Seda
The tilt angle of sunspot groups is an important quantity, as it determines the amount of signed flux transported to the solar poles. To date, however, there has been only a few observational studies on cycle-averaged tilt angles. Using the digitised archive of sunspot drawings produced at Kandilli Observatory, we measured group tilt angles for the period 1958-2017, and compared our results with the Mount Wilson (MWO), Kodaikanal (KSO) and Debrecen Photoheliographic (DPD) databases. The average shape of Joy's law as well as cycle-averaged tilt angles show similar trends with DPD. We found a much weaker anti-correlation of the mean tilt angle (normalised to latitude) with cycle strength than was reported using MWO and KSO data.
Emergence and surface transport of magnetic flux in Sun-like stars
Isik, Emre
Forward modelling of surface magnetism can be highly useful when interpreting photometric time series of Sun-like stars, as well as when reconstructing solar irradiance. We set up a theoretical framework based on the solar butterfly diagram, to study processes of flux emergence and transport on Sun-like stars. We take a semi-synthetic solar butterfly diagram of sunspot group emergence and map the emergence latitudes back to the base of the convection zone, using numerical simulations of rising flux tubes under the effects of stratification, drag force, and internal differential rotation. Transforming the base distribution to the surface for a given rotation rate, we determine the emergence latitudes and tilt angles of flux loops for the input rotation rate and activity level. Running a surface flux transport (SFT) model, we simulate the diffusive-advective evolution of the radial field at the surface. As the rotation rate increases, an inactive gap opens around the equator, reaching a half-width of 20º for 4 and 8 times the solar rotation rate. Between these two rotation rates, we find that polar spots start to form by accumulation of follower polarity flux. For 4 and 8 times the solar rotation rate, the cycle-averaged spot coverage becomes 2% and 10%, respectively, compared to the solar value of 0.2%, compatible with stellar observations.
Orbital resolved spectroscopy of GX 301-2: wind diagnostics
Islam, Nazma
GX 301-2, a bright high-mass X-ray binary with an orbital period of 41.5 days, exhibits stable periodic orbital intensity modulations with a strong pre-periastron X-ray flare. Several models have been proposed to explain the accretion at different orbital phases, invoking accretion via stellar wind, equatorial disc, and accretion stream from the companion star. From the orbital resolved spectroscopic study of GX 301–2 with the X-ray all sky monitor MAXI, we found a very large equivalent width of the iron line for a small value of the column density in the orbital phase range 0.10–0.30 after the periastron passage. The orbital dependence of the spectral parameters favours accretion on to the neutron star occurring via a high density accretion stream plus stellar wind of the companion. We further investigate the characteristics of the accretion stream with an ASTROSAT LAXPC and SXT observation of the system.
A curious case of HMXB 4U 1700-37
Islam, Nazma
4U 1700-37 is an eclipsing High Mass X-ray binary in a short orbital period of 3.412 days. In the absence of detectable pulsations, the orbital evolution is determined from the eclipse timing measurements, both from archival measurements as well as new measurements from long-term light curves obtained with the all sky monitors RXTE-ASM, Swift-BAT and MAXI-GSC. The orbital period decay rate of the system is estimated to be 10^{-7} /yr, smaller compared to its previous estimates. The mid-eclipse times and the eclipse duration measurements obtained from 10 years long X-ray light curve with Swift-BAT are used to separately put constraints on the eccentricity of the binary system and measure any apsidal motion. We carry out a deepest search for pulsations and Cyclotron Resonance Scattering Feature (CRSF) using a 40 kilosec ASTROSAT LAXPC observation. These results will provide some newer insights into the nature of the compact object, which is either a very high mass neutron star or a very low mass black hole.
SURFACE PHOTOMETRY OF PROPLYDS IN THE ORION NEBULA
Ismayilov, Nariman
The Orion Nebula (M42, NGC1976) is the unique space laboratory for studying of physical processes at the initial stage of starformation. Proplyds are small star-shaped objects that have comet-like forms which are consisting of the bright head and tail. In this report we present the results of studies of the structure of 11 proplyds located near the star θ1 OriC by using the surface photometry method. The observational material was taken from the archive MAST HST (https://archive.stsci.edu/hst/). CCD images were obtained with a resolution of 0.05" and in different filters. For research we have used the software MIDAS._x005F We studied the surface brightness distribution of proplyds along the axes, one of which passes through the head and tail (the Y axis), and the second through the brightest center and perpendicular to the first direction (the X axis). In all case, the spatial orientation of each axis was taken into account and their absolute sizes were determined. It is shown that the brightness along these axes shows non-linear bell-shaped distribution which can be descripted by 3 degree polynomial. For different proplyds, the maximum linear dimensions are reached from 60 to 200 AU along different axes. On average, the ratio of the linear sizes along these axes directions is obtained as Dy: Dx = 2: 1, i.e. the ratio of dimensions along the tail is twice large than in width._x005F A noticeable difference in the sizes of the prodlyds from the images obtained in different wavelength was found. For example, the linear sizes of proplyds in the blue band (λ 3870 Å) have a more asymmetric appearance and, on average, linear sizes, about 20-50% greater than the sizes in red band (λ 7727 Å). This indicates that the gas component matter around the proplyds is much larger than of the dust component.
Master light curve analysis of the Classic T Tauri type star DN Tau
Ismayilov, Nariman
The results of analysis of the summary light curve of the classical T Tauri star (CTTS) DN Tau, obtained from observations for over 50 years, are presented. It is shown that the amplitude of seasonal variations in brightness is ~ 0.5 mag. The average for year light curve shows long-time slow variations with a characteristic time of about 25 years._x005F The distribution of the brightness variations in the V and R bands is carried out a symmetric form, while asymmetry is observed in the U and B bands, which is occurred for often flare type increases in the brightness. The dependence of V brightness with color indexes B-V, U-B and V-R is well described in the simple cool spot model, where the temperature of the spot is lower by 800 K than the mean photosphere temperature of the star._x005F The dependence of the brightness V on the color indices B-V and V-R is well described in the cold spot model, at a spot temperature below 800 K from the temperature of the photosphere of the star. For different observation seasons, a difference in the value of the previously detected photometric period of 6.3 days was found within a few tenths of a day. For the average value of this period for different seasons 6.231 ± 0.089 days were obtained. The displacement the phases of minimum of this period were found from data of different observations seasons. In addition, two characteristic values of the steepness in the light curve are observed. In the first case, the brightness variation has a high speed, in the second case a relatively low rate of brightness changes with time. It is shown that the displacement of the phase of the period can arise because of migration of spots.
Proto-BCG candidates at z~4 by using HSC-SSP data
Ito, Kei
Brightest Cluster Galaxy (BCG) is the brightest and the most massive galaxy in a galaxy cluster. In nearby universe, BCGs are known to have distinguished characteristics compared to other cluster galaxies and field galaxies. Theoretical research predicts that most of the stellar mass was already formed at z~3 (De Lucia and Blaizot 2007); therefore, it is a key to find the progenitor of BCGs (proto-BCGs) at high-redshift in order to understand the formation of BCGs. However, it has been difficult to systematically study the high-z BCGs due to a small size of previous protocluster sample. Here, we report our survey of proto-BCGs candidates at z~4 by using Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We are ongoing the largest survey of high-redshift protoclusters to date by using imaging data produced by HSC-SSP. We constructed g-dropout galaxies catalog and found 179 protocluster candidates at z~4 (Toshikawa et al. 2018) over 121 square degrees. This is roughly ten times larger than any previous survey, enabling us, for the first time, to also construct a large sample of proto-BCGs. After removing contaminants (e.g. foreground galaxies or stars) which dominate bright-end, we identified 58 proto-BCGs candidates by 1) selecting the brightest member galaxy in each protocluster and 2) requiring the magnitude difference between the fifth and the first in a region is greater than 1.1 mag in i-band. Interestingly, members of protoclusters with proto-BCGs are found to be redder in (i-z), indicating that the dust extinction is more severe than that in field galaxies and members of protoclusters without proto-BCGs. This suggests that proto-BCGs may trace more developed structures than those without proto-BCGs. Also, we report the result of the morphological analysis in this poster.
VLT / KMOS view of the explosive outflow in Orion BL/KL
Itrich, Dominika
Orion BL/KL hosts a unique outflow containing more than 100 individual jets resembling those of young stellar objects. The directions of the jets strongly suggest an explosive origin linked to the decay of a non-hierarchical system of massive stars (Youngblood et al. 2016). Here, we present near-IR (1.4-2.4 µm) spectral maps of these "Orion fingers" using the K-band Multi Object Spectrograph (KMOS) at VLT. The H2 and [FeII] lines are used to determine gas physical conditions and dynamics. The observations reveal the properties of the shocks in this unique region at unprecedented detail.
Semi-analytical theory of the axially symmetrical Moon's rotation
iVANOVA, TAMARA
In the present paper the trigonometric theory of the rigid-body axially symmetrical Moon's rotation is constructed in the framework of the general planetary theory avoiding the non-physical secular terms and involving the separation of the long-period and short-period angular variables, both for planetary-lunar motions and Moon's rotation. The combined system of the equations of motion for the principal planets and the Moon and the equations of the Moon's rotation is reduced to the autonomous secular system describing the evolution of the planetary and lunar orbits independent of the Moon's rotation and the evolution of the Moon's rotation depending on the orbital planetary and lunar evolution. The secular system is solved in the trigonometric form. As a result, the theory of the axially symmetrical Moon's rotation is presented by means of the power series in evolutionary variables withquasi-periodic coefficients in mean longitudes of the planets and the Moon. All analytical calculations were performed by means of the Poisson series processor.
GC58 Constraints on the dark matter core inside the neutron stars
Ivanytskyi, Oleksii
We study a compatibility of the dark matter condensation inside the neutron stars with the observational constraints on the properties of these astrophysical objects. Effects of the baryon-lepton matter are taken under control based on the well tested novel equation of state of nuclear matter, which is able to fulfill a rich collection of constraints from nuclear physics and heavy ion collision experiments. Considering the dark matter as a free Fermi gas coupled to usual matter only by gravity we explicitly introduce mass and quantum mechanical degeneracy of these particles to the problem. Integration of the Tolman-Oppenheimer-Volkoff equation allows us to obtain the mass-radius diagram of neutron stars for different concentrations of dark matter particles and their masses from 100 MeV to 1 TeV. We argue, that concentrations of the dark matter typical for the Milky Way galaxy do not allow its particles to be heavier than about 100 GeV. This result can serve as a constraint for beyond the Standard Model theories aiming to explain the dark matter nature in terms of WIMPs.
Dusty plasma effects in the atmosphere of Mars and near the Martian Surface
Izvekova, Yulia
Dusty plasma effects in the Martian atmosphere are discussed. A specific feature of the Martian atmosphere is the presence of dust grains in a wide range of altitudes. Taking into account the presence of the Martian ionosphere and the high conductivity of the medium at lower altitudes, the appearance of plasma systems in the Martian atmosphere can be considered quite a common phenomenon. Special attention is paid to Dust Devils that frequently form in the Martian atmosphere and can efficiently lift dust grains. The processes of dust grain charging as a result of triboelectric effect and generation of electric fields in a Dust Devil are discussed. The dynamics of dust grains in such a vortex is simulated with allowance for their charging and the generated electric field._x005F This work was supported by the Russian Foundation for Basic Research (project no. 18-02-00341).
Can the brightest stellar explosions be triggered by gas inflows ?
Izzo, Luca
The advent of integral-field unit spectrographs allowed us to analyse with great details the galaxies and the direct environment where the brightest stellar explosions, like GRBs and SLSNe, formed and evolved. Long-time observations have revealed that GRBs and SLSNe form in the lowest-metallicity regions of their hosts. At same time, the inflow of pristine gas can enrich the galaxy environment of low-metallicity gas and also trigger burst of star-formation rate. Presence of this pristine gas can also be inferred from HI radio observations, as well as in the distribution of the brightest star-forming regions in host galaxies. We present some evidences for the possible presence of gas inflow interactions in some host galaxies, concentrating on the specific cases of GRB 100316D and SLSN 2017egm.
OGLE-ing the Magellanic System: Three-Dimensional Structure
Jacyszyn-Dobrzeniecka, Anna
I will present a three-dimensional structure of the Magellanic System using over 9000 Classical Cepheids (CCs) and almost 23000 RR Lyrae (RRL) stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample we were able to study the Magellanic System in great details.Lately, we have very carefully studied once again the distribution of both types of pulsators in the Magellanic Bridge area. We showed that there is no evidence of an actual physical connection between the Clouds in RRL stars distribution. We only see the two halos overlapping. There are few CCs in the Magellanic Bridge area that seem to form a genuine connection between the Clouds. Their on-sky locations are very well correlated with young stars and neutral hydrogen distribution.CCs in the LMC are situated mainly in the bar that shows no offset from the galaxy plane. The norther arm is also very prominent. Moreover, it is located closer to us than the entire sample. The CCs in the SMC have a non-planar distribution that can be described as an ellipsoid extended almost along the line of sight. RRL stars revealed a very regular distribution in both Magellanic Clouds. We fitted triaxial ellipsoids to our LMC and SMC RRL samples.
OGLE-ing the Magellanic System: Three-Dimensional Structure
Jacyszyn-Dobrzeniecka, Anna
I will present a three-dimensional structure of the Magellanic System using over 9000 Classical Cepheids (CCs) and almost 23000 RR Lyrae (RRL) stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample we were able to study the Magellanic System in great details.Lately, we have very carefully studied once again the distribution of both types of pulsators in the Magellanic Bridge area. We showed that there is no evidence of an actual physical connection between the Clouds in RRL stars distribution. We only see the two halos overlapping. There are few CCs in the Magellanic Bridge area that seem to form a genuine connection between the Clouds. Their on-sky locations are very well correlated with young stars and neutral hydrogen distribution.CCs in the LMC are situated mainly in the bar that shows no offset from the galaxy plane. The norther arm is also very prominent. Moreover, it is located closer to us than the entire sample. The CCs in the SMC have a non-planar distribution that can be described as an ellipsoid extended almost along the line of sight. RRL stars revealed a very regular distribution in both Magellanic Clouds. We fitted triaxial ellipsoids to our LMC and SMC RRL samples.
Magnetic fields along the pre-main sequence: new magnetic field measurements of Herbig Ae stars using high resolution HARPS spectropolarimetry
Jaervinen, Silva
Herbig Ae/Be-type stars are analogs of T Tauri stars at higher masses. Since the confirmation of magnetospheric accretion using Balmer and sodium line profiles in the Herbig Ae star UX Ori, a number of magnetic studies have been attempted, indicating that about 20 Herbig Ae/Be stars likely have globally organized magnetic fields. The low detection rate of magnetic fields in Herbig Ae stars can be explained by the weakness of these fields and rather large measurement uncertainties. The obtained density distribution of the root mean square longitudinal magnetic field values revealed that only a few stars have magnetic fields stronger than 200G, and half of the sample possesses magnetic fields of about 100G or less. These results call into question our current understanding of the magnetospheric accretion process in intermediate-mass pre-main sequence stars, as they indicate that the magnetic fields of Herbig Ae/Be stars are by far weaker than those measured in their lower mass classical T Tauri star counterparts, usually possessing kG magnetic fields. We report on the results of our analysis of a sample of presumably single Herbig Ae/Be stars based on recent observations obtained with HARPSpol attached to ESO's 3.6m telescope. Knowledge of the magnetic field structure combined with the determination of the chemical composition are indispensable to constrain theories on star formation and magnetospheric accretion in intermediate-mass stars. As of today, magnetic phase curves have been obtained only for two Herbig Ae/Be stars, HD101412 and V380 Ori.
Studying the accretion geometry of X-ray pulsar GX 1+4 in a peculiar state
Jaisawal, Gaurava K
We present detailed spectral and timing studies using a NuSTAR observation in 2015 October of GX 1+4 during an intermediate intensity state. The measured spin period of 176.778 s is found to be one of the highest value since its discovery. In contrast to a broad sinusoidal-like pulse profile, a peculiar sharp peak was observed in profiles below 25 keV. The profiles at higher energies were found to be significantly phase-shifted to the soft X-ray profiles. Broadband energy spectra of GX 1+4, obtained from NuSTAR and Swift observations, were described with various continuum models. Among these, a two component model consisting of a bremsstrahlung and a blackbody component was found to best-fit the phase-averaged and phase-resolved spectra of the pulsar. Physical models were also used to investigate the emission mechanism in the pulsar. Based on the results obtained from fitting physical models to the data, the magnetic field strength of GX 1+4 was estimated to be in ~(5--10)x10^12 G range. Phase-resolved spectroscopy of NuSTAR observation showed a strong blackbody emission component in a narrow pulse phase range. This component was interpreted as the origin of the peculiar peak in the pulse profiles below 25 keV. The size of emitting region was calculated to be ~400 m. The bremsstrahlung component was found to dominate in hard X-rays and explains the nature of simple profiles at high energies.
Magnetic and kinematic characteristics of very fast CMEs in 24th solar cycle
Jang, Soojeong
It is important to understand very fast CMEs which are the main cause of geomagnetic storms and solar particle events (SPEs). During this solar cycle 24, there are 10 very fast CMEs whose speeds are over 2000 km/s. Among these, there were only two front-side events (2012 January 23 and 2012 March 7) and they are associated with two major flares (M8.7 and X5.4) and the strongest SPEs (6310 pfu and 6530 pfu). They have similar characteristics: there were successive CMEs within 2 hours in the same active region. We analyze their magnetic properties using SDO HMI magnetograms and kinematic ones from STEREO EUVI/COR1/COR2 observations. We can measure their speeds and initial accelerations without projection effects because their source locations are almost the limb. Additionally, we are investigating magnetic and kinematic characteristics of 8 backside events using AI-generated magnetograms constructed by deep learning methods.
Rotating stellar populations and morphology analysis in dSph galaxies, possible hints to understand their formation and evolution.
Jara, Alex
According to the Lambda-CDM cosmological model, dwarf spheroidal (dSph) galaxies are the basic building blocks for the formation of bigger structures, because of their high velocity dispersions and low luminosities, they are thought to be the most dark matter (DM) dominated objects in the universe. There are several models that attempt to explain their formation and evolution invoking two body interactions, e.g., resonant stripping or tidal stirring, but they have difficulty explaining the formation of isolated dSph galaxies. Another formation scenario is the dissolving star cluster model (Assmann et al. 2013, Alarcon et al. 2017), according to this model dSph galaxies were formed by the fusion and dissolution of several star clusters (SCs) formed in a giant molecular gas cloud within a DM halo. Simmulations predict kinematic substructures formed by stars following similar orbits and clumps of stars formed for star cluster which were not entirely dissolved. In this work we will compare simulations of the dissolving star cluster model with observational data.
Heating mechanisms in accretion disks around young stellar objects
Jatenco-Pereira, Vera
Accretion disks are observed around young stellar objects such as T Tauri stars. In order to complete the star formation, particles in the disk need to loose angular momentum in order to be accreted into the central object. The magneto-rotational instability (MRI) is probably the mechanism responsible for a magneto-hydrodynamic (MHD) turbulence that leads to disk accretion, which implies the disk particles to be coupled with the magnetic filed lines. As the temperatures of the particles in the disk are low, the ionization rates are also very small. In order to increase the disk temperature, besides the viscous heating mechanism often included in the models by means of the alpha-prescription, we study the damping of magneto-acoustic waves and the damping mechanisms of Alfvén waves, the turbulent and non-linear, as an additional heating source. We show that these damping mechanisms can increase the ionization fraction, making possible the presence of the MRI in a large part of the disk. In particular, the mechanism derived that couples the turbulent and non-linear damping mechanisms of Alfvén waves proved to be very efficient, generating temperatures almost one order of magnitude higher than those mechanisms considered independently.
Chemical evolution of water in the protostellar environment
Jensen, Sigurd
Understanding the evolution of water during star formation, from the molecular cloud down to the circumstellar disk, is a central goal of astrochemistry.Open questions on this topic are how the water content is influenced by the local environment in which the protostar is formed, whether water is inherited directly from the molecular cloud and what role local processing during the cloud collapse plays for the water in the protoplanetary disk.We focus on the deuteration of water (HDO/H2O and D2O/HDO) as a tracer for the physical and chemical evolution of water around young protostars.We investigate the effects of the inhomogeneous star formation process by studying the formation of several hundred protostars in a realistic 3D MHD simulation of a molecular cloud from pc to tens of AU scales.For each of these protostars, we have large number of tracer particles available which track the gas flow providing the physical evolution of the material. On these particles, we evolve the chemical network from pre-collapse conditions down to the scales of the protostellar disk in a 3-phase model which includes both gas, surface and mantle species and track the buildup of ices species layer by layer.The theoretical results will be combined with incoming high-resolution ALMA observations of water and its isotopologues around young protostars. With the combination of an increased observational and theoretical sample we aim to pinpoint the important steps in the evolution of water and constrain the origin of water in the Solar System.
The measurements of beam efficiency, size, and shape of TRAO 13.7-m Radio Telescope
Jeong, Il-Gyo
We introduce performance and capability of the 13.7-m Taeduk Radio Astronomy Observatory (TRAO) telescope. Recently, TRAO was equipped with the new receiver, SEQUOIA-TRAO, consisting of high performing 16-pixel focal plane array with the operating frequency range from 86 to 115 GHz. The radome is the considerable factor that affects the frequency dependent efficiency of the telescope . The 30 years old radome that has been worn out went through weathering is switched to the new radome in 2017. In order to measure the beam size and efficiency of the TRAO, we executed the continuum observation of Jupiter at 86, 98, 110 and 115 GHz with the On-The-Fly mapping mode in 2016. Moreover, we repeated the continuum observation in order to determine the influence of the radome in 2017. The full width half maximum of the beam size were measured to be about 60’’ and 47’’ at 86 and 115 GHz. The measured aperture efficiencies are 31, 35, 39, and 36 % in 2016, and 43, 42, 37, and 33 % in 2017, respectively. The main-beam efficiencies are 37, 42, 49, and 46 % in 2016, and 45, 48, 46, and 41 % in 2017, respectively. We also present the molecular line spectra of each frequency toward the Orion-KL and IRC10216.
A photometric study of KIC 8682849 showing strong variations in the period and light curve
Jeong, Min-Ji
We report a photometric study of KIC 8682849 based on the high precision data observed continuously for about 4 years by the Kepler mission. KIC 8682849 is a W UMa-type binary star with a short orbital period of 0.352 d. It shows strong variations of light curve as well as an anti-correlated pattern between the primary and secondary times of minima. Period-searches were tried to find any periodicities in the variations of light curve and the anticorrelated patterns. We found that both variations show to be quasi-periodic and have nearly the same period of about 77 days. Based on the results, a symmetric light curve mostly free from the variations of light curve and anti-correlation was chosen and solved with the 2015 Wison-Devinney binary model. It was found that KIC 8682849 is the over-contact binary system with an extremely low mass ratio and a deep fill-out factor. The rest asymmetrical light curves were modelled only with spot parameters to track the time-migrations of spot position on the surface of larger and hotter components. The modelled properties of the time-varying spots are discussed.
CO molecular line observations of HII region G84.9+0.5
Jeong, Il-Gyo
We present the results of the multiple transitions of CO molecular line observations toward the Galactic HII region G84.9+0.5. The low transition 12CO and 13CO molecular line observations are executed with the Taeduk Radio Astronomy Observatory (TRAO) 13.7-m radio telescope in order to explore the distributions of molecular clouds and search for the star-forming activity along the H II region. We mapped 20’ x 20’ area with On-The-Fly mapping mode of the TRAO to cover the whole area of H II region. Several molecular clumps are detected in the vicinity of the H II region, and the velocity component at ~-41 km/s these clumps seem to strongly correlated with the H II region spatially. The estimated kinematic distance toward the H II region is about 5.5 kpc. Thus, 12CO J=3-2 molecular line observation was performed in order to investigate the spatial correlation between these clumps and the H II region G84.9+0.5. The observation results indicate that the molecular cloud distributions are well matched along the H II region identified as the distinct ring-like morphology with a small radius (~3'). The infrared images from Spitzer and Herschel clearly show the ring-like H II region shape and the point sources are associated with molecular dense clumps. At the northern part of the H II region, we were able to detect the broadened CO velocity profiles might imply the existence of the young stellar objects as well as the outflow feature. We show the detailed observation results and present the characteristics and properties of the HII region G84.9+0.5.
NIR Color–Metallicity Relations and Color Distributions of Globular Cluster system in Elliptical Galaxy NGC 4649 with Subaru/MOIRCS
Jeong, Jong-Hoon
We present Subaru Near-Infrared (NIR) photometry for the globular cluster (GC) system in NGC 4649 (M60), the giant elliptical galaxy belonging to the Virgo cluster. NIR data are obtained in Ks - band with the Subaru/MOIRCS, and HST/ACS and Gemini/GMOS optical data available in the literature are used to investigate the origin of GC color bimodality in early-type galaxies. A clear bimodal color distribution is observed in the optical colors g475 – z850 and g'– i', and this bimodality is commonly considered as evidence for the presence of two GC subpopulations with different metallicities. By contrast, the more metallicity-sensitive Opt-NIR colors such as z850 – Ks and i'– Ks show a considerably weakened or no bimodality in their distributions. Furthermore, color–color relations of the optical and Opt-NIR colors for the NGC 4649 GC system exhibit a nonlinear feature. Our results support the recent claim that the optical color bimodality observed in GC systems of early-type galaxies is caused by the nonlinear nature of their color–metallicity relations.
S-type planets formation in close binaries: scattering induced tidal capture of circumbinary planets
JI, Jianghui
Although several S-type and P-type planets in binary systems were discovered in past years, S-type planets have not yet been found in close binaries with a separation not more than 5 au. Recent studies suggest that S-type planets in close binaries may be detected using the current high-accuracy radial velocity (RV) and photometric measurements. However, current planet formation theories generally suggest that it is difficult for S-type planets in close binaries systems to form in situ. In this study, we extensively perform numerical simulations to explore the scenarios of planet-planet scattering among circumbinary planets and subsequent tidal capture in various binary configurations, to examine whether the mechanism can play a part in producing such kind of planets. The maximum capture probability is approximately %10, which can be comparable to the tidal capture probability of hot Jupiters in single star systems. The capture probability is related to the binary configuration, where a smaller eccentricity or a low mass ratio of the binary will lead to a larger probability of capture, and vice versa. Furthermore, we find that the S-type planets with retrograde orbits can be naturally produced during capture process. These planets on retrograte orbits can help us distinguish in situ formation and post-capture origin of S-type planet in close binaries systems. The forthcoming missions such as PLATO will provide the opportunity and feasibility to detect these planets. Our work provides several suggestions for selecting target binaries to search S-type planets in the near future according to the investigation.
A Small UV mission CAFE for Warm Baryons in Nearby Universe
Ji, Li
We will present the current status of the on-going research project, a small UV mission CAFE both scientifically and technically. CAFE was proposed for UV line emission mapping for IGM and nearby galaxies, which will investigate those filaments connecting the galaxies and the large-scale structure of the Cosmic Web, and make the first maps of the three-dimensional structure of the dense part of the 104and 105K WHIM, and of the accretion and feedback flows around galaxies.
The YSZ,Planck -YSZ,XMM scaling relation and its difference between cool-core and non-cool-core clusters
JIA, Shumei
We construct a sample of 70 clusters using data from XMM-Newton and Planck. YSZ,XMM is calculated by accurate de-projected temperature and electron number density pro?les derived from XMM-Newton. YSZ,Planck is the latest Planck data restricted to our precise X-ray size ?500. To study the cool-core in?uences on YSZ,Planck -YSZ,XMM scaling relation, we apply two criteria, limits of central cooling time and classic mass deposition rate, to distinguish cool-core clusters (CCCs) from non-cool-core clusters (NCCCs). We also use YSZ,Planck from other papers, which are derived from di?erent methods, to con?rm our results. The intercept and slope of the YSZ,Planck -YSZ,XMM scaling relation are A = -0.86±0.30, B = 0.83±0.06. The intrinsic scatter is sins = 0.14±0.03. The ratio of YSZ,Planck/YSZ,XMM is 1.03±0.05, which is perfectly agreed with unity. Discrepancies of YSZ,Planck -YSZ,XMM scaling relation between CCCs and NCCCs are found in observation. They are independent of cool core classi?cation criteria and YSZ,Planck calculation methods, although discrepancies are more signi?cant under the classi?cation criteria of classic mass deposition rate. The intrinsic scatter of CCCs (0.04) is quite small compared to that of NCCCs (0.27). The ratio of YSZ,Planck/YSZ,XMM for CCCs is 0.89±0.05, suggesting that CCCs YSZ,XMM may overestimate SZ signal. By contrast, the ratio of YSZ,Planck/YSZ,XMM for NCCCs is 1.14±0.12, which indicates that NCCCs YSZ,XMM may underestimate SZ signal.
On the silicate crystallinities of oxygen-rich evolved stars and their mass-loss rates
Jiang, Biwei
For decades ever since the early detection in the 1990s of the emission spectral features of crystalline silicates in oxygen-rich evolved stars, there is a long-standing debate on whether the crystallinity of the silicate dust correlates with the stellar mass-loss rate. To investigate the relation between the silicate crystallinities and the mass-loss rates of evolved stars, we carry out a detailed analysis of 28 nearby oxygen-rich stars. We derive the mass-loss rates of these sources by modelling their spectral energy distributions from the optical to the far-infrared. Unlike previous studies in which the silicate crystallinity was often measured in terms of the crystalline-to-amorphous silicate mass ratio, we characterize the silicate crystallinities of these sources with the flux ratios of the emission features of crystalline silicates to that of amorphous silicates. This does not require the knowledge of the silicate dust temperatures, which are the major source of uncertainties in estimating the crystalline-to-amorphous silicate mass ratio. With a Pearson correlation coefficient of -0.24, we find that the silicate crystallinities and the mass-loss rates of these sources are not correlated. This supports the earlier findings that the dust shells of low mass-loss rate stars can contain a significant fraction of crystalline silicates without showing the characteristic features in their emission spectra.
Binary evolution and double sequences of blue stragglers in globular clusters
Jiang, Dengkai
Double sequences of blue stragglers in the color-magnitude diagram of globular clusters are important to study the formation mechanisms of blue stragglers. We study the formation of blue stragglers from binary evolution. We find the location of a blue-straggler binary produced by mass transfer in binary systems depends on the contribution of the mass donor to the total luminosity of the binary, because two components of this binary system cannot be distinguished. In the blue sequence, the blue-straggler binaries have a blue straggler orbiting a cool white dwarf. However, the red sequence include blue-straggler binaries that are experiencing mass transfer, or just terminating mass transfer, and the blue-straggler binaries that the blue stragglers have evolved away from the blue sequence. We suggest that mass transfer in binary systems can contribute to the blue stragglers in both of the sequences in globular clusters.
Application of 1-m class telescopes network in time domain astronomy
Jiang, Xiaojun
We collect the specifications, performance, and locations of the 1-m class telescopes in China. We further investigate the scientific goals suitable for the network/clusters of these telescopes, including time series observations, coordinated photometric and/or spectroscopic observations using multiple telescopes in different observation modes at the same or different sites. The strategy and solution for the coordinated observations is given.
OBSERVATIONS OF 01 SEPTEMBER 2016 ANNULAR SOLAR ECLIPSE FROM TANZANIA
JIWAJI, NOORALI
The major astronomical event of an Annular Solar Eclipse that crossed through the heart of Africa on September 01, 2016 was used as an outreach, educational, and scientific opportunity in Tanzania. We present the challenges of organising, funding and reaching the population and educating the public as well as students in schools across the country. We also present findings of global solar radiation and temperature changes monitored during the eclipse. Results show a practically night sky situation during full annularity and a nearly 4oC drop in air temperature at full eclipse.
Global distribution of far-ultraviolet emission from the highly ionized gas in the Milky Way
Jo, Young-Soo
One of the keys to interpreting the characteristics and evolution of interstellar medium in the Milky Way is to understand the distribution of hot gas (105–106 K). Gases in this phase are difficult to observe because they are in low density and lack of easily observable tracers. Hot gases are observed mainly in the emission of the FUV (912—1800 Å), EUV (80—912 Å), and X-rays (T>106 K) of which attenuation is very high. Of these, FUV emission lines originated from high-stage ions such as O VI and C IV can be the most effective tracers of hot gases. To determine the spatial distribution of O VI and C IV emissions, we have analyzed the spectra obtained from FIMS (Far-ultraviolet IMaging Spectrograph), which covers about 80 percent of the sky. The hot gas volume filling factor, which varies widely from 0.1 to 0.9 depending on the supernova explosion frequency and the evolution model, has been calculated from the O VI and C IV maps. The hot gas generation models has been verified from the global distribution of O VI and C IV emissions, and a new complementary model has been proposed in this study.
The HI Neighborhoods Around STARBIRDS
Johnson, Megan
Starbursts are finite periods of intense star formation (SF) thatcan dramatically impact the evolutionary state of a galaxy.Recently, published results have redefined both the duration and spatialextent of starbursts in dwarf galaxies to be longer and more distributedthan previously thought, with star formation efficiencies (SFEs) comparableto spiral galaxies. The contrast between these SFEs and those typical ofnon-bursting dwarfs highlights the inconsistencies between two SF modes thatcan operate in low-mass galaxies. These inconsistencies might beexplainable if the starburst mode of SF is externally triggered bygravitational interactions with other nearby systems. We present new,sensitive neutral hydrogen observations of 18 starburst dwarf galaxies,which are part of the STARburst IRregular Dwarf Survey (STARBIRDS) and eachwere mapped with the Green Bank Telescope (GBT) and/or Parkes Telescope inorder to study the low surface brightness gas distributions, a common tracer for tidal interactions.
Planetary cores, their energy flux relationship, and its implications
Johnson, Prof. Fred M.
Integrated surface heat flux data from each planet in our solar system plus over 50 stars, including our Sun, was plotted against each object’s known mass to generate a continuous exponential curve at an R-squared value of 0.99. The unexpected yet undeniable implication of this study is that all planets and celestial objects have a similar mode of energy production. It is widely accepted that proton-proton reactions require hydrogen gas at temperatures of about 15 million degrees, neither of which can plausibly exist inside a terrestrial planet. Hence, this paper proposes a nuclear fission mechanism for all luminous celestial objects, and uses this mechanism to further suggest a developmental narrative for all celestial bodies, including our Sun. This narrative was deduced from an exponential curve drawn adjacent to the first and passing through the Earth’s solid core (as a known prototype). This trend line was used to predict the core masses for each planet as a function of its luminosity.
Stellar Activity Indicators in the CARMENES Sample
Johnson, Erik
Stellar activity has long been a source of irritation for exoplanet surveys as the radial velocity signal from the stellar activity is on the same order of magnitude as that from terestrial planets in their habitable zones. This is especially true for the M-type stars in the CARMENES survey. Statistical methods can alleviate some of the effects but require extensive-and costly- data sets to work. Understanding and relating the signals of stellar activity through chromospheric and photospheric indicators is vital to deconvolving the planetary radial velocity signal from the stellar activity signal.
The Influence of Chemical Composition on Planetary Upper Atmospheres and Atmospheric Losses
Johnstone, Colin
The thermal and chemical structures of the upper atmospheres of planets are very important for determining how quickly atmospheric gas is lost to space. These structures are determined by a range of processes, including heating by stellar radiation, especially in X-ray and UV wavelengths, and cooling by IR radiation from molecules such as carbon dioxide. The importance of each of the relevant mechanisms depends sensitively on the atmospheric composition. In this talk, I will discuss different atmospheric chemical compositions, and how they influence the atmospheric heating and cooling. I will link this to atmospheric loss mechanisms and long term atmospheric evolution.
Dust producing AGB stars in the Metal-poor, Dwarf Irregular Galaxies Sextans A and Leo A
Jones, Olivia
We present JHK s observations of the metal-poor ([Fe/H] < -1.40) dwarf-irregular galaxies, Leo A and Sextans A, obtained with the WIYN High-resolution Infrared Camera at Kitt Peak. Their near-IR stellar populations are characterized by using a combination of color–magnitude diagrams and by identifying long-period variable stars. We detected red giant and asymptotic giant branch stars, consistent with membership of the galaxy’s intermediate-age populations (2–8 Gyr old). Matching our data to broadband optical and mid-IR photometry, we determine luminosities, temperatures, and dust-production rates (DPR) for each star. We identify 32 stars in Leo A and 101 stars in Sextans A, confirming that metal-poor stars can form substantial amounts of dust. We also find tentative evidence for oxygen-rich dust formation at low metallicity, contradicting previous models that suggest oxygen-rich dust production is inhibited in metal-poor environments. The majority of this dust is produced by a few very dusty evolved stars and does not vary strongly with metallicity
Characterizing SZ and X-ray Selected Samples of Clusters of Galaxies
Jones, Christine
Using Chandra observations, we compare the cluster masses and fractions of cool core clusters in X-ray and SZ selected cluster samples. In particular, we analyzed 164 clusters (z<0.35) from the Planck Early SZ sample and 100 clusters from a flux-limited X-ray sample (z<0.3). We find that cluster mass determinations derived from SZ or X-ray observations are in good agreement (Andrade-Santos et al. 2018). We also find, using four different metrics to identify cluster cool cores, that for each metric, the sample of X-ray selected clusters contains a significantly larger fraction of cool core clusters, compared to the SZ sample. In particular, the measured fraction of cool core clusters in the X-ray sample ranges from ~40 to 60%, depending on the particular metric used to identify cool cores, while the fraction of cool core clusters in the SZ sample ranges from ~30 to 40% (Andrade-Santos et al. 2018). Thus X-ray flux-limited cluster samples, compared to the approximately mass-limited SZ sample, are overrepresented with cool-core clusters. We describe a simple model that uses the excess luminosity of cool-core clusters, compared to non-cool-core clusters at fixed mass, to successfully predict the observed fraction of cool-core clusters in X-ray-selected samples. In addition, we find that cluster masses derived from Chandra observations agree well with Planck SZ masses (Andrade-Santos et al. 2019).
2D metallicity gradients and how they depend on substructures in MaNGA galaxies
Jones, Amy
Many galaxies have a metallicity gradient, however there is a large scatter about the slope of this gradient. Typically the galaxy is azimuthally averaged to look only at the 1D metallicity profile as a function of radius. With IFU observations, we no longer need to azimuthal average, but instead can use the 2D metallicity map to describe metallicities in galaxies. With SDSS IV MaNGA observations, we can disentangle the scatter in the 1D profile by measuring metallicity gradients along certain substructures within the galaxies, e.g. spiral arms and bars. By looking at the gradients along the structures, we hope to minimize the scatter and compare these different gradients. We will use the full 2D information to find quantitative parameters, such as asymmetry, M20, and MID diagnostics, to describe the metallicity distribution within galaxies and see how these correlate with other galactic properties and structure.
Turbulent Generation of Galaxy Cluster Magnetic Fields
Jones, Thomas
Observations, and especially radio observations, reveal that microGauss-strength magnetic fields commonly pervade ICMs. Although the bulk dynamical stresses of those fields are probably sub-dominant to other forces, the fields should still play critical roles in ICM behaviors through microphysics, energy transport and dissipation processes. Largely independent of the sources of ICM seed magnetic fields, the extent and magnitude of the fields almost certainly depend on amplification and distribution by ICM turbulence. The effectiveness of turbulence in this context depends, in turn, on the strength, distribution, duration and character of the turbulence during cluster formation and evolution. In this presentation I will outline results from our simulation studies of MHD turbulence and cluster formation dynamics addressing these issues. I will emphasize the importance of turbulence "character", as well as its distributions in space and time, and also stress the implications to ICM physics of the observed ICM magnetic field properties.This work is supported at the University of Minnesota by the US National Science Foundation and the University of Minnesota Supercomputing Institute.
SN 1987A: The Formation and Evolution of Dust in a Supernova Explosion
Jones, Olivia
From Supernova to Supernova Remnant, SN 1987A, has given us a unique opportunity to study the mechanics of a supernova explosion and now to witness the birth of a supernova remnant. With JWST, we wish to understand how massive stars age and explode, how their ejecta forms dust and molecules and how the blast wave from their violent explosion affects their surroundings. In this talk, I will describe the scientific goals of the joint nine hour program between the MIRI European Consortium and Meixner's US MIRI Science Time allocation to capture the time evolution of SN1987A using JWST MIRI imaging, MRS spectroscopy and NIRSpec IFU spectroscopy. These will provide key emission line diagnostics and dust feature and continuum measurements of SN 1987A.The central stellar ejecta of SN 1987A is surrounded by a ring of progenitor gas and dust that is being shocked by the blast wave of the explosion. A large quantity (0.4-0.7 M) of dust in the stellar ejecta has an unknown composition and our MIRI observations may provide the first constraints through the imaging and MRS spectroscopy. Both the MRS and NIRSpec IFU spectroscopy will measure key shocked line diagnostics that will constrain the shock physics as well as the elemental abundances in both the ring and the stellar ejecta.
Towards a better scattered moonlight model and aerosol extinction determination at Cerro Paranal
Jones, Amy
Estimating the sky background is critical for ground-based astronomical research. In the optical, scattered moonlight dominates the sky background, when the moon is above the horizon. The most uncertain component of a scattered moonlight model is the aerosol scattering. The current, official sky background model for Cerro Paranal uses an extrapolated aerosol extinction curve. With a set of X-Shooter sky observations, we have tested the current model as well as determined the aerosol extinction from UV to NIR. These observations were taken of plain sky, during three different lunar phases, and at six different angular distances from the moon for each night/lunar phase. Using a set of models with varying aerosol distributions to compare with the observations, we found the most likely aerosol extinction curves, phase functions, and volume densities for the three nights of observations. While there were some degeneracies in the aerosol scattering properties, in general the current model had significantly less coarse particles compared to the favored volume densities from the X-Shooter data. This affects the phase function by being more peaked at small angular distances. Also the extinction curves flatten towards redder wavelengths and are overall less steep compared to the extrapolated curve used in the official model. Overall, the current model does reproduce the observations for average conditions decently well. For the three nights of sky observations, the aerosol distributions differed reflecting the changes in atmospheric conditions and aerosol content, which is expected. These changes among the three nights seemed to correlate with the atmospheric conditions recorded at the site. Using sky observations and the sky background model is a unique way to probe the aerosol content of the atmosphere.
SDSS efforts on inclusion for bridging different communities
Jones, Amy
The Sloan Digital Sky Survey (SDSS) IV is an international astronomy collaboration that has been in the fore-front of addressing issues of inclusivity within the collaboration. Many of the things learned in SDSS can be applied to IAU activities and efforts. SDSS IV originally created two committees, one focused on women and the other on minorities, and two years ago these joined to form COINS, the committee on inclusion in SDSS. Part of the charge is to conduct a yearly or bi-yearly demographics survey to asses the inclusiveness within SDSS. To help increase minority participation within SDSS and astronomy, we had the FAST (faculty and student teams) Initiative and REU (research experience for undergraduates) programs. Additionally, there are many efforts to help younger members feel welcome and participate, currently with a focus at the collaboration meetings. We have drafted several documents, including how to make a meeting more accessible and inclusive, best practices regarding code of conduct, best practices for running telecons, and meeting chairing guidelines. I would like to share what has been successful for SDSS which would be useful for the IAU and bridging different communities.
Using Inhomogeneous Chemical Evolution to Model Dwarf Galaxies
Jordan, Chris
We use an inhomogeneous chemical evolution (i-GEtool) code to model the dwarf spheroidal galaxy, Draco. Using i-GEtool as opposed to traditional chemical evolution models allows a natural dispersion to occur within the output data, thus mimicking observations. We tune our model to simulate the Draco system using the metallicity distribution function and star formation history. We investigate the alpha-element abundance distributions, comparing and contrasting different stellar yields to find a best fit to observational data. Lastly we examine methods used for calculating gas outflow in models.we confirm that the use of different stellar yields sets can change GCE results. For instance, the NuGrid yield set has problems reproducing the high [alpha/Fe] observations whereas the yields from do not reproduce the low [alpha/Fe] results. We use a new method in inhomogeneous codes to model outflows, allowing supernovae type-II to expand beyond the radius of Draco, making outflows self-consistent and more similar to current hydrodynamic models. Our outflow method was found to imply a high ratio of star formation rate to outflow rate, i.e. mass-loading, factor of ~15.
Internal calibration of the spectrophotometry in Gaia mission
Jordi, Carme
Gaia space mission includes two slitless low-resolution spectrographs (one blue and another one red) aimed to parameterize the observed sources. The focal plane includes 7 CCDs for each of the spectrographs to acquire the observations. Gaia observes simultaneously with two telescopes. The Gaia spectra will be part of the next Data Release 3.The aim of the talk is to show the current approach for the internal self-calibration of all the acquired observations in order to define a mean instrument from the two fields of view and across the focal plane.
Spectroscopic binaries among AGB stars
Jorissen, Alain
Very few spectroscopic binaries hosting an AGB component are known so far. We will present a few long-period binaries discovered with the HERMES spectrograph mounted on the Mercator telescope at the Roque de los Muchachos Observatory (La Palma). These discoveries open interesting prospects for diagnosing the interaction of the AGB wind with the companion. A few specific cases will be discussed.
OH maser structures in the molecular cloud W49N.
Juarez, Mariana
W49N is part of the Giant Molecular Cloud (GMC) W49A, a high-mass star forming region, which is located near the galactic plane. W49A has been observed at different wavelengths, as millimeter and radio wavelengths, finding dozens of HII regions and many compact cores, many of which are at W49N. They indicate the presence of newly born high mass stars and protostars. This star forming region is one of the most efficients in our galaxy.The processes of high mass stars still have many caveats. For this reason, the study of W49N is of great importance. In particular, the identification of spatial structures, can give clue information on the ongoing processes as accretion and outflows and on their physical conditions. All these information can be used as probes of different models of high mass star formation.OH masers at 1612, 1665 and 1667 at RCP and LCP observed with the VLBA are analyzed in this work. We found a velocity gradient of the maser spots. Also, large velocity dispersions of some groups of spots, that are close in distance, is observed. The parameters of the groups of these OH masers are being studied to evaluate their possible kinematics. For some of these groups, it is found that, their velocity dispersion seem to be due to the local kinematics rather than to global or turbulent motions.
Use of Astronomy to Motivate the Girl Child into Science Related Careers
Jurua, Edward
The government of Uganda has a policy to improve the number of female students in tertiary institutions. This has motivated very few female students into science related programmes compared to the humanities in tertiary institutions. In the case of Mbarara University of Science and Technology, more male students are enrolled at undergraduate annually than the female students. This has a direct effect on the number of female students continuing to postgraduate studies in science related programmes. This could be due to socio-cultural reason. In addition, there are negative influences from the society, with the believe that science careers are meant for the male gender but not the female gender. We used Astronomy outreach to girls’ secondary schools to motivate the female students into the sciences. In this paper, the use of astronomy to motivate and encourage the girl child into science related programmes in tertiary institutions in Uganda is discussed.
Red Giant Star KIC 5110738 in the Kepler Open Cluster NGC 6819
Jurua, Edward
The Kepler Input Catalogue (KIC) misclassified a number of red giant stars as sub giants. This could have resulted from the large uncertainties in the KIC surface gravities. This resulted in 1523 stars which were recently classified red giant stars. The cluster membership of the 1523 red giant stars was determined using age, distance modulus, and variation of colour magnitude with large frequency separation. We found that only one star is a member of NGC 6819.
The dynamical impact of satellite galaxies on the Milky Way disc
Just, Andreas
We investigated the interaction of dark matter (DM) subhaloes on the thin disc of Milky Way-like host galaxies by high-resolution re-simulations combining the statistical properties of DM halos from the Aquarius simulations with a live host galaxy in dynamical equilibirum. We have shown that the contribution of DM subhalos to the dynamical heating of the inner disc of the Milky Way is not dominant. However, the impact of DM haloes with a few billion solar masses on disc perturbations like the bar, vertical wiggles and warps is significant. These DM intruders are not able to force a bar to form, but they can trigger or delay bar formation by up to a Gyr, if the galaxy becomes bar unstable. Consequently, from the existence of a (even young) bar one cannot infer a recent interaction event with a satellite galaxy. In contrast, vertically oscillating ring-like wiggles as observed recently in the Milky Way, have a lifetime of roughly 1 Gyr and thus point to a recent pertubation event. Warps of the outer disc survive for a few Gyr or even longer and serve as a cumulative measure of past harassement or merger events of satellite galaxies. The dynamics of the impact of DM subhaloes with respect to the formation and evolution of bars, wiggles and warps will be discussed.
ALMA spectrum of the extreme OH/IR star OH26.5+0.6
Justtanont, Kay
We present ALMA band 7 data of OH 26.5+0.6 in band 7, resolving the CO J=3-2 emission which shows a compact core (FWHM = 0.6 arcsec), surrounded by tenuous envelope which extends out to 4-5 arcsec where CO is photodissociated. The circumstellar envelope also exhibit a number of emission lines due to metals, e.g., NaCl and KCl. A lack of C$^{18}$O is expected but a nondetection of C$^{17}$O is puzzling given the strength of H$_{2}$^{17}$O from the Herschel spectrum of the star. However, a line associated with Si$^{17}$O is seen which may be indicative in molecular formation processesin envelope of extreme OH/IR stars. We also report a detection of the gas-phase emission line of MgS J=21-20. MgS dust is found exclusively in C-rich circumstellar environment and is thought to be the carrier of the 30$\mu$m dust feature. ALMA spectrum of this object reveals intriguing features which may be used to investigate chemical processes and dust formation during a high mass-loss phase.
Dust emission and polarisation in the massive star-forming filament G35.39-0.33
Juvela, Mika
G35.39-0.33 is a massive (~5000 MSun) filamentary cloud at a distance of 2.9 kpc. It has a number of low-luminosity infrared sources and potentially prestellar massive cores but still appears to be in an early stage of its star formation activity. We have used JCMT POL-2 850 µm observations and Planck 353 GHz measurements to study dust emission and polarisation in the G35.39-0.33 field. The relationships between the magnetic field geometry, grain alignment, and polarisation fraction were examined with radiative transfer modelling.The G35.39-0.33 cloud exhibits large values of submillimetre dust opacity and opacity spectral index, both typical of very dense clouds. Planck data reveal an almost uniform polarisation fraction and a field direction that is at an oblique angle relative to the main cloud. In SCUBA-2 observations, the magnetic field is mostly perpendicular to the filament but at one end turns parallel to it. There is no contradiction because the SCUBA-2 measurements are not sensitive to the large scale field. The polarisation fraction in the filament is of the order of p=1-2%. The decrease of p as a function of column density is partly caused by noise, with a possible contribution from the filtering of the extended emission. The data are in agreement with models where grain alignment is lost at densities above ~104 cm-3. The agreement with simulations employing radiative torques alignment is only approximate but strong conclusions are precluded by the uncertainty of the 3D field geometry and the spatial filtering of the ground-based observations.The presentation is given on behalf of the JCMT Large Program SCOPE (PI T. Liu).
Evolution of Milky Way angular momentum: comparison of the Newtonian gravity with DM and non-Newtonian gravity without DM
Kacala, Ivan
Evolution of Milky Way angular momentum: comparison of the Newtonian gravity with DM and non-Newtonian gravity without DMIvan Kacala, Roman Nagy, Jozef KlackaDepartment of Astronomy, Physics of the Earth and MeteorologyFaculty of Mathematics, Physics and Informatics, Comenius UniversityMlynská dolina F1, 842 48 Bratislava, Slovak RepublicA standard approach to examination of orbital evolution of stars in the galactic disk and related evolution of the galactic angular momentum considers Newtonian gravity and the spherical halo of dark matter. In our contribution, we compare this standard approach with a new approach considering modified Newtonian dynamics / gravity based on observational results from the work by McGaugh et al. (2016) and the spherical halo of dark matter is not considered. We trace distribution of angular momentum of stars in the Milky Way galaxy for the two approaches described above by simulating motion of more than 103 stars. The models of the galactic structures (central bar, galactic disk and spiral arms) used in our simulations are in accordance with observed properties of the Milky Way, e. g., Freudenreich (1998), Antoja et al. (2011), Klacka et al. (2012). We find that the distribution of angular momentum in the new approach corresponds, approximately, to the conventional distribution of angular momentum, if the standard Newtonian approach is considered.References:Antoja T., Figueras F., Romero-Gómez M., Pichardo B., Valenzuela O., Moreno E.: 2011, Understanding the spiral structure of the Milky Way using the local kinematic groups. Mon. Not. R. Astron. Soc. 418, 1423Freudenreich H. T.: 1998, A COBE model of the galactic bar and disk. Astrophys. J. 492, 495Klacka J., Nagy R., Jurci M.: 2012, Radial migration of the sun in the galactic disc. Mon. Not. R. Astron. Soc. 427, 358McGaugh S. S., Lelli F., Schombert J. M.: 2016, The Radial Acceleration Relation in Rotationally Supported Galaxies. Phys. Rev. Lett. 117, 201101
Outburst Models for Young Eruptive Stars
Kadam, Kundan
The formation of low mass stars through protoplanetary discs is a highly complex process. Accretion during star formation is also time dependent and the most compelling evidence for it can be seen in the observations of young eruptive stars. Variable young stars called FUors show sudden brightening by a factor of about 100, which can last for several decades. A closely related class of young eruptive stars EXors show relatively smaller outbursts lasting only a few years. It is proposed that such events lie on a continuum and may be a part of the standard pre main sequence evolution (Audard et al. 2014). Although the prototype FU Orionis has been in outburst since 1936, the origin of such eruptions is still highly debated and there are several proposed mechanisms. Earliest model includes viscous-thermal instabilities in the protoplanetary disc (Bell & Lin 1994), while an alternative model shows that a combination of gravitational and magneto-rotational instability leads to episodic accretion (Armitage et al. 2001). Perturbation of the disc due to a planet or close companion can also induce periodic outbursts (Lodato & Clarke 2004). Vorobyov & Basu (2005) show that massive discs can gravitationally fragment leading to accretion in clumps. For EXor events, D’Angelo & Spruit 2010 propose another theory for magnetic stars when the accretion disc is truncated close to the corotation radius. I will summarize the literature related to the models of young eruptive stars and update on its current status. I will present our latest numerical results which improve upon the shortcomings of previous models of both FUor and EXor type outbursts. I will also discuss the observability of the predictions made by such models through latest high spatial and spectral resolution sub-millimeter and infrared techniques.
Statistical study of magnetic reconnection in accretion disks systems around HMXBs
Kadowaki, Luis H.S.
Highly magnetized accretion disks are present in high-mass X-ray binaries (HMXBs). The complex emission observed in these systems indicates the presence of different regimes of accretion. A hot, low-density magnetized disk corona is frequently invoked in order to explain the non-thermal high-energy emission. A potential mechanism to explain the transition between the High/Soft and Low/Hard states observed in HMXBs can be attributed to fast magnetic reconnection induced in the turbulent corona. According to this model, the power released by fast reconnection between the magnetic field lines arising from the inner accretion disk and the lines anchored into the compact source could accelerate relativistic particles in a first-order Fermi process and produce the observed non-thermal emission. In this work, we present results of high-resolution three-dimensional local magnetohydrodynamic (MHD) simulations and global general-relativistic MHD (GRMHD) simulations of accretion disks around black holes that show that fast reconnection events, similar to those occurring in the solar corona, can naturally arise in the coronal region of magnetized accretion disks in presence of turbulence triggered by MHD instabilities, indicating that such events can be a potential mechanism to explain the transient non-thermal emission in HMXBs. To find the zones of fast reconnection, we have employed an algorithm to identify the presence of current sheets in the turbulent regions and computed statistically the magnetic reconnection rates in these locations obtaining average reconnection rates consistent with the predictions of the theory of turbulence-induced fast reconnection.
On the contrast of solar magnetic elements in the quiet Sun and active region plage
Kahil, Fatima
It is well established now that small-scale magnetic elements on the solar surface are major contributors to the solar irradiance variations. Such variations are caused mainly by the variation of the solar magnetic flux. Since quantifying this contribution depends on the spatial resolution of the data, we use SUNRISE observations of a quiet-Sun network (2009 flight) and an active region plage (2013 flight) to investigate how the brightness of small-scale magnetic elements at/near disk center depends on the photospheric magnetic field strength. At a spatial resolution of 0.15 arcsec achieved by IMaX, and with high resolution imaging in the UV, we update earlier studies of the brightness contrast of magnetic elements. The brightness with respect to the quiet surroundings (contrast) is measured in the continuum and in the core of the Fe I line at 525.02 nm with the Imaging Magnetograph eXperiment (IMaX), and in the UV spectral range with the SUNRISE Filter Imager (SuFI) at 300 nm and at 397 nm. Information on the magnetic field vector and other physical parameters is derived from inverting the spectropolarimtertic data taken around the Fe I line. We find that in the UV, the contrast in both regions increases with increasing field strength, independently of their size. In the continuum at 525.40 nm, the averaged contrast in the quiet Sun saturates at higer field strengths instead of peaking and decreasing like obtained in earlier lower spatial resolution studies. In plage, however, we find that the downturn in the contrast is due to their dark magnetic cores as expected from larger features. We also find that the quiet Sun reaches higher contrast than plages and the difference decreases with atmospheric height.
Atlas of Ha-images for five hundred nearest dwarf galaxies
Kaisin, Serafim
Results of mass imaging nearby dwarf galaxies in emission Ha-line and red continuum with the 6-m BTA telescope are available via the address:http://www.sao.ru/lv/lvgdb. The sample of dwarfs limited by a distance of 11 Mpc contains about 500 objects. Their Ha-fluxes are used to derive integrated and specific star formation rates of the galaxies. We evaluate the consistency between star formation rates obtained from our Ha-survey and GALEX far-ultraviolet survey. We fix a systematic rise of the ratioSFR(FUV)/SFR(Ha) with the decreasing stellar mass of dwarf galaxies.
Catalog & Atlas of the LV Galaxies
Kaisina, Elena
We present a database of galaxies in the Local Volume (https://www.sao.ru/lv/lvgdb/) having individual distance estimates within 11 Mpc or corrected radial velocities VLG < 600 km s–1. It collects data on the following galaxy observables: angular diameters, apparent magnitudes in far-UV, B, and Ksbands, Ha and HI fluxes, morphological types, HI-line widths, radial velocities, and distance estimates. Also contains a consolidated set of optical images of all the galaxies from the SDSS and DSS surveys and Ha images of galaxies that were observed with the 6-m BTA telescope. The latest version of the Updated Nearby Galaxy Catalog (UNGC) (Karachentsev et al. 2013) contains 869 objects, now in the database more 1150 objects. We present the some main dependencies describing the updated sample LV galaxies: Hubble flow, distribution galaxies according to their distance estimates and on the sky, relation between the absolute magnitude, Holmberg diameter, and rotation velocity et al.
HISTORICAL PROGRESS OF METEOR RADAR OBSERVATIONS IN KAZAN (RUSSIA)
Kalabanov, Sergei
The development of meteor radio measurements in Kazan was originated in the 1950th on the base of the Kazan state university. In 1957 it was created laboratory under the direction of Kostilev K.Further a group of researchers has been consistently developing several radar installations from KGU-M1 to KGU-M5 (fig.1) providing scientific data for studies of meteoric complex near the Earth's orbit.To interpret the results of meteor radar observations it has been necessary to create and then to develop the methodology of quantitative and qualitative characteristics of coming meteoric matter.The purpose of meteor radar observations is the determination of the meteoroid flux density Q above a given mass and the parameter s (mass index) of the meteoroid mass distribution.In 1970th analytical solution for determining the distributions of Q and s with an accuracy of 10 dgr. was obtained by Belkovich O. and Pupyshev Y.In the 1980th it was developed a method for determining the Q distribution with measurement of arrival angles of the reflected radio waves from meteor trails by Belkovich O., Sidorov V., Filimonova T. with the accuracy of 5 dgr.In the early 2000th on the basis of microshower hypothesis it was developed the discrete quasytomographic method that is able to measure the angular coordinates of radiant of meteor showers with the accuracy of 2 dgr. by Sidorov V. and Kalabanov S. [1], fig3.In 2015 Kazan University purchased a new meteor radar. Now the radar detects in average 6000 meteor radioechoes per day, fig.2https://cloud.mail.ru/public/KHqP/rQ1jLaCsyFig 1. Antenna system of the KGU-M5https://cloud.mail.ru/public/5Ahf/8BkHm84x7Fig 2. The transmitting antennahttps://cloud.mail.ru/public/A4DV/LpjjqLh7uFig 3. Orbital structure of meteoric complexThis work was funded by the subsidy allocated at Kazan Federal University for the state assignment in the sphere of scientific activities ? 3.740.2017/8.9. [1] Solar System Research. 2008. V. 42. ? 3, pp.194-208
A NEW PLATFORM FOR METEOR RADAR OBSERVATIONS IN KAZAN FEDERAL UNIVERSITY (RUSSIA)
Kalabanov, Sergei
The Kazan Meteor Radar (KMR) is a new generation system deployed on the scientific research area of Kazan Federal University, Tatarstan, Russia (55 N) in March 2015. KMR transmits 15kW power in pulse and uses single antenna all sky configuration for transmission and five-antennas for reception of meteor radiechos (Fig.1, Fig.2). The new design increases the sensitivity of the radar enabling the detection of about 6000 of particles per day.Initial surveys show that KMR observes a very strong contribution of the North Hemisphere source enabling primary on-line analysis software of meteor detection and position determination parameters: the time of the detection, the height of the detection in km, the radial drift velocity of the detection in m/s, the zenith and the azimuth angles of the detection in degrees, the entrance speed of the meteors in km/s.The off-line analysis software developed in Kazan University [1],[2] is able to determine the radiant coordinates of meteor showers and to calculate meteoroid orbital parameters using the raw data.Finally, results from various radar meteor researches will be presented in this contribution. It will be shown the orbital statistics, the radiant coordinates of meteor showers detected throughout the year 2017 (Fig.3).https://cloud.mail.ru/public/MvrM/d6Qfg8bBXFigure 1. The transmitting antenna of KMRhttps://cloud.mail.ru/public/LNdu/hSHxSueFgFigure 2. The pulse transmitter module of KMR.https://cloud.mail.ru/public/7wda/sxSFir9dSFigure 3. The whole celestial sphere Jan. 2016 with detected Quadrantids from KMR.Acknowledgments: This work was funded by the subsidy allocated at Kazan Federal University for the state assignment in the sphere of scientific activities ? 3.740.2017/8.9.References:[1] Sidorov V., Kalabanov S., Sidorova S., Filin I., Filimonova T. Meteoroids-2004, journal Earth, Moon, Planets, Kluwer Academic Publishers, p.165-179[2] Kalabanov S., Sidorov V.ACM-2002, 2002, ESA Publications, Netherlands, p.149-152
Star formation across the metallicity ladder in the local group dwarf Magellanic system
Kalari, Venu
We present resolved multi-wavelength observations of molecular clouds, young stellar objects, and pre-main sequence stars (the latter two limited to stars more massive than a solar mass) in the local group dwarf galaxies the Large (1/5 Zsun), Small (1/10 Zsun), and the Magellanic Bridge (1/10 Zsun). From these, we compare our results with those in the Galaxy to demonstrate how there are noticeable differences in key star formation indicators, and also the effect of feedback from massive stars across the metallicity ladder- which may provide vital clues as to how star formation proceeded in the early Universe.
Direct imaging observations of possible dynamical upheavals in exoplanetary systems
Kalas, Paul
Giant planets are thought to form and persist on coplanar, circular orbits in the region of the protoplanetary disk cold enough to hold icy materials. However, direct imaging observations reveal highly asymmetric debris disks and associated exoplanets that are inclined relative to these disks, have highly eccentric orbits, or are located at hundreds of au radius. Here we present new HST/STIS images of several 10-100 Myr old systems that are consistent with dynamical upheavals. We discovered one highly asymmetric dust disk around an M0 target in the 11 Myr-old Upper Sco association that could be a signature of a disk-planet perturbation. Another target is Fomalhaut C (LP 876-10) where the new data test for a highly eccentric disk resulting from dynamical interactions with Fomalhaut A and B. In addition, we show deep coronagraphic images of the HD 106906 planetary system that achieve higher signal-to-noise and a smaller inner working angle than previous HST/ACS optical observations. The very extreme vertical and radial disk asymmetries of this 13 Myr-old Lower Centaurus-Crux debris disk indicate a recent dynamical upheaval involving a stellar flyby.
Swift and XMM-Newton monitoring of the BL Lac object PG 1553+113 during 2010-2017
Kalita, Nibedita
The BL Lac PG 1553+113 has been frequently monitored in X-rays with Swift and XMM-Newton satellites. It lies in the redshift range 4< z < 5.8. The object recently attracted attention of the community because of the probable existence of a super massive black hole binary system at its center. We have investigated the temporal and spectral behavior of the source in the energy range 0.3–10 keV during different activity states with XRT and Epic-pn instruments on board the satellites Swift and XMM-Newton, respectively. During the high phase significant variability in the flux has been detected, where variation occurs less than an hour. The continuum emission from the source is generally best described by a log-parabolic model. Spectral evolution study of PG 1553+113 reveals a clear harder-when-brighter trend.
Evolution and motions in the most active sunspot groups of Cycle 24
Kalman, Bela
Cycle 24 was unusual in that it began significantly later and was smaller than the earlier 4. In this poster, possible differences in sunspot motion patterns and flare activity are studied, using internet databases, relating to the largest and/or most active groups of the cycle, compared to previous examples of earlier cycles. The spot motions in Active Regions NOAA 11748, 12192 and 12673/4 allow us to obtain information on the emerging flux tubes below the photospheric level, and show, which types of interactions lead to greater flare activity level, which is particularly noticeable when comparing „normal” large AR 12674 to quickly evolving and interacting AR 12673.
The Complex of Remotely Controlled Devices at the RTT150 for Increasing the Effectivity of Scientific Observations
Kandemir, Ekrem
Russian Turkish telescope (RTT) is a 1.5 m telescope and installed in 1998 under the agreement between Russia and Turkey and the first light was received from the telescope in September 2001. The telescope is devoted to kind of astrophysical observations in the visible range and it has various modern scientific astronomical instruments which can operate in wide range observations. The instruments of RTT150 make possible to carry out complex and high-quality observations which meet all requirements of astrophysical researches. Due to use of these instruments, there are many observation modes available to work in different kind of observation such as spectroscopy, photometry and polarimetry etc. To increase the observational effectivity of scientific instruments of RTT150, it becomes necessary to build additional complex of devices and user-friendly GUI to the present telescope control system with the developments of modern control techniques remotely. In the initial stage, the integration of dome covers feedback position, controlling of dome flat field lamps, remote telescope power control, telescope voltage display and Сoude Echelle Spectrometer calibration units control are realized and their automation control can be done remotely without human intervention. In the final stage of the developed system, it makes RTT150 possible to increase follow up observation efficiency and provides faster response to the transient astrophysical events. Therefore, the remotely controlled complex of devices leads the telescope scientific instrument capability to increase of observation performance of telescope in its related telescope class.
Does A Galaxy Group Environment Affect Molecular Gas Properties in Galaxies?
Kaneko, Hiroyuki
Galaxy groups are a common environment, since about a half of nearby galaxies belong to them. Then, to understand the galaxy evolution including star formation history, it is important to investigate whether molecular gas properties in groups are similar to that in clusters. However, the limited number of CO images prohibits us to study statistical nature of molecular gas in galaxies, for example, how much it exists or how it distributes. We, a CO Multiline Imaging of Nearby Galaxies (COMING) project team, have performed imaging observations of more than 100 nearby galaxies with 12CO(J=1-0), 13CO(J=1-0), and C18O(J=1-0) lines. With the first data, we present the result of molecular gas mass, atomic gas mass, and a molecular gas fraction. We find these three quantities are not different between isolated galaxies and galaxy groups. This implies that selective HI stripping and galaxy suffocation by shock compression, which are seen in galaxy clusters, and effective molecular gas formation under a strong galaxy interaction may not play a dominant role in galaxy groups.
Constraints on the warm dark matter mass using the Milky Way satellite galaxies
Kang, Xi
Studying the very inner structure of faint satellite galaxy requires very high-resolution hydro-dynamical simulations with realistic model for star formation, which is beginning to emerge very recently. In this work we study the kinematics of satellite galaxies in the Milky Way using an analytical description. Our aim is to investigate their constraints on the nature of dark matter,namely cold dark matter and warm dark matter. We use a Monte-Carlo method to produce merger trees of Milky Way mass halos and a semi-analytical model to produce visible stars in the satellite galaxies. We consider a few important processes which can significantly affect the satellite kinematics. The first is the reduction of dark matter halo concentration in the warm dark matter model. The second is the baryonic feedback which can induce a flat inner profile with a dependence on the star formation efficiency in the satellite galaxy. The third is the tidal stirring which can further reduce the satellite velocity dispersion. Compared to previous studies, our model is firstly tuned to fit the stellar mass of satellites, thus they have correct star formation efficiency and associated inner density profile. We show that in the CDM model the baryonic feedback effect alone can reduce the satellite velocity dispersion to agree with the observation, and a maximum of 30\% reduce in satellite velocity dispersion by tidal heating is allowed. Without tidal stirring, the WDM model with dark matter mass m_s < 3.5 keV is excluded and a strong tidal stirring can even rule out model with m_s < 10 keV. Our results indicate that current favored WDM model with m_s ~ a few keV is bad for the too-big-to-fail problem, and conversely, it leads to a too-diffuse-to-sustain problem.
Information of TRAO with all changed systems
Kang, Hyunwoo
Taeduk Radio astronomy Observatory (TRAO) has installed all new systems, and opened scientific observation service from 2016. There are SEQUOIA-TRAO receiver system, VxWorks observation system, FFT2G backend system, servo system, and new radome. SEQUOIA-TRAO is 4X4 receiver system that operates from 86 GHz to 115 GHz with low system noise temperature (170 K at 100 GHz and 400 K at 115 GHz). VxWorks system supports most stable environment with On-The-Fly mainly. FFT2G covers 32 pixel data from the receiver of which each pixels support two frequencies by power divider. Servo system has replaced with new motors and drivers. Radome has substituted with rude one. There are three key science projects from 2016, and some dozen general projects yearly. Wide band mode up to 2 GHz is being supported soon.
Dwarf Galaxies in the Local Volume
Karachentsev, Igor
A catalog of 1060 Local volume (=LV) galaxies situated within a distance of 11 Mpc contains 870 dwarfs, i.e. 5/6 of the sample. Almost 40% of them have accurate distances measured with Hubble Space Telescope. Most of the LV dwarfs have been observed already in HI and H_alpha emission lines, as well in far-ultraviolet with GALEX. We present basic properties of the LV dwarfs, their HI-mass content and star-formation rate in different local environments. We discuss a baryonic Tully-Fisher relation for the LV dwarfs, and apply it to determine TF-distances for several hundreds other local galaxies. The accurate distances and radial velocities of the LV dwarfs are used by us to trace dark matter distribution within 11 Mpc. We discuss also does the Local Group may be treated as a typical or uncommon representative of the LV population.
Near-Infrared atmospheric modelling of Jupiter’s Southern Equatorial Belt (SEB) observed with AAT/IRIS2
Karamiqucham, Behrooz
The low resolution (R ~ 2400, H and K bands) spectra of Jupiter’s Southern Equatorial Belt have been modelled using VSTAR (Versatile Software for Transfer of Atmospheric Radiation) and ATMOF (ATMOspheric Fitting) codes through observation of the Anglo-Australian Telescope’s Infra-Red Imaging Spectrograph 2 (AAT/IRIS2). By creating a line-by-line radiative transfer model with the most latest ammonia and methane line lists we derived the best models in the Jupiter’s, ammonia depleted, SEB. Using different cloud and haze opacities and distributions resulted from our modelling outputs, we were able to fit our models to the spectra of the planet in the observed region. Our findings enable us to use and define the resulted parameters to uncover the cloud and haze pressure heights and opacities in the spectral H and K bands of Jupiter’s troposphere and stratosphere.
When binaries keep track of recent AGB nucleosynthesis: The Zr - Nb pair in extrinsic stars as an efficient s-process diagnostic
Karinkuzhi, Drisya
Extrinsic stars like Barium, CH and CEMP-s (carbon-enriched metal poor) stars are s-process enriched giants; they owe their chemical peculiarities to a past mass transfer, during which they were polluted by their binary companion, which was at the time an asymptotic giant branch (AGB) star, but now an extinct white dwarf. Hence extrinsic stars are ideal targets to understand and constrain the s-process in low- to intermediate-mass AGB stars. Actually, since the $^{93}Zr/Zr$ isotopic ratio is a sensitive function of the s-process operation temperature (independently of stellar evolution models), and since, in extrinsic stars, $^{93}Zr$ has fully decayed into mono-isotopic$^{93}Nb$, we can use the Nb/Zr abundance ratio to constrain the s-process operation temperature. Adopting the same methodology as in Neyskens et al. (Nature 517, 174–176, 2015), we analyze a sample of highly-enriched extrinsic stars observed with the high-resolution HERMES spectrograph mounted on the MERCATOR telescope (La Palma). We derived the abundances of a large number of heavy elements. They provide more accurate constraints on the s-process operation temperature and therefore on the s-process neutron source. The results are then compared with stellar evolution and nucleosynthesis models. Four stars in our sample show peculiar abundance patterns with high nitrogen abundance and high [Nb/Zr] ratio. We compare the nucleosynthetic profile of the present sample stars with those of CEMP-s, CEMP-rs and CEMP-r stars. One barium star of our sample is potentially identified as the highest-metallicity CEMP-rs stars yet discovered. Whether the i-process could account for its abundance pattern is discussed (Karinkuzhi et al., A&A, submitted).
Toward the standardized astronomy curriculum: Analysis of astronomy syllabus in Japanese universities
Karino, Shigeyuki
IAU has shown clear direction to broadly support the astronomy education / outreach in developing countries with the International Year of Astronomy 2009 celebrations and its vision through the “Strategic Plan 2010–2020”.To relocate knowledge to developing countries, international education exchanges are required. In particular, it is necessary to support higher education for young people in developing countries, to train up researchers and educators who can play leading roles in their own countries. At present, however, a required level of education has not been defined, in an international cooperative framework of astronomy education. This could lead to significant obstacles, especially when students study abroad. That is, for students, it is difficult to understand the entrance skills required, and the skills achieved after receiving training in a particular institution. This situation might cause a serious mismatch between students' intentions/levels and the curricula offered by institutions. It is possible to avoid such a mismatching by having a set of "standardized skills in astronomy" and "standard curricula of astronomy" based on the improving scheme of those skills.Here, our final goal is to formulate a standard curriculum of astronomy from the above viewpoint. Toward this goal, we need to1) Investigate the current curriculum of astronomy to grasp the current situation and constitute the framework of a standardized curriculum of astronomy in higher educations.2) Formalize an IAU endorsement for the creation of the IAU Astronomy Education Guidelines. Here, we report the preliminary analysis of the astronomy curricula in Japanese universities, focusing on the general education levels, and highlight the points at issue.Then, we propose a way to formulate a standard curriculum of astronomy by objectively incorporating the present notion of what factors are determinant for science (astronomy) to be “comprehensive” in accordance with the goal settled by IAU.
On the long-term variability of high massive X-ray binary Cyg X-1
Karitskaya, Eugenia
We present the results of our study of spectral and photometric long-term Cyg X-1 variability on the base of the 44-year long series of multicolor photometric and many-year-long spectral observations. In 2006 it was revealed for the first time that the temperature of the optical component (О9.7Iab supergiant) was decreasing and its size was increasing over 7 years (1997–2003). The photometry performed at the Crimean Station of Sternberg Astronomical Institute (Lomonosov Moscow State University) shows that the variability of the supergiant in this system on the time scale of decades continues up to now - the mean level of star brightness continues to decrease since 1999 with the variations on smaller time scales superimposed. A remarkable very blue flare 2009 in U-band coinciding with X-ray flare is revealed. Our spectral observations show variations of HeI λ4713Å absorption line depths. There is a connection between X-ray and optical changes. The chaotic variations of X-ray flux sometimes reaching to "hard" - "soft" state irregular changes switch on when U brightness and HeI λ4713Å absorption line depth decrease. And inversely - they switch off during U brightness and HeI λ4713Å absorption line depth increasing. This is may be connected with star size variations, causing outflow gas instability._x005F It is concluded that the fundamental parameters of the supergiant in the system of Cyg X-1 continue to vary.
Observation and modeling of a pseudostreamer before and during eruption
Karna, Nishu
Coronal mass ejections (CMEs) are the most violent eruptions in our Solar System. CMEs are responsible for large solar energetic particle events and severe geomagnetic storms. In this study, we present a magnetic configuration of a pseudostreamer before and during eruption observed on April 19, 2015 on the Southern West limb embedding a prominence cavity. The eruption resulted in a relatively wide CME with a round front and prominence core. In SOHO/LASCO C2 partial halo was observed. The prominence eruption begins with a slow rise and then evolves to a fast rise phase. We first constructed a non-linear force free field (NLFFF) model of this pseudostreamer using the flux rope insertion method. The NLFFF model produces the 3D coronal magnetic field constrained by observed coronal structures and photospheric magnetogram. SDO/HMI magnetogram was used as an input for the model. The field configurations representing the eruption are not in force-free equilibrium. We magnetofrictionally relax the model until the flux rope expands to three solar radii and compare CME propagation with the SOHO/LASCO C2 observations. From the simulation results, we determine the process for the eruption by identifying where reconnection takes place and how much flux is reconnected. We determine the pre-eruption twist and decay index and how the twist is transferred as the simulation progresses. In addition, we perform a topology analysis of the models in order to determine the location of quasi-separatrix layers (QSLs). QSLs are used as a proxy to determine where strong electric current sheets develop in the corona and also provide important information about the connectivity in this complicated magnetic field configuration.
On Russian - Cubian meteor observations
Kartashova, Anna
Meteor observations have the specific property: we do not know in advance neither point on the celestial sphere, no about a moment when the event occurs. Besides, a meteor flash in the atmosphere has duration few seconds or less. Therefore the wide-field cameras are used for meteor observations. Since 2011 INASAN has been conducting the meteor observations from Zvenigorod observatory INASAN and “Istra” station. Simultaneously meteor observations are carried out by IDG RAS and Ryazan State University. Thus, organizing a meteor network in the central part of Russia. The weather in Moscow region not very useful for optical observations and approximate we have 100-120 nights (the night with partly cloudy also) per year. So the main part of our observations was conducted during the summer period (in the period of the Perseid meteor shower activity). Due to the specific properties of meteor observations, it is necessary to carry out continuous monitoring throughout the year. Therefore important to performed meteor observations from different part of Earth. In the first time the meteor observations were performed from the territory of Cuba (the reserve “Sierro del Rosario” (~70 km from Havana)). The television system (the camera Watec LCL-902H3 and the lenses Computar F=2.9-8.2 mm, 1:1.0) with field of view of 90° x 65° and limiting magnitude (for meteors) +2.0m was used for observations. Observations were carried out by a single station method .108 meteors (brighter than +1m) were detected during the period 12-14 December 2017. 77 meteors were associated with Geminid meteor shower. Results of these single stations observations are presented.
The multi technique meteor observations in 2016-2017
Kartashova, Anna
The interaction of meteor particles with the atmosphere produces the optical (actually meteors) and infrasound emission. Most meteor particles do not reach the surface of the Earth, their properties (mass, size, density and etc.) are estimated based on the observational data under different assumptions. The details of meteor-atmosphere interaction are poorly known, the parameters of meteor particles are determined with large uncertainty. Simultaneous registration of meteors by different techniques provides possibility to refine both the meteor parameters and models of particle interactions with the atmosphere. Multi technique (optical and acoustical) meteor observations were organized by Institute Astronomy RAS and Institute for Dynamics of Geospheres RAS in 2014 and continued in August 2016. The multi - station optical observations are conducted on Zvenigorod observatory of INASAN (ZO INASAN), the “Istra” station, Geophysical observatory IDG RAS Mikhnevo (GPhOMikhnevo). Simultaneously infrasound meteor observations are carried out at three stations (IDG RAS, GPhOMikhnevo, ZO INASAN) in 2016 (and present time). The radiant positions, geocentric velocity, heights and orbit parameters were calculated for all double-station meteors. The meteoroids mass were estimated based on these data by different methods. Comparison of masses and energies, which were obtained based on optical and acoustical observations, shows considerable variation of values (up to two orders of magnitude). The details of these analyzes are presented.
A Population of Gas-Poor Field Dwarfs in the Local Volume?
Karunakaran, Ananthan
We have searched for atomic gas along the lines-of-sight to low surface brightness (LSB) features that project near Local Volume galaxies in order to explore the possibility that they are dwarf satellites of the latter. The properties of the satellite populations of galaxies are vital for understanding galaxy formation and evolution. Wide-field optical imaging campaigns are effective at detecting LSB features, however, typical optical follow-up methods are expensive; the distances to these putative dwarf galaxies, and therefore their association with their putative parents, are unknown. We exploit well-known atomic gas (HI) properties of low-mass systems to constrain this association. Dwarf galaxies in the field are almost ubiquitously gas-rich while low mass satellites within the virial radius of a massive host are gas-poor; an HI non-detection along the line of sight to an LSB feature supports the hypothesis that it is a dwarf satellite of its putative parent. We have performed GBT observations to search for HI reservoirs in 48 LSB features detected in deep images near known Local Volume galaxies. While we do find some gas-rich dwarfs around nearby massive hosts and in the field, the vast majority (~80%) of our observations yield stringent non-detections. Surprisingly, a number of them correspond to LSB features that are not resolved into stars by HST, placing a firm lower limit on their distances and rule out the possibility that they are satellites of their nearest Local Volume host. Combining GBT and HST results, we find that these systems are plausibly gas-poor, M* ~10^7 Mo field dwarfs. We will report on our efforts to distinguish real satellite galaxies from background interlopers around nearby galaxies, compare their measured properties to established dwarf galaxy scaling relations, and explain how the predictions of these relations can be reconciled with our observations by invoking a population of gas-poor, field dwarfs in the Local Volume.
Accretion Simulations of Eta Carinae and Implications to Massive Binaries
Kashi, Amit
We present high resolution numerical simulations of the colliding wind system Eta Carinae, showing accretion onto the secondary star close to periastron passage. This question was unanswered for more than a decade and our new high resolution simulations were able to finally provide an answer. We find that the smooth stellar winds collide and develop instabilities, mainly the non-linear thin shell instability, and form filaments and clumps. We find that a few days before periastron passage the dense filaments and clumps flow towards the secondary as a result of its gravitational attraction, and reach the zone where we inject the secondary wind. We run our simulations for the conventional stellar masses, M1=120 Msun and M2=30 Msun, and for a high mass model, M1=170 Msun and M2=80 Msun, that was proposed to better fit the history of giant eruptions in the nineteenth century. As expected, the simulations results show that the accretion processes is more pronounced for a more massive secondary star. We obtain orbital parameters of the binary system from the simulation results, and learn about the recovery of Eta Carinae from its giant eruptions. This leads us to the conclusion that the presence of a binary companions can have a huge influence on the evolution of massive star, especially at later stages where it may undergo giant episodes of mass loss.
Dwarfs in the entourage of the Local Volume groups: flow tracers and cosmological probes
Kashibadze, Olga
We consider a sample of field dwarf galaxies with accurate distances and radial velocities around 14 massive groups in the Local Volume (LV). We combine all the data into a single synthetic LV group, and then determine its radius of the zero-velocity surface, which separates any overdensity against the global cosmic expansion. Our approach is based on a comparison of the observational data with the velocity field expected from the spherical infall model, including effects of the cosmological constant. We found the optimal value of the radius to be 0.93±0.02 Mpc. Assuming the standard Planck model parameters, it corresponds to the total mass of the synthetic group ~(1.6±0.2)×1012 M☉ Thus, we are faced with the paradoxical result that the total mass of the LV group estimated on the scale of 3-4 its virial radius is only 60% of the virial mass estimate. Anyway, we conclude that wide outskirts of the nearby groups do not contain a large amount of hidden mass outside their virial radius.
The effects of the Galactic structures on Solar motion measurements
Kashiwada, Yuki
Measuring the Solar motion is a long-standing problem in Galactic astronomy. Although most previous studies were based on the axisymmetric kinematic models to measure the Solar motion, it is known that the non-axisymmetric Galactic structures (i.e. a bar and spiral arms) affect the kinematics of nearby stars. In this study, we therefore investigated the effects of the bar and spiral arms on the Solar motion measurement using the 'mock' Gaia DR2 data for the purpose of determining the solar motion with Gaia. The mock data are generated from 3D N-body/hydrodynamic simulations of a bar potential, rigidly rotating spiral potential (i.e., density wave), and dynamically evolving barred spiral models (Baba 2015; Baba et al. 2018). Applying the Oort-Lindblad and Ogrodonikov-Mile models to the mock data, we evaluated the effects of the spatial distributions and velocity structures (e.g. velocity ellipsoids and substructures) of sample stars. Using Bayesian analysis, we found that the difference between velocity dispersions of sample stars does not have a large influence on the values of the Solar motion in the Oort-Lindblad model. We will also discuss the effects of tilts of velocity ellipsoids, resonance orbits, selections of sample stars.
Stargazing Party in Terminal Care
Kato, Seiichi
It has been recognized that public outreach is important activity in astronomical society. When we held the seminar and/or stargazing party, people across all age groups participated in the activities, but the participants usually had good health. On the other hand, Japan is world's fastest aging society, and it will be not enough to hold the seminar only in the future. We show the example of the stargazing party at the hospice(facilities for terminal care) and share the problem. People in the hospice, the staff and their families have various condition of health.
Challenges for the NIR spectroscopic mode of MICADO@ELT
Kausch, Wolfgang
MICADO (Multi-AO Imaging Camera for Deep Observations) will be one of the first-light ELT instruments, covering the wavelength range from 0.8 through 2.4µm. Its main capabilities aim for SCAO and MCAO (MAORY) supported diffraction-limited imaging, astrometry, coronagraphy, and high-time resolved imaging on a 3x3 detector array.MICADO will also comprise an echelle slit spectroscopic mode, which is mainly designed for point and compact sources. A spectral resolving power of up to R~19000 will be achieved for point sources. The wavelength range is covered in two setups (0.8 through 1.45 µm, and 1.22 through 2.4µm) for a slit length of 4 arcsec. In addition, a longer slit with 20 arcsec is under consideration for slightly extended sources (enabling a simultaneous observation of the sky emission), being able to take spectra in one photometric band, separated by a set of order sorting filters.The spectroscopic capability is intended to be a workhorse mode, applicable to a broad variety of science cases. In particular, high-redshifted objects up to z~6, e.g. supernovae, emission line galaxies, star-forming HII region complexes, properties of starburst galaxies, dynamical investigations of the Galactic centre by combining MICADO’s astrometric and spectroscopic capabilities, or studies on stellar populations in nearby galaxies are the main scientific goals to be addressed.Since the ELT project is on the edge of today’s feasible technologies, the instrument design is very demanding, e.g. effects on the point spread function arising from the adaptive optics modules (SCAO and MCAO), or technical challenges from the telescope construction introduce unknowns, which nevertheless need to be taken into account properly to achieve science-ready data. In this presentation we give an overview on the main goals and the optical design of the spectrograph, the current status of the software development for the data reduction, and an outlook on the further development.
Implications of a density dependent IMF for the statistics of progenitors of gravitational wave sources
Kavila, Indulekha
Observations of multi-compact-object mergers taking place in galaxies offers a window to massive star formation in globular clusters, the oldest objects in the Universe. The advent of next generation telescopes like the James Webb Space Telescope and the TMT allow detailed exploration of binaries, and their statistics in deeply embedded star burst as well as globular cluster fields. The advent of Advanced LIGO and LISA leads us to multi-messenger astronomy that includes multi-wavelength observations on multi-compact-object mergers in the GW sector too. More and more sophisticated codes allow us to track the formation and evolution of binaries in stellar clusters and details of the evolution and merger of multi-compact-object systems, from the very early phases of high stellar density and high density of embedding gas to late phases wherein massive compact objects merge. In simulations of binary formation and evolution in globular clusters, the possibility that the distribution in the properties of the initial set of binaries might have a non-standard IMF factored into them, has not been explored. Observations of the nearest high mass star forming regions point to the IMF at the high mass end being flatter than Salpeter in regions where the stellar densities are high. We explore the impact of the distribution in the properties of the initial set of binaries that have a non-standard IMF factored into them, on the statistics of potential gravitational wave sources in the Galaxy derived from simulations. Globular clusters being significant contributors to the ionization history of the early universe, the results have implications for the same, and also on our ability to explore the putative mass gap between the upper limit for neutron star masses and the lower limit for black hole masses. Priors with different assumptions regarding the IMF from which the binaries are drawn, changes the derived most likely masses as well as the confidence intervals on them.
Development of stargazing party for local elementary school students
Kawagoe, Shio
Chiyoda Ward Kudan Secondary School has a 15 cm refracted telescope. School science teachers of Kudan secondary school wanted to organize stargazing parties using the 15 cm refracted telescope for public, especially local elementary school students. However, no one knew how to use the telescope. In order to organize the stargazing parties for the local elementary school students, the teachers requested the cooperation with some astronomers and graduates of a Kudan high school astronomy club.The first stargazing party was held for the Kudan secondary school students in October 2009, in order to train the staffs of the stargazing parties for the elementary school students. At this party, there was not only observation of stars but also lectures on how to use the telescopes and astronomical simulation software.In November 2009, we organized the stargazing party for the local children. In order to look for participants, we informed the public through posters and the homepage. The participants of this event limit 10, because the participants take a lecture from real astronomers as active learning. At this event, we decided 10 participants by drawing lots, because there were 24 applicants. A few of the students who participated in the first stargazing party helped this event as a staffs. We have held about 70 stargazing parties for the local children since 2009. The number of applicants is 5062.Recently, the students who participated in the stargazing parties when they were elementary school students are enrolled in Kudan secondary school. Some of them join as a staff of the stargazing parties. Furthermore, college students who graduated from the Kudan secondary school have supported the stargazing parties and have been teaching the student staff. We shall pursue to establish such cycles.
Hyper-Eddington Soft X-ray Nova from a Be Binary System
Kawai, Nobuyuki
MAXI J0158-744 is an extraordinary soft X-ray transient discovered from a Be system located near the Small Magellanic Cloud. It is characterized by a soft X-ray spectrum with little flux above 4 keV, a rapid rise (< 6ks), a short duration (< 11 ks), and a huge peak luminosity of 2x1040 erg/s in 0.7-7.0 keV band with a 0.92 keV Ne emission line. Its later spectrum resembling "super-soft X-ray source" indicates that the transient event was an explosion on a white dwarf that exceeds the Eddington luminosity by two orders of magnitude. These properties suggest that the explosion involves a small amount of ejecta and is produced on an unusually massive O-Ne white dwarf close to, or possibly over, the Chandrasekhar limit. We propose that the huge luminosity detected with MAXI was due to the fireball phase, a direct manifestation of the ignition of the thermonuclear runaway process in a nova explosion. This interpretation has been further supported by the radiative transfer calculation using a Monte Carlo code.
Direct evidence of a few to tens parsecs torus in 3C84
Kawakatu, Nozomu
New discovery of a parsec scale northern lobe in a nearby bright radio galaxy 3C 84 at 43 and 86 GHz shades a light on the nature of structure surrounding of active galactic nuclei (AGNs). Based on this, we examine a parsec scale surrounding matter near supermassive black holes (SMBHs) of 3C 84.The optically thick spectral feature of northern lobe can be interpreted as the existence of a dense matter, which is responsible for the free-free absorption of the northern lobe with the ionized electron density with 10^5 cm^-3. Moreover, the ratio of the observed optical depths at 43 and 86GHz suggests highly inhomogeneous surrounding matter near SMBHs within a parsec scale. In addition to this, the abrupt appearance of the new counter lobe implies the column density with N_H~10^23-24 cm^-2 for inclination angle 40-80 deg. This would be consistent with results of the radiation-driven fountain model for low-luminosity AGNs(Wada 2012). Thus, this may suggest that the observed absorbing structure is a direct evidence of the clumpy torus.
Gamification and Drama as a Technique to Teach Astronomy to Primary and Secondary School Students
KAYIHAN, H. Aziz
Children like to run and scream during school hours thus creating chaos. That is an alternate way they experience the universe around them. Chaos is in a way a big part of our universe, as it is our children's life. This chaos is a way for them to tell that they want to be more involved in the process. Presenting them with games and fun activities contributes greatly to their education and learning experience. Astronomy is yet another course, children can learn through games and drama. Games create challenge, this is a way for children to prove themselves among others and drama create teamwork and involvement. Combining the two, by gamifying the topics, presents a much more effective method for teaching astronomy and space sciences. In this study, we present the ways and methods through which astronomy is better carried to children an how classrooms can suddenly turn into magical space funfairs for them. Yet, educational systems are a part of the challenge as an obstacle on the way.
A specific non-gravitational effect in the asteroid belt as a possible main cause of origin of Trojans in the Solar system
Kazantsev, Anatolii
A specific non-gravitational effect (NGE) in the asteroid belt is revealed. This NGE manifests itself in an increase in the semimajor axes of orbits of low-albedo asteroids relative to the semimajor axes of orbits of high-albedo bodies. The increase of semimajor axes of asteroids with albedos ? < 0.1 may be as high as 1.E–7 AU/year. The NGE presently affects the motion of a considerable fraction (not less than 20%) of main-belt asteroids with diameters up to 40 km. The NGE action can see from results of numerical calculations of the orbital evolution of asteroids from 2005 to 2016. From the numerical calculations there were obtained differences (da) of semimajor axes of asteroid orbits for 10 years, which are not caused by the gravitational influence of the planets. A significant dependence of the da values on the albedos for bodies with sizes of 5-40 km is obtained. Such result is confirmed by dependences asteroid albedos on proper semimajor axes for individual asteroid families. The physical mechanism behind this NGE should be close in nature to an NGE in comets. The action of this NGE can explain:- the well-known reduction of the mean albedo across the asteroid belt;- the existence Trojans of Mars, Jupiter and Neptune and the absence Trojans of Saturn;- the origin of the Hilda group asteroids and the low albedos of these bodies, as well as the Jupiter Trojans. This mechanism of the Trojans origin involves certain characteristics of small bodies, which can easy verify from observations:- Mars Trojans should mostly have retrograde rotation;- Hilda group asteroids and Jupiter Trojans should mainly have prograde rotation.
The Trojans distribution in the Solar System
Kazantsev, Anatolii
Orbits of potential Trojans of different planets in the solar system were selected from the MPC catalog on February, 2017. The evolution of those orbits was calculated. The bodies on librating orbits around the points L4 and L5 were determined. The quantities of real Trojans in the MPC catalog are as follows: Mars - 5, Jupiter - over 4500, Saturn - none, Uranus - 2, Neptune - 15. A reasoned explanation of such distribution of Trojans in the solar system is proposed.
Submission for 'Planets Days' Juno mission and supporting observations from the GEMINI telescope
Kedziora-Chudczer, Lucyna
The Juno spacecraft is placed in the 53-day orbit around Jupiter taking data of its atmospheric composition, magnetic fields and gravity that will help to answer many fundamental questions about planetary formation, evolution and physics. I will discuss the most detailed maps of Jovian clouds and radiometric measurements that probe planetary weather systems to unprecedented depths. I will focus on Juno’s observations of Jovian auroras that are formed in high-latitude atmospheric layers as a result of charged particles precipitating from planetary magnetosphere. Juno’s study of the Jovian polar regions is complemented by observations from the ground telescopes. Our observations of Jupiter aurora with the GNIRS spectrograph at the Gemini telescope provide high-resolution (R~18000), near-infrared H3+ auroral emission maps in the planetary polar regions. These can be used to estimate temperatures and ion density profiles in the upper ionosphere of Jupiter. Juno's measurements of particle energies in the planetary magnetosphere combined with information from the infrared emissions, will help us to understand how the ionosphere of the planet responds to heating.
Search for water on extrasolar planets with polarimetric observations
Kedziora-Chudczer, Lucyna
Light scattered from the atmosphere of a planet and its surface is polarised. In contrast, light from solar-type stars is largely unpolarised. Therefore polarimetry can be used for the detection and characterisation of extrasolar planets around such stars. The degree of polarisation due to reflected starlight depends strongly on the composition and physical properties of planetary atmospheres. Ultimately observations of polarisation could provide the clues about the water droplets in the planetary atmosphere and possible detection of liquid water on the planetary surface via glint reflection.I will discuss polarimetric observations of hot Jupiters with the high precision polarimeter, HIPPI at the Anglo Australian telescope built at the UNSW. I will also describe capabilities of the newly developed polarimeter, HIPPI-2, to be used on the 8-metre Gemini telescope.
The mineralogy of AGB dust in the Magellanic Clouds
Kemper, Ciska
The Surveying the Agents of Galaxy Evolution (SAGE) project has been hugely successful in using the Spitzer and Herschel Space Telescopes to study the life cycle of dust in the Magellanic Clouds. Using the photometric modes on both these telescopes, an inventory of the interstellar dust reservoir and the stellar sources (AGB stars) and sinks (young stellar objects) of dust has been made. In particular, Boyer et al. (2011) identified tens of thousands of dust producing AGB stars in both the Large and the Small Magellanic Clouds (LMC, SMC), while Riebel et al. (2012) and Srinivasan et al. (2016) used a grid of radiative transfer models to estimate the total dust production by AGB stars in the LMC and SMC. The photometric surveys were followed up with a spectroscopic survey, which used the Infrared Spectrograph (IRS) on board of Spitzer to observe around 200 point sources in the LMC, not all AGB stars, in the SAGE-Spec survey. Furthermore, the SAGE-Spec project also included all archival spectroscopic observations obtained wit IRS within the SAGE and SAGE-SMC footprint, arriving at a total of approximately 1000 unique targets in the LMC and 250 in the SMC; of which 225 and 58, respectively, are AGB stars. Here we summarize the SAGE-Spec legacy of the mineralogical analysis of these objects, draw conclusions with respect to the mineralogical composition of freshly produced AGB dust on a global scale, and compare the result with the composition of interstellar dust.
Astronomical Data Visualized with 360 degree Video
Kent, Brian
We present a method to create 360 degree spherical panoramic video of different astronomical data types. 2D sky maps and catalogs, 3D galaxy catalogs, and GIS and planetary maps can be imported and viewed on a desktop browser. The setup extends to mobile devices as well, using Python and the Google Spatial Media module so that the accelerometer can be used as a navigation and control mechanism. Examples and tutorials are shown to instruct users on ways to visualize their own data.
A multiwavelength analysis of the long duration flare observed on 2002 April 15
Kepa, Anna
We present a multiwavelength analysis of the long duration flare observed on 2002 April 15 (soft X-ray peak time at 03:55 UT). This flare occurred in NOAA 9906 and was observed by a number of space instruments including EIT/SOHO, RESIK, and RHESSI. We have performed a complex analysis of available measurements and studied the morphology and physical parameters characterizing the conditions in the flaring plasmas. The EIT images have been used to study evolution of flaring loops. RHESSI data provided opportunity of detailed analysis o HXR emission with a high energy resolution. The temperature diagnostics of flaring plasma have been carried out by means of a differential emission measure (DEM) analysis based on RESIK X-ray spectra and GOES.
Hot star winds over evolutionary timescales: revisions of the mass-loss prescription and impact of magnetic confinement
Keszthelyi, Zsolt
Surface phenomena, such as mass loss, angular momentum loss, and magnetism of the individual components of high-mass X-ray binary systems have a large impact on the evolution of these objects. Stellar evolution models rely on parametric prescriptions to account for such surface effects, however the evaluation, revision, and a change in currently-used prescriptions has become inevitable. In this contribution, we will present how the revision of mass-loss rates and the incorporation of surface magnetic fields can change modern stellar evolution models of massive stars.Mass-loss rates of hot stars are uncertain by at least a factor of two. Their dependence on surface properties, such as the effective temperature, may show abrupt changes at certain critical values. New theoretical results support observational indications that the effective temperatures at which these changes may occur had previously been overpredicted. These revised predictions urgently need to be adopted in stellar evolution models in view of their important consequences for massive star evolution.Magnetic confinement in hot, massive stars has far-reaching consequences. The effects arise from the magnetic field’s interaction with the stellar wind, leading to mass-loss quenching and magnetic braking. State-of-the-art stellar evolution models predict that magnetic progenitors can account for the formation of ‘heavy’ stellar mass black holes (such as those detected by the Advanced LIGO) and pair-instability supernovae, even at solar metallicity.
Asteroseismology of Machine Learnt light curves
Kgoadi, Refilwe
Due to an avalanche of data that is currently available in astronomy, Astroinformatics is increasingly becoming a common analytical tool. The availability of stellar light curves from survey data has promoted the usage of this new tool in stellar physics. Astroinformatics has enabled classification of stars (variable or non-variable) to be performed at a faster rate, allowing researchers to shift their focus from tedious work such as data reduction methodologies to studying the internal dynamics of stars. This research aims to construct a classification algorithm using a combination of Catalina Real-Time Transient Survey (CRTS) and Optical Gravitational Lensing Experiment (OGLE) survey data. Based on its efficiency, a second test set comprising of light curves obtained from (non-survey, ground-based) photometric CCD observations of two Fields of View (FOVs) within the Large Magellanic Cloud (LMC) will be classified. These test data were part of photometric studies at the South African Astronomical Observatory (SAAO), Sutherland, South Africa with a 2.6 * 2.6 arcmin square FOV charge-coupled device (CCD) on a 1.0 m telescope detector. Johnson-Cousins filters (UBVIC) were used during observations. Light curves were extracted from calibrated CCD frames using a photometric package; \textit{daophot}, which is part of the Image Reduction Analysis Facility (IRAF) \textit{noao} suite. Features from light curves were generated using a python based feature engineering software package. As a next step, pulsation modes of classified plausible pulsating stars will be identified using software packages such as Frequency Analysis and Mode Identification for Asteroseismology (FAMIAS). If this test is successful, we will broaden our search for pulsating stars to other large datasets. Details of our strategy will be discussed.
Rising magnetic flux tubes as a source of IR-variability of the accretion disks of young stars
Khaibrakhmanov, Sergey
We investigate the dynamics of the magnetic flux tubes (MFTs) in the accretion disks of young stars. Slender flux tube approximation is used. Equations of the model include the aerodynamic and turbulent drag forces, radiative heat exchange with external medium, magnetic pressure of the disk. Structure of the disk is calculated using our MHD model of the accretion disks of young stars. Vertically stratified polytropic disk is considered.We study various thermal regimes of the dynamics of the MFT: motion in thermal equilibrium with external gas, adiabatic motion, motion with heat exchange. We investigate dependence of the velocity of the MFTs on initial radius, plasma beta, position in the disk.Simulations show that the less initial plasma beta of the MFT the more it’s speed. The MFTs with plasma beta ~0.1 and radius comparable to height scale of the disk move with velocities up to 50 km/s causing periodic outflows from the disks. Pressure of the magnetic field of the disk counteracts the buoyancy causing the MFTs to oscillate near the surface of the disk. Periods of the oscillations are 10-100 days. The radius, density and temperature of the MFTs also vary during the oscillations.We propose that the MFTs periodically rising from the inner regions of the disks and oscillating above the disk’s surface can cause the IR variability of the thermal radiation of the disks. Time scales of oscillations found in our simulations agree with the measured periods of the IR variability of the accretion disks of young stars.
Characterizing the atmospheres of giant exoplanets
Khalafinejad, Sarah
The application of the transmission spectroscopy method during a transit of an exoplanet has allowed us to study the chemical composition of exoplanetary atmospheres. Among evolved exoplanets, hot Jupiters have the largest and most extended atmospheres. Hence, considering current observing facilities, they are great targets for carrying out atmospheric characterization. These objects allow us to improve our observing techniques and re ne our models to characterize other types of exoplanetary atmospheres such as the atmospheres of Earth analogues. To reach this stage, one of the most important steps in the data analysis is to disentangle the host star features from those of the planet. This is particularly important for the characterization of small and rocky exoplanets, which so far have mainly been detected around active M dwarfs. In this research, we used single transit observations of HD 189733b (with UVES/VLT) and WASP-17b (with MIKE/Magellan) as test targets. We obtained their high-resolution transmission spectra at sodium lines. In this procedure, we rst considered the e ects of stellar aring activity and stellar di erential limb-darkening. Then, as a novel approach, we accounted for the changing planetary radial velocity on the atmospheric excess light curves. In the second stage of the work, after the detection of sodium in these giant exoplanets, the transmission spectra are compared with atmospheric models to constrain the temperature and radius of the exoplanet. We are currently improving our framework to additionally consider the e ects of stellar spots. Hence, it can be used for applications on lower-mass targets.
Studies of physical parameters of kilometer sized Near Earth Asteroids by the RTT-150 telescope.
Khamitov, Irek
The relevance of the study of Near Earth Asteroids (NEA) is related to the origin of the Solar system, the potential danger of collision with the Earth, and also the practical interest in the near future of using them as source of useful minerals and metals. We discuss the program of experimental studies (aim, status and used methods) as full as possible sample of kilometer sized NEAs are carrying out with the 1.5 m Russian-Turkish telescope RTT150. The results of polarimetric and photometric observations in V bandpass of 23 faint NEAs (18 objects with diameter larger than 1 km and 5 of them only a few hundred meters in diameter) with high proper motion in period of theirs close approaches performed at RTT150 between the August 2014 and February 2018 are presented. The estimation of albedo and diameters of asteroids by means of polarimetric and photometric data is discussed. Due to that sources were observed at large phase angles from 40 to 100 degrees for different asteroids the measured linear polarization degree makes it possible to differentiate the taxonomy classes of observed sources even using single shot as well. In addition to polarimetric determination, the spectral class of NEA 333888 was obtained with direct using the low resolution spectra (R~600, covered whole visual range from 4000 Å to 9000 Å) obtained with RTT150 facilities.
Dynamic interaction of expanding plasmospheres of hot giant exoplanets with the stellar wind: On the transit spectra features
Khodachenko, Maxim
The interaction of escaping upper atmosphere of a hydrogen rich non-magnetized analogue of HD209458b with a stellar wind of its host G-type star at different orbital distances is simulated with a 2D axisymmetric multi-fluid hydrodynamic model. A realistic sun-like spectrum of XUV radiation, which ionizes and heats the planetary atmosphere, hydrogen photo-chemistry, as well as stellar-planetary tidal interaction are self-consistently taken into account. Two different regimes of the planetary and stellar winds interaction were modelled: 1) the “captured by the star” regime, when the tidal force and pressure gradient drive the planetary material beyond the Roche lobe towards the star, and 2) the “blown by the wind” regime, when sufficiently strong stellar wind confines the escaping planetary atmosphere and channels it to the tail. The model simulates in details the generation of energetic neutral atoms (ENAs) around the planet due to their acceleration by the radiation pressure and as a result of charge-exchange between the stellar wind protons and planetary atoms. These simulations enable calculating of the Lya absorption during transits of HD209458b and quantifying the major mechanisms responsible for its observed features. The calculations in a wide range of stellar wind parameters and XUV flux values showed that under the typical Sun-like star conditions the observed absorption at the level of 6÷8% can be attributed only to the non-resonant natural line broadening. For lower XUV fluxes, e.g., during the activity minima, the number of planetary atoms that survive photo-ionization and give the origin to ENAs, increases resulting in up to 10÷15% absorption at blue wing of Lya line, caused by the resonant thermal line broadening. It has been found, that the radiation pressure in all considered cases has a negligible contribution to the production of ENAs and the corresponding absorption.
Stellar metallicity variations across spiral arms in disk galaxies with multiple populations
Khoperskov, Sergey
We discuss the formation of azimuthal metallicity variations in the disks of spiral galaxies in the absence of initial radial metallicity gradients. Using high-resolution N-body simulations, we model composite stellar discs, made of kinematically cold and hot stellar populations, and study their response to spiral arm perturbations. We find that, as expected, disk populations with different kinematics respond differently to a spiral perturbation, with the tendency for dynamically cooler populations to show a larger fractional contribution to spiral arms than dynamically hotter populations. By assuming a relation between kinematics and metallicity, namely the hotter the population, the more metal-poor it is, this differential response to the spiral arm perturbations naturally leads to azimuthal variations in the mean metallicity of stars in the simulated disk. Thus, azimuthal variations in the mean metallicity of stars across a spiral galaxy are not necessarily a consequence of the reshaping, by radial migration, of an initial radial metallicity gradient. They indeed arise naturally also in stellar disks which have initially only a negative vertical metallicity gradient.
bRing: Constructing a PSF Map
Khorshid, Niloofar
The MASCARA and bRing instruments are the first ground based instruments searching all sky for transiting exoplanets around bright stars with a magnitude of 4 to 8. The southern MASCARA and bRing network continuously covers a large area of the southern hemisphere between declination bands of -30 and -80 and the northern MASCARA instrument covers the northern hemisphere.Stellar flux seen by the detector is influenced by a variety of noise factors which results in lower signal to noise and photometry precision. The photometric precision of bRing is around 0.5% for ß Pictoris over 5 minutes. With this precision it is possible to detect planets on the order of Jupiter masses for every star. In order to push our limits we constructed a new method based on Point Spread Function (PSF) fitting to better reduce the raw data from bRing.We build a super resolved PSF map for the instrument so that each star is assigned a PSF which is dependent on the position of the star on the detector. There are two major assumptions upon which we build the PSF map: the PSF does not change significantly for a star within a short period of time, and the PSF shape does not change quickly over the detector area, meaning that neighbouring stars have similar PSF shapes. To construct the PSF map we average over all the frames we have for each star at the same siderial time.Comparing the results for ß Pictoris, this method works 40% better than the current method that is used for bRing and MASCARA, which is approximating the PSF by a circular aperture and calculating the flux within that aperture. The aperture photometry requires corrections around the edges which mostly come from coma aberrations, where the PSF spreads out of the aperture. At the edges, the average flux over the PSF becomes much lower and the signal to noise drops. This PSF method can be easily reapplied to any wide-field instrument, as it is independent to any unique characteristics of the detector.
AGN activity and the galaxy group environment
Khosroshahi, Habib
We study the AGN activity in the most massive galaxies in galaxy groups and show that their activity is influenced by the environment, more specifically with the dynamical state of the galaxy group. The dynamical state of the group is defined by the halo relaxation, probed by the stellar dominance of the brightest group galaxy and the offset between the position of the brightest group galaxy and the luminosity centroid of the group. We use GAMA survey data and show that the radio luminosity of the most massive galaxy in the group strongly depends on its environment, such that the brightest group galaxies in dynamically young or recently formed groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old or early formed groups. We have been able to successfully reproduce such an environmental influence on AGN activity of giant elliptical galaxies using a newly developed semi-analytic galaxy formation model.
Monitoring of the AGB star R Doradus using SPHERE/ZIMPOL
Khouri, Theo
In recent years, our understanding of the inner environment of evolved stars has been reshaped by high-angular-resolution imaging and the development of very sensitive instruments. These have revealed the highly dynamical inner circumstellar environments, from where the outflows are accelerated, and even details of the stellar photospheres, with overall asymmetries, hotspots, and shaping by convective cells. The new observational constraints are very important to guide the ongoing development of advanced computer simulations of convection, wind driving, and binary interactions. We have used the extreme adaptive optics and polarimetric imager SPHERE/ZIMPOL to monitor the AGB star R Doradus in visible wavelengths at 12 epochs over eight months using up to five filters per epoch. The stellar disc and the dust-formation region are resolved in the images obtained. This allows us to study the processes shaping the stellar disk and the time variability of dust formation. R Dor varies significantly in size between the different filters. Nonetheless, the images in each epoch reveal mostly a consistent picture of an asymmetric stellar disk with features that evolve on timescales from a few weeks to a few months. The polarised light images are interpreted using radiative transfer models and show a significant variation in the total amount and in the distribution of the dust grains. By analysing the wavelength dependence of the scattered light, we also study how the properties of the dust particles vary between the different epochs of observation.
New catalogue of extragalactic objects in the GAIA era
Khramtsov, Vladislav
In the GAIA era it is a crucial task of separation extragalactic objects from the galactic ones to test reference frame. We solved this problem with classification of objects due to optical-infrared colour information and created a new photometric catalogue of about 10 millions extragalactic objects from ALLWISE, Pan-STARRS DR1 and NOAO Source Catalogue (NSC) cross-identification. To create this catalogue, we employ Sparse Autoencoders (SAs) – machine learning technique for automatic feature extraction. We show that SAs provide precise star-galaxy separation in optical-infrared range without using any prior knowledge about types of objects. Separation were done using supervised classification in the high-dimensional sparse colour space by Support Vector Machine method.For investigation of separation accuracy, we tested catalogue of extragalactic sources using absolute proper motions from PMA catalogue; for this we cross-matched our resulting catalogue objects with PMA catalogue objects. We found that mean formal proper motion of these objects equals zero. Also we employ kinematic analysis: we investigated components of rotation tensor of our system according to solid-body rotation model; in result, all rotation components in faint part of magnitudes are zeros confirming that our objects are distant ones. Result was compared with same tests for other catalogues of extragalactic sources: ALLWISEAGN, Milliquas and WISExSCOS_photoz.In near future, we plan to test GAIA DR2 proper motions with our own catalogue.
Correlation of CCD aperture photometry and Herschel photometry of 29P/Schwassmann-Wachmann from the Herschel Catalogue of Solar System Object Observations
Kidger, Mark
Comet 29P/Schwassmann-Wachmann is an object of great interest due to the fact that despite orbiting in a low-eccentricity orbit between Jupiter and Saturn it shows frequent outbursts that can be of amplitude up to 6 magnitudes. The Herschel Science Archive reveals that twelve observations of Comet 29P/Schwassmann-Wachmann were made with the Herschel Space Observatory on six Operational Days between April 19th 2010 and February 17th 2013, all within the HssO Guaranteed Time Key Programme, “Water and related chemistry in the Solar System”. Three of the observations were high-resolution spectroscopy of the 110-101 o-H2O line at 557GHz taken with HIFI, four were imaging observations in mini-scanmap mode (scan and cross-scan) with the PACS photometer at 70 and 160 microns (obtained on 10/06/2010, 02/01/2011 & 17/02/2013) and one observation was SPIRE imaging photometry simultaneously at 250, 350 and 500 microns (obtained on 10/06/2010).The HIFI observations on April 19th 2010 are particularly interesting as they were made close to the peak of an outburst with maximum at R=12.5 (within a 30 arcsecond aperture) on April 16th. The HIFI observation shows a strong detection of the 557 GHz water line with a FWHM of ˜130m/s. A second observation, taken on May 11th, with the magnitude in a 10 arcsecond aperture down 2.5 magnitudes from the peak, shows a weak detection of a much broader 557 GHz line of FWHM 700m/s (Bockelée-Morvan et al., 2010DPS....42.0304B).We present the HIFI spectra and photometry of 29P at 70, 160, 250, 350 and 500 microns taken from the Herschel Catalogue of Solar System Object Observations that we correlate with the visible light curve of the comet as determined from an archive of 18500 historical CCD measures of the comet obtained by Spanish observers between 2002 and 2017 by the “Observadores_cometas” Group.
The Herschel Catalogue of Solar System Object Observations
Kidger, Mark
The European Space Agency's Herschel Space Observatory has been the only space facility to date to cover a spectral range from the far infrared to sub-millimetre (55-672µm). Herschel performed photometry and spectroscopy with its 3 on-board instruments: 2 diffraction-limited cameras - PACS (simultaneous observations in 70µm or 100µm and 160µm) and SPIRE (simultaneous observations in 250µm, 350µm, 500µm), each with a low-to-medium resolution spectrograph and a one very high resolution heterodyne spectrometer, HIFI.Herschel performed ˜37000 science observations of which 1693 were from Solar System objects (4.5% of the total) which represent 170 individual objects, including 5 planets and 6 of their satellites, 14 comets, 107 TNOs and 38 other asteroids. These measurements have been only partially exploited and to facilitate their analysis we have compiled these observations in the Herschel Catalogue of Solar System Object Observations (SSOO). We have included fluxes for each photometric observation, as well as complete ancillary information, a detailed classification of the observed bodies and the physical circumstances of the observation (phase angle, heliocentric distance, etc.) to facilitate a search for correlations between properties.We have analysed all the photometric observations from PACS and SPIRE using the science ready maps in the Herschel Interactive Processing Environment (HIPE) v15.0.1 and performed point source aperture photometry. Due to the diversity of the 170 SSOs (e.g. TNOs, planets) we developed a pipeline to apply to both faint and bright sources. The quality of the measurements has been analysed taking into account the source flux, sky background and published results from different types of bodies.We aim to facilitate the analysis of Herschel SSO data and help the scientific community to use the archive to widen our knowledge of the Solar System. Our own analysis of the data in this catalogue will be presented.
A new pipeline for astrometry and photometry of asteroids
Kilic, Yucel
Using Python 3, astropy and astrometry.net, a pipeline is developed to obtain photometric light curves of asteroids automatically queried by the SkyBoT database from sequential FITS images. The pipeline provides, pre-reduction of data, a reliable astrometry, standard differential photometry and light curves by auto-selecting multiple comparison-stars (maximum user-defined) from NOMAD catalog via VizieR. The pipeline was tested by existing photometric data of Karin Asteroid Family taken with SI-1100 CCD with 1-meter telescope at TUBITAK National Observatory in Antalya. The pipeline is not only applicable to archived data but it is also adjustable for ongoing observations. The code is an open source, free and hosted on GitHub with the GNU GPL v3 license.
Are Disky Dwarf Galaxies Unstable to Formation of Bars and Spirals?
Kim, Woong-Tae
A fraction of early-type dwarf galaxies in the Virgo cluster have a disk component and even possess disk features such as bar, lens, and spiral arms. Using N-body simulations, we study formation scenarios of these non-axisymmetric features in the disky dwarf galaxies. By adopting VCC 856 as our progenitor, a bulgeless dwarf disk galaxy with embedded faint spiral arms, we construct 15 initial conditions with slight dynamical variations based on observational error ranges and evolve them in isolation. Our standard model slowly forms a bar at ~3 Gyr and then undergoes buckling instability that temporarily weakens the bar, although the bar strength continues to grow afterward. Nine of our isolated models are also unstable to bar formation. This suggests that the disky dwarf galaxies are intrinsically unstable to form bars, accounting for a population of barred dwarf galaxies in the outskirts of the Virgo cluster. We also find that both the concentration of dark matter halo and the degree of random motions within stellar disk affect the vigor of buckling instability. To examine tidal effects from neighboring galaxies and a cluster, we additionally construct galaxy-galaxy and galaxy-cluster models by differing pericenter distances. We find that weak tidal interactions drive faint spirals, while strong encounters result in bars. Furthermore, our result of galaxy-cluster models shows that the tidal force in the cluster outskirts is insignificant in bar formation.
Nature or Nurture: The formation of compact elliptical galaxies
Kim, Suk
We aim at finding cE galaxies in various environments using SDSS DR12, and studying stellar population of cEs as a function of environments. Based on the typical properties of cE galaxies, we selected cE candidates by restricting that low-luminosity Mg > 19.5 mag, small sizes Re < 700 pc, and high-velocity dispersions σ > 60 km s-1. Since effective radii of cE candidates are mostly smaller than the seeing size of SDSS photometry, we calculated the effective radius by fitting a Sersic profile using GALFIT. In addition, an environmental parameter is computed as distances between cE galaxies and host galaxies (Mr < -21 mag). Mgb values of cEs increase as the distances from the host galaxies decrease. Especially, for cEs close to the host galaxies(\cEW; Dhost < virial radius), the Mgb values are similar to those of massive elliptical galaxies, which is consistent with the previous studies. On the other hand, cEs distant from the host galaxies (cEWO; Dhost > virial radius) lower Mgb values than the conventional cEs. Moreover, the Mgb values of cEWO follow the σ-Mgb relation of elliptical galaxies. This can be explained as a result of different merger histories for differing environments. For example, cEW galaxies are formed by tidal stripping by massive galaxies as suggested by previous studies (stripped origin or nurture), but cEWO galaxies could be linked with high-redshift spheroids (e.g. faint end of red nuggets) which have not evolved into present-day elliptical galaxies. (intrinsic origin or nature).
Tentative Discovery of a Star Cluster Remnant in the Sextans Dwarf Galaxy
Kim, Hak-Sub
We report a discovery of a possible relic of a star cluster in the Sextans dwarf spheroidal galaxy. Using the hk index (=(Ca-b)-(b-y)) as a photometric metallicity indicator, we have successfully discriminated the metal-poor and metal-rich stars in the galaxy and found an unexpected number density peak of metal-poor stars near the galaxy center. The stars around the peak form a narrow sequence in optical color-magnitude diagrams and exhibit redder colors than the bulk of field stars in the galaxy. Our population models suggest that they appear to be originated from an old, metal-poor globular cluster. This supports the presence of the star cluster remnants in the galaxy which have been suggested by previous studies, and provides a piece of evidence of a cored dark-matter halo profile for the Sextans dwarf galaxy. We will discuss the implications of our results for the dwarf galaxy formation theories.
High Resolution Spectral Analysis of SN 2011fe and SN 2014J
KIM, Soo Hyun
We present some results of spectral analysis for Type Ia supernova SN 2011fe in M101 and SN 2014J in M82. We performed spectroscopic observations with BOAO Echelle Spectrograph (BOES) attached to 1.8-m reflector (at Yeongcheon, South Korea). Our spectra was obtained for 18 epochs in 9 nights from September 6 2011 to April 1 2012 UT for SN 2011fe and 26 epochs in 6 nights from 22 January 2014 to 23 February 2014 UT for SN 2014J. SN 2011fe shows typical Type Ia spectra. High Velocity Features (HVF) are appeared in Si II and Ca II triplet. Absence of Ha emission line on late phase spectra and asymmetric features on several absorption lines indicate possibility of double degenerate scenario. SN 2014J also shows Type Ia spectra and HVF. We find notable feature around Na I doublet lines caused by ISM. No blueshifted Na I D lines and asymmetric features, which are appeared in SN 2011fe, also indicate possibility of double degenerate scenario. Comparison between SN 2011fe and SN 2014J by spectral feature variations for several significant lines including Ca II triplet, Si II and C II will be discussed.
Star Formation Activity of Barred Spiral Galaxies
Kim, Eunbin
We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at0.02=< z < 0.055 and Mr < -19.5 from the Sloan Digital Sky Survey. We compare the physical properties ofstrongly and weakly barred galaxies with those of non-barred galaxies that have stellar mass and redshiftdistributions similar to barred galaxies. We find that the star formation activity of strongly barred galaxies probed by starburstiness, g - r, NUV - r, and mid-infrared [3.4]–[12] colors is, on average, lower than that of nonbarred galaxies. However, weakly barred galaxies do not show such a difference between barred and non-barred galaxies. The amounts of atomic and molecular gas in strongly barred galaxies are smaller than those in non-barred galaxies, and the gas metallicity is higher in strongly barred galaxies than in non-barred galaxies. The gas properties of weakly barred galaxies again show no difference from those of non-barred galaxies. We stack the optical spectra of barred and non-barred galaxies in several mass bins and fit to the stacked spectra with a spectral fitting code, STARLIGHT. We find no significant difference in stellar populations between barred and non-barred galaxies for both strongly and weakly barred galaxies. Our results are consistent with the idea that the star formation activity of barred galaxies was enhanced in the past along with significant gas consumption, and is currently lower than or similar to that of non-barred galaxies. The past star formation enhancement depends on the strength of bars.
Stray Light Analysis of the Entoto Observatory Telescopes in Ethiopia
KIM, Young-Soo
Two 1 m telescopes were founded on the Entoto mountain of about 3200 m altitude. Entoto Observatory and Research Center in Ethiopian Space Science & Technology Institute is operating the telescopes, and found unusual patterns on the flat images. Those lead us to analyze stray light and to examine functions and performances of the system. In this paper, progress of the telescopes are introduced, and analysis result are described.
A Study on the Heumgyeonggak-nu, the Original Model of An Armillary Clock
Kim, Sang Hyuk
Heumgyeonggak-nu is an automatic mechanical water clock that was designed by King Sejong and produced by Jang Young-sil in 1438. This mechanical clock employed elements of the Chinese style escapement (i.e. water-hammering type) and the Islamic mechanics for generating time-signals. To express respect for astronomy, the clock structure was covered by an artificial mountain, the perimeter of which was decorated with images, puppets and the Sun to highlight the lives of the people, which moved through time and ran over the top respectively. We studied the mechanical structure and composition automatically playing on inner and outer spaces of the artificial mountain. According to our analysis, motion was generated on a time signal with components such as bumps on rails, an iron ball in the channel, and several levers inside the mountain. On the upper part of the mountain, a Holy Virgin matched Four Heavenly-Animals keep the time by shaking a handled bell when her Heavenly-Animal is in rotation together. At the middle part of the mountain, an hour-jack, bell warrior, drum warrior, and gong warrior are controlled on the time-keeping platform. On the ground, another 12 Holy Virgins with the time medallion were located around the foot of the mountain, to match with her Twelve Branch Animals. Each pair of these puppets (i.e. one Holy Virgin and one of the Twelve Branch Animals) appears and disappears for their double-hour. Our model of water-hammering escapement has an error of about 3 min a day. It is hoped that this study will aid in the restoration of Heumgyeonggak-nu.
GEOMAGNETIC FIELD VARIATIONS DURING SOLAR ECLIPSES
KIM, JUNGHEE
We investigate the geomagnetic field variations recorded by INTERMAGNET geomagnetic observatories, which are observed while the Moon's umbra or penumbra passed over them during a solar eclipse event. Though it is generally considered that the geomagnetic field can be modulated during solar eclipses, the effect of the solar eclipse on the observed geomagnetic field has proved subtle to be detected. Instead of exploring the geomagnetic field as a case study, we analyze 207 geomagnetic manifestations acquired by 100 geomagnetic observatories during 39 solar eclipses occurring from 1991 to 2016. As a result of examining a pattern of the geomagnetic field variation on average, we confirm that the effect can be seen over an interval of 180 minutes centered at the time of maximum eclipse on a site of a geomagnetic observatory. That is, demonstrate an increase in the Y component of the geomagnetic field and decreases in the X component and the total strength of the geomagnetic field. We also find that the effect can be overwhelmed, depending more sensitively on the level of daily geomagnetic events than on the level of solar activity and/or the phase of solar cycle. We have demonstrated it by dividing the whole data set into subsets based on parameters of the geomagnetic field, solar activity, and solar eclipses. It is suggested, therefore, that an evidence of the solar eclipse effect can be revealed even at the solar maximum, as long as the day of the solar eclipse is magnetically quiet.
Measuring Characteristics and Performance of a DICE(Diagnostic Coronal Experiment) CCD Camera(QSI 640i)
KIM, JINHYUN
KASI have been developing a Diagnostic Coronal Experiment(DICE) system for total solar eclipse observation. We have tested the characteristics and performance of the DICE CCD camera 640i made by QSI company. For this we have used KASI’s photoelectron detector performance test system. (1) Using a lambertian light source flatted by integrating sphere, we were able to get the image signal value dependent on the exposure time. We have analyzed these images and measured readout noise, intensity and linearity. Using a Photon Transfer Curve(PTC) method, we have obtained CCD’s conversion gain for the 2 gain mode(High:0.7 /ADU, Low:1.5 /ADU) and full well capacity. (2) Using a monochromator that make light of a specify wavelength band, we have measured the quantum efficiency(200nm~1100nm). As a result, we found that the measured conversion gain value(High:0.71 /ADU, Low:1.51 /ADU) was almost similar to the specifications manual provided in QSI. In particular, It was confirmed that the peak value of the quantum efficiency is 55% and measured quantum efficiency was similar to the QSI manual. This test will be an important step in the performance of our next generation coronagraph CCD cameras.
FWHM of Power Excess and Global Seismic Properties of Solar-like Oscillations
Kim, Kibeom
Quantitative and qualitative photometric time series data of solar-like stars are provided by Kepler space mission. Through these data, it is possible to investigate statistical study of seismic properties of oscillating stars. Global seismic properties - large frequency separation (△ν), frequency of maximum power (νmax) and amplitude of Gaussian envelope (A) are widely used to determine empirical scaling relations for inferring the stellar physical quantity – mass, age, temperature. We aim to find the characteristics of width of Gaussian envelope on power excess (δνenv) from main to subgiant sequence stars for confirming whether or not they can be used with parameter of scaling relation. We have demonstrated that δνenv has high correlation with △ν and νmax. We have also found the break of δνenv –△ν and νmax relations.
A new catalogue of galactic eclipsing binary stars in elliptical orbits
Kim, Chun-Hwey
We report that a new catalogue of 623 galactic eclipsing binary (EB) stars in elliptical orbits (EOs) has been compiled. Based on their eclipse timing diagrams all the systems are divided into three groups: (1) 453 systems with constantly displaced secondary minima, (2) 139 systems showing only apsidal motion (AM), (3) 31 systems exhibiting both AM and light-time effect (LITE). The AM parameters of 170 systems (AM and AM+LITE systems) are consistently determined and cataloged with basic information for all systems. The AM parameters are statistically discussed with those for the EB systems with EOs in the Large and Small Magellanic Clouds.
High Resolution Spectroscopic Observation of Symbiotic Stars AG Draconis and UV Aurigae
KIM, Soo Hyun
We present spectral monitoring results for symbiotic stars AG Draconis and UV Aurigae in recent several years. We investigate the characteristics and variations of emission lines by hydrogen Balmer series and significant elements and discuss the changing pattern of Balmer lines according to activity and V magnitude of two symbiotic stars.
NIR High-Resolution Spectroscopy of MWC 1080 by IGRINS: Detection of New Outflows?
Kim, il-joong
Through MIRIS Paa Galactic plane survey, a lot of Paa blobs were found along the plane. To reveal their characteristics, we are planning to collect NIR high-resolution spectroscopic data for the Paa blobs by using Immersion GRating INfrared Spectrograph (IGRINS). Here, we present the IGRINS results for the Herbig Be star MWC 1080, which is one of the Paa blobs detected in Cepheus. This Herbig Be star is known to have many young stellar objects (YSOs) and bright MIR (10-20 µm) nebulosity in its vicinity. From IPHAS Ha data, we found large extended Ha features that correlate well with MIR and 13CO morphologies around MWC 1080. A part of the Ha features shows a bow shock shape to the northeast of the primary star MWC 1080A, which seems to be due to an outflow from the star. We detected faint [Fe II] ?1.644 µm and H2 1-0 S(1) ?2.122 µm emission lines around the bow shock feature. To the east region of MWC 1080A, we also detected strong [Fe II] and H2 emission lines with a couple of velocity components, which suggests the detection of a new outflow from another YSO. Broad Br? ?2.1662 µm line and H2 lines with various velocity components were detected around the bright MIR and Ha nebulosity as well.
Gas infalling motions in the envelopes of Very Low Luminosity Objects
Kim, Mi-Ryang
We present the results of observations toward 95 VeLLOs in optically thick (HCN 1-0) and thin (N2H+ 1-0) lines using both the Korean VLBI Network (KVN) and Mopra telescopes to study inward motions in the envelopes of the VeLLOs. The normalized velocity differences (dV) between the peak velocities of the thick and thin lines were derived from 44 VeLLOs detected in both lines. The dV distribution of these VeLLOs is found to be significantly skewed to the blue, like the case of starless cores, but not as much as that of normal protostars.We selected 25 infall candidates showing infall asymmetry in the line profiles and derived their infall speeds of 0.03 km s-1 to 0.3 km s-1 with a trimmed mean value of 0.15 km s-1 using a HILL5 radiative transfer model. The mass infall rates calculated from these infall speeds are mostly of the order of 10-6 Msun yr-1 with a 10% trimmed mean value of 4.0 x 10-6 Msun yr-1. Thirteen sources out of the infall candidates were found to show typical outflow wing features in HCN profiles. The mass accretion rates for these sources were derived and found to be smaller by 1-2 orders of magnitude than the mass infall rate. This may imply that most of the VeLLOs are currently accreting only a small fraction of mass accumulated from infalling processes. In this process, a major fraction of the infalling material from the envelopes may be accumulated somewhere in accretion disk for the future massive inflow to the central source in an episodic manner. Alternatively, the infalling material may be being mostly ejected in the form of outflow winds before reaching to the central object.
Electromagnetic induction heating of planets orbiting late M dwarfs
Kislyakova, Kristina
We present our results on the induction heating of planetary interiors inside planets orbiting late type M dwarfs with strong magnetic fields. Induction heating arises when the conducting body (in this case, an exoplanet with a conducting mantle) is embedded into constantly varying magnetic field. We consider two cases: in the first one, the planet is supposed to orbit in its host star’s equatorial plane and the varying magnetic field at planetary orbit arises due to an inclination between the stellar magnetic dipole and stellar rotation axis. In the second case, we assume the two axes of the stellar magnetic dipole and the stellar rotation to be coalighned and study induction heating inside planets orbiting on inclined orbits. Our calculations show that induction heating can in some cases melt the upper mantle and enormously increase volcanic activity, sometimes producing a magma ocean below the planetary surface. This conclusion is very important for the planetary habitability, because it influences the outgassing and, thus, also the atmospheric composition of a planet in the habitable zone. It is also important for close-in planets, as induction heating can be very strong close to a star and exceed the energy release inside the Jupiter’s satellite Io, likely leading to a fully molten mantle of such planets and totally changing the energy budget of planetary mantle and planetary interior evolution.
X-ray and radio counterparts of Fermi long-duration gamma-ray events
Klein, Karl-Ludwig
The Fermi spacecraft showed a rather frequent occurrence, and sometimes long duration, of gamma-ray bursts at photon energies above 100~MeV. They are ascribed to pion-decay photons, which in turn requires protons to be accelerated to energies above 300 MeV. This raises the question why the Sun, which is thought to be a modestly skilled particle accelerator, accelerates protons to energies above 300 MeV rather frequently, and where this can happen on occasion during several, up to ten, hours. The HESPERIA project, funded between 2015 and 2017 by the European Union (H 2020 programme), endeavoured to shed light on these questions by a systematic investigation of X-ray and radio emission during the gamma-ray events. We found that the Fermi gamma-ray events are accompanied by signatures of energetic electron acceleration in the corona during the impulsive phase and the early post-impulsive phase. This points to a common acceleration of the relativistic protons with energetic electrons, and is in line with occasional earlier findings. Gamma-ray emission lasting several hours was found to accompany the decay phase of long-lasting soft X-ray bursts, post-flare loop formation and decametric-to-kilometric type~II bursts, revealing shock waves in the high corona. The presence of a type II burst may suggest shock acceleration of the relativistic protons. But the acceleration far from the Sun poses the problem of how to transport the protons back to the chromosphere against magnetic mirroring. An alternative is prolonged trapping of protons accelerated during the first hours of the solar event. This has then to be reconciled with the absence of simultaneous X-ray and radio emission.
PDR Analysis with Far-infrared Diagnostic Lines in M17-SW
Klein, Randolf
Photo-dissociation regions (PDRs) are the places where molecular clouds are destroyed by UV radiation of forming massive stars (eg. Hollenbach & Tielens 1999). The molecular gas is photo-dissociated and then ionized by UV radiation. Photo-electric heating heats the gas in the PDRs. Cooling happens through the dust continuum and a handful of far infrared (FIR) fine-structure lines. FIFI-LS (Colditz et al. 2012), the FIR spectrometer onboard the US-German airborne observatory, SOFIA, can map these main cooling lines efficiently. To study the heating, cooling, physical conditions and destruction rates, we observed the well-studied edge-on PDR, M17-SW with high spatial resolution in all major FIR cooling lines of the ionized and neutral medium. In this pre- sentation, we discuss the fine-structure line and continuum maps observed by SOFIA/FIFI-LS showing the layering in this edge-on PDR. The data allows us to infer physical conditions and the energetics of the interface regions. The continuum maps together with literature data allow us to construct complete spectral energy distributions of the PDR material and the sources embedded in the PDR.
Pebble accretion onto planets in turbulent discs
Kley, Wilhelm
Planets are born in protoplanetary discs growing from very small particles to full-grown planets.In the past years, it has been recognized that the growth process can be sped-up by accreting alarge number of solid, pebble-sized objects that are still present in the protoplanetary disc.It is still an open question how efficient this process is in realistic turbulent discs.In this contribution we present results on the accretion efficiency of pebbles in turbulent discsthat are driven by the purely hydrodynamical vertical shear instability (VSI).We perform global three-dimensional simulations of discs with embedded planets of different massesranging from 5 to 100 Earth masses. Embedded in the flow is a swarm of pebbles in ten size binsthat move under the action of drag forces between gas and particles.For well-coupled particles with unity Stokes number we find an accretion efficiency(rate of particles accreted over particles drifting inward) of about 2% for the lower massplanets. For masses between 10 and 30 Earth masses the core reaches the pebble isolation massand the particles are trapped at the pressure maximum just outside of the planet,shutting off further particle accretion.
Star formation and starbursts in dwarfs
Knapen, Johan
We use a representative sample of over 1500 galaxies that has been imaged in the optical and IR in the Spitzer Survey of Stellar Structure in Galaxies to collect information on their star formation rate (SFR), specific SFR, SFR density, gas content, gas depletion time, stellar mass, morphological type, and whether they are interacting. We calculate values for all these parameters normalised to individualised control samples. This allows us to study how star formation in dwarf galaxies behaves when compared to higher-mass galaxies. We also consider how common starburst definitions can mis-classify when confronted with dwarf galaxies.
Strong gravitational lensing by elliptical and spiral galaxies in modified Newtonian dynamics
Ko, Chung-Ming
Modified Newtonian dynamics (MOND) is a viable alternative to dark matter halo in interpreting the missing mass problem in galaxies. Even if MOND were not a fundamental theory, practically it is an effective way to estimate the baryonic mass of galaxies. We study strong gravitational lensing of galaxies in the framework of MOND. To work out the lensing mass in MOND, we adopt Herquist-like model for ellipticals and Kuzmin-like model for spirals. We compare the lensing mass with baryonic mass deduced from other methods.
Evidence for the existence of abundant intracluster light ~5 billion years after the Big Bang
Ko, Jongwan
Not all stars in the universe are gravitationally bound to galaxies. Observations have clearly revealed that a significant stellar component fills the space between galaxies in nearby galaxy clusters, creating diffuse intracluster light (ICL). However, when and how these stars form are still in debate. Galaxy clusters at the epoch when mature galaxy clusters began to appear are crucial to answer these questions. We present a ICL study of MOO J1014+0038 at z=1.24, using high-quality HST/WFC3 near-IR imaging data that enables us to reach a very low surface brightness threshold (~29 mag arcsec-2) and obtain a clear two-dimensional ICL map out to ~200 kpc from the center of the cluster. We find that the ICL color is consistent with that of the bright, red cluster galaxies. However, unlike the radial color variation of galaxies, we do not detect any significant radial dependence of the ICL color. Using simple stellar population synthesis with an exponentially decaying star formation model, we estimate that the ICL stars had formed at z~2 or earlier. Despite our conservative analysis, the ICL fraction still exceeds ~10% of the total cluster light at r<200 kpc. These results strongly support that intracluster stars might have formed during a short period and early in the history of the Virgo-like massive cluster formation and might be concurrent with the formation of the brightest cluster galaxy.
Chemodynamical simulations of dwarf galaxies
Kobayashi, Chiaki
Using our chemodynamical simulations that include star formation, supernova feedback, and detailed chemical enrichment, we show our zoom-in simulations of satellite galaxies in the Milky Way-size halo. Our simulations are in good agreement with the observed metallicity distribution of stars as well as the evolution of elemental abundance ratios. This story is coupled with the detailed modelling of Type Ia Supernovae (SNe Ia), and we also show the impact of the subclasses of SNe Ia, namely, sub-Chandrasekhar mass SNe Ia and so-called Type Iax SNe.
Constraining the blackhole masses from elemental abundances of nearby stars
Kobayashi, Chiaki
First of all, I will show the contribution of massive stars in galactic chemical evolution, namely, the improtance of hypernovae from >25Msuns stars. Secondly, provided that the interstellar medium was highly inhomogeneous at the early stage of galaxy formation, we constrain the properties of the first supernovae (from <50Msun stars) by directly comparing our nucleosynthesis yields to the observed elemental abundance patterns of extremely metal-poor stars in the solar neighborhood. We have done this abundance fitting analysis for ~200 stars, and the predicted mass distribution has a double peak at ~6 and ~10 Msun. Finally, I will discuss the contribution from stars with >50Msun by searching very low [alpha/Fe] stars in the Milky Way.
Evolutionary Description of Molecular Cloud Mass Functions and Metal Distribution in the Multiphase Medium of Milky Way and Nearby Spiral Galaxies
Kobayashi, Masato
Recent radio surveys to nearby galaxies highlight the distribution of giant molecular clouds across galactic disks, which indicate that massive clouds preferentially reside along the galactic spiral arms (e.g., Koda et al., 2014, Colombo et al., 2014). Magneto-hydrodynamics simulations of the multiphase interstellar medium suggest that multiple episodes of supersonic compression is an essential process to form molecular clouds from the magnetized warm neutral medium in galactic disks (e.g., Inoue & Inutsuka 2008, 2012, Valdivia et al., 2016). We formulate a semi-analytical equation that governs time evolution of the differential number density of giant molecular clouds. This formulation considers cloud formation and mass growth due to multiple episodes of compression, cloud self-dispersal due to stellar feedback, cloud-cloud collisions, and gas resurrection. Our results indicate that the single power-law slope in the low-mass regime (less than 10^5.5 Msun) is determined by the ratio of timescales (mass growth and self-dispersal). Mass flux analyses show that there is a one to one mapping between the power-law slope and the gas resurrection rate that properly reproduces observed mass functions. Thus measuring the slope could be a powerful tool to constrain such timescales and gas resurrection across various galactic environment.In addition, we evaluate the star formation rate driven by cloud-cloud collisions and suggest that collision may amount to a few 10 percent of total star formation in a galactic disk. However, our results also suggest that collisional events between massive clouds whose mass are larger than 10^6 Msun is rare, thus further large surveys are needed to evaluate the importance of cloud-cloud collision driven star formation.Lastly, we evaluate metal production due to star formation coupled with our model of time evolution of molecular cloud mass functions and discuss the expected metal distribution as a function of galacto-centric radii.
Optical Monitoring of High Mass X-ray Binary Systems with Black Hole Component
Kocak, Dolunay
We presented long term optical observations of the selected high mass X-ray binaries with black hole components. New observations obtained by using the 1m and 0.6m telescopes at the TÜBITAK National Observatory (TUG). Photometric behaviors of the systems are analyzed and compared with the earlier published results. We will discuss new observations results in this study.This study is supported by the Turkish Scientific and Research Council-TÜBITAK (117F118). We thank to TUBITAK for a partial support in using T100 and T60 telescope with project number 15AT60-775, 15CT100-916 and 17BT100-1204.
Optical Monitoring of High Mass X-ray Binary Systems with Black Hole Component
Kocak, Dolunay
We presented long term optical observations of the selected high mass X-ray binaries with black hole components. New observations obtained by using the 1m and 0.6m telescopes at the TÜBITAK National Observatory (TUG). Photometric behaviors of the systems are analyzed and compared with the earlier published results. We will discuss new observations results in this study.This study is supported by the Turkish Scientific and Research Council-TÜBITAK (117F118). We thank to TUBITAK for a partial support in using T100 and T60 telescope with project number 15AT60-775, 15CT100-916 and 17BT100-1204.
From Filaments to Molecular Clouds and Protostellar Systems - what is the Role of the Magnetic Field?
Koch, Patrick
The role of the magnetic (B-) field in the star-formation process is highly debated. How important is the magnetic field in the presence of gravity and turbulence? Conclusive observational results have been scarce due to both limited available data anddue to the generally challenging measurements requiring very sensitive observations.We present observational results illustrating the role of the B-field on three representative scales in the star-formation process: (1) the filamentary-scale infrared dark cloud G34.Here, the local B-field correlates with the local velocity gradients on the largest scales.Based on a benchmark analysis that quantifies the various energy components we arguethat a different relative importance between B-field, turbulence, and gravity leads to different observed fragmentation types on a next smaller scale; (2) the molecular-cloud-scale in the high-mass star-forming region W51. Here, increasingly higher resolutions fromthe SMA to ALMA resolve new B-field sub-structures. In particular, we see zones of symmetrically converging B-field lines, cometary-shaped satellite cores, local collapse features, and a possible new phenomenon of magnetic channelling; (3) the protostellar-source-scale in B335. Here, we provide evidence for magnetic braking from detailed high-resolution observations of the kinematics of neutral and ionized gas tracers. Besides these textbook cases on three different scales, we further present statistical resultsfrom a 50-source sample of molecular clouds that reveal generic B-field features and a systematically locally varying importance of the B-field versus gravity.
Chemistry of hydrogen isotopologues in the ISM: similarities and differences
Kochina, Olga
Since observational technologies allow astronomers to get detailed molecular spectra of cold dense clouds, the presence of isotopologues in the ISM is being discovered. A common approach to taking into account such extraordinary species in numerical modeling is computing chemistry of the main isotopologue and then considering the abundance of a specific isotopologue being a fraction of the main one corresponding the isotope ratio for a definite atom. In order to validate the accuracy of such approach, the detailed chemistry of deuterium-bearing species was studied. Evolution of abundance of the species was compared to that of main isotopologues. As surface chemistry is highly important for evolution of molecular compound in cold dense cloud, chemistry was additionally detailed by considering complex dust compound [1] in the simulations. The results show that for some of the deuterium-bearing species evolution differs from the one for main isotopologues, and ratios of abundances of isotopologues on each step do vary and may differ from general isotope ratio. Evolutionary ways of some astrochemicaly important isotopologues and origins of the differences were studied and are presented here. The study was supported by RFBR, research project No. 16-02-00834 a.[1] Different-sized dust grains and the chemical evolution of protostellar objects. Kochina, O.V. & Wiebe, D.S. Astron. Rep. (2014) 58: 228.
Angular momentum and central mass-concentration of galaxies
Kodaira, Keiichi
Kalinova, V. and Kodaira, K. : We present a correlation study among the global galaxy parameters given in Kalinova et al. (2017, MNRAS, 469, 2539) which introduced Circular-Velocity-Curve (CVC) classes basing upon the stellar kinematics of CALIFA galaxies. Most of global parameters (age, metallicity, bulge/disk-ratio, maximum circular velocity, line-of-sight velocity dispersion, or stellar-mass surface- density) in average monotonously increase with the stellar mass, log M*, with a slight bend around log M0* (in M?) ~10.8. , while the angular momentum (or azimuthal velocity) of stellar system turns to decrease beyond M0* towards higher mass. This trend-change is also obvious in log (M*/Mdyn) vs. log (M*) diagram, indicating physical influences of invisible mass (gas, dust, dark matter halo, central massive black hole) to the mechanism of angular momentum supply/dispersal of forming galaxies. Log-log diagram of the star formation rate (SFR) vs. M* is known to show a prominent jump around the mass range ofM0*, which corresponds to the GRREN VALLEY in the color-mass /luminosity diagram of nearby galaxies, indicating SF-quenching on the high-mass side of M0*. By defining an index of the steepness of inner part of CVC, Vs, which represents the degree of the central mass concentration, we find that log M* vs. log Vs diagram shows the same kind of jump around M0*. These interrelations support the working hypothesis that high-mass concentration beyond M0* led to formation of active BH at the center of galaxies, which dispersed the angular-momentum-carrying baryon, to quench SF activity in an early epoch of galaxy formation. Kinematical aspect of the trend-change around M0*will be explored by introducing phase-space-density parameter for stellar-particle ensembleand referring to mass-radius relation of galaxy stellar system.
Simulating JWST Mosaic Imaging Science Observations
Koekemoer, Anton
An increasingly important aspect of planning observations and interpreting the results involves carrying out simulations to quantify the necessary sensitivities that need to be achieved, and examine the impact of potential observational biases and instrumental effects. For imaging observations with JWST, a framework is being developed to perform simulated observations of various different types of astronomical targets, using realistic observing programs as a starting point, with input scenes based on catalogs or pre-existing images, and producing realistic exposures that include telescope optics and instrumental detector effects. These exposures are then passed through the JWST pipelines to produce simulated mosaic products, which can be compared with the original inputs to quantify the impact of various effects (including instrumental effects such as detector noise or calibration uncertainties, as well as enabling astrophysical effects such as biases due to different source population properties). Current examples of simulated mosaics are presented with initial results for JWST NIRCam, as well as prospects for other instruments.
The Hubble Space Telescope Frontier Fields Program
Koekemoer, Anton
[This abstract is for the Mini-symposium IV/V "Build-up of Galaxy clusters" on 27 Aug 2018]The Hubble Space Telescope Frontier Fields program is a large Director's Discretionary program of 840 orbits, to obtain ultra-deep observations of six strong lensing clusters of galaxies, together with parallel deep blank fields, making use of the strong lensing amplification by these clusters of distant background galaxies to detect the faintest galaxies currently observable in the high-redshift universe. The entire program has now completed successfully for all 6 clusters, namely Abell 2744, Abell S1063, Abell 370, MACS J0416.1-2403, MACS J0717.5+3745 and MACS J1149.5+2223,. Full sets of high-level science products have been generated for all these clusters by the team at STScI, including cumulative-depth data releases during each epoch, as well as full-depth releases after the completion of each epoch. These products include all the full-depth distortion-corrected drizzled mosaics and associated products for each cluster, which are science-ready to facilitate the construction of lensing models as well as enabling a wide range of other science projects. Many improvements beyond default calibration for ACS and WFC3/IR are implemented in these data products, including corrections for persistence, time-variable sky, and low-level dark current residuals, as well as improvements in astrometric alignment to achieve milliarcsecond-level accuracy. The full set of resulting high-level science products and mosaics are publicly delivered to the community via the Mikulski Archive for Space Telescopes (MAST) to enable the widest scientific use of these data, as well as ensuring a public legacy dataset of the highest possible quality that is of lasting value to the entire community.
A New Package to Simulate Quasar Microlensing
Koeller, Jordan
Numerical simulation of gravitationally microlensed quasars provides a tool to determine the physical size and temperature profile of quasars’ accretion disks, which is impossible through direct observation. Additionally we learn about the dark matter distribution of lensing galaxies by characterizing the frequency of microlensing-induced anomalies. In order to use microlensing as a tool, we develop a robust, large-scale simulator, written in Python, to model gravitationally lensed quasar source objects. The method consists of ray-tracing approximately 10^9 paths through a simulated starfield, taking advantage of the latest technologies in cluster computing, to calculate flux received by the observer from each lensed image from different regions of the accretion disk as the quasar moves relative to the lensing galaxy. We compare our simulations to observations of QSO2237+0305 in optical and X-ray wavebands to place constraints on the size of the quasar’s accretion disk.
Perseid meteoroids by the Tajikistan fireball network observations. I. Dynamical features
Kokhirova, Gulchehra
Fireball observations were started in the Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan in 2006. The network consists of 5 stations situating on the south part of the Tajikistan territory and covering the area of near eleven thousands square kilometers. The mutual distances between them range from 53 to 184 km. The stations are equipped by the all-sky cameras with the Zeiss Distagon "fish-eye" objectives (f=30 mm, D/f =1:3.5) using sheet films and by the digital SLR cameras "Nikon D2X" and "Nikon D300" with the Nikkor "fish-eye" objectives (f=10.5 mm, D/f=1:2.8). The all-sky cameras provide us with photographic data about meteors brighter than -4 magnitudes, which are called fireballs. Astrometric and photometric reduction procedures the same as in the European Fireball Network (EN) are using. Photographic observations of the Perseid meteor shower activity were carried out by the Tajikistan fireball network at the maximum of the shower during 2007-2011. 29 Perseid fireballs were registered over this period. The fireballs were produced by meteoroids with sizes larger than small dust particles which form usual meteor phenomenon. As a result of astrometric and photometric reduction of the obtained observational data the atmospheric trajectories, velocities, orbits, light curves of fireballs as well as the photometric masses and densities of meteoroids were determined. Detected fireballs present sufficient data set for analysis of physical and dynamical properties of the large-sized Perseid meteoroids. The results of investigation of their dynamical features are presented in this paper. It is shown that detected Perseid activity was caused by both the Perseid filament and annual shower activity.
Dynamical and physical properties of presumed meteorite-dropping fireballs photographed by the Tajikistan fireball network
Kokhirova, Gulchehra
The systematic double-station observations of fireballs were started in the Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan in 2006 with the aim to study the large-sized meteoroids penetrating the Earth's atmosphere. Obtained experience and results have stipulated the organization of the fireball network in 2008. The network consists of 5 stations situating on the south part of the Tajikistan territory and covering the area of near eleven thousands square kilometers. The mutual distances between them range from 53 to 184 km. The stations are equipped by the all-sky cameras with the Zeiss Distagon "fish-eye" objectives (f=30 mm, D/f =1:3.5) using sheet films and by the digital SLR cameras "Nikon D2X" and "Nikon D300" with the Nikkor "fish-eye" objectives (f=10.5 mm, D/f=1:2.8). The all-sky cameras provide us with photographic data about meteors brighter than -4 magnitudes, which are called fireballs. More than 400 multi-station fireball images including digital ones were photographed by the network in the period 2006-2012. The geometrical conditions for 230 multi-station fireballs were good enough to compute reliable trajectories. Astrometric and photometric reduction procedures the same as in the European Fireball Network (EN) are using. Digital fireball images were measured using the Ascorecord measuring software "FISHSCAN" developed by Dr. J. Borovicka. 25 meteorite candidates, i.e. fireballs that may have dropped meteorites, were identified among processed fireballs. In this work, we present complete and precise data on their atmospheric trajectories, radiants, orbits and light curves. The physical properties such as preatmospheric and terminal masses, densities of the substance of presumed meteorite-dropping meteoroids are considered as well. Strong correlations have found between dynamical and physical features allow describing parameters of typical meteorite event.
Exploring The Universe from west Africa
Kolenberg, Katrien
In Senegal astronomy is only known through outreach activities organized by local amateurs, even if the university sometimes hosts guest lectures in astronomy. My PhD thesis fits into the framework of setting up professional astronomy in Senegal, and it is part of a continental-wide Initiative for Planetary and Space Sciences (http://africapss.org).A partnership has been established for this project between the University of Cadi Ayyad in Morocco, the University Cheikh Anta Diop in Senegal, the Observatories of Paris and Midi-Pyrénées in France, and the University of Antwerp in Belgium.I will spend the first year of my PhD mostly in Belgium, getting acquainted with astronomy research and procedures for astronomical observations, while following the developments of the setup of a local observatory in Senegal, in collaboration with the Ministry for Research, Higher Education and Innovation of Senegal, and the Senegalese Association for the Promotion of Astronomy. Solar system research, exoplanets characterization, survey of variable starts are possible research topics where high-level contributions are possible with modest telescopes.
Steady orbits of Small Solar System bodies and some aspects of Alfven-Arrhenius concept about evolution of Solar system
Kolomiyets, Svitlana
In connection with the accumulation of a huge amount of new observational data on the Solar system and exoplanets, the introduction of modern information technologies in the methods of researching a large amount of data, and also with obtaining new knowledge about the Universe, it is time to turn once again to some theories of the past about the structure and evolution of planetary systems. There was the Alfven-Arrhenius concept about the structure and evolution of the Solar system (Alfven&Arrhenius 1998). For the researchers of Small Solar system bodies, the Alvfen-Arrhenius concept is attractive in that it pays much attention to the analysis of the origin and development of the class of small bodies of the Solar system (asteroids, comets, meteoroids). We have examined some aspects of the Alfven-Arrhenius concept regarding the evolution of small bodies. The purpose of our study was to identify in the distributions of selected elements of the orbits of small bodies of the Solar System a fine deterministic structure associated with the evolution of their orbits. For this purpose, the distributions of orbital elements of near Earth objects (Near Earth Asteroids - NEA, Near Earth Comets - NEC and meteoroids in the Earth's atmosphere) were analyzed. To analyze the selected data, a modified method was used to extract a useful signal from a noisy sample and some other methods (Cherkas et al. 2014). As a mathematical model, a time series model was adopted. It can be said that the conducted research does not deny the existence of steady periodicity in the distribution of our samples of Small Solar system bodies (ie, the presence of regions with an increased and lower concentration of their orbits). There are grounds to assert that not only the process of decay of larger bodies into smaller components can occur in the Solar system, but also the formation of steady orbits on which the accretionary aspect of the Alfven-Arrhenius concept (substance pooling) looks quite logical.
Peculiarities of the distribution of meteor radiants on the celestial sphere for meteoroids with asteroid-type orbits
Kolomiyets, Svitlana
From a database of sporadic meteors of the Kharkiv National University of Radio Electronics with a volume of about 160,000 meteor orbits, samples of meteoroid's orbits of asteroidal and cometary type were formed. The selection was carried out in accordance with the well-known formal criteria of Whipple and Kresak. The number of meteoroids with asteroid-type orbits (84%) turned out to be higher than that of meteoroids with orbits of cometary type (16%). The 63% of meteoroids with asteroid-type orbits have a direct movement. The 83% of meteoroids with orbits of cometary type have a direct movement. For cometary and asteroidal meteoroids, the distributions of radiants on the celestial sphere were constructed. Similar distributions were also constructed for some special samples of meteoroid's orbits. We analyzed the distributions for different celestial coordinate systems. In analyzing the constructed distributions, some peculiarities of the distribution of meteor radiants on the celestial sphere for meteoroids with asteroid-type orbits were found. These peculiarities are discussed. Some questions concerning the asteroidal and cometary origin of meteoroids are discussed. The results of the research are of interest from the point of view of solving the problems of the asteroid hazard and the Small Solar system bodies evolution.
Subaru Hyper Suprime-Cam Survey for the Local Group Dwarf Galaxies: Ursa Minor
Komiyama, Yutaka
We have carried out a wide and deep imaging survey for Local Group dwarf galaxies using Hyper Suprime-Cam (HSC) which is a 1 Giga pixel CCD camera with 1.5degrees field of view attached to the prime focus of the 8.2-m Subaru Telescope. The high spatial resolution (0.4 arcsec for the best condition, 0.67 arcsec for median) and high sensitivity provided by the Subaru Telescope on Maunakea, Hawaii makes HSC the most powerful instrument for exploring the Local Group galaxies with large apparent sizes. The survey data are used for the target selection of the future Prime Focus Spectrograph survey which is planned to start in 2021.In this presentation, we show the result for the dwarf spheroidal galaxy Ursa Minor (UMi) for which HSC covers out beyond the nominal tidal radius down to ~25 mag in i-band, which is ~2 mag below the main sequence turn-off point. The structure of UMi is investigated for individual stellar component such as red-giant branch stars, blue horizontal branch stars, etc. The structural parameters are estimated and the tidal radius is suggested to be larger than those estimated by the previous studies. The fraction of binary stars of UMi is investigated from the morphology of the main sequence following the method described in Sollima et al. (2007) and Milone et al. (2010). The CMDs of binary systems can be calculated by making use of the isochrone of the representative stellar population (i.e., age and metallicity), the initial mass function, and the binary mass distribution of the system. By comparing the simulated CMDs of different binary fractions with the observed CMD, the fraction of binary systems in UMi is estimated to be ~0.4. The value is consistent with those estimated for the other Local Group dwarf spheroidal galaxies based on the radial velocity measurements, but slightly higher than those derived for the most Galactic globular clusters by the same method.
Spectroscopic Observation and Analysis of H II Regions in M33 with MMT: Oxygen Abundances
Kong, Xu
"Spectroscopic Observations of the HII Regions In Nearby Galaxies" is a project, which perform spectroscopic observations on HII regions in 20 nearby large galaxies since 2008 via the NAOC2.16 m telescope and the Multiple Mirror Telescope (MMT). In each galaxy, spectra of hundreds of HII regions were observed, and a homogeneous spectrum sample was obtained. In this talk, we will report the the spatial distribution of gas-phase oxygen abundances in M33, with the homogeneous spectra sample of 413 star-forming (or H II) regions in M33, which were observed using the multifiber spectrograph of Hectospec at the 6.5 m Multiple Mirror Telescope.
The Radio Telescopes in Miyun Station of the National Astronomical Observatories
Kong, Deqing
In 1999, after the Miyun Synthesis Radio Telescope (MSRT) finishes its main scientific goal, the meter-wave radio source survey, Miyun radio group proposed to construct a more multi-function 50 m radio telescope for both radio astronomical observation and space communications in 2002. The 50 m radio telescope (MRT50) was put into test operation in 2005 and was passed its final reception test in 2006. MRT50 is equipped with S/X, Ku-bands and also low frequencies such as 300and 610MHz. Because of strong interference in this region, the low frequencies are hardly used. From 2007, the main task of MRT50 is to get the downlink data of the Chang’E-1, 2 and 3 probes in the Chinese Lunar Exploration Program. Except for receiving lunar scientific data, a lot of the VLBI observations to measure the probes orbits, have been done organized by Shanghai observatory. Also a lot of interplanetary scintillation (IPS) and pulsar observations were carried on. The 40 m radio telescope (MRT40) was put into test operation and passed its final reception test in 2017, which is mainly used for Chang’E-5 mission, the first Mars exploration mission of China and other astronomical observations. MRT40 is equipped with S/X, Ku-bands. In the Mars Exploration mission to be launched in 2020, MRT50 and MRT40 at Miyun Station, the 70 m radio telescope (WRT70) at Wuqing Station, and the 40 m radio telescope (KRT40) at Kunming Station will be used as antenna array to receive the downlink data. The MRT50 and KRT40 arraying experiments have been implemented using the downlink signal of Chang’E-3 pobe in 2016, which the combining efficiency is greater than 93%.
Solar Irradiance: Instrument-Based Advances
Kopp, Greg
Variations in the total solar irradiance (TSI) over long periods of time potentially provide natural Earth-climate forcing and are thus important to measure. Variations over a solar cycle are at the 0.1% level. Variations on multi-decadal to century timescales, if extant, are fortunately very small, which thus drives the need for highly-accurate and stable measurements over correspondingly long periods of time. Advances to TSI-measuring space-borne instruments are striving to achieve the desired climate-driven measurement accuracies and stabilities. I will present a summary of the modern-instrument improvements intended to enable these measurements and show some of the solar-variability measurement results recent space-borne instruments have acquired, including solar variability from solar-flare and solar-convection to solar-cycle timescales.
How well do we understand the wind properties of FS CMa class of the B[e] stars?
Korcakova, Daniela
FS CMa stars are low luminosity near main sequence stars of intermediate mass showing the B[e] phenomenon, that are located far from the star-forming region. These stars are surrounded by geometrically thick disks (inferred from their spectra and, for HD 50138, from interferometric imaging), whose origin and dynamics are not yet well understood. In particular, their inferred mass loss rate is high relative to "normal" Be stars with observed speed velocities about a few hundreds of km/s. Many are also spectroscopic variable on timescales ranging from days to decades. Modeling has proven difficult, in large measure for lack of observations over the past decade or so. Yet sporadic observations of high resolution and S/N ratio do exist in archives and also from monitoring programs. We present constrains based on line profile diagnostic for a sample of about ten of these stars. We estimate the differential flow characteristics (ionizations, densities, and velocities) in the circumstellar matter. Special attention is paid to non-LTE effects, the level coupling for the most critical cases is emphasised. We also discuss the importance of previously noted but unexploited diagnostics, e.g., Na I D emission and multiple absorption components and its comparison with Fe II, the O I multiplets, and the comparison of He I and hydrogen line profiles. Our data, for example, show that there is a strong coupling between Pashen and Balmer lines that can be used as a wind diagnostic. We also present the overview of the time variability at different scales, in order obtain restrictions of the system dynamics.
OPTICON Schools
Korhonen, Heidi
The main educational component of the EU Funded Optical Infrared Coordination Network for Astronomy (OPTICON) is organised through its Work Package 12 (WP12): 'Enhancing community skills, Integrating communities'. WP12 runs a community training programme which delivers expert knowledge in infrastructure use and development, and helps to integrate newer communities. The main programme consists of a yearly NEON Observing school, giving hands-on observing experience to young astronomers at a professional telescope. Additionally, OPTICON organises other schools concentrating on different aspects of observational astronomy, life-long learning, and integrating communities. These schools can have different scopes, for example 'Hot Topics', astronomical instrumentation, or combining data from different wavelength domains. Here, I will outline the OPTICON WP12 activities for the duration of the current OPTICON grant, running the years 2017-2020.
Neutral Hydrogen in Nearby Dwarf Galaxies
Koribalski, Baerbel
I will present the gas content, kinematics and star formation observed in nearby dwarf galaxies (D < 10 Mpc), based on the Local Volume HI Survey (LVHIS, Koribalski et al. 2018) and similar interferometric surveys. The LVHIS sample consists of nearly 100 galaxies, including new discoveries, spanning a large diversity in size, shape, mass and degree of peculiarity. The hydrogen properties of dwarf galaxies in two nearby groups, Sculptor and CenA / M83, are presented and compared with many rather isolated dwarf galaxies. Around 10% of LVHIS galaxies are transitional or mixed-type galaxies (dIrr/dSph), the formation of which is explored. I will also give a brief update on WALLABY Early Science, which has focussed on HI in galaxy groups and clusters, based on observations with wide-field (30 sq degr) ASKAP Phase Array Feeds.
The kinematics of large HI disk galaxies
Koribalski, Baerbel
The Local Volume HI Survey (LVHIS; Koribalski et al. 2018) provides detailed hydrogen intensity and velocity maps of nearby galaxies, typically extending a factor 2-3 beyond the known stellar disk. The shape and kinematics of the outer disks is of particular interest, tracing the dark matter content to large radii, and allowing for detailed comparison with galaxy evolution models. New galaxy surveys, such as WALLABY - the ASKAP HI All Sky Survey - which is expected to detect more than 500 000 galaxies (-90 degr < DEC < +30 degr), will contribute to mapping the galaxy large scale structure in the nearby Universe. About 5000 of the WALLABY detected galaxies are expected to be well resolved and will be run through robust kinematic modelling pipelines (e.g., Kamphus et al. 2015, Oh et al. 2018).
Characterization of extrasolar multi-planet systems by Transit Time Variation
Korth, Judith
Transit Time Variation (TTV) is the earlier or later occurrence of a planetary transit across the stellar disk relative to the time of a reference transit. TTV is dominantly caused by third body orbit perturbations by attracting forces acting on the transiting planet by at least one another planet inside or outside of the orbit of the known transiting planet. Gravitational interactions perturb the velocity of the transiting planet in its orbit which manifests in a periodical perturbation of the revolution period. Measurements of the transit times and the identification of differences from a mean transit period may prove the existence of further planets. The TTV is therefore a tool to confirm planetary candidates in multi-planet systems. Even non-transiting planets can be detected by the analysis of the TTV of a transiting planet. Their orbital elements can be estimated if the TTV is sufficiently resolved. The shape of the TTV curve, the sequence of the individual transit time differences as a function of observing time, depends on the orbital elements of the planet(s) in the system and may show very complex structures.Upcoming spaced-based surveys will observe various stars for which the usual planetary mass determination by ground-based radial velocity observation is not always possible. TTV is an alternative method for orbit determination which uses only the information from the light curve.
Spots, flares, accretion, and obscuration in the pre-main sequence binary DQ Tau
Kospal, Agnes
Pre-main sequence stars are intimately linked with their circumstellar material. This relationship manifests in a variety of phenomena that makes young stars highly variable at a wide range of wavelengths. The photometric variability of young stars can be traced back to four main origins: variable accretion, rotational modulation due to hot or cold stellar spots, variable line-of-sight extinction, and stellar flares. Here we present results on a very special young star, DQ Tau, which displays all of these effects. Thanks to the unprecedented precision of Kepler K2 and Spitzer data, we could separate the signature of the individual effects. DQ Tau is a young low-mass spectroscopic binary, consisting of two almost equal-mass stars on a 15.8 d period surrounded by a circumbinary disk. Our light curve analysis revealed that the rotational modulation appears as sinusoidal variation with a period of 3.017 d. In our model this is caused by extended stellar spots 400 K colder than the stellar effective temperature. During our 80-day-long monitoring we detected 40 stellar flares with energies up to 1.2 x 10^35 erg and duration of a few hours. The flare profiles closely resemble those in older late-type stars, and their occurrence does not correlate with either the rotational or the orbital period. We observe elevated accretion rate up to 5 x 10^-8 M_Sun/yr around each periastron. Our Spitzer data suggests that the increased accretion luminosity heats up the inner part of the circumbinary disk temporarily by about 100 K. We found an inner disk radius of 0.13 au, significantly smaller than expected from dynamical modeling of circumbinary disks. Interestingly, the inner edge of the disk is in corotation with the binary's orbit. DQ Tau also shows short dips of <0.1 mag in its light curve, reminiscent of the well-known "dipper phenomenon" observed in many low-mass young stars
Mass transport from the envelope to the disk of V346 Nor: a case study for the luminosity problem in an FUor-type young eruptive star
Kospal, Agnes
A long-standing open issue of the paradigm of low-mass star formation is the luminosity problem: most protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Ori-type stars (FUors) are thought to be the visible examples for objects in the high accretion state. FUors are often surrounded by massive envelopes, which replenish the disk material and enable the disk to produce accretion outbursts. However, we have insufficient information on the envelope dynamics in FUors, about where and how mass transfer from the envelope to the disk happens. Here we present ALMA observations of the FUor-type star V346 Nor at 1.3 mm continuum and in different CO rotational lines. We mapped the density and velocity structure of its envelope and analyze the results using channel maps, position-velocity diagrams, and spectro-astrometric methods. We found that V346 Nor is surrounded by gaseous material on a 10,000 au scale in which a prominent outflow cavity is carved. Within the central ~700 au, the circumstellar matter forms a flattened pseudo-disk where material is infalling with conserved angular momentum. Within ~350 au, the velocity profile is more consistent with a disk in Keplerian rotation around a central star of 0.1 M_Sun. We determined an infall rate from the envelope onto the disk of 6 x 10^-6 M_Sun/yr, a factor of a few higher than the quiescent accretion rate from the disk onto the star, hinting at a mismatch between the infall and accretion rates as the cause of the eruption.
Probing the building blocks of galaxies: sub-galactic scaling relations between X-ray luminosity, SFR and stellar mass.
Kouroumpatzakis, Konstantinos
We explore the tight correlation between the X-ray luminosity from high mass X-ray binaries (HMXBs), star formation rate (SFR), and stellar mass using the Star-Formation Reference Survey (SFRS), a sample of galaxies representative of the star-formation activity in the local Universe. We measure these relations with archive X-ray Chandra and XMM observations and a comprehensive set of star-formation (radio, FIR, 24µm, 8µm, Ha, UV, SED fitting) and stellar mass (K-band, 3.6 µm, SED fitting) indicators. We investigate the X-ray luminosity – SFR – stellar mass scaling relations down to sub-galactic scales of ~1 kpc2, extremely low SFRs (~10-6 Msol/yr) and stellar masses (~104 Msol). Using different age-sensitive SFR indicators, we quantify the scatter and dependence on the age of the local stellar populations. These results importantly set the benchmark for the formation of X-ray binaries in vigorous, but low SFR galaxies in the early Universe.
Circumstellar disk fragmentation and the origin of massive planetary companions and free-floating Jupiters
Kouwenhoven, M.B.N. (Thijs)
Most of the Sun's nearest neighbors are M-type stars or brown dwarfs. Constraining the origin of such systems, in particular of those of brown dwarfs hosting a brown dwarf or massive planet as a companion, remains a challenge. Here, we present circumstellar disk fragmentation as a possible mechanism for such systems, based on numerical simulations. Circumstellar disk fragmentation results in the formation of multiple companions of varying mass (from super-Jupiters to low-mass stars) in wide and highly unstable orbits. The decay of these systems results in the ejection of massive planets and brown dwarfs, and in frequent physical collisions. Billions of years after formation, the host stars are often left with none, one, or two companions, with a large variety of configurations, including two types of hierarchical triples with predictable (and measurable) orbital configurations. Despite the unknown frequency of occurrence, circumstellar disk fragmentation is able to predict many of the challenging stellar and substellar systems in the solar neighborhood, and provides predictions for the properties of hierarchical systems containing brown dwarfs and massive planets.
Exploring the missing baryons using absorption studies
Kovacs, Orsolya
In the low-redshift (z<2) universe, about one-third of the baryons remain unaccounted for, which poses the long-standing missing baryon problem. The missing baryons are believed to reside in filaments connecting galaxies in the form of warm-hot intergalactic medium (WHIM). Although UV absorption studies explored the warm phase (T < ~105 K) of the WHIM, it is hypothesized that notable fraction of the missing baryons are in the hot (X-ray) phase (T > ~5 x 105 K ). However, X-ray spectroscopy is limited by the low effective area of currently available instrumentation, thus the conclusive observational evidence is still lacking. In this work, we utilize Chandra LETG spectra of luminous AGN, along with previous redshift measurements of UV absorption line systems, and apply a stacking method to gain unparalleled sensitivity. Based on the stacked data, we probe the most abundant helium-like and hydrogen-like metal lines in the spectra of AGN. In addition, we constrain the contribution of the WHIM to the overall baryon budget.
Star formation in dwarf galaxies in the ELAIS N1 field
Kovács, Tímea Orsolya
The European Large Area ISO Survey (ELAIS), which was one of the biggest open-time projects of the Infrared Space Observatory (ISO), has covered a total of 12 square degrees on the sky, and measurements were taken in four different bands (in a wavelength range of 6.7-175 µ m). The survey consisted of multiple smaller regions, and one of these regions was the ELAIS N1 field. ELAIS N1 became one of the most known regions on the sky thanks to multiple follow up surveys which were carried out in different wavelength ranges, from the optical to the radio.We have chosen dwarf galaxies in the ELAIS N1 field, and fitted their Spectral Energy Distributions (SED) with the SED fitting code CIGALE (which was developed by the Laboratoire d'Astrophysique de Marseille).We used data from the new Herschel SPIRE and PACS Point Source catalogues, to add data points in the far infrared, so we can constrain the emission of the dust surrounding young stars, and give a better estimation on the star formation rate. Data available in VIZIER from multiple surveys (WISE, SDSS and surveys specific to this region) have also been used.CIGALE can be used in a broad wavelength range, and it is very modular, different modules can be chosen for the different processes and mediums in galaxies. With the SED fittings we determined several parameters of the galaxies, including their star formation rate and dust mass.
Parameters of GRB host galaxies based on CIGALE SED fitting
Kovács, Tímea Orsolya
Gamma ray bursts (GRB) are the most luminous known events in the gamma ray sky, they are sudden flashes which are strongest in the gamma range, and can be observed up to high redshift. GRBs can be divided into four groups based on their duration: short, long, intermediate and ultralong. Long GRBs (LGRB) are emitted at the end of the lives of massive stars, during supernova explosions. Because these massive stars are very short lived, LGRBs can indicate star formation in distant galaxies.It is crucial to have observations in the far infrared to constrain the dust emission, and with that the star formation rate of these galaxies. So we determined Herschel fluxes and upper limits from Herschel intensity maps, and together with photometric data collected from the literature and databases we fitted the spectral energy distributions of these GRB hosts with CIGALE (Code Investigating GALaxy Emission), a spectral energy fitting software package developed by the Laboratoire d'Astrophysique de Marseille.CIGALE has multiple models for different physical processes in galaxies, and can handle a wide wavelength range from the UV to the radio. We determined different parameters of GRB hosts, for example the stellar mass, the dust mass, the luminosity and star formation rate. We compared the results with the main sequence of galaxies and with the results of previous articles.
Infrared photometry of GRB host galaxies with deblending algorithm
Kovács, Tímea Orsolya
Gamma ray bursts (GRB) are the most luminous events in the gamma ray sky. The longest GRB signal the death of very massive stars and are observed up to redshift 9. Many of their host galaxies have been observed spectroscopically and most of them have been observed with the X-Shooter spectrograph of VLT. Another method to calculate the parameters of galaxies is to fit their Spectral Energy distributions (SED). This method offer the best results when using Infrared data which are of paramount importance to determine host parameters, especially the star formation rate. However, the best understanding of the host parameters is obtained joining spectroscopy and SED fitting.The aim of this work is to enlarge the sample of hosts with IR detection and X-Shooter spectroscopy. Therefore, from the X-Shooter sample we chose GRB hosts with observations from the Spitzer Space Telescope, and carried out source detection and photometry on Spitzer images with the IDL code CuTEx (CUrvature Thresholding EXtractor). CuTEx was developed to perform photometry on crowded fields observed with the Herschel space telescope. The code finds sources on second derivative maps, and then fits the close sources simultaneously with 2D Gaussians.We compared fluxes of the GRB hosts obtained with multiple methods: i) with the photometry routine in CuTEx; ii) aperture photometry on images without the contaminating sources, removed using model images obtained from the parameters of the Gaussians fitted by CuTEx.When possible we compared the results with the literature. These results will be used to fit the SEDs of the host galaxies, that will be later compared with the results obtained from the analysis of X- Shooter spectra. Thanks to this work, we increased the number of hosts with IR detection and obtained more robust photometry for most of the other hosts.
Dynamical evolution of Damocloids family
Kovalenko, Nataliya
The orbital evolution of 144 Damocloids and their model clones (12 for each real object, a total of 1872 test particles) is modeled for 100 million years in the future. It is shown that the population of Damocloids retains high orbital inclinations during the integration time of 100 million years. By their dynamic life time, Damocloids can be divided into two subpopulations, with a short and long time of life. The first includes 85.75% of the objects and has an average life span of 2.68 + -0.04 million years. The subsistence population with a long life span is 14.25%, with an average lifetime of 126 + -6 million years. It is shown that these subpopulations are not segregated according to the plots i (e), i (a), i (Q). But they can be seen in the plots e (a), q (a), q (Q), i (q), q (e). We found 5 interesting objects that have a long time of life, but on the plots they occupy positions among objects with a short life span. More than a half of objects transfered from prograde motion to retrograde or vice versa during the time of integration and were traced with shorter step of integration. Taking into account the bimodal distribution of Damocloids in a dynamic life span, it is proposed to clarify the definition of Damocloids.
Properties of the Ultraluminous X-ray Source Populations in Chandra Source Catalog 2.0
Kovlakas, Konstantinos
The nature and evolution of ultraluminous X-ray sources (ULXs) is an open problem in astrophysics. They challenge our current understanding of stellar compact objects and accretion physics. Recent discoveries of ULX pulsars and reports of ULXs serving as sources of heating of the universe during the epoch of reionization, further demonstrate the importance of this intriguing and rare class of objects.In order to overcome the difficulties of directly studying the optical associations of ULXs, we generally resort in statistical studies of the stellar properties of their host galaxies.We present the largest scale such study based on the combination of Chandra archival data with the most complete galaxy catalogue of the local universe (D < 100 Mpc).This analysis incorporates robust distances and stellar population parameters (star formation rate, stellar mass, metallicity) based on associated multi-wavelength information. We explore the association of ULXs with galaxies in the (SFR, stellar mass, metallicity) space and we compare our results with predictions from X-ray binary population synthesis models.In addition, we discuss the effects of source confusion in large-volume studies of individual sources, and we present a statistical model to account for their clustering based on spatially resolved star-formation histories.
Schwarzschild model of the Fornax dSph
Kowalczyk, Klaudia
The Fornax dwarf spheroidal galaxy is one of the best studied satellites of the Milky Way. Thanks to its proximity, a convenient position on the sky and high luminosity, large data samples for its resolved population of stars, both photometric and spectroscopic, are available. I will present the outcome of modelling Fornax with the spherically symmetric orbit superposition method, including the derived mass and velocity anisotropy profiles. I will compare our results with those given in the literature and obtained with both full data modelling (applying Jeans or Schwarzschild methods) and simple mass estimators. I will also discuss a possible bias caused by the non-spherical shape of the galaxy and its implications for the final interpretation of the results.
Star Formation Activity and Molecular Gas in Nearby Galaxies across Environments
Koyama, Shuhei
The fraction of passive early-type galaxies increases with local galaxy number density, while that of young, star-forming late-type galaxies decreases. These strong correlations between galaxy properties and environment suggest that there exist some mechanisms which accelerate galaxy growth and/or efficient quenching of star formation in high-density environments, so called environmental effect. However, the physical mechanisms responsible for the environmental effect are still unclear, and identifying the key mechanism is one of the most important goals of the modern extra-galactic astronomy.To reveal these mechanisms, we present the molecular gas mass fraction (f(H2) = M(H2)/M*) and star formation efficiency (SFE = SFR/M(H2)) of local galaxies on the basis of our new CO(J=1-0) observations with the Nobeyama 45m radio telescope, combined with the COLDGASS catalog, as a function of galaxy environment. As a result, we revealed that both f(H2) and SFE have strong positive correlations with the SFR offset from the star-forming main sequence (?MS), and most importantly, we find that these correlations are universal across all environments.Our results demonstrate that the average f(H2) and SFE are determined by the average ?MS of the sample, regardless their surrounding environment. Since the average ?MS strongly depends on environment, it is not surprising to see the environmental dependence of average f(H2) and SFE if the samples are selected randomly without considering their ?MS distribution. In other words, our results suggest that f(H2) and SFE do not depend on environment at fixed ?MS. Based on our observational results, we conclude that the star formation process occurring within individual galaxies is not strongly affected by their global environment, but primarily controlled by their molecular gas content. In other words, our results suggest that the role of environment is to reduce the gas reservoir in galaxies.
Magnetic fields and CR propagation in the halo of spiral galaxies as deduced from the CHANG-ES survey
Krause, Marita
With CHANG-ES, a survey of 35 edge-on galaxies in radio continuum and polarization with the EVLA in C- and L-band, we now better understand the halos of spiral galaxies and their magnetic fields. In the halo we observed again in strong X-shaped (and vertical) magnetic fields in several galaxies. However, it was unknown whether these fields are regular (coherent) or anisotropic (e.g. elongated loops). We now detected for the first time a large-scale Faraday depth pattern with different signs, indicating the existence of regular (coherent) magnetic fields in the halo of spiral galaxies. The results for the well-known galaxy NGC 4631 are presented and discussed in more detail.Further, we determined and analyzed the radio scale heights in a CHANG-ES subsample of 13 galaxies in a coherent way. The results are:Galaxies with smaller scale lengths are more spherical in the radio emission, while those with larger scale lengths are flatter.The radio scale height depends mainly on the radio diameter of the galaxy.The sample galaxies are consistent with an escape-dominated radio halo with convective cosmic ray propagation, indicating that galactic winds are a widespread phenomenon in spiral galaxies.While a higher star formation rate or star formation surface density does not lead to a higher wind velocity, we found for the first time observational indication of a gravitational deceleration of CRE outflow, i.e. a lowering of the wind velocity from the galactic disk.
Tomography of the red supergiant star mu Cep
Kravchenko, Kateryna
We present a tomographic method allowing to recover the velocity field at different optical depths in a stellar atmosphere. It is based on the computation of the contribution function to identify the depth of formation of spectral lines in order to construct numerical masks probing different optical depths. These masks are cross-correlated with observed spectra to extract information about the average shape of lines forming at a given optical depth and to derive the velocity field projected on the line of sight. We applied this method to series of spectra of the red supergiant star μ Cep and derived velocities in different atmospheric layers. The resulting velocity variations reveal complex atmospheric dynamics and indicate that convective cells are present in the atmosphere of the μ Cep. The μ Cep velocities were compared with those obtained by applying the tomographic masks to series of snapshot spectra from 3D radiative-hydrodynamics CO5BOLD simulations.
Resolving the origin of the hydrogen line emission in YSOs with near-infrared interferometry
Kreplin, Alexander
Jets and out?ows play a fundamental role in star formation and the physics of the accretion-ejection process. While the hot circumstellar dust can be studied in the near-infrared continuum, hot ionised gas can be studied in lines, in particular, the Br? line. The unprecedented milliarcsecond resolution achievable with the Very Large Telescope Interferometer (VLTI) allows us to study the origin of the line emission and kinematics of the physical processes involved in the creation of these lines, e.g., magnetospheric accretion or disk wind. In this talk, we show the application of various modelling techniques ranging from geometric models to state-of-the art disk wind radiative transfer codes on Herbig Ae/Be stars observed with the VLTI/AMBER and GRAVITY instruments. In the high mass protobinary system IRAS17216-3801 we demonstrate how spectro-interferometric observations of the Br? and CO lines can be used to estimate the fractional contribution to the line emission of hot (10^4 K) and warm (10^3 K) gas of each star within a young binary system. Near-Infrared interferometric observations of the Herbig Ae/Be star MWC120 reveal that the source of Br? emission in this system seems to be dominated by a disk wind rather than, e.g., by magnetospheric accretion. Our study on the Herbig B[e] star MWC 297 combines VLTI/AMBER high-spectral dispersion interferometry (R=12,000) and CRIRES spectro-astrometry (R=100,000). Using aperture synthesis imaging techniques, we reconstruct velocity-resolved channel maps and moment maps that reveal the motion of the Br?-emitting gas in six velocity channels, marking the first time that kinematic effects in the sub-AU inner regions of a protoplanetary disk could be directly imaged. We model all observables using a kinematic model that includes a Keplerian-rotating velocity component as well as outflowing velocity component, as inspired by a magneto-centrifugal disk-wind scenario.
An automated testbed for the precision characterization of intra-pixel sensitivity for TESS CCD detectors
Krishnamurthy, Akshata
Transiting Exoplanet Survey Satellite (TESS) is an Astrophysics Explorer Mission selected by NASA for launch in April 2018. The objective of the mission is to discover small planets around bright dwarf stars by detecting temporary periodic dips in brightness caused due to occultation. The instrument consists of four identical wide-field optical CCD cameras with seven optical elements. One of the lens elements has a long-pass filter coating to enforce the band-pass cutoff at 600 nm. The 2x2 array of CCDs is contained within a 62x62 mm area with 15x15 micron pixels. The CCD detectors are optimized to have enhanced sensitivity over the redder wavelengths up to 1050 nm. Systematic noise of 60 ppm or less on hourly timescales is required to enable high precision photometry. Very precise on-ground characterization and calibration of TESS CCD detectors is necessary to achieve this photometric limit. One of the most significant sources of noise is intra-pixel or sub-pixel sensitivity that can lead to increased systematic error in the presence of pointing instability. An automated optical test bench with very high photometric stability has been developed to study the intra-pixel response variations in the back-illuminated deep depletion CCD detectors. The results from the measurements will significantly assist in understanding the impact of sub-pixel variations on the photometric performance and science yield of the mission. The paper describes the facility design, key features, calibration, error analysis and test results from this effort.
Doppler images of V1358 Ori
Kriskovics, Levente
We present Doppler images of the active dwarf V1358 Ori. The maps are derived with our new Doppler imaging code iMap applied on TBL-NARVAL data, covering two consecutive rotations. The maps show polar spottedness, as well as cooler features on lower latitudes. Solar-type surface differential rotational pattern is also detected by cross-correlating the consecutive maps.
Protostellar Interferometric Line Survey of the Cygnus-X region: PILS-Cygnus
Kristensen, Lars
Most stars, including our own Sun, form in dense stellar clusters with hundreds or thousands of other stars. These clusters show an incredibly rich chemistry, particularly near the forming young stars, where planets eventually form. Understanding the origin of this chemistry is important to study the process of star formation and determine the complexity of chemistry that can develop, particularly in terms of prebiotic molecules. To achieve these goals, star-forming regions are being surveyed both in terms of number and type of objects, and in terms of frequency coverage. The larger the source sample, and the greater the frequency coverage, the stronger the final conclusions regarding the formation of complex organic and prebiotic molecules are. Achieving both at the same (number of sources and frequency coverage) is traditionally expensive, but the SMA with its upgraded receivers and SWARM correlator is now overcoming this technological barrier, making it cheap to cover large frequency windows in one go. We have exploited these capabilities and will here present the initial results of the Protostellar Interferometric Line Survey of the Cygnus X star-forming region (PILS-Cygnus). The survey is done by observing the frequency range from 329-363 GHz with the SMA at an angular resolution of 1" (~1500 AU).
Double maximum of solar cycle
Krivodubskij, Valery
We propose a new scenario to explain the observed phenomenon of the double maximum of the sunspot cycle. This scenario includes the generation of the magnetic field near the bottom of the solar convection zone (SCZ) and its subsequent removal from the deep layers to the surface in the “royal zone". We take into account the five processes of magnetic field reconstructing during solar cycle: omega-effect, meridional circulation, magnetic buoyancy, macroscopic radial turbulent diamagnetism and magnetic pumping due to matter density radial inhomogeneity (the MPDI-effect). It was found that there are different conditions for the reconstruction of magnetism in the near-polar and the near-equatorial domains of the SCZ. The radial differential rotation generates a strong toroidal field near tachocline by affecting the poloidal field of the previous cycle. In the near-equatorial domain, magnetic buoyancy, turbulent diamagnetism, and the MPDI-effect act together to transport this deep strong toroidal field to the solar surface, where its fragments can be observed after a while as bipolar sunspot groups at the middle latitudes of the “royal zone”. This upward directed first wave of toroidal field is responsible for the main maximum of sunspot activity. At the same time the toroidal fields in the high-latitude polar domains are blocked at the beginning of the cycle near the SCZ bottom by two “negative buoyancy” effects: the downward turbulent diamagnetic transfer and the downward magnetic pumping due to matter density inhomogeneity. After only 1–2 years the deep equatorward meridional flow will push these magnetic fields into low-latitude areas of the near-equatorial domain. Due to directed upward magnetic pumping caused by the MPDI-effect these belated magnetic fields rise to the surface. These second waves of belated toroidal fields come to the surface at somewhat lower latitudes of the “royal zone” and produce the repeated maximum of sunspot activity.
Anthropic Principle and the Hubble Constant
Krizek, Michal
The so-called weak formulation of the Anthropic Principle states that all fundamental physical constants have just such values that they enabled the origin of life. We show that also the Hubble constant significantly contributed to the existence of mankind [1]. Life on Earth has existed continually for at least 3.5 Gyr and this requires relatively stable conditions during this very long time period. However, since the luminosity of the Sun increases, the Earth should recede from the Sun. We present several examples indicating that the Solar System expands by a speed comparable to the Hubble constant. This guarantees that the Earth received almost constant solar flux during the last 3.5 Gyr. We give three independent arguments showing that the average Earth-Sun distance increases about 5 m/yr due to the finite speed of gravitational interaction. Such a large recession speed cannot be explained by solar wind, tidal forces, plasma outbursts from the Sun, or by the decrease of the Solar mass due to nuclear reactions. Models based on Newtonian mechanics can explain only a few cm per year. The measured average increase in the Earth-Moon distance is 3.84 cm/yr, while Newtonian mechanics is able to explain only 2.1 cm/yr. We claim that this difference is also caused by the finite speed of gravitational interaction and its size is comparable with the Hubble constant. Mars was much closer to the Sun as well, otherwise it could not have had rivers 3.5 Gyr ago, when the Sun’s luminosity was only 75 % of its present value [2].References[1] M. Krížek, Dark energy and the anthropic principle, New Astronomy 17 (2012), 1–7.[2] M. Krížek, L. Somer, Manifestations of dark energy in the Solar system, Grav. Cosmol. 21 (2015), 58–71.
Hot star wind mass-loss rate predictions at low metallicity
Krticka, Jirí
Hot star winds are driven by the radiative force due to the light absorption in the lines of heavier elements. Therefore, the amount of mass lost by the star per unit of time, i.e., the mass-loss rate, is sensitive to the metallicity. Consequently, the hot star feedback mediated by the winds also depends on metallicity. We provide mass-loss rate predictions for O stars with low mass fraction of heavier elements Z < Zsun. Our predictions are based on global (unified, hydrodynamic) model atmospheres. The models allow us to predict wind terminal velocity and the mass-loss rate just from basic global stellar parameters. We provide a formula that fits the mass-loss rate predicted by our models as a function of stellar luminosity and metallicity. On average, the mass-loss rate scales with metallicity as Z^0.59. The predicted mass-loss rates agree with mass-loss rates derived from ultraviolet wind line profiles. We show that the rotational mixing affects the wind mass-loss rates at low metallicity. We study the influence of magnetic line blanketing, which might be important for binary black hole progenitors. Our models provide consistent mass-loss rate determinations, which can be used for quantitative study of stars at low metallicity.
PHOTOMETRIC SURVEY OF NEAR-EARTH ASTEROIDS IN THE FRAME OF ISON NETWORK
Krugly, Yurij
The main goals of our survey are regular photometric observations of near-Earth asteroids (NEAs) in order to investigate:(1) newly discovered and/or closely approaching the Earth NEAs, with impact on potentially hazardous asteroids;(2) rotation properties of NEAs, which are expected to show an evidence of the YORP effect influence;(3) well-known binary NEAs for the BYORP effect determination as well as to search for new binaries;(4) very fast rotation of small NEAs with diameters smaller 200-300 m;(5) physical properties of NEAs which are radar targets.The survey is based on facilities of International Scientific Optical Network (ISON). The Network includes more than 100 telescopes with the apertures from 20 cm up to 2.6 m located at 43 observatories in 17 countries. Ten largest telescopes are used for regular photometric observations of asteroids.We present the results of our observations of 70 NEAs carried out during more than 250 nights in 2017. Among them, we observed 18 newly discovered NEAs and the known binaries (66391) 1999 KW4 and (137170) 1999 HF1 to study the BYORP effect. The rotation peroids were determined or improved for more than 20 asteroids. We obtained the lightcurves of many asteroids suitable to investigate an influence of the YORP effect. Several NEAs were found as suspected to be a binary. We also discuss future development of the ISON network for photometry of asteroids.
Problems with exoplanets around sdBV snd sdO stars from primary Kepler field
Krzesinski, Jerzy
The existence of exoplanets around evolved objects is one of the most interesting subjects from the viewpoint of planetary systems evolution and their fate. What happens to the exoplanets engulfed in the host star envelope during red giant branch (RGB) phase? What is the fate of planets when the host star enters the asymptotic giant branch (AGB) evolution? Do planet form from the debris of the AGB remnant material or are there any survivors from the original planetary system? These and other questions are crucial for our understanding of the late planetary system evolution. We do observe planets around giant stars, however, since the discovery of exoplanets around pulsars (Wolszczan and Frail 1992), there are still continuous searches going for exoplanets around white dwarfs and intermediate stage stars – subdwarfs. The last one seems to be successful in terms of finding candidates for giant and earth type planets around extreme horizontal branch stars, but is this a confirmed link for planetary existence between RGB/AGB and white dwarf phase of the stars? Here we are showing that at least some of the exoplanetary signatures found in the light curves of a couple of sdBV star systems (KIC 5807616 and KIC 10001893) might be of different source than exoplanet light reflection or radiation effects. We point out that at least one signature can be explained by linear combination of pulsating frequencies of the host star and others might be just artifacts. Using simulated light curves we also analyzed frequency changes of the signal around 0.256 c/d (~3.9 day) visible in the Fourier transform of the KIC 10449976 sdO star light curve. Our simulations show that it is difficult to reproduce the observed signal frequency variations by the weather changes in the exoplanet atmosphere.
Exploring the 3D properites behind dust polarization maps of star forming filaments
Küffmeier, Michael
To trigger a hot debate among astronomers, it is often enough to ask about the importance of magnetic fields. In the field of star formation, this is mainly because of ambiguities both in models with and observations of magnetic fields. In models, on the one hand magnetic fields help in transporting angular momentum, on the other hand if they are too strong they suppress the formation of disks altogether. To constrain the orientation of magnetic fields, polarization of dust grains have been considered as a useful tracer. However, polarization of dust is not only affected by magnetic fields, and therefore it is a very sensitive tracer. Our aim is to demonstrate the different polarization features in different regions of molecular clouds by producing synthetic observations with the radiative transfer code polaris. Based on magnetohydrodynamical simulations with the adaptive mesh refinement code ramses of a molecular cloud region of (4 pc)^3 in volume, we produce synthetic dust polarization maps. The MHD simulations successfully reproduce the IMF and apply a maximum resolution of 50 AU in the vicinity of the stars. The stars -- modeled as sink particles in the original MHD simulations – are used as sources of radiation by adopting stellar properties obtained with the stellar evolution code MESA at given snapshots. Besides showing the dependencies of the polarization signal on the underlying physical properties, we also discuss issues when considering the ratio of polarization signal and surface density against the background of the three dimensional nature in Giant Molecular Cloud.
A Multi-Phase Gas Description and its Implications for Numerical Models of Dwarf Galaxies
Kühtreiber, Matthias
We present results from our N-body/SPH code “cd-sph” including a modern state-of-the-art SPH algorithm and a multi-phase description of the interstellar medium (ISM). This approach aims at overcoming various issues of a single gas phase used in most hydrodynamical simulations. The ISM is modelled more realistically by adding a cold cloudy medium to the hot/warm gas represented by SPH particles. These clouds are treated with the sticky-particle method and allow for coagulation and fragmentation of molecular clouds. The formation of stars is realized by directly applying the Jeans criterion to the clouds. Stars, which are treated as collisionless N-body particles, and the gas phases are mutually coupled by mass, momentum, and energy exchange in a self-consistent manner.Different feedback processes from stars are taken into account distributing energy, mass and newly produced chemical elements to the cold clouds or to the hot/warm medium. Depending on the stellar mass, UV radiation, stellar winds supernovae type II, type Ia and planetary nebulae, are considered. The different gas phases are not decoupled from each other, as they can exchange mass, including chemical elements and energy through thermal conduction, leading to condensation or evaporation. Due to their different dynamical properties, additional drag forces are included which lead to momentum exchange between clouds and the gaseous medium.We apply our model to isolated dwarf galaxies in order to investigate their chemo-dynamical evolution and make comparisons with observations and with single-phase simulations. Thereby, we demonstrate the differences of the dynamics and chemical evolution due to the multi phase ISM and the stellar feedback processes which affect the clouds and the hot/warm medium in a decoupled manner. We further discuss mass loading as an important process for the chemo-dynamical evolution in dwarf galaxies and implications for simulations of ram pressure stripping and galaxy harassment.
First Hydrodynamics Simulations of Radiation Forces and Photoionization Feedback in Massive Star Formation
Kuiper, Rolf
We present the first simulations of the formation of massive stars which account for radiation forces as well as photoionization feedback (along with protostellar outflows) simultaneously. We perform direct hydrodynamics simulations of the gravitational collapse of high-density mass reservoirs toward the formation of massive stars including self-gravity, stellar evolution, protostellar outflows, continuum radiation transport, photoionization, and the potential impact of ram pressure from large-scale gravitational infall. For direct comparison, we execute these simulations with and without the individual feedback components. Furthermore, each simulation series is performed starting from two different accretion scenarios, namely a finite small-scale mass reservoir such as a pre-stellar core vs. a virtually infinite reservoir which accounts for large-scale accretion flows. We determine the relative strength of the feedback components and derive the size of the reservoir from which the forming stars gained their masses. _x005F Photoionization and HII regions dominate the feedback ladder only at later times, after the star has already contracted down to the zero-age main sequence, and only on large scales. Specifically, photoionization yields a broadening of the bipolar outflow cavities and a reduction of the gravitational infall momentum by about 50%, but does not limit the stellar mass accretion. On the other hand, we find radiation forces restrain the gravitational infall toward the circumstellar disk, impact the gravito-centrifugal equilibrium at the outer edge of the disk, and eventually shut down stellar accretion completely. _x005F The most massive star formed in the simulations accreted 95 Msol before disk destruction; this mass was drawn-in from an accretion reservoir of approximately 240 Msol and 0.24 pc in radius. Concluding, in the regime of very massive stars, the final mass of these stars is controlled by their own radiation force feedback.
Star formation efficiency in self-gravitating molecular cloud deviating from thermodynamic equilibrium
Kumssa, Gemechu
Abstract In this paper we present star formation efficiency in free-fall time (SFE_{ff}) of self-gravitating molecular cloud which is deviating from thermodynamic equilibrium by a factor e where (0 < e < 1). Understanding efficiency of star formation in molecular cloud (MC) leads to know how, where and when of star formation in time. In this work we see the influence of different parameters in triggering and controlling star formation efficiency in self-gravitating molecular cloud deviating from thermodynamic equilibrium. Based on the conceptual framework we have modeled equation of star formation efficiency (SFE_{ff}) in free fall-time for star forming MC under its own gravity and deviating from thermodynamic equilibrium. Its efficiency is relatively larger than that of star forming MC in thermod ynamic equilibrium. Fundamental parameters also varied in time and obtained that star formation efficiency of self-gravitating MC is affected by fundamental parameters present in modeled equation.Keywords MC: self-gravitating MC; Star : Star Formation; thermodynamic equilibrium.
Realistic 3D simulations of solar and stellar surface convection covering several days
Kupka, Friedrich
We present results from 3D radiation hydrodynamical simulations forthe Sun and a few other Sun-like stars. These are performed over relatively long time scales of several days to study p-mode excitation and damping processes. While the focus of our study is on helio- and asteroseismology, the same simulation data can also be used to investigate the stability of solar and stellar irradiance over these time scales. To this end, we show results from a first analysis of our simulation data.
Modeling of hydrodynamic processes within high-mass X-ray binaries
Kurfürst, Petr
High-mass X-ray binaries belong to the brightest objects in the X-ray sky. The massive X-ray binariesmay be schematically sub-divided into supergiant X-ray binaries and Be/X-ray binaries. The firstsubclass usually consists of massive O or B star, or a blue supergiant while the compact, X-rayemitting, component is a neutron star or black hole. The Be/X-ray binaries consist of a Be star andmostly a neutron star. Intensive matter accretion from luminous optical donor star onto the compactobject takes various forms: spherically symmetric accretion, Roche-lobe overflow, or circumstellardisk. It produces an intensive X-ray source that may more or less dramatically vary in brightness ontimescales ranging from miliseconds to years. In our multi-dimensional models we perform numericalsimulations of an accretion of a circumstellar disk matter onto a compact companion in case of Be/X-ray binaries. Using the Bondi-Hoyle-Littleton approximation, we estimate the neutron star accretionrate and the X-ray luminosity of a system, we can determine the Be/X-ray binary disk hydrodynamicstructure and compare its deviation from the isolated Be stars’ disk. From the rate and morphologyof the accretion flow and the X-ray luminosity we improve the estimate of the disk mass-loss rate.We also study the behavior of high-mass X-ray binary system under a supernova explosion event,assuming a blue supergiant progenitor with an aspherical circumstellar environment.
Long-term study of TeV blazars
Kurtanidze, Omar
About fifty (Mrk 421, Mrk 501, 1ES 1959+650 and others) northern TeV extragalactic sources have been discovered during last twenty five years. Most of them (2/3) we are monitoring in Abastumani Observatory during 20 years using 125-cm and dedicated 70-cm meniscus telescopes. All observations (over 3100 nights) have been conducted with Apogee Ap6E and SBIG ST-6 CCD cameras in BVRI bands. The frames have been reduced using Daophot II and homogenous lightcurves have been constructed. The amplitudes of long-term variability are within 0.3-1.5 magnitudes. Few sources show Intra-day variability within 0.05-0.15 magnitudes, while intra-night/micro-variability is below 0.05 magnitudes. The extensive multi-wavelength campaigns with Whipple, VERITAS, HESS and MAGIC have also been conducted.
Use of Medium Size Telescopes and CCD Cameras to study blazars
Kurtanidze, Omar
The first report on micro-variability in AGNs was announced in the beginning of 60-ies, when a few sources were studied with a single-channel photoelectric photometer and biggest Palomar telescopes. Nevertheless, these variations were received with skepticism due to the instrumental instabilities and the inherent non repeatability of time-critical observations. Availability and utilization of CCD cameras breathed new life to small telescopes. During last decades, the variability time-scales from minutes to years have been studied for many blazars using commercial CCD cameras and small telescopes. A short review of blazar monitoring programs conducted during last 20 years in Abastumani Observatory and future prospects will be presented.
Stellar and dark halo properties of LAEs: the efficiency of star formation and the origin of diffuse Lya halos
Kusakabe, Haruka
Lya emitters are a representative dwarf galaxy population at high z characterized by strong Lya emission. However, the stellar mass (Ms), SFR, and dark halo mass (Mh) of LAEs have not been estimated with a high enough accuracy to place them in the framework of structure formation. Moreover, the origin of diffuse Lya halos (LAHs) has not been identified in spite of the fact that the Lya luminosity of LAHs is comparable to or even higher than that of the main body of LAEs. To address these issues, we study the stellar and dark halo properties of LAEs using a large sample of z~2 LAEs for which LAH luminosities are available by stacking analysis. We find that while these LAEs are consistent with SFMS galaxies, they have relatively high Ms/Mh and SFR/BAR ratios, implying that LAEs have been converting baryons into stars efficiently in spite of their low Mh. We also find a nearly constant LAH luminosity with Ms and Mh. This suggests that LAHs are caused by scattering of Lya photons in the CGM, not by in situ gas cooling or star formation in satellite galaxies, because the latter two origins predict a roughly linear scaling of LAH luminosity with these masses. When the LAH component is included, LAEs have very high Lya escape fractions reaching ~30-100%, being one dex higher than those of HAEs with the same Ms and E(B-V). Such high escape fractions may be partly due to relatively low gas masses implied from high Ms/Mh ratios, i.e., high efficiencies of star formation, although another Lya source may also be needed in the main body of LAEs.
Outreach activities of Astrobiology Center of Japan
Kusakabe, Nobuhiko
As a result of developments in extrasolar planet observations, astrobiology research to explore “Life in the Universe” and uncover its mysteryes has become a pressing subject. Astrobiology Center (ABC) of Japan, established in 2015, advances this field by combining disciplines, promotes research into extrasolar planets and life both outside and within the Solar System, and develops observational instruments for these purposes.For public, “Life in the Universe” is one of the most attractive topic. Many science fiction movies show various shapes aliens. However, real astrobiology researches are quite far from such aliens shape and most public people do not know such actual astrobiology research. Therefore, ABC needs to tell actual astrobiology research field.At first, we have opened the astrobiology center official website since 2015 (http://abc-nins.jp). In the website, thirteen topics related astrobiology and exoplanet researches have been released until now. We organized and participated various outreach programs such as visiting lectures, public talk, symposiums and open campus based on some Astrobiology researches. For example, one of a new topic is photosynthesis on a habitable exoplanets. Plants on exoplanets are quite attractive topic. From biology side, we talked about photosynthesis system such as reaction wavelength and efficiency under another Sun’s spectrum. From astronomy side, we talked about various exoplanets, habitable zone, their assumed environment and climate. We talked about both of these topics on some events.On the other hand, for children, we held exoplanet and alien drawing events. In such events, we explain some exoplanet parameters such as size, gravity and temperature. Then children drew freely their own planets and aliens based on scientific exoplanet environment. I summarize ABC public outreach activities. Our activities would be effective for people who are interested in not only astronomy but also biology.
Calibration and Standardization Issues in UV-VIS-IR Astronomy
Küsters, Daniel
SCALA is a physical calibration device for the SuperNova Integral Field Spectrograph (SNIFS) and is permanently mounted to the University Hawaii 2.2m telescope. The aim of SCALA is to perform a fundamental calibration of the CALSPEC1 standard stars, which are currently calibrated relative to white dwarf model atmospheres. SCALA transfers the calibration of a ux calibrated photodiode to SNIFS. As the photodiode is sensitive over a broad wavelength range, a monochromator lamp setup is used to perform the transfer wavelength by wavelength. This calibration of SNIFS relative to a laboratory ux-calibrated broad-band detector can be compared with the usual SNIFS calibration relative to the CALSPEC standard stars, and consequently ties the laboratory detector standard with the models for the white dwarf atmospheres We here report several identi ed and characterized internal systematics (reections2) which we correct our measurements for, most prominently internal reections and out-of-band emission from our monochromator. We compare our results to the existing CALSPEC system (model atmospheres) and to a compilation of Vega ux calibrations using laboratory-calibrated light sources (measurements, Hayes 19853). Our measurements agree to the CALSPEC and Hayes 1985 results within 2% in a wavelength range from 4500A to 9000A. We plan to introduce baes to our light source and detector to suppress internal reections. We further plan to use a double monochromator to suppress the out-of-band emission. Both improvements should lead to sub-percent uncertainties in the calibration of the standard stars and an increased wavelength range, down to 3500A.
Keywords: Cosmology, SNe Ia, Calibration, Spectrophotometry, Integral eld spectroscopy
The New Variability Phase of OJ 287 and Emergence of New Components in NIR to X-ray Region
Kushwaha, Pankaj
We present a multi-wavelength (MW) spectral and temporal study of the recent activity of the claimed super-massive binary black system OJ 287 since December 2015. The overall MW activity can be divided into two durations: December 2015 – May 2016, showing strong activity from near-infrared (NIR) to gamma-rays and April 2016 – July 2017, showing intense NIR to X-ray variability concurrent with detection at very high energies (VHE) by VERITAS, but without any signatures of variability in the Fermi-LAT band. In the first duration, the variations are almost simultaneous and the SEDs show new components in NIR-optical and optical-UV region. The NIR-optical bump is consistent with standard accretion disk description while the optical-UV appears consistent with contributions from the broad-line region. The extracted broadband SEDs also show a clear shift in gamma-ray SED peak and can be explained with inverse Compton scattering of photons from the optical-UV bump. In the second period, the variations are also simultaneous except for one duration during which X-ray leads the optical/UV by ~ 5-6 day. The broadband SEDs, on the other hand, show mixture of a typical OJ 287 SED and an HBL SED, consistent with an origin from two different zones, one located at sub-parsec scales and other at parsec scales.
On the Role of Magnetic Fields in Cloud Dynamics in Serpens South/Aquila Rift
Kusune, Takayoshi
We made NIR polarimetric observations toward 1x0.5 square degree area of Serpens South/Aquila Rift (e.g., Sugitani et al. 2011). We also conducted mapping observations in 12CO/13CO/C18O/N2H+ with the Nobeyama 45-m telescope and found that this region contains several filaments with different velocities, which are roughly parallel to each other. Using the Histogram of Relative Orientations (Soler et al. 2015), the filaments are found to be roughly perpendicular to the magnetic field. Applying the Davis-Chandrasekhar-Fermi method, the plane-of-sky magnetic field strength is estimated to be 30-100 µG. The morphology of the field and molecular gas suggests that the magnetic field plays an important role in the filament evolution. We also found that the global field is somewhat curved in the southern part, suggesting that the expanding shell by the nearby HII region, W40, dynamically affects the filaments. The C18O velocity structure along the filament also indicates the dynamical interaction with W40 (Shimoikura et al. 2018 in prep.). The dense filaments are magnetically supercritical as a whole, and thus the magnetic field is not so strong to fully support the filaments against gravitational contraction. As a result, the gravitational fragmentation appears to promote the formation of dense cores where protostars form. This is consistent with the fact that the active cluster formation, which we call Serpens South cluster, is ongoing in the southern part of the densest filament (e.g., Könyves et al. 2015). We propose that the global motion of the filaments is regulated by the magnetic field and the collision of the filaments along the global magnetic field triggered the protocluster formation in Serpens South (Nakamura et al. 2014). Furthermore, we will report the results of the CCS Zeeman measurement toward the Serpens South cluster using Z45 on the Nobeyama 45-m telescope (Mizuno et al. 2015; Nakamura et al. 2015) to constrain the 3D magnetic structure in this region.
Dust reddening and diffuse ultraviolet observations near Taurus
kuzhikkatt, sathyanarayanan
We have studied the dust-distribution in Taurus molecular region with different reddening maps and analyzed the GALEX diffuse ultraviolet data to estimate the dust grain properties in the region with a Monte Carlo dust-scattering code. We find that the dust-distribution has little effects on the grain properties.
2015-2016 NuSTAR monitoring of the non-thermal emission around the Arches cluster
Kuznetsova, Ekaterina
Recent NuSTAR and XMM–Newton observations of the molecular cloud around the Archescluster demonstrate a dramatic change both in morphology and intensity of the non-thermalemission, similar to that observed in the Central Molecular Zone (CMZ) of the Galactic Center(GC). Strong variations of the molecular clouds support the X-ray reflection mechanism offluorescence observed in CMZ and reveal propagation of illuminating fronts, presumablyinduced by the past flaring activity of Sgr A*. We continue monitoring campaign of the Archescluster with NuSTAR and will present results based on the recent observations, revealing thecurrent intensity level of the non-thermal emission from the molecular cloud.
Contribution of satellite techniques to CRS realization
Kwak, Younghee
Conventionally, the International Celestial Reference System (ICRS) is realized solely by the Very Long Baseline Interferometry (VLBI). On the other hand, the International Terrestrial Reference System (ITRS) is realized by the four space geodetic techniques: VLBI, Global Navigation Satellite System (GNSS), Satellite Laser Ranging (SLR), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). The VLBI-derived Terrestrial Reference Frame (TRF) is not consistent with the inter-technique combined TRF due to different data sets, its network geometry, and the impact of local ties at co-location sites. The same holds for the EOP series which provide the link between the Celestial Reference Frame (CRF) and TRF. Apart from consistency issues, the VLBI-derived EOP (especially terrestrial x/y-pole coordinates) have less precise time series than those derived from GNSS observations since GNSS is the dominant technique in determining terrestrial x/y-pole coordinates among the space geodetic techniques. In the combination, the precise GNSS EOP series can beneficially stabilize the VLBI-derived EOP and consequently indirectly the CRF.In this contribution, we estimate CRF, TRF, and EOP simultaneously based on the VLBI input data for ICRF3 (1979-2017), and the GNSS input data for ITRF2014 (1994-2014) extended for the period 2015-2017. We present the possible correlation between CRF parameters (right ascension and declination) and EOP. The influence of various combination strategies on different types of radio sources is also studied.
Chemical enrichment of galaxies as the result of organic synthesis in evolved stars
Kwok, Sun
Infrared spectroscopic observations have shown that complex organics with mixed aromatic-aliphatic structures are synthesized in large quantities during the late stages of stellar evolution. These organics are ejected into the interstellar medium and spread across the galaxy. Due to the sturdy structures of these organic particles, they can survive through long journeys across the galaxy under strong UV background and shock conditions. The implications that stellar organics were embedded in the primordial solar nebula will be discussed.
Magnetic Braking of Circumstellar Disks may not be so Catastrophic
Kwon, Woojin
Magnetic fields affect star formation over a broad range of scales from ~1 pc to ~100 au. In particular, interferometric observations and ideal magneto-hydrodynamic (MHD) simulations have reported that formation of a rotation-supported disk around the earliest young stellar objects (YSOs) is largely suppressed by magnetic fields aligned with the rotational axis of the YSOs, which is known as the magnetic braking catastrophe. We present ALMA observations toward the protostar L1448 IRS 2, where rotation is detected and magnetic fields are aligned with the rotation axis (poloidal fields) on ~500 au scales. Our data show that on ~100 au scales, the field morphology changes to toroidal, which implies strong evidence for a circumstellar disk. On the other hand, the magnetic field strength, as estimated by the Davis-Chandrasekhar-Fermi method, is strong enough to hinder the formation of a rotationally supported disk, which is inconsistent with the central toroidal field. This result suggests that magnetic braking may not be so catastrophic for early disk formation, even in YSOs with magnetic fields aligned to the rotational axis and that non-ideal MHD effects should be considered for understanding early disk formation around YSOs.
MIRI GTO spectroscopy of high-z galaxies
Labiano, Alvaro
MIRI, with the spectral coverage from 5 to 28 um and its sensitivity, is the JWST instrument best suited to explore the rest-frame optical/near-infrared spectrum for galaxies at High-z, and the only one that can detect the Halpha emission line on sources at redshifts beyond 6.7. The European MIRI Guaranteed Time Observations (GTO, PI: G. Wright) will dedicate 65 hours with the Medium-resolution integral field spectrograph (MRS) and the IMAGER to individually study three Lyman alpha emitters (LAEs), two quasars in the Epoch of Reionization (EoR), and two dusty star-forming galaxy (DSFG) at z~4-7.In this talk we discuss the main goals of the program : a) detect the Halpha emission line for three spectroscopically detected LAEs (COS-zs7-1, EGS-zs8-1 y EGSY8P7) from z~7 to 9. b) explore the optical/near-infrared continuum spectrum and emission lines for two QSOs (J1120+0641 and J2348-3054) at z~7. c) study the sub-arcsec view over the rest-frame near-infrared spectrum for two DSFG (GN-20 and HFLS3). d) perform Mid-IR imaging for all the galaxies and surrounding fields.In addition, we will show realistic MIRISim simulations of our future GTO observations and the first calibration tests with the JWST pipeline.
Chaotic capture and ejection of matter by binary systems
Lages, José
Binaries are everywhere: at the heart of many planetary systems (binary stars), at the center of galaxies (SMBH binaries), among small bodies (binary asteroïds), even the Solar System in a rough approximation can be viewed as the Sun+Jupiter couple. Here, we study the capture of a galactic flow of particles by binaries and even n-aries with a symplectic map description. This approach allows modeling the scattering of 1016 particles after following the time evolution of the captured particle on about 109 orbital periods of the binary system. It is shown that the capture cross-section is much larger than the area of the binary being inversely diverging at small particle energy. We show that the dynamics of captured particles is chaotic and is well described by a simple symplectic map. We obtain the particle density distribution inside such systems and determine in the vicinity of the binary the enhancement factor of their density compared to its galactic value as a function of the mass ratio of the bodies and the ratio of the body velocity to the velocity of the galactic particle wind. We find that the enhancement factor can be on the order of tens of thousands.References:J. Lages, D. Shepelyansky, I. Shevchenko, Kepler map, Scholarpedia, 13(2):33238 (2018)G. Rollin, J. Lages, D. L. Shepelyansky, Chaotic enhancement of dark matter density in binary systems, A&A 576, A40 (2015)J. Lages, D. L. Shepelyansky, Dark matter chaos in the Solar System, Monthly Notices of the Royal Astronomical Society : Letters 430, L25-L29 (2013)
Chaotic clearing of the vicinity of rotating small bodies
Lages, José
Asteroids, cometary nuclei, trans-Neptunian objects, planetary satellites, with diameter below 1000km, are usually irregular shape bodies which appear like contact binaries. We show that the rotation of such gravitating bodies creates in their vicinity a zone of chaotic orbits. We determine the chaotic zone extent analytically and numerically. The slower is the rotation rate of the small body, the wider is the chaotic zone. In particular, the chaotic zone swells more than twice if the rotation rate is decreased 10 times with respect to the contact binary “centrifugal breakup” threshold. We precisely determine the properties of the chaotic orbital zones and of the global orbital dynamics about the asteroids; 243 Ida (which has a moon, Dactyl, orbiting near the edge of the chaotic zone), and 25143 Itokawa; and about the cometary nuclei of 67P/Churyumov–Gerasimenko, 1P/Halley, 8P/Tuttle, 19P/Borrelly, and 103P/Hartley. In the case of Comet 1P/Halley, the circumnuclear chaotic zone seems to engulf an essential part of the Hill sphere, at least for orbits of moderate to high eccentricity.References:J. Lages, I. Shevchenko, G. Rollin, Chaotic dynamics around cometary nuclei, accepted in Icarus (https://doi.org/10.1016/j.icarus.2017.10.035)J. Lages, I. Shevchenko, D. Shepelyansky, Chaotic zones around rotating small bodies, The Astronomical Journal 153:272 (2017)L. Maltagliati, Research Highlights: Cloud of chaos, Nature Astronomy 1, 0168 (2017) (highlight of article [2])
Origin of Spin-Orbit Misalignments and Formation of Close-in Giant Planets
Lai, Dong
The origins of hot Jupiters (HJs, with periods < 10 days) and warm Jupiters (WJs, with periods 10-200 days) remain an outstanding problem in exoplanetary astrophysics. Possible formation channels range from high-eccentricity migration induced by planet-planet or planet-binary interactions to disk-driven migration or even in-situ formation. A significant fraction of these close-in giant planets have been found to have misaligned planetary orbital angular momentum axis relative to the spin axis of the host star. How are spin-orbit misalignments produced? We will discuss/review our recent works on the production of spin-orbit misalignments in different HJ/WJ formation channels. Topics include: (1) The role of chaotic stellar spin dynamics as the giant planet undergoes high-eccentricty migration; such stellar spin variation/dynamics plays a dominant role in determining the final spin-orbit misalignment; (2) The possibility of producing primordial spin-orbit misalignment in the disk migration scenario as a result of star-planet-disk-binary interactions; (3) The possibility of producing misaligned multi-planetary systems; (4) The presence or lack of spin-orbit misalignment in a planetary system as a probe of the planet's dynamical history and the physical processes taking place in the planet's birth environment (protoplanetary disks, binaries, etc).
JWST Wavefront Sensing & Control Commissioning Operations
Lajoie, Charles-Philippe
The James Webb Space Telescope’s segmented deployable mirror imposes complex technological and operational challenges, resulting in a telescope commissioning phase spanning several months and involving every instrument and part of the observatory ground system. A carefully planned sequence of mirror segment moves will iteratively sense and adjust the mirrors to achieve an optimal alignment of the optical telescope element (OTE). This commissioning process has been developed through a joint effort of Ball Aerospace, STScI, and NASA Goddard over the past ten years, and has resulted in a robust and well-tested plan for commissioning the JWST OTE.The operational concept for OTE commissioning relies on the same observation planning and operations software as normal science operations, although some particular capabilities were developed in order to handle special cases. Here, we present an overview of the current operations plan to support and execute OTE commissioning, highlight the complexities that certain steps present, and discuss how the telescope commissioning is interwoven with commissioning the instruments. We also discuss the various ways this process has been tested and rehearsed in order to verify readiness of the flight hardware, software, and personnel to ensure an efficient and successful commissioning of JWST.
NGC4869 in Coma cluster: Its collimated radio jet and the role of Kelvin-Helmholtz instabilities
Lal, Dharam
The GMRT upgrade, an SKA pathfinder instrument is almost complete and has begun operations. The upgraded facility will complement several other observatories as essential tool for discovery in several areas of astrophysics. Here, we present radio and X-ray imaging of the Coma cluster, an important 'laboratory' to study the role of cluster environment on the properties of radio sources and demonstrate the importance of multi-wavelength imaging. We would also present a case study, using upgraded GMRT and Chandra, NGC4869 in Coma cluster - we report flaring of a straight, collimated jet at approximately the position where it crosses the surface brightness edge in the hot gas - with an aim to investigate the radio jet collimation on kpc-scales.
Coma cluster: A sharp view using upgraded GMRT
Lal, Dharam
We have used upgraded GMRT, an SKA pathfinder instrument as a testbed to demonstrate the capabilities of wide field, wide band imaging of Coma cluster of galaxies at 1050-1450 MHz and at 250-500 MHz bands. These images detected more than 100 radio sources and here we summarise their radio properties in a statistical sense. We also present spatially resolved radio morphologies and spectral structures, and the effect of intra-cluster medium for several radio galaxies using upgraded GMRT and Chandra. We discuss the importance of multi-wavelength imaging, and the improvements that will be possible due to upgraded GMRT and the role of low-frequency instruments.
Quality of astrometric solution in Gaia DR2
Lammers, Uwe
The backbone of Gaia Data Release 2 (DR2) consists of the astrometric data for 1,692,919,135 sources (1,331,909,727 of which with parallax and proper motion) produced with the Astrometric Global Iterative Solution scheme. Although the solution is overall of excellent quality it is not free of systematic errors and correlations of small, but noticeable levels. Some of the found features in the data are expected and just reflect the fact that Gaia DR2 is based on merely 22 months of mission data and an immature calibration of the astrometric instrument. Other effects in the data were unexpected and are still under investigation. In this paper we characterize and discuss the quality of the solution, outlining its limitations that all users of the data should be aware of.
A 3D hydrodynamical simulation of a black hole outflow in a dwarf spheroidal galaxy
Lanfranchi, Gustavo A.
It is a known fact that large galaxies harbour central black holes with masses larger than $\> 10^6 \msun $ and that their feedback causes an impact in the evolution of the galaxy and the media. Recently, observations suggested that also smaller galaxies host black holes in their center, but with lower masses (intermediate massive black holes - IMBH). The effects of these objects in the evolution of the dSphs have been so far not analysed. In this work, we present results of a study of the effects of a outflow from an IMBH in the gas dynamics of dSph galaxies by means of a non-cosmological, 3D-hydrodynamical simulation. Assuming an initial baryonic-to-dark-matter ratio derived from the cosmic microwave background radiation and a cored, static dark matter gravitational potential, we evolved the galactic gas distribution over 3 Gyr, taking into account the outflow of a IMBH. The outflow is simulated by the injection of density and velocity in both directions of one of the axis. We explored the density and velocity space-parameter in order to determine in which physical conditions the outflow can propagate through the interstellar medium of the galaxy. We adopted a scenario with an homogeneous medium and another one with the feedback of supernovae to infer the differences in the propagation of the outflow. Our results indicate that in a homogeneous medium the outflow propagates freely in both directions with the same velocity and its capable of removing a fraction of the gas from the galaxy. When the SNe are taken into account, the effect of the outflow is reduced. It is necessary a velocity around 1000 $km.s^{-1}$ and a density larger than 0.003 $cm^{-3}$ for the outflow to propagate. In this conditions, the removal of gas from the galaxy is almost negligible at the end of the simulation.
Experience with Student-Constructed Telescopes for Radio Astronomy
Langston, Glen
Our group has designed, documented construction and operated Radio Telescopes intend for use by high schools, colleges, hobbyists and other Science Aficionados. We present our experience with college freshmen that built two telescopes during a two-week summer program. The students operated the telescopes, which they named Alexander and Bess. Their experience was mostly successful, and we learned how to improve documents describing construction and operation. We’re incorporating lessons learned into revised documentation, published on the web at: https://opensourceradiotelescopes.org/wk
Confirmation of Benzonitrile in the Interstellar Medium
Langston, Glen
Complex organic molecules are found in cold clouds in the interstellar medium (ISM) of our Milky Way galaxy.[1][2] Frequently, if one isomer of a molecule is detected, then other isomers will also be found, but with different relative abundances. The formation pathway for these molecules is deduced the relative abundance of different sub-component molecules. The measurement of the relative abundances of isotopomers strongly tests interstellar chemical models. These chemical models are relevant to understanding the origin of line on Earth, because the initial conditions for chemical phenomena on Earth were formed in the ISM. Our observations further extend interstellar chemistry by the first detection of benzene ring through microwave spectroscopy of cold molecular clouds. Here we report the detection in the ISM of benzonitrile, C6H5CN. This is the first individual polycyclic aromatic hydrocarbon identified in the ISM by microwave spectroscopic observations. The Taurus Molecular Cloud 1 (TMC) is long known[3] to be a prime candidate for search for this molecule due to the high abundance of the linear cyanopolyyne molecule, HC7N, with similar molecular mass to benzonitrile. Benzonitrile molecular lines are expected to be much weaker than those for HC7N, due to the complexity of the benzonitrile microwave spectrum.[4] We identify benzonitrile by the weighted sum of a number of spectral lines. This process is described by Langston and Turner 2007[5].[1] Herbst, 1[2] Tielens, A.G.G.M., 2013, Reviews of Modern Physics, 85, 1021[3] Feeman, A. & Millar, T. J. (1983), Nature301, 402[4] J. M. Hollis, Anthony J. Remijan, P. R. Jewell, and F. J. Lovas (2006), Ap. J. 642:933[5] Langston, G. I. and Turner, Barry (2007), Astronomical Journal
Characterization of methanol as a magnetic field tracer in massive star-forming regions
Lankhaar, Boy
Magnetic fields play an important role during star formation. Direct magnetic field strength observations have proven specifically challenging in the dynamic protostellar phase. Because of their occurrence in the densest parts of star forming regions, masers, through polarization observations, are the main source of magnetic field strength and morphology measurements around protostars. Of all maser species, methanol is one of the strongest and most abundant tracers of gas around high-mass protostellar disks and in outflows. However, because experimental determination of the magnetic characteristics of methanol has remained unsuccessful, a magnetic field strength analysis of these regions could hitherto not be performed. In this talk, we present quantum-chemical calculations of the Zeeman-parameters of methanol. We use these parameters in re-analyzing methanol maser polarization observations. With these calculations, we can confirm the presence of dynamically important magnetic fields around protostars.
Angular Momentum of Early- and Late-type Galaxies: Nature or Nurture?
Lapi, Andrea
We investigate the origin,shape,scatter, and cosmic evolution of the observed relationship between specificangular momentum jå and the stellar mass M_star in early-type galaxies (ETGs) and late-type galaxies (LTGs).Specifically, we exploit the observed star formation efficiency and chemical abundance to infer the fraction f_inf ofbaryons that infall toward the central regions of galaxies where star formation can occur. We find f_inf˜1 for LTGsand ˜0.4 for ETGs with an uncertainty of about 0.25 dex, consistent with a biased collapse. By comparing with thelocally observed j_star-M_star relations for LTGs and ETGs, we estimate the fraction f_j of the initial specific angularmomentum associated with the infalling gas that is retained in the stellar component.For LTGs, we findf_j ˜ 1, in line with the classic disk formation picture; for ETGs, we infer f_j ˜ 0.6, which can betraced back to a z<1 evolution via dry mergers. We also show that the observed scatter in the j_star-M_star relationfor both galaxy types is mainly contributed by the intrinsic dispersion in the spin parameters of the host dark matterhalo. The biased-collapse plus merger scenario implies that the specific angular momentum in the stellar components of ETG progenitors at z~2 is already close to the local values, in good agreement with observations. All in all, we argue that such a behavior is imprinted by nature and not nurtured substantially by the environment.
Elongations in Sco-Cen with Gaia DR2
Larreina, Irati
Bouy & Alves (2015) studied the overdensities of massive blue stars in the solar neighbourhood. Using distances for OB stars from the Hipparcos catalogue they identified three large-scale structures, named "blue streams". Confirmation of their results can be crucial to understand the star formation history in many important star forming regions, such as Orion and Sco-Cen.Our interest lies in the study of large-scale structures on the solar vicinity. Using the Tycho-Gaia astrometric solution (TGAS) from GAIA DR1 we created a 3D Kernel Density Estimation (KDE) map. The overdensities on this map correspond mainly to well known clusters and associations of various ages. This was implemented using an Epanechnicov kernel with a bandwidth of 12 pc and error cuts for the parallax and proper motion in RA and Dec < 20%. We also filtered the sample by parallax > 5 (200pc) and B-V < 0.5. Due to the errors in parallax many structures appear elongated towards the Sun, except for the Sco-Cen association (Upper Sco, UCL and LCC), meaning that the elongations in this association might be real. A smaller cluster candidate was found previously categorised as part of UCL and recently studied by Röser et al. (2017) around V1062 Sco. We observe a very prominent gap between UCL and LCC unnoticed before, probably caused by a lower stellar density in the region or the incompleteness of OB stars in the catalogue. We also notice some substructures on Upper Sco and LCC which need further study. We will show the implemented results of these structures using Gaia DR2, available in April. These results will be important to throw light on the star formation history of this association and ultimately test the existence of blue streams.
Celebrating Eddington@Sundy 100 years later
Latas, Joana
The year of 2019 will mark the 100th anniversary of the experiment that confirmed the theory of general relativity. Principe was one of the main stages for the experiment during the total solar eclipse on May 29th, 1919 during an expedition led by Arthur Eddington to Principe. The experiment was also performed in Sobral, Brazil. The observations made in Principe were relevant to the History of Science and following developments in scientific endeavour. We are aiming for a 5-year program, 2015-2019 in which the local community becomes involved and takes ownership of this important initiative. Its culmination, on 29th of May 2019, will bring to Principe a sense of pride and will provide the opportunity for an exchange with the international scientific community. The centenary celebrations on Principe will promote a scientific and educational programme, through 4 pillars: Science, History of Science, Science Education and Outreach. The expected outcomes of this project range from the creation of a thematic space near the site where the observations took place in Principe Island to the production of a documentary devoted to the centenary, as well as exhibits and publications of the scientific events taking place during the event.
Observations of the Starburst Galaxy M82 with SOFIA/FIFI-LS
Latzko, Serina T.
The active galaxy M82 at 3.7 Mpc is one of the closest laboratories to study massive starburst phenomena in detail. Radio observations revealed two Ultra Luminous X-Ray Sources (ULXs) near its center. Optical and near-infrared (NIR) observations focused on super star clusters in the core of M82 while the cool and warm molecular interstellar medium (ISM) was investigated using Infrared Space Observatory (ISO) observations in the mid-infrared (MIR) and far-infrared (FIR). We present new [CII] 157µm observations on the galactic wind emerging perpendicular to the disk of M82 at high velocities obtained with FIFI-LS onboard SOFIA using its spectral mapping capability. Our data also extend the investigation on the processes prevailing in the core of M82 by using spectral lines that were previously inaccessible, e.g., [OIII] 52µm, in particular at high angular resolution of about 6 arcsec.
The "Science Accelerator: Mission Mars"
Laufer, Diana
The "Science Accelerator: mission Mars" is a unique course for high school students to develop entrepreneurship and innovation in science. The course focuses on planet Mars and especially future plans to colonize the planet.The science accelerator based on the Start-Up accelerators programs, led by Vered Cohen Barzilay – Social entrepreneur and Mentor at the "8200 Social Accelerator" in Israel.At the science accelerator, the students' mission was to create a product that will help the science community in their mission to colonize Mars. They were instructed to look for ideas that will be: practical, scientifically based and innovative.The two classes (60 students) were divided into working groups and started dreaming. Soon after the “start-up nation” students, found unique and innovative ideas: GOODEYE HELMET - Solutions for people with short-sightedness or hyperopia, SPACE FASHION -Personalizing astronauts suits, ELECTRIC SPACE - Green Electricity home device produce from carbon dioxide, CLEAN SHEILD - Cleaning Robot for Habitats on Mars, SPACEBALL - Playing football on Mars, DIS(ABLE) IN SPACE - Solutions for disabled on Mars, RESCUE-M - Rescue cars on Mars with rescuing equipment and PLANT MARS -Greenhouse for Mars.During the learning period, enjoyed lectures and interactive lessons, pitching and working with a 3D printer to support the students in their first steps as a startup-space entrepreneur.The students visited Givatayim Observatory and met with top scientists and entrepreneurs such as Dr. Eugene Tu, Director of Ames Research Center, NASA and Jacob Cohen Ames Chief Scientist, Nader Haghighipour from the Institute for Astronomy University of Hawaii, Reut Sorek-Abramovitch, a scientist at D-Mars, Shmuel Barzilay, Ophir Optronics Solutions, Yaniv Saban, owner of Yaniv Saban Digital Marketing Consulting.Video Linkhttps://www.youtube.com/watch?v=nn9EmC71t3g&feature=youtu.beThis project is supported by the Israeli Ministry of Science and Technology.
Noble gases and volatiles delivery from comets to Earth
Laufer, Diana
Direct measurements by the Rosetta spacecraft on Comet 67P/C-G composition together with our laboratory experiments of gas trapping in amorphous ice improve our understanding of the gas composition and the formation condition of the ice grains in the protosolar nebula (PSN) and the source of the Earth's atmosphere and the building blocks of life.For the first time in comet research, the Rosetta spacecraft detected O2, N2 and also noble gases: argon, krypton and xenon and their isotopes, and absence of neon. Comparing these measurements to our experimental results of gas-laden amorphous ice, the formation temperature of the cometary ice grains was =35 K. This temperature is close to the temperatures observed for the circumstellar dust shells around a PsA (55 K), e Eri (45 K) and Ori A PPD Class II (40-65 K).Noble gases are key tracers for understanding the origin and their contribution to the planetary atmospheres. The ROSINA mass spectrometers of the Rosetta spacecraft measured their isotopic abundances. Argon isotopes are depleted as compared to solar. This can be explained by our experimental results of trapping of argon in amorphous ice, being strongly dependent on the formation temperature of the ice. At 35-50 K, not all the argon was trapped in the amorphous ice, as krypton and xenon, with a depletion factor of up to 2. The xenon isotopes in 67P/C-G are significantly different from solar.A possible explanation can be xenon being trapped also in CO2 ice or recondensed on the night side.For other volatiles, N2 and Ar are depleted as compared with O2, as derived also from our experiments. CO and CO2 vary for different comets as also the D/H ratio, being explained by inhomogeneity in the PSN.The measurements of comet 67P/C-G together with our experimental results set a limit to the formation conditions and abundances of the volatiles delivered to the Terrestrial planets.This research was supported by the Israel Space Agency, Ministry of Science and Technology.
Late Thermal Pulse Evolution Models and the Rapid Evolution of V839 Ara
Lawlor, Timothy
We present evolution calculations from the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PNe) phase for models of mass 1 M? over a range of metallicities from primordial, Z = 10-14, through Z = 0.03. The understanding of these objects plays an important role in galactic evolution and composition. Here, we particularly focus on Late Thermal Pulse (LTP) models, which are models that experience an intense helium pulse that occurs just following the AGB and causes a rapid looping evolution between the AGB and PN phases. This transient phase only lasts for decades and centuries while increasing and decreasing in temperature, luminosity and size over many orders of magnitude. For this and similar phases, we can and have observed stellar evolution in real time (e.g.; Sakurai's Object and FG Sge). In this paper, we use our LTP models to make comparisons to the central star of the Stingray Nebula, (V839 Ara; SAO 244567). This object has been observed to be rapidly evolving and heating over more than 50 years and is the central star of the youngest known planetary nebula. These characteristics are expected and seen in LTP models. However, the observations have proven difficult to reporduce because this central star has a high log(g) but lower temperature compared to models.
Changing the Landscape: New Ways of Tracing and Probing Magnetic fields with Velocity and Synchrotron Gradients
LAZARIAN, ALEXANDRE
Modern understanding of MHD turbulence suggests that this type of turbulence is strongly anisotropic at small scales. This entails a conclusion that gradients of velocity and magnetic field are perpendicular to the local direction of the magnetic field. Guided by this fact we proposed, developed and successfully tested with observational data a set of new techniques for studying interstellar magnetic fields. I shall demonstrate how the velocity gradients can be measured using either velocity centroids of thin channel spectroscopic maps, while magnetic field gradients can be measured using synchrotron intensity or synchrotron polarization. I shall present 3D maps of galactic magnetic fields obtained with the new technique, demonstrate that gradients can provide both magnetic field tracing and identify the regions of graviational collapse. I shall discuss new ways of obtaining magnetic field strength using the gradients. I shall show how to use different types of gradients to map the structure of the magnetic web within the multiphase interstellar media.
Analysis of spectrum variations in Hercules X-1 in terms of the accretion flow
Leahy, Denis
Hercules X-1 was observed extensively by the Rossi X-ray Timing Explorer (RXTE) over its 17 year lifetime. Here, the RXTE/PCA spectrum observations over the full 35 day cycle are analyzed. The spectral variations over 35-day phase are characterized and seen to have a regular behaviour. The changes are interpreted in terms of the precessing accretion disk. The most important variation is caused by the changing illumination of the inner edge of the disk, but other variations with different causes are also seen.
Radio Properties of AGN in the GAMA 23 Field
Leahy, Denis
The GAMA 23 Field, a region of about 6 degrees by 7degrees, was observed by the Australia Square Kilometer Array Pathfinder (ASKAP) during its commissioning phase. We utilize the radio data from ASKAP in conjuntion with the optical data from the GAMA survey, and infrared data from the WISE survey to investigate the properties of AGN over this large field. A number of well-known properties of the AGN population are confirmed but we find some new properties because of the large area and sensitivity of the radio and optical data, which allows low mass galaxies to be identified out to a redshift of about 0.5.
The Laboratory Calibration of the UVIT detectors for the ASTROSAT observatory
Leahy, Denis
The UVIT ultraviolet and visual band detectors and electronics for the ASTROSAT observatory were calibrated in the vacuum laboratory at the University of Calgary. This work was supported by the Canadian Space Agengy and carried out prior to integration with the UVIT optical assembly and the ASTROSAT spacecraft. The multiband (X-ray, UV and optical) ASTROSAT observatory was successfully launched by the Indian Space Research Organization on Sept. 28, 2015, with subsequent in-orbit verification and ongoing calibration activities. Here we discuss the current issues of calibrating the UVIT data, such as distortion corrections, and how the laboratory data is being used to address these issues.
The ASTROSAT Light-Curve and Spectrum of Hercules X-1
Leahy, Denis
ASTROSAT is a multi-wavelength observatory with 4 main instruments: UVIT, an ultraviolet and visible wavelength telescope; SXT, a soft X-ray imaging telescope; LAXPC, a broad-band large-area X-ray timing instrument; and CZT, a hard X-ray coded-mask imaging telescope. These four instruments operate simultaneously and are co-pointed, yielding a very wide band view of X-ray and UV emitting systems. ASTROSAT carried out an observing campaign on the X-ray binary Hercules X-1 during 2016-2017. Here we report on the results of these observations, focussing on the light curve in different energy bands and the X-ray spectrum in different states of the system.
UV Photometry of the Most Massive Stars in M31
Leahy, Denis
We obtain near- and far- ultraviolet (NUV and FUV) high spatial resolution (1 arc-second) photometry of M31. The observations were made with the UVIT instrument on board the ASTROSAT observatory. This NUV and FUV photometry is combined with HST NUV and visible wavelength photometry to study the brightest NUV and FUV objects in M31. Stellar models are applied to the photometry to determine the properties of the hot massive stars. We also determine which ones are not consistent with single stars, but rather are likely interacting binaries.
New HI Absorption Distances for Galactic Supernova Remnants
Leahy, Denis
We use absorption by neutral hydrogen from the ISM and emission from CO to obtain new distances for Galactic supernova remnants (SNRs). The area of the Galaxy studied is between longitudes of 15 and 60 degrees. An updated Galactic rotation curve for this region of the Galaxy is used to convert absorption and emission line velocities into distance limits for the SNRs. We are able to obtain new distances for 30 SNRs in the surveyed area. Implications of the new distances are discussed.
GRB X-ray light curve types, and the nature of dark energy.
Leaman, Jesse
Following an analysis of 775 (739 long, 36 short) Gamma-ray bursts (GRB) from 2005 to 2017 it was found that GRB types should be based on the x-ray light curve (LC) shape, the number of breaks in the LC, and the LC slope (steep or shallow) between breaks. The 36 SGRBs fall into one of 7 types, likely the merger of a certain combination of compact objects, neutron stars and black holes. The 739 LGRBs fall into one of four optical afterglow (OA) families: Supernova (5 types), Kilonova (32 types), Forward shock (15 types), and Dark (13 types). Most GRB types, Kilonova and Supernova, arise from different inclination angles, and gas and dust distributions, around collapsing massive stars. Other types, especially those with little or no OA, and occurring near the center of galaxies, might represent the annihilation of matter and antimatter (AM). The later may be evidence of the release of dark energy (DE), and the creation of dark matter (DM). The first black holes (BHs) twisted space-time (ST) into strings a plank length (lp) in radius, with vast tensile strength. Over the eons, BHs merged within their potential wells, lp-strings became entangled, and BHs grew to massive sizes at the center of their own galaxies. The lp-strings connecting BHs in separate potential wells, stretch as the universe expands, until they tear, and ST unravels, reducing the mass/size of the BHs.When the AM emerges from the event horizon, a GRB is accompanied by an X-ray flare, and a stream of neutrinos. Information about the original entanglement determines the vector and mass of the expelled AM. Conservation of momentum requires the galaxy to experience an acceleration in the opposite direction, resulting in the accelerated expansion of the universe observed today. Evidence that this conversion of stored DE has been ongoing for billions of years, can be found in the DM distributions around, and between, clusters of galaxies.
Carbon and oxygen isotopes in AGB stars, from the cores of AGB stars to presolar dust
Lebzelter, Thomas
Isotopic ratios are a powerful tool for gaining insights into stellar evolution and nucleosynthesis. The isotopic ratios of the key elements carbon and oxygen are perfectly suited to investigate the pristine composition of red giants, the conditions in their interiors, and the mixing in their extended atmospheres. Of course the dust ejected from red giants in their final evolution also contains isotopically tagged material. This red giant dust is present in the solar system as presolar dust grains. Thus evolved star C and O isotope ratios can be measured in two ways, spectroscopically in the atmospheres of red giant stars and in grains in the laboratory.We have measured isotopic ratios of carbon and oxygen in spectra from a large sample of AGBstars including both miras and semiregular variables. We show how the derived ratios compare with expectations from stellar models and with measurements in presolar grains. We will show how the isotopes measure the initial stellar masses of AGB stars. Comparison of isotopes that are affected by different types of neuclosynthesis provides insights into galactic evolution.
Detecting turbulence in large scale structures with X-ray satellites.
Lecoq, Edouard
Understanding the baryonic processes taking place in the large scale structures of the Universe is essential both if we want to understand structure formation and the biases they may induce in cosmological studies (e.g. s8 or ?m). Among those processes, turbulent motions that are induced at various scales, for instance by AGN jets or accretion of matter from intergalactic filaments, are crucial. At those scales, turbulence can potentially be tracked through the X-ray emission & absorption of the gas. We will present our results on the detectability of turbulent motions on the largest scales of the Universe that future X-ray satellites may offer.
On the origin of the consequent brightening of coronal loops in solar flare arcades
Ledentsov, Leonid
With the purpose of interpreting modern satellite observations of successively increasing the brightness of individual coronal loops in solar flares, we solved the problem of the stability of small longitudinal perturbations of a homogeneous reconnecting current layer in the MHD approximation. The suppression of the plasma thermal conductivity by the magnetic field inside the current layer provides an instability. The instability increases in a radiative cooling time scale of the plasma in the linear phase. A periodic structure of hot and cold fibers arranged transversely to the direction of the electric current are formed as a result of the instability. The proposed mechanism of the thermal instability can be useful for an explanation of the consistent increase in the brightness of individual coronal loops in solar flares.
Stellar Wind Accretion and Raman O VI Spectroscopy of the Symbiotic Star AG Draconis
Lee, Young-Min
Symbiotic stars(SySts) are wide binary systems of a mass losing giant and a hot white dwarf. Nearly half of SySts exhibit broad Raman scattered O VI scattered features at 6825Å and 7082Å. Formed through inelastic scattering of O VI??1032 and 1038 with neutral hydrogen, they provide important information about the mass loss and mass transfer processes. Adopting a Monte Carlo method, we perform a profile analysis of Raman O VI features of the yellow SySt AG Draconis based on asymmetric Keplerian accretion flow around the white dwarf. Our best fit to the spectra obtained with the Canada-France-Hawaii Telescope is obtained from our model with a mass-loss rate of the giant ~ 4 × 10-7 M_sun yr-1. A slight red excess in the observed data suggests the presence of the bipolar neutral component receding directions perpendicular to the O VI emission region with a speed ~ 70 km s-1.
Ram pressure stripping effect on dwarf galaxies in the Virgo cluster
Lee, Woong
We investigate star formation quenching of galaxy population in the Virgo cluster under ram pressure stripping effect using VLA Imaging of Virgo spirals in Atomic gas (VIVA) survey data. We adopted four subgroups of 40 VIVA galaxies at various stages of ram pressure stripping (pre, early, active, and past) classified by Yoon et al. based on the basic HI properties. Assuming that low-mass galaxies around massive VIVA galaxies are likely to be influenced by the similar level of ram pressure effect, we selected neighbor galaxies possibly associated with each VIVA galaxy using kinematic data from the Extended Virgo Cluster Catalog (EVCC). Additionally, we also classified galaxies in VIVA and Ursa Major group without any hint of gas stripping. We investigate optical and ultraviolet (UV) photometric properties of galaxies in four subgroups spanning a wide range of brightness (-21 <mr <="" -12)="" using="" sdss="" optical="" and="" galex="" uv="" data.="" in="" the="" near-uv="" (nuv)="" -="" r-band="" color-magnitude="" relation,="" nuv-r="" colors="" of="" galaxies="" subgroups="" become="" redder="" with="" ram="" pressure="" stripping="" stages,="" which="" is="" good="" agreement="" orbital="" history="" described="" by="" yoon="" et="" al.="" a="" phase-space="" diagram.="" we="" find="" that="" faint,="" dwarf="" active="" past="" are="" more="" rapidly="" quenched,="" while="" massive="" counterparts="" still="" star="" formation="" activity.="" observationally="" confirm="" effect="" critical="" process="" for="" star-forming="" systems="" into="" a red="" galaxy="" cluster="" environment,="" especially="" low-mass="" on="" very="" short="" timescale.="" other="" hand,="" lower="" dense="" environments="" outskirt="" group,="" gravitational="" influence="" nearby="" could="" not="" be="" enough="" passive="" evolution="" neighbor="" from="" blue="" cloud.<="" p="">
</mr></mr></mr></mr></mr></mr>
The Nature of Ultra-diffuse Galaxies in Massive Galaxy Clusters
Lee, Jeong Hwan
Ultra-diffuse galaxies (UDGs) are an intriguing galaxy population, because they are as large as the Milky Way but have surface brightness fainter than typical dwarf galaxies.The origin of the UDGs has been controversial: whether they are massive giant galaxies which failed forming stars or they are extended dwarf galaxies.The Hubble Frontier Fields (HFF) program is useful to study the UDGs in massive galaxy clusters.In this study, we present our search for UDGs in three massive clusters, Abell 2744 (z=0.308), Abell S1063 (z=0.348), and Abell 370 (z=0.374), using deep images of the HFF.We find a large amount of UDGs in each cluster.The color-magnitude relations show that the colors of most UDGs are consistent with the faint end of the red sequence of the cluster members.This suggests that UDGs are mainly composed of old stars.However, a few blue UDGs indicate the presence of young stars.This implies that not all cluster UDGs are quenched.The stacked radial number density profiles of UDGs show a flattening feature in the central region, in contrast with those of bright galaxies. This implies that tidal disruptions contribute to the lower number density of UDGs in the central region of the clusters.We indirectly estimate the virial masses (M_200) of the UDGs using the fundamental manifold.The virial masses of most UDGs range from 10^10 M_Sun to 10^11 M_Sun, suggesting that they are dwarf-origin UDGs.However, several UDGs have virial masses larger than 10^11 M_Sun, indicating that they are failed giant galaxies.In conclusion, UDGs in massive galaxy clusters are formed via both dwarf and giant origins.
Environmental dependence of surface brightness profile types of dwarf galaxies
Lee, Youngdae
We investigate surface brightness profiles (SBPs) of dwarf galaxies in field, group, and cluster environments. Using images from the Korea Microlensing Telescope Network (KMTNet) Supernova Program (KSP) for the NGC 2784 group and SDSS for the Virgo cluster, SBP types are classified into profiles with single exponential (Type I), double exponential (Type II and Type III). Type II and Type III have smaller and larger outer sizes than inner sizes, respectively. SBP types of field dwarfs are compiled from a previous study. The distributions of SBP types are different in three environments. Common SBP types of the field, the NGC 2784 group, and the Virgo cluster are Type II, Type I and II, and Type I and III profiles, respectively. After comparing sizes of dwarfs in different environments, we suggest that since sizes of some dwarfs are changed due to the environmental effects, SBP types are able to be transformed. It makes that the distributions of SBP types in three environments are different. We discuss possible environmental mechanisms on the transformation of SBP types.
Origin of Hot Bubble in NGC 6822 Hubble V Star-Forming Regions
Lee, Hye-In
NGC6822 is an irregular galaxy whose star-forming environment is free of dynamical driving effects. At a distance of ~500 kpc, we can spatially resolve molecular clouds or star-forming regions clearly down to parsec scales. Some of the bright HII regions of NGC6822 have bubbles produced by supernova. We observed the bright HII complex in NGC6822 Hubble V, using an infrared spectrometer, IGRINS, attached on the 2.7 m telescope at the McDonald Observatory. We performed a slit scan mapping of 15" × 7" region (35 × 17 pc) in H and K bands with a spectral resolving power of 45,000. Emission lines of Br? ?2.1661 µm and He? ?2.0587 µm from ionized regions were detected. Additional obtained lines are molecular hydrogen lines of 1-0 S(1) ?2.1218 µm, 2-1 S(1) ?2.2477 µm, and 1-0 S(0) ?2.2227 µm from photo-dissociation regions (PDRs). We show three-dimensional maps of the emission lines and discuss a hot bubble scenario with an expanding ionized shell structure around the central stellar cluster.
Enabling HST UV Exploration of Dwarf Galaxies and the Low Surface Brightness Universe
Lee, Janice
We present a HST pilot program to broadly enable high-resolution UV exploration of star formation at low densities in nearby galaxies using a strategy to increase observing efficiency by up to a factor of two. The increased efficiency makes more tractable programs which require several tens to hundreds of orbits to aggregate sufficient numbers of resolved massive stars, young star clusters, and clumps to build statistical samples. We aim to enable basic characterization of the ensemble properties of star formation in the low density regime in its primary units. We will discuss first results based on the nearby dwarf galaxy Holmberg I.
What the iMOGABA tells us about Gamma-ray bright AGNs
Lee, Sang-Sung
The interferometric monitoring of gamma-ray bright AGNs (iMOGABA) program aims at revealing the origins of the gamma-ray flares that are often detected in active galactic nuclei (AGNs). We would like to talk about what we have learned about the Gamma-ray bright AGNs based on the recent results of the Korean VLBI Network Key Science Program: the iMGOABA. The results will include a) the source properties of the whole samples obtained from a single-epoch observation, and b) some of scientific highlights for the iMOGAGBA on specific sources. From those highlighted works, we find that the Gamma-ray bright AGNs become fainter at higher frequencies, yielding optically thin spectra at mm wavelengths. Based on the studies on specific sources, taking into account the synchrotron self-absorption model of the relativistic jet, we are able to estimate the magnetic field strength in the mas emission region during the observing period. More scientific highlights and future prospects of the KVN KSP are discussed.
Radio-loud fraction of high-z low-luminosity HSC/Subaru quasars
Lee, Kianhong
The co-evolution between super-massive black holes (SMBHs) and their host galaxies has become one of the biggest mysteries in the modern astronomy. In the active galactic nucleus (AGN)-feedback scenario, theoretical studies show that the radio-mode feedback has a significant impact on shaping the bright-end of the galaxy luminosity function. Radio-loud AGNs, a sub-class of AGN populations, provide a laboratory to study the physical processes associated with the radio-mode feedback in galaxies, yet we still lack a complete understanding of the existence of two populations which are divided by whether they show the strong radio emission or not.In the local or lower redshift universe, some studies showed that the radio-loud fraction tend to depend on both the redshift and the optical luminosity, while it has been argued that the result is biased by the apparent magnitudes. Such potential bias can become more significant at higher redshifts, and in fact, previous studies on radio-loudness of high-z (z>5.5) quasars are focused on the very luminous ones which likely host heavy SMBHs.However, recently, a sample of more than 80 high-z (z~6) lower luminosity quasars has been discovered by an on-going deep and wide-area multi-band optical imaging survey with the Hyper Suprime-Cam (HSC) on Subaru 8-m telescope (Matsuoka et al. 2016, 2018ab). Most of these newly uncovered z~6 quasars have the lower rest-UV luminosity (M_1450 > -25 mag) and thus fall near the break of the quasar luminosity function at z~6, which means that their properties are more representative compared to the known luminous ones in the early universe.Toward this valuable new sample, we have conducted radio follow-up observations with JVLA at 1.4 GHz. At this moment, 16 targets have been observed with a typical sensitivity of about 10-30 uJy (1 sigma). In this presentation, constraints on the radio-loud fraction of such low-luminosity z~6 quasars will be presented for the first time.
Analysis of Astronomical Almanacs of Manchukuo
Lee, Ki-Won
We investigate the astronomical almanacs of Manchukuo, a Japanese puppet state that lasted for 14 years from 1932 to 1945. In this study, we explore Manchukuo almanacs for the years from 1934 to 1945 except for 1941. From examination of the contents, we find that the name of the almanac is the same as that of the Qing dynasty in China, Shixianshu, and that it was published as two versions in Chinese and Mongolian, at least in case of the almanac for the year 1945. We also find that the reference location of the time data was Xinjing (nowadays Changchun) and that the standard meridian was changed from 120° E to 135° E since the almanac of 1937. In addition, we observe that sunrise and sunset times are recorded on only the days of 24 solar terms but for several cities, while moonrise and moonset times are recorded daily but only for Xinjing. Moreover, only days are recorded (i.e., the hours are not recorded) in the almanacs of 1934 for 24 solar terms. In order to estimate the accuracy of the time data, we extract eleven kinds of time data from the almanacs: solar term, four phases of the Moon (i.e., new moon, first quarter moon, full moon, and last quarter moon), rising and setting of the Sun and Moon, and eclipses of the Sun and Moon. Then, we compare those time data with the results of modern calculations obtained using the DE405 ephemeris. Even though the time data are tabulated until the unit of minutes in the almanacs except for solar eclipse times, we calculate until the unit of seconds and determine the mean absolute deviation (MAD) for each kind of time data. We find that the MAD value for all kinds of time data is approximately 0.33 min, while the maximum deviation is 0.45 min for the times of lunar eclipse. In conclusion, we think that our findings will contribute to the study of astronomical almanacs of Korea, China, and Japan that were published during the similar period.
Study on the effects of non-equilibrium ionization on EUV and X-ray observations
Lee, Jin-Yi
During a major solar eruption, the erupting plasma is possibly in non-equilibrium ionization state with its rapid heating or cooling events. The non-equilibrium ionization process is important in a rapidly evolving system where the thermodynamical time scale is shorter than the ionization or recombination time scales. We investigate the effects of non-equilibrium ionization on EUV and X-ray observations by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory and X-ray Telescope (XRT) on board Hinode. For the investigation, first, we find the emissivities for all the lines of ions of elements using CHIANTI 8, and then we find the temperature responses multiplying the emissivities by the effective area for each AIA and XRT passband. Second, we obtain the ion fractions using a time-dependent ionization model (Shen et al. 2015), which uses an eigenvalue method, for all the lines of ion, temperature, and a characteristic time scale, net, where ne and t are density and time, respectively. Lastly, the ion fractions are multiplied to the temperature response for each passband, which results in a 2D grid for each combination of temperature and the characteristic time scale. This is the set of passband responses for plasma that is rapidly ionized in a current sheet or a shock. We predict the observational brightness in the AIA and XRT using these responses. We discuss the differences of the predicted observations in non-equilibrium and equilibrium ionization state.
3-D Oscillations of 21 Halo Coronal Mass Ejections by Multi-spacecraft
Lee, Harim
We have made an investigation on the 3-D oscillation (radial and azimuthal wave modes) of full halo coronal mass ejections (HCMEs). For this, we consider 21 HCMEs which are simultaneously observed by SOHO and STEREO A & B from August 2010 to August 2012 when they were roughly in quadrature. Using the SOHO/LASCO C3 and STEREO COR2 A & B running difference images, we estimate the instantaneous speeds of the HCMEs at 24 different position angles. We find that all these HCMEs have experienced quasi-periodic variations of the instantaneous radial velocity with the periods ranging from 24 to 48 minutes. The oscillations in 21 events are found to be associated with distinct azimuthal wave modes with the azimuthal wave number m=1 for seventeen events (about 80 %). The oscillating directions (or polarization) of the nodes of m=1 mode for these HCMEs are quite consistent with those of their position angles (or direction of eruption) with the mean difference of 22 degrees. The amplitude is found to well correlate with the projected speed. These facts support that 3-D oscillations of these CMEs are mainly related to solar eruptions.
Physical Nature and Orbital Behavior of the Eclipsing System UZ Leonis
Lee, JaeWoo
New CCD photometric observations of UZ Leo were obtained between February 2012 and April 2013, and on February 2017. Its physical properties were derived from detailed analyses of our light curves and existing radial velocities. The results indicate that this system is a totally-eclipsing A-subtype overcontact binary with both a high fill-out factor of 76 % and a third light source contributing 12 % light in the B bandpass, 10 % in V, and 7 % in R. The light residuals between observations and theoretical models are satisfactorily fitted by adopting a magnetic cool spot on the more massive primary star. Including our 12 measurements, a total of 172 eclipse times were used for ephemeris computations. We found that the orbital period of UZ Leo has varied due to a periodic oscillation superposed on an upward parabolic variation. The observed period increase at a rate of +3.49 x 10-7 d yr-1 can be plausibly explained by some combination of non-conservative mass transfer from the secondary to the primary component and angular momentum loss due to magnetic braking. The period and semi-amplitude of the oscillation are about 139 yrs and 0.0225 d, respectively, which is interpreted as a light-time effect due to a third component with a mass of M3 sin i3 = 0.30 Msun. Because the third lights of 7-12 % indicate that the circumbinary object is very overluminous for its mass, it would possibly match a white dwarf, rather than an M-type main sequence.
Near-infrared observations of supernova remnants in M33
Lee, Ho-Gyu
We present near-infrared imaging and spectroscopic observations of supernova remnants (SNRs) in M33. The SNRs are detected by our UKIRT near-infrared [Fe II] and H2 narrow band imaging of M33. For the detected SNRs, we perform follow-up spectroscopic observations using GNIRS on Gemini. The shock-heated SNR is clearly detected in the narrow band [Fe II] image, while the photoionized giant H II region is undistinguished even to the larger scale. We also detect H2 emission for some of the SNRs, suggesting that the SNRs are interacting with molecular clouds and significantly impact their surrounding conditions. We compare our results to the cases of SNRs in Milky Way. The spatially resolved distributions of two emission lines indicate that the line-emitting gases are in different conditions, resulting from the influence of evolution of massive star through stellar wind and interaction with surrounding. Additional observations including integral field unit spectroscopy and ALMA molecular line observations are needed to understand the SNRs and their effects to the environments simutaneously.
Color Dispersion as an Indicator of Stellar Population Complexity in Galaxies
Lee, Joon Hyeop
We investigate the properties of 32 bright (Mr = -21.3 mag) galaxies with various morphological types in two low-redshift clusters Abell 1139 and Abell 2589, using the pixel color-magnitude diagram (pCMD) analysis technique. After masking contaminants with two-step procedures in our CFHT/MegaCam observation images, we examine how the detailed properties in pCMDs depend on galaxy morphology and infrared color. The mean g - r color as a function of surface brightness (µr) in the pCMD of a galaxy shows fine performance in distinguishing between early- and late-type galaxies, but it is not perfect because of the similarity between elliptical galaxies and bulge-dominated spiral galaxies. On the other hand, the g - r color dispersion as a function of µr works better. We find that the best set of parameters for galaxy classification is the combination of the minimum color dispersion at µr = 21.2 mag/arcsec2 and the maximum color dispersion at 20.0 = µr = 21.0 mag/arcsec2: the latter reflects the complexity of stellar populations at the disk component in a typical spiral galaxy. Finally, the color dispersion measurements of an elliptical galaxy appear to be correlated with the WISE infrared color ([4.6] - [12]). This indicates that the complexity of stellar populations in an elliptical galaxy is related with its recent star formation activities. From this observational evidence, we infer that gas-rich minor mergers or gas interactions may have usually happened during the recent growth of massive elliptical galaxies.
Photometric Properties and Spatial Distribution of RSGs of Nearby Galaxy System: Leo Triplet
Lee, Sowon
We present the near infrared JHK photometric properties and the spatial distribution of red supergiants(RSGs) of NGC 3623, NGC 3627 and NGC 3628 in the Leo Triplet system using the data obtained with 3.8m UKIRT(United Kingdom Infra-Red Telescope) at Hawaii. We checked interaction between the three galaxies by making a spatial density map of RSGs. From (J-K,K)0 Color-Magnitude Diagram which include resolved stars in three galaxy and control field with PARSEC isochrone, we figured out the RSG candidates of the Leo triplet are at 1.0 < (J-K)0 < 1.3, mK < 17.5 and separated them from background and foreground sources. Using gaussian kernel density estimation, we drew spatial density map of RSGs in the Leo triplet with an assumption that all RSGs are an identical population. The density map shows extended features of NGC 3628 to NGC 3627 along the declination direction. The asymmetries between NGC 3627 and NGC 3628 might be evidence for that the distribution of actual star components(RSGs) follows the neutral hydrogen distribution and also for interaction between two galaxies. And the extended features along the right ascension direction might be a supporting evidence for the existence of a TDG(Tidal Dwarf Galaxy). In case of NGC 3623, we could not see any sign of interaction in density map.
Tidal interactions shaping dwarf galaxies
Lee-Waddell, Karen
Dwarf galaxies are easily shaped by the influence of neighbouring systems. Accordingly, these low-mass objects can be used to probe the dynamical processes that are affecting the environments in which they are contained._x005F I will present observational data of an assortment of dwarf galaxies that are being formed and/or evolved by tidal forces. The neutral hydrogen gas and stellar content of these galaxies enable a more complete interpretation of the internal dynamics. In most cases, the multi-wavelength datasets coalesce on a common evolutionary history; however, there are a few objects for which the data appear almost contradictory.
Oral Histories of Individuals Involved in Astronomy in South Africa
Leeuw, Lerothodi
We will present progress and future plans of a project on oral histories of individuals involved in astronomy in South Africa. The project is to conduct, archive and showcase the recording of histories of individuals involved in astronomy in South Africa, and will mark one of the first initiatives of South Africa's National Research Foundation Roadmap for the History of Astronomy in South Africa. Uniquely, the interviews will be video recorded, transcribed, and made publicly available online. In interviews of these individuals, the scientific practice, discovery and innovation of astronomy in South Africa will be recorded for analytical study and presentation in scholarly outputs and public outreach presentations, as well as archiving.
Bright Merger-nova Emission Powered by Magnetic Wind from a Newborn Black Hole
Lei, Weihua
Mergers of neutron star–neutron star (NS–NS) or neutron star–black hole (NS–BH) binaries are candidate sources of gravitational waves (GWs). At least a fraction of the merger remnants should be a stellar mass BH with sub-relativistic ejecta. A collimated jet is launched via the Blandford–Znajek mechanism from the central BH to trigger a short gamma-ray burst (sGRB). At the same time, a near-isotropic wind may be driven by the Blandford–Payne mechanism (BP). In previous work, additional energy injection to the ejecta from the BP mechanism was ignored, and radioactive decay has long been thought to be the main source of the kilonova energy. We propose that the wind driven by the BP mechanism from the newborn BH’s disk can heat up and push the ejecta during the prompt emission phase or even at late times when there is fall-back accretion. Such a BP-powered merger-nova could be bright in the optical band even for a low-luminosity sGRB. We apply this model to explaine the kilo-nova in GW170817.
The II Zw 40 Super Nebula
Leitherer, Claus
We discuss HST COS G140L spectroscopy of the enigmatic nearby blue compact dwarf galaxy II Zw 40. The galaxy hosts a nuclear super star cluster with a luminosity 10 times that of 30 Doradus, the most powerful giant HII region in the Local Group. The super star cluster has been suggested to be the ionizing source of a ”supernebula” detected via its free-free radiation in the radio. The physical conditions, however, are much more complex, as demonstrated by the detection of the nebular He II and the mid-infrared line of [O IV] 25.9. These lines are unlikely to be related to hot stars and require a different powering source. II Zw 40 shares many similarities with the related blue compact dwarfs NGC 5253 and Henize 2-10. However, II Zw 40’s UV spectrum is unique in terms of the exceptional strength of He II 1640, O III 1663 and CIII 1909. We determined reddening, age, and the stellar initial mass function and perform a comparison with the local benchmark 30 Doradus. Photoionization modeling is used to determine the origin of the nebular lines as due to stellar ionization, shocks, or powering by a black hole. Series deficiencies in the stellar evolution models are revealed by the presence of excessively strong stellar He II.
Observed versus modelled stellar CME rates
Leitzinger, Martin
Stellar coronal mass ejections (CMEs) may play an important role in stellar and planetary evolution, therefore the knowledge on parameter distributions of this energetic activity phenomenon is highly relevant. During the last years several attempts have been made to detect stellar CMEs of late-type main-sequence and pre main-sequence stars from dedicated optical spectroscopic observations. Up to now only a handful of distinct stellar CME detections are known which contradicts the results from stellar CME modelling, which predict higher CME rates. We report on dedicated ongoing and future observational attempts to detect stellar CMEs and discuss the observational results with respect to the results from stellar CME modelling.
Backward orbital evolution of the Vesta Family without and with the Yarkovsky effect
Leliwa-Kopystynski, Jacek
In our previous paper (Wlodarczyk and Leliwa-Kopystynski, 2018) orbital evolution of the Vesta Family Members (VFMs) was investigated 1 Gy forward. Presently evolution 1 Gy backward is considered. The starting data set is from the catalogue of proper synthetic elements (ASTDyS catalogue, 2015) is the same as previously. Physical parameters of the asteroid Vesta (density 3456 kg m-3, and visual albedo 0.4228) are the same as well. Physical parameters of the VFMs (geometric albedo 0.4228, the mean density 2000 kg m-3, the surface density 1500 kg m-3, the heat conductibility 0.01 W m-1 K-1, the specific heat of the near-surface layer of all VFMs, 680 J kg-1 K-1 were the same as well. The Hierarchical Clustering Method (Nesvorny, 2012) was applied. With the cutting velocity vcut = 54 m s-1 there were chosen 17164 VFMs. Starting keplerian orbital elements of VFMs were taken from the Lowell catalogue (2015). For studying evolution of orbital elements the code SWIFT of Broz (2006) was applied twice: for pure gravitational evolution (YN = Yarkovsky not) and for evolution that consider Yarkovsky effect (Y = Yarkovsky yes). Comparison of the initial and final properties of the full set of VFMs has been done: drift of each of orbital elements was calculated; the number of asteroids that were lost from the family was found. The results YN vs. Y and the results forward vs. backward evolution are illustrate on the graphs.ReferencesASTDyS catalogue, updated 2015, hamilton.dm.unipi.it/astdys/index.php, M. 2006. Yarkovsky effect and the dynamics of Solar system. Ph.D. Thesis, sirrah.troja.mff.cuni.cz/mira/mp/Lowell catalogue, 2015. ftp://ftp.lowell.edu/pub/elgb/astorb.html The Asteroid Orbital Elements Database.Nesvorný, D., 2012, Nesvorny HCM Asteroid Families V2.0. EAR-A-VARGBDET-5-NESVORNYFAM-V2.0. NASA Planetary Data System.Wlodarczyk I., Leliwa-Kopystynski, J. 2018. BlgAJ, 28, 79-94.
Atlas of new and revised high-resolution spectroscopy of six CO isotopologues from 101 to 115 nm (B 1?+, C 1?+ and E 1? states) J.L. Lemaire, A.N. Heays, M. Eidelsberg, L. Gavilan, G. Stark, S.R. Federman, J.R. Lyons, and N. de Oliveira
LEMAIRE, Jean Louis
Since the pioneering work of Deslandres, 130 years ago (CR Académie des Sciences, 106, 842, 1888), our knowledge of the CO molecule still remains incomplete despite the numerous works of many generations of researchers both experimentalists and theoreticians.CO spectroscopy is particularly relevant to astrophysics where our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observed spectra. The recent and future improvements of UV space instrumentation, both in sensitivity and resolution, require increasingly detailed laboratory data. At the SOLEIL Synchrotron facility (Orsay), a worldwide unique Fourier-transform spectrometer installed on the DESIRS beamline provides a resolving power up to 106@10 eV from 5 to 30 eV. This is ideal for highly resolved spectroscopy in the VUV where many key electronic transitions of CO are found.As part of a long-term experimental campaign, first started at super-ACO (SOLEIL’s precursor), a French-American team, have successfully acquired at SOLEIL gas phase absorption spectra of six CO isotopologues in the VUV. A spectral resolution up to 450000 enabled the analysis of individual line positions. In our last work we report new measurements on neighboring Rydberg states from 101 to 115 nm that could also be used as f-value calibrators, namely B 1S+, C 1S+ and E 1P. This range encompasses the electronic transitions: B(v'=0, 1, 2), C(v'=0, 1, 2, 3) and E(v'=0, 1, 2, 3) from X1S+(v"=0). Higher resolution laser-based measurements of CO from the literature are used to improve the absolute calibration and accuracy of our data. The overall uncertainty of the great majority of the line positions, presented as an atlas, is estimated to be 0.01 cm-1. In addition, some of the data derived from transition energies measurements (term values and molecular constants) are obtained for the first time and others are improvements on previous sparser or lower spectral resolution datasets.
Generalized Faraday rotation of the CMB polarized anisotropies by large scale structures
Lemarchand, Nadège
A cluster of galaxies is both a magnetized relativistic and non relativistic plasma. Thus, it acts as a birefringent medium for the light that goes through this kind of structures. In particular, CMB photons cross clusters of galaxies on their way to us. Depending on the relativistic nature or not of the free electrons in the plasma, the effect on the CMB polarization will be different. In the case of a cold plasma, the polarization plane is rotated after going through a cluster of galaxies (Faraday Rotation). On the contrary, when the plasma is relativistic, CMB photons experience Faraday Conversion which transfers linear polarization into circular polarization. I looked at a statistical study of this effect, by first focusing on predicting the angular power spectra of such effects due to clusters, using a line-of-sight approach and the halo model, implementing the cosmological principle for the statistics of the directions of the magnetic fields inside clusters. These effects are both sensitive to the cosmology through the mass function of the clusters and so parameters such as s8, and to the distribution of the magnetic field and electrons inside a cluster, and can be used as a probe both for cosmology and for clusters of galaxies. Then I looked at the consequences of these effects on the angular power spectra of the CMB polarized anisotropies: the Faraday rotation effect mixes the E and B modes (creating secondary B modes in addition to the primordial and lensing ones), whereas the Faraday conversion effect transfers E and B anisotropies into the V mode, creating circular polarization which has no primordial origin in the standard cosmological scenario. Finally, I will sketch how polarized CMB anisotropies can be used for reconstructing the Faraday rotation and conversion fields.
Bright-Red Stars in the Dwarf Irregular Galaxy Leo A
Lescinskaite, Alina
We have studied bright-red stars (i.e., stars that are brighter and redder than the tip of the red giant branch (TRGB) in the colour-magnitude diagram I vs. V – I) in the dwarf irregular galaxy Leo A using multicolour photometry data obtained with the Subaru, HST ACS, and Spitzer telescopes. We developed a reliable method to significantly reduce a number of contaminating foreground Milky Way stars, which allowed us to study a spatial distribution of the bright-red stars within the Leo A galaxy and compare it with the distribution of RGB stars. We demonstrated a possibility to distinguish between different types of bright-red stars solely by using multicolour photometry data.
Towards resolving the globular cluster problem in the Fornax dSph in LambdaCDM
Leung, Gigi
The presence of globular clusters (GCs) at large galactocentric distances in the Fornax dSph challenges our understanding of the dark matter distribution in dwarf galaxies. Suggested solutions to this problem either invoke a very large initial galactocentric distance for these GCs, or only aim to produce an orbital decay timescale larger than the Hubble time but not the final locations of the GCs. On the other hand, numerical simulations have shown a dynamical buoyancy effect in which GCs are pushed outwards in cored dark matter halos. Although this effect partially alleviates the problem, these numerical simulations provide neither an understanding of the physical origin of the buoyancy effect nor a quantitative constraint on the core size. Here, we present a semi-analytical treatment of dynamical friction that is able to reproduce the buoyancy effect found in N-body simulations. The essential ingredient to include is the effect of background (dark matter) particles that move faster than the infalling GCs, a component that has been neglected in previous works but is important for cored profiles. We constrain the initial locations of the GCs in the Fornax dSph based on pressure equilibrium between the GCs and a progenitor gas disk for this galaxy. To reproduce the observed locations of all the GCs in this galaxy, a dark matter core with a size of at least 4 times that predicted by ?CDM simulations of dwarf galaxies with baryonic feedback is required. A potential resolution to this disagreement may lie in a proper consideration of the past merger history of this galaxy.
NOC activities at Hong Kong
Leung, Kam Cheung
The poster present the NOC activities at Hong Kong
Dynamical evolution of near-Earth space objects with high area-to-mass ratio
Levkina, Polina
Objects in the near-Earth space can be conditionally divided into two groups: operating spacecrafts - there are currently about 2000 objects, and space debris - about 17000 objects, the size of which is more than 10 cm. As a rule, operating objects have compact dimensions, and their area-to-mass ratio is small. Therefore, orbit determination for such satellites is not a laborious task. On the other hand, space debris objects can have high area-to-mass ratio (HAMR), for example, 111 m2/kg. In this case, significant perturbations of the orbits arise, including radiation pressure. Such large values of AMR and uncontrolled triaxial rotation of the object lead to fluctuations in the rate of influence of the radiation pressure force with time, and, consequently, to unmodifiable errors, not allowing to determine the orbit of these objects with the necessary accuracy. Note that the orbital evolution of objects with HAMR is significantly different from objects with small AMR. Orbital motion modeling for objects with a large but constant AMR (sun-oriented objects) revealed that the amplitude of the inclination variations is proportional to the magnitude of the AMR value. These orbits also show significant periodic changes in eccentricity. Orbits of such objects eventually expand from the initial circular shape to highly elliptical. Our research showed that for objects of space debris with a constant area-to-mass ratio equal to 25 m2/kg, the eccentricity after 5 days increases from 0.001 to 0.005.This paper presents the results of orbital determination for objects with HAMR, using optical observations obtained at the peak Terskol observatory and Zvenigorod observatory of Instutute of Astronomy of the RAS and provides numerical modelof the object motion in near-Earth space.This research supported by grant of the President of the Russian Federation No. MK-6640.2018.2.
A Single Pulse Picture of the Crab Pulsar
Lewandowska, Natalia
In spite of more than 50 years of intensive studies, the mechanism responsible for the observed radio emission from fast rotating, highly magnetized neutron stars (commonly known as pulsars) remains not understood.The Crab pulsar is one of the early discovered pulsars, but remains also one of the most complex known. Its changing profile emission at lower and higher frequencies can currently not be explained by existing emission models. We observed the Crab pulsar with the Very Large Array in a frequency range from 2 to 6 GHz in phased array mode and present results of the corresponding polarimetric study.
Tracing the Transition from Atoms to Molecules in the ISM
Li, Di
The transition from atoms to molecules is a key step in star formation. The processes and results of this transition not only dominate the formation time scale of stars, but also could affect protostellar disk evolution. I report here new results based on two absorption techniques, namely, absorption against background quasars (e.g. Heiles & Troland 2003) and HI narrow self-absorption (HINSA; Li & Goldsmith 2003). Through analyzing HI/OH absorption and the corresponding CO emission, we revealed the OH excitation to follow an empirical log-normal distribution peaking around 3.4 K (Li et al. 2018). The closeness between the OH excitation temperature and the Galactic background (CMB+synchrotron) should explain the apparent weakness of OH emission, which was rarely mapped on larger scales nor found in other galaxies. As a simple hydride, however, OH is found to trace the total amount of H2 including the so-called dark molecular gas (DMG) in the intermediate extinction regime ( 0.2<av<2). oh="" has="" a="" tighter="" x-factor="" than="" co="" (xu="" &="" li="" 2016). ="" based="" on="" the="" hinsa="" technique,="" we="" were="" able="" to="" identify="" an="" isolated="" dark="" cloud,="" b227,="" currently="" undergoing="" h2="" formation.based="" dust,="" co,="" nh3,="" and="" hi, ="" b227="" was="" shown="" have="" higher="" hi="" abundance="" in="" outside="" ring="" lower="" core.="" such="" gradient="" enabled="" us="" obtain="" limit="" of="" 5="" million="" years="" its formation="" time="" scale.="" core,="" [hi]="" [h2]="" measured="" be="" 0.1%,="" orders="" magnitude="" usually="" assumed="" chemistry="" models="" for="" protoplanetary="" disks="" (e.g. walsh="" et="" al.="" 2015). ="" absorption="" techniques="" thus="" provide="" crucial="" constraints="" formation="" molecules="" universe,="" affecting="" both="" cosmological="" simulations="" (e.g. gnedin="" 2009)="" star-formation="" models.="" further="" facilities,="" ska="" particular,="" could="" comprehensive="" information="" ism,="" terms="" total="" gas="" content="" including="" dmg="" excitation,="" through="" absorption ="" measurements="" (mcclure-griffith="" 2015).<="" p="">
</av<2).></p>
The abundance distributions of [a/Fe] in the Galactic disk giants from the LAMOST DR4
Li, Ji
Disk is the main structural component of the Milky Way, but whether there are sub-structures such as the so-called thin- and thick- disks has always been a controversial issue. The LAMOST Spectroscopic Survey of the Galactic Anti-center (LSS-GAC) provide the largest and most complete sample stars to investigate the disk structure of the Galaxy. Using the Add Value Catalogue V2 of LSS-GAC, we investigate the abundance distribuations of [a/Fe] ratios in the R-z space for 775 091 disk giants from the LAMOST DR4. Our results show that the sample stars can be seperated into two chemical distinct populations the thin- and thick- disks with the a-low and a-high abundances, respectively. While the chemical seperated thin and thick disc components are overlaped considerably in spatial kinematics in solar neibourhood. Moreover, our results indicate the Galactic disk is edge thickening both for the thin- and thick- disks.
Dust trapping and coagulation in protoplanetary disks
Li, Yaping
Grain growth from the submircro-size, typical size of dust from the ISM, to millimeter (mm) and centimeter sizes is the first step toward the formation of planet inside protoplanetary disks (PPDs). However, such process is still poorly understood because of the complex dust/gas dynamical process in disks. In this work, we carry out two-fluid (gas+dust) hydrodynamical simulations to study the dust coagulation processes in PPDs. By a systematic comparison with the continuum emission at several mm bands from ALMA observations, we find that ringed structures are predicated in the unresolved disks for those with mm spectral indexes as low as 2. With the help of ringed structures to slow down the dust radial drift and speed up the dust growth, both a high fragmentation velocity and a high dust surface density can produce such a shallow spectral slope. Future high resolution ALMA observations of these low spectral index sources can be used to test the existence of the ringed structures in the inner region of the disk and to further constrain the fragmentation velocity, one key parameter of the dust coagulation model. The physical implications of the expected rings are briefly discussed in terms of the planet formation.
Overshooting beyond the convective cores of massive stars
Li, Yan
During the main sequence phase, massive stars develop central convective cores due to the central hydrogen burning. The development of convection is crucial for the evolution of massive stars, since it can bring hydrogen into the stellar center to be burnt. Overshooting beyond the convective core is then an important effect, as it can significantly enlarge the supply of nuclear fuel. On the other hand, the convective core usually becomes smaller and smaller during the main sequence evolution, leaving a chemical gradient region beyond the convective core. The semi-convection is assumed to develop in such a chemical gradient region, resulting in complicated partial mixing to modify the chemical profile that is crucial for the post-main-sequence evolution of massive stars._x005F We investigated the overshooting mixing beyond the convective core by use of the k-omega model of Li (2012) for massive stars. We found that the convective core is considerably enlarged by about 0.15Hp, which is in agreement with results of other works in the literature. In addition, we also found an additional convection shell in the chemical gradient zone, where the semi-convection is usually assumed to develop. We noticed that the inclusion of the core overshooting significantly increases the separation between the convective core and the convection shell, making the convection shell quite thin and situated around the outer edge of the chemical gradient region. This effect entirely suppresses the semi-convective mixing predicted previously just above the convective core. As a result, the semi-convection can only be present near the outer edge of the chemical gradient zone, and result in a quite limited mixing effect on the chemical profile.
Angular momentum regulated atomic gas fractions of galactic disks in clusters
Li, Jie
We investigate the relation between the angular momentum and the HI gas fraction fatm = 1.35MHI/M in galaxies in varying environments, by using data from the VIVA (VLA Imaging of Virgo in Atomic gas) survey and the EAGLE (Evolution and Assembly of GaLaxies and their Environments) simulation. Obreschkow et al.(2016) suggested that fatm only depends on a global stability parameter q = js/GM for isolated galaxies, where j is the specific angular momentum of the disk and s is HI velocity dispersion. We apply their stability solution to investigate HI deficiency in q - fatm plane. This novel approach of quantifying the HI deficiency enables us to confirm the mechanics (mainly stripping) responsible, as well as to propose a method for identifying stripped galaxies in the q - fatm plane. This method is confirmed using all large clusters in EAGLE.
Orbital Distribution of Infalling Subhalos
Li, Zhaozhou
We study the distribution of the orbital parameters of subhaloes when they rst enter the virial boundary of their hosts. We focus on the joint distribution of velocities and infall angles, and how they depend on halo mass, merger mass ratio, and redshift. We nd that the infall velocity of subhalos follows a universal distribution with no dependence on the halo mass or redshift, while the infall angle varies under di erent merger conditions. Subhaloes in massive host halos tend to follow more radial orbits then those in low-mass hosts though they have similar normalized kinematic energy distributions. This trend is nearly independent of redshift or cosmology if we use the density peak height as a proxy for halo mass. Additionally, at xed host halo mass, the massive subhaloes are more likely to move along the radial direction than the low-mass ones. This is consistent with the picture that massive structures are in dynamically colder environments than low-mass ones. We provide an accurate tting formula for the joint distribution of velocity and infall angle that can be used as the initial condition for the semi-analytic model of galaxy formation.
The estimation of the ratio of central eclipses - Based on probability theory
Li, Jian
The ratio of partial solar eclipse and central solar eclipse can be induced from the “eclipse limit”, but the ratio of the three types of central eclipses: annular, total and total-annular eclispe, can not be reached by the same way. We found that considering the distance of Earth-Moon and the distance of Earth-Sun (during central eclipses) as random variables, it’s easy to find the proximate ratio of the central eclipses through the probability theory.By constructing the probability density function of the random variables, we calculate that the ratio of annular, total-annular and total eclispe (to central eclipses) is respectively 58.1%, 10.5% and 31.4%, which is consisted with the statistical result from AD 1001 to AD 2000 given by NASA in the rough: 49.5%(annular), 10.7%(total-annular) and 39.8%(total). It showes that the probability method maybe a relatively simple way to let the public know more about why there are more annular solar eclipses, fewer total solar eclpses and much fewer total-annular solar eclipses.
Measuring open clusters with photometric data by mixture model
Li, Lu
We established the mixture model for photometric data of open clusters. In the color-magnitude diagram, the number density distribution is a mixture of two components, cluster members and field stars. The cluster members are supposed to follow the distribution of the isochrone of a single stellar population. The field stars have a more complicated distribution which is the combination of various stellar populations, but it could be well constrained by using the field stars near the cluster region. Then, the properties of the cluster, such as age, metallicity, distance and dust extinction etc., can be fitted simultaneously. We validate this method on a broad set of over 400 synthetic clusters with varying degrees of field star contamination, and derived more accurate results than previous works. For a typical cluster, the uncertainties are only ~0.04 dex for age, 0.08 dex for metallicity and 0.03 dex for distance. Also, the mixture model method can be exquisite ways to determine the mass function of cluster members, and to detect the binary components in a stellar cluster. Our fitting algorithm utilizes a Nested Sampling technique, so it is easy to calculate the Bayesian evidence, which can be used to discuss the selection models of the stellar population.
Introduction to AMATEUR ASTRONOMER magazine-the most popular astronomical magazine of China
Li, Jian
Founded in 1958, by the head of the China Association for Science and Technology, and operated by the Chinese Astronomical Society and Beijing Planetarium, AMATEUR ASTRONOMER is China's earliest and most influential astronomical journal for public.AMATEUR ASTRONOMER tracks astronomical hot spots, introduces basic knowledge of astronomy, forecasts astronomical phenomena and etc. The special columns include "Frontiers·Viewpoint", "Staring The Sky", "Astronomical Gossip", "Astronomy Olympics". Since founded, It has been issued more than 13 million copies, and is popular with young readers. Nowadays, many of them have been professional astronomers and turned to become enthusiasm authors . The magazines also host the annual Star Party of China, which initiated in 2005 and more than 200 people attended per year. In 2015, AMATEUR ASTRONOMER awarded for the "National Popular Science Education Base" (2015-2019).
In-orbit performance and calibration status of Insight-HXMT
Li, Xiaobo
As China’s first X-ray astronomical satellite, Insight-HXMT successfully launched on Jun 15, 2017. It carries three main payloads onboard: the High Energy X-ray telescope (HE,20-250keV, NaI(Tl)), the Medium Energy X-ray telescope(ME,5-30keV, SiPin) and the Low Energy X-ray telescope(LE,1-15keV, SCD). The response of the three payloads can be divided into three parts: the response of the collimators, the effective areas and the redistribution matrix file. On ground, we have used the x-ray double crystal monochromator and radioactive sources to calibrate the detectors and also supplemented by the Geant4 simulation to get all the responses. In orbit, we have also used the radioactive sources, activated lines, the fluorescence lines, CasA, Crab and other celestial sources to verify the change of the performance compared to the ground. We found that deliquescence of NaI on ground made the energy resolution bad. Although the resolution can be better and better in orbit in first three months but also worse than the ground calibation phase. We recalibrate the energy solution and EC relation in orbit and also update the RMF and ARF file for HE instruments._x005F For ME and LE, we found that the energy resolution are almost same with ground. The response of the collimators have already calibrated using the small area scan to Crab. The effective areas will also adjusted by the observation of Crab. The EC relation has verified through the Ag line of ME and we think that the EC for ME is almost with the measurements on ground. But for LE, we have used CasA to verify that its EC has changed with the measurements on ground. We also update the EC relation of LE instruments.
Possible Contribution of the Lyman-alpha Solar Telescope to Studying our Sun
Li, Hui
As the most intensive line in Ultraviolet (UV) solar spectrum, the larger relative brightness of the Lyman-alpha line with respect to the visible waveband in the corona leads to less stringent requirement for the stray light suppression and make it suitable to detect faint features. In addition, the wide temperature coverage of the line allows us to access both low- and high-temperature features on the Sun, such as filaments (prominences), jets, loops, coronal holes, coronal mass ejections (CMEs), flares, etc. Due to its unique advantages, we selects the Lyman-alpha as the main observation wavebands of the Lyman-alpha Solar Telescope (LST), which is one of the three payloads proposed for the Advanced Space-based Solar Observatory (ASO-S) that is now in phase B study. The LST payload consists of three instruments and is aiming at observing the Sun from disk center up to 2.5 solar radii in both the Lyman-alpha line and white-light with high tempo-spatial resolution. In this talk, I will review solar observations with the Lyman-alpha line done by various satellites and sounding rockets, such as OSO, TRACE, SOHO, IRIS, VAULT, etc. and outline the possible LST contributions to study of the Sun.
HD 74050: A Delta Scuti Variable in the Praesepe Cluster
Li, Zhiping
The 77 hr of usable time-series over twelve nights photometric V-filter data were acquired for HD 74050, and it's Delta Scuti variability are confirmed by the light curve. Amplitude spectra indicate multiperiodic pulsation behavior, and two main pulsation frequencies, f1 = 18.8714 and f2 = 19.1450 cycles day-1, have been confidently identified. Three other frequencies, f3= 17.6205, f4 = 16.3291 , and f5=22.2880 cycles day-1, were suggested as the candidates with a relatively low possibility. Pulsation constant values of the five modes are distributed in the range from H to p3 mode.
Stellar and AGN feedback in isolated early-type galaxies: the role in regulating star formation and ISM properties
Li, Yaping
Understanding how galaxies maintain the inefficiency of star formation with physically self-consistent models is a central problem for galaxy evolution. Although numerous theoretical models by invoking different feedback processes have been proposed in recent decades, the debate still exists. By means of high-resolution two-dimensional hydrodynamical simulations, we study the three feedback (the thermalization of winds from AGBs, red giants, planetary nebula phases, SNe feedback, and AGN feedback) effects in suppressing star formation activities on the cosmological evolution of early-type galaxies with different stellar masses. AGN feedback models are updated based on Yuan et al.'s recent work. The availability of gas sources for star formation comes exclusively from the mass losses of dying low-mass stars for most of our models. We find that SNe feedback can keep star formation at a significantly low level for low mass galaxies for a cosmological evolution time. For the high mass elliptical galaxies, AGN feedback can efficiently offset the radiative cooling and thus plays a dominate role in regulating the star formation activities. Such a suppression of star formation is extremely efficient in the inner region of the galaxies. As expected, AGB heating cannot balance the cooling losses in the whole galaxies and hence cannot account for the suppression for both cases. The hot plasma X-ray temperature $T_{\rm X}$ can be in agreement with the observed data with the inclusion of effective feedback processes. We further find that X-ray luminosity $L_{\rm X}$ for the hot gas in our effective feedback models is consistent with the observed values. These results thus suggest that we can use $T_{\rm X}$ and $L_{\rm X}$ to probe the role of different feedback processes. The inclusion of additional gas sources can make the mass scale between SNe and AGN feedback dominating in suppressing star formation decrease to an observationally inferred value of a few $10^{10}~M_{\odot}$.
The local properties of supernovae explosion and their host galaxies
Liang, Yanchun
To understand the local properties of supernova explosion, and to compare those with the global properties of the host galaxies, we analyze the integral field spectragraph (IFS) of Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) for a sample of 11 SNe host galaxies selected from MaNGA-MPL4 and Asiago supernova catalogue. We obtained the 2D maps and gradients of the Ha velocity field , oxygen abundace , surface stellar mass density, specific star formation rate and star formation rate density, mean stellar population age etc. for the sample galaxies. These properties are analyzed for the individual object. We also try to obtain a general idea for the sample. For example, the differences between local and global gas-phase oxygen abundance of SNe Ia hosts cover a wider range than that of SNe II hosts. An extended sample up to 50 from MPL6 is under analyzed to get more statistical properties.
Galaxy Disc Central Surface Brightness Distribution in the Optical and NIR Bands
Liang, Yanchun
We aim to study the disc central surface brightness (µ0 ) distribution of 708 late-typegalaxies within 57 Mpc in optical griz bands and near-infrared Y JHK bands. Thesample is larger than the samples of previous studies.We obtain very strong evidence of double Gaussian fitting being better than singleGaussian fitting for µ 0 distribution of our sample in J band. To avoid the incorrectinclination correction, highly inclined galaxies with axial ratio b/a = 0.35(inclination greater than ˜ 73o ) are cut off. Double Gaussian fitting of the µ0distribution for galaxies with b/a = 0.35 is still better in J band. For galaxies insideVirgo Cluster, single Gaussian fitting is better in J band, which may be not reliabledue to the small sample size. For galaxies outside Virgo Cluster, the evidence ofdouble Gaussian fitting being better for µ0 distribution is still very strong in J band.The morphology of galaxies are also classified into two subsamples, subsampleone with fracDevr_ 0.1 and subsample two with fracDev_r = 0.1. Single Gaussianfitting of the µ0 distribution for galaxies with small and large portion of bulge isbetter in J band. For the total sample, we repeat 1000 times simulations and it turnsout that the percentage of double Gaussian fitting being better than single Gaussianfitting for µ0 distributions in J band is much higher than in other bands, which refutesthe hypothesis that the result could be caused by the statistical fluctuations.Therefore, the reason of double Gaussian fitting being better than single Gaussianfitting for µ0 distribution in J band may be morphology and scalelength of samplegalaxies, rather than inclination and environment of galaxies.
Astrometric radial velocities from Gaia DR2 astrometric data
Liao, Shilong
High accuray astrometric data such as Gaia DR2 allow us to determine the line of sight velocities. We use the maximum-likelihood formulation to estimate the space velocity in moving clusters with the Gaia DR2 high accuracy astrometric data only. And then we compare the results with the spectroscopy results. The astrometric radial velocities are obtained with a RMS of about 0.50 km/s for the center of the cluster.
Using Gaia DR2 astrometric data to identify QSOs
Liao, Shilong
QSOs are essential objects for astrometry, especially in building the celestial reference frame. Besides, QSOs are perfect nature objects to detect parallax and proper bias in astrometry mission such as Gaia because QSOs present no significant parallax. The non-detectable proper motion is a basic characteristic of quasars; therefore, an astrometric selection criterion based on near-zero proper motion can increase the purity of quasars in the mid-infrared color selected sample, as the latter is inevitably contaminated by false detections. Here we try to use the Gaia DR2 astrometric data and combine with the WISE data to select the largest sample of QSO candinates. This will be very useful in Gaia mission and related scientific research.
A compilation of known QSOs for the Gaia mission
LIAO, Shilong
Quasars are essential for astrometric in the sense that they are spatial stationary because of their large distance from the Sun. The European Space Agency (ESA) space astrometric satellite Gaia is scanning the whole sky with unprecedented accuracy up to a few µas level. However, Gaia’s two fields of view observations strategy may introduce a parallax bias in the Gaia catalog. Since it presents no significant parallax, quasar is perfect nature object to detect such bias. More importantly, quasars can be used to construct a Celestial Reference Frame in the optical wavelengths in Gaia mission. In this paper, we compile the most reliable quasars existing in literatures. The final compilation (designated as Known Quasars Catalog for Gaia mission, KQCG) contains 1843850 objects, among of them, 779349 objects are found in Gaia DR2 after cross-identifications. This catalog will be very useful in Gaia mission.
Local galactic kinematics from Gaia DR2 proper motions
Liao, Shilong
The stellar velocity field within 500pc of the solar system is investigated from the Gaia DR2 proper motions. The motion of the Sun with respect to the Local Standard of Rest is studied, the relative velocity field is modified in the frame work of the Milne-Ogorodnikov model, leading to eight parameters charcterizing the flow, including the Oort Constants. I use the data from Gaia DR2 and also the radial velocity information to determine the Oort Constants: A=14.7+-0.3km/s/kpc. B=-11.5+-0.4km/s/kpc, C=-3.5+-0.2km/s/kpc and K= -3.1+-0.5km/s/kpc.
Dwarf Galaxies and the cosmic web
Libeskind, Noam
It has been known since the 80s that environment plays a crucial role on the formation and evolution of galaxies. But how does environment affect the formation of satellite and dwarf galaxies? How are the dwarfs in the immediate neighbourhood of the Milky Way shaped by our unique local Universe? In order to address the issue of environment in the local area we must accomplish two important things: 1. We must first properly quantify and map the local cosmography and 2. we must attempt to understand how, via numerical simulation, this unique structure has affected the formation and evolution of galaxies within it. Constrained simulations are used for this purpose. In my talk I will explain how the local cosomgraphy has impacted outstanding problems, such as the existence of long flat planes of satellite galaxies around the Milky Way, Andormeda and Centaurus A. I will also present the HESTIA project - High-resolution Environometal Simulations of The Immediate Area - constrained gas dynamical simulations of the Local Group and its dwarfs.
State-of-the-art Hubble Space Telescope PROper MOtion (HSTPROMO) catalog of Galactic globular clusters. New insights and results.
Libralato, Mattia
With the advent of Gaia, astrometry is experiencing a new Renaissance. Although the Gaia mission will make important breakthroughs in different scientific topics, stars in crowded fields and at the faint end of the color-magnitude diagrams are and will be out of Gaia's reach, leaving again Hubble Space Telescope (HST) observations the unique way to obtain high-precision astrometric measurements for these stars.I present the continuation of the HST-based proper-motion analysis of Galactic globular clusters started in 2014, characterized by significant improvements in many aspects of the data reduction. As a benchmark of the state-of-the-art astrometry and photometry achieved with the HST data, I performed an all-around analysis of the globular cluster NGC 362. I studied the cluster’s internal kinematics and that of its multiple stellar populations. Furthermore, I investigated whether this cluster rotates in the plane of the sky and its absolute proper motion.
Analysis of Dawn Framing Camera images of Ceres in preparation for OSIRIS-REx encounter with Bennu.
Licandro, Javier
The IAC Solar System group has been cooperating with NASA’s OSIRIS-REx mission since 2011. In 2015 we came to an agreement to be members of the Image Processing Working Group (IPWG) to perform two main tasks: produce and analyze the Color-ratio Maps and participate in the in-flight calibration of the cameras (OCAMS). Currently four members of our group are participating in the IPWG.OSIRIS-REx was launched in 2016 and will visit near-Earth asteroid Bennu. It will completely characterize this object during 2018-2019, take a sample of material from its surface, and bring it back to Earth for detailed study in 2023. Bennu is the most accesible primitive near-Earth asteroid and is also one of the Potentially Hazardous Asteroids most likely to collide with Earth. It is well established that primitive class (eliminar) asteroids are the parents of carbonaceous chondrite meteorites, those with the most primitive known composition. Their study is of cosmogonic and astrobiological interest due to their primitive nature and their content in water and complex organics.In preparation for the analysis of Bennu’s color-ratio maps we have been analyzing Dawn Framing Camera images of different regions of Ceres using a spectral clustering technique to search for regions with different spectrophotometric properties. We have also derived Ceres' global photometric parameters following Schroder et al. (2017). In this talk we present our preliminary results on the clustering analysis of Ceres images and the derived global photometric models. We finally discuss the potential of the application of these techniques to OSIRIS-REx/OCAMS images of Bennu in the framework of our contribution to the IPWG.
Sausage Oscillations in a Plasma Cylinder with a Surface Current
Lim, Daye
Linear sausage oscillations of a cylinder embedded in a plasma with an azimuthal magnetic field, created by a current on the surface of the cylinder, are studied. Such a plasma configuration could be applied to modelling flaring loops, and magnetic ropes in CME. The plasma is assumed to be cold everywhere. Dispersion relations demonstrate that the lowest radial harmonic of the sausage mode is in the trapped regime for all values of the parallel wave number. In the long-wavelength limit, phase and group speeds of this mode are equal to the Alfve ´n speed in the external medium. It makes the oscillation period to be determined by the ratio of the parallel wavelength, e.g. double the length of an oscillating loop, to the external Alfve ´n speed, allowing for its seismological estimations. The application of the results obtained to the interpretation of long-period (longer than 20-30 s) oscillations of emission intensity detected in solar coronal structure, gives reasonable estimations of the external Alfve ´n speed. Cutoff values of the parallel wavenumber for higher radial harmonics are determined analytically. Implications of this finding to the observational signatures of fast magnetoacoustic wave trains guided by the plasma non-uniformity are discussed.
Understanding the Origin of Nuclear Activity in Low-Power Radio Galaxies
Lin, Yen-Ting
Using large samples containing nearly 2300 active galaxies of low radio luminosity (1.4 GHz luminosity between 2x1023 and 3x1025 W/Hz, essentially low-excitation radio galaxies) at z<0.3, we present a self-contained analysis of the dependence of the nuclear radio activity on both intrinsic and extrinsic properties of galaxies, with the goal of identifying the best predictors of the nuclear radio activity. While confirming the established result that stellar mass must play a key role in the triggering of radio activities, we point out that for central, most massive galaxies, the radio activity also shows a strong dependence on halo mass, which is unlikely due to enhanced interaction rates in denser regions in massive, cluster-scale halos. We thus further investigate the effects of various properties of the intracluster medium (ICM) in massive clusters on the radio activities, employing two standard statistical tools, Principle Component Analysis and Logistic Regression. It is found that ICM entropy, local cooling time, and pressure are the most effective in predicting the radio activity, pointing to the accretion of gas cooling out of a hot atmosphere to be the likely origin in triggering such activities in galaxies residing in massive dark matter halos. Our analysis framework enables us to logically discern the mechanisms responsible for the radio activity separately for central and satellite galaxies.
Computing Models of M-type Host Stars and their Panchromatic Output
Linsky, Jeffrey
We have begun a program of computing state-of-the-art model atmospheres from the photospheres to the coronae of M stars that are the host stars of known exoplanets. For each model we are computing the emergent radiation at all wavelengths that are critical for assessing photochemistry and mass-loss from exoplanet atmospheres. In particular, we are computing the stellar extreme ultraviolet radiation that drives hydrodynamic mass loss from exoplanet atmospheres and is essential for determining whether an exoplanet is habitable. The model atmospheres are computed with the SSRPM radiative transfer/statistical equilibrium code developed by Dr. Juan Fontenla. The code solves for the non-LTE statistical equilibrium populations of 18,538 levels of 52 atomic and ion species and computes the radiation from all species (435,986 spectral lines) and about 20,000,000 spectral lines of 20 diatomic species. The first model computed in this program was for the modestly active M1.5 V star GJ 832 by Fontenla et al. (ApJ 830, 152 (2016)). We will_x005F report on a model for the more active M5 V star GJ 876 and compare this model and its emergent spectrum with GJ 832. In the future, we will compute and intercompare semi-empirical models and spectra for all of the stars observed with the HST MUSCLES Treasury Survey, the Mega-MUSCLES Treasury Survey, and additional stars including Proxima Cen and Trappist-1. This talk is dedicated to the memory of Dr. Juan Fontenla who passed away in January 2018. This multiyear theory program is supported by a grant from the Space Telescope Science Institute.
Educators onboard SOFIA – The hidden Universe enters the Classroom
Lischke-Weis, Antje
The German SOFIA Institute (DSI) offers the SOFIA German Ambassador Program (SGAP). This program is an exciting opportunity for educators to participate a one-week STEM training that includes a scientific overnight flight onboard SOFIA. SOFIA – the Stratospheric Observatory for Infrared Astronomy – is an airborne observatory, with a 2.7m telescope onboard a highly modified Boeing 747SP, developed and operated by the National Aeronautics and Space Administration (NASA) and the German Aerospace Center (DLR). Flying above more than 99% of the water vapor in the atmosphere, SOFIA can obtain infrared light to study e.g. the birth of stars, or the atmosphere of other planets. In preparation for the flight, the SGAP participants obtain a one-day workshop in Stuttgart including background information about the observatory, the telescope, and infrared astronomy. During the SOFIA flight week at NASA’s research facility in Palmdale, California, the educators participate a safety training, and get an insight into science conducted with SOFIA and SOFIA engineering skills. The intensive STEM experience helps to not only include modern science and engineering in the lessons but also motivates students with real-world experience. After a successful application, SGAP travel expenses are covered be project fund.
Probing asteroid families with precise photometry from robotic telescopes
Lister, Tim
Asteroid families are products of catastrophic collisions, and their properties are a very important input for modelling the physics which governs these phenomena and understanding the evolution of the early Solar System and potentially other exoplanetary systems. The use of new techniques for computing the proper elements of large number of asteroids and hierarchical clustering methods to identify new, and refine existing, families enables us to extract a great deal of information, in particular the ages of the formation of these collisional families.A drawback of these large samples is that the absolute magnitude, which is used to derive the diameter and age, is drawn from a very inhomogeneous source (the Minor Planet Center’s database) with typical scatter of greater than 0.25 mag. We have a conducted a pilot program to use the Las Cumbres Observatory (LCOGT) telescope network to obtain precise calibrated photometry of a subset of the Vesta asteroid family to provide better constraints on the age of this important dynamical family. The refined absolute magnitude will allow more accurate diameters and ages for the two major collisions that formed this family.The robotic telescopes of the LCOGT Network were used to obtain a homogeneous set of calibrated photometry for a subset (100 objects or ~1% of the total) of the Vesta family objects spanning a range in absolute magnitude, H. This made use of the flexible and robotic scheduling to observe this subset of objects over a range of phase angles throughout the 6 month semester to measure the phase curve behaviour and the G parameter, giving a much more robust determination of the absolute magnitude. The combination of the uniform cameras and filters within the LCOGT Network and the robotic scheduling and will allow a high quality set of asteroid magnitudes and diameters to be derived and a better determination of the age of an important asteroid family.
The First Homogeneous Catalogue of Ultra-Compact Dwarf Galaxies in the Virgo Cluster and Related Studies
Liu, Chengze
For many decades, it was widely believed that galaxies and star clusters were completely distinct populations. However, in the late 1990s, a new type of compact stellar system, Ultra-Compact Dwarf galaxies (UCDs), was discovered to have some properties that bridged the gap between compact, dwarf galaxies and globular clusters. More than 15 years after their discovery, the origin of UCDs remains surprisingly obscure. In this talk, based on NGVS data, we will report the first homogeneous catalogue of UCDs in Virgo cluster and provide evidence that tidal stripping of nucleated galaxies is probably the dominant process in the formation of UCDs._x005F We show how UCDs can be selected with high completeness using a combination of magnitude, half-light radii and location in the color-color diagrams. _x005F Most of UCDs are around the three largest galaxies in the Virgo cluster: M87, M49 and M60. Although these three galaxies have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ~ 3.5 and 7 times as many UCDs as M49 and M60, respectively. _x005F We show for the first time that the UCDs, like the globular clusters in most high-mass galaxies, show a bimodal distribution in color with ~80% of the UCDs belonging to the blue sub-population. _x005F We report the discovery of the most massive UCDs, M59-UCD3, in Virgo cluster. With an effective surface mass density of 9.4×1010 Msun/kpc2, it is the densest galaxy in the local universe discovered to date. _x005F We present evidence that UCDs in Virgo core may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from the center of Virgo cluster.
Gas Temperature Demography in the Magellanic Clouds
Liu, Boyang
A galaxy's star formation rate is partially determined by how quickly gas converts from diffuse atomic (HI) state to molecular (H2). This HI-H2 conversion is affected by the amount of metal in the gas and the strength of interstellar radiation fields. We have conducted an Australia Telescope Compact Array (ATCA) observation project that uses HI absorption to probe the HI-H2 conversion within disparate environments in two local laboratories: the nearby Large and Small Magellanic Clouds. This project will complement the ASKAP survey, GASKAP and help us understand the gas processes that lead to star formation and how these impact galaxy evolution throughout the Universe. Our project observed 48 sightlines in LMC and 31 in SMC with 6km configuration of ATCA telescope, which doubled the total number of sampling. By Jan 2018 we have completed all the ~850 hours observation and derived the preliminary results for the temperature distribution of atomic gas in the Magellanic Clouds. We'll show the results and its implications for our knowledge of ISM evolution and galaxy formation.
The interaction of core-collapse supernova ejecta with a companion star
Liu, Zhengwei
The progenitors of many core-collapse supernovae (CCSNe) are expected to be in binary systems. After the SN explosion in a binary, the companion star may suffer from mass stripping and be shock heated as a result of the impact of the SN ejecta. If the binary system is disrupted by the SN explosion, the companion star is ejected as a runaway star, and in some cases as a hypervelocity star. By performing a series of three-dimensional (3D) hydrodynamical simulations of the collision of SN ejecta with the companion star, we investigate how CCSN explosions affect their binary companion. For main-sequence (MS) companion stars, we find that at most 10% of their mass is lost and their resulting impact velocities are less than 100 km/s. The amount of removed stellar mass, the resulting impact velocity, and the chemical contamination of the companion that results from the impact of the SN ejecta strongly increases with decreasing binary separation and increasing explosion energy. Their relationship can be approximately fitted by power laws. Also, we find that the impact velocity is sensitive to the momentum profile of the outer SN ejecta and, in fact, may decrease with increasing ejecta mass, depending on the modeling of the ejecta. Because most companion stars to Type Ib/c CCSNe are in their MS phase at the moment of the explosion, combined with the strongly decaying impact effects with increasing binary separation, we argue that the majority of these SNe lead to inefficient mass stripping and shock heating of the companion star following the impact of the ejecta, causing that the long-term post-explosion evolution of the compaion star is in general not dramatic.
Multi-color observation of active comets
Liu, Jinzhong
In general, due to a high temperature and a presence of gas sublimation leading to coma emitting, a comet is supposed to be active when it is close to the Sun. We start to investigate photometric information from some special active comets. The data were obtained with the 1-m wide field optical telescope at Nanshan Observatory in Xinjiang. This project is beginning from 2017. By multi-color observation and cometary morphological studies, we will estimate the surface brightness profiles, Af? parameters, mass production rates, the sizes of nuclei radii and coma colors. Meanwhile the physical driving mechanism of activity in comets is needed to be discussed.
TeachForAstro: A Chinese Practice of Astronomy Ambassadors' Concept
Liu, Boyang
TeachForAstro is an NGO founded by the author in 2014, as a Chinese version of the Astronomy Ambassadors Programme of AAS. It aims at connecting astronomers with curious young minds in local schools and supporting the astronomy teachers behind them. During the past 4 years, it has developed over 50 partner schools in Beijing, China, making it one of the largest astronomy education organization in China by far.TeachForAstro has also devoted a lot of efforts in Western China in collaboration with other education NGOs, as well as developed collaborations with institutes in the US and Australia, in order to narrow the astronomy education resource gap laid between developing and the developed regions. With the recent development of Chinese Astronomy, now TeachForAstro is seeking for wider connections with the world to better serve the communities both domestic and abroad.
Protection of Ali Observatory and its surrounding potential site
Liu, Liyong
The Ali Observatory is located in western China, where a group of telescopes were built and operated for Ground-to-satellite quantum teleportation, and a millimeter-wave telescope for CMB observations was under construction with Sino-U.S. Cooperation. The current site monitor results imply it is one of the world excellent infrared and sub-mm sites, and the SCIENCE journal has reported the Ali site in Sept. 2012 as a world-class observatory rising on ’Roof of the World’. The area around the Observatory is one of candidate sites of the 12m extremely large optical telescope under review, which also is of potential interest for the installation of the large sub-millimeter wave telescope of Chinese in future.This report provides the effort to protect areas around Ali observatory. We have used an all sky camera to monitor and evaluate light pollution, although there is only one small town around the Observatory. Local government legislation has set up dark night protected areas, including the core area, the restricted area and the corresponding provisions, in order to control unwanted light and radio emissions at observatory sites. Educational and outreach activities also are organized, to assist in raising public awareness about the importance of preserving access to an unpolluted night sky for all mankind.
What if a black hole devours too much?
Liu, Jifeng
The formation of relativistic jets by an accreting compact object is one of the fundamental mysteries of astrophysics. While the theory is poorly understood, observations of relativistic jets from systems known as microquasars have led to a well-established phenomenology. Relativistic jets are not expected from sources with soft or supersoft X-ray spectra, although two such systems are known to produce relatively low-velocity bipolar outflows. Here we report optical spectra of an ultraluminous supersoft X-ray source (ULS) in the nearby galaxy M81 (M81 ULS-1) showing blueshifted broad Ha emission lines, characteristic of baryonic jets with relativistic speeds. The time variable jets have projected velocities ~17 per cent of the speed of light, and seem similar to those in the prototype microquasar SS 433. Such relativistic jets are not expected to be launched from white dwarfs, but an origin from a black hole or neutron star in M81 ULS-1 is hard to reconcile with its constant soft X-rays. The completely unexpected presence of relativistic jets in a ULS challenges the canonical theories for jet formation, but can be explained by a long speculated super-critically accreting black hole with optically thick outflows.
A new interpretation of glitch events in high magnetic pulsars
Liu, Mengxu
Many pulsars exhibit sudden increases in their rotation frequency ?, which are known as glitches. For the lack of the radiative changes associated with glitches in nearly all rotation-powered pulsars, the origin of such events have been attributed to the stellar interior. However, glitches in some high magnetic field pulsars and magnetars which are frequently accompanied with profile and flux changes, may indicate an external origin. Radiation change associating with several glitch events for two high magnetic field pulsars and five magnetars are investigated. These pulsars have very similar radiation phenomena observed near epochs of glitches. A new mechanism originating from the magnetospheric activities is proposed, which confronts with both radiation change and timing property in glitch events.
Cosmological constraints from high-SNR weak lensing peak statistics using KiDS-450
Liu, Xiangkun
Emerged as one of the important probes in cosmological studies, weak lensing (WL) peak statistics is an efficient way to probe the nonlinear regime of the structure formation, and thus can provide important complements to the cosmic shear two-point correlation analysis. In this talk, I will report our latest cosmological results with high-SNR WL peak statistics using ~450 deg2 of imaging data from the Kilo Degree Survey (KiDS-450) . Accounting for different systematics, particularly for the boost factor and the effect of baryons on the mass-concentration relation of dark matter haloes, we derive the cosmological constraints on (Om, s8) and find a slightly flatter degeneracy direction compared with the cosmic shear analyses, which indicates that combining cosmic shear with peak statistics has the potential to break the degeneracy in Om and s8. Our results are consistent with the cosmic shear tomographic correlation analysis of the same data set and ~2s lower than the Planck 2016 results. More thorough studies on different systematic effects should be performed to understand the origin of this discrepancy.
CANDELS: From Outside-in to Inside-out Quenching of Galaxies at Intermediate Redshift
Liu, Fengshan
We investigate the galaxy quenching process at intermediate redshift using a sample of $\sim4400$ galaxies with $M_{\ast} > 10^{9}M_{\odot}$ between redshift 0.5 and 1.0 in all five CANDELS fields. We divide this sample, using the integrated specific star formation rate (sSFR), into four sub-groups: star-forming galaxies (SFGs) above and below the ridge of the star-forming main sequence (SFMS), transition galaxies and quiescent galaxies.We study their $UVI$ ($U-V$ versus $V-I$) color gradients to infer their sSFR gradientsout to twice effective radii. We show that on average both star-forming and transition galaxies at all masses are not fully quenched at any radii, whereas quiescent galaxies are fully quenched at all radii. We find that at low masses ($M_{\ast} = 10^{9}-10^{10}M_{\odot}$) SFGs both above and below the SFMS ridge generally have flat sSFR profiles, whereas the transition galaxies at the same masses generally have sSFRs that are more suppressed in their outskirts. In contrast, at high masses ($M_{\ast} > 10^{10.5}M_{\odot}$), SFGs above and below the SFMS ridge and transition galaxies generally have varying degrees of more centrally-suppressed sSFRs relative to their outskirts. These findings indicate that at $z\sim~0.5-1.0$ the main galaxy quenching mode depends on its already formed stellar mass, exhibiting a transition from the outside-in at $M_{\ast} < 10^{10}M_{\odot}$ to the inside-out at $M_{\ast} > 10^{10.5}M_{\odot}$. In other words, our findings support that the internal processesdominate the quenching of massive galaxies, whereas the external processes dominate the quenching of low-mass galaxies.
The Belgian Repository of Fundamental Atomic Data and Stellar Spectra: Radial Velocity Standards for Hot Stars
Lobel, Alex
BRASS is an international research networking project for the development of a new public database at brass.sdf.org providing accurate fundamental atomic data and high-resolution benchmark spectra of hot and cool stars of BAFGK-types. We model the BRASS spectra observed with Mercator-HERMES and ESO-VLT-UVES using advanced radiative transfer spectrum calculations for testing the quality of published atomic line data available in online atomic databases. BRASS will also offer high-resolution optical HERMES spectra of hot radial velocity standard stars. We present a new method for measuring accurate radial velocity values of A- and B-type reference spectra that can show strong rotational line broadening. The BRASS hot RV standards are important for measuring and validation of ESA-Gaia radial velocities of millions of stars in the Galaxy. We develop statistical methods to search for constant radial velocity stars in Gaia Data Release 2 and in future data releases. The HERMES and theoretical spectra are interactively offered in BRASS. The combination of these datasets is a novel approach for its development, which will provide a universal reference for advanced stellar spectroscopic research. We present an overview of the BRASS Data Interface developments allowing online user interaction for the combined spectrum and atomic data display, line identification, and line equivalent width measurements.
Search for technetium and s-process elements in binary central stars of planetary nebulae
Löbling, Lisa
Low- and intermediate mass stars experience a phase of carbon enrichment and slow neutron-capture nucleosynthesis (s-process) on the AGB. One particularly interesting s-process element is the relatively short-lived (with a half-life of 211,000 years) technetium (Tc), whose presence in the atmosphere of a star is a clear indication that nucleosynthesis happened very recently. _x005F Analysing the element abundances, especially the enrichment of carbon and s-process elements not only in the hot evolved stars at the centre of planetary nebulae (CSPNe), which followed the AGB phase, help to derive constraints for the evolution of these CSPNe, i.e. the timescales of their formation. Doing so also in their companions if they are in a binary, provides information on the mass-transfer history and the post-common envelope evolution that led to the planetary nebula (PN)._x005F We present the study of the two PNe which were shown to harbour binary systems in their centres – in both cases the red giant companion is dominating in the visible. Using high-resolution spectra of these red giants, we analyse the presence of Tc and the abundances of carbon and s-process elements in their atmospheres – a clear sign of pollution by mass transfer from the former AGB-star – and compare the results to predictions from stellar models
Teaching Astronomy in Ghana
Löbling, Lisa
The European Southern Observatory Astronomy Research Training (ESO ART) is a newly established programme which will be conducted for the first time in Ghana in April 2018. In collaboration between ESO staff members and members of the Ghana Space Science and Technology Institute, ESO ART aims at providing undergraduate students from developing countries access to astronomy and at bringing them into contact with the global astrophysical community via mentoring. During the workshop in Ghana, the students will be taught by a group of ESO scientists basic analytical skills and knowledge to tackle open questions in modern astronomy. Proceeding from the workshop, students interested in pursuing astronomical research will have the opportunity to create the basis for future research projects._x005F In this talk we will summarize the experiences of the first ESO ART workshop, and discuss possible avenues for future collaborations
The virtual observatory service TheoSSA: Establishing a database of synthetic stellar flux standards - NLTE spectral analysis of the O-type subdwarf BD+28º4211
Löbling, Lisa
Spectrophotometric standard stars with accurate absolute fluxes are mandatory for the calibration of ultraviolet (UV) space telescopes like the International Ultraviolet Explorer (IUE), the Hubble Space Telescope (HST), or the Far Ultraviolet Space Explorer (FUSE). Such a star is BD+28º4211, a bright O-type subdwarf exhibiting a fairly simple spectrum. _x005F We present a detailed spectral analysis of high-resolution UV spectra obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the HST and with FUSE. Non-local thermodynamic equilibrium (NLTE) stellar model-atmosphere techniques based on the Tübingen Model Atmosphere Package (TMAP) are employed to determine fundamental photospheric parameters like effective temperature, surface gravity, and element abundances.
Weaving a Webb Story: Communicating Science for JWST
Lockwood, Alexandra
Humanity’s next flagship-class space observatory is a complex mission with many tales to tell. JWST (or Webb for public audiences) will be a centerpiece of 21st century science communications, with discoveries ranging from our solar system to the first galaxies. How are we preparing to share the scientific news to come from this telescope? From news releases to multimedia content to a vast online presence, the discoveries of the James Webb Space Telescope will appear in multiple places with a broad reach across multiple audiences. At the same time, Webb’s infrared observations present new challenges to inspiring the public and sharing the science. For example, Webb’s science results are likely to be dominated by many different, and complex, data types (e.g. IFUs, coronagraphy), including some that have never before been deployed in space (e.g. multi-object spectroscopy and aperture masking interferometry). It will be more difficult to capture the public eye with these than it has been with the beautiful visible images of Hubble, but preparing resources in advance is helping science communication professionals worldwide anticipate these challenges. Each science story will need to be carefully crafted in multiple formats to reach the widest audience possible while also providing sufficient detail to further public understanding. We discuss strategies for developing stories based on messaging, goals, mediums, and audience, and how you can apply the same principles to communicating your own research.
Inflow and Outflow meridional self-similar MHD models around Kerr hole
Loic, Chantry
The jets produced by AGN are extremely energetic natural phenomena and thus constitute a real laboratory of high energy physics. To describe the inner-spine jet of AGN in the context of ideal, stationary and axial-symetric MHD, we build a meridional self-similar model in Kerr metric. The choice of this metric is justified in order to describe the flow near the super-massive central black hole, and in particular to study the effects of its rotation. The model, characterized by 8 parameters, is based on a first order expansion of the governing general relativistic equations in the magnetic flux function around the symmetry axis of the system. Using the regularity conditions at the Alfvén transition surface, we introduced a parameter to take into account the light cylinder effects and the meridional increase of the Alfvén number with the magnetic flux function. This complete treatment for an outflow in a Kerr metric allowed us to present four enthalpy driven solutions with different field geometries and Lorentz factors, wherein the contribution of the Poynting flux is rather small. The jet power of the ultra-relativistic outflow solutions are of the same order as that determined from numerical simulations conducted by several groups.Furthermore, our model is able to describe both an incoming and outgoing flow at the level of the stagnation radius; at this radius, pairs are created from neutrinos or highly energetic photons coming from the disk. Coupling inflow and outflow models allows us to describe the MHD flow from the horizon of the black hole up to infinity. We can estimate the different contributions of each of those processes: at the black hole level the energetic component coming from the Blandford-Znajek effect or the generalized Penrose mechanism, and the energetic input due to the creation of pairs.
Growing up in a rougher neighbourhood: Star and planet formation/evolution in extreme environments
Longmore, Steven
Our understanding of star and planet formation is underpinned by observations of systems forming close to Earth at the present day. However, most stars in the Universe (including our own Sun) formed at earlier epochs of the Universe, when the properties of the interstellar medium were very different. Understanding how stars and planets form and evolve in gas with densities, temperatures, and pressures orders of magnitudes higher than in the local universe is therefore fundamental to linking formation theories to the observed (extrasolar) planet population. In our lifetime no observational facilities will have sufficient sensitivity and resolution to observe individual forming stars/planets at the epoch of peak star formation (z=1-2). However, the properties of gas in the inner few hundred parsecs of our Galaxy are remarkably similar to gas in galaxies at this epoch. At only a fraction of the distance to high redshift galaxies, the Galactic Centre molecular clouds therefore offer an ideal laboratory for understanding star and planet formation/evolution in more extreme environments. Over the last few years we have undertaken a systematic ALMA study to trace the gas in extreme Galactic Centre molecular clouds down to the size scales of individual forming stars and proto-planetary disks (<1000AU). I will summarise the results from these observations aiming to quantify the differences in star/planet formation and chemistry in this environment compared to that in nearby clouds.
Magnetic field constraints in the outskirts of galaxies
Lopez, Ericson
Based on CO(2-1) public data, we study the monoxide oxygen gas excitation conditions and the magnetic field strength of four spiral galaxies. For the galaxy outskirts, we found kinetic temperatures in the range of 35 - 38 K, CO column densities 10^15 - 10^16 cm^(-2), and H2 masses 4 x10^6 - 6 x 10^8 Ms. An H2 density 10^3 cm^(-3) is suitable to explain the 2 sigma upper limits of the CO(2-1) line intensity. We constrain the magnetic field strength for our sample of spiral galaxies and their outskirts by using their masses and H2 densities to evaluate a simplified magneto hydrodynamic equation. Our estimations provide values for the magnetic field strength in the order of 6-31 uG.
The astronomical heritage of the Quito Astronomical Observatory
Lopez, Ericson
The Quito Astronomical Observatory is one of the oldest observatories in America. This was founded in 1873 by the Ecuadorian President Gabriel García Moreno, as part of the national plan to promote and develop education, sience and technology, in those early days of the republican life of Ecuador. Nowadays, as the result of hard and dedicate work, the infraestructure of the Quito observatory looks in great conditions and fully operational. On the basis of the old instruments and equipments of the Quito Observatory heritage, the first astronomical museum has been established and it is open permanently open to the general public, since the summer of 2012. In this presentation wegive an overview of the history of astronomy in Ecuador and about the astronomical heritage of the Quito Astronomical Observatory.
The highly polarized 2-90 microns core of Cygnus A
Lopez Rodriguez, Enrique
Near- to mid-infrared (NIR, MIR ; 1-13 µm) total and polarized flux observations from the ground have been key to advance our understanding about the dust distribution and emission in the central few parsecs of active galactic nucleus (AGN), i.e. jets and dusty torus. Although 10 µm total flux observations of the identified thermal and non-thermal nuclear source of radio-quiet galaxies show low polarizations (<1%), the radio-loud Cygnus A galaxy shows a highly polarized, ~10%, core. The polarization is thought to arise from a synchrotron polarized pc-scale jet close to its core with a cut-off frequency at far-IR wavelengths (FIR). However, the atmosphere is opaque to the FIR wavelength range and observations are impossible from ground-based telescopes. Furthermore, polarimetric capabilities have been very limited in this wavelength range, which makes difficult to observationally constrain our previous findings. HAWC+ onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) has opened a new window to explore AGN, providing the best angular resolution and the unique polarimetric capability within the 50-250 um range.We here present 53 and 89 µm imaging polarimetric observations using HAWC+/SOFIA of Cygnus A. We have found a highly polarized core, ~10%, with a potential change in the polarization angle from 2 µm to 89 µm showing a shift of >50 degrees from the radio axis. Our preliminary analysis shows that a synchrotron polarized component explains acceptably well the polarized SED, however dust scattering from large grains can also be considered.
Far-infrared polarization of galaxies with SOFIA/HAWC+
Lopez Rodriguez, Enrique
Near- to mid-infrared (NIR, MIR; 1-13 µm) total and polarized flux observations from the ground have been key to advance our understanding about the emission and distribution of dust in galaxies as well as the morphology of their magnetic fields. However, the atmosphere is opaque to the 50-220 µm range and observations are impossible from ground-based telescopes. Furthermore, polarimetric capabilities have been very limited in this wavelength range. HAWC+ has opened a new window to explore active galactic nuclei (AGN) and starburst galaxies, providing the best angular resolution within the 40-300 µm range of the current suite of instruments.We here present the results of a massive spiral galaxy containing an AGN, NGC 1068, and a starburst galaxy, M82, observed at 53 µm and 89 µm with the far-IR (FIR) polarimeter HAWC+ onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Specifically, our polarization observations of NGC 1068 at 53 µm have shown for the first time a magnetized arm along the spiral inner arms of the galaxy. Our polarized flux observations of M82, in combination with previously published NIR polarimetric observations, have shown evidences of a galactic magnetic wind at scales of several hundred parsecs.
ANALYSIS OF THE PHYSICAL PROPERTIES OF JETS/OUTFLOWS IN T TAURI STARS
Lopez-Martinez, Fatima
Winds and jets are key factors in the evolution of accretion disks in pre-main sequence stars, and deriving their physical properties is one of the most important steps for a full understanding of the connection among outflow, jet and accretion processes. In this work we determine the physical properties of the high velocity component (HVC) and the low velocity component (LVC) emitting region of the optical forbidden [N II], [O I] and [S II] lines for the jets of DG Tau, SZ 102, CW Tau and RW Aur. We found two well defined ranges of temperatures and densities for the gas emission lines: one with 4.125 ≤ log T e (K) ≤ 4.55 and 2.25 ≤ log n e (cm^3 ) ≤ 5.25, and another one with_x005F 5.25 ≤ log T e (K) ≤ 5.6 and 5.25 ≤ log n e (cm 3 ) ≤ 6.75. The LVC has high temperatures and high densities for DG Tau and CW Tau, whereas for SZ 102 it has much lower densities and temperatures. The peak velocities and full width at half maximum of the LVC pointed out that its origin is from a MHD disk wind at 0.05-1.69 AU and that Keplerian rotation is the main responsible of the broadening of the lines. The relation found between the accretion luminosity with the LVC’s temperature and density, suggests that the accretion plays an important role in the physical properties of the emitting region, likely a steady accretion is performing in the outflow driving region. We did not find evidence of Keplerian broadening for the HVC, whereas we found a correlation between the mass loss rate and accretion luminosity, probably because episodic accretion is occurring in the region where the jet is driven.
Orbital Dynamics in Galaxy Clusters
Lotz, Marcel
The effect of galactic orbits on a galaxy's internal evolution within a galaxy cluster environment has been the focus of heated debate in recent years. To disentangle this relationship, we investigate the velocity anisotropy, phase space and the orbital evolution of cluster satellites. Through the use of the hydrodynamic cosmological Magneticum Pathfinder simulations, we evaluate the orbits of subhalos associated with clusters above a mass threshold of 1014 Msol from redshift z = 2 to z = 0.2. Through the inspection of different cluster masses and redshifts, we are able to achieve a diverse statistically relevant sample of subhalos inside clusters, which we further split into quiescent and star forming subhalos. This split allows us to observe the internal subhalo evolution and study its dependence on the velocity anisotropy parameter and the radial distance. To evaluate the validity of the simulation-based findings, we compare, where possible, with observations. We find that independent of mass and redshift, the star forming subhalo population experiences a continuous decrease in star formation at radii above the virial radius. More importantly, after crossing below the virial radius the vast majority of star forming subhalos are quenched through ram-pressure stripping during their first passage.
Properties of OH/IR stars versus YSOs in mid- and far-infrared surveys
Loup, Cecile
To disentangle very optically thick AGB stars and young stellar objects in infrared photometric surveys has always been a challenge. The typical double-peaked OH maser profile of OH/IR stars proves that they are AGB or post-AGB stars, while the detection of a CH3OH maser signs the presence of YSOs, independently of any infrared observation. About 2000 OH/IR stars and 500 YSOs with CH3OH maser emission have been identified in the AKARI-IRC/FIS, MSX6C, GLIMPSE, MIPSGAL, and Hi-Gal surveys. It is shown that OH/IR stars can be as red as YSOs in the mid-infrared, with m(8)-m(24) reaching 10. OH/IR stars and YSOs with m(8)-m(24) > 2.5 cannot be disentangle with mid-infrared observations only. On another hand, the combination of mid- and far-infrared observations allows to set up selection criteria to disentangle OH/IR stars and dusty YSOs. These criteria have been applied to the "intrinsically red sources in the galactic midplane" selected by Robitaille et al. (2008). It is shown that these "red sources" towards the galactic plane are mostly AGB stars rather than YSOs, with proportions of the order of 70% versus 30%, respectively.
A New Generation of AGN Feedback Models in Simulation of Galaxy Clusters
Lu, Yinghe
A better understanding of feedback effects due to the central AGN (active galactic nucleus) in galaxy clusters is important for addressing the cool-core problem, in which the cooling rate inferred from the observed luminosity predicts far more cool gas than X-ray spectroscopy reveals. Aiming to investigate the environment of galaxy cluster cores with AGN feedback via three-dimensional hydrodynamic simulations, we present a novel, more physical subgrid model whichincorporates the most recent theoretical improvements in accretion disk physics, including information from global accretion disk simulations, jet-environment interaction, and radiative cooling. We will discuss results from a series of kiloparsec-scale simulations of galaxy cluster cores and observations that are used to calibrate the model. The studyprovides a clearer image of the detailed interplay between the supermassive black holes (SMBHs) at the centers of galaxy clusters and the surrounding gas, and offers insights into the physics of the SMBHs and the interstellar medium of cluster central galaxies.
Methods to increase the audiences, promote Citizen Science projects, and include women and underserved groups in astronomy outreach programs
lubowich, donald
I created programs can be adapted for different cultures. My NASA-funded Music and Astronomy program at 70 free/low-cost outdoor concerts, festivals, fairs was assisted by 15 amateur astronomy clubs (60,000 people; 50% families; 65% female; 20% seniors; targets underserved by type of music and location). There were telescopes, hands-on activities, posters/banners, information about science museums, and hands-on citizen science projects. Yo-Yo-Ma, the Chicago or Boston Symphony Orchestras, Ravi Coltrane, Phish, Blood Sweat and Tears, Deep Purple, James Taylor, and Wilco performed at some events. Astronomy Festival on the National Mall (co-sponsored by the White House, 2010) had the participation of astronomy clubs, universities, museums, and scientific institutions (AAAS, AAS, AGU, APS, Carnegie Science, Chandra, NASA, NASM, NOAO, NRAO, NSF, STScI, USNO; 30,000 people, 8000/year; largest in the US). Astronomy for very ill/severely injured children (undergoing surgery, chemotherapy, medical treatment) and their families (low-income/poverty-level; minority) at Ronald McDonald Houses (350; 80 countries, 250 in the US) and hospitals (NASA & IAU funded). RMH charities give free/low-cost lodging for the children and their families (50% low-income/poverty-level; 50% African-American or Hispanic; 60% are female in US). I trained their staff so the program can be sustained without an astronomer. My astronomy float in the 2009 NYC Columbus Day Parade honored Galileo and IYA2009 with telescopes, “Galileo” and an “astronaut”. Seen by hundreds of thousands and on TV, (many families and females). Astronomy at summer camps for low-income/special needs children. Super Bowl Star Party (targeting females) can adapted to soccer matches at parties, parks, and stadiums. Halloween star party attracts girls in costume. Edible astronomy demos with chocolate chips, cookies, marshmallows, popcorn, candy (Starburst and Twizzlers), and bagels can be adapted for the blind and visually impaired.
Astronony Outreach for 100,000 People at Outdoor Concerts and the US National Mall
lubowich, donald
Bringing astronomy directly to the public is effective! I brought astronomy to the public at tourist sites and outdoor concerts where there are large crowds. In 2010 I created the Astronomy Festival on the National Mall (AFNM), co-sponsored by the White House Office of Science and Technology Policy. Ten astronomy clubs, universities (American, Catholic, George Mason, George Washington, Georgetown, Johns Hopkins, Penn State), scientific institutions (AAAS, AAS, AGU, APS, Carnegie Science, Chandra X-ray telescope, NASA, NASM, NOAO, NRAO, NRL, NSF, STScI, USNO), and an E-planetarium show on an 8m dome participated. The AFNM is now the largest single-day annual astronomy outreach event in the US with ~10,000 participants (30,000 since 2010). My $308,000 NASA-funded Music and Astronomy program (MAUS) reached 70,000 people at 70 free/low-cost outdoor concerts assisted by 15 amateur astronomy clubs. The audiences were 60% female; 50% families; 20% seniors; and targeted African-American and Latino audiences by the types of music. These were family learning experiences - often the first time kids and adult looked through a telescope. Yo-Yo-Ma, the Chicago or Boston Symphony Orchestras, Esperanza Spalding, Ravi Coltrane, Phish, Blood Sweat and Tears, Deep Purple, Tony Orlando, Debbie Boone, James Taylor, and Wilco performed at some events. MAUS and AFNM include solar, optical, and radio telescope observations; hands-on activities; an image projection system; large posters/banners; videos; edible demonstrations; and promoted science museums, membership in astronomy clubs, public science events, and Zooniverse citizen science projects. MAUS Evaluation: 96% of the participants all of ages, ethnicity, income, or interest in science found MAUS enjoyable and understandable; learned about astronomy; wanted to learn more; and increased their interest in science (average rating 3.35/4, 4 = strongly agree). The positive response was the same for all genders all types of music.
ARIEL - An ESA Space Mission to Focus on the Nature Of Exoplanets
Lueftinger, Theresa
ARIEL (Atmospheric Remote-sensing Exoplanet Large-survey) has recently been selected as the next medium-class science mission by the European Space Agency (ESA) due for launch in 2028. The goal of the ARIEL mission is to investigate the atmospheres of planets orbiting distant stars in order to address the fundamental questions on how planetary systems form and evolve and to investigate the composition of exoplanetary atmospheres.During its 4-year mission, ARIEL will observe 1000 exoplanets ranging from Jupiter- and Neptune-size down to super-Earth size, in a wide variety of environments, in the visible and the infrared. The main focus of the mission will be on warm and hot planets in orbits close to their star. Some of the planets may be in the habitable zones of their stars, however. The analysis of ARIEL spectra and photometric data will allow to extract the chemical fingerprints of gases and condensates in the planets’ atmospheres, including the elemental composition for the most favorable targets. The ARIEL mission has been developed by a consortium of more than 60 institutes from 15 ESA member state countries, including UK, France, Italy, Poland, Spain, the Netherlands, Belgium, Austria, Denmark, Ireland, Hungary, Sweden, Czech Republic, Germany, Portugal, with an additional contribution from NASA in the USA currently under study.
An Upper Mass Limit for a Black Hole in the Large Magellanic Cloud
Luetzgendorf, Nora
As one of our closest galactic neighbours, the center of the Large Magellanic Cloud (LMC) is an enticing place to look for a central black hole (BH). Due to the large size of the LMC on the sky and the complexity of its dynamics, the center of this dwarf galaxy is still only known to ~ 30 arcmin. Here we present a new study of the stellar kinematics near the center of the LMC, and use this to provide the first constraints on the possible presence of a central black hole. With the impressive field of view of the Multi Unit Spectroscopic Explorer (MUSE) for the Very Large Telescope this is the largest region of the LMC mapped with integrated light. We identify and subtract the galactic foreground population and use the Calcium Triplet (~ 850nm) spectral lines to create a 2D radial velocity map with an unprecedented spatial resolution of 1 arcmin2. Comparison of this map with kinematic models yields 3s upper-mass-limit of 107.1 M? for any black hole within the center of the LMC. Considering the poorly constrained scaling relations between BH masses and their host galaxies on the lower-mass end, the study of such a nearby dwarf galaxy and its potential black hole can shed light on many theories of BH formation, growth, and host system interaction. It is also still unknown what fraction of low-mass galaxies contain black holes, and the measurements remain difficult to achieve. This study is a promising step in searching for the kinematic signature of black holes in the elusive intermediate mass range and contributes to the growing understanding of the complex dynamics of the LMC’s central bar region.
POLICAN first results: Infrared Polarization of the Molecular Cloud Associated to IRAS18236-1205
Luna, Abraham
Using the new infrared image polarimeter POLICAN (Devaraj, R., Luna, A., Carrasco, L., et al. PASP 2018), at the Guillermo Haro Astrophysical Observatory in Cananea Sonora Mexico, we investigate the role of the magnetic fields in the process of star formation observed at the molecular cloud associated to the source IRAS18236-1205 (Retes, R., Mayya, Y.D., Luna, A., and Carrasco, L. Apj, 2017). Using the polarization field measured in H band in the molecular cloud, we obtained a strong correlation in the projected orientation with the observed molecular outflow at the IRAS central densest molecular region. Comparing the mean field projected polarization orientation in the cloud with the Milky Way Galactic plane field, there is a 20deg of deviation and the long axis for the filamentary molecular cloud is perpendicular to the outflow (Luna, A., Retes, R., Devaraj, R., et al. RMxAASC 2017). Using the Chandrasekhar-Fermi (CF) method we investigated the energy balance of the complete cloud. Column densities were estimated with the molecular component and confirmed with an approaching model using Herschel photometric data. Following these approach and using POLICAN instrument we are observing nearest molecular clouds like MonR2 and other regions at the Milky Way galactic plane (< 3kpc) to analyze their stability using the CF approximation. Results will be compared against theoretical models with strong and weak magnetic fields in molecular clouds with ongoing star formation (Zamora-Aviles, M., Vazquez-Semadeni. E., et al 2018).
How HI eXtreme galaxies maintain their HI content
Lutz, Katharina
The HIX galaxy survey investigates how the most HI eXtreme galaxies in the Southern Hemisphere maintain their HI reservoir. HIX galaxies were selected from the HIPASS HI-blind survey to contain at least 2.5 times more HI than expected from their optical luminosity.Making use of spatially resolved observations of their HI content as well as imaging and photometry in the ultraviolet and infrared, we find that HIX galaxies form stars less efficient than galaxies with an average HI content for their optical luminosity. A detailed HI kinematic analysis reveals this to be due to a high HI specific angular momentum, which stabilises the HI disc against star formation and keeps HI at large radii, where it is unavailable for star formation.A comparison to galaxies modelled with the semi-analytic model DARK SAGE shows that HIX-like, modelled galaxies tend to reside in dark matter haloes with higher than average spin and thus inherit the high HI specific angular momentum from their dark matter halo.
Metallicity gradients in xGASS/xCOLDGASS galaxies
Lutz, Katharina
The xGASS and xCOLDGASS surveys observed 1179 and 538 local galaxies from the SDSS/GALEX overlap in HI and CO, respectively. Galaxies have been observed with the Arecibo Dish/the IRAM 30m single dish until HI / CO were detected or a detection limit was reached. Thus mass-selected samples, representative of the local galaxy population, have been obtained.We present a study of the gas-phase oxygen abundance gradients of 129 star forming galaxies from the xGASS / xCOLDGASS samples for which optical long-slit spectra have been obtained. We find correlations between the gas-phase metallicity gradients and stellar mass surface density (as a proxy for morphology), stellar mass, and HI mass fraction. Furthermore, we find that the metallicity at the outskirts of the stellar discs is correlated with the global HI mass fraction.These findings suggest that metallicity gradients and radial metallicity profiles are driven and shaped by an equilibrium between gas-inflow, outflow and star formation.
ZOOMING INTO THE COMPLEX DUSTY ENVELOPES OF C-RICH AGB STARS
Lykou, Foteini
Recent advances in high-angular resolution instruments (VLT and VLTI, ALMA) have enabled us to delve deep into the circumstellar envelopes of AGB stars from the optical to the sub-mm wavelengths, thus allowing us to study in detail the gas and dust formation zones (e.g., their geometry, chemistry and kinematics). I will be reporting on the most recent developments of our study of 15 evolved stars in the near-infrared at high-angular resolution. The focus of the presentation will be on four (4) C-rich AGB stars from the initial sample. I will be presenting our multi-wavelength tomographic studies of the dusty layers of the circumstellar envelopes of these C-rich stars, i.e. the variations in the morphology and temperature distribution of the dust w.r.t. different phases, as well as discuss any hints on binarity from the interferometric data (Lykou et al., to be submitted).
History of Astronomy and Archaeoastronomy: Education, Outreach and Heritage in Greece
Lyrintzis, Ioannis
The History of Astronomy and archaeoastronomy as a relatively new discipline in (some) higher education establishments offers new interdisciplinary approaches in coupling humanities and new technologies. In both theoretical and positive science departments the subject bridges two different fields but initiates students to the balanced approach of cultural education with an holistic attitude. Terminology, phenomena, physical sciences, as well as, documentation, promotion of new cultural assets those of astronomical heritage significance, are related to a) education (from primary to adult), b) social outreach (LLL), c) research (location, documentation), and d) marketing and employment sectors both essential elements of sustainable development in a local, regional and national level. The current status in Greece is overviewed (Examples: Pnyka, Tower of the Winds, orientations of Temples, mythology coupled to astronomy, ancient sources referring to astronomical phenomena).
The orbital damping effect on the inclination and eccentricity of Neptunian Trojans
MA, Yuehua
Trojan asteroids formation mechanisms are closely related to giant planet formation/migration. Using test particle simulations, we investigate the orbital element distributions of Neptune Trojans affected by the processes of planetary migration and the orbital damping of Uranus and Neptune. We examine the stability of primordial Neptune Trojans, objects that were initially Trojans with Neptune prior to migration, and also study Trans-Neptunian objects captured into resonance with Neptune and becoming Neptune Trojans during planet migration. We find that most primordial Neptune Trojans were unstable and lost if eccentricity and inclination damping took place during planetary migration. With damping, secular resonances with Neptune can increase a low eccentricity and inclination population of Trans-Neptunian objects increasing the probability that they are captured into 1:1 resonance with Neptune, becoming high inclination Neptune Trojans. We suggest that the resonant trapping scenario is a promising and more effective mechanism to explain the origin of Neptune Trojans if Uranus and Neptune had orbital damping during planetary migration.
INSIGHT-HXMT Observations Of The New X-ray Binaries: Swift J0243.6+6124 and MAXI J1820+070
Ma, Xiang
The Hard X-ray Modulation Telescope (HXMT), Insight-HXMT, the first Chinese X-ray astronomical satellite, consist of three slat-collimated instruments: the High Energy X-ray Telescope (HE), the Medium Energy X-ray Telescope (ME), and the Low Energy X-ray Telescope (LE). After launch, Insight-HXMT went through a series of performance verification tests where it observed blank sky, standard source and sources of scientific interest.In the past few months,Insight-HXMT observed some new X-ray transient source: Swift J0243.6+6124 and MAXI J1820+070 and so on. The total of observation time of Swift J0243.6+6124 and MAXI J1820+070 by Insight-HXMT are ~1200ks and ~610ks respectively. We perform timming analysis and spectral analysis on these two sources. In Swift J0243.6+6124, we find the evolution of pulse profile is vary rapidlly in timming analysis and existance broad iron line in continuum spectral fitting. In MAXI J1820 data analysis, we find the source exhibits Quasi-periodic oscillations (QPOs) in the intermediate states, which seem to be of different types. We'll present the energy dependence of the QPO amplitude up to 100 keV which was totally unexplored area in timing domain.
Mid-IR images of clumpy tori in AGN simulated with METIS@ELT
Mach, Michael
The structure of the torus in active galactic nuclei (AGN) has recently been shown to be clumpy, meaning the torus consists of geometrically thick dust structures on scales between tens of parsecs down to subparsecs at temperatures between T ~ 300 - 800 K. The only instruments with sufficient resolution to observe these structures in mid-IR were the VLTI instrument MIDI and MATISSE performing interferometry. However, the need for increased sensitivity along with the desire to be able to directly image the clumpy torus calls for observations with METIS, the upcoming mid-infrared ELT Imager and Spectrograph.In anticipation of METIS becoming available to the community, we are using the METIS instrument data simulator to simulate the dusty structures of the clumpy torus as they would be observed by METIS. This will showcase the potential of future METIS observations to shed light on the chemical composition and physical parameters of the hot & cold torus structures. It will also deliver diagnostics on the level of radiation to be expected from the central engine, and provide new insights into the process of mass transfer from the torus onto the central black hole. Additionally, we will show how far along the redshift axis these structures can be reasonably observed, distinguished, and analyzed to put the capabilities of METIS into reference of the current possibilities of instruments and define the discovery space in this field of research. Observational data is mainly provided by continuum emission at T ~ 300 K, the emission of forbidden lines (e.g. [NeII], [SIV], [ArII]), and polycyclic aromatic hydrocarbon (PAH) lines in the mid-IR.
A Molecular Dynamics approach to generate silicate nanodust models in circumstellar environments.
Macià Escatllar, Antoni
Nano-dust particles play an important role as condensation centers for ices and catalyzing reactions of important molecules such as H2. The mean composition of silicate dust has been figuerd, but doubts remain on the real structures of this particles and how their IR spectra shifts due to the conditions in which they are formed.Theoretical and computational chemistry is a powerful tool applied in astrochemistry in several ways. With respect to silicate nanodust, computational models have centered in either formation of very small nanoclusters or on the adsorption of molecules on the surfaces of bulk crystal systems, such as H2 and CO. Most theoretical work has dealt with crystal structures, but amorphous grains are thought to be the main component of dust in the interstellar medium. Hence, a proper understanding of the properties of silicates require computational studies on amorphous particles, which not only contain a higher amount of defects, but also posses coarse surfaces and non-homogeneous distribution of their elements due to the nature of the formation process.We present here a scheme to generate models of amorphous particles following the conditions for the grain growth in post-AGB stars. Following the growth process described in Goumans & Bromley 2012, we follow the trajectory of a dust particle in time, and calculate the positions where each monomeric addition takes place. This allows to set-up molecular dynamics simulations where the incoming particle aggregates into the seed particle in a processes mirroring the real conditions. The result is a random amorphous particle whose physical properties we can average over different runs and follow with respect to time to provide a better understanding of the sphericity, surface area, or silica polimerization, to mention some parameters relevant to IR spectroscopy and nucleation rates. We present preliminary information of this properties, and some calculated IR spectra using IPs for particles of sizes ~5nm.
Is WASP-12 b falling onto its host star?
Maciejewski, Gracjan
With an orbital period as short as 26 hours, the transiting giant planet WASP-12 b belongs to a group of planets on the tightest orbits. We detected the apparent shortening of its orbital period that could be caused by orbital decay or apsidal precession due to tidal interactions. The reanalysis of available data allowed us to identify an alternative scenario that explains the departure of transit timing from a linear ephemeris. We have found a solution with an additional planet from a Neptune-mass regime and an orbital period of 3 days. Numerical simulations show that this planet can perturb the orbital motion of WASP-12 b that manifests as the apparent orbital decay. The proposed planet is likely to transit the host star. This finding rises an opportunity to confirm the existence of the planet via the transit method.
Mass Loss Rates of Li-rich AGB/RGB Stars
Maciel, Walter
A sample of AGB/RGB stars with an excess of Li abundances is considered in order to estimate their mass loss rates. Our method is based on a correlation between the Li abundances and the stellar luminosity, using a modified version of Reimers formula. We have adopted a calibration on the basis of an empirical correlation between the mass loss rate and some stellar parameters. We conclude that most Li-rich stars have lower mass loss rates compared with the majority of AGB/RGB stars, which show no evidences of Li enhancements, so that the Li enrichment process is apparently not associated with an increased mass loss rate.
Oxygen and iron radial abundance gradients from galactic cepheids
Maciel, Walter
We consider the determination of O/H and Fe/H radial abundance gradients in the galactic disk on the basis of a large sample of cepheid variable stars. We assume a simple linear gradient throughout the galactic disk as well as other possibilities to explain the observed data, such as the existence of multiple slopes and non-linear variations. We report preliminary results for a total sample of 361 cepheid stars, for which we conclude that a single gradient is statistically the best estimate in the inner galaxy from about 3 kpc from the centre, with possibly some flattening at large galactocentric distances.
The stellar pulsation timing method to detect substellar companions
Mackebrandt, Felix
Planetary systems undergo their most fateful changes during the pre- and post-main sequence phase of the host star. Subdwarf B stars (sdBs) are laboratories to test how planets survive and influence the late phases of stellar evolution. Those stars are stripped He-burning cores of red giants with a thin hydrogen atmosphere. The canonical model to explain the existence of sdB stars is binary evolution. Formation scenarios for single sdBs are more controversially discussed and can be hard to reconcile with observational properties. Besides the merger of two helium white dwarfs or other merger processes for apparently single sdB stars, an alternative formation channel involves planetary systems. During the RGB the star would develop a common envelope with a giant planet that leads to the loss of the envelope._x005F To empirically test this scenario, we have monitored the rapid pulsations of a number of sdBs, which allows to detect sub-stellar companions. Periodic variations in the expected arrival times of the pulsation maxima provide evidence for companions. This timing method is particularly sensitive to planets at large distances and complementary to other exoplanet detection methods which are not efficient for stars with small radii and high gravities. Thus, the timing method opens up a new parameter range in terms of the host stars and helps to understand the formation process of single sdBs. Examples of planetary candidates in sdB-systems are V391 Peg b, HW Vir b, c, HS 0705+67003 b and Kepler-429 b, c, d._x005F In consideration of future photometric space missions like TESS or PLATO it is essential to enhance the diversity of potential exoplanet host stars that can be probed. We report on the development of an automated pipeline and simulations to validate this method and to apply it to a variety of both ground- and space-based observations. This allows us not only to probe evolved stars but also other pulsating stars such as main-sequence A stars as exoplanet host stars.
3D Time-dependent Hydrodynamical and Radiative Transfer Modeling of Eta Carinae's Innermost Fossil Colliding Wind Structures
Madura, Thomas
Eta Carinae is the most massive active binary within 10,000 light-years. While famous for the largest non-terminal stellar explosion ever recorded, observations reveal a supermassive (120 M_Sun) binary consisting of a highly unstable LBV and either a WR or extreme O star in a very eccentric orbit (e = 0.9) with a 5.54-year period. Dramatic changes across multiple wavelengths are routinely observed as the stars move about in their highly elliptical orbits, especially around periastron when the hot (~40 kK) companion star delves deep into the denser and much cooler (~15 kK) extended wind photosphere of the primary. Many of these changes are due to a dynamic wind-wind collision region (WWCR) that forms between the stars, plus expanding radiation-illuminated fossil WWCRs formed one, two, and three 5.54-year orbital cycles ago. These fossil WWCRs have been spatially and spectrally resolved by the Hubble Space Telescope (HST)/STIS at multiple epochs, resulting in data cubes that spatially map Eta Carinae’s innermost WWCRs and follow temporal changes in several forbidden emission lines (e.g. [Fe III] 4659Å, [Fe II] 4815Å) across the 5.54-year cycle. We present initial results of 3D time-dependent hydrodynamical and radiative-transfer simulations of the Eta Carinae binary and its WWCRs with the goal of producing synthetic data cubes of forbidden emission lines for comparison to the available HST/STIS observations. Comparison of the theoretical models to the observations reveals important details about the binary’s orbital motion, photoionization properties, and recent (5 – 15 year) mass loss history. Such an analysis also provides a baseline for following future changes in Eta Carinae, essential for understanding the late-stage evolution of a nearby supernova progenitor. Our modeling methods can also be adapted to a number of other colliding wind binary systems (e.g. WR 140) that will be studied with future observatories (e.g. JWST).
Astronomy for Students with Visual Impairments: Development of a Hands-on Career Exploration Lab
Madura, Thomas
For students with blindness/visual impairments (B/VI), the possibility of a future in astronomy, or any science, technology, engineering, and mathematics (STEM) field, seems daunting. In order to bolster astronomy and STEM opportunities for high school students with B/VI (ages 15 – 19) we developed a series of student Career Exploration Labs (CELs). Our CEL methodology employs tactile astronomy instruction via three-dimensional (3D) printing technologies and 3D-printed models, STEM teachers of students with B/VI, interactions with professional scientists with B/VI acting as role models, and partnerships with local STEM businesses that provide insights into possible career paths. In cooperation with the South Carolina Commission for the Blind and the Bureau of Services for Blind Persons in Michigan, we held three week-long pilot CELs during June 2017, June 2018, and July 2018. We gathered pre- and post-CEL data via student and teacher surveys, quantitative assessments of students’ astronomy knowledge and spatial thinking skills, and audio and video recordings of the CEL activities in order to study to what extent the CEL model could enhance high school students with B/VI’s attitudes towards, interests in, and capacities to participate in astronomy education and careers. Once tested and refined, we will make our 3D model files and associated activities freely available to the community for further use and study. This work serves as a testbed for an expanded international CEL program.
The submm properties of dust in the detached shells around carbon AGB stars
Maercker, Matthias
The origin and properties of dust in the universe, and the contribution from AGB stars, is a fundamental question in galaxy evolution. We constrain the properties of the dust grains in the thin detached shells around the carbon AGB stars R Scl, U Ant, V644 Sco, and DR Ser. The shells were created during recent thermal pulses, and the dust properties play a crucial role in understanding the wind-driving mechanism, the evolution of the star throughout the thermal pulse cycle, and the type and amount of dust returned to the ISM from AGB stars. We use new observations from LABOCA and ALMA to model the entire SED including submm wavelengths. For all objects, we find an excess emission in the submm. Spatially resolved observations confine this excess to the detached shells. However, a straightforward explanation for this excess is still lacking. While very large, cold grains can explain the submm flux, they do not reproduce the overall shape of the SED in the FIR and submm. Other obvious grain properties (e.g., composition or geometry) also do not reproduce the observed SEDs. The results imply that the submm observations probe properties of the dust grains that are not typically considered, but may be critical for a complete understanding of dust around evolved stars. A similar SED shape and submm excess has been seen in observations of the small and large magellanic clouds, and has been attributed to unknown dust properties. If the origin of this excess is the same as for the detached shell sources, this would have important implications on the contribution to the total dust budget from AGB stars to galaxies.
Observational constraints on thermal pulses and the evolution of the mass-loss rate
Maercker, Matthias
AGB stars are the dominant producers of half of the elements heavier than iron, and thus play a crucial role in the chemical evolution of galaxies. The elemental yields from AGB stars depend critically on the number of thermal pulses the star experiences during AGB evolution, and hence on the lifetime of the star on the AGB. The evolution of the mass loss throughout the entire thermal pulse cycle therefore strongly affects the total return of elements and dust to the interstellar medium. ALMA observations of the detached shell around the carbon AGB star U Ant allow us to trace the mass-loss history since it was created in a thermal pulse 3000 years ago. In addition to the detailed structure of the shell, the ALMA data show the extended, smooth post-pulse and present day wind. Combined with Herschel/PACS image of thermal dust emission from the shell, the full analysis of the ALMA data will constrain the formation and evolution of the shell, and the evolution of the mass loss during and after a thermal pulse. The results are put into contrast to the detached-shell source R Scl, for which the evolution of the mass loss is significantly different from model predictions. Together with new ALMA data on the inner wind of R Scl, the results provide a unique test-bed for models of stellar evolution, and may be the only direct way of observationally constraining the evolution of AGB stars throughout the thermal pulse cycle. The observations of U Ant will eventually play a key role in our understanding of AGB stars and their place in the evolution of galaxies and the universe.
Phase-lag measurements in dust-scattered, polarised light: the distance to R Scl
Maercker, Matthias
Distance measurements to astronomical objects are essential for understanding their intrinsic properties. For asymptotic giant branch (AGB) stars it is particularly difficult to derive accurate distance estimates. In the case of the carbon AGB star R Sculptoris, the uncertain distance significantly affects the interpretation of observations regarding the evolution of the stellar mass loss during and after the most recent thermal pulse. I provide a new, independent measurement of the distance to R Sculptoris, using phase-lag measurements in the thin, dusty detached-shell surrounding the star. By observing in polarised light, we imaged the shell in the plane of the sky, removing any uncertainty due to geometrical effects. The variation of the scattered light in the shell is of the same amplitude and period as the stellar pulsation, but with a phase lag that depends on the absolute size of the shell. The polarised, scattered light measurements reduce the absolute uncertainty of the distance estimate to this source to approx. 10%, giving a distance of 361 +/- 44 pc. This distance estimate is consistent with previous estimates, but is one of the most accurate measurements of the distance to R Scl to date. In the future, the same technique may be used for other detached-shell sources, or any circumstellar envelope with clear dust features, and may offer an independent distance measurement to AGB stars.
The SOUTH POL Survey: Status and First Results
Magalhaes, Antonio Mario
SOUTH POL is a survey of the Southern sky in optical linearly polarized light. It uses a newly built, wide field polarimeter for T80-S, an 84 cm robotic telescope installed at Cerro Tololo (CTIO), Chile. It will initially cover the sky South of declination -15 deg aiming at a polarimetric accuracy < 0.1% at V~14-15. The telescope-camera combination covers a field of about 2.0 square degrees.SOUTH POL will impact areas such as Cosmology, Extragalactic Astronomy, Interstellar Medium of the Galaxy and Magellanic Clouds, Star Formation, Stellar Envelopes, Stellar Explosions and Solar System. Both catalog data and raw images will be made available. The polarimeter has been successfully commissioned in mid-November, 2017. We will describe the instrument, data reduction and its challenges, as well as a sample of the first results.
The radial gradients of the heavy elements in the Galaxy
Magrini, Laura
Several works have found an increase of the abundances of the s-process neutron- capture elements in the youngest Galactic stellar populations. These trends have given important constraints to stellar and Galactic evolution, suggesting a strong contribution from low mass stars in the production of s-process elements. However, the literature results were limited to the Solar neighborhood. Using the analysis of the Gaia-ESO high-resolution spectra of field and open cluster stars, we have extended the study to different radial and metallicity bins. We have found a strong dependency of the abundances and of the relative abundance ratios, as for instance [Ba/Y], on the Galactocentric position. This indicates the presence of a relationship of the current s-process element abundances not only on the metallicity, but also on the the infall time scales and star formation history.
Optical/NIR high resolution spectroscopy of field and cluster RR Lyrae as a stepping stone for ELTs
Magurno, Davide
RR Lyrae stars are excellent distance indicators and tracers of old stellar populations. They have been the cross-road of a paramount theoretical and observational efforts, however, we still lack a homogeneous metallicity scale based on high-resolution spectra, especially for the Bulge region. To fill this gap, we started an observing campaign aimed at collecting optical (BVRI, M2FS at Magellan, UVES at VLT) and near-infrared (zYJ, WINERED at NTT), high resolution, high signal to noise ratio spectra to estimate the abundance gradients across the Galactic Halo and the Bulge. One of the main goal of the current project is to provide a homogeneous metallicity scale (iron, alpha elements) for field and cluster RRLs. We also plan to constrain the dependence of NIR distance diagnostics (Period-Luminosity, Period-Wesenheit relations) in the metal content. Moreover, the comparison between abundance distributions and predictions based on up-to-date chemical evolution models will allow us to investigate the impact of the environment in the early chemical evolution of the Milky Way. We also investigate the role that different approaches concerning the telluric subtraction (telluric standards, sky models) have on the abundance precision. We also outline how the current efforts will pave the way to fully exploit the unprecedented spectroscopic capabilities of the new generation of ELTs.
Probing the Dynamics & Energetics of Radio-loud AGN
Mahatma, Vijay
Radio jets are the large-scale and extragalactic footprints of accretion onto supermassive black holes, and are suggested to be the key ingredient controlling the galaxy mass function. Of particular importance is their jet power - the time-averaged energetic feedback into their environment. To determine a jet power, an accurate estimate of the age of the radio source is required, which is known to give discrepant results based on the method of calculation. Here, we attempt to resolve the spectral age/dynamical age discrepancy using high resolution radio and X-ray observations of two powerful radio galaxies, and consequently determine their source energetics. I also present some recent observations of the rare classes of remnant and restarting radio galaxies, which are crucial to inferring the global duty cycle of radio galaxies.
Water transport and loss in planet formation: a collision outcome parameter study
Maindl, Thomas I.
As it is well established, the formation of terrestrial planets involves a long sequence of collisions of protoplanetary bodies. Water in particular may have been brought to the accretion zone of Earth by water-carrying planetesimals and planetary embryos from outer regions of the asteroid belt. In most simulations of planet formation, these collisions are treated as perfect inelastic merging events and consequently ignore fragmentation and the loss of volatiles such as water. Compared to the actual outcome of realistic, physical collisions, the masses as well as the water contents of the final terrestrial planets are significantly overestimated.In order to arrive at a more realistic estimate of the amount of water transported to Earth’s accretion zone, we performed a suite of several hundred collision simulations with our 3D smooth particle hydrodynamics (SPH) code. We discuss the outcome of our simulations in terms of mass and water content of final bodies and for different parameters of the system including collision velocity, impact angle, and the masses and water-mass fractions of the projectile and target. Our results present a more realistic estimate of water transport rates in dynamical studies of planet formation.
Material properties and momentum transfer uncertainty for DART
Maindl, Thomas I.
Kinetic impactors are one possible option to deflect sub kilometer sized asteroids that may collide with planet Earth. The momentum delivered by such a spacecraft would change the potentially hazardous asteroid's orbit so as to avoid an impact on our home world. Near-Earth asteroids with diameters the order of 100m are believed to be very common and consist of a wide variety of materials with varying bulk densities. A kinetic impact on such targets would not only entail a direct momentum transfer from the spacecraft to the target, but also post-impact effects caused by ejected material resulting in a momentum transfer efficiency ß>1. The latter is only weakly constrained, however. We study the momentum transfer onto an asteroid after it is hit by a kinetic impactor comparable to the Double Asteroid Redirection Test (DART) mission concept's projectile. The notional target is an asteroid similar in size to the secondary body of the binary near-Earth asteroid (65803) Didymos (approx. 150m) consisting of a variety of different materials such as solid basaltic rock, carbonaceous chondrite, porous rock, a blend of porous rock and water ice, and – as an extreme case – solid iron. Impact simulations are conducted within a state-of-the-art 3D smooth particle hydrodynamics framework that allows us to present likely ß factors for different target materials. We compare our results to other published work and discuss potential consequences for DART.
Discovery of a new ULX pulsar in NGC 300
Maitra, Chandreyee
We report the discovery of pulsations from NGC 300 ULX1 during simultanous XMM-Newton / NuSTAR observations in Dec. 2016. The period decreased from 31.7 s to 31.5 s over ~310 ks linearly, resulting in a spin period derivative of -5.6e-07 s/s, probably the largest ever observed. Archival Swift observations revealed that the period decreased exponentially from ~45 s to ~20 s over 21 months. The pulses are highly modulated with a pulsed fraction strongly increasing with energy and reaching nearly 80% at energies above 10 keV. The X-ray spectra can be modelled by a power law plus soft black-body component. In 2016 the X-ray luminosity was at ~3e39 erg/s. The X-ray spectra from an archival XMM-Newton observation from 2010 can be explained by the same model, however, with much higher absorption. This suggests, that the intrinsic luminosity did not change much since that epoch. NGC 300 ULX1 shares many properties with supergiant high mass X-ray binaries, however, at an extreme accretion rate.
Timing and Spectral studies of SXP 15.3 near its Eddington luminosity
Maitra, Chandreyee
SXP 15.3 (RX J0052.1-7319) is a Be X-ray binary pulsar located in the Small Magellanic Cloud. The source was classified as a transient X-ray binary candidate based on ROSAT observations in the 1990's, and pulsations at ~15.3 s were subsequently discovered from an outburst in 1996 from the ROSAT data. The source has never been studied in an outburst or a bright state ever since. Following reports of an outburst in November 2017, we triggered a Target of Opportunity observation of SXP 15.3 with AstroSat. We report here the first broadband spectral and timing studies of the source, when the source was accreting near the Eddington limit of 10^38 erg/s. We discuss the energy dependence of the pulse profiles and the broadband spectrum in context of accretion onto magnetized neutron stars accreting near its Eddington limit.
Serendipitous discovery of a pair of faint dwarf galaxies
Makarov, Dmitry
In framework of the study of the distribution and peculiar motion of galaxies in the Local Volume with Hubble Space Telescope we discovered a physical pair of dwarf galaxies with the absolute magnitudes of MV=-13.3 and -9.4 mag. We determined the distance to this pair of 9.2 Mpc using the tip of the red giant branch. The projected separation between the galaxies in pair is only 3.9 kpc. The existence of such systems of dwarfs is not unusual. On a scale of 3 Mpc most dwarfs are associated with either a luminous group or associations of dwarf galaxies. The groups of dwarfs where both components have the luminosity lower than the Small Magellanic Cloud form a significant population of all groups on the scale of 40 Mpc. The newly discovered system of dwarfs is one of the faintest known groups of galaxies.
The spatial segregation impact on the star formation histories of nearby dwarf spheroidal galaxies
Makarova, Lidia
Nearby dwarf galaxies are an excellent laboratory to study the processes of star formation, since they are resolved into individual stars, and their structure is relatively simple. At the same time, the role of dwarf galaxies in the formation and evolution of visible structures in the Universe is very significant. In recent years, we have discovered and investigated a number of isolated dwarf spheroidals (dSphs). It is important to get detailed consideration to such the rare objects, since the common recent scenario of dSphs formation suggests that such galaxies are formed due to the interaction between a rotationally supported dwarf irregular galaxy and a MW-sized host galaxy. Then rather isolated dwarfs should be exceptionally irregular. However, we have found a number dwarf galaxies, which are classical spheroidal, and are located in isolation. Using our HST/ACS observations of these objects, we homogeneously measured their star formation histories (SFHs). We determined the star formation rate as a function of time, as well as the age and metallicity of the stellar populations. All objects demonstrate a complex SFH, with a significant portion of stars formed 10-13 Gyr ago. Nevertheless, the stars of middle ages (1-8 Gyr) are presented. In order to understand how the SF parameters influence the evolution of dSphs, we also studied a sample of nearest dSphs in a different environment: isolated (d<2 Mpc); beyond the Local Group (LG) virial radius (but within the LG zero velocity sphere); and the satellites of M31 located within the virial zone (300 kpc). Using archival HST/ACS and WFPC2 observations of the dSphs, we measured their SFHs. A comparative analysis of the parameters obtained give us a possibility to distinguish a possible effect of the spatial segregation on the dSphs evolution scenario.
Non-stationary accretion diversities onto black holes of different masses in binary systems
Malanchev, Konstantin
Properties of non-stationary accretion onto black holes of different masses in binary systems are discussed. In a close binary containing a supermassive black hole, a novel sub-critical accretion regime in the innermost radiation-dominated zone of the accretion disk is found, different from accretion regime in stellar mass black hole X-ray binaries. In this regime, the opacity is determined by absorption and not by Thomson scattering. We show that it can be possible to overcome the thermal instability of the innermost zone of the disk to obtain power-law time solutions of the non-stationary accretion onto such massive black holes. The found solutions are applied to explain very luminous optical transients recently discovered in the centres of some active galaxies (e.g., PS1-10adi, Kankare et al. 2017), which are hard to explain as tidal-disruption events. We also discuss the possible role of the outflows and remote gas structures surrounding such binary systems in producing the optical and infrared light curves.
The NASA Exoplanet Exploration Program: Update and Prospects for the 2020's and Beyond
Mamajek, Eric
The NASA Exoplanet Exploration Program (ExEP) is responsible forimplementing NASA's plans for discovering and characterizingexoplanets, and identifying candidates that could harbor life. ExEPmanages concept studies, technology development programs, ground-basedscience programs that help complete the science goals of current andfuture NASA missions (and that enable the design of next generationexoplanet missions), and communicates the excitement of exoplanetresearch to the public. We will review recent activities in theNASA-NSF exoplanet research collaboration (NN-Explore), progress inthe characterization of exozodiacal light, the status of ongoingstudies of future exoplanet flagship missions, and recent technologymilestones (including updates on the progress of starshade andcoronagraph technology capable of imaging and characterizingexo-Earths).
The interaction of the Helix nebula with the interstellar medium; a solid case.
Manchado, Arturo
As an asymptotic giant branch (AGB) star loses mass, moving with respect to the interstellar medium (ISM),its morphological shape is affected and a characteristic bow shock appears. This is the case for the planetary nebula (PN) NGC 7293 (The Helix nebula).This PN represents one of the rare instances in which theoretical predictions of stellar evolution can be accurately tested against observations.The distance is well determine, thus the mass of the progenitor star that has evolved into a PN, and the velocity and proper motion of the central star is known.We performed numerical simulations of the interaction of the Helix nebula with the local ISM and constrain the evolution of both the progenitor and the nebula.The simulations reproduce well the observations, in particular, the multiple bow-shock structures ahead of the star can be explained by multiple fragmentation ofthe shock front where the direct interaction of the stellar wind with the ISM takes place.The outer nebular size (or PN halo) is the result of the mass-loss associated to the last thermal pulse only, i.e. the last 50 000 yr of evolution on the AGB phaseand the PN-ISM interaction.
The galaxy-halo connection: Demography, scaling relations and radial distributions of the dark and luminous matter
Mancillas-Vaquera, Brisa
To understand the galaxy formation and evolution is required a cosmological framework. The current cosmological paradigm is summarized in the so called ?-cold dark matter model. The observations and the cosmological numerical simulations suggest that disk formation is the generic process of assembly of galaxies, while the spheroidal component arises from the merging disks as well as from their secular evolution. Through a semi-empirical approach a galaxy-halo connection is obtained mainly at a demographic level, constraining the most relevant properties like the Ms-Mh relation (Rodriguez-Puebla et al. 2015), which summarizes the main astrophysical processes of galaxy formation and evolution (gas heating and cooling, SF, SN- and AGN-driven feedback, etc.). An important question is to see how such approach is projected towards the structural-dynamic properties of the observed galaxies and the radial distributions of dynamic and luminous mass, with the purpose of having a complete demographic and dynamic-structural description of the observed galaxies and their haloes. Such description allows us to constrain the key parameters of the formation and evolution of galaxies, like the angular momentum transport of the gas from which galaxies are formed, the role of the mergers, the level of adiabatic contraction of the halo due to the formation of the galactic disk. To explore this question, we generated a mock catalog of millions of spatially resolved bulge-pseudobulge-disk-halo systems, by applying the semi-empirical approach on a given N-body simulated cosmological box described in Klypin et al. (2016) and Rodríguez-Puebla et al. (2016), and using the properties of halos and their respective fractions of stellar and gaseous mass (reported in Rodríguez-Puebla et al. 2017), as initial conditions for the static models that produce the resolved galaxies. The static models are based on the formalism of Mo et al. (1998) and its extension in Dutton et al. (2007).
The origin of a series of EUV confined eruptions
Mandrini, Cristina
We analyze a series of EUV confined eruptions that occurred in active region (AR) NOAA 11476. The events were associated to M-class flares. We use observations in multiple wavelengths (EUV, X-rays, Halpha, and magnetograms) from instruments in space and on the ground. The analysis of the magnetic configuration shows the presence of two rotating bipoles at the center of the AR. Their evolution along two days can transfer a high amount of twist to the magnetic structure in the coronal volume above. The observations suggest that the free magnetic energy accumulated in this way is released through reconnection due to the interaction of the bipoles with the pre-existing coronal structures. As a consequence, flares occurred and cool and dense material was ejected along the reconnected loops in the form of EUV surges, with one of them also observed in Halpha. Analyzing the magnetic topology using a force-free model of the coronal field, we identify the location of quasi-separatix layers (QSLs), where reconnection is prone to occur, and present a detailed interpretation of the chromospheric and coronal events.
ALMA observations of oxygen-bearing complex organic molecules towards the low-mass protostellar binary IRAS 16293--2422
Manigand, Sébastien
Many questions remain concerning the formation of complex organic molecules and their presence in the inner region of solar-type protostars. The nearby low-mass Class 0 protostellar binary IRAS 16293--2422 (IRAS16293 hereafter) is an excellent object to study these species on solar system scales. The Atacama Large Millimeter/submillimeter Array (ALMA) provides the high angular and spectral resolution as well as the sensitivity needed to study the physical and chemical structure of such protostars in unprecedented detail._x005F We use observations from the Protostellar Interferometric Line Survey (PILS; Jørgensen et al. 2016), an unbiased line survey of IRAS16293 using ALMA, to analyse oxygen-bearing complex organic molecules in both IRAS16293A and IRAS16293B. A comparative analysis of the two sources reveals differences in abundances for some of the species and their isotopologues. For example, formaldehyde (H2CO), glycolaldehyde (CH2OHCHO) and ethylene glycol (CH2OH)2 are more than one order of magnitude more abundant towards the A source compared to the B source measured relative to methanol._x005F In contrast, methyl formate (CH3OCHO), ethanol (C2H5OH) and dimethyl ether (CH3OCH3) show similar abundances towards the two components. In addition, the high sensitivity of the ALMA observations enabled many deuterated species to be detected, including doubly-deuterated methyl formate (CHD2OCHO) for the first time in the ISM (Manigand et al. 2018,subm.). The D/H ratio of CHD2OCHO and CH2DOCHO were found to be extremely enhanced compared to the canonical value 2 x 10-5, with CHD2OCHO D/H ratio 2--3 times higher than CH2DOCHO D/H ratio. Abundance and D/H ratios suggest that methyl formate forms through grain surface reactions involving H2CO and CH3OH photodissociation products (Chuang et al. 2016) and the deuteration enhancement is driven by H-D abstraction substitution processes on the grain.
Study of Energy Build-up time of Solar Flares
manisha, pithadia
Three super active regions have been studied in the present work to probe the time of energy build up in Solar Flares. Free magnetic field energy in the active region has been taken into consideration as the major source of energy build-up in the corona. We undertake the measurement of magnetic field complexity employing magnetograms from HMI/SDO to constrain the possible mechanisms of energy build-up. Three super active regions observed during February 2011, March-2012 and May 2013 are selected considering that each active region has produced a minimum of 10 flares with importance = C1.0 class and minimum one X-class flare during its passage on the disk. To quantifying the energy build up we measure the magnetic flux from the photospheric observations, which transfers to the corona through magnetic convection in the loops. The measured energy build-up time is observed to be in the range of 2 to 15 hours.
Formation and interaction of nanoparticles in the upper Earth atmosphere
Mann, Ingrid
Earth’s upper atmosphere where solar radiation determines the degree of ionization (ionosphere) contains nanoparticles with radii few 10 nm to less than nm. The nanoparticles form as a result of meteor ablation, the loss of material from cosmic dust and meteoroids at the transition between mesosphere and thermosphere (~70 - 130 km). The nanoparticles influence chemical processes and most likely contribute to formation of icy particles when temperatures are sufficiently low, in the polar mesosphere during summer. The nanoparticles are electrically charged and the ambient medium is partially ionized so that dusty plasma phenomena occur. The meteor ablation process is compared to the process of dust fragmentation during mutual collisions, as it occurs e.g. in the interplanetary medium and to some extent in the interstellar medium. The dust growth rates and the size limit of the particles are discussed in comparison to the conditions in e.g. the solar wind, the vicinity of a comet and the interstellar medium.
Clarifying the population of HMXBs in the Small Magellanic Cloud
Maravelias, Grigoris
The Small Magellanic Cloud (SMC) hosts a large number of High-mass X-ray binaries (~120) offering a unique laboratory to examine these sources with a homogenous and consistent approach. Almost all the sources with confirmed counterparts have as a companion an OB star with an equatorial decretion disk. This makes their population to stand out in ?a imaging and, subsequently they display strong emission Balmer lines. However, for a large fraction of the HMXB population in the SMC, although they are associated with one or more early-type stars, the actual counterpart and its nature are unclear. Thus, we performed extensive photometric and spectroscopic surveys to identify the optical counterparts to HMXB candidate sources. Using ?a imaging we discover that the OBe stars, i.e. the parent population of HMXBs, is ~13% of the total OB star population in the SMC down to 18.7 mag (equivalent to ~B8 type Main Sequence stars). Using this catalog we perform a cross-correlation with the most recent census of X-ray sources in the SMC (Haberl and Sturm, 2016) to verify the nature of known HMXBs and explore a number of candidate systems, in combination with spectroscopic observations. Moreover, using the most recent census of star clusters in the SMC (Bitsakis et al., 2018) we investigate the connection of the HMXBs with star-clusters and we use it to obtain a robust estimate of their kick velocities.
AstroReg: a world-wide astronomical registry
Maravelias, Grigoris
In the era of automated information, astronomers still waste a considerable amount of time looking for the correct contact details (e.g. mail, phone) of another researcher. Often the information found at institute websites are not up-to-date, incomplete or -incredibly- totally missing. When this is the case, one has to go through a tedious search to find the proper contact details, typically looking for the reference mail in the latest publication of a given astronomer. Except that sometimes the astronomer has changed address in the meanwhile, or did not report a contact mail. To overcome such unfortunate issues, we introduce AstroReg: a world-wide registry for astronomers providing instant access to the basic and updated information necessary to contact any astronomer at any institute. While submissions by astronomers themselves are favored (a process taking less than a minute), the database can be populated automatically by searching the public available information (and the corresponding profiles can be edited at a later step). Once queried, AstroReg provides the few basic (public) contact information (name, current affiliation, mail). Our goal is to include every single astronomer in the world and keep it updated as part of their CVs. The database will serve the community in two more ways: (a) constitute the first and most complete census of the astronomical community, (b) allow the formation of groups/associations (e.g. to support national or gender-wise demands for rights). Future features of the AstroReg platform could offer synergies with other platforms to enhance the profile/CVs of the partiipants, and collaborative tools for communication (e.g. proposal submissions).
A paradigm to develop new contributors to Astronomy
Maravelias, Grigoris
One of the most regular activity of amateur clubs is scientific outreach, a paramount channel to disseminate scientific results. This is performed typically through talks given either by professional scientists or amateurs with significant knowledge of their subject to a rather passive audience. The advance of technology has provided all the tools that can help amateurs to actively participate in the scientific output. What is missing often is the proper guidance. To address that within the Greek amateur community the Hellenic Amateur Astronomy Association materialized a training program (free of charge and open accessed) to develop scientific thought and the practical capabilities for amateurs to produce valuable results. The program run from November 2014 to May 2015 and each session (month) was dedicated to a particular field: the Sun, variable stars, comets, planets, artificial satellites, meteors. For each session a professional and/or an experienced amateur astronomer was leading the course consisting of: (i) a theoretical part with talks on the highlights of the field and the necessary observing techniques, (ii) a hands-on session, where the participants were actively involved in obtaining observations, data reduction, and final analysis. In total about 100 participants gained significant experience with respect to the observational procedures and the scientific methodology.
Cape Town’s Iziko Planetarium & Digital Dome : a cutting edge platform for big-data science & public engagement at 360 degrees
Marchetti, Lucia
The recently inaugurated Iziko Planetarium and Digital Dome is the most advanced digital planetarium on the African continent. This multi-functional, world class facility not only provides immersive multi-sensory edutainment and a platform for artistic production - it is also aimed to be used for cutting-edge scientific research and to optimise South Africa’s eResearch and data visualisation capacity.This digital full dome theatre provides audiences with an unequalled experience of animation and 360 degrees cinema; as well as making virtual exploration of the Universe, the inner workings of the human body, or the intricacies of an atomic structure possible.In addition, learners and educators from primary to tertiary levels will benefit from computer generated imagery that makes interactive teaching and visual learning possible; providing an unparalleled and accelerated learning experience.In my talk I will give an overview of the capabilities and goals of this cutting edge facilty in the local and international context. In particular, as a professional astronomer working with the planetarium to implement new practices for data visualisation and reasearch I will show how this platform can also be used as an effective public engagement platform at 360 degrees.
A SINGLE SERSIC INDEX-EFFECTIVE RADIUS RELATION BETWEEN MILKY WAY OUTER HALO SATELLITES.
Marchi, Sebastian
In this article we use structural properties of Milky Way’s outer halo (RG < 25kpc) satellites (dwarf spheroidal galaxies, ultra-faint dwarf galaxies and globular clusters) derived from deep, wide-field and homogeneous data, to present evidence of a correlation in the Sersic index - Effective radius plane for all outer halo satellites. We show that this correlation can be entirely reproduced by fitting empirical relations in the central surface brightness - absolute magnitude and Sersic index - absolute magnitude parameter spaces, and by assuming the existence of two types of outer halo GCs: one of high surface brightness (HSB group), with properties similar to inner halo clusters; and another of low surface brightness (LSB group), which share characteristics with dwarf spheroidal and ultra-faint dwarf galaxies. Given the similarities of LSB clusters with dwarf spheroidal and ultra-faint dwarf galaxies, we discuss the possibility that outer halo clusters also originated inside dark matter halos and that tidal forces from different galaxy host’s potentials are responsible for the different properties between HSB and LSB clusters.
Unistellar eVscopes: Smart, Portable And Easy-To-Use Telescopes For Exploration, Interactive Learning, And Citizen Astronomy
Marchis, Franck
Unistellar has developed the eVscope, a compact telescope that amplifies light so users can finally see hundreds of nebulae and galaxies directly through its eyepiece. It can also pinpoint and identify objects in the sky, making amateur astronomy fun and more accessible to the public.Thanks to its sensitivity, the eVscope is a powerful tool capable of generating data that can be used by scientists to search for transient events like supernovae, near-earth asteroids, and comets. Because of the larger field of regard provided by a constellation of small, smart telescopes, our network could provide additional data to the few existing large telescopes. Unistellar initiated a partnership with the SETI Institute to identify and develop scientific applications for our network of telescopes.We will summarize the technology behind the telescope and its real-time data processing, then show several applications, including asteroid occultations, lightcurves and astrometry of asteroids accessible to the users. Finally, we will discuss Unistellar network’s potential to make citizen astronomy a reality by offering all users (newbie or experienced) a tool to explore the night sky with a powerful and reliable instrument while they contribute to scientific investigations.
Probing Dwarf Galaxies in Low Density Environments
Marleau, Francine
Recent discoveries on dwarf galaxies, such as their planar rotationaround the Milky Way and Andromeda galaxies, have challenged ourunderstanding of galaxy formation and evolution. While these dwarfgalaxies and others in the Local Group and in a few nearby clustershave been studied in considerable detail, relatively few observingprograms have focused on the study of this population of galaxies inlow density environments. Using the optical data obtained in thecontext of MATLAS, a deep imaging large program at CFHT, we havesystematically assembled the largest sample of dwarf galaxies in lowdensity environments. These dwarfs have magnitudes, surfacebrightnesses and sizes comparable to their Local Group and clustercounterparts. I will present results on their visual classification,2D surface brightness profile fitting, local environment andclustering properties, and discuss how these new findings impact ourcurrent understanding of how these galaxies form and evolve.
Spectroscopic, photometric, and polarimetric modeling of asteroid (4) Vesta
Martikainen, Julia
We present a novel simulation framework for modeling the spectroscopy, photometry, and polarimetry of asteroid (4) Vesta. In order to model Vesta, we derive the complex refractive indices of howardite, abundant on Vesta’s surface. Spectral modeling is carried out in multiple parts: first, we use the Superposition T-Matrix Method (STMM, [1]) and the numerical method of radiative transfer with reciprocal transactions (R2T2, [2]) to compute scattering matrices and single-scattering albedos for small howardite particles (see [3]) with particle sizes less than the wavelength of the incident light. Second, we use SIRIS4 [4,5], a ray-optics code that simulates light scattering by Gaussian-random-sphere particles larger than the wavelength of the incident light, to compute the scattering matrices and single-scattering albedos for larger howardite particles (10, 20, 30, 40, and 50 microns). Finally, the scattering matrices and single-scattering albedos of the different particle sizes are averaged over a power law distribution to obtain the final spectrum. We also model Vesta’s photometric phase curve and with the same model explain the observed opposition effect and negative linear polarization.ReferencesMarkkanen, J., and Yuffa, A. J., 2017: Fast superposition T-matrix solution for clusters with arbitrarily-shaped constituent particles. JQSRT 189, 181-189.Muinonen, K. et al. 2018: Multiple scattering in discrete random media using incoherent interactions. Opt. Lett. 43, 683-686.Muinonen, K. et al. 2018: Asteroid photometric and polarimetric phase effects: Modeling for the main taxonomical classes. Conference abstract, this meeting.Lindqvist, H. et al. 2018: Ray optics with inhomogeneous waves applied to scattering by ice crystals. JQSRT, submitted.Martikainen, J. et al. 2018: Spectral modeling of meteorites at UV-vis-NIR wavelengths. JQSRT 204, 144-151.
Observations of Inflowing Gas and Angular Momentum with CWI
Martin, Christopher
We describe observations with the Palomar Cosmic Web Imager and the newly commissioned Keck Cosmic Web Imager of the Circum-Galactic Medium (CGM). We show ubiquitous Lyman alpha emission near 2<z<3 qsos,="" a="" significant="" number="" of="" systems="" velocity="" shear="" and="" angular="" momentum,="" filamentary="" disklike="" morphology,="" features="" expected="" from="" cold="" flow="" inspiral="" structures.="" in="" particular,="" new="" observations="" with="" kcwi="" show="" unambiguously="" both="" rotation="" radial="" inflow="" patterns,="" strong="" evidence="" for="" cold-flow="" origin="" high-z="" star-forming="" galaxies="" the="" deliverance="" momentum="" via="" forming="" galaxies. <="" p="">
</z<3></p>
Magneto-thermo-turbulent star formation in cosmic zoom-in spiral galaxies
Martin-Alvarez, Sergio
An incredibly successful and simple description of star formation on galactic scales is the Kennicutt-Schmidt law which relates the star formation rate to gas density. At smaller scales however, complex local dynamical processes driven by phenomenon such as stellar feedback, turbulence and/or magnetic fields are thought to be necessary to explain star formation.As numerical simulations are able to resolve unprecedented spatial scales, sub-grid prescriptions need to be adapted to consistently model those physical processes that still remain below the resolution limit. By means of a suite of constrained transport magnetohydrodynamical adaptive mesh refinement high-resolution cosmological zoom-in simulations of Milky Way-like spiral galaxies, we explore how modelling star formation through a local magneto-thermo-turbulent prescription affects the properties of the resulting galaxies. We focus specifically on the role played by magnetism. We find that for most levels of magnetisation, even though the presence of magnetic fields considerably modifies star formation histories, it does not substantially alter the resulting stellar mass. Only at the strongest magnetisations tested, is the stellar mass halved. We also explore how stellar feedback changes the effect of magnetic fields and hence star formation.
Detailed mass models for specific galaxies for CALIFA and MaNGA data: kinematical constrains and radial migration
Martinez-Bautista, Gerardo
With the use of detailed steady and N-body models for the potential of barred spiral galaxies, we construct from observed kinematics, rotation curves, mass and chemical abundances, specific galaxies from the MaNGA and Califa surveys, and analyse their stellar dynamics, preliminary results are presented on radial migration studies. This work has the potential to characterize some structural and dynamical parameters of the spiral arms and bars based on radial migration and the shape of the Metallicity Distribution Function (MDF).
Finding needles in the haystack: a comparison of outlier detection methods
Martínez-Galarza, Rafael
Upcoming large observational surveys such as the Large Synoptic Survey Telescope (LSST) will produce millions of irregularly-sampled astronomical light curves. The enhanced sensitivity and time-sampling strategies of LSST will open a new window for several fields of astronomy, including precision cosmology, variable stars, as well as the discovery and characterization of new solar system objects. However, the large volume of the data that LSST will produce will require sophisticated algorithms for processing and interpreting these light curves. One important related question is how to find the most anomalous light curves, those that are perhaps not explained by current models. In this talk I will discuss state-of-the-art anomaly detection methods that use machine learning to find needles in the upcoming haystack of data. I will discuss several approaches to feature extraction for irregular light curves, including the use of auto-encoding recurrent neural networks, and the performance of several anomaly detection algorithms with respect to the features used. I will show the results of applying these methods to several time domain surveys, including SDSS's Stripe 82 and the All Sky Automated Survey (ASAS) catalog of variable stars, and present some of the weirdest light curves found.
The Photometric LSST Astronomical Time-Series Classification Challenge (PLAsTiCC)
Martínez-Galarza, Rafael
PLAsTiCC is a community-wide challenge to spur development of algorithms to classify astronomical transients expected to launch in the summer 2018. The Large Synoptic Survey Telescope (LSST) will discover tens of thousands of transient phenomena every single night. To deal with this massive onset of data, automated algorithms to classify and sort astronomical transients are crucial. PLAsTiCC, based on the highly successful Supernova Photometric Classification Challenge, will consist of a set of realistic LSST simulations of a variety of transient and variable phenomena. The challenge will be publicly available on a popular data science platform, encouraging algorithm submissions from outside the Astronomy community. I will present the major steps in getting this challenge ready, outline the several papers prepared that deal with the validation of the challenge data, and the metrics used to rank the participant's classiffiers and some early results of the communities response to it.
The NIRSpec Wide GTO Survey
Maseda, Michael
The sensitivity of JWST combined with the multi-object capabilities of NIRSpec facilitates a large spectroscopic galaxy survey at 1 < z < 6 with an enormous discovery space. I will present the planned wide-field GTO NIRSpec extragalactic survey (NIRSpec Wide), which will observe several thousand galaxies across half of the entire CANDELS area in 105h of total time. With relatively short individual exposures, the Wide survey is primarily designed to target the rarest sources in CANDELS and the brightest quiescent galaxies for which continuum spectroscopy will be possible, as well as providing a census of emission lines in galaxies at high redshifts. Broad rest-frame optical wavelength coverage at R=100 resolution is combined with R=2700 resolution focused on redshifted Ha and [OIII] emission lines to uncover the physical properties of galaxies such as SFR, metallicity, and AGN fraction as well as their ionized gas kinematics and a census of outflows. In the talk, I will focus on the challenges to prepare such complex observations for NIRSpec, the main science aims of the Wide survey, and the release plans for the public.
NEOCam: The Near-Earth Object Camera
Masiero, Joseph
The Near-Earth Object Camera (NEOCam) is NASA-funded mission concept that would discover and characterize the majority of potentially hazardous asteroids, allowing us to constrain the threat posed to Earth from an asteroid impact. The NEOCam mission would place a 50 cm, passively-cooled, infrared telescope at the Earth-Sun L1 point, where it would carry out a survey of the inner Solar system for nearby asteroids and comets. Here, we describe the details of the NEOCam mission, the nominal planned survey, and discuss predictions of the survey performance over the planned 5-year mission life.
New calibration of the Vilnius photometric system
Maskoliunas, Marius
The medium-band seven-color Vilnius photometric system for many years was an important tool to determine interstellar reddenings and distances of single stars due to its ability to recognize stars of different spectral types in the presence of different interstellar reddenings. The Gaia mission now allows to determine distances of stars with much better accuracy at least up to 1 kpc. However, multicolor photometry, which allows the classification of stars as well as the determination of stellar temperatures, gravities, metallicities and interstellar reddenings, remains an important method for distant stars.Here we present a semi-empirical calibration of color indices of the Vilnius photometric system in terms of physical parameters of stars, taking into account that many new spectroscopic investigations were published recently. The calibration is based on photoelectric color indices of more than 2000 stars with known effective temperatures, Gaia distances, gravities and metallicities. The physical parameters of stars (Teff, logg, [Fe/H]) were sampled from several sources. We also use the stellar atmosphere models ATLAS to calculate synthetic color indices of stars of spectral types and luminosities which are not covered by photometric observations. Finally, we present the new code for the classification of stars observed in the Vilnius system. Keywords: techniques: photometric – Vilnius photometric system - stars: parameters
The abundance of SiC2 in Carbon Star Envelopes
Massalkhi, Sarah
During the late stages of their evolution, AGB stars experience significant mass loss, which result in circumstellar envelopes (CSEs). These environments are efficient factories of molecules and dust grains. Although much has been advanced recently, there is still much to understand about how dust grains are formed and what the main gas-phase seeds are. This is the main driver of the ERC Synergy Project NANOCOSMOS. Silicon carbide (SiC) dust grains are exclusively found in the envelopes around C-type (C/O>1) AGB stars (Treffers & Cohen 1974). Here, we explore what the main precursor seeds of SiC dust grains are. Only three gas-phase molecules containing the Si-C bond have been observed in C-rich envelopes around AGB stars. The ring molecule SiC2 has been observed towards a few AGB and post-AGB stars (Thaddeus et al 1984; Bachiller et al. 1997; Zhang et al. 2009a,b), while SiC and Si2C have been only observed in the C star envelope IRC +10216 (Cernicharo et al. 1989, 2015). Much of the knowledge about the role of these three molecules as seeds of SiC dust grains comes from the study of IRC +10216. The scenario emerged from these studies suggests that only SiC2 and Si2C are present in the inner circumstellar layers of IRC +10216, while SiC is probably a photodissociation product of these molecules, and thus it is restricted to the outer envelope. This scenario indicates that SiC2 and Si2C are likely the main gas-phase seeds to form SiC dust grains. To explore the role of gas-phase SiC2 molecules on the formation of silicon carbide dust, we have used the IRAM 30m telescope to observe SiC2 in a wide sample of C-rich AGB stars. The observations have been interpreted carrying out non-LTE excitation and radiative transfer calculations to estimate the fractional abundance of SiC2 in the CSEs. The behavior of the abundance of SiC2 as a function of the envelope density indicates that this gas-phase molecule does indeed play an important role as a seed of silicon carbide dust.
RAS200: Sky & Earth: Engaging diverse partners and diverse audiences with astronomy: a new approach to public engagement
Massey, Robert
In 2020 the Royal Astronomical Society will celebrate its 200th anniversary. As part of our preparations, we inaugurated the £1 million outreach and engagement programme “RAS 200: Sky and Earth”, with the explicit aim of working with diverse audiences and partners and engaging citizens who would not normally consider astronomy and geophysics as something “for them”.RAS 200 is a “bottom up” scheme, which has encouraged organisations and community groups to propose ideas to the Society. Over the course of two rounds (2014-15 and 2016-17), RAS 200 has provided funding of £30k - £100k to each of fifteen national and community-based projects, including two Celtic cultural festivals, as well as “underserved” audiences such as young people not in employment or training, and prison inmates.I will discuss these projects in more detail, describe the successes and challenges of this model, and how the IAU and other partners might draw on our work.
MoRIA dwarf galaxies in the Fornax cluster environment
Mastropietro, Michele
We investigate the evolution of dwarf galaxies falling into the Fornax cluster starting from a selection of the MoRIA (Models of Realistic dwarfs In Action, Verbeke et al. 2015, 2017) suite of simulations.We first simulate the dwarfs outside the cluster up to 8 Gyr in order to obtain realistic late-type dwarf galaxies to inject into the cluster. Our simulations include detailed subgrid physics processes (radiative cooling, supernova feedback, UV background effects, and ionization-aware internal energy and equation of state of the gas) coded in a heavily modified GADGET-2 version developed in our group.We model the Fornax cluster gravitational potential as an NFW density profile and the intracluster gas density distribution as a beta model following Paolillo et al. (2002). We have carried out a set of simulations starting from a range of different trajectories and we study first separately and then together the effects of tidal stirring and ram-pressure stripping trying to isolate their effects. We show the results of the simulations following the dwarfs' journey into the Fornax cluster environment by tracking their star formation rates, gas distribution, stellar dynamics, and metallicity distribution.
How bright are the brightest stars with transiting exoplanets?
Masuda, Kento
We discuss the expected properties of nearby transiting exoplanets, based on the planet occurrence rate from the Kepler mission as well as the properties of nearby stars from the second data release of Gaia. We especially focus on estimating how bright the brightest stars hosting various types of transiting planets are, to inform future missions.
Global Magnetohydrodynamic Simulations of Coexisting Hot and Cool Disks in Black Hole Candidates
Matsumoto, Ryoji
We present the results of global three-dimensional magnetohydrodynamic simulations of the hard-to-soft state transitions in Cyg X-1 and other black hole candidates. We apply a radiation magnetohydrodynamic code CANS+R which adopts HLLD+MP5 scheme to solve resistive magnetohydrodynamic equations, and M1-closure scheme to update the 0th and 1st moment equations of radiative transfer. This code can handle both optically thin and optically thick region. The initial state is a hot torus threaded by weak azimuthal magnetic fields. Radiative cooling terms are switched on after a quasi-steady disk is formed by efficient angular momentum transport by magnetic turbulence driven by the magneto-rotational instability (MRI). When the equatorial density of the torus exceeds the threshold for the onset of the cooling instability, the torus shrinks in the vertical direction by cooling. When the global azimuthal magnetic field is symmetric with respect to the equatorial plane, magnetic pressure becomes dominant as the disk shrinks in the vertical direction by cooling. When the disk near the black hole stays in an optically thin, hot state, the interaction between the strong magnetic fields in the outer disk and the quasi-periodically reversing dynamo magnetic fields in the inner hot disk drives magnetic reconnection and plasmoid ejections. Furthermore the additional heating by magnetic reconnection prevents the outer disk to complete the transition to an optically thick, standard disk. The coexisting inner hot disk and outer cool, strongly magnetized disk can explain the X-ray spectrum and X-ray time variabilities observed in Cyg X-1 and other black hole candidates. We also discuss the effects of the thermal conduction.
Circumstellar Disks and Outflows in Turbulent Molecular Cloud Cores: Possible Formation Mechanism for Misaligned Systems
Matsumoto, Tomoaki
We investigate the formation of circumstellar disks and outflows subsequent to the collapse of molecular cloud cores with the magnetic field and turbulence. The ohmic dissipation is also considered, showing a high resistivity in the high-density regime. Numerical simulations are performed by using an adaptive mesh refinement (AMR) to follow the evolution up to ~1000 years after the formation of a protostar.In the simulations, circumstellar disks are formed around the protostars; those in magnetized models are considerably smaller than those in nonmagnetized models, but their size increases with time. The models with stronger magnetic fields tend to produce smaller disks. During evolution in the magnetized models, the mass ratios of a disk to a protostar is approximately constant at ~1%-10%.The circumstellar disks are aligned according to their angular momentum, and the outflows accelerate along the magnetic field on the 10-100 au scale; this produces a disk that is misaligned with the outflow. The magnetic field has an internal structure in the cloud cores, which causes misalignment between the outflows and the magnetic field on the scale of the cloud core. The distribution of the angular momentum vectors in a core also has a non-monotonic internal structure. This should create a time-dependent accretion of angular momenta onto the circumstellar disk. Therefore, the circumstellar disks are expected to change their orientation as well as their sizes in the long-term evolutions.The models with strong magnetic field tend to exhibit cavities in the flat, infalling envelopes. The radius of the cavity increases with time, and it increases up to ~50 au by the end of the simulation. The cavities are caused by the magnetic pressure. Such cavities probably correspond to the complex circumstellar structures, which have been revealed by the recent high-resolution observations.
B-fields and dust grains in the L1689 stream region: an interpretation of Planck polarization data
Matsumura, Masafumi
We investigate the polarization properties around the L1689 stream in rho Oph star forming region. We have found that the observed polarization with Planck makes a nearly closed curve in the Stokes QU plane, as a function of position in a direction perpendicular to the stream. Possible interpretations of this pattern will be presented.
A Roadmap for Far-Infrared and Terahertz Interferometry in Space
Matsuo, Hiroshi
Far-infrared and terahertz, astronomy have developed by large ground-based facilities like ALMA and space-born missions like Hershel Space Observatory. But, there is a large gap in angular resolution between these observatories due to atmospheric conditions and telescope diameters. Future space-borne interferometry have been studies, such as SPIRIT and FIRI programs, but not yet feasible in terms of technologies and their scientific returns.I will be discussing international collaboration for future space-borne interferometer missions, including technological developments, ground-based demonstrator programs and possible coordination toward future space missions. In terms of technology, I focus on possible application of intensity interferometry in far-infrared and terahertz frequencies. Independent space telescopes with photon counting detectors could be used to form a large interferometer in space, similar to the very long baseline interferometry (VLBI).Ground-based VLBI is a good example for the international collaboration, which can be extended into terahertz frequencies. High altitude sites in Atacama and Antarctica is good observing sites in terahertz frequencies, and intensity interferometry could be used to make long baseline interferometers under moderate atmospheric conditions. In space-borne intensity interferometry, photon counting detectors could enable background limited observations for long baseline interferometry, which could be applied to resolve exoplanets with their thermal emission.
The mass-metallicity relation of high-z type-2 AGNs
Matsuoka, Kenta
Metallicity is one of the most important clues in understanding the galaxy evolution since metal formations and its enrichments are closely connected with the past star formations in galaxies. The early-recognized relationship between galaxies and their metal contents would be the mass-metallicity relation (MZR), and this correlation has been explored at high redshift (z < 3) by active and earnest near-infrared (IR) observations. However, it should be more challenging to examine the MZR for higher-z galaxies (z > 3.5) since emission lines for metallicity diagnostics shift out of the K-band atmospheric window. Thus, we focus on active galactic nuclei (AGNs) instead of star-forming galaxies. Thanks to their huge luminosity and various emission lines in the wide wavelength range from ultraviolet (UV) to IR, we can easily measure metallicities even in the high-z universe.In this study, we investigated the MZR of type-2 AGNs at 1.2 < z < 4.0 by using high-z radio galaxies (HzRGs) and X-ray selected AGNs. To estimate narrow-line region (NLR) metallicities, we utilized type-2 AGNs of which rest-frame UV emission lines, i.e., CIV, HeII, and CIII], are available. From literature, we collected 67 HzRGs and 13 X-ray selected AGNs as type-2 AGNs, that a few of the later are newly observed with the Subaru Telescope. Furthermore, for 28 of them, we obtained host stellar masses estimated by spectral energy distribution fit: they cover the mass range of 10 < logM/M_Sun < 12. We divided 28 objects into three subsamples with stellar mass bins and estimated their NLR metallicities with a diagnostic diagram of CIV/HeII and CIII]/CIV. In the result, we found that there is a significant positive correlation between stellar masses and NLR metallicities in type-2 AGNs at 1.2 < z < 4.0. This is the first direct evidence that AGN metallicities are related to their host properties. In this meeting, we will present our new results described above and discuss the MZR of type-2 AGNs.
Separation of gas and dust in the winds of AGB stars
Mattsson, Lars
Due to hydrodynamic drag, large dust grains will decouple from a gas flow, while small grains will tend to follow the motions of the gas; the drag is inversely proportional to the Stokes number. Similarly, the drag force radiatively accelerated dust grains exert on the gas is also dependent on the Stokes number. In a stellar-wind context this is often called “drift”, which is referring to the fact that dust and gas may develop different mean-flow velocities. In a spherically-symmetric setting, a mean-flow model of drift is fairly simple. But there are significant 3D effects, which we must take into account. For instance, dust grains of various sizes will cluster and increase the rate of grain-grain interaction. Moreover, due to spatial separation of dust and gas, condensation is likely less effective than in a velocity-coupled case. There are several implications for dust-driven stellar winds which arise from this. One is that the momentum-transfer efficiency (from dust to gas) of large grains may be low as they cluster where the gas is not; another is that the sublimation rate increases as grains are more exposed to the radiation field._x005F Here, we present results from high-resolution box simulations of forced turbulence and apply these results on the problem of dust-driven winds from AGB stars. The simulations represent a first set of idealised models, which aim at understanding the classical particle-in-flow problem for hypersonic stochastic gas dynamics, i.e., type of flows we typically encounter in astrophysics. It is argued that modelling of the dust-driven winds of AGB stars is a problem that may need to be treated in a less holistic way, where some parts of the problem is treated separately in detailed simulations and parameterised back into a less detailed model describing the big picture.
Vortex - multiface unity of astrophysical objects
Matveyenko, Leonid
The fine structure of AGN objects (3C 84, 3C345, 3C454, OJ 287, Cyg A et al.), galaxy NGC 4258 and star formation region of Orion KL at maser emission had been investigated. The structure and cinematics correspond to vortex nature. The matter transferred to the nozzle, an angular momentum is caring away by a bipolar out flower. The ejection velocity is v < 0.1c. The rest of the matter drops out on the forming central massive body. The rotation collimated and accelerated streams, generated ring currents – magnetic fields. The gravitation and magnetic fields extra accelerated and stabilized the structure. The jet moved along the magnetic field - accelerated, the counter jet against – deaccelerated, that determined extra emission of relativistic electrons. The brightness temperature of the nozzles 1013=Tb=1014 K. Bipolar out flower of Cyg A surrounding by low velocity one. A Seifert galaxy 3C 84 is double gravity connected system. In blazar OJ 287 formatted new independent whirlwind. In the Orion KL a matter transferred along two spiral arms to the nozzle. An excess angular momentum is caring away by a bipolar out flower that determined rigid-body rotation. The rotation collimated and accelerated streams. The gravitational field of the central body accelerated and stabilized the structure. Bipolar high velocity spiral out flower of surrounded by two low velocity ones. The structure and cinematics of Orion KL is vortex. The matter transferred along arms to the nozzle and ejected by bipolar out flowers, that determined rigid-body rotation of central part of a disk ? =15 A.U. The period rotation is 170 years. An instability of the outflow caused precession – the spiral structure. Remain of the medium drops on the central body. Rotation of the out flower collimated and accelerated of the out flowers. The ejection velocity v˜5 km/s, which accelerated until 45 km/s at distance 2AU. The objects are self-organized structures, which correspond to gas dynamic solutions.
Magnetically regulated collapse in the B335 protostar ? ALMA observations of the polarized dust continuum emission
Maury, Anaëlle
The role of the magnetic field during protostellar collapse is poorly constrained from an observational point of view, although it could be significant if we believe state-of-the-art models of protostellar formation. We present polarimetric observations of the 233 GHz thermal dust continuum emission obtained with ALMA in the B335 Class~0 protostar. Linearly polarized dust emission arising from the circumstellar material in the envelope of B335 is detected at all scales probed by our observations, from radii of 50 to 1000 au._x005F The magnetic field structure producing the dust polarization has a very ordered topology in the inner envelope, with a transition from a large-scale poloidal magnetic field, in the outflow direction, to strongly pinched in the equatorial direction. This is probably due to magnetic field lines being dragged along the dominating infall direction since B335 does not exhibit prominent rotation._x005F Our data and their qualitative comparison to a family of magnetized protostellar collapse models show that, during the magnetized collapse in B335, the magnetic field is maintaining a high level of organization from scales 1000 au to 50 au: this suggests the field is dynamically relevant and capable of influencing the typical outcome of protostellar collapse, such as regulating the disk size in B335.
A numerical study on the distribution of the tidally stripped matter of the Milky Way satellites
Mazzarini, Matteo
I address the phase-space distribution of the matter stripped from the Milky Way (MW) satellites. From a first N-body test of MW-satellite interaction performed with Gadget 4 (a code from Springel et al., in prep.), I find that the baryonic matter stripped from a satellite has a narrow distribution around the density center of the satellite, while the dark matter (DM) component is more spread around it. Based on this result, I perform a statistical analysis of high-resolution, pure N-body simulations of MW-satellites interaction already run in Moetazedian & Just (2016) following the Aquarius DM-only cosmological simulations (Springel et al. 2008). Second, performing N-body simulations with Gadget 4, I substitute the Aquarius satellites with hybrid baryonic-and-DM satellites (Macciò et al. 2017, Frings et al. 2017) in order to address a similar analysis, also looking at the difference between the deposit of baryonic and dark debris in the MW environment. Preliminary results indicate more stripping happening for DM rather than for baryonic matter. Also, these results suggest on average similar radial density fractions of stripped DM in both simulation sets and a higher density fraction of stripped baryonic matter than DM in the innermost halo. I plan to look at the time required to destroy the nuclei of the satellites. Further simulations are planned, with hyrodynamics and feedback implemented in order to quantify their impact on the stripping process and on the distribution of the streams.
Two views of the massive binary population
McBride, Vanessa
Massive X-ray binaries are the progenitors for gravitational wave sources, but also tracers of star formation visible well outside the Milky Way. While well over a hundred massive X-ray binaries have been identified in the Milky Way, only a handful of radio pulsars with massive companions are known to exist. Such binaries harbouring young pulsars are expected to evolve into massive X-ray binaries. In this work, we attempt to quantify observational selection effects in the context of binary evolution models to understand these different manifestations of the same underlying population of massive binary stars.
Detectors for a Probe-class X-ray Mission to Study Hot Gas in Circumgalactic and Intergalactic Space
McCammon, Dan
Athena will have the capability of making this type of observation, but the required times are very long and that mission will spend most of its time on tasks for which it is much better optomised. An array of superconducting transition edge sensors with 1 mm^2 pixels and ~1 eV resolution over much of the 0.1 – 1 keV energy range would enable a relatively inexpensive probe-class mission with very good sensitivity to faint diffuse emission. A 60 x 60 array of such pixels coupled with a 3.5 m focal length 1 arcmin resolution mirror with an effective area of 1000 cm^2 would have a throughput of ~0.3 cm^2 sr, giving it a mapping speed for emission lines 20x faster than Athena. For absorption spectroscopy, there is the possibility of replacing the four central pixels with an 8x8 array of very small pixels, whose energy resolution could in principle be as good as 0.1 eV. If 0.25 eV at 600 eV can be achieved, this would give a resolving power of 2400 for the oxygen lines and a time to reach a given equivalent width sensitivity only about 2x longer than Athena. Comparing performance requirements with those of Athena as a stand-in for mission complexity: the mirror has 1/15 the effective area, 1/3 the focal length, and 1/12 the angular resolution. The detector array has almost as many pixels, but 1/5 the required maximum resolving power (0.86x for the absorption subarray) and 1/10 the counting rate.
A Massive Stellar Feedback Driven Outflow from the Small Magellanic Cloud?
McClure-Griffiths, Naomi
Feedback from massive stars plays a critical role in the evolution of the Universe by driving powerful winds out of galaxies which can enrich the intergalactic medium and regulate star formation within galaxies. As the most numerous galaxies in the Universe, dwarf galaxies may be important candidates for populating the intergalactic medium with enriched gas. Although star formation rates in dwarf galaxies can be lower than their more massive, starburst counterparts, these low mass systems have small gravitational potential wells and thereby find it difficult to maintain their star-forming material in the presence of intense stellar feedback. Here we use new data from the Australian SKA Pathfinder to show that the nearest low metallicity, gas rich dwarf galaxy, the Small Magellanic Cloud, shows evidence of stellar feedback driven outflows. The outflow is made up cold filamentary material extending up ~1 kpc, with temperatures of T< 500 K and widths as small as 50 pc. We estimate a significant atomic gas mass flux in the range 0.2 - 1 solar mass per year, which may be feeding the Magellanic Stream.
Mass-loss from solar-like and metal-poor stars
McDonald, Iain
Mass-loss prescriptions for solar-mass stars overpredict the number of AGB stars: we have been taking new observations to better calibrate this relationship and understand the processes of mass loss. I will report on our progress into: (1) new evidence showing RGB mass loss is very different to current predictions, (2) the onset of pulsation-driven mass loss once stars reach a pulsation period of ~60 days, (3) the similarities in dust production across a factor of at least 40 in metallicity. I will close by mentioning how this research ties into the NESS and DUSTiNGS surveys and give direction for a new universal mass-loss prescription.
Free-floating planets with K2 (and other topics)
McDonald, Iain
Free-floating exoplanets (FFP) are generated by orbital dynamical evolution, mostly at the start and end of stellar evolution. thus their abundance traces migration patterns within planetary systems. Tension exists between occurrence rates of FFPs derived by OGLE and MOA. I describe our blind search for FFPs in data from the K2 Campaign 9, which targetted the Galactic Bulge, and our attempts to resolve this tension. I will finish by summarising other research into planetary migration, evolution and atmospheric characterisation being performed by the SpearNet Manchester-Thai collaboration.
African Astronomical Society
McGruder, Charles
African Astronomical Society (AfAS) was formed at an IAU symposium in Ouagadougou in December 2010 and was ceremoniously launched in Cape Town, South Africa in April 2011. We describe the structure of the society, its basic philosophy, present what AfAS has accomplished and what its near terms goals are.
Why is the observed distribution of Quasars on the celestial sphere highly anisotropic?
McGruder, Charles
Standard cosmological theory assumes that the matter in the universe is distributed homogenously. Is this assumption correct? Homogeneity implies isotropy. But, it is known that the observed distribution of quasars is highly anisotropic. We show that if we employ supergalactic coordinates and consider only those quasars that have been observed from outer space, then the distribution of quasars as a function of supergalactic latitude is nearly isotropic.
Planetary Magnetism as a Factor of Exoplanet Habitability
McIntyre, Sarah
Discovering life outside the solar system using telescopic observations is the ultimate goal of planetary science. However, while we wait for the next generation of telescopes to come online, we can make use of current data to assess the habitability of a planet using a variety of planetary and astronomical features. This will assist in determining optimal targets for near-future observations of planetary atmospheres.One requirement for habitability is liquid water. Thus far this requirement has only been applied to determining the location of the circumstellar habitable zone (CHZ). However, a strong dipolar magnetic moment may play a significant role in the maintenance of an atmosphere and surface liquid water. Mars’s weak magnetic field is thought to have contributed to the loss of atmosphere and ultimately the absence of liquid water on its surface today. Furthermore, the high D/H abundance ratio in the atmosphere of Venus (120 times that on Earth) indicates large amounts of water loss, potentially attributable to the lack of a substantial magnetic field. On the other hand, Earth’s geodynamo appears to have been remarkably continuous since its inception, which probably occurred shortly after the Moon-forming impact. Therefore, magnetic shielding is a key factor that might significantly contribute to the discussion of whether a terrestrial-like planet will retain its water.This research investigated the dipolar magnetic moment of habitable planets in order to determine whether their magnetospheric protection is sufficient to shield the surface (and the potential liquid water on it) from the effects of X-EUV radiation, coronal mass ejections, cosmic rays, stellar winds and stellar magnetic fields. We show it is likely that only a small fraction of CHZ planets have a sufficient dynamo to sustain liquid water on their surfaces. This result holds even if we assume a low threshold based on the magnetic dipole moment from Earth’s palaeomagnetic records.
Searching for Winds in Starbursting Low-Mass Galaxies from STARBIRDS
McQuinn, Kristen
Mass-loss via stellar-feedback driven outflows is predicted to play a critical role in the baryon cycle of low-mass galaxies. However, observational constraints on warm winds are limited as outflows are transient, intrinsically low-surface brightness events and, thus, difficult to detect. Here, we search for outflows in a sample of eleven nearby starburst dwarf galaxies which are strong candidates for outflows based on their recent star formation histories derived from HST optical imaging of resolved stellar populations. We trace the warm gas phase, which is expected to carry the greatest amount of gas mass, using very deep Hα observations reaching 31 mag arcsec-2 from the KPNO Mayall 4m and the University of Arizona 2.3m Bok telescopes. Despite the deep imaging on galaxies biased towards hosting winds, the observational signature of gaseous outflows is still subtle. Only a fraction of the sample show evidence of winds and these are preferentially found in galaxies with centrally concentrated star formation. We suggest that the concentration of star formation is a predictor for whether a low-mass galaxy will develop a wind. The spatial extent of all detected ionized gas is limited and would still be considered part of the ISM by simulations. We calculate the mass-loading factors of winds based on the Hα emission and compare these to numbers from the latest predictions from hydrodynamical simulations. These observations indicate that (i) the physical extent of warm phase outflows is modest, (ii) most of the mass will be recycled to the galaxy, (iii) the frequency of winds - even in a biased sample - is lower than expected. The sample is part of the panchromatic STARBurst IRegular Dwarf Survey (STARBIRDS) designed to characterize the starburst phenomenon and its impact on the evolution of low-mass galaxies.
The Star Formation History of the Low-Mass Galaxy WLM with JWST from "The Resolved Stellar Populations Early Release Science Program"
McQuinn, Kristen
Kristen McQuinn, Jay Anderson, Martha Boyer, Andrew Cole, Andy Dolphin, Marla Geha, Jason Kalirai, Nitya Kallivayalil, Karin Sandstrom, Daniel Weisz, & Benjamin WilliamsIn the era of HST, the star formation histories of low-mass galaxies derived from resolved star imaging have transformed our understanding of early dwarf galaxy evolution, mass assembly, and the powerful effects of stellar feedback and reionization. Due to distance and exposure time constraints, nearly all studies have been limited to low-mass galaxies co-evolving in the halo of the Milky Way or M31 where environmental processes are also at play.JWST opens a new window in star formation history work by increasing the volume of galaxies that can be efficiently probed. In our JWST "The Resolved Stellar Populations Early Release Science Program", we will obtain extremely deep NIRCam imaging of the gas-rich, extremely metal-poor dwarf galaxy WLM. Located on the outskirts of the Local Group, WLM offers the opportunity to study structure formation and evolution in effective isolation. In this talk, I will describe the planned prototype star formation history study of WLM as well as showcase science with resolved stars that will be made possible with JWST.NOTE TO ORGANIZERS: I am the co-chair of the IAU GA symposium "Dwarf Galaxies: From the Deep Universe to the Present" which is being held simultaneously to the JWST FM. I am excited about the invitation to talk about our ERS program in the FM! The other co-chair of the Dwarf Galaxy symposium, Sabrina Stierwalt, is also part of an ERS program and is submitting an abstract to your FM. Given that we will be running our own symposium, we ask for some flexibility in the scheduling of our talks so that both of us are not absent from the Dwarf Galaxy room at the same time. Thank you for your consideration.
Classical Be stars as Mass Donors in Be/X-ray Binaries
McSwain, M. Virginia
Roughly half of known high mass X-ray binaries contain a Be star secondary. These Be/X-ray binaries (BeXRB) are known to experience a diverse assortment of X-ray outbursts, some of which (Type I) may be associated with a binary periodicity while others (Type II) are seemingly more random. At least some Type II outbursts may be related to the changing disk state of the mass donor, a classical Be star. Here we present properties of the optical variability of classical Be stars to compare their optical outbursts with their X-ray counterparts to look for links behind the two phenomena. While the duration of optical outbursts is consistent with the "zoo" of BeXRB outbursts presented in the preliminary catalog of Kuhnel et al., the shapes of optical outbursts reveal more diversity.
Modelling the extended dust emission around carbon stars observed by Herschel
Mecina, Marko
We give an overview of Herschel PACS far infrared imaging observations of carbon stars and their extended envelopes. Dust structures known from previous infrared missions or expected because of molecular line emission observations are resolved in unprecedented detail. In particular, we study spherically symmetric detached shells. Some of these geometrically thin structures are also discovered in thermal dust emission around stars where there has been no detection so far. The associated stars show deep spectral features due to carbon bearing molecules, indicating a (very) high C/O ratio. This suggests that these objects are all in a very similar, late stage of the AGB, having undergone multiple dredge ups.The remarkable spherical symmetry justifies a straightforward application of 1D models to constrain the properties of the dust envelope, whose modulation in density is a consequence of short epochs of highly increased mass loss and/or wind-wind interaction between outflows of different velocity. We thus perform 1D dust radiative transfer calculations, first based on a parametrised density distribution, and in a more sophisticated approach on a combination of stationary wind models. The spatial information of PACS imaging provides crucial constraints. Emphasis is put on evaluating various dust grain setups. We show how the different grain parameters as well as the degeneracy between them affect the models and to which extent this prohibits accurate determination of the shell characteristics.
Infrared extinction in Orion A
Meingast, Stefan
Despite numerous studies in recent years, the characteristics of the infrared extinction law remain a controversial topic. Examples for open debates are the origin of the often-observed gray distribution of the MIR portion from ~3 to ~6 µm, as well as the the universality of the extinction law in the NIR regime (~1 to 2.5µm). Most recent studies, however, are relying on measurements toward the galactic center. There, multiple, physically separate, regions overlap along the line-of-sight. As a consequence, physical conditions along the observed direction can hardly be controlled, therefore biasing attempts to derive general characteristics of the extinction law.In this talk I will present new results on the infrared extinction law from 1 to 25 µm toward the Orion A star-forming complex. The Orion A molecular cloud is situated in the direction of the galactic anti-center, is located below the galactic plane, and furthermore appears to be well-isolated from other star-forming regions. At the same time, the cloud is relatively nearby (400pc) and features a large dynamic range in column densities. Moreover, the complex hosts a massive cluster, along with many other isolated star-forming events. Together, these conditions make it ideal to probe the extinction law in a controlled environment.Based on a statistically refined analysis, I will show that the extinction law does indeed vary across the molecular cloud. In particular, and in contrast to many results in the literature, this study finds direct evidence that the NIR portion is not universal and also determine the MIR portion of the extinction law to be variable. These variations show a strong spatial correlation where regions far away from the massive stars show a distinctly different extinction law compared to the immediate warm environment close to the cluster. Our evidence therefore points to the conclusion that feedback from the massive stars in the cluster can have a direct impact on dust grain properties.
Solar System Stereoscopy with Hubble and James Webb Space Telescopes
Meinke, Bonnie
The two most powerful optical/IR space telescopes in history -- NASA's Hubble and James Webb Space Telescopes -- will be in space simultaneously in the early 2020s timeframe. We have a unique opportunity to leverage the 1.5 million kilometer separation between the two telescopes to obtain simultaneously captured stereoscopic images of asteroids, comets, moons, rings, and planets in our Solar System. The studies of various objects could benefit from such spectroscopic observations. Here, we present the technical requirements for acquiring stereoscopic images of Solar System objects, given the constraints of the telescopic equipment and the orbits of the target objects. We present a handful of examples that we hope will serve as a conversation starter with members of the solar system community who might propose for such observations. As an added bonus, the recent resurgence in stereo-3D movies and the recent emergence of stereo-enabled mobile devices and of virtual reality headsets means that these stereoscopic images of solar system objects could engage the public on an unprecedented scale. Discussions about how to engage the public with such observations are also welcome!
Uncovering how Lyman alpha photons escape by studying dwarf galaxies in the near-by universe.
Melinder, Jens
The Lyman alpha reference sample (LARS) is a major multiwavelength imaging andspectroscopic campaign of star-forming dwarf galaxies, as well slightly moremassive systems, using the Hubble Space Telescope and ground-based telescopes.The aim of this survey is to probe what physical conditions and processesregulate the emission of Ly alpha radiation on local and global galacticscales. The fact that Ly alpha is a resonant line makes it optically thick evenat relatively low neutral hydrogen column densities, this means that theradiative transport of Ly alpha photons through galaxies is a complex problemwhere the structure, kinematics and dust content, and neutral hydrogen contentof the interstellar medium all contribute to the process. In this talk I willpresent unique HST Lyman alpha maps and FUV spectroscopy of 44 galaxies within theLARS sample. Roughly half of the sample are dwarf galaxies (with stellar masses lower than one billion solar masses) and they are all highly star-forming. These galaxies show, on average, a higher Lyman alphaescape fraction than the rest of the sample. By comparing global observables(e.g., SFR, extinction, Lyman alpha line profile, Lyman alpha morphology, HI mass)to the Lyman alpha escape fraction I will try to explain why the physicalconditions in these dwarf galaxies makes it easier for Lyman alpha photons to escape. Detectingdwarf galaxies at high redshift is often only possible by Lyman alpha emission,which makes understanding how the emission escapes critical for interpretingthe observations in a broader context (e.g., galaxy evolution, re-ionization).
MUSER: on the way to fundamental and applied problems of solar physics
Melnikov, Victor
Chinese spectral radioheliograph MUSER, a radio synthesis imaging telescope dedicated to observe the Sun, operates on multiple frequencies in dm to cm range. The observing radio frequency bands are 400 to 2000 MHz, 64 channels (MUSER-I: 40 x 4.5m antennas) and 2 to 15 GHz, 32 channels (MUSER-II: 60 x 2m antennas). The double spiral array includes 40 parabolic antennas with diameter 4.5m (MUSER-I) and 60 antennas with diameter 2m (MUSER-II) with the maximum baseline of 3 km. Observations are conducted in both circular polarizations R and L with time resolution of 25ms/200ms, and highest angular resolution of 12"/1.6" for MUSER-I and MUSER-II, respectively. These characteristics of MUSER allow it to be used in solving the fundamental problems of physics of solar flares and CMEs, the heating of the solar corona, as well as in solving some applied problems of physics of solar-terrestrial relationships. Methods of radiophysics allow us to obtain information that is unattainable in other areas of the electromagnetic spectrum. This applies primarily to data on the magnetic field on coronal heights and electrons of the mildly relativistic energies. In this report, we will confine ourselves to considering the potential of MUSER in relation to studies of physical processes in coronal magnetic loops and magnetic flux ropes. The ability of MUSER to measure Stokes I and V parameters simultaneously at a large number of frequencies in a wide band is of fundamental importance. In particular, polarization maps may give data on the orientation of coronal magnetic field and evolution of magnetic loop twisting. The developed methods of radio-diagnostics make it possible to determine the localization of the energy release and acceleration of electrons and the type of pitch-angular anisotropy of accelerated particles in flash loops. And this information, in turn, is the key to selecting more adequate mechanisms and acceleration models among the many currently proposed.
Rotating stellar models of low- and intermediate-mass stars from the pre-main sequence up to the AGB
Mendes, Luiz Themystokliz Sanctos
We report on rotating stellar evolutionary models of low- and intermediate-mass stars computed with the ATON 2.3 stellar evolution code. Rotation has been implemented by using the Kippenhahn & Thomas (1970) method in the approximation by Endal & Sofia (1986), which relies on the deformation of the star's equipotential surfaces due to rotation provided that the total (gravitational plus rotational) potential is conservative. This method was already used in the ATON 2.3 code in the context of low-mass stars during the pre-main sequence and main-sequence stages, and now is being extended to intermediate mass stars and evolution stages up to the asymptotic giant branch (AGB). Some preliminary results about the evolution of some typical rotating models in the range of 1 to 5 solar masses from the pre-main sequence to the AGB are presented and discussed.
A common-envelope wind model for SNe Ia
Meng, Xiangcun
Here, we propose a new version of the SD model in which a common envelope (CE) is assumed_x005F to form when the mass-transfer rate between a carbon–oxygen white dwarf (CO WD) and_x005F its companion exceeds a critical accretion rate. In our model, helium flash and hydrogen-burning phases adjust themselves just as they do in a TPAGB star. In the CEW model, the SN Ia may explode in CE, supersoft X-ray source and recurrent nova phases. The CEW model shares many of the merits of the previous model while avoiding some of its shortcomings. Our model suggeste that SN 2002cx-like and SN Ia-CSM objects would share the same origin.
The origin and evolution of UV-upturn elliptical galaxies in Hubble Frontier Fields at z>0.9
MENG, XIAOLEI
The ultraviolet (UV) upturn phenomenon in elliptical galaxies has attracted much attention as it violates the common understanding that early type galaxies are mostly comprised of old stars with little UV radiation. Although there have been several recent samples of UV-upturn detections at low redshift (z<0.5), the analysis at high z is still lacking. In this work, we try to address this by measuring UV-upturn elliptical galaxies at 0.9<z<2.5 in="" 6="" cluster="" fields,="" using="" the="" ultra="" deep="" broad-band="" photometry="" given="" by="" hubble="" frontier="" fields="" project.="" ancillary="" data="" sets="" are="" also="" taken="" into account,="" such="" as="" clash="" data,="" ultra-deep="" ks-band="" imaging="" of="" hff="" (kiff="" project),="" etc.="" these="" span="" 14-20="" filters="" and="" cover="" far="" uv="" to="" h="" band="" for="" target="" redshift="" range,="" offering="" more="" accurate="" photometric="" estimation="" sed="" fitting.="" meanwhile,="" spectroscopic="" acquired="" grism="" lens-amplified="" survey="" from="" space="" (glass)="" multi="" unit="" explorer="" (muse)="" observations="" included="" analysis="" deriving="" spectroscopy="" excluding="" star-forming="" galaxies="" mistaken="" passive="" ones.="" we="" obtained="" distribution="" uv-upturn="" elliptical="" over="" compared="" our="" observational="" results="" with="" theoretical="" predictions="" binary="" star="" model="" explaining="" origin="" evolution="" this="" phenomenon. especially="" found="" that="" there="" exists="" a="" few="" at="" z="" >2="" which="" hard="" be explained="" on="" its="" own.="" importantly,="" managed="" explore="" specific="" radiative="" zone="" galaxy="" radius="" sample.<="" z<2.5><="" p=""> </z<2.5></z<2.5></z<2.5></z<2.5></z<2.5>
Long Period Variables in dwarf Irregular Galaxies of the Local Group
Menzies, John
In a survey of Local Group galaxies conducted at SAAO, we have included a number of dwarf irregular galaxies. We discovered some remarkable long period variables in the galaxies, NGC 6822, SagDIG and IC1613, and we now have identified more than 10 Miras in WLM and at least 7 in NGC 3109. We discuss the distribution of periods and the implications for theoretical modelling of these stars in the late stages of AGB evolution.
Red supergiants in the Inner Disk of the Milky Way.
Messineo, Maria
Red supergiants (RSGs) are key ingredients of spiral galaxies, they trace the spiral arms,and chemically enrich the interstellar medium by losing mass at high rates andexploding as supernovae. RSGs are the brightest stars in the Disk seen atinfrared wavelengths, being young and cold objects with typical luminosity above 10,000 that of our Sun.Due to our position on the Disk, dust obscuration, and poor distances, their identificationis difficult and their census is highly incomplete, with about five hundred RSGs currentlyreported in the literature. Recently, about 100 new inner Galactic late-type stars wereselected from the GLIMPSE I North catalog, and spectroscopically observed with thesurprising detection rate of RSGs of 61%, and an increase by 25% in the number ofpreviously known RSGs in the searched area. We are currently photometricallymonitoring the new sample with ANDICAM at CTIO.
Gamma-ray Bursts: A Brief Survey of the Diversity
Meszaros, Attila
The separation of the gamma-ray bursts (GRBs) into short/hard and long/soft subclasses, respectively, is well supported both theoretically and observationally. The long ones are coupled to supernovae type Ib/Ic - the short ones are connected to the merging of two neutron stars, where one or even both neutron stars can be substituted by black holes. These short GRBs - as merging binaries - can also serve as the sources of gravitation waves, and are observable as the recently detected macronovae. Since 1998 there are several statistical studies suggesting the existence of more than two subgroups. There can be a subgroup having an intermediate durations; there can be a subgroup with extra long durations; the long/soft subgroup itself can be divided into two subclasses with respect to the luminosity of GRBs; etc. The authors with other collaborators provided several statistical studies in this topic. This topic of the GRB-diversity is shortly surveyed in this contribution.
A Top-Light IMF in Low Surface Brightness Environments
Meurer, Gerhardt
We use direct imaging with the Hubble Space Telescope to construct the main-sequence luminosity function of five nearby dwarf galaxies and spiral galaxy outskirts. The luminosity functions are consistent with the paucity of O stars relative to B stars inferred from Halpha and ultraviolet imaging observations. Hence, the observations disfavour the interpretation of low Halpha/FUV ratios as being due to escaping ionizing photons and instead favour an Initial Mass Function deficient in high mass stars compared to the canonical Salpeter IMF.
The Formation of Spectroscopic Massive Binaries via Early Disk Fragmentation and Migration
Meyer, Dominique
Accretion-driven luminosity outbursts are a vivid manifestation of variable mass accretion onto protostars. _x005F We present three-dimensional gravitation-radiation-hydrodynamics simulations of pre-stellar core collapse, star, and disk formation. We find that accretion disks of young massive stars violently fragment without preventing the (highly variable) accretion of gaseous clumps onto the protostars. This episodic accretion of clumps is accompanied by luminous outbursts. Furthermore, while acquiring the characteristics of a nascent low-mass companion, some disk fragments migrate toward the central massive protostar with dynamical properties showing that their final Keplerian orbits resemble that of a close massive binary system. _x005F We predict the fragmentation of massive circumstellar accretion disks as a viable road to the formation of spectroscopic massive binaries and the recently observed strong accretion bursts in high-mass star forming regions.
The continuing mystery of multiple spectral components in Jets from Black Holes
Meyer, Eileen
One of the first things that astronomers usually determine for any new astrophysical source class is the emission process generating the radiation -- thermal, synchrotron, inverse Compton, Bremsstrahlung, etc. Identifying these processes is critical to using the EM observations to probe the physical environments of very distant objects. Despite the fact that jets from black holes were first understood to exist over 40 years ago, we are still in ignorance about many primary aspects of these systems -- including the radiation mechanism at high energies, the particle makeup of the jets, and how particles are accelerated, possibly to energies as high as 100 TeV and hundreds of kpc from the central engine. I will discuss how this mystery first really got going with the launch of Chandra in 1999, and show how high-resolution observations with observatories like Hubble and ALMA have continued to add pieces to the puzzle -- sometimes seemly solving a problem, and other times opening a new one. I will conclude with some perspectives on how new observatories, like the Chandra successors AXIS and Lynx, can help us solve these long-open questions in jet physics.
Tycho-Gaia vs Gaia DR2
Michalik, Daniel
The second Gaia data release (Gaia DR2; April 2018) contains five parameter astrometry for more than one billion stars. The underlying model assumes all stars to exhibit single star behaviour, i.e. to follow a uniform linear proper motion trend._x005F For 2 million stars we can obtain long temporal baseline proper motions by combining Gaia DR2 data with Tycho-2 positions from 1991.25, similar to the Tycho-Gaia Astrometric Solution (TGAS) in Gaia DR1. We present a comparison of instantenous Gaia DR2 proper motions with DR2-based Tycho-Gaia long-term trends, and a goodness-of-fit measurement that describes the agreement between the datasets. The latter allows us the detection of candidates for stars hosting stellar or sub-stellar companions fainter than the Gaia detection limit.
The shapes of fine fragments with several tens of micrometers in impact experiments and influence of petrographic textures: Comparison with Itokawa regolith particles.
Michikami, Tatsuhiro
The shape distribution of Itokawa particles less than 120 µm is distributed around the mean values of the axial ratio 2: v2: 1, which is similar to those of laboratory impact fragments larger than several mm in catastrophic disruption. Thus, the Itokawa particles are considered to be the impact fragment on the asteroid surface. However, there have never been laboratory impact experiments investigating the shapes of fine fragments less than 120 µm, and little is known on the relation between the petrographic textures and the shapes of fine fragments. In this study, we have primarily investigated the shapes of fine fragments smaller than 120 µm (S-sized fragments) created in impacts in the range from cratering to catastrophic disruption (Q = 230 to 8540 J/kg in basalt targets; Q = 1930 and 13540 J/kg in L5 chondrite targets) using synchrotron radiation-based microtomography at SPring-8. The shape distributions of S-sized fragments of basaltic and L5 chondrite targets are similar, distributed around the mean values of the axial ratio 2: v2: 1. The shape distributions of these small fragments are independent of Q which means that the degree of target fragmentation does not affect their shapes.Moreover, we found that concluded the petrographic textures and the crystal grain boundaries do not significantly affect the shapes of S-sized fragments by impacts. On the other hand, in thermal fatigue caused by the day-night temperature cycles on an asteroid surface, the petrographic textures and the crystal grain boundaries would affect the shapes of the fragments (Molaro et al., 2015). As the shape distribution of the Itokawa particles is similar to those of S-sized fragments from impacts, we therefore conclude that the Itokawa particles have not been produced by thermal fatigue and are likely to be impact fragments on the asteroid surface.
Morphological study of a large sample of extragalactic radio sources for revelation of radio jets
Mickaelian, Areg
With an improved cross-correlation technique, we have matched two largest radio catalogs at 1.4 GHz (21 cm), NVSS and FIRST to improve positions and photometry, to reveal radio variability and check with optical variability, to study the radio structure and optical morphology of sources, to classify radio sources into FRI and FRII types, and to reveal jets and additional features. NVSS (Condon et al. 1998) contains 1,773,484 sources and FIRST (Helfand et al. 2015) contains 946,432 sources and have better positional and photometric accuracy (5 arcsec and 1 mJy, respectively). As a preliminary result, we obtained 556,282 common sources. 6301 of them show obvious signs of variability having > 50 mJy differences between fluxes in NVSS and FIRST. For these sources we have made multiwavelength (MW) investigations in all wavelength ranges aimed at finding relations between the radiation fluxes in different bands for different types of sources (blazars, QSOs, other AGN, and starbursts). Another possibility that appeared after having cross-correlated NVSS/FIRST sources, is the study of radio morphology. Given that FIRST resolution is higher, very often we have 2-4 FIRST associations within 30 arcsec corresponding to 1 NVSS source. In such cases the central source is considered as the core, and 2 farther bright sources are considered as radio lobes. Depending on the flux ratio of the central source and the lobes, we have preliminarily classified sources to FRI and FRII. On the other hand, the 4th component, when available, may be regarded as a jet, and very often it appears not far from the core. We match these results with radio contours to verify candidate jets, as well as we check these sources for radio variability. We identify NVSS/FIRST sources having 4 FIRST components and radio variability, a highly reliable sample for revelation of radio jets.
Morphological study of a large sample of extragalactic radio sources for revelation of radio jets
Mickaelian, Areg
With an improved cross-correlation technique, we have matched two largest radio catalogs at 1.4 GHz (21 cm), NVSS and FIRST to improve positions and photometry, to reveal radio variability and check with optical variability, to study the radio structure and optical morphology of sources, to classify radio sources into FRI and FRII types, and to reveal jets and additional features. NVSS (Condon et al. 1998) contains 1,773,484 sources and FIRST (Helfand et al. 2015) contains 946,432 sources and have better positional and photometric accuracy (5 arcsec and 1 mJy, respectively). As a preliminary result, we obtained 556,282 common sources. 6301 of them show obvious signs of variability having > 50 mJy differences between fluxes in NVSS and FIRST. For these sources we have made multiwavelength (MW) investigations in all wavelength ranges aimed at finding relations between the radiation fluxes in different bands for different types of sources (blazars, QSOs, other AGN, and starbursts). Another possibility that appeared after having cross-correlated NVSS/FIRST sources, is the study of radio morphology. Given that FIRST resolution is higher, very often we have 2-4 FIRST associations within 30 arcsec corresponding to 1 NVSS source. In such cases the central source is considered as the core, and 2 farther bright sources are considered as radio lobes. Depending on the flux ratio of the central source and the lobes, we have preliminarily classified sources to FRI and FRII. On the other hand, the 4th component, when available, may be regarded as a jet, and very often it appears not far from the core. We match these results with radio contours to verify candidate jets, as well as we check these sources for radio variability. We identify NVSS/FIRST sources having 4 FIRST components and radio variability, a highly reliable sample for revelation of radio jets.
Study on the Korean Astrolabe of Ryu Geum
Mihn, Byeong-Hee
We investigated the Korean astrolabe with a diameter of 17 cm made by Ryu Geum (1741~1788), a Joseon Confucian scholar, and dedicated to Yoon, Yak-Am, who was probably his teacher. In the mid-17th century, an astrolabe was first introduced to Joseon, called ‘Hongae-tongheon-ui,’ which was given its name by Nam, Byeong-Cheol (1817~1863) after the Hungai tongxian tushuo edited by Chinese Mathematician Li Zhi-zao (1565~1630). Ryu’s astrolabe is now owned by the Museum of the Silhak in Korea, reimported with some loss from Japan. In this study, we introduce Ryu’s astrolabe manufactured for 38° latitude. We express all circles on the front and back mother with trigonometric functions derived from geometry. The radii of these circles are determined by its latitude, obliquity of ecliptic, altitude and so forth. This Korean astrolabe has a quintuple part for night-time, not twelve parts, based on the Joseon nocturnal time system. This astrolabe divides the shadow square (or box) into 48 like an Islamic instrument, not 180, in a half turn. However, it has 360° in scales of degrees and 96 quarters a day (i.e. 24 hours a day). 11 star pointers of Ryu’s Astrolabe cling to the branch of rete, which has the ecliptic circle off the center. In this study, we will discuss a comparison of our calculations with Ryu’s astrolabe measurements on the accuracy of circle drawing. We think that our findings will contribute to efforts to remanufacture and restore the Korean astrolabe.
Spectroscopic and photometric survey of the northern sky: Towards understanding of the Galactic chemical environment in the Solar vicinity
Mikolaitis, Šarunas
A spectroscopic characterisation is available for less than 30% of bright stars in the Solar neighbourhood leaving us with missing information about the Galactic environment in this region of space. This is very unfortunate for astero-seismic and planetary studies. For example, new space missions (e.g. NASA-TESS or ESA-PLATO) will perform an in-depth analysis of large fields of the sky-sphere searching for extraterrestrial planets around bright stars that are similar to the Sun. In order to achieve thier goals, the space missions need a full characterisation of observational objects. However, large spectroscopic surveys that have the greatest input in studying properties of Solar environment and far beyond, usually exclude brightest nearby stars. In this study, we aim to observe high-resolution spectra for all bright (V < 8 mag) and cooler than F5 spectral class dwarf stars in the northern-most fields of the sky sphere in order to determine their precise atmospheric parameters and abundance patterns with spatial and temporal distribution. We use high-resolution spectra obtained with the VUES spectrograph mounted on the 1.65 m telescope at the Moletai Astronomical Observatory of the Institute of Theoretical Physics and Astronomy, Vilnius University. High-resolution spectra (R = 60 000) were observed in two fields with radius of 20 degrees towards the northern ecliptic pole which will be targeted by the TESS and PLATO space missions. For 73% of the observed stars we spectroscopically determined the main atmospheric parameters and chemical properties for the first time. We used magnesium to iron and magnesium to manganese ratios for tagging Galactic substructures in the solar vicinity for further investigations.In this contribution, we put together stellar atmospheric parameters and chemical compositions with the derived ages and orbital parameters to draw a chemical picture of the very close Solar vicinity.
IMPACT OF YARKOVSKY EFFECT AND MEAN-MOTION RESONANCES ON MAIN BELT ASTEROID'S TRANSPORT
Milic Zitnik, Ivana
The subject of our research is interaction between the mean motion resonance (MMR) and the Yarkovsky effect. This interaction occurs when an asteroid due to the changes of its orbital semimajor axis (caused by the Yarkovsky effect) reach the resonance. The resonance induces a periodic oscillations in the asteroid's semimajor axis around its center. The Yarkovsky effect exactly causes the permanent (secular) evolution of the orbital semimajor axis. As a result of their interaction, the mean semimajor axis drift speed is modified with respect to the one caused solely by Yarkovsky. One of the main goals of this investigation was to study this interaction, and to define how the time that an asteroid spend in the MMR depends on some characteristics of this resonance, as well as of the asteroid itself. So far, the impact of the resonance on the semimajor axis drift speed has not been studied to that extent neither from that point of view. We established our findings about the effect of 11 two-body MMRs with Jupiter, on the mobility of an asteroid's semimajor axis caused by the Yarkovsky effect. This study was accomplished using numerical integrations of test asteroids. The obtained results revealed that MMRs could either speed up or slow down the drift in the semimajor axis. This allowed us to determine the distribution that represents the best data obtained for time delays, dtr, caused by the resonances on the mobility of an asteroid. Also, we established the certain functional relation that describes dependence of the average time lead/lag <dtr> on the strength of the resonance, SR, and the semimajor axis drift speed, da/dt. Also, we analyzed how the time spent inside the resonance depends on orbital eccentricity, and proposed the relation that taking this parameter into account as well. As the Yarkovsky effect scales as 1/D, an important consequence of this relation was that average time lead/lag <dtr> is directly proportional to the diameter D of an asteroid.</dtr></dtr>
Some properties of motion of resonant asteroids with very slow Yarkovsky drift speeds
Milic Zitnik, Ivana
We investigated the effect of mean motion resonances (MMRs) with Jupiter, on the mobility of an asteroid's semimajor axis caused by the Yarkovsky effect. We observed only asteroids that entered and exited from the MMR. One of the main goals of our research was to study this interaction between gravitational and non-gravitational force, and to define how the time that an asteroid spend in the MMR depends on some characteristics of this resonance and of the asteroid itself. In the begining, for 9 (out of 10) values of Yarkovsky drift speed (da/dt) that we analyzed (in range from 0.00004 AU/Myr to 0.001 AU/Myr), we found that time increases when strength of resonances (SR) is increasing and vice versa. For our the slowest Yarkovsky drift speed, an opposite trend is observed: test asteroids very fast move across MMRs in comparing with resonant asteroids with da/dt larger and equal than 0.0001 AU/Myr (our the second smallest da/dt). This results might indicate that below some limiting value of da/dt, objects typically quickly jump across the MMR. Analyzes of additionally four values smaller than 0.00004 AU/Myr (0.00003, 0.00002, 0.00001, 0.000007 AU/Myr) were necessary and have confirmed our previous results. Asteroids very fast cross the MMR in this way: with smaller speed da/dt we got smaller time spent in the resonance. We concluded that limit value of Yarkovsky drift speed exists between 0.00004 and 0.0001 AU/Myr, approximately on 0.00007 AU/Myr (we took medium of previous interval). Possible explanation about results of our research is that MMRs have more powerfully influence than very slow Yarkovsky drift speeds on motion of resonant asteroids. Also, the mentioned effect on time is more expressed in stronger MMR because combination of larger oscillation in semimajor axis values with very slow da/dt helps resonant asteroid to reach easier border of MMR and came out earlier from MMR.
Searching for Methylamine in Orion-KL using ALMA archival data
Minamoto, Harumi
Methylamine (CH3NH2) is the simplest amine and thought to be potential interstellar precursors to the amino acid glycine (NH2CH2COOH). It is confirmed by the experiment that the reaction of methylamine with CO2 in water ice yields glycine under UV irradiation. In terms of exploration in the Solar system, this molecule has been detected in comet 81P/Wild 2 in the Stardust mission and comet 67P/Churyumov-Gerasimenko in the Rosetta mission. However, a robust detection of methylamine has been reported only in Sgr B2(N) while a variety of complex organic molecules have been detected by radio observation in molecular clouds so far. To search for methylamine, we focused on the Orion Kleinmann–Low nebula (Orion-KL), which is known as the nearest high-mass star-forming region and one of the most prolific sources of line emission of a variety of complex organic molecules. Because of its richness in chemical composition, it also has been regarded as a suitable target for molecular line survey in the interstellar medium. We used the ALMA Science Verification(SV) data and Cycle 2 archival data toward Orion-KL at Band 6, and several candidate spectral features of methylamine were found. These exhibit a compact emission at the center of the Hot core, with the signal-to-noise ratio of 10 and Vpeak ~ 5 km/s, although the possibility of contamination by other molecular line emissions is not excluded. Also the frequency coverage of the Cycle 2 data is not wide enough so that the transition lines of this species, which are expected to be relatively strong, cannot be identified in the data. Therefore, we need to merge the SV data to cover a wider frequency. In order to obtain the precise intensity of the lines, we performed statistical analysis to subtract the continuum emission.For the robust detection, we will discuss the physical state of the candidate lines, such as the distribution of temperature and column density, and a rotational diagram analysis.
Signatures of UV radiation around low-mass protostars in Serpens
Mirocha, Agnieszka
A new-born protostar forms in dense core deep inside molecular cloud. Due to high extinction in the optical range, observations at long-wavelengths are needed. In particular, submillimeter spectra include rotational lines of key molecules which are useful probes of physics and chemistry around low-mass protostars. Here,we analyse molecular emission from the Serpens Main star forming regions using IRAM 30 m single dish telescope. HCN, CN, and CS emission is modelled using radiative transfer code RADEX to determine the gas physical conditions and molecular abundances. The presence of UV radiation in these regions isidentifiedand compared to models of dense envelopes irradiated by UV photons. Thus, we gain new understandings of chemical and physical processes around low-mass protostars.
New evidences for the North Polar Spur as the kpc-scale jet with extended cocoon
Miroshnichenko, Alla
The analysis of the jet hypothesis for the North Polar Spur as the Galaxy jet with extended cocoon is carried out. Befor we have derived the main physical parameters (the magnetic field strength, the spectral index, the radio luminosity, the jet propagation velocity, the characteristic age) of the North Polar Spur at the base of observed Galactic background at the low-frequency band. For the further testing of the jet hypothesis we derive some additional estimates, including the value of the mass accretion rate for the supermassive black hole at the Galactic centre and the value of the total energy of the North Polar Spur. We consider that the observed Galactic radio background is, in the main, the radio emission of extended cocoons of both possible Galactic jets (the North Polar Spur (jet) and the South spur (counterjet)). We have examined the features of the possible Galactic kpc-scale jet with extended cocoon and known kpc-scale Galactic winds and superbubbles.
Analysis of the parameters of the DM Halo around the non-radially oscillating disk
Mirtadjieva, Karamat
We study the dependence of the evolution of a nonlinearly nonradially disk oscillating in its plane, depending on the basic parameters of the DM Halo. The DM Halo stabilizes the instabilities in the plane of the disk, but destabilizes its vertical oscillations. The global disk structure is dependent strongly on the mass and shape of the DM Halo. The evolutionary dependences of the oscillation process versus the indicated parameters of the DM Halo are constructed.
Why are classical bulges more common in S0 galaxies than in spiral galaxies?
Mishra, Preetish
We carry out a comparative study of the bulge and global properties of a sample of spiral and S0 galaxies in a fixed environment. Our sample is flux limited and contains 262 spiral and 155 S0 galaxies drawn from the Sloan Digital Sky Survey. We have classified bulges into classical and pseudobulge categories based on their position on the Kormendy diagram. Dividing our sample into bins of galaxy stellar mass, we find that the fraction of S0 galaxies hosting a classical bulge is significantly higher than classical bulge fraction seen in spirals even at fixed stellar mass. We have compared the bulge and the global properties of spirals and S0 galaxies in our sample and find indications that spiral galaxies which host a classical bulge, preferentially get converted into S0 population as compared to pseudobulge hosting spirals. By studying the star formation properties of our galaxies in the NUV - r color-mass diagram, we find that the pseudobulge hosting spirals are mostly starforming while the majority of classical bulge host spirals are in the green valley or in the passive sequence.As an answer, we suggest that some internal process, such as feedback from the central black hole etc., quenches these classical bulge hosting spirals and transforms them into S0 galaxies, thus resulting in the observed predominance of the classical bulge in S0 galaxies.
Evolution of Isophote Shapes of Early-Type Galaxies In Massive Clusters from z~1
Mitsuda, Kazuma
Galaxy clusters provide unique environments for studying evolution of early-type galaxies (ETGs) because there are large number of ETGs including very massive ones such as central and cD galaxies, and galaxies evolve within the cluster once they enter into such an environment. Exploiting this advantage, we compare the isophote shape parameter a4 between z~1 and 0 as a proxy for dynamics to investigate the epoch at which the dynamical properties are established. We create cluster ETG samples with log(M*/Msun)>=10.5 with spectroscopic redshifts. We have 130 ETGs at z~1 from the Hubble Space Telescope Cluster Supernova Survey and 355 ETGs at z~0 from the Sloan Digital Sky Survey. We find similar dependence of the a4 parameter on stellar masses at z~1 and 0; the main population changes from disky to boxy at a critical mass of log(M*/Msun)~11.5 with the massive end dominated by boxy ones. The disky ETG fraction is consistent between these redshifts. Although uncertainties are large, the results suggest that the isophote shapes and probably dynamical properties of cluster ETGs are already in place at z>1 and do not significantly evolve at z<1, despite significant size evolution. The constant disky fraction implies that the processes responsible for the size evolution are not violent enough to convert the dynamical properties. The boxy shapes of massive ETGs in z~1 clusters can be originated from major mergers at z>1 when the velocity dispersion of clusters are small. We are now developing a next generation adoptive optics system for the 8-m Subaru telescope aiming to obtain spatially resolved properties of high-redshift galaxies such as stellar kinematics and stellar population which will provide new insights into evolution of galaxies and clusters at high redshifts.
Fractal basins of attraction in the autonomous restricted four-body problem with the variable mass
Mittal, Amit
We numerically investigated the circular autonomous restricted four-body problem where the fourth particle of variable mass is moving under the gravitational influence of three bodies always known as primaries which move in_x005F circular orbits around their their common center of mass in such a way that their configuration remains always an equilateral triangle. The effect of the variable mass parameter on the existence as well as on the locations of the libration points are investigated. The parametric variation of the position of libration points and zero velocity curve are also revealed when the variable mass parameter increases. Moreover, the Newton-Raphson basins of convergence corresponding to libration points are unveiled numerically when the variable mass parameter increases. The correlations between the basins of attraction and the required number of iterations associated with them are also evaluated and discussed numerically. The obtained results strongly suggests that the study of the evolution of the attracting domains of the proposed dynamical system is worth studying in spite of their complexity.
Astronomy education initiative in senegal
Modou, MODOU
in this work, we describe eight years education approach for developping astronomy for developpment in numerous region in senegal, where still no teaching programme is available in the five local universities. Dual Optical Telescopes equiped with CMOS camera and various Galleoscopes were used for demonstration purposes on remote area for promoting astronomical observation of planets and the natural satellite of our Earth. in total around 120 schools and 15 conferences were organized for spreading widely our programme with the help of SAOImage DS9 software we were able to download usefull astromical images and we introduced image processing and applied statistics in astrophysics.
Resolving the Origin of GAMA’s Enigmatic Dwarf Galaxies
Moffett, Amanda
The GAMA survey’s dwarf “Little Blue Spheroid” (LBS) galaxy class has a complex identity, combining star formation typical of spiral galaxies with elliptical-like morphology. Using deep, high-resolution imaging from VST KiDS and the Bayesian, two-dimensional galaxy profile modeling code ProFit, we examine the detailed structure of LBSs and find structural properties similar to low-mass elliptical galaxies. In contrast to this apparent spheroid-like structure, SAMI survey integral field spectroscopy data indicate that LBS dynamics are rotation dominated, or disk like. We also find that LBSs typically occupy low group halo mass environments similar to those of low-mass spiral galaxies. Finally, we consider potential origin scenarios for a population with this unexpected combination of properties, which include star-forming, field-environment precursors to dwarf ellipticals, products of dwarf-dwarf mergers, and transitional dwarf starbursts akin to blue compact dwarf galaxies.
Impact of AGB stars on their circumstellar environments
Mohamed, Shazrene
Recent high-resolution, high-sensitivity observations, e.g., with Herschel, ALMA, and SPHERE, have given us dramatic new views of cool, evolved giants and their circumstellar environments; revealing dusty arcs, bubbles, dense shells, spirals, and equatorial and bipolar outflows. In this talk, we present 3D simulations of the interaction of the outflows of cool giants with nearby (sub-) stellar companions and the interstellar medium. We discuss the physical processes that govern the origin and evolution of the observed complex structures, and the implications for the wide range of related systems, e.g., symbiotic binaries, detached shell sources, runaway stars and (proto-)planetary nebulae.
NOC activities at Bangladesh
Mohammedy, Farseem
The poster present the NOC activities at Bangladesh
The Gaia Archive Visualisation Service
Moitinho, André
Gaia, with its astrometric data of unprecedented quality is widely considered a transformative endeavour in Astronomy. The huge data volume delivered in the Gaia data releases is also transforming the way data exploration is done.With almost 1.7 billion sources as of Data Release 2, the information content of the Gaia Archive is unimaginable. In this poster we present the Gaia Archive Visualisation Service (GAVS). GAVS is both a platform for interactive visual exploration of the Gaia data; and a provider of intelligible visual representations of the enormous information content of the archive. Examples of these representations are the all sky density and flux maps which became the iconic images of the Gaia Data releases. Technical details are given, lessons learned and open challenges for Gaia and future missions are discussed.
The Time Evolution of the Milky Way's Oxygen Abundance Gradient
Molla, Mercedes
We study the evolution of the Oxygen abundances radial gradient along the redshift obtained with a chemical evolution model for a Milky Way type galaxy. We revise the recent data of abundances of different objects observed in our Galactic disk. We then analyze the role of thegrowth of the stellar disk, as well as the effect of the infall rate and star formation prescriptions in the time/redshift evolution of the radial distribution of oxygen abundances in the Milky Way Galaxy; we also evaluate the role of the star formation in the halo. We show that the definition of the radial range in which the gradient of the disk is measured is essential to estimate correctly its value and evolution along time/redshift. We find that the evolution is very smooth when the radial gradient is measured within the optical radius.
The relation of the oxygen abundance radial gradient in spiral galaxies with the formation process of their disks
Molla, Mercedes
We analyse the evolution of the oxygen abundance radial gradient for galaxies of different total masses and different star formation efficiencies and the correlations of these gradients with stellar mass, effective radius or morphological type. Our main result is that the radial gradient shows a strong variation only in the very early time when stars start to form in regions out of the centre of galaxies. Then, once the disk appears, the evolution is very smooth along the time or redshift. We compare our predictions with a set of existing data showing good agreement with the negative radial gradients, while the positive gradients can not be explained with our models for isolated galaxies. We interpret the positive radial gradients observed at high redshift as corresponding to galaxies in interaction. We also compare with cosmological simulations showing good agreement with the most recent results.
Galaxy Clusters and Olbers’ Paradox
Molnar, Sandor
Foreground galaxy clusters may pose a difficulty to detect protoclusters, therefore it is important to study the distribution of these clusters in the sky and estimate the confusion they may cause. We use a semi-analytic modeling based on the latest results of cosmological simulations to study the angle on the sky occupied by the gas in clusters of galaxies. We simulate images of X-ray emission and Sunyaev-Zel’dovich signal of an evolving population of clusters of galaxies and estimate their covering factor.
Chemical signatures of FU Ori outbursts
Molyarova, Tamara
FU Ori type young stellar objects are known to experience sudden outbursts, their luminosity growing by 1-2 orders of magnitude. These objects are typically observed in their outburst state, which lasts for several decades, but are difficult to find in the quiescent state. The tool to identify the object that has passed through the luminosity outburst some time ago might be provided by disk chemistry. The disk heating and the enhanced radiation field during the outburst affect dramatically the disk chemical composition, evaporating abundant ices and accelerating chemical reactions. Some of the outburst chemical consequences may stay noticeable long enough to identify them after the outburst, when the luminosity is back to normal. We perform astrochemical modeling of protoplanetary disks before, during and after an FU Ori outburst. We find species that are especially sensitive to the luminosity growth, as well as those able to retain signatures of the outburst after it has finished. We probe the impact of disk parameters and dust size on the chemical composition of the selected species.
Zeeman Effect Observations in Class I Methanol Masers
Momjian, Emmanuel
We report the detection of the Zeeman effect in the 44 GHz Class I methanol maser line toward the star forming region DR21W. The 44 GHz methanol masers in this source occur in a ~3 arcsec linear structure that runs from northwest to southeast, with the two dominant components at each end, and several weaker components in between. Toward a 93 Jy maser in the dominant northwestern component, we find a significant Zeeman detection of -23.4 ± 3.2 Hz. If we use the recently published result of Lankhaar et al. (2018) that the F=5→4 hyperfine transition is responsible for the 44 GHz methanol maser line, then their value of z=-0.920 Hz/mG yields a line-of-sight magnetic field of 25.4 ± 3.5 mG. If Class I methanol masers are pumped in high density regions with n ~ 107-8 cm-3, then magnetic fields in these maser regions should be a few to several tens of mG. Therefore, our result in DR21W is certainly consistent with the expected values. We also give a brief overview of past Zeeman effect detections in Class I methanol masers (e.g., Sarma & Momjian 2011; Momjian & Sarma 2017) in light of the recently measured Zeeman splitting factors.
Closing the Photometric Loop: Estimating top-of-atmosphere fluxes from ground based telescopes
Mondrik, Nicholas
For a ground based observatory, the observed flux of an astrophysical source is the product of its spectral energy distribution, the Earth's atmospheric transmission, and the instrumental response. Comparing space-based spectrophotometric observations and ground-based photometry of the same stars, one should be able to reconstruct the observed brightness of the source in a given band pass if the atmospheric and instrument transmission functions are measured. We describe some results of our work to 'close the photometric loop' for HST CALSPEC stars using data obtained with the CTIO 0.9 m telescope. The instrumental response is measured in situ with the Collimated Beam Projector, and spectroscopy of telluric standards provides an estimate of the atmospheric behavior.
ISOPRENE AND TOLUENE STABILITY AT EXOPLANETARY ATMOSPHERES
Monfredini, Thiago
As the characterization of extrasolar planetary atmospheres is a new frontier in exoplanetary science, there has been a growing interest on determining what properties of atmospheric chemistry are indicative of the presence of a biosphere. Some molecules, like molecular oxygen and ozone have been proposed as possible evidence of the presence of life; however, their detectability fluctuates, and they are capable of being produced abiotically, leading to the possibility of false positives. Species known as volatile organic compounds (VOCs), such as isoprene and other terpenoids, are emitted in significant amount by trees and other vegetations. The emission of biogenic VOCs can play an important role in the photophysics and photochemistry of a atmosphere, affecting its oxidative capacity. To understand the molecular stability of VOCs in the atmosphere, we have measured the absolute photoionizing cross-section of these molecules, using an ionizing chamber and ion-trap spectrometer, with UV, EUV and soft X-ray radiation (3-300 eV) from the Toroidal Grating Monochromator (TGM) beamline of the Brazilian Synchrotron Light Laboratory (LNLS), to simulate the radiation field of astrophysical situations. The ionizing chamber has four ion-collectors, two guard-electrodes, a repeller and a pair of secondary electron deflectors in a cylindrical symmetry. It was determined the optimized voltage of the ion collector as 20 V from the plateau of ion current versus applied potential curve, through the ionization of argon, nitrogen and xenon with pressures between 10-8 and 10-6 torr. In our preliminary results, we have determined photoionizing cross-section of toluene at energies of 102 eV and 280 eV produces. Also, these results sugest that the photofragmentation of toluene at these energies produces high rates of double ionizied fragments.
SOIL CHARACTERIZATION: MARTIAN ANALOGUES
Monfredini, Thiago
The investigation of microbial life and/or inorganic biosignatures on Mars has been done mainly by the study of analogue environments on Earth. The nature of the ferriferous regions in Brazil seems to be suitable, as a substantial sources of extremophiles (Duarte et al, 2012) and potential source of inorganic biosignatures. This work is aimed to improve the knowledge needed to test the possibility of present or evidence of past life on Mars by characterizing samples of the iron-rich soil of the region of Diamantina, located at the center of Brazil. This characterization consists of examining the atomic and molecular compositions and the structural, mechanical and optical properties of the soil. This is done by applying different experimental techniques, such as thermo-gravimetry, electron microscopy and X-ray spectroscopy. The molecular and atomic structure had been measured through, both, X-ray diffraction and fluorescence at LNLS (Brazilian Synchrotron Light Laboratory - Campinas). Also, the volatile content was investigated through thermo-gravimetry in a high-temperature furnace and by H:C:N analysis. The X-ray diffractogram is dominated by cristalline silicon oxide with low contribution of an amorphous phase. Also, there is no strong evidence of phylosilicates (clay minerals). Thermo-gravimetry showed weight losses of just ~1 wt% at 600oC. For comparison, JSC Mars-1, a well-known Martian analog soil, has a large volatile content, presenting losses of 21.1 wt% in the same conditions. It also confirms the abscence of phylosilicates. Viking in situ experiments of the Martian soil released ~1.0 wt% water from samples heated at 500oC, which suggest that Martian regolith is also extremely dry (Biemann et al, 1977). So, our preliminary results showed good evidence that Diamantina's soil can be a good candidate for Martian simulant, just as JCS Mars-1 and JMSS-1.
Aperiodic variability in pulsars and the dynamo frequency
Mönkkönen, Juhani
Highly magnetized neutron stars accreting matter via an accretion disk offer a unique way to examine the interaction of plasma with the ultra-strong magnetic field. The magnetic field will truncate the disk at the so-called magnetospheric radius, inside which the disk matter is guided onto the neutron star surface where its energy is released in X-rays (so-called X-ray pulsars). The properties of the fast flux variability carry an imprint of the geometrical and physical conditions of the system.In the current work, we conducted comparative timing analysis of several X-ray pulsars whose magnetic fields are known through cyclotron line measurements. We examined the evolution of their power density spectra with respect to luminosity during outbursts. Our focus was on the power-law break frequency which in the perturbation propagation model (Lyubarskii 1997) is related to the inner radius of the accretion disk (Revnivtsev et al. 2009). Magnetic dynamo action occurs in all modern accretion disk simulations and its timescale can be linked to the growth of perturbations in the disk (Hogg & Reynolds 2016). Following the latest extension of the model (e.g. Mushtukov et al. 2018), the break frequency is expected to occur at the dynamo frequency of the inner disk radius. We now present limiting values for the ratio of the dynamo frequency to the Keplerian frequency of the inner radius.
The Wolf-Rayet Star Population in Nearby Dwarf Starburst Galaxy NGC 625
Monreal Ibero, Ana
Quantifying the number, type, and distribution of Wolf-Rayet (W-R) stars is a key component in the context of galaxy evolution, since they put constraints on the age of the star formation bursts. Nearby galaxies (distances <5 Mpc) are particularly relevant in this context since they fill the gap between studies in the Local Group, where individual stars can be resolved, and galaxies in the Local Volume and beyond.In this contribution, I will present the characterization of the W-R star population in NGC 625, a low-metallicity dwarf galaxy at ~4 Mpc, by means of optical integral field spectroscopy (IFS) data obtained with the VIMOS-IFU and the HR_Orange and HR_Blue. The number of W-R stars was estimated using a linear combination of three W-R templates: one early-type nitrogen (WN) star, one late-type WN star, and one carbon-type (WC) star (or oxygen-type (WO) star). Fits using several ensembles of templates were tested. Results were confronted with i) high spatial resolution HST photometry; ii) numbers of W-R stars in nearby galaxies; and iii) model predictions. Results of this analysis have been presented in Monreal-Ibero et al. 2017, A&A, 603, A130.
Simulation of QSO observations with HARMONI
Monreal Ibero, Ana
This work analyses simulations of observations with HARMONI, the first light integral field spectrograph for the European Extremely Large Telescope, for two different scientific approaches to understand the co-evolution of galaxies and their central massive black holes.On the one hand, we study the performances of QSOs hosts observations with HARMONI to determine black holes masses and their host galaxies properties (morphology and kinematics) at redshift around 1.5. On the other hand, we explore the capabilities of HARMONI observations to obtain astrometric measurements of kinematically selected regions of broad line regions (BLRs) of QSOs.
GRAVITOMAGNETIC ACELERATION OF THE UNIVERSE
MONROY RODRIGUEZ, MIGUEL ANGEL
Using the Hubbles law V=H*R the dark energy produce an acceleration a=R*H2. We use the approximation of the universe as a Minkowski flat spacetime and Maxwell type equations (GEM formalism) to calculate inferior bound to the gravitomagnetic acceleration that hole universe produce over one galaxy located at cosmological distance Z of the Milky Way. As result we find that gravitomagnetic acceleration a= 0.27*Z*H2 which implies, it can explain at least 27 percent of the dark energy effect.
Updates on the Ultraviolet Emission from Asymptotic Giant Branch Stars
Montez, Rodolfo
A comprehensive study of the UV emission detected from asymptotic giant branch (AGB) stars by the Galaxy Evolution Explorer (GALEX) revealed that of the 316 AGB stars observed by GALEX, 57% were detected in the near-UV (NUV) bandpass and 12% were detected in the far-UV (FUV) bandpass. The NUV emission from AGB stars is correlated with the optical to the near-infrared emission and is often found to vary in phase with phased visible light curves. The detections and non-detections indicate higher detection fractions among the brightest, and hence closest, AGB stars, as well as the influence of galactic extinction. The study also found evidence for anti-correlation between the circumstellar envelope density and the NUV – and possibly FUV – emission. Altogether, these results suggest that the origin of the GALEX-detected UV emission is an inherent characteristic of the AGB stars, likely traced to a combination of photospheric and chromospheric emission. Here, we extend our initial study (Montez et al. 2017) to include additional archival spectroscopic UV observations as well as an expanded sample of UV-variable AGB stars, in an effort to better understand the nature of AGB star UV emission.
Understanding Accretion Effects in Disks in HMXBs
Montgomery, Michele
During the HMXB phase, the companion to the more massive black hole or neutron star primary evolves, losing its mass to the primary. The lost mass is thought to form an accretion disk around the primary, which can then heat up due to friction within the disk. This heating, along with the jets that form from the primary generate the X-ray emission. Accretion disks are also suggested to occur in BeHNXBs due to the type II outbursts and QPOs that are observed. The flare-like activity during the outburst is large-scale and may be caused by instabilities near the inner edge of the accretion disk that could oscillate the accretion flow. In this work, we study effects of accretion stream on an accretion disk. We know from studies of their low-mass close binary counterparts, that gas stream overflow can impact the disk face, generating local X-ray emission. In this work, we study the net effect on the disk due to the local heating of gas stream overflow. We present our findings of effects within the disk due to gas stream overflowing the edge of an accretion disk that surrounds a high mass compact primary in a close binary.
Using VPython in the Cloud as a Mode of Teaching in General Education Astronomy
Montgomery, Michele
In this work, we discuss our strategies to encourage a culturally diverse population of general education astronomy students at a large, research-oriented university in an urban setting within the United States to write python code in the cloud to learn basic physics and astronomy principles. In addition to presenting these findings of learning by writing and running code, we also present our findings of which groups tended to opt-out from participation and why, a cognitive based research study.
Violation of the paradigm: a new path of circumstellar disk evolution around young A-type stars
Moor, Attila
In the early phase of their evolution stars are surrounded by massive primordial disks, mainly composed of gas but also containing a lesser amount of dust. According to the current paradigm, this primordial material dissipates by the age of 10 Myr in most systems, leaving behind a tenuous debris dust disk, whose observable parts are composed of short-lived second generation dust grains that are replenishedfrom collisional erosion or evaporation of larger planetesimals. While the evolution of dust between the two stages is rather well studied, the evolution of gas remains poorly explored. In order to better understand this aspect of the transition, we carried out observations with ALMA to measure the CO content of 18 nearby young (10-50 Myr) dust rich debris disks. We discovered gas in three debris disks.By supplementing our target list with literature/archival CO line data, we compiled a nearly complete volume-limited sample of dust-rich cold debris disks with fractional luminosity of >5x10-4 within 150pc.The analysis of this sample implied that the presence of CO gas in bright debris disks around young A-type stars is a common phenomenon. Interestingly, dust-rich debris disks around young FG-type stars exhibit a significantly lower gas incidence. The main difference between the two samples is related to a special population of gaseous debris disks whose total CO gas quantity is comparable to that of less massive Herbig Ae and T Tauri disks. This large amount of gas indicates that - contrary to "normal" debris disks where the gas component is derived from the erosion of planetesimals - in these objects the gas may rather have primordial origin. Since their dust content is secondary, these disks probably have a hybrid nature representing a very special phase in which the evolution of the gas component is decoupled from that of the dust.
Detection of Exoplanets in Multisystem Stars Using Quantization of Orbits
Morcos, Abd El Fady
Detection of the exoplanets in multisystem stars represents one of the important tasks in the coming interval of time. Thousands of multisystem in particular triple systems have been observed. The detection of the nature of the third body as a planet represents a hard question to be answered in triple systems. In a previous theoretical trial, Morcos in 2013, derived a simple relation, in the framework of scale relativity (Nottale (1997)), to find the orbital period of solar system plants by using a quantized form. That formula has been adapted to calculate the quantum orbital number of some exoplanets (Morcos, et al (2016)). In this work, the previously mentioned relation has been reformed using Hill radius of Margot (2015) to detect exoplanets in multisystem stars. The results may through a light on detection of the third body as an exoplanet by using the quantization of the body's orbit.
Activities in Egypt in the Frame Work of NOC
Morcos, Abd El Fady
Since three years NOC activities had been started in Egypt. The rate of our activities increased than the previous date by supporting us by NOC publications and contacts. Our activities nowadays cover many ranges. We concentrate during the interval from 2015 till now on public elementary lecturers in different fields of astronomy and cosmology, in different places e.g. in public libraries, public and professional societies besides Helwan and Kottamya observatories and different Universities. On the other hand, a team of lecturers at different ages and different scientific backgrounds from different organizations, visit schools and universities giving simple and professional lectures. Training and courses about different topics of astronomy and practical workshops were done at Astronomy Department in National Research Institute of Astronomy and Geophysics, Kottamya observatory, Kottamya Center of Scientific Excellence for Astronomy and Space Science and Scientific Society of Astronomy & Space in Egypt – SSASEgypt , for Different Faculties students and high schools students. Conferences for two days and one-day meetings were held. Open area observations at different deserts were done also at both of Helwan and kottamya observatories. The observatory was opened for free for popular in astronomical special events. We made the area of contact through social media as Facebook and internet sites wider. Many TV and Radio programs were presented. A lot of simplified astronomical books were published and distributed for free. In the end, we got the chance to held ISYA to hold in Egypt during the interval from 26 March 2018 to 12 April 2018. It is worth of mentioning that Egypt is planning to build a new telescope in too near future.
Astronomy Education in Egypt through the last 3 years
Morcos, Abd El Fady
One of the major tasks in Egypt now is developing the education of astronomy. We can divide it into three essential axes. The first level is in the different stages of education starting from primary stage to university stage, the second is for popular and the third is for amateurs. The Egyptian National Committee for Astronomy, under the supervision of the ministry of high education and the Academy of Scientific Research and technology, put on its shoulders the responsibility of revising the astronomy parts in primary preparatory and secondary stage’s courses. Also, some training programs had been prepared for teachers of different stages of educations, in collaboration with the ministry of education. In the secondary and university stages training courses for students of faculties of science and also of engineering have been done and will be done in the National Research Institute for Astronomy and Geophysics and Kottamia Center of Scientific Excellency for astronomy and space science. A new faculty of space technology was opened to learn astronomy and astrophysics and space technology. In the framework of the regional countries, we did a training course and conferences for surrounding Arab and African. It is worth of mentioning that the coming ISYA in 2018, will be held in Egypt. For popular level, general lectures programs were prepared by different societies (private and governmental). These societies have been encouraged to similar activities and visiting Kottamia observatory. There are different sites in social media have been used to publish important and basic astronomical knowledge and events. Many TV and Radio programs aiming to spread astronomical culture were presented. For amateurs, professional courses and practical training were prepared.
Dark Matter and Dark Energy as Remnants of Visible matter in Cosmological Models
Morcos, Abd El Fady
The accelerated expansion of our universe needs consistent theoretical models to explain the origin of this acceleration. The cosmological equations describing the formation of large-scale structures in a homogeneous and isotropic universe are systems of ordinary differential equations. The formations of large-scale structures depend on the cosmological model and the framework of the theory in which the model has been formed. It is assumed, in this work, that the remnants after the formation of large-scale structures (visible universe) represent the dark matter and dark energy. Different cosmological models have been used as Saez and de Juan model, The self-consistent model, and the standard model. It is found that the description of dark matter and dark energies as remnants of visible matter depends on a parameter which depends on the model itself.
Dynamical resonance and the core-cusp problem in dark matter halos
Mori, Masao
We have studied the dynamical response of dark matter (DM) halos in darf galaxies to recurring changes in the gravitational potential of the interstellar gas near the centers of the DM halos. A resonance model between the DM particles and density waves excited by the oscillating external potential is proposed to understand the physical mechanism of the cusp–core transition of DM halos. We determine that the collisionless system effectively gains kinetic energy from the energy transfer driven by the resonance between the DM particles and the density waves induced by the oscillation of the gravitational potential of the interstellar gas. The condition for the cusp–core transition is such that the oscillation period of the baryon potential is the same as the local dynamical time. The core radius of the DM halo after the cusp–core transition driven by the resonance is shown using the conventional mass density profile of DM halos, which is predicted by the cosmological structure formation models. Moreover, we verify our analytical model by using numerical simulations, whose results validate our resonance model. Therefore, we conclude that the energy interchange between the DM particles and the oscillation of the baryon potential driven by the resonance mechanism plays a key role in solving the core–cusp problem of DM halos.
The Cassini RPWS/LP observations of Dusty Plasma in the Kronian System
Morooka, Michiko
During almost thirteen years of the Saturn orbiting period, the Cassini visited various regions that consist of the small dust grains in the Kronian system. The RPWS (Radio and Plasma Wave Science)/LP (Langmuir Probe) onboard Cassini was the device to estimate the thermal plasma parameters that are important for characterizing the surrounding plasma and dust properties. In Saturn’s faint rings (the E and F rings), in the Enceladus plume, and in the atmosphere of Titan, the LP observations indicated the presence of the dusty plasma, where the nano grains becomes important in charge balance. During the Grand Finale orbits, the LP identified the dusty plasma also in the ionosphere of Saturn. The observed dust and plasma characteristics were all unique in different places, but showed the importance of the small (nano) grains in the plasma. We will review the dusty plasma in the Kronian ring system in terms of the Cassini/LP observations.
The Starspots of HAT-P-11: Evidence for a Solar-like Magnetic Dynamo
Morris, Brett
We measure the starspot radii and latitude distribution on the K4 dwarf HAT-P-11 from Kepler short-cadence photometry. We take advantage of starspot occultations by its highly-misaligned planet to compare the spot size and latitude distributions to those of sunspots. We find that the spots of HAT-P-11 are distributed in latitude much like sunspots near solar activity maximum, with mean spot latitude of 16±1°. The majority of starspots of HAT-P-11 have physical sizes that closely resemble the sizes of sunspots at solar maximum, with occasional spots larger than the largest sunspots. We measure the mean spotted area coverage on HAT-P-11 is 3%, roughly two orders of magnitude greater than the Sun’s. The similarities in spot distribution and radii are interesting given the star’s similar rotation period (29 d) but smaller mass (0.8 MSun) than the Sun. We also monitor the chromsopheric activity of the star from the ground with the ARC 3.5 m telescope at the Apache Point Observatory, and find evidence for a ~10 year cycle.
Study of the equilibrium points and the dynamic characteristics of the surface of the asteroid 16 Psyche
Moura, Tamires
16 Psyche is an asteroid located in the main belt. It has a diameter of approximately 250 km, in addition to being considered the most massive among the M-type asteroids. This fact makes Psyche a unique object, since observations indicated an iron-nickel composition. It is believed that this body may be what was left of a metal core of an early planet that would have been fragmented over millions of years due to violent collisions. The Psyche space mission, selected by NASA, aims to study the origin of planetary nuclei based on the exploration of the asteroid 16 Psyche. The launch of the mission is scheduled for 2022 and, after a 4-year journey, will explore the target for about 21 months. In the present work is studied a variety of dynamical aspects related to the surface, as well as, the environment around this asteroid. In our studies was adopted the shape of the asteroid determined by radar observations. The shape is given by a polyhedron of 2292 triangular faces and 1148 vertices. Assuming constant values for its density and rotational period. We used computational tools to explore the gravitational field generated by this asteroid. It was determined a set of physical and dynamical characteristics over the whole surface of the asteroid. Among them were computed the altitude, tilt, slope, potential height, potential speed and escape speed. In order to explore the neighborhood close to asteroid 16 Psyche, the location and linear stability of the equilibrium points were found. The system has four external equilibrium points and an internal one. Two of the external points are unstable and the other two stable. A set of numerical simulations of massless particles around the asteroid confirmed the stability of these points, and also showed an asymmetry in the size of the stable regions. That information is also relevant in order to estimate regions on the surface of 16 Psyche that might have a higher amount of accumulated particles.
The non-Fourier image reconstruction method for the STIX instrument
Mrozek, Tomasz
The STIX is an X-ray imaging spectrometer operating in the 4-150 keV range. It is equipped with 30 pairs of grids with pixelized Caliste-SO detectors. Such system allows for registering the Fourier components of solar flare HXR emission distribution. In our method we abandon the Fourier's approach to image reconstruction. We use only the number of counts recorded by each of detectors, and reconstruct image on the basis of the classical Maximum Likelihood method. With a knowledge of the instrument detailed geometry we are able to calculate detectors response for point source. For our purpose the point source is a 1x1 arcsec pixel on the Sun. Having calculated point source response on the grid covering entire solar disc, we can iteratively combine point responses with varying weights until the best match between reconstructed and observed detector responses is achieved. Preliminary tests revealed that the developed algorithm reproduce reliable images of simulated solar HXR sources. In particular, it is very robust for some specific configurations which are problematic for other existing algorithms.
Finding Gamma Dor pulsators in Kepler's database
Mu, Xiaoyong
We design a selecting programme to screen ? Dor pulsators from the Kepler's database of more than 200,000 stars, from which we select candidates for visual classification. To include more candidates, very loose limitation factors are considered. We get thousands of ? Dor candidates whose spectral types are between G0 and A6, with effective temperature restricted in the range of 6000K - 8000K. In addition, they should be variable stars with at least a frequency between 0.2 per day and 5 per day. Then we classify them visually to find stars whose light variation is almost mono-periodic with characteristic beating. From the candidates, we get several hundred of ? Dor pulsators. In the end, we present a comprehensive analysis of this sample from the kepler database.
Improving the accessibility of research articles at the American Astronomical Society
Muench, August
There are many contributors to the creation and production of an astronomy journal article. All of these contributors, from the author themselves to the preprint platform to the journal production editors and staff must grapple with how to make the final research available to the broadest segment of the astronomy community and the public. In this talk (or poster) I will describe the approach of the American Astronomical Society to improve the accessibility of the articles published in its Journals. I will review our work with our publishing partner, the Institute of Physics in response to the AAS's Working Group for Accessibility and Disability's 2016 Recommendations, “Improving Accessibility of Astronomical Publications” and will provide a current status update of authoring and access tools for the astronomical literature.This topic may also be relevant to FM15 if the SOC feels that the contribution has broader synergies with the OAD efforts.
How many suns are in the sky? - Multiplicity surveys of exoplanet host stars
Mugrauer, Markus
In order to determine the true impact of stellar multiplicity on the formation and on the evolution of planets, we have initiated direct imaging surveys to search for (sub)stellar companions of exoplanet host stars on close orbits, as their gravitational impact on the planet bearing disk at first and on formed planets afterwards is expected to be maximal. According to theory these are the most challenging environments for planet formation and evolution but might occur quite frequently in the milky way, due to the large number of multiple star systems, which reside within in our galaxy. Here we will show some results, obtained so far in the course of our AO and Lucky-imaging campaigns of exoplanet host stars, conducted with NACO at the Paranal observatory in Chile for southern and with AstraLux at the Calar Alto Observatory in Spain for northern targets, respectively. In addition, we will introduce our new high contrast imaging project of southern exoplanet host stars, recently started with SPHERE, the new high contrast AO imager operated at the ESO-VLT, and we will present some first results of this survey.
Multiplicity study of T Tauri stars in the Lupus star forming region
Mugrauer, Markus
We have carried out a high contrast imaging survey for stellar and substellar companions among young pre-main sequence stars in the Lupus star forming region. For this long-term project we have utilized the adaptive optics imager NACO of the ESO-VLT, operated at the Paranal observatory in Chile. Here, we will present the results of this survey. In several observing campaigns we could obtain diffraction limited deep IR imaging data and have detected faint co-moving companions around our targets, whose astrometry (angular separations and position angles) as well as IR photometry was determined in all observing epochs. The co-moving companions found in our survey exhibit angular separations in the range between about 0.1 up to a few arcsecs, which corresponds to projected separations between about 10 up to a few hundreds of au, at the distances of our targets (about 140pc, in average). Beside several new binary and triple star systems, whose multiplicity was revealed in this survey, also faint co-moving companions in the substellar mass regime could be identified close to some of our targets.
Asteroid photometric and polarimetric phase effects: Modeling for the main taxonomical classes
Muinonen, Karri
We consider scattering and absorption of light in the regoliths of asteroids, that is, in discrete random media of densely packed particles. We extend the numerical Monte Carlo method of radiative transfer and coherent backscattering [1] to the case of dense packing of particles [2,3], establishing the numerical method of radiative transfer with reciprocal transactions (R2T2, [3]). We adopt the ensemble-averaged incoherent extinction, scattering, and absorption characteristics of a volume element of particles, computed using the Superposition T-Matrix Method (STMM, e.g., [4]), as input for the R2T2. The volume element must be larger than the wavelength but smaller than the mean free path length of incoherent extinction. We show that the R2T2 solutions are in agreement with the exact STMM solutions for large finite systems of densely packed particles [2,3]. We apply the R2T2 to the photometric and polarimetric phase curve observations of the main taxonomical classes of asteroids and utilize the observations to retrieve wavelength-scale information about the regoliths of the asteroids.References: [1] Muinonen, K., 2004, Waves Random Media14(3), 365. [2] Muinonen, K., Markkanen, J., Väisänen, T., Peltoniemi, J., and Penttilä, A., 2017, Radio Science52, 1. [3] Muinonen, K., Markkanen, J., Väisänen, T., Peltoniemi, J., and Penttilä, A., 2018, Opt. Lett.43, 683. [4] Markkanen, J., and Yuffa, A. J., 2017, JQSRT189, 181.
About astronomy outreach in Mexico
Mujica, Raul
The astronomical vocation in Mexico has a long tradition that comes from the prehispanic cultures that adored the Sun and developed outstanding abilities to observe our star. They left several testimonies of this wisdom in codices, sculptures and in the architecture of their buildings. The tradition has been maintained, Mexico has a very robust professional astronomical community and a community of very enthusiastic amateur astronomers, also with a great tradition, for example, the Astronomical Mexican Society was founded more than 115 year ago, being the second amateur astronomy association founded in the world.More important is that, between these two groups, there is also a long history of collaboration bringing astronomy to the great public.Outreach programs in our country are of high quality, mainly thanks to this collaboration between amateur astronomy groups, astronomers and science popularizers who are very well organized in networks, such as the Mexican Association of Planetariums, the Association of Science Centers and Museums, the Science Popularizers Network, etc. Maybe one of the most important is the organization “Noche de las Estrellas (NdE)” with members all around the country. NdE is coordinated through a National Committee composed of representatives of some of the major astronomical research and outreach institutions in Mexico. Up to date, the NdE network is composed of more than 100 groups, named local committees, distributed throughout the states of the Mexican Republic. The groups include science museums, planetariums, cultural centers, civil associations, universities, etc. We have plenty of experience organizing series of public talks, workshops, star parties, exhibitions, contests, science fairs, and many other activities to promote scientific vocation among the young Mexican population. I will talk about several current astronomy outreach programs in which the National Institute of Astrophysics, Optics and Electronics is involved.
Long-term asymmetry in the solar hemispheric cycles
Murakozy, Judit
Hemispheric solar cycles show long-term difference in their time profiles and intensities. This difference can clearly be observable during the last twelve cycles and not so clearly before 1874, the start of the Greenwich Phootheliographic Results. For that time there are three more sunspot data are available made by using the observations of Schwabe, Staudacher and Spörer. These catalogues consist of sunspot location data of Cycles 1-4, 7-10 as well as 10-11. The detectable hemispheric variation means the two hemispheres always change the leading role in time after four Schwabe cycles. This variation can also be recognized in the magnetic field reversal data which may indicate that this variation is a long-term property of the entire solar dynamo mechanism.
A modular pipeline proposal for the short-term solar irradiance forecasting
Muralikrishna, Amita
The Sun, being a star closer to the Earth, allows its more detailed and constant monitoring, which benefits the study of the causes and consequences of its influence on the planet as well as the study of the profile and behavior of other stars of the Universe. Among several aspects that can be investigated in solar activity, the relation of a given solar cycle and its features - such as the formation and evolution of sunspots and active regions - with events occurring on Earth can contribute to the achievement of short-term and long-term researches around the terrestrial climate and the disturbances of the Earth atmosphere layers. One of the relevant parameters of this relationship is the total and spectral solar irradiance, which provides an indication of how much the radiation emitted by the star can influence life on the planet. The accurate prediction of solar irradiance at the top of the Earth's atmosphere, using for that solar activity data, has been a challenge, since the orbiting instruments that perform these measurements have a limited useful life and suffer damages over time. This work proposes the modularization of the irradiance forecast task, suggesting a process composed of steps that can become relatively independent, so that they can be replaced by other options like another database or computational techniques for specific tasks, for example, thus offering flexibility for the continuous optimization of the process. The aim is to construct the process in the form of a pipeline, using some of Data Science concepts, such as reproducibility and application of Machine Learning techniques, together with functionalities that involve traceability of partial and final results and their availability as products.
KAGONMA:NH3 mapping observations of molecular clouds with Nobeyama 45-m telescope
Murase, Takeru
In the molecular cloud collapsing phase, the molecular gas temperatureis a key to understand the process from a dense molecular cloud tostars. Thank to many transitions in the rather narrow frequency band,or 23 GHz, we can derive many physical parameters of molecular gasusing NH3 lines. From the line intensity ratio of the satellite andmain lines we can estimate the optical depth of the line and theintensity ratio of NH3 (1,1) and NH3 (2,2) we can estimate the rotationtemperature. This is well known and many investigations have been made.However, most of them are observations toward cores in molecularclouds. But our group made mapping observations of molecular cloudassociated with Monkey Head Nebula and W4 and no systematic temperaturegradient was found in either cloud (Chibueze et al. 2013 and Nakano etal. 2017). This shows mapping observation is important. Therefore, weconduct “KAGONMA”, which is an abbreviation of “Kagoshima Galacticobject survey with Nobeyama 45-m telescope in ammonia lines”. Based onC18O (1-0) data from FUGIN, or “FOREST unbiased galactic plane imagingsurvey with Nobeyama 45-m telescope”, we choose 71 molecular cores andare making mapping observations in NH3 (1,1), (2,2), (3,3) and H2Omaser lines. Until this season we have made 3 maps. From these maps wefound temperature structure in a cloud. In this talk we show the latestresults of them and discuss on the relation between temperaturestructure and star formation activity in each cloud.
Ultra Long Period Cepheids: a cosmological primary standard candle in the E-ELT era
Musella, Ilaria
The extragalactic distance scale is largely based on the period-luminosity relation of the Classical Cepheids but to reach cosmologically significant distances we need one or more secondary distance indicators and their calibration suffer several uncertainties. In this context, the possibility to use primary indicators observable in the Hubble flow would be very important. A very promising good candidate as primary standard candle is represented by the Ultra Long Period Cepheids (ULPs). These variable stars appear to follow the extension at higher periods of the Classical Cepheids period-luminosity and period-Wesenheit relations. Thank to their high luminosity, this class of variables could represent primary distance indicators capable to reach, in one step, distances up to 100 Mpc and, in the future, using the European Extremely Large Telescope, up to 350 Mpc.In this context, our group is engaged to verify both from the observational and the theoretical point of view thei goodness of ULPs as standard candles also using their Gaia parallaxes in the Magellanic Clouds.
Active Galactic Nuclei with a Low-metallicity Narrow-line Region
Nagao, Tohru
Low-metallicity active galactic nuclei (AGNs) are interesting to study the early evolutionary phase of AGNs and supermassive black holes (SMBHs). However, most AGNs are chemically matured, and accordingly, low-metallicity AGNs are extremely rare. For identifying low-metallicity AGNs, we focus on objects located at "the BPT valley"; i.e., showing high [OIII]5007/Hb4861 and relatively low [NII]6584/Ha6563 flux ratios (Groves et al. 2006). We examine how many objects among the BPT-valley objects are low-metallicity AGNs, since other populations of galaxies (such as extreme star-forming galaxies, AGNs with narrow-line regions characterized by a very high density and/or low ionization parameter). We select 70 BPT-valley objects from 212,866 emission-line galaxies obtained by the Sloan Digital Sky Survey (SDSS). Among the 70 BPT-valley objects, 43 objects show firm evidence of the AGN activity, i.e., the HeII emission and/or weak but significant broad Ha emission. Our analysis shows that those 43 BPT-valley AGNs are not characterized by a very high gas density nor ionization parameter, inferring that at least 43 among 70 BPT-valley objects (i.e., > 60%) are actually low-metallicity AGNs. This suggests that the BPT diagram is an efficient tool to search for low-metallicity AGNs (Kawasaki, Nagao, Toba, et al. 2017).
Evolution of dwarf galaxies in a semi-analytic galaxy formation model
Nagashima, Masahiro
Dwarf galaxies are sensitive to some physical processes such as supernova feedback in galaxy formation owing to their shallow gravitational potential wells, therefore, they provide constraints on galaxy formation. We analyze formation and evolution of dwarf galaxies by using our own semi-analytic galaxy formation model, New Numerical Galaxy Catalog (?2GC), in which we model galaxy formation with many physical processes such as gas cooling and heating, star formation, supernova and AGN feedback, formation of supermassive black holes, galaxy mergers, starbursts, and stellar population synthesis within dark matter halos based on the cold dark matter model of the Universe. The model is combined with very high-resolution N-body simulations that can resolve the Jeans scale after cosmic reionization, therefore we can be almost free from resolution-dependent rsults. We have found that our model succeeds in reproducing many observations such as luminosity functions. In this poster, we extend our analysis towards dwarf galaxies.
Astrometric VLBI observation of the Galactic LPVs with VERA; Miras and OH/IR stars
Nakagawa, Akiharu
We present studies of LPVs in the Milky Way Galaxy (MWG) based on astrometric VLBI observations of H2O/SiO maser with VERA. The LPVs are 1 - 8 Msun AGB stars pulsating with typical period range of 100 - 1000 d. They are on the late stage of their life time, and show high mass loss ratio (10^-7 Msun/yr) before they evolve to planetary nebulae.LPVs in the LMC show some period-luminosity relations (PLR), and the PLR is used as distance indicator for Miras in the MWG. But metallicity is different between the LMC and MWG, it is also important to explore PLR of Miras in MWG. Since 2003, we have been observing dozens of Miras in MWG. The latest Galactic Mira’s PLR determined from our study is Mk = -3.52 logP+1.09 (+-0.14) (Nakagawa et al. 2016). In this conference, new results will be added. We find consistency of PLRs between LMC and MWG, but some stars show fainter magnitudes than expected from the PLR previously obtained. Though the discrepancy should be investigated, this can possibly indicate different properties of Miras in the LMC and MWG. Astrometric VLBI also has an advantage to reveal dynamical picture of circumstellar matters. A 3D model of circumstellar matter in “OH231.8+4.2” will be shown as an example.There are OH/IR stars showing quite long period longer than 1000 d (Extreme-OH/IR). They are thought to have initial masses of ~4 Msun and ages of ~10^8 yr. Recent studies predict galactic spiral arms bifurcating/merging in time scale of 10^8 yr. So, the Extreme-OH/IR stars can become a new probe to survey spiral arms. We started 43GHz VLBI observations of 2 Extreme-OH/IR stars, OH127.8+0.0 and NSV25875 from Oct. 2017. Images from phase-referencing analysis will be presented. Since evolutional relation between Miras and OH/IR stars is still an open question, sequential studies of LPVs along wide period axis are crucial. LPVs with longer period tend to be fainter in visible band, and VLBI observations play a promising and complementary role even in Gaia era.
Firm Detection of 7-Year X-ray Periodicity from X Persei
Nakajima, Motoki
X-ray binary pulsars exhibits various time scale activities.These variabilities are considered to be produced by the rotation of the neutron star, the binary orbital motion, and the precession of the accretion disc around the neutron star (so called superorbital).Each time scale distributes in the time range from few milliseconds to months.In addition to the above periodicities, Laplace et al.\ (2017) reported that Be/X-ray binary pulsar EXO 2030+375 repeats the giant X-ray outburst and the outburst phase shift with the time interval of ~10 years.In order to explain such long-term recurrence period, Kozai-Lidov oscillation model was proposed, and the estimated period was similar to the observed time interval of ~10 years.Except for EXO 2030+375, there are no reports about the sources which shows a periodicity more than several years, so far.To search for another source having long periodicity, we analyzed one of the Be/X-ray binary pulsar, X Persei, observed by RXTE/ASM, Swift/BAT, and MAXI/GSC.This source is characterized by a spin period of ~835 s, an orbital period of 250.3 days, an ecccentricity of 0.11 (Delgado-Marti et al.\ 2001).No normal outburst have been recorded from this source, however, it was observed that its X-ray flux has increased about twice every 7-years since 2003.Furthermore, it was confirmed that the decrease timescales (~250 days) are the same for all three X-ray flares.
Japanese Asteroid Studies for a Century after the Discovery of the Hirayama Families
Nakamura, Tsuko
This paper reviews the studies relating to asteroids conducted by Japanese astronomers for a century since the discovery of asteroid families by Kiyotsugu Hirayama in 1918. First, the situation is mentioned that it took quite some time for the concept of an ‘asteroid family’ to be understood correctly by the astronomical community worldwide. It is no wonder that some eminent researches on the dynamics of asteroids appeared in Japan after WWII, as represented by the Kozai mechanism (1962), which probably was stimulated by Hirayama’s monumental discovery. As for studies of the physical nature of asteroids, we must note the pioneering work by M. Kitamura in 1959 when the observed colors of about 40 asteroids were compared with reflectance spectra of several meteorites measured in the laboratory. Modern impact experiments initiated by A. Fujiwara in 1975 soon became an important means for investigating the origin of asteroid families, and collisional phenomena in general in the Solar System. Then we overview recent outcomes briefly in 1) the discovery of a huge number of meteorites in Antarctica by the Japanese expedition team, 2) the establishment of the ISAS and its achievements in the asteroid mission to the near-asteroid Itokawa by the Hayabusa spacecraft in 2005, 3) the discovery race of asteroids by Japanese amateur asteroid hunters during the 1980s-2000s, 4) an experimental solution of the space weathering problem in asteroid reflectance spectra, and 5) survey observations of sub-km-sized asteroids using the 8.2m Subaru telescope equipped with a wide-field CCD camera.
Kinetic Simulations of the Radiative Signatures of Relativistic Magnetic Reconnection
Nalewajko, Krzysztof
We present the results of kinetic numerical simulations of relativistically magnetized plasmas that illustrate the mechanism of magnetoluminescence, i.e., efficient conversion of free magnetic energy into broad-band non-thermal radiation by means of localized magnetic reconnection and associated particle acceleration. In particular, we performed 2D and 3D particle-in-cell simulations of periodic magnetic equilibria known as "ABC fields", including radiation losses due to synchrotron and inverse Compton processes. Similar processes can be expected to operate within the relativistic jets of active galactic nuclei, leading to non-thermal radiation signals observed in blazars and radio galaxies. We calculate detailed radiation signatures including lightcurves, spectral energy distributions, and synchrotron polarization. We investigate the effect of strong radiative losses on the intrinsic structure of dynamical current layers. We also demonstrate departure of the Compton dominance parameter from its nominal value, which can be invoked to alleviate the extreme energetic constraints imposed on the relativistic jets by rapid gamma-ray flares.
Magnetic Variability of the Sun over the Main Sequence Lifetime
Nandi, Dibyendu
The Sun's magnetic output varies and this variation impacts its radiative and wind output, and spawns magnetic storms such as flares and coronal mass ejections. Several decades of observations and modelling in the context of the solar system show that solar variations force planetary environments and atmospheres. It is thought that the magnetic output of the Sun has evolved over timescales relevant for planetary evolution, driven by changes in its internal differential rotation due to angular momentum losses mediated by the solar wind. Based on an analysis of available stellar activity observations and stellar parameters relevant for the solar dynamo, we infer the magnetic field variation of the Sun (or a solar-like G2 star) over its Main Sequence lifetime. In the light of this inferred magnetic variability of the Sun, we discuss plausible changes in our space environment over timescales relevant for habitability and planetary atmospheric evolution.
Multi-frequency study of a large sample of double-double radio galaxies
Nandi, Sumana
Striking examples of episodic jet activity in active galactic nuclei (AGN) are the double-double radio galaxies (DDRGs) with two pairs of lobes emerging from the same central engine. The mechanism for multiple jet activity in DDRGs is still unclear. Several ideas were proposed to explain this phenomenon and most possible scenario is merging of the two black holes. The number of DDRGs reported so far is very limited, and it is important to identify more of these to provide a significant statistical overview of the conditions to trigger the jets and the role of jets in terms of feedback mechanisms that affect the host galaxies. A significant number of smaller sized candidate DDRGs have been identified in our recent study. We started low-frequency observation of this sample to confirm that the sources are related to distinct epochs of nuclear activity. For few sources in this sample we noticed instability in jet direction. Radio galaxies with rapid change of jet axis are the prime candidates to detect binary black hole systems. Interestingly we identified one candidate which shows not only restarted jet activity with a axis reorientation but also generates double-peaked emissions line from the central AGN. The split in emission lines are the possible out come of a bound pair of supermassive black hole, moving with their own characteristic velocity. Here, I will highlight the main results from our observations and discuss on the possible scenarios responsible for the episodic activity in DDRGs.
Modeling of Century-Scale Solar Activity and a Prediction for Cycle 25
Nandi, Dibyendu
It is now believed that variations in the Sun's irradiance are primarily governed by surface magnetic flux emergence and evolution -- at least over centennial timescales. Observations show that this flux emergence is cyclic with significant variations in the amount of magnetic flux from one cycle to another. This magnetic variability is driven by a magnetohydrodynamic dynamo mechanism operating in the Sun’s interior. Based on recent advances in our understanding we utilize a solar surface flux transport model and a solar internal dynamo model to perform the first ever century-scale calibrated, data driven simulation of solar activity to predict the strength and timing of the upcoming sunspot cycle 25. Our simulation results are further interpreted to provide insights on the processes that govern long-term solar variability over centennial timescales.
Carbon stars in the Magellanic Clouds: properties and dust production rate
Nanni, Ambra
We employ newly computed grids of spectra reprocessed by dust to fit the spectral energy distributions (SEDs) of the entire sample of carbon-stars (C-stars) in the Small Magellanic Cloud (SMC). This procedure allows us to derive some important properties of these stars as well as their dust production rate (DPR). For the first time, the grids are calculated as a function of the stellar parameters, i.e. mass-loss rate, luminosity, effective temperature, current mass and carbon-excess, following a consistent, physically grounded scheme of dust growth coupled with stationary wind outflow. Our model accounts for the dust growth of various dust species formed in the circumstellar envelopes of C-stars, such as carbon dust, silicon carbide and metallic iron. The available grids are computed for different combinations of optical constants and grain sizes for carbon dust that have been shown to simultaneously reproduce the most relevant infrared colour-colour diagrams in the SMC.Differently from the other works in the literature, our approach allows for the direct estimate of the mass-loss and of the DPR of these stars, without the need of assuming the gas-to-dust ratio, the outflow expansion velocity and the dust chemistry. These latter quantities are indeed consistently calculated by in our dust growth scheme.The DPR provided by our method can be significantly different, between a factor of 2-5, from the ones available in the literature.The same kind of investigation is currently ongoing for C-stars in the Large Magellanic Cloud and we here show our preliminary results.
The analysis of geodetic residuals based on recent models of atmosphere and ocean for different time scales
Nastula, Jolanta
An assessment of the impact of hydrological effects on polar motion, through seasonal soil moisture changes, ice and snow loading and melting, is based on the determination of geodetic residuals (GAO). Being difference between Geodetic Angular Momentum (GAM) and the sum of Atmospheric and Oceanic Angular Momentum (AAM and OAM, respectively), geodetic residuals reflect hydrological signals in observed polar motion excitation. However, while GAM is determined from precise geodetic measurements such as SLR, VLBI and GNSS, AAM and OAM are based on different models of atmosphere and ocean. Consequently, the errors of geodetic hydrological excitations are mainly related to inaccurate geophysical models. The mass terms of AAM and OAM, related to air pressure and ocean bottom pressure, as well as motion terms connected with wind speed and currents, vary from one model to another.Here, we would like to compare the results of different geodetic hydrological excitation functions, that are computed by removing modelled atmospheric and oceanic effects from precise observations of polar motion excitations. To do this, we use several models of AAM and OAM. Additionally, we compare the resulting geodetic residuals with hydrological excitation functions based on Gravity Recovery and Climate Experiment (GRACE) satellite mission and hydrological models. The polar motion budged is analysed here at different time scales – decadal, interannual, seasonal and short term oscillations. This analysis could let us indicate which components of different models of atmosphere and ocean cause the biggest errors in geodetic budget at specific time scales.
Flow behind an exponential shock in a rotational axisymmetric mixture of non-ideal gas and small solid particles with heat conduction and radiation heat flux
Nath, Gorakh
The propagation of exponential cylindrical shock wave in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux, which has a variable azimuthal and axial fluid velocity, is studied. The shock wave is driven out by a piston moving with time according to exponential law. Similarity solutions exist only when the surround medium is of constant density and constant angular velocity. The azimuthal and axial components of the fluid velocity in the ambient medium are assumed to be varying and obeying exponential laws. The dusty gas is assumed to be a mixture of small solid particles and non-ideal (or perfect) gas, in which solid particles are continuously distributed. In our model it is assumed that the small solid particles are pseudo-fluid and the equilibrium flow-conditions are maintained in the flow-field. The heat conduction is express in terms of Fourier’s law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient αR are assumed to vary with density and temperature.The effects of the variation of the heat transfer parameters, mass concentration of solid particles in the mixture κP the ratio of the density of solid particles to the initial density of the gas Ga and the parameter of the non-idealness of the gas b are worked out in details. It is found that an increase in the ratio of the density of solid particles to the initial density of the gas or the conductive heat transfer parameter or the radiative transfer parameter increases the compressibility of the mixture in the flow field behind the shock, and hence there is an increase in the shock strength. Also, it is shown that an increase in the parameter of non-idealness of the gas has decaying effect on the shock wave._x005F Key word: Shock wave; Mechanics of fluid; Rotating dusty gas; Stars; Non-ideal gas; Conductive and radiative heat fluxes
Spherical shock wave driven out by a moving piston in mixture of small solid particles and non-ideal gas under the influence of gravitation field (Roche model) with monochromatic radiation
Nath, Gorakh
Similarity solutions for the spherical shock wave in a mixture of small solid particles of micro size and non-ideal gas is discussed under the influence of gravitational field with monochromatic radiation. The shock wave is assumed to be driven out by a moving piston and solid particles are uniformly distributed in the mixture. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the moving piston. The medium is considered to be under the influence of gravitational field due to central mass (m) at the origin (Roche model). The gravitational effect of the mixture itself is neglected in compared to the attraction of the central mass at the origin. In order to obtain the similarity solutions the density of the undisturbed medium is assumed to be constant. Mathematica software is used to perform the computation. The effect of an increase in the value of the parameter of non-idealness of the gas in the mixture b , the mass concentration of solid particles in the mixture Kp, the ratio of the density of solid particles to the initial density of the gas Ga and the gravitational parameter G0 are obtained. It is shown that due to an increase in the gravitational parameter the compressibility of the medium at any point in the flow field behind the shock front decrease and the flow variables velocity, pressure, radiation flux and shock strength are increased. Also, an increase in the ratio of the density of solid particles to the initial density of the gas and the gravitational parameter has same effects on shock strength and reverse effect on compressibility. The non-idealness of the gas causes a decrease in the shock strength and widens the disturbed region between the shock and the piston._x005F Keywords: Fluid-solid interactions; Similarity Method; Shock wave; Monochromatic radiation; Gravitational field; Non-ideal gas; Roche model
Star Cluster Systems of the Andromeda Galaxy
Naujalis, Rokas
We continue studies of the M31 galaxy’s star clusters (de Meulenaer et al. 2017; A&A, 602, A112) using photometry data from the HST PHAT multicolour survey. A significant improvement in the accuracy of star cluster physical parameters – age, mass, metallicity and extinction – was achieved by combining resolved, semi-resolved, and unresolved cluster photometry. Special care has been taken to account for contaminating foreground stars. Based on a new synthetic star cluster parameter database we derived star cluster parameters in the M31 galaxy.
Near-infrared polarimetry of M2-9
Navarro, Silvana G.
We present the near-infrared polarization observations of M2-9, a highly bipolar planetary nebulae with a binary central object. The polarization observations were obtained with the near-infrared polarimeter POLICAN at the Guillermo Haro Observatory.We compare them with the optical polarization obtained at the San Pedro Martir Observatory using the polarimeter POLIMA.
MAXI observations of long-term X-ray activities in SFXTs and other HMXB systems
Negoro, Hitoshi
Monitor of All-sky X-ray Image (MAXI) on the International Space Station has been observing all the X-ray sky since August 2009. Super-giant Fast X-ray Transients (SFXTs) are one of interestingobjects of which activities often trigger the MAXI Nova-Alert system(Negoro et al. 2016, PASJ, 68, S1). MAXI detected probable X-ray enhancements from IGR J08408-4503, AX J1739.1-3020, AX J1841.0-0536, and IGR J18483-0311 (e.g., Sakamaki & Negoro 2017, in proc of "7 years of MAXI Monitoring X-ray Transients"). It is difficult to study each enhancement in detail with MAXI data because of poor statistics, but more than 8 years observationsallow us to search periodicity of the enhancements and obtain their average profiles in soft (2-10 keV) X-ray band.To obtain reliable MAXI light curves free from nearby sourcesas best as possible we perform the image fitting analysis for eachscan transit (Morii et al. 2016, PASJ, 68, S11). We present not only these results, but also long-termactivities in other HMXBs, for instance, Cir X-1 and black hole candidates,and discuss the origin of the long-term activities.
The evolution of the luminosity function faint end of cluster galaxies in the Cluster-EAGLE simulation
Negri, Andrea
The galaxy luminosity function (LF) is a fundamental tool for exploring galaxy evolution over cosmic time. In the last decade observations have been able to probe the evolution of the galaxy LF with redshift, in particular showing a variation of its low-mass end with redshift. On the numerical side, there is currently no extended study of the evolution of the LF of galaxies in clusters. We employ the data of the Cluster-EAGLE project, a set of cosmological, hydrodynamical zoom simulations of 30 galaxy clusters, to study the evolution of the galaxy LF in clusters as function of redshift. We compile a catalogue of simulated galaxies’ luminosities in the SDSS bands using the E-MILESspectra database, and taking into account dust attenuation. Stacked luminosity functions show a good agreement with observations, presenting little evolution with redshift of the faint-end slope. The environment effects are strong for intermediate-luminosity galaxies. At radius larger than 3 virial radii, star-forming galaxies dominate in number the knee of the LF, whereas, inside the clusters (r < r200), the fraction of passive galaxies is larger. The relative fraction of passive and star-forming galaxies within r200 evolves with redshift, with the star-forming fraction being larger above z~0.5. Remarkably, the fraction of low-luminosity, red dwarfs dominates the faint end up to z=2.
Characterizing of Polygonal Impact Craters on Rhea, Dione, Tethys, Ceres, and Vesta
Neidhart, Tanja
A polygonal impact crater (PIC) is a crater that does not have a circular shape but consists of at least two straight crater rim segments including a discernable angle. We examined all approved impact craters from the IAU/NASA/USGS Planetary Database on Rhea, Dione, Tethys, Ceres, and Vesta and performed statistics concerning their number of straight rims, diameters, and distribution [1]. We also measured the unknown diameters of 48 craters on Rhea.In total, 431 approved impact craters were studied. On Rhea about 48% of craters were classified as polygonal, on Dione 59%, on Tethys 34%, on Ceres 70%, and on Vesta 56%. The results regarding the mean number of straight rims and the angles between them accord well with previous studies [2,3]. Also, the assumption that PICs seem to favour small to midsized diameters has been proved [2,3]. As there are many more unapproved than approved impact craters on these objects, all impact craters between a latitude of 60° and -60° were examined yielding about 44% for Rhea, 50% for Dione, 51% for Tethys, 61% for Ceres, and 55% for Vesta. Furthermore, no correlation between the diameters and the number of straight crater rim segments was found.However, why the percentage of PICs on these objects is much higher than on the terrestrial planets and the Moon remains unclear. One possible explanation could be the different surface composition in comparison to the terrestrial planets and the Moon but for definite answers to this question further understanding of the formation process of PICs, which is still unclear, is necessary.References: [1] IAU/NASA/USGS Planetary Database. (2016), planetarynames.wr.usgs.gov. [2] Öhman et al. (2010) Geol. Soc. Spec. Pap., 465, 51-65. [3] Weihs G. T. et al. (2015) Planet. Space Sci., 111, 77-82.
The XUV Sun in Time*
Nemec, Nina-Elisabeth
The evolution of the X-ray and extreme ultraviolet radiation (XUV) of a star is important to understand the evolution of planetary atmospheres as this radiation heats and ionizes the upper layers of such atmospheres. The XUV output of solar-type stars varies on evolutionary timescales, showing a gradual decline seen at all wavelength regimes. However, the XUV radiation is essentially unobservable for most stars between approximately 10 and 92 nm because of interstellar absorption due to hydrogen.We present a novel method based on the stellar S-index or R’HK (probing the strength of the Ca II H and K lines), using calculated spectra of elementary solar features and their filling factors to model the stellar flux across the XUV wavelength range. We present filling factor relations for up to eight different solar features that are extrapolated to stars at much higher activity levels with the help of some filling factor information (in particular spots) from stars. We then synthesize the full spectra for any given stellar activity level. The method can be extended to non-solar spectral types. * dedicated to the late Juan Fontenla, who provided the elementary, calculated spectra of the solar features
Carolingian observations of transient celestial phenomena: Comets, aurorae, sunspots, halos, etc.
Neuhäuser, Ralph
During the lives of Charlemagne (AD 747-814) and Louis the Pious (778 -840), many transient celestial observations were recorded in various chronicles: Royal Frankish Annals, Annals of St. Bertin, Fulda, and Xanten as well as vitae on Charlemagne and Louis the Pious (by Nithard and a so-called anonymous astronomer). Apart from comets, halos, meteors, bolides, aurorae, and eclipses, there are also one or two sunspot records. Several of the transient phenomena were reported within a negative context, as bad portent or omen, or at least as a call to repent.The perihelion passage of the large comet of AD 837 (1P/Halley) is reported in the annals of Fulda and Xanten, letters of Einhard and Lupus, and in a poem by Florus of Lyon. The accounts in the Annals of Fulda and in the Anonymous Vita yield celestial rough positions with dates, which we use together with those from China and Arabia to improve the orbit of 1P/Halley.The Royal Frankish Annals for AD 807 report one solar and three lunar eclipses, a lunar occultation of Jupiter, a sighting of "war armies" in a full moon night with an eclipse (halo display or aurora), and a spot on the sun described as Mercury transit observed for 8 days (March 807). The latter was observed during the arrival of a delegation from Baghdad, for which technology transfer is reported, so that knowledge transfer in astronomy may also have happened. Having compiled all other sunspot and aurora observations from the 9th century, we can date Schwabe cycle maxima and minima. The completeness of Carolingian eclipse records was 100% from the visit of a delegation from Baghdad (March 807) until the death of Charlemagne (January 814), but was lower by more than a factor of four after the death of Charlemagne, reflecting the decline of the Carolingian empire. Since the celestial phenomena in the Anonymous Vita show some deficiencies regarding knowledge in astronomy and computus, we argue that it was not written by an astronomer.
Reconstructed sunspot positions in the Maunder Minimum based on the correspondence of Gottfried Kirch
Neuhäuser, Ralph
We present reconstructed sunspot positions based on observations reported in letters between Gottfried Kirch and other contemporary astronomers from AD 1680 to 1709, i.e. in the last decades of the Maunder Minimum. The letters to and from Gottfried Kirch were written in Latin and/or German language (edited by Herbst 2006). The letters and observations from Kirch are mostly by Gottfried Kirch, but some also by his 2nd wife Maria M. Kirch and their son Christfried Kirch. The partners of the letter exchanges regarding sunspots are G. Schultz, J. Hevelius, G.S. Dörfel, G. Teubner, G.C. Eimmart, J.A. Ihle, J.P. Wurzelbaur, S. Reyher, J.H. Hoffmann, G.W. Leibniz, O. Römer, L.C. Sturm, H.C. von Wolffsburg, and C.G. Hertel. Using excerpts from the letters, some with drawings, we found 34-35 sunspot groups (often for several days in a row or with interruptions). We also found 19 explicit spotless days, several of them new (dates without any previously known observations). We were able to constrain the heliographic latitude for 19 sunspots - four of them completely new (one group 1680 May 20-22 from Kirch and Ihle, one to two groups 1680 Jun 15-23 for Kirch, one group 1684 May 6 from Ihle, and one group 1688 Dec 14-15 from Kirch), while the others mostly agree with previously published values for those dates by others. These data allowed us to amend the butterfly diagram for the Maunder Minimum. By comparison of these observations with the sunspot group catalog in Hoyt & Schatten (1998), we noticed a number of discrepancies, e.g. that the dates for most British observers in this time period as listed in Hoyt & Schatten (1998) are in their original Julian style, not converted to the Gregorian calendar (10-11 day offset to Hoyt & Schatten). Furthermore, in at least four cases, when Hoyt & Schatten report 2 or 3 groups for Kirch or others, we found in the letters to and from Kirch only one group each, sometimes with 2 or 3 spots.
Celestial signs in the 8th century Syriac Chronicle of Zuqnin - their cultural and scientific relevance
Neuhäuser, Dagmar L.
The world Chronicle of Zuqnin is written in AD 775-776; for the last decades, the author is both an eyewitness of events and a reporter of other first-hand accounts; for previous centuries, he often quotes partly from lost chronicles (including Pseudo-Joshua the Stylite). The chronicle survived in one only manuscript, which is an autograph (Vat. Syr. 162). The Chronicler wrote in Syriac in the monastery of Zuqnin near Amida, now Diyarbakir, Turkey; the first and last folios are lost together with the name of the author; the Chronicle is divided into four parts, translated partially to French and entirely in English (e.g. Harrak 1999, 2017).We carefully studied the celestial phenomena in parts III and IV. Already Dall'Olmo (1979, Journal Geophysical Research 84, 1525) and Schove (1984, Chronology of eclipses and comets AD 1-1000) suggested aurorae from part IV, but with uncertain dating and shortcomings in the translation. Neuhäuser & Neuhäuser (2015 AN 336, 225) dated these two credible auroral displays to the summers of AD 772 and 773 and discussed them in connection with the radiocarbon variation around AD 775. We found a few more, earlier likely true aurorae.The detailed description of comet 1P/Halley in AD 760 with positions and dates allows us to improve the orbit. The chronicle reports additional objects called nayzko for lance, which we try to classify as comets in today's sense or other, comet-like phenomena ? taking into account the sources of our Chronicler and how he used them.The Chronicle reports a number of halo effects, e.g. a cross and various arcs, some connected to historical events or biblical narratives. It includes several colourful drawings of celestial phenomena, e.g. aurorae, comets and halos, partly observed by the author; for others, we discuss whether they are based either on other eyewitnesses who reported to the author, or whether they are modelled by him after previous similar observations and/or his written sources.
Comments on recent interpretations of transient phenomena from Babylonia
Neuhäuser, Dagmar L.
Recently, there were two publications about historical celestial observations reported in the "Astronomical Diaries and related texts from Babylonia" (Sachs & Hunger 1988-1996): Sigl et al. (2015 Nature 523, 543) surveyed for observations possibly indicating atmospheric dust layers due to volcanic eruptions, and Hayakawa et al. (2016 EPS 68, 195) searched for certain keywords presumably pointing to the Aurora Borealis.Sigl et al. (2015) interpreted multiple "billowing lunar halos", repeated incidences of "dense haze and mist" within the same year as well as "redness" and "halos" as indication for volcanic eruptions, but billowing and non-billowing halos as well as haze and mist are typical atmospheric phenomena often reported in the "Diaries", in particular during incoming depressions, while volcano-induced atmospheric phenomena like stars appearing fainter, abnormally strong fiery, purple light during twilight, Bishop's ring with a bluish-whitish disk around the sun and green, pale blue, and azure blue sun and moon (Minnaert 1993, Light and color in the outdoors) were never reported.In addition to three previously suggested aurorae in the "Diaries", Hayakawa et al. (2016) propose three "torches", two "red rainbows" and a "rainbow before (sun)rise" as aurorae, partly not even at night-time, but they overinterprete the text and omit alternative interpretations such as bolides or real red rainbows; e.g. one of their "likely" cases ("before (sun)rise, a rainbow stretched in the NW direction" in BC 385 Dec) can easily be a high-altitude rainbow in today's sense with the sun still slightly below the horizon ("before (sun)rise") at the opposite direction (SE) ? not considered in Hayakawa et al. (2016).We will not only present alternative explanations for all those observations and reflect on methodological problems, but we will also philologically discuss previously suggested and newly found wordings regarding transient celestial phenomena from both the Diaries and Omina.
Constraining the allowed mass Warm Dark Matter using estimates of the total satellite population of the Milky Way
Newton, Oliver
Surveys of the Milky Way's close environs remain incomplete both in depth and sky coverage, producing only a partial census of its complement of dwarf satellite galaxies. Estimates of this population can be used to place tighter constraints on the allowed masses of candidate Warm Dark Matter (WDM) particles. We present estimates of the total satellite population of the Milky Way (MW) made using observations from both the Sloan Digital Sky Survey (SDSS) Data Release 9 and the Dark Energy Survey (DES) surveys, which together cover nearly half of the sky. These estimates are made by the application of a Bayesian inference method to a set of 5 highly-resolved DM-only MW analogues from the Aquarius simulation suite, and predict fewer satellites than previous studies that only used earlier SDSS data releases. We find only a weak dependence on MW halo mass at fainter absolute magnitudes and predict that half of this total population is potentially observable by the forthcoming Large Synoptic Survey Telescope (LSST). We compare this prediction of the total satellite population in the standard cosmological model to predictions from different WDM cosmologies in order to tighten constraints on the allowed masses of candidate WDM particles.
Additional ALMA Observations of Major Mergers Among the Host Galaxies of Fast-growing, High-redshift, Supermassive Black Holes
Nguyen, Nathen
We present new ALMA band-7 data for a sample of twelve luminous quasars at z~4.8, powered by fast-growing super massive black holes (SMBHs) with rather uniform properties: the typical accretion rates and black hole masses are L/L_edd ~ 0.7 and M_BH ~ 10^9 solar masses. Our sample of twelve sources is a follow up of six pilot observations lead by Benny Trakhtenbrot. Our sample consists of six “FIR-bright” sources, which were individually detected in previous Herschel/SPIRE observations with star formation rates of SFR > 1000 Solar masses per year, and six “FIR-faint” sources for which Herschel stacking analysis implies a typical SFR of ~400 Solar masses per year.The dusty interstellar medium in the hosts of eleven of the twelve quasars is clearly detected in the ALMA data and resolved on scales of ~2 kpc, in both continuum (rest wave length ~ 150 micrometers) and [C II] with wavelength 157.74 micrometer line emission. The continuum emission is in good agreement with the expectations from the Herschel data, confirming the intense SF activity in the Quasar hosts. We detect companion sub-millimeter galaxies (SMGs) for two sources, one faint and one bright. This is ratio (1 in 6 targets having companions) is much lower than the ratio found in our pilot sample (1 in 2). While we argue that these major mergers are important drivers for rapid early SMBH growth, the smaller percent of companions implies that other factors are leading to the rapid growth, and are in fact more common than major mergers.
Magnetic field difference in young-embedded massive protoclusters and evolved massive protoclusters in M17
Nguyen-Luong, Quang
Magnetic fields play an important role in star formation. They affect how the molecular gas assembles mass to form denser filamentary structures and eventually fragments to form stars. It is only recently that observations of magnetic fields via dust polarization have become efficient with the emergence of new sensitive submm polarimetric cameras such as SCUBA2-POL on JCMT and infrared polarimetric camera SIRPOL. We present the submm and infrared polarimetric maps of that map the B-field inside the massive star-forming filaments M17SWex which host young-embedded massive protoclusters and the M17 giant HII region which host an evolved massive protocluster. We will disscuss the structures of the B- fields in the two similar regions but at different evolutionary stages to answer the questions: 1) What is the relative contribution of B-field to the energy budget in different phases?2) what is the role of B-fields in mass assembly from the filamentary network onto individual cores?3) Similarity or Difference between young-embedded and evolved massive protocluster environments?This leads to the understanding how mass is transferred, assembled and collapsed from the cloud scales to core scales and then evolve to star clusters.
Seeking for partnership to construct an astronomical observatory in the remote area of Vietnam
Nguyen-Luong, Quang
Tay Nguyen University is a local university in Buon Ma Thuot, Daklak, a highland part of Vietnam which as mountain peaks up to 1200-1600 m and a large portion of clear sky nights per years. Having 20000 students and 4000 students in the Science and Technology department, it deserves to have its own astronomy department. We are actively developing a plan to build an observatory in Tay Nguyen university for educational and training purposes. We currently have some partnership in development but we are still actively looking for new ones, especially in curriculum development and financial support. In this talk, I will describe the challenges that the project is facing and also the help that we are looking for. Detail of the project can be found here:cita.utoronto.ca/~qnguyen/FLO.html
Developing a sustainable astronomy education in Vietnam with external supports
Nguyen-Luong, Quang
Our previous IAU-OAD activities focus mainly on public audience in order to increase the awareness of astronomy in Vietnam. Now, while maintaining the energy of that spirit, we also expand our activities to leverage the educational and professional status of astronomy in Vietnam. To continue that development and progress toward a more sustainable development of astronomy in Vietnam, we are moving into new directions. First, we are conducting a joint project between Tay Nguyen University (Vietnam), NAOJ (Japan), Kyoto University (Japan) to build an observatory in Tay Nguyen university for educational and training purposes. The plan of the project was already set and the budget is planned. Secondly, we are actively send staffs and students abroad for training and research collaboration with international institutes such as Paris Observatory, Max Planck Institute for Radio Astronomy. Third and more importantly, we are setting a mechanism to welcome trained astronomers and use their talent to create more synergy in Vietnam, especially in under-developed part of the country.
X-ray spectroscopy of massive stellar winds: previous and ongoing observations of the hot star zeta Pup
Nichols, Joy
The massive stellar winds of hot stars have an important impact on galactic evolution, yet their structure and internal processes remain only partially understood. One of the best nearby laboratories for studying such massive stellar winds is the O4 If star zeta Pup. After reviewing existing X-ray observations from Chandra and XMM, we present a simulation of an 840 ksec upcoming Chandra HETGS observation. This simulation indicates that the increased S/N of this new observation will allow several major steps forward in the understanding of massive stellar winds. By measuring X-ray line strengths and profiles, we should be able to differentiate between various stellar wind models and map the entire wind structure in temperature and density. This legacy X-ray spectrum of zeta Pup will be a useful benchmark for future X-ray missions.
A Stellar Proper Motion Map of the Magellanic Clouds
Niederhofer, Florian
The Large and Small Magellanic Cloud (LMC and SMC) are recently acquired satellites of our Galaxy andare currently interacting both with each other and with the Milky Way. The dynamical interplay is most likely responsible for the complex morphology of the two Clouds and the formation of tidal features such as a stellar Bridge connecting the two dwarf galaxies and a gaseous Stream. Thanks to their close proximity (50-60 kpc), they provide a good opportunity to study in detail the kinematics of resolved stellar populations in an interacting pair of galaxies. However, precise and homogeneous stellar proper motion measurements across the LMC and SMC, needed to design dynamical models that describe the formation, orbital history and evolution of the Magellanic system, are still lacking.The ongoing near-infrared VISTA survey of the Magellanic Cloud system (VMC) is specially designed to study in detailmultiple aspects of this interacting pair of galaxies. Thanks to its multi-epoch nature, the VMC data can also be used to derive stellar proper motions. In this contribution, we will present first results from our ongoing project dedicated to measure the proper motions of large samples of stars across the Magellanic Clouds, showing for the first time the large scale velocity field within the Clouds and the small scale motions of individual stellar populations.
A wide and deep survey for low-luminosity quasars at z~5 with Subaru Hyper Suprime-Cam
Niida, Mana
Observational surveys for protoclusters in the high-redshift Universe are crucial to understand the formation and evolution of clusters of galaxies. Quasars have been sometimes used to discover protoclusters at high redshift. Quasars in protoclusters are interesting also to study the triggering mechanism of the mass accretion onto supermassive black holes and possible effects of the quasar activity to the evolution of protoclusters. Therefore quasar surveys at high redshift over a wide luminosity range are required. However there are only small number of low-luminosity quasars at z>5 identified so far, due to insufficient area and sensitivity in past surveys. We are searching for low-luminosity quasars at z~5 by using wide and deep optical imaging survey data obtained through the Subaru strategic program (SSP) with Hyper Suprime-Cam (HSC). This survey covers a wide survey area (~82 deg^2) and has deep sensitivity, which is ~3 mag deeper than SDSS, enough to observe faint quasars at z~5. We selected photometric candidates of low-luminosity quasars at z~5 by adopting the so-called Lyman-break method. Consequently, we obtained a large sample of quasar candidates at z~5 (224 objects) with a luminosity range of -27.4<m_1450<-22.4. we="" derived="" the="" quasar="" luminosity="" function="" (qlf)="" at="" z~5,="" taking="" into="" account="" of="" survey="" and="" contamination="" galactic="" stars="" galaxies.="" as="" a="" result,="" faint="" end="" slope="" our="" qlf="" is="" flatter="" than="" that="" previous="" studies="" (giallongo="" et="" al.="" 2015).="" trend="" consistent="" with="" z~4="" using="" hsc="" data="" (akiyama="" 2018).="" in="" this="" presentation,="" would="" like="" to="" discuss="" also="" redshift="" evolution="" number="" density.<="" p="">
</m_1450<-22.4.>
Broadband spectral study of M33 X-6 with Swift-XRT and NuSTAR: a new extragalactic Z-type source?
Nikolaeva, Svetlana
We present results of a broadband (0.3-20 keV) spectral analysis of the luminous X-ray binary system X-6 located in the nearby spiral galaxy M33. NuSTAR has measured its spectrum above 10 keV for the first time. We utilized Swift-XRT archival data to extend energy coverage to below 3 keV. The spectrum is well described by a slim accretion disk model with a maximal temperature of ~2 keV at the inner disk radius of a few kilometers. There is also evidence for an additional hard spectral component at energies above 10 keV. These results indicate that M33 X-6 may belong to the class of Z-type sources, well known in our Galaxy, in which near-critical accretion takes place on a neutron star with a low magnetic field.
Optical and X-ray study of V404Cyg during its activity in the Summer 2015.
Nikolaeva, Evgeniya
We have observed optical outburst of theblack holeX-ray binary V404 Cygin Summer 2015 by using 1.5-meter Russian-Turkish optical telescope (RTT150) facilities.The velocity of shell expansion was measured basedon hydrogen and helium lines. From June 22 to June 28 2015shell expansion velocity decreased from 650 to 350 km/s as measured by Ha and Hß lines, from 450 to 300 km/s as measured by lines of HeI 6678 Å, 7065 Å and from 580 to 300 km/as measured by HeII 4685 Å line. Thus, it can be concluded the shellexpansion occurred with decelerationin the indicated period. The hydrogen and helium line formation regions in different stages of ionization are situated at different radial distances from the center of the star.The X-ray light curves of V404 Cyg were studied during its outburst activity in June and December 2015 by using open archive data of the Swift XRT orbital observatory. The power spectra constructed by using optical and X-ray light curves showed the same slope within the error limits - -1.9 +/- 0.09 and -1.85 +/- 0.06. At frequencies from 0.002 Hz and below, a "flat area" was detected the X-ray power spectrum of V404Cyg. In the X-ray region, the power spectrum exhibits quasiperiodic oscillations at the frequency of 0.0137 Hz, its nature is unknown. It is assumed that the correlation of flow variability in the optical and X-ray ranges is caused by fluctuations in the rate of accretion near a compact source where X-ray photons are generated. X-ray photons go then into density fluctuations in the expiring hot baryon jet radiating in the optical and X-ray ranges.
Optical Study of Bright FERMI/LAT Blazars
Nikolashvili, Mariam
To study optical variability of extragalactic sources during last twenty years we are conducting in Abastumani Observatory a long-term monitoring campaign using dedicated telescopes, which allowed collecting 300000 CCD frames during ~3100 nights. This extensive monitoring campaign a few dozen blazars first five years was carried out in BVRI bands and later on from 2002 mainly in R band using the 70-cm meniscus (f/3, SBIG ST6 and Apogee Ap6E) and 125-cm Ritchey-Chretien (f/13, Apogee Ap6E) telescopes. Most dense coverage of selected LAT brightest sources has been undertaken after lunch of FERMI satellite in 2008. The frames have been reduced using Daophot II and homogenous sample of light curves have been constructed. Most sources show wide range of variability (long-term, IDV and micro-variability). We present optical light curves of these most well sampled sources.
SMA Spectral Line Survey of the Proto-Planetary Nebula CRL 618
Nimesh, Patel
Carbon-rich Asymptotic Giant Branch (AGB) stars are major sources of gas and dust in the interstellar medium. AGB stars remain in their evolutionary stage for 1 to 10 Myrs, during which they have very high mass loss rates that increase at the end. During the brief (~1000 yr) period in the evolution from the AGB to the Planetary Nebula (PN) stage there are dramatic changes in the morphology from nearly spherical symmetry, to bipolar, quadrupolar and more complex structures, with the development of both slow and fast (100 km/s) outflows. The molecular composition of these objects' cirumstellar envelopes also evolves from being similar to that of parent AGB star (mainly diatomic and small polyatomic species), to more complex molecules (including ions).We have started an observational study of a sample of Proto-Planetary nebulae (PPN) with the Submillimeter Array (SMA) to carry out spectral-line surveys of ~60 GHz frequency coverage in the 345 GHz band (similar to our published IRC+10216 line survey of 2011). Here we present results from the spectral line survey of the carbon-rich PPN CRL 618, covering a frequency range of 281.9 to 359.4 GHz. Observations were carried out in January 2016, September 2017, and November 2017, with the SMA in compact (3" angular resolution), very extended (0.5”), and extended (1.0") configurations, respectively.More than 1100 lines were detected in CRL 618. The majority of them can be attributed to HC3N and c-C3H2, and their isotopologues. About 350 lines are as yet unassigned. The continuum emission is unresolved even at 0.5" resolution. Several hydrogen recombination lines are detected from the central HII region. Lines of CO, HCO+, CS show the fast outflow wings, while the majority of molecular emission arises from a compact region of about 1" diameter. We present LTE modeling and rotation temperature diagram analysis of HC3N, c-C3H2, CH3CN, and their isotopologues.
The Greenland Telescope Project
Nimesh, Patel
The Greenland Telescope is a new 12-m diameter antenna located at Thule Airbase in Greenland. The primary scientific goal of the project is to resolve the shadow of a super massive black hole (Inoue et al. 2014, Radio Science, 49, 564). The telescope was formerly the ALMA North America prototype antenna that was awarded to the Smithsonian Astrophysical Observatory (SAO) in 2011 by the NSF. The partnering institute, Academia Sinica Institute of Astronomy & Astrophysics (ASIAA), has led the effort to retrofit and rebuild the telescope in Thule, to make it operable in extremely cold environment (-70 C). Currently there are three receivers operating at 86, 230 and 345 GHz. The antenna assembly was completed in August 2017. Various commissioning tests are in progress (January-March 2018) including optical pointing, radio pointing at 86 GHz, focus optimization at 86 and 230 GHz, and implementation of continuum synchronous detection system with a hexapod controlled nutating subreflector. A hydrogen maser was installed at the antenna in September 2017. In January 2018, VLBI observations were carried out with several antennas including the South Pole Telescope and ALMA, operating at 230 GHz, as part of the Event Horizon Telescope (EHT) "dress rehearsal". In February 2018 the antenna joined the Global millimeter VLBI Network at 86 GHz, observing SiO masers. The Greenland telescope will participate in the EHT campaign in April 2018 to image the shadow of the Black Hole in M87. In future, the antenna is planned to be relocated at a high altitude site (3200 m) near the Summit station in Greenland, which will allow observations at frequencies above 345 GHz (Matshushita et al. 2017, PASP, 129,025001) to allow 345 GHz VLBI observations, and also single-dish science observations approaching terrahertz frequencies (Hirashita et al. 2016, PASJ, 68,1).
On the relation of star formation and molecular cloud structure of Orion A GMC
NISHI, Ryoichi
We analyze the Gaia DR2 stellar data, comparing with the large area rado map of Orion A Giant Molecular Cloud (GMC), to investigate the aggregate star formation process in GMCs. As a part of Nobeyama Radio Observatory of NAOJ Star Formation Project, we paerformed large area mapping observation of Orion A, in 13CO, C18O and some other molecular lines using the Nobeyama 45-m radio telescope. We investigated both the frame structure of Orion A and the detailed structure of dense cores in Orion A. On the other hand, we have picked up stellar associations around Orion A with the Gaia DR2 data, and are investigating the physical characteristics of them, such as the structure, the overall motion, the interenal motion, the age, and so on. We will investigate the relation of thess characteristics and the structure of Orion A and will discuss star formation process in GMCS.
Inspiring Global Grassroots Learning Networks with Astronomy
Noel-Storr, Jacob
The mission of InsightSTEM is to democratize STEM (Science, Technology, Engineering, and Mathematics) knowledge through exploration. We work with grassroots networks around the world consisting of high school and university students, teachers, families and communities, and young STEM professionals to help them engage and inspire others in STEM education. Astronomy is well known to be an inspiring topic to use in STEM engagement programs but is often overlooked in the preparation of STEM outreach facilitators in countries with lower Gross Domestic Income per Capita where conducting astronomical research and astronomical research facilities may be a rarity. Often in the communities we work with, we find that inspiring topics, such as astronomy, can be overlooked in favour of more survivalistic topics centring around safety and public health. We recognize that astronomy may be lower on the list of ‘need to learn’ topics, but believe it is a mistake to overlook the inspirational value for learners in these nations and we strive, along with our grassroots Insightful Teachers, High School Scholars, Campus Ambassadors, and Young STEM Professionals, to include astronomical topics and explorations in their professional learning to engender a more inspirational and aspirational slant to STEM education and outreach activities, to move the next generations towards their future place in the world. In this presentation, we will share ways that we have developed economical means of enabling our InsightSTEMmers to inspire others and engage them in the exploration of genuine astronomical and space mission data that is available to everyone on the planet.
Does the Newtonian Gravity "Constant" G Vary?
Noerdlinger, Peter
Does the Newtonian Gravity "Constant" G VaryA series of measurements of Newton's gravity constant, G, dating back as far as 1893, yielded widely varying values, the variation greatly exceeding the stated error estimates (Gillies, 1997; Quinn, 2000, Mohr et al 2008). The value of G is usually said to be unrelated to other physics, but we point out that the 8B Solar Neutrino Rate ought to be very sensitive. Improved pulsar timing could also help settle the issue as to whether Greally varies. We claim that the variation in measured values over time (1893-2014 C.E.) is a more serious problem than the failure of the error bars to overlap; it appears that challenging or adjusting the error bars hardly masks the underlying disagreement in central values. We have assessed whether variations in the gravitational potential due to (for example) local dark matter (DM) could explain the variations. We note that true variations in G would be associated with variations in clock rates (Derevianko and Pospelov 2014; Loeb and Maoz 2015), which could mask changes in orbital dynamics. Bernabei et al (2003) also found evidence for DM penetrating deep underground at Gran Sasso. If, indeed, variations in G can be tied to variations in gravitational potential, we have a new tool to assess the DM density.
Superflares on Solar-Type Stars
Nogami, Daisaku
Super?ares are de?ned as ?ares which are over 10 times more energetic (=1033 erg) than largest ?ares ever observed on the Sun, and many super?ares have been found on many solar-type stars, i.e. G-type main sequence stars in the Kepler-spacecraft data. Statistical analyses indicate that the frequency distribution to the ?are energy of the super?are is almost consistent with that of the Sun. Many of super?are stars show quasi-periodic variations with timescales of about 1 to 30 days. Spectroscopic measurements of the projected rotation velocity suggest that these variations are due to rotation of super?are stars with large starspots. The size distribution of starspots shows the power-law distribution which is on the same line of the size distribution of relatively large sunspots. The frequency-energy distributions for ?ares originating from spots with various sizes are the same for solar-type stars with super?ares and the Sun. These results suggest that the magnetic activity on solar-type stars with super?ares and that on the Sun is caused by the same physical processes. Long term monitoring of the chromospheric activity and research on possible coronal mass ejections accompanying with super?ares will give us an insight on the e?ects of super?ares on the planetary environment, and possible extreme space weather events on the Earth.
ALMA Observations of Sulfur-bearing Molecules in Protoplanetary Disks
Nomura, Hideko
Protoplanetary disks are the natal place of planets and ALMA observations are now revealing the physical and chemical structure of planet forming regions in the disks. Understanding chemical components of gas, dust and ice in the disks is essential to investigate the origins of materials in the plants. Meanwhile, molecular lines are useful to trace physical properties of astronomical objects. Sulfur-bearing molecules are known as shock tracers and have been recently observed around protostellar disks surrounded by infalling envelope (e.g., Sakai et al. 2017, Miura et al. 2017). I will report the result of our ALMA observations of sulfur-bearing molecules towards ten T Tauri disks in the Taurus molecular clouds. It is thought that eccentricities of planetesimals are excited due to gravitational interaction with (proto)planets in protoplanetary disks. As a result, bow shocks are formed around the icy planetesimals and they evaporated via the shock heating. The evaporation rates and orbital evolution of such icy planetesimals have been investigated (Tanaka et al. 2013, Nagasawa et al. 2014). In this work we aimed to observe the molecules evaporated from icy planetesimals with ALMA as a possible tracer of (proto)planet formation in the disks. We selected transition lines of sulfur-bearing molecules as a tracer; however, the lines were undetected by our observations, unfortunately. The obtained upper limits of the line intensity give us some information, thanks to high sensitivity of ALMA. Based on the observed upper limits and model calculations, we discuss the fractional abundances of sulfur-bearing molecules in the ice mantle on grains in the outer regions of the disks and their relation with those observed in comets in our Solar System as an analogues of comparison between the fractional abundances of complex organic molecules recently found in protoplanetary disks and those found in comets (e.g., Oberg et al. 2015; Walsh et al. 2016).
Magnetic Flux Emergence Rates of Sunspots: Observations Compared to Simulations
Norton, Aimee
We present flux emergence rates of active regions using vector magnetic field data as observed with HMI/SDO. Observed rates can provide feedback to those who simulate the subsurface emergence process that we cannot observe directly. Signed flux emergence rates for sunspots average 5 x 10^{19} Mx per hour. The observed rates from HMI are put into context with results previously reported from observations using various instruments and simulations. A clear trend is seen that larger flux regions emerge faster than smaller flux regions. Observed emergence rates (df/dt) scale with total signed peak flux (fmax) as a power law with an exponent of 0.36, i.e., df/dt = A(fmax )0.36. The rates reported here may assist in constraining the choice of boundary and initial conditions in simulations which have already demonstrated that rates increase when a flux tube has higher buoyancy and twist, or is in the presence of a strong convective upflow.
Possibility to locate the position of the H2O snowline in protoplanetary disks through spectroscopic observations
Notsu, Shota
Observationally locating the position of the H2O snowline (e.g., Hayashi et al. 1981, 1985) in protoplanetary disks is crucial for understanding the planetesimal and planet formation processes, and the origin of water on the Earth. The velocity profiles of emission lines from disks are usually affected by Doppler shift due to Keplerian rotation. Therefore, the line profiles are sensitive to the radial distribution of the line emitting regions. In our previous works (e.g., Notsu et al. 2016&2017, ApJ), we calculated the chemical composition of the disks around a T Tauri star and a Herbig Ae star using chemical kinetics, and then the ortho-H216O line profiles to identify that lines with small Einstein A coefficients and relatively high upper state energies (~1000K) are dominated by emission from the hot midplane region inside the H2O snowline, and therefore through analyzing their profiles the position of the H2O snowline can be located. In addition, we analyzed the ortho- and para-H218O molecular lines to find that they trace deeper into the disk than the ortho-H216O lines since the number density of H218O is low (Notsu et al. 2018a, ApJ). Thus these H218O lines are potentially better probes of the position of the H2O snowline at the disk midplane, depending on the dust optical depth. Since the values of the Einstein A coefficients of sub-millimeter candidate water lines are low, H218O and para-H216O lines with relatively lower upper state energies (~ a few 100K) can also locate the position of the H2O snowline. There are several candidate water lines that trace the position of the H2O snowline in ALMA Bands 5-10. Finally, we have proposed the water line observations for a Herbig Ae disk HD163296 in ALMA Cycle 3, and partial data were delivered. We constrain the line emitting region (the location of the H2O snowline) and the dust properties from the observations.
Asteroid Families Portal
Novakovic, Bojan
A possible way to cope with the large size and complexityof data accumulated in the recent years is development of web-portals.Such portals are often devoted to specific purposes, and allow scientiststo easily review and analyze different data.Here we present an open access web portal devoted to asteroid families, namely theAsteroid Families Portal (AFP). The aim of the AFP is to collect different dataabout asteroid families and closely related subjects. The portal can be used to quicklyassess and visualized data, but this should not be its only purpose. Our aim is to providedifferent tools and methods to analyze collected data and to study families ingeneral. For instance, the well-known Hierarchical Clustering Method (HCM) could beemployed on-line to obtained the most recent list of a family members. Other servicescurrently implemented at the AFP includes an automatic procedure to obtain a list of familyinterlopers and a list of the most recent pear-reviewed papers on asteroid families.For all available tools we are planing to provide two levels of application.First should allow to use the tools in as simple as possible way, withpredefined (i.e. default) parameters. Second level should be mainly devoted toresearchers that already have an experience with these methods, and itwill allow to set different parameters.The AFP is foreseen to be continuously updated and upgraded.For instance, we foresee to offer a fully automatic estimationof family age, based on the so-called V-shape method.We also aim to develop an algorithm that will provide different basic information aboutan asteroid family, such is the size of the parent body and its corresponding escape velocity,the slope of the magnitude-frequency distribution, etc.
Dwarf galaxies and their globular cluster systems: data analysis and non-stationary formation model
Nuritdinov, Salakhutdin
Because of the deficiency problem of dwarf galaxies (DG) in the Universe relatively to quantity of usual Hubble galaxies the research of those which contain the globular cluster systems (GCS) is of interest. We have collected the data of observations for 76 DG containing the GCS. About 95% of them are elliptical DG. We have received that the absolute magnitude of DG depends linearly on values of both the metallicity and logarithm of quantity of globular clusters around them. A dependence of the ellipticity degree of DG on average quantity of globular clusters is studied. An empirical dependence of masses of DG on quantity of globular clusters around them is also found. We have offered a non-stationary model of the collapsing protogalaxy against a background of which both the poor GCS and the dwarf galaxy can be formed.
Towards the formation theory of protoclusters and superclusters of galaxies: method of random matrices
Nuritdinov, Salakhutdin
At an earlier stage of the Universe evolution the influence of effects of high non-stationarity and turbulence on a separated volume has a random character. It is interesting to find out whether the statistical effect of the randomness can bring to the formation of volume protoclusters and superclusters of galaxies or we will have an elongated formation. A computer program of this process is worked out by the method of random matrices. In the report the algorithm and preliminary results will be given.
Global Estimation of Nutation Components from VLBI Data
Nurul Huda, Ibnu
Nutation is mainly produced by cyclic gravitational forces exerted by the Sun and the Moon on the Earth equatorial bulge. In turn it is composed of several harmonic components. These components are commonly estimated from celestial pole offset (CPO) time series, which are produced from VLBI time delay analysis. However, as CPO are determined independently for each 24 hour VLBI session, the celestial pole offsets can present uncorrected systematic effect stemming from the geometry of the antenna network. The instability of the observed sources also makes this approach questionable. On the other hand the nutation components can be treated as global parameters and directly fitted to VLBI time delay. In this work, we apply both approaches over 30 years of VLBI observations and show that the global approach give more consistent and precise estimates of the nutation components.
Bringing Radio Astronomy to the poorest community
obi, ikechukwu
We describe the set up of a "Poor man Radio Telescope" that is based on the software defined radio (SDR) systems that will serve as an indispensable tool in bringing the techniques and thrills of radio astronomy to the reach of the poorest community in Nigeria. The target audience are primary and high school students who have little or no knowledge in the invisible world of radio astronomy in contrast to the visible optical astronomy. The radio telescope comes along with some hands-on-exercises that can be incorporated into the schools curriculum. We discuss our experiences in schools where this radio telescope has been introduced.
Star formation rate calibrations: the effect of the upper mass limit of the IMF
Obi, Ikechukwu
We construct a large library of star-burst models for a large range of physical parameters using our spectrophotometric code GRASIL. The adopted Simple Stellar Populations (SSP) are computed at various metallicities and upper mass limits of the Initial Mass Function (IMF), using PARSEC (PAdova TRieste Stellar Evolution Code) evolutionary tracks. We derive analytic relations that provide the star formation rates (SFR) of star forming galaxies from their UV to radio continuum and main recombination lines luminosities, by explicitly accounting for different IMF upper mass limit and metallicites. The relations are particularly useful for young star forming systems not strongly attenuated by dust, with a FIR luminosity that is only a fraction of the bolometric one. We discuss possible diagnostics for the IMF upper mass limits.
Discovery of a LAE overdensity in a concentrated region of damped Ly-alpha systems
Ogura, Kazuyuki
To investigate the early phase of the galaxy evolution, we focus on two populations of gas-rich young systems, damped Lya systems (DLAs) and Lya emitters (LAEs). The DLA is a class of quasar absorptionline systems with NHI>1020.3 cm-2 and is a key population to understand the galaxy evolution in the following respects: (1) DLAs provide a powerful tool to investigate the nature of the cold gas at high redshift since they trace the intervening gas that can be detected as a strong Lya absorption line on quasar spectra regardless of the luminosity of their stellar component, and (2) it is known that DLAs dominate the neutral-gas content in a wide redshift range and they are thought to be gas reservoirs for the star-formation. Another important population of young galaxies is the LAE. Typical mass and age of LAEs are 108-109 Msun and order of 100 Myr, respectively. Although most of the galaxy counterparts of DLA at z>2 that have been identified to date show the Lya emission, the relation between those two population is still unclear.We focus on concentrated regions of DLAs to investigate the physical relationship between DLAs and LAEs. Here we define the concentrated region of DLAs as a region where three or more DLAs distribute within a (50 Mpc)3 cubic box. We conducted narrow-band imaging observations of LAEs in the J1230+34 field, where four DLAs present, with Subaru/Suprime-Cam. In the entire target field of ~50 Mpc scale, we have found no difference between the obtained Lya luminosity function and those in blank fields at similar redshift. The frequency distribution of Lya rest-frame EW is also not different from those in blank fields and a overdensity region at similar redshift. On the other hand, in the small scale of ~10 Mpc, we have found a possible overdensity of LAEs around a DLA with highest NHI (logNHI=21.08 cm-2) in the J1230+34 field. This may correspond to a possible discovery of a gas-rich protocluster traced by DLAs for the first time.
Robust profile decomposition for extragalactic spectral line surveys
Oh, Se-Heon
We present a novel algorithm which is based on a Bayesian Markov Chain Monte Carlo (MCMC) technique for performing robust and reliable profile analysis of a data cube from either single dish or interferometric radio telescopes. It fits a set of models comprised of a number of Gaussian components given by the user to individual line-of-sight velocity profiles, then compares them and finds an optimal model based on the Bayesian Inference Criteria computed for each model. The decomposed Gaussian components are then classified into bulk or non-circular motions as well as kinematically cold or warm components. The fitting based on the Bayesian MCMC technique is insensitive to initial estimates of the parameters, and suffers less from finding the global minimum in models given enough sampling points and a wide range of priors for the parameters. It is found to provide reliable profile decomposition and classification of the decomposed components in a fully automated way, together with robust error estimation of the parameters as shown by performance tests using an artificial data cube. This is an essential feature for profile analysis of the large number of data cubes expected in Square Kilometre Array (SKA) pathfinder surveys. We then apply the newly developed algorithm to a combined HI data cube of the Large Magellanic Cloud (LMC) from the Australia Telescope Compact Array (ATCA) and Parkes radio telescope. The results show highly complex HI structure and kinematics in the galaxy.
Application of Generative Adversarial Network to Machine Learning Classification of Gravitational Wave Data
Oh, Sang Hoon
We investigate a feasibility to utilize Generative Adversarial Network (GAN) in gravitational wave (GW) data analysis in order to enhance multivariate classification of GW signals and noise transients. Multivariate classification using machine learning algorithms (MLAs) was applied to auxiliary channel data of GW detectors in order to discriminate glitchy time and clean time in the gravitational wave channel (Biswas et al. 2013). Significant deficiency of the glitch sample with respect to the clean sample makes it easy to train MLAs to classify inputs in favor of the clean category. The size of glitch sample in the evaluation data set also limits the lowest false positive rate (FPR) estimation which is one of the figures of merit to verify the performance of MLA classifiers. Using GAN we intend to generate fake glitches to increase the glitch sample, achieving the balance between the training data set. We anticipate that a fake glitch generator can be utilized in various tests for GW data analysis such as new search algorithms and classifiers.
Super DIOS mission
Ohashi, Takaya
We are studying an improved DIOS (Diffuse Intergalactic Oxygen Surveyor) program for a launch year after 2030. The aim of Super DIOS is an X-ray exploration of warm-hot intergalactic medium using emission and absorption lines, measured with TES microcalorimeters. This mission will perform wide field X-ray spectroscopy with FOV of about 30 arcmin and energy resolution of a few eV, but with much improved angular resolution, than the original DIOS, of about 10 arcseconds. Besides the WHIM science, gas dynamics, distribution of elements, and other physical properties of plasmas will be studied with very high sensitiviey for cluster outskirts, supernova remnants, normal and active galaxies, and Galactic interstellar medium. We will describe the Super DIOS mission and its expected science.
SWIFT/XRT Observations of Cataclysmic Variables
Ok, Samet
Abstract Cataclysmic variables (CVs) consist of a white dwarf that accretes matter via Roche-lobe overflow from late-type donor stars. The orbital periods of these close binaries lie between ~80 min and ~10 hours. These are WD analogues of the low-mass X-ray binaries. These systems are very important laboratories which offer enormous diagnostic power for accretion physics and allow a direct mass measurements. CVs radiate in a wide energy range from infrared and optical bands to the hard X-rays. The main emission components in the case of the WDs with a weak magnetic field are the companion star which is a dwarf star with temperatures of 3500 - 4000, the accretion disk or accretion column near the WD surface radiating in X-rays. In this study, we have undertaken a survey of CVs using Swift/XRT instrument to investigate their optical and X-ray luminosity relation. Such a study has been done before for dwarf novae in quiescence. In addition to this study, we used more DNe objects and also magnetic CVs.
Structure of dark matter haloes of Milky Way satellite galaxies in SIDM universes
Okamoto, Takashi
CDM has some difficulties in explaining the small-scale structure of dark matter halos, such as central density distribution of the dark matter halos of the Milky Way satellites. These problems can be resolved by invoking galaxy formation processes because the central density of low-mass halos can be lowered by strong feedback. This fact alone, however, does not mean that CDM is consistent with observations because galaxy formation processes are tuned to reproduce observations. To observationally discriminate CDM from other dark matter models such as warm dark matter (WDM) and self-interacting dark matter (SIDM), we have to carry out galaxy formation simulations assuming these dark matter models and appropriately tuned galaxy formation processes to reproduce basic observational properties such as the satellite luminosity functions. We have implemented SIDM models by Loeb and Weiner (2011), of which the interaction cross-section depends on the relative velocity between two SIDM particles. The SIDM subhalos have cored profiles and much less abundant than the CDM subhalos. We report the difference between the structure of the CDM and SIDM subhalos when we tune the baryonic physics to reproduce the observed luminosity function of the Milky Way satellites.
Report on the West African International Summer School for Young Astronomers (WAISSYA)
Okere, Bonaventure
The West African International Summer School for Young Astronomers (WAISSYA) is a week-long introduction to astronomy for university students and teachers from West Africa, organized by a collaboration of scientists from Nigeria, Ghana, Gabon, Canada, and Germany. WAISSYA is held bi-annually -- so far in Ghana (2017) and Nigeria (2013 and 2015). WAISSYA's vision is to: (1) Contribute to building a critical mass of astronomers in West Africa; (2) Contribute to empowering young West Africans in becoming scientific leaders; and (3) Share ideas about teaching and learning between West Africa and North America / Europe. We will highlight four major aspects of WAISSYA and their significance to Astronomy for Development in West Africa: (1) our innovative curriculum focusing on “inquiry,” in which students ask and investigate their own mini-research questions in small teams; (2) an authentic research experience for graduate students (in 2017 at the new Ghana Radio Observatory); (3) "paired-teaching," in which international partners teach together to learn new teaching methods; and (4) evaluations to measure the effectiveness of the program.
Multiple Absorption Systems in the Lines of Sight to Quadruply Lensed Quasar H1413+1143 As a Probe of the Circumgalactic medium around Dwarf Galaxy
Okoshi, Katsuya
We present the first measurement of differences in MgII absorption strength in three intervening absorbers at redshift z=1.66, 2.068, and 2.097, which are also identified as (sub-)Damped Lyman alpha (DLA) absorption systems, in the four spectra of the quadruply lensed and broad absorption-line quasar H1413+1143, often referred to the “Cloverleaf” from highly spatial resolution and high signal-to-noise (S/N) spectroscopy with an optical multi-mode spectrograph, the Kyoto tridimentional spectrograph II (Kyoto 3DII) on board the Subaru telescope. We find that significant metal absorptions are detected in one and/or more components in the spatially-resolved spectra toward H1413+1143. This suggests that chemical enrichment differs at least on scale of about 10 kpc within the separation of sightlines similarly to the variation of the other metal absorption and HI absorption strengths. Specifically, we find that all systems at z=1.66 and three ones at z=2.068 in the four sightlines are strong MgII systems while only one system at z=2.097 is identified as a strong MgII system. The rest equivalent widths of MgII absorption lines change by factors within 2 for the multiple absorption systems at z=1.66 and 2.068. We will discuss the observed variation of low-ionization absorption strengths in comparison to that of high-ionization ones. Furthermore, host galaxies giving rise to both damped Lyman alpha absorption and the multiple metal absorption lines in the spatially-resolved spectra toward H1413+1143 will be discussed on the basis of highly spatial resolution and high S/N spectroscopy with Kyoto 3DII observation.
Quiet-time modulation of Cosmic Rays in the High and Mid latitudes
Okpala, Kingsley
The Heliosphere and geomagnetic field modulate cosmic rays of galactic origin. The mutual (and mutually exclusive) contribution of both heliospheric and geomagnetic conditions to galactic cosmic rays (GCR) modulation is still an open question. While the rapid-time association of the galactic cosmic ray variation with different heliophysical and geophysical phenomena has been well studied, not so much attention has been paid to slow-time variations especially with regards to local effects. In this work, we employed monthly means of cosmic ray count rates from two mid latitude (Hermanus and Rome), and two higher latitude (Inuvik and Oulu) neutron monitors (NM), and compared their variability with geomagnetic stations that are in close proximity to the NMs. The data spans 1966 to 2008 and covers four (4) solar cycles. The difference (ΔCR)between the mean count rate of all days and the mean of the five quietest days for each month was compared with the Dst-related disturbance (ΔH) derived from the nearby geomagnetic stations. Zeroth- and First- order correlation between the cosmic ray parameters and geomagnetic parameters was performed to ascertain statistical association and test for spurious association. The signature of convection driven disturbances at high latitude geomagnetic stations was evident during the declining phase of the solar cycles close to the solar minimum. The absence of this feature in the slow-time varying cosmic ray count rates in all stations, and especially in the mid latitude geomagnetic stations suggest that the local geomagnetic disturbance contributes much less in modulating the cosmic ray flux.
IMPACT ASSESSMENT OF SPACE CLUB FUTA IN PROMOTING ASTRONOMY IN NIGERIA
Oniosun, Temidayo
Space Club,Federal University of Technology Akure organized the ?rst Asteroid Search Campaign in West Africa in collaboration with the International Astronomical Search Collaboration;a campaign that brought together participants from three Universities in Nigeria in a mission to discover unknown objects and reduce the risk of an asteroid impact using a special software called Astrometrica (this software provides the ability to easily compare astrometrical images for the purpose of moving object discovery).The Space Club is under the University Centre for Space Research and Application,registered under the African Regional Centre for Space Science and Technology Education in English.The club is the largest Space Club in West Africa with over 250 members and is made up of both undergraduate and postgraduate students (Mostly undergraduate) of the University with a common interest in Space Science and Technology.The purpose is to raise the next generation of Space Leaders.The club has several project groups including Astronomy,Cosmology,Satellite Meteorology,Space Engineering,Global Navigation Satellite System,Robotics etc.The Club has grown tremendously into becoming the pride of the University and a key ?gure in the Nigeria’s Space Sector.Over the years, the Club has collaborated with Space Organizations such as Space Generation Advisory Council, National Space Research and Development Agency,Universe Awareness,University Space Engineering Consortium,and recently,International Astronomical Search Collaboration in promoting Space Science and Astronomy in Nigeria.Since its launch,the club has been involved in several outreach programs to promote Astronomy among University students,High School students and little children.This paper focuses on evaluating the in?uence of the University Space Club in promoting space science and astronomy in Nigeria and explaining the mission of the club to all Space Enthusiast in a bid to seek for more partnership and collaboration.
WISDOM: Analysing the galaxy gravitational potential using molecular gas kinematics observed with ALMA
Onishi, Kyoko
Black holes are thought to play an essential role in galaxy evolution, leading to the various known correlations between the mass of the supermassive black hole (SMBH) and host galaxy properties (e.g. M-sigma relation, where sigma is the central stellar velocity dispersion). These correlations are however based on a relatively small number of measurements and a handful of methods, each with many limitations and selection biases. Given this situation, we started a mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project so to develop a SMBH mass measuring method using molecular gas kinematics. After some pilot studies, WISDOM Project I-IVmeasured SMBH masses in NGC 3665 (elliptical fast-rotator with a radio jet), NGC 4697 (elliptical fast-rotator with a low-luminosity AGN), NGC 4429 (lenticular with a low-luminosity AGN suggested), and NGC 5064 (spiral disc galaxy without an AGN), respectively. The project altogether profit from the growing power of the Atacama Large Millimeter/submillimeter Array (ALMA), that allows one to observe nearby galaxies at high enough spatial resolution to resolve the SMBH gravitational sphere of influence. WISDOM aim to expand the range of targets and thus shed more light onto the coevolutionary processes between galaxies and black holes. We will present the method to model the galaxy gravitational potential, and then discuss our results on the existing M-sigma relation. Our works altogether demonstrate the molecular measurement method is applicable to various galaxy types. The method thus open the possibility to drastically increase the number and most importantly the variety of galaxies with an accurate SMBH mass measurement.
The CSIRO Radiophysics 24.4-m Dover Heights ‘Hole-in-the-Ground’ Radio Telescope (1951?1954)
Orchiston, Wayne
THIS IS FOR THE HISTORIC RADIO ASTRONOMY WG MEETING ON 27 AUGUSTAUTHORS: WAYNE ORCHISTON, PETER ROBERTSON, HARRY WENDT & MARTIN GEORGEThe CSIRO Division of Radiophysics used a novel 72-ft (21.9-m) and later an 80-ft (24.4-m) transit ‘dish’ at Dover Heights field station in the eastern suburbs of Sydney from 1951 to 1954. In a bid to overcome the resolution problem then plaguing radio astronomy, in 1951 the Dover Heights team excavated a 72-ft diameter parabolic-shaped depression in the sand dunes at the field station, lined the surface with reflective metal strips, installed an antenna mast with a dipole and then used this transit instrument to detect 160 MHz galactic emission along the galactic plane—including the discrete source Sgr A. At the time, this was the largest parabolic dish in the world ‘constructed’ specifically for radio astronomy. The Dover Heights ‘hole-in-the-ground’ antenna was then enlarged to 80-ft diameter and in 1953 was used for a 400 MHz survey of accessible areas of the southern sky. This resulted in the detection of 14 discrete sources, along with a detailed contour plot of Sgr A which the Dover Heights group correctly identified as the Galactic nucleus. Finally, this novel antenna was used in 1954 to search unsuccessfully for the 327 MHz deuterium line. In just three short years this novel transit instrument allowed Australian radio astronomers to advance the cause of international radio astronomy with important results and a significant non-result.
The CSIRO Radiophysics Murraybank 6.4-m Parabola (1956?1961)
Orchiston, Wayne
THIS IS FOR THE HISTORIC RADIO ASTRONOMY WG MEETING ON 27 AUGUSTAUTHORS: HARRY WENDT, WAYNE ORCHISTON, PETER ROBERTSON & MARTIN GEORGEThe CSIRO Division of Radiophysics operated a fully steerable 21-ft (6.4-m) parabola at Murraybank field station in the northern suburbs of Sydney from 1956 to 1961. This radio telescope was built to test a new 48-channel H-line receiver prior to its installation at Parkes. A full southern sky H-line survey was conducted as well as observations of the Magellanic Clouds. The site also served as the test bed for a new digital recording system, which together with the 48-channel receiver, became the first H-line system installed on the 64-m Parkes Radio Telescope when it was commissioned in 1961.
The CSIRO Radiophysics Potts Hill 11-m Transit Parabola (1952?1963)
Orchiston, Wayne
FOR THE HISTORIC RADIO ASTRONOMY WG MEETING ON 27 AUGUSTAUTHORS: HARRY WENDT, WAYNE ORCHISTON, PETER ROBERTSON & MARTIN GEORGEThe CSIRO Division of Radiophysics operated a 36-ft (11-m) transit parabola at the Potts Hill field station in the western suburbs of Sydney from 1952 to 1963. This radio telescope was built following the H-line discovery for the purpose of a southern sky survey which was combined with Leiden observations to produce a full sky H-line survey of our Galaxy. The H-line survey used a 4-channel (40-kHz/channel) receiver. It was also used to produce the first neutral hydrogen maps of the Magellanic Clouds and to conduct a 600 MHz continuum survey of the southern sky, as well as serving as a test bed for an experimental maser receiver prior to the commissioning of the 64-m Parkes Radio Telescope.
The CSIRO Radiophysics 60-ft ‘Kennedy Dish’ (1959?1969)
Orchiston, Wayne
FOR THE HISTORIC RADIO ASTRONOMY WG MEETING ON 27 AUGUSTAUTHORS: WAYNE ORCHISTON, MARTIN GEORGE, HARRY WENDT & PETER ROBERTSONThe CSIRO Division of Radiophysics used the 60-ft (18.2-m) ‘Kennedy Dish’ at Fleurs field station in the far western suburbs of Sydney from 1960 to 1962 and subsequently at Parkes in central New South Wales. This fully-steerable altazimuth-mounted prefabricated American antenna was installed at the eastern end of the EW arm of the Chris Cross at Fleurs in November 1960. During 1961 and 1962 it was used in conjunction with the E-W arm of the Cross as the Fleurs Compound Interferometer to investigate the positions and angular sizes of eight known discrete sources at 1423 MHz. It also was used as a stand-alone dish to survey the southern sky at 1440 MHz. In 1963 the Kennedy Dish was relocated to Parkes and used as a variable baseline interferometer with the 64-m Parkes Radio Telescope. Undoubtedly the most notable astronomer to use this facility was Ron Ekers, for some of his Ph.D. research on source sizes and brightness distributions. In addition, other radio astronomers used the Parkes Variable Baseline Interferometer for H-line work and for OH observations. We feel that the pioneering role that the Kennedy Dish played in Australian astronomy has not been fully recognized.
The CSIRO Radiophysics 4.9-m × 5.5-m ex-WWII Experimental Radar Antenna (1947?1959)
Orchiston, Wayne
FOR THE HISTORIC RADIO ASTRONOMY WG MEETING ON 27 AUGUSTAUTHORS: WAYNE ORCHISTON, HARRY WENDT, PETER ROBERTSON & MARTIN GEORGEThe CSIRO Division of Radiophysics used a 14-ft × 18-ft (4.9-m × 5.5-m) WWII experimental radar antenna to conduct radio astronomical research at the Georges Heights and later Potts Hill field stations in Sydney from 1947 to 1959. Initially this novel radio telescope was used to record solar radio emission at 200, 600 and 1200 MHz from Georges Heights, but after transferring to Potts Hill in 1948 it was used to observe the partial solar eclipses of 1948 and 1949 and as part of a multi-wavelength solar monitoring project. Then from 1949 to 1951 it was employed for a 1210 MHz all-sky survey that resulted in the discovery of Sgr A, the strong discrete source later shown to be at the centre of our Galaxy. When Ewen and Purcell announced the detection of the 1420 MHz H-line in 1951 it was the ex-Georges Heights radar antenna that was used for confirmatory observations, and then to conduct the first survey of the distribution of neutral hydrogen in the southern sky. Finally, this historic antenna was used at 1423 MHz to observe the partial solar eclipse of 8 April 1959, in conjunction with the Chris Cross at Fleurs field station. For more than a decade this radar antenna made important and wide-ranging contributions to international radio astronomy.
Nucleated dwarf galaxy population in the Fornax galaxy cluster
Ordenes, Yasna
We present the analysis of the nucleated dwarf galaxy population in the central regions (= 350 kpc) of the Fornax galaxy cluster. The galaxies and their nuclei are studied as part of the Next Generation Fornax Survey (NGFS) using optical imaging obtained with the DECam mounted at Blanco/CTIO and near-infrared data obtained with VIRCam at VISTA/ESO. We decompose the nucleated dwarfs in nucleus and spheroid, after subtracting the surface brightness profile of the spheroid component and studying the nucleus using PSF photometry. In general, nuclei are found in a narrow color range, consistent with colors of confirmed metal-poor globular clusters (GCs), and with significantly smaller dispersion than other confirmed compact stellar systems (CSSs) in Fornax. We find nucleus masses in the range 4.8=log(M/Msun)=7.3 and detect a bimodal distribution with peaks located at log(M/Msun)~5.4 and ~6.3. We show that the two nucleus-mass sub-populations have different stellar population properties, where the more massive nuclei are older than ~2Gyr and have metal-poor stellar populations (Z=0.02Zsun), while the less massive nuclei are younger than ~2Gyr with higher metallicities in the range 0.02<z zsun="1." we="" find="" that="" the="" nucleus="" mass="" (m_nuc)="" vs.="" galaxy="" (m_gal)="" relation="" becomes="" shallower="" for="" less="" massive="" galaxies="" starting="" around="" 108="" msun.="" consequently,="" ratio="" ?="" (m_nuc="" m_gal)="" shows="" a="" clear="" anti-correlation="" with="" m_gal.="" ?-m_gal="" correlation="" exhibits="" two="" different="" regimes;="" both="" regimes="" reach="" maximum="" ?~10%="" at="" lowest="" and="" highest="" masses.="" test="" current="" theoretical="" models="" of="" nuclear="" cluster="" formation="" they="" cannot="" reproduce="" these="" observed="" trends.="" however,="" likely="" mixture="" in-situ="" star="" star-cluster="" mergers="" seems="" to="" be="" acting="" during="" growth="" over="" cosmic="" time.<="" p="">
</z></z></z></z></z></z>
An episodic maser jet in the water fountain IRAS 18113-2503
Orosz, Gabor
Planetary nebulae often express beautiful, multipolar, point symmetric shapes - while their progenitors are characterised as having spherical layered structures. As stars exhaust their nuclear fuel and depart from the AGB, they launch powerful jets that are believed to be responsible for creating the diverse shapes of PNe. Spectacular examples of collimated jets are those traced by water masers, in objects named "water fountains" (with jet speeds and sizes on the order of 100 km/s and 1000 AU respectively). Water fountains are very rare due to their short timescales (on the order of 100 years) and as such the launching mechanism of their collimated jets remains an unresolved puzzle. In our talk, we introduce the VLBI maser astrometric results of IRAS 18113-2503, a water fountain with multiple bipolar bow shocks in its high-velocity collimated outflow. Using our VLBA and VERA measurements, we unveil the spatial/kinematic structure and trigonometric distance (>10 kpc) of the bipolar bow shocks. We argue that the measured 3D maser velocities (>200 km/s) clearly show that the jets are formed in very short-lived, episodic outbursts on a decadal timescale, and that they decelerate in a non-linear way. Using a simple kinematic model, we use our astrometric results to derive the physical properties of the jet, its source and surroundings, and argue that the most reasonable driving mechanism is a binary system.
LOFAR MSSS: Diffuse radio emission in clusters of galaxies
Orru, Emanuela
The existence of mega-parsec scale intra-cluster magnetic fields is proved by the presence of diffuse radio sources detected at the centre (radio halos) or periphery (radio relics) of clusters of galaxies. Current statistical studies of radio halos are based few tens of objects on samples limited in redshift and cluster mass. Radio halos are statistically found in about one third of massive clusters (Cassano2006), while these are statistically rare in less massive clusters (Cuciti2015, Bernardi2016). Moreover an handful of giant radio halos have been found in non merging cluster (Bonafede2014, Sommer2017). A sub-class of radio halos with very steep spectrum, the ultra-steep spectrum radio halos (hussRH, BrunettiussRH2008) expected to be bright only at low frequencies. In particular low frequency observations are the best tool to detect and study ussRH in low mass (M_{500} < 5 * 10^{14} M_Sun) galaxy clusters.The LOFAR Multifrequency Snapshot Sky Survey (MSSS) (Heald et al. 2015) is the first all northern sky survey performed with LOFAR. MSSS data were used to perform a pilot study aimed at expanding the statistics, investigating the detection rate of the survey of diffuse radio emission in clusters of galaxies and characterising their spectral behaviour at 150 MHz. The sample probes two orders of magnitude in X-ray luminosity, radio power, red-shift and one order of magnitude in cluster mass and temperature. In this talk I will discuss about the analysis of the newly discovered ultra steep diffuse radio emission in the cluster A1185 (z=0.0336).
Night sky brightness at Kottamia observatory site using DMSP satellite images
Osman, Ahmed
We have calculated the artificial sky brightness in V photometric band at Kottamia observatory site in Egypt, using The Defense Metrological Satellite Program (DMSP) images. For the first time Garstang's model has been applied to DMSP images to calculate the artificial sky brightness over the entire sky at a specific site. The results have been compared with photoelectric ground based observations (GBO) carried out by Osman (1996). It is found that after adding corrections due to the atmospheric ozone and thin dust layer above the polluting cities and below the observatory, there is a good agreement between our predictions based DMSP data and the GBO.
A Search for Binaries in the Kepler K2 Fields Using the Pulsation Timing Method
Otani, Tomomi
Finding orbital solutions of binaries which have small mass ratios (<0.4) and long periods (>50 days) is challenging using traditional techniques. For example, the radial velocity method is a common way to detect binary stars, however it requires large telescopes and is challenging for long period systems. For binaries in this regime with at least one component that pulsates, pulsation timing is a better approach. Orbital solutions for such systems can be obtained from the periodic change in pulse arrival times as the star’s reflex motion is manifested by the changing light travel time along the line of sight. We present early results of a search for binaries containing delta Scuti variables in the Kepler K2 extended mission fields. We used the K2 long-cadence (sampling time = 29.45-min) light curves, which are suitable to detect pulsation periods of a few hours as in delta Scuti stars. The Kepler K2 mission observations span about 80 days. Binary candidates which show evidence of periods longer than the K2 temporal window can be observed using space telescopes like TESS and ground-based 1-m size telescopes.
SWAG: Distribution and Kinematics of an Obscured AGB Population toward the Galactic Center
Ott, Juergen
Outflows from AGB stars enrich the Galactic environment with metals and inject mechanical energy into the ISM. Radio spectroscopy can recover both properties through observations of molecular lines. We present results from SWAG: "Survey of Water and Ammonia in the Galactic Center". The survey covers the entire Central Molecular Zone (CMZ), the inner 3.35x0.9deg (~480x130pc) of the Milky Way that contains ~5x10^7 Mo of molecular gas. Although our survey primarily targets the CMZ, we observe across the entire sightline through the Milky Way, covering the full radial profile of the Galaxy's AGB population. AGB stars are revealed by their signature of double peaked 22GHz water maser lines. They are distinguished by their spectral signatures and their luminosities, which reach up to 10^-7 Lo. Higher luminosities are usually associated with Young Stellar Objects located in CMZ star forming regions. We detect a population of ~600 new water masers that can be associated with AGB outflows. That corresponds to a density of ~200/deg^2, with a Galactic Latitude and Longitude density gradient. Our survey allows us to study the distribution and energetics of the AGB population as well as correlations with additional ~42 thermal molecular lines that we observe in SWAG.
Roche lobe filling red giants in symbiotic novae
Otulakowska-Hypka, Magdalena
Symbiotic stars are interesting for many reasons. There are still poorly understood when it comes to the impact of binarity on their evolution, there is also no consensus in terms of their mass transfer mode (RLOF or stellar wind). The most interesting is probably the fact that their observed masses suggest that they are promising candidates for SN Ia progenitors in both: the single and the double degenerate scenarios. With the use of optical interferometry we measure radii of red giants in well-chosen symbiotic novae. Such precise geometry of the giants in symbiotic S-type systems is crucial and conclusive from a binaries' evolution perspective and also to understand their potential as SN Ia progenitors in any scenario.
Review of V1128 Tau Light Curves between 2004-2016
ÖZEREN, Ferhat Fikri
V1128 Tau is a well-known binary system discovered by HIP-PARCOS satellite. It was classified as a B Lyra-type eclipsing binary with 0.3053732 days orbital period, and G0 spectral type, and 9m.64 in V band.It has visual tenth magnitude G7 companion, BD+12 511B, separated by 14” which is considered as a physical pair and a triple system.In this study, we gathered all related observational data of V1128 Tau and we included our own observations and give the light curve analysis and review of it.
The star-formation and ionisation properties of low-mass galaxies out to z=1 from ultra-deep MUSE spectroscopy
Paalvast, Mieke
The MUSE instrument on the VLT provides an entirely new way to study the population of, especially dwarf, emission-line galaxies. Here we present results from ~310 hours of GTO observations, spread over ~52 arcmin^2 of the low-mass galaxy population (6<log m*="" msun<9)="" out="" to="" z="1." we="" use="" these="" data="" study="" the="" low-mass="" end="" of="" sfr-m*="" relation="" down="" log="" sfr="" ~="" -3,="" and="" its="" evolution="" with="" redshift,="" sfrs="" determined="" from="" balmer="" lines,="" highlight="" importance="" selection="" function="" on="" inferred="" relation.="" our="" slope="" is="" shallower="" than="" most="" simulations="" semi-analytical="" models="" predict,="" which="" implies="" that="" feedback="" processes="" in="" systems="" affect="" star="" formation="" or="" accretion="" gas="" onto="" galaxies="" are="" more="" important="" expected.furthermore="" ionisation="" properties="" plane.="" particular="" explore="" [o="" iii]="" ii]="" (o32)="" ratio="" has="" been="" argued="" be="" elevated="" non-zero="" escape="" ionising="" radiation.="" discuss="" relationship="" between="" o32="" galaxy="" show="" not="" correlated="" sfr.="" find="" fraction="" extreme="" oxygen="" ratios="" (o32="" >4)="" constant="" implying="" amount="" photon="" over="" cosmic="" time.the="" content="" this="" presentation="" described="" paalvast,="" m.="" (4th="" year="" phd="" student="" at="" leiden="" observatory), ="" verhamme,="" a.,="" straka,="" l.a.,="" brinchmann,="" j.="" et="" al="" (submitted="" a&a) and="" boogaard,="" j.,="" bouche,="" n.,="" (in="" prep). <="" log><="" p=""> </log></log></log></log></log>
Metallicity calibrations of low star-forming dwarf galaxies: the influence of a stochastic IMF
Paalvast, Mieke
We present a study of the consequences of an initial mass function (IMF) that is stochastically sampled on the main emission lines used for gas-phase metallicity estimates in low star-forming dwarf galaxies. We use the stochastic stellar population code SLUG and the photoionisation code Cloudy to show that the stochastic sampling of the massive end of the mass function can lead to clear variations in the relative production of energetic emission lines such as [OIII] relative to that of Balmer lines. We use this to study the impact on gas-phase metallicity calibrators such as the electron temperature method and the N2O2, R23 and O3N2 strong-line methods. We find that the stochastic sampling of the IMF leads to a systematic over-estimate of O/H in galaxies with low star formation rate ($\le 10^{-3}$ \Msun /yr$^{-1}$) when using all different methods. We point out that while the SFR(Ha)-to-SFR(UV) ratio can be used to identify systems where the initial mass function might be insufficiently sampled, it does not provide enough information to fully correct the metallicity calibrations at low star formation rates. Care must therefore be given in the choice of metallicity indicators in such systems, with the N2O2 indicator proving most robust of those tested by us.The content of this presentation is described in Paalvast, M. & Brinchnmann, J., 2017, MNRAS, 470, 1612
ALMA polarization studies of Nearby galaxies
Paladino, Rosita
Magnetic fields are an essential ingredient of star formation in galaxies, at various spatial scales.They affect directly the mean gas density, which impacts significantly the star formation rate, but they also regulate the collapse and fragmentation of molecular clouds.Nearby galaxies offer the unique opportunity to study magnetic fields in different environments on large scales, while still being close enough to allow detailed studies of small scale structures.The large scale magnetic fields in galaxies are investigated through observations of synchrotron polarized emission. On giant molecular clouds scales, so far only in the Milky Way, dust polarization measurements have been obtained. Relating these different tracers at different scales is fundamental to clearly understand the role of magnetic fields.With current data for the Milky Way, it is difficult to reconcile magnetic field models with both synchrotron and dust polarization observed. More sophysticated models are needed, and observational constraints on the observed dust polarization in different location of nearby galaxies are crucial.ALMA, with its incomparable combination of resolution and sensitivity, offers a new tool to observe dust continuum at giant molecular clouds scales in nearby galaxies and detect its polarization.With these unprecedented observations it will be possible to combine dust polarization and synchrotron information to build a coherent picture of magnetic fields in galactic interstellar medium.
ALMA polarization studies of Nearby galaxies
Paladino, Rosita
Magnetic fields are an essential ingredient of star formation in galaxies, at various spatial scales.They affect directly the mean gas density, which impacts significantly the star formation rate, but they also regulate the collapse and fragmentation of molecular clouds.Nearby galaxies offer the unique opportunity to study magnetic fields in different environments on large scales, while still being close enough to allow detailed studies of small scale structures.The large scale magnetic fields in galaxies are investigated through observations of synchrotron polarized emission. On giant molecular clouds scales, so far only in the Milky Way, dust polarization measurements have been obtained. Relating these different tracers at different scales is fundamentalto clearly understand the role of magnetic fields.With current data for the Milky Way, it is difficult to reconcile magnetic field models with both synchrotron and dust polarization observed. More sophysticated models are needed, and observational constraints on the observed dust polarization in different location of nearby galaxies are crucial.ALMA, with its incomparable combination of resolution and sensitivity, offers a new tool to observe dust continuum at GMC scales in nearby galaxies and detect its polarization.With these unprecedented observations it will be possible to combine dust polarization and synchrotron information to build a coherent picture of magnetic fields in galactic interstellar medium.
Studying the large-amplitude optical variabilty of V648 Car
Palma, Tali
Since 2012 we have been conducting, at the Swope telescope of the Las Campanas Observatory in Chile, an observing campaign aimed at searching for rapid photometric variability (i.e., flickering) in different types of accreting binary stars. V648 Car was recognize as a priority target among symbiotic stars - binaries composed of a hot compact star and a late-type giant - due to its supposedly high-mass WD and its hard X-ray emitting nature. After the first serendipitous discovery of V648 as a high-amplitude flickerer (Angeloni et al. 2012), a large amount of photometric data have been collected over the years with the aim of studying possible periodicities and thus further characterize the nature of the accreting component and of the binary system as a whole. In this work we present the preliminary results of this ongoing investigation.
Triggered Formation of Star Clusters
Palous, Jan
Gould's belt with its star forming regions and OB associations, and the galactic supershell GS242-03+37 with associated young stars clusters, serve as examples of the triggered star formation due to the gas density increase in walls of expanding shells. We shall discuss how frequently similar events may happen in the differentially rotating disks of spiral galaxies and what role the supernovae play in this scenario. Interior volume of the expanding shell contains the interstellar medium enriched with the yields of the evolution of the parent stars. This medium mixes with the gas collected in the shell walls where the new clusters form.
Star Clusters Triggered by GS242-03+37
Palouš, Jan
We explore the star clusters found in walls of the Milky Way supershell GS242-03+37. We argue that the observed HI distribution can be explained as an expanding structure more than 100 Myr old powered by a modest energy released by an OB association. The formation of star clusters has been triggered less than 40 Myr ago when the ISM density increased due to the galactic differential rotation and vertical oscillations in the galactic disk. The sequence of ages of star clusters connected to the wall of GS242-03+37 will be compared to progression of star formation observed in the solar vicinity and in the spiral arms of the Milky Way.
STUDY OF X-RAY EMISSION CHARACTERISTICS In SOLAR FLARES employing SOXS: CZT detector
PANDYA, UMANGKUMAR
My project involves a unique sample of 11 solar flare events observed by the space mission “Solar X-ray Spectrometer (SOXS)” particularly by CZT detector. I study temporal characteristics of 11 flares in general and rise time characteristics in particular. For this purpose I got an opportunity to learn newly developed software in IDL. The flares selection is based on the GOES intensity in the range of M1.0-X1.0. The catalogue of all the flares chosen for this work is presented in table. The rise time of flares vary between 123 and 433 secs in 4-5.5 keV energy band while shortest rise time of the order of ~60 secs has been observed in 20-56 keV high energy bands. I have discussed analysis methodology and results in Table. My results reveal unique feature that rise time decays exponentially towards high energy. This result suggests that short rise time at high energy tail may be due to faster acceleration of electrons and thereby producing non-thermal bremesstrahlung via collisions of electrons with ambient plasma in solar flare loops.
The role of the magnetic field in a translucent molecular cloud
Panopoulou, Georgia
Translucent molecular clouds represent a vastly underexploredregime of cloud evolution in terms of the effect of the magnetic field. Theirpristine nature renders them ideal for investigating the initialproperties of the magnetic field, prior to the onset of star formation.Using starlight polarimetry, we map the plane-of-sky magnetic field orientationthroughout ~10 sq. degrees of the Polaris Flare translucent molecular cloud.We provide the first quantitative estimate of the magnetic field strength in thistype of system. By combining our measurements with the high-resolution Herscheldust emission map, we find a preferred alignment between filaments and theobserved magnetic field. Our results support the presence of a strong magneticfield in this system.
SAFARI: Direct Detection of Low-Mass Companions From Long Period Radial Velocity Trends
Pantoja, Blake
Radial velocity measurements have long proven to be a powerful method of detecting low-mass companions to bright stars, but they come with the inherent limitation that only minimum masses can be constrained for these companions, since the system inclinations are unknown. Direct imaging, on the other hand, allows us to constrain the companion's inclination relative to an Earth-bound observer, and when combined with radial velocities, allows us to directly probe into the mass/period parameter space of any detected companions. By searching for targets with long-period radial velocity trends, we are able to search for objects with a known but unseen companion. We will present our program for following up old metal-rich and giant stars with observed long period radial velocity trends with high-contrast direct imaging on SPHERE, MagAO, and SOAR. This project has shown to be successful for the detection of low-mass stars with non-detections representing possible planetary-mass companions. We will also show our methods for obtaining the highest possible contrast performance close to the primary star for extreme Adaptive Optics instruments, which will be crucial for directly detecting faint low-mass planets around old stars. This will also be crucial for future instrumentation on the E-ELT and WFIRST, when planetary detections will be achievable.
Argentina Uranometry and the constellation boundaries
Paolantonio, Santiago
The astronomical community accepts the division of the celestial sphere into 88 constellations, according to what was established by the IAU. In the first Assembly of 1922 the exclusive use of Latin names for constellations and their abbreviations was resolved with the three-letter system. In the following meeting, the Belgian National Committee of Astronomy examined the pending issue of the limits of the constellations, presenting a motion to review them. The astronomer Eugène Delporte had the responsibility for the complete theoretical demarcation, informed the rest of the members of the sub commission, and took their recommendations into account. In his work of 1930, Delporte took into account what was done half a century earlier in the famous work “Argentinean Uranometry”, published in 1877 and 1879. The reason for this action was the quality of the work done in the Cordoba Observatory and the detailed study carried out by its director, Benjamin Gould. One of the most important reasons for the need to clearly define constellation boundaries was the issue of variable star names. Again in this aspect the Argentine Uranometry had great importance, since 208 variable or suspicious stars were included, at that time the list did not exceed 150. In this work the structure known today as the Gould's belt was described for the first time. We present a detailed investigation of the current situation at that moment, when the constellation boundaries were proposed using arcs of RA circles and parallels of declination, choosing them in such a way that they did not deviate too much from those used in the most important celestial atlas of the time, and minimizing the changes of belonging of the stars to the constellations. The consideration of the Gould’s work, was the reason for the choice of the reference equinox 1875.0 for the coordinates, in order to form a set with the Uranometry, although by that time the positions referred to 1900.0 were already given.
The Argentinean attemps to prove the Theory of General Relativity: the total solar eclipses of 1912, 1914 and 1919.
Paolantonio, Santiago
The year 2019 marks a century of the first verification of one of the predictions of the Theory of General Relativity, on the occasion of the total solar eclipse of May 29, 1919. While this event has been widely documented by historians, much less has been written about the attempts made before it. Various pieces of documentation belonging to the collection of the Museum of the Astronomical Observatory of Córdoba, Argentina, have allowed to detail the circumstances that led to the expedition of the Argentine National Observatory to observe the eclipse of October 10, 1912 - visible in the southern area of Brazil. This expedition, under the direction of Dr. Charles D. Perrine, had among its purposes, the test of the new theory proposed by Albert Einstein. The origin of this initiative was in an express demand made by Erwin Freundlich, by letter and personally, to Perrine in order to confirm Einstein's theory. Two cameras were specially designed and built for this purpose in the workshop of the Observatory. The attempt to prove the new theory was frustrated by a storm that prevented observing the phenomenon. A second attempt was carried out in 1914, an opportunity for the organization of an expedition that was established in the Crimean peninsula facing the Black Sea, at the very beginning of the Great War. Again, the clouds hampered the studies. Despite the observation was once more planned, budgetary problems prevented the participation of the Argentine delegation for the eclipse of 1919, in which the Sun finally shined.In this presentation, we share a history of failures that could have meant to transcend for a successful observation at the right place and time. The storyline is (as today?) crossed by the need of continuity in scientific projects, to effort working towards any result. Yet, we plan to celebrate the centenary of the 1919 eclipse in Argentina, for a total solar eclipse will cross will cross all the territory on July 2nd of 2019.
Dwarf Galaxies of the NGC 2784 Galaxy Group Newly Discovered in KMTNet Supernova Program
Park, Hong Soo
We present the first study on the faint dwarf galaxies in nearby galaxy groups detected in the KMTNet Supernova Program. Our presentation shows the result of BVI surface photometry of 38 dwarf galaxy candidates discovered in deep stack images of ~30 square degrees centered on the NGC 2784 galaxy group. The detection limit in the surface brightness is about µV=28.5 mag/arcsec2 and the faintest central surface brightness is µ0,V= 26 mag/arcsec2. The dwarf candidates have absolute magnitudes brighter than MV = -9.5 mag and effective radii larger than 200 pc assuming they are at the distance of NGC 2784 (d~10 Mpc). Their radial number density decreases exponentially (or with power index, a=-1.3) with distance from the center of NGC 2784. Beyond radius of 0.5 Mpc, the density profile flattens and we estimate the background contamination is about 15%. The mean color, <(B-V)0>=0.7, and Sérsic structural parameters of the candidates are consistent with those parameters for the dwarf galaxies of other groups. We find that the central dwarf galaxies in the group are redder and brighter than the outer dwarfs. The faint-end slope, a=-1.33, of the luminosity function of the NGC 2784 group is consistent with results for other groups, but steeper than that of the Local Group. The KMTNet survey will provide homogeneous catalogs of dwarf galaxies in 15–20 groups.
Sensitivity of Saturn's orbit to a hypothetical distant planet
Park, Ryan
Several distant scattered Kuiper belt objects have similar perihelion geometries that might be aligned due to the influence of an unknown planet well outside the orbit of Neptune (Batygin & Brown, 2016 Astronomical J. 151:22). Such a planet, with a mass up to an order of magnitude larger than the Earth, would dynamically affect the rest of the solar system. Saturn, which is well observed from radio range and Very Long Baseline Interferometry (VLBI) observations of the Cassini spacecraft, provides an opportunity to look for these perturbations. An unknown large planet would be expected to affect the orbit of Saturn, but this effect might be partially absorbed in the estimation of parameters used to fit the planetary ephemerides. Ephemeris parameters include the planetary orbital elements, the mass of the Sun and the masses of asteroids that perturb the orbit of Mars. Earlier analysis of the Cassini data showed no non-Newtonian effect as suggested by the Modified Newtonian Dynamics theory. We present an updated Cassini data set, with the accuracy of ranges to Saturn improved through updated estimates of the Cassini spacecraft orbit, and an analysis of the largest possible perturbing distant planet mass consistent with the ranging.
Measurements of Twilight Sky Brightness in Korea
Park, Han-Earl
Twilight time is important for not only astronomical observations but also daily lives. Historically, three types of the time has been established according to the zenith distance of the Sun: civil, nautical, and astronomical twilight times when the zenith angles of the Sun are 96°, 102°, and 108°, respectively. We report on the measurements of the sky brightness during the twilight period, which was carried out at Daejeon (127° 22' E and 36° 24' N), Korea, from July 2015 to December 2017. A portable lux meter (T-10) is used for the measurement and its bundled software (T-A30) for data acquisition and pre-processing. In the analysis, we utilize the data of 179 days when the cloud coverage belongs between 0 and 2: 30, 56, and 93 days in 2015, 2016, and 2017, respectively. In this study, we will discuss the following topics: comparison of our measurements with known empirical equation for twilight sky brightness, difference of mean value of sky brightness in between the morning and evening twilight times, its seasonal variation, and relative amount of the illuminance on each twilight time to that on sunrise time. We believe that this study will provide a quantitative information on the sky brightness during the twilight time. In particular, the measurements on cloudless and moonless days will provide a standard for twilight sky brightness, at least at Daejeon of Korea.
Application of deep learning to the forecast of solar flare occurrence using solar magnetograms
Park, Eunsu
Convolutional neural networks (CNNs) are one of the well-known deep learning methods in the area of image processing and computer vision. In this study, we present the first application of convolutional neural networks to the forecast of solar flare occurrence. For this we consider three CNN models, two well-known pre-trained models, AlexNet and GoogLeNet, and one our proposed model. These models are optimized by changing several options such as the number of layers, activation function, and optimizer. Our inputs are SOHO/MDI(from May 1996 to Dec 2010) and SDO/HMI(from Jan 2011 to Jun 2017) magnetograms at 00:00 UT. Outputs are the ‘Yes or No’ of daily flare occurrence (C, M, and X classes). We train the models using the input and output data from 1996 to 2008, covering the entire solar cycle 23, and test them using the data sets from 2009 to 2017, covering almost the whole of solar cycle 24. Then we compare the results of the CNN models with those of conventional flare forecasting models in view of statistical scores such as Accuracy, Probability of Detection (POD), False Alarm Ratio (FAR), Critical Success Index (CSI), Heidke Skill Score (HSS), and True Skill Score (TSS). Our major results from this study are as follows. First, all of the CNN models have accuracy more than 0.80, and TSS values more than 0.55. Second, most of the models have CSI values more than 0.60, and POD value more than 0.80. Third, our model have better values for all of statistics scores than other two pre-trained models. Fourth, there are much improvements in FAR values compared to previous forecasting models. Our results indicate a sufficient possibility that deep learning methods can improve the capability of solar flare forecast as well as similar types of forecast problems. We discuss several possibilities to improve the models.
The Early Dynamical Evolution of Young Massive Clusters near the Galactic Centre
Park, So-Myoung
We examine the dynamical evolution of both Plummer sphere and substructured (fractal) star forming regions in Galactic Centre (GC) strong tidal fields to see what initial conditions could give rise to an Arches-like massive star cluster by ~ 2 Myr. We find that any initial distribution has to be contained within its initial tidal radius to survive, which sets a lower limit of the initial density of the Arches of ~ 600 M pc-3 if the Arches is at 30 pc from the GC, or ~ 200 M pc-3 if the Arches is at 100 pc from the GC. Plummer spheres that survive change little other than to dynamically mass segregate, but initially fractal distributions rapidly erase substructure, dynamically mass segregate and by 2 Myr look extremely similar to initial Plummer spheres, therefore it is almost impossible to determine the initial conditions of clusters in strong tidal fields.
The Historical Astronomy Division of the American Astronomical Society
Pasachoff, Jay
We report on the activities of the Historical Astronomy Division of the American Astronomical Society. We meet regularly together with the main January meeting of the American Astronomical Society (most recently in 2018 at National Harbor, Maryland) and occasionally with the Divisions (Solar Physics; Planetary Sciences; High-Energy Astrophysics) or at the spring main meeting. We also have a semiannual newsletter, which contains news relevant to the history of astronomy and book reviews. We "exist for the purpose of advancing interest in topics relating to the historical nature of astronomy. By historical astronomy we include the history of astronomy; what has come to be known as archaeoastronomy; and the application of historical records to modern astrophysical problems." We award the Doggett Prize for career achievement and the Osterbrock Prize for a book. The vice-president supervises attaining the obituaries of deceased AAS members. See had.aas.org.
Strong evidence for a cored dark halo in the Fornax dwarf spheroidal galaxy
Pascale, Raffaele
A knowledge of the present-day dark-matter distribution and internal stellar kinematics of dwarf spheroidal galaxies (dSphs) is important, having implications for both models of galaxy formation and the nature of dark matter. I will present a novel dynamical modelling method of dSphs, based on analytic distribution functions (DFs) depending on the action integrals, which can describe axisymmetric and possibly rotating stellar systems. In particular I will show very recent results (Pascale, Posti, Nipoti & Binney 2018, https://arxiv.org/abs/1802.02606) obtained by applying this method to the Fornax dSph, considering two-component spherical models in which both the stars and the dark matter are described with Dfs. Fornax can safely be modelled as an isolated system, because environment effects due to the Milky Way tidal field have been proven to be negligible. The models are compared with state-of-the-art spectroscopic and photometric observations of Fornax, accounting for the foreground contamination from the Milky Way and exploiting the knowledge of the line-of-sight velocity distribution with a star-by-star analysis. In light of the core/cusp problem we tested both the hypothesis of cuspy and cored dark halos. The model that best fits the structural and kinematic properties of Fornax has a cored dark halo, with corerc ~ 1kpc ~ 1.7 Re, where Re is the effective radius. The stellar velocity distribution is isotropic almost over the full radial range covered by the spectroscopic data and slightly radially anisotropic in the outskirts of the stellar distribution. The dark-matter annihilation J-factor and decay D-factor are strongly constrained. This cored-halo model of Fornax is preferred, with high statistical significance, to both models with a Navarro, Frenk and White dark halo and simple mass-follows-light models.
The High-redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: The Spitzer Catalog
Paterno-Mahler, Rachel
We present 190 galaxy cluster candidates (most at high redshift) based on galaxy overdensity measurements in the Spitzer/IRAC imaging of the fields surrounding 646 bent, double-lobed radio sources drawn from the Clusters Occupied by Bent Radio AGN (COBRA) Survey. The COBRA sources were chosen as objects in the Very Large Array FIRST survey that lack optical counterparts in the Sloan Digital Sky Survey to a limit of m r = 22, making them likely to lie at high redshift. This is confirmed by our observations: the redshift distribution of COBRA sources with estimated redshifts peaks near z = 1 and extends out to z≈ 3. Cluster candidates were identified by comparing our target fields to a background field and searching for statistically significant (≥2σ ) excesses in the galaxy number counts surrounding the radio sources; 190 fields satisfy the ≥2σ limit. We find that 530 fields (82.0%) have a net positive excess of galaxies surrounding the radio source. Many of the fields with positive excesses but below the 2σ cutoff are likely to be galaxy groups. Forty-one COBRA sources are quasars with known spectroscopic redshifts, which may be tracers of some of the most distant clusters known.
JVLA imaging of Heavily obscured, Hyperluminous quasars
Patil, Pallavi
The active galactic nucleus (AGN) phenomenon, driven by accretion onto supermassive black holes, influences the formation and subsequent evolution of galaxies and their constituent stars, gas, and dust via radiative and mechanical energy transfer (termed AGN feedback) to the surrounding interstellar and intergalactic media. Dust obscured quasars are likely going through early stages of feedback due to recent triggering of AGN activity, thus they are ideal for studying such interactions. We present high-resolution JVLA imaging of 156 hyper-luminous and heavily obscured quasars found at redshifts from z ~ 0.4-3. These galaxies were selected to have extremely red MIR-optical colors in WISE and bright, compact radio emission in NVSS/FIRST. JVLA snapshot observations at 10GHz with sub-arcsecond-scale angular resolution revealed that 115 out of 156 sources are indeed compact, radio-loud, and have structures on scales = 2 kpc (at z~2). We performed a detailed analysis of the radio SEDs of our sample sources. A few sources have peaked radio spectra, and thus belong to the class of High Frequency Peakers (HFP), Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources. This suggests that the radio jets could be recently triggered and are clearing their way out of the dense ISM of the host. We discuss implications of this study for our understanding of the impact of young jets on the evolution of the host galaxy.
Red Supergiants as Chemical abundance Probes: The Local Group dwarf NGC6822
Patrick, Lee
Red Supergiant Stars (RSGs) are important probes of stellar and chemical evolution in star-forming environments. They represent the brightest near-IR stellar components of external galaxies and probe the most recent stellar population to provide robust, independent abundance estimates. The Local Group dwarf irregular galaxy, NGC6822, is a reasonably isolated galaxy with an interesting structure and turbulent history. Using RSGs as chemical abundance probes, we estimate metallicities in the central region of NGC6822, finding a suggestion of a metallicity gradient (in broad agreement with nebular tracers), however, this requires further study for confirmation. With intermediate resolution Multi-object spectroscopy (from e.g. KMOS, EMIR, MOSFIRE) combined with state-of-the-art stellar model atmospheres, we demonstrate how RSGs can be used to estimate stellar abundances in external galaxies and present an overview of recent efforts to estimate the Mass-Metallicity relation of galaxies, a key diagnostic of the chemical evolution of galaxies, using stellar tracers alone. In this context, we compare stellar and nebular abundance tracers and highlight the potential of this technique with the upcoming/current generation of ground- and space-based telescopes.
AGB stars of the Magellanic Clouds as seen within the Delta-a photometric system
Paunzen, Ernst
About four decades ago, the Delta-a photometric system was introduced in order to investigate the flux depression at 5200A, typically for chemically peculiar stars of the upper main sequence. The a-index samples the flux of the 5200A region by comparing the flux at the center with the adjacent regions. The final intrinsic peculiarity index Delta-a was defined as the difference between the individual a-values and the a-values of normal stars of the same colour (spectral type). Here we present, for the first time, a case study to detect and analyse AGB stars in the Magellanic Clouds. For this, we use synthetic spectra and our photometric survey of the Magellanic clouds within the a-index. We find that AGB stars can be easily detected on the basis of their Delta-a index in an efficient way. We discuss our findings for AGB-stars of different chemistries.
AGB stars of the Magellanic Clouds as seen within the Delta-a photometric system
Paunzen, Ernst
About four decades ago, the Delta-a photometric system was introducedin order to investigate the flux depression at 5200A, typically for chemicallypeculiar stars of the upper main sequence. The a-index samples the flux of the5200A region by comparing the flux at the center with the adjacent regions.The final intrinsic peculiarity index Delta-a was defined as the difference between theindividual a-values and the a-values of normal stars of the same colour (spectral type).Here we present, for the first time, a case study to detect and analyse AGBstars in the Magellanic Clouds. For this, we use synthetic spectra and ourphotometric survey of the Magellanic clouds within the a-index. We find thatAGB stars can be easily detected on the basis of their Delta-a index in anefficient way. We discuss our findings for AGB-stars of different chemistries.
The debris disc around 49 Ceti
Pawellek, Nicole
Dust grains in debris discs are important tracers of the planetesimal formation mechanisms and physical processes operating in these systems. Two main forces influencing the particle orbits are gravity and radiation pressure leading to typical appearances of debris belts including asymmetries. High angular resolution observations at near-infrared wavelengths can provide key constraints on the radial and azimuthal distribution of the small dust grains helping us to better understand where most of the dust particles are released upon collisions. In contrast to near-infrared data, sub-mm observations trace the larger parent bodies. Thus, we are able to get more information on the distribution of the dust grains by using both wavelength ranges for our analysis. Here, we present near-infrared and sub-mm radial profiles of the 49~Ceti debris disc and compare them to our theoretical model taking into account the stellar radiation pressure.
Stellar variability in the ASASSN and APOGEE surveys
Pawlak, Michal
The APOGEE project is a large spectroscopic survey covering over 260 000 sources. Most of this objects are also observed photometricly by the ASASSN survey, which provide an unique opportunity to study them photometricly and spectroscopicly at the same time. I would like to present the collection of about 2000 periodic variables stars identified in the cross-matched data of the two surveys. The combination of photometric and spectroscopic data allows for an very accurate parametrisation of each of the objects, including deriving accurate periods and magnitudes from ASASSN photometry as well as logg, Teff, Vsini from APOGEE spectra. Additional information can also be derived from recentlyreleased Gaia DR2.
Testing cosmology with the phase-space distribution of satellite galaxy systems
Pawlowski, Marcel
Both the Milky Way and the Andromeda galaxy are known to host highly flattened planes of satellite galaxies. These display coherent kinematics, which is consistent with many of their satellite galaxies co-orbiting along the structures. Comparisons to cosmological simulations revealed that these planes of satellite galaxies are in severe tension with expectations based on the ?CDM model. Other phase-space correlations that have been found to be (at the very least) puzzling include the accretion of satellite dwarf galaxies in pairs or groups, the apparent overabundance of backsplash galaxies around the Milky Way, and the lopsidedness of the Andromeda satellite galaxy system. Due to the intrinsic difficulty of observing faint satellite galaxies around more distant hosts, determining their 3D positions and measuring their kinematics, these correlations have thus far been predominantly studied in the Local Group. This lead some to dismiss the planes of satellite galaxies problem by arguing that the Local Group happens to be a statistical outlier in a ?CDM universe. I will discuss successes in expanding such studies to more distant host galaxies. This includes recent results on the kinematics of the satellite galaxy plane around Centaurus A, and the first comparison to ?CDM of the pronounced signal of lopsidedness that has been found in stacked satellite galaxy systems around host galaxy pairs in the SDSS survey. I will discuss how these satellite phase-space correlations compare to expectations based on ?CDM simulations, and whether there is evidence that the inclusion of baryonic processes in cosmological simulations can alleviate the existing tension.
Cooperation in the Asia Pacific region for processing data from the Square Kilometre Array
Pearce, Sarah
The first phase of the Square Kilometre Array (SKA) Observatory will include two telescopes: SKA1-Low to be built in Australia, and SKA1-Mid in South Africa. By the time the SKA is in steady state operations in the late 2020s it will generate a raw data rate close to 1 TB/s. After initial processing, the output data products to be disseminated to science teams are estimated to be 250-300 PB per year for the two arrays combined.The core construction funding for SKA1 does not include the distribution of data to users, nor computational facilities to enable users to undertake further data analysis, both of which are necessary if the SKA is to deliver on its scientific promise. As with several other large-scale scientific instruments, these functions will be provided from regional funding rather than from project funds. The SKA Board has agreed on a model for SKA Regional Centres (SRCs), which would see SKA members establish and fund centres to provide computer support for the astronomers in their country or region.Australia has built two SKA pathfinders - ASKAP and MWA. Significant effort and investment has already been made that paves the way to the future Australian SRC, including close to 20 PB produced by MWA and ASKAP, and stored in the Pawsey Supercomputing Centre. An Australian collaboration is currently developing a roadmap towards the SRC, starting with tools needed for the precursors and building towards full SKA operations.In particular, Australia is exploring opportunities to expand the Australian SRC activities to include collaboration with similar developments in China, New Zealand and the broader Asia-Pacific Region. The International Centre for Radio Astronomy Research, CSIRO and the Shanghai Astronomical Observatory have initiated the ERIDANUS Project (Exascale Research Infrastructure for Data in Asian-Pacific astroNomy Using the SKA). This effort will form part of the collective work in the Asian-Pacific Region to establish SKA Regional Centres.
Protecting radio quiet at the Murchison Radio-astronomy Observatory
Pearce, Sarah
Australia’s site for the SKA is the 3,600km2 Murchison Radio-astronomy Observatory (MRO), in the Mid West region of Western Australia. More than 300km northeast of the nearest city, Geraldton, the MRO was selected for its low population density, excellent sky coverage, ionospheric stability and good tropospheric conditions. It currently hosts the Australian SKA Pathfinder (ASKAP), the Murchison Widefield Array (MWA) and the Experiment to Detect the Global Epoch of Reionisation Signature (EDGES).The low population density of the Mid West means that radio interference is much lower than in populated regions. In order to maintain this into the future and keep harmful interference to a minimum, the Australian and Western Australian (WA) Governments established the Australian Radio Quiet Zone WAThe radio quiet zone is protected by legislation, regulation and policy. There are concentric zones with different levels of protection, centred on the MRO:70km radius Inner Zone: other radiocommunications services within this zone are secondary to radio astronomy. Mining activities and the use of consumer-grade devices are also restricted within this zone.Coordination zones of 100 km to 260 km radius (depending on frequency) where licenced radiocommunications are coordinated with radio astronomy.Under the regulations, anyone who applies for a radiocommunications licence within the coordination zones must consult with the Site Entity (CSIRO). CSIRO then advises the regulator on any likely impact to radio astronomy at the MRO.This paper will examine the practical aspects of protecting radio quiet at the MRO and lessons learned during early years of operation. This includes managing radio emissions from the experiments and operations on the MRO itself through submission and assessment of Radio Emissions Management Plans. Ongoing protection of radio quiet is a high priority for CSIRO in its management of the MRO site.
Spheroid-dominated galaxies in a LCDM universe
Pedrosa, Susana
The goal of our work is to understand the formation and evolution of early-type, spheroid-dominated galaxies by means of cosmological simulations.For that purpose, we analyse the main structural, dynamical, and stellar population properties and assembly histories of this kind of galaxies and compare our results with observational data. In a recent paper, we studied field spheroid-dominated galaxies selected from a numerical $\Lambda$-CDM simulation. We analysed a sample of 18 low-intermediate mass field galaxies and achieved results that are in good agreement with observations as regards size, Sersic-law, Faber-Jackson relation, Fundamental Plane and Tully-Fisher relation. All of them have a non-neglectable disc component. It is remarkable that none of the relations mentioned above were tuned to be reproduced. However, the simulated galaxies are bluer and with higher star formation rates than the observed ones. Furthermore, the archaeological mass growth histories show later stellar formation and more prominent inside-out growth. In spite of this, they are consistent in average with observations in the sense that our galaxies also follow a downsizing trend. We concluded that the existence of a extended disc in the simulated galaxies causes this tension between simulation and observation and therefore, the need of more efficient quenching mechanisms is evident. SNe feedback seems to be necessary whereas AGN feedback is not expected to common in low-intermediate mass galaxies (our simulation does not include this effect). In consequence, we find Horizon-AGN and Horizon-noAGN simulations extremely useful to determine the role AGN effect in spheroid-dominated galaxies. We also extend all this analysis to galaxies from EAGLE simulation. In both cases, the simulated box is much bigger and therefore a very larger sample of galaxies can be obtained leading to significative statistics.
Relativistic beaming effect and radio dominance of Fermi sources.
Pei, Zhi-Yuan
Active Galactic Nuclei are very interesting and attractive objects for researching in extragalactic sources. A small subset of the radio loud AGNs is called blazars, which display extreme observational properties, such as showing ?-ray radiation, rapid variability, high luminosity, high and variable polarization, and superluminal motion. All of those observational properties are probably due to a relativistic beaming effect with the jet pointing close to the line of sight. Blazars also have two subclasses, namely BL Lac and FSRQ. Observations suggest that the orientation can be expressed by a core-dominance parameter R, which defined asR = Score/Sext. ,where Score and Sext. stands for the emission in the core Sext.component and extended component, respectively. The R, to some extent, is associated with the beaming effect. After the launch of Fermi Large Area Telescope(Fermi LAT), many sources have been detected to show high energetic ?-ray emission. In the latest catalogue(3FGL), 1444 sources are added by the former ones, and now are up to over 3000 sources, in which around 60% are AGNs, and 98% are Fermi blazars. Those data has give us a good opportunity to study the high energy astrophysics and beaming effect. In this work, we collected relevant observations from the literature for a sample of 2013 AGNs including 240 Fermi-detected sources and 1173 non- Fermi-detected sources. We found that the mean value of core dominance parameter for Fermi sources is higher than the case for non- Fermi sources, however, in contrary, the mean value of radio spectral index for Fermi sources is lower than the case for non-Fermi sources. A sequence is shown that: BL Lac > quasar > Seyfert > galaxy > FR type galaxy. For both ?-ray spectral index and variability index, quasar is higher than BL Lac. Meanwhile, We found that the core-dominance parameter-spectral index correlation exists for a large sample presented in this work, which may come from a relativistic beaming effect.
Milky Way abundance gradient: from HII regions and from chemical evolution models
Peimbert, Antonio
We present 2 determinations of the abundance gradient of the Milky Way based on HII regions: the first one derived from the conventional Direct Method (DM-gradient); and the second one from a combination of Recombination Lines and from Colisionally Excited Lines corrected for an implicit Abundance Discrepancy Factor (ADF-gradient). We compare these gradients with abundance gradients determined from B stars (B-gradient) and from Cepheids (C-gradient); we find that the ADF-gradient is consistent the B- and C-gradients while the DM-gradient is not. All these gradients show a flattening at intermediate radii (6 to 10 kpc) when compared with large radii (10 to 18 kpc), but there is a discrepancy at smaller radii (3 to 6 kpc): B stars suggest the flattening continues to the inner Galaxy, while Cepheids suggest the gradient steepens again. We present 3 chemical evolution models of the Galaxy, 1 that reproduces the DM-gradient, and 2 more that reproduce the ADF-gradient (one with a flat inner galaxy and the other with a steep inner galaxy); we find that the DM-gradient model is unable to reproduce the chemical abundance observed in the Sun, regardless of a possible solar migration; while the ADF-gradients are able to do so. Our results imply that one should use calibrations based on recombination lines when determining abundances in HII regions.
The relation between the O/H ratio and the total mass of the galaxies
Peimbert, Manuel
We compare different calibrations of the O/H abundance ratio measured from H II regions at the effective radius of galaxies of the CALIFA sample. Most calibrations are based on the collisional lines, ignore the ADF problem, ignore the results based on O recombination lines, and do not include the fraction of O atoms embedded in dust grains. Our calibration is consistent with the O recombination lines and present a mechanism that explains the cause of the ADF. This explanation is consistent will all the observational data for H II regions including the O recombination and the O collisional excited lines. The calibration is also consistent with the O/H values derived from Cepheids, B stars, the Sun and H II regions in our Galaxy (Carigi, Peimbert, and Peimbert 2018).
Science with the Fornax Deep Survey - a new complete census of 600 dwarf galaxies
Peletier, Reynier
28 years after Ferguson’s FCC, we have produced a new galaxy survey of the Fornax Cluster, covering a region of 26 square degrees. The survey in u’g’r’i’ is based on OmegaCAM images at the VST, at a depth comparable to the NGVS survey. Authors of this survey, the Fornax Deep Survey, based on GTO observations, are a an NL-led team (PI Peletier) and an Italian-led team (PI Iodice), of in total about 40 scientists. Our survey is being suppplemented by a variety of anciliary observations, including a K-band imaging survey, IFU observations of 50 dwarf galaxies and CO-observations taken with ALMA. HI observations are planned using the MeerKAT telescope.The scientific goals of the FDS project are diverse. We aim to study in detail the baryonic substructures, ranging from massive galaxies to small spheroidal galaxies and star clusters. The data have considerable legacy value, and will serve as a local reference for high redshift studies. The survey is ideal to study the influence of the galaxy environment on stellar populations. In particular, this allows us to study dwarf galaxies in unprecedented detail.In this presentation I will discuss the most important science results obtained up to now in the regime of dwarf galaxies, including:- A comprehensive magnitude and size-limited catalog of ~600 dwarf galaxies has been produced, of which colors and structural parameters have been obtained, leading to new insights in the formation and evolution of dwarf galaxies. These are discussed in the presentation of Aku Venhola.- A survey of Ultra Diffuse and other LSB galaxies in Fornax, clearly indicating a deficit of UDG/LSB galaxies in the center of the cluster (Venhola et al. 2017)- High spectral resolution SAMI IFU data for 50 galaxies, in an effort to obtain detailed spatially resolved kinematics and stellar populations for a complete sample of dwarfs, going fainter than anything currently available in the literature.
Abundance determinations in two H II regions in the dIrr galaxy Leo A
Pena, Miriam
In this work, we present chemical abundance determinations of two H II regions in the dIrr galaxy Leo A, from GTC OSIRIS long-slit spectra. Both regions, which are the brightest HII in this galaxy, seem to be ionized by stars later than O9 spectral type. In the first H II region, we were able to use the direct method, by measuring the electron temperature with the [O III] ??4363/5007 line ratio. For the low-ionized species, an electron temperature derived from the formula by Campbell et al. (1986, MNRAS, 223, 811) was used. Ionic abundances of O+2, O+, N+, and S+ were determined. O, N and S total abundances were calculated using literature ICFs for each element. Abundances by using strong-line methods were also determined, with similar results. For the second H II region, O and N abundances were calculated using strong-line methods. It is confirmed that Leo A in a very low metallicity galaxy, with 12+log O/H = 7.4, log N/O = –1.6, log S/O = –1.1.
Possible Implications for Discovery of Strong Radial Magnetic Field at the Galactic Center
Peng, Qiuhe
An abnormal strong radial magnetic field near the Galactic Center (GC) is detected at 2013 . The lower limit of the radial magnetic field at r=0.12 pc from the GC is B>8mG, which is quantitatively in agreement with the prediction of our paper “An AGN model with MM”(Peng & Chou, 2001, ApJL). Its possible scientific significances are following: 1)The black hole model at the GC is incorrect (Peng et al. 2016, ApSS). The reason is very simple as follows. The radiations observed from the region neighbor of the GC are hardly emitted by the gas of accretion disk which is prevented from approaching to the GC by the abnormally strong radial magnetic field; 2)This is an astronomical evidence for existence of magnetic monopoles(Peng et al. 2016, ApSS). 3) Magnetic monopoles may play a key role in some very important astrophysical problems using the Robakov-Callen effect that nucleons may decay catalyzed by MMs. Taking the RC effect as an energy source, we have proposed an unified model for various supernova explosion(Peng et al. 2017, ApSS) , including to solve the question of the energy source both in the Earth core and in the white dwarfs. 4) We may explain the physical reason of the Hot Big Bang of the Universe with the similar mechanism of supernova explosion by using the RC effect as an energy source.
DDO68-V1: an extremely metal-poor LBV in a void galaxy
Perepelitsyna, Julia
The lowest metallicity massive stars in the Local Universe with Z ~ (Zo/50-Zo/30) are the crucial objects to test the validity of assumptions in modern models of low-metallicity massive star evolution. These models, in turn, have major implications for our understanding of galaxy and massive star formation in the early epochs. The great progress in the area is expected with the next generation facilities like JWST and extremely large telescopes. One of the most interesting targets of this kind is the massive star DDO68-V1 in a nearby void galaxy DDO68. Discovered by us in 2008 in the HII region Knot No.3 with Z = Zo/35 [12+log(O/H)=7.14], DDO68-V1 was identified as a luminous blue variable star (LBV). We present here the LBV lightcurve in V and B bands, combining own new data and the archive and/or literature data on the light of Knot No.3 over the last 30 years. We find, in particular, that during the years 2008-2011 the LBV have experienced a very rare event of the giant eruption with the V-bavd amplitude of ~4 mag (V~24-20 mag).
Halo structural parameters of Low Surface Brightness galaxies
Pérez Montaño, Luis Enrique
Low surface brightness galaxies are disk galaxies intrinsically faint that are expected to form in fast- rotating haloes characterized by having high values of the spin parameter. In the present work we test this hypothesis by estimating the spin parameter distribution of a large sample of galaxies drawn from the SDSS-DR7, making use of HI mass and kinematic information from the ALFALFA survey catalog. The method used to estimate the spin parameter is an upgraded version of the one presented by Hernandez & Cervantes Sodi (2006), implementing different prescriptions for estimating the mass of the dark matter halos and including bulge+disc decompositions to estimate the specific angular momentum of the different baryonic components. Using a Tully-Fisher relation to infer the rotation velocity for the baryonic component, we obtain spin distributions for a volume-limited sample of LSB and HSB galaxies, as well as spin distributions of control samples with direct kinematic information to show that LSB galaxies present systematically higher values of spin than HSBs. If the spin distribution of both sub-samples is the same, HSBs need to lose angular momentum in order to reproduce the distribution of their observed structural properties.
Radial population gradients in cD galaxies
Pérez-Hernández, Ernesto
cD galaxies have two components, one has a light profile similar to the de Vaucouleurs law(n=4) while there is also a component from an extended luminous envelope. D and cD galaxies are usually brightest cluster members (BCM) and, while there are many ways of forming the extended luminous envelope, it is not clear why not all BCMs have one.We present a study of optical long-slit spectroscopy of 14 cD galaxies with 4 runs using the Boller & Chivens spectrograph at the 2.1 m San Pedro Mártir telescope and data for A2162 using the OSIRIS spectrograph at the 10.4 m GTC telescope respectively, to find gradients in age and metallicity, plus 2 runs of photometry with the 2.1m telescope looking for radial color gradients. Preliminary results of radial variations of spectral indices for 7 cD galaxies show mostly flat age gradients, in agreement with the photometry, while others present flat age and metallicity variations which appear as radial color gradients in the photometry. Preliminary results for A2162 from GTC include the measurement of spectral index variations between the center and radius 50”(~31.51 kpc), this could be due the existence of metallicity and/or age variations.
On the circumstellar effects on the Li and Ca abundances in massive Galactic AGB stars
Pérez-Mesa, Víctor
By considering the presence of a circumstellar envelope, we previously found strong circumstellar effects in the determination of the Rb abundances in massive AGB stars; these circumstellar effects, however, were found to be very weak for Zr. The abundances of lighter elements such as Li (and Ca) in massive AGB stars may be altered by the activation of hot bottom burning (HBB), which is expected to overproduce the 7Li (and 41Ca) isotope; e.g., the (super-)Li-rich character of massive AGB stars has been used as a HBB indicator in these stars. Here we explore the circumstellar effects on the Li and Ca abundances determination in massive AGB stars. By using our pseudo-dynamical models, we report new Li abundances in a complete sample of massive Galactic AGB stars, while their Ca abundances are reported for the first time. The circumstellar effects on the Li and Ca abundances are found to be very weak and the Li and Ca abundances derived with the pseudo-dynamical models are similar to those derived with the hydrostatical ones. The Li abundances thus confirm the (super-)Li-rich character of our sample stars and the HBB activation in massive Galactic AGB stars. Remarkably, massive Galactic AGB stars are found to be strongly underabundant in Ca (sometimes by up to 1-2 dex, with respect to the expected solar value). Possible explanations for this unexpected Ca underabundance in massive Galactic AGB stars are offered.
An interferometric quest to reveal the true nature of the core in the radio galaxy 3C 411
Perger, Krisztina
Examination of the X-ray spectrum of the classical double-lobed radio galaxy 3C 411 (PKS J2022+1001) resulted in two equally well-fitting models (Bostrom et al., 2014). One of the models was consistent with those known for radio galaxies, but the other one was a combination of two components: one similar to those found for Seyfert nuclei and another blazar-like, hard X-ray component. We investigated the parsec-scale radio structure of the galaxy core with sub-milliarcsec resolution very long baseline interferometry (VLBI) imaging, using archival Very Long Baseline Array (VLBA) data and new European VLBI Network (EVN) observations at multiple frequencies. The data do not confirm the presence of a blazar-like nucleus in the radio galaxy, and provide evidence for a change in the jet inclination angle with respect to the line of sight between pc and 100 kpc scales.
Methanol and carbon monoxide chemistry of protostellar envelopes
Perotti, Giulia
Carbon monoxide, CO, is a key molecule in the interstellar medium. It is the cornerstone for synthesizing complex molecules in the Universe, starting with methanol (CH3OH) and potentially leading to prebiotic molecules. To model the solid and gas-phase CO and CH3OH abundances in star-forming regions, we developed a Simplified CO Network (SCON). SCON can either be coupled to a 1D physical model of collapsing protostellar envelopes or a sophisticated 3D MHD simulation of a collapsing molecular cloud. The advantage of this simplified network is that it allows us to run these models for the ~104 trace particles of the simulations. In the cold outer parts of the envelope, most of the gas is frozen out onto dust grains. As matter falls toward the star, the temperature increases and these molecules sublimate. In the 1D model, the collapse is radial and all CH3OH sublimates into the gas phase. In the 3D simulation, results show that only a small fraction of gas reaches a high enough temperature for CH3OH to sublimate. Hence, the total amount of gas-phase CH3OH is lower in the 3D model compared to the 1D model. To benchmark the model predictions, we compare these to recently obtained observations of gas-phase CO and CH3OH from the SMA and APEX and ice CO and CH3OH from the VLT. Specifically, the data cover the envelope of the deeply embedded protostar Ser-SMM4 in the Serpens Main Cloud. The results of this benchmarking and the implications for the CO and CH3OH chemistry are presented.
Forming spiral galaxies in wet major mergers: The role of angular momentum in shaping the surface density profile
Peschken, Nicolas
In Athanassoula et al. (2016), we used high resolution N-body hydrodynamical simulations to model the major merger between two disc galaxies with a hot rotating gaseous halo each, and showed that the remnant is a spiral galaxy with realistic morphology and dynamics. The two discs are completly destroyed by the collision, but after the merger, accretion from the surrounding gaseous halo and the induced star formation allow the buiding of a new disc in the remnant galaxy.In Peschken et al. (2017), we used these simulations to examine the radial surface density profiles of the remnant galaxies, and their dependence on the galactic angular momentum. We focus on downbending disc profiles (type II), i.e. profiles composed of an inner and an outer exponential disc separated by a break, with the outer disc being steeper than the inner one. This particular type of profiles is observed in the majority of real spiral galaxies but can display very different values for the corresponding scalelengths, from 0.5 kpc to 10 kpc for the flatter profiles. We analyzed the effect of the total initial angular momentum on these values, and found that both the inner and the outer disc scalelengths, as well as the break radius, correlate with the total angular momentum of the initial merging system, and are larger for high angular momentum systems. To understand this result, we followed the angular momentum redistribution in our simulated galaxies, and find that, like the mass, the disc angular momentum is acquired via accretion, i.e. to the detriment of the gaseous halo. Furthermore, high angular momentum systems give more angular momentum to their discs, which affects directly their radial density profile. Adding simulations of isolated galaxies to our sample, we find that the correlations are valid also for disc galaxies evolved in isolation.
Stellar Spectra as a Laboratory Source for Identifying Levels of Neutral Iron
Peterson, Ruth
We report the significant progress we have made on Fe I line identification by using high-resolution, high-quality archival ultraviolet and optical spectra of a dozen warm and cool stars as the Fe I laboratory source. The warmer temperatures of these stars populate higher excitation levels than is possible with the laboratory furnace. We have now published the identifications and energies of 124 previously unknown Fe I levels by demanding an exact match of the positions of at least four Kurucz predicted lines of each unknown level to observed but unidentified stellar absorption features (Peterson & Kurucz 2015; Peterson, Kurucz, & Ayres 2017). We are continuing this work with new Hubble high-resolution spectra from HST GO-14161 and GO-15179, and anticipate adding solar and stellar infrared spectra as well. The resulting identification of hundreds more levels and their associated thousands of stellar lines will fill in line blends and flux gaps throughout the UV and IR, enabling accurate determinations of the abundances of exotic elements from high-resolution spectra, and the reliable theoretical modeling of moderate-resolution rest-UV fluxes of remote, red-and-dead galaxies at low to intermediate redshifts.
A high baryon fraction in galaxy haloes at z~3
Pezzulli, Gabriele
A possible reason why baryons appear to be missing from the immediate surroundings of present day galaxies is that they may have been expelled from (or prevented to accrete on) galaxy haloes by feedback processes at high redshift. Determining if and when this happened is key to understand the fate of baryons over cosmic time and requires a detailed census of warm and hot baryons in the CGM of galaxies at an early stage of their evolution.Thanks to the unprecedented capabilities of MUSE, it is now possible to directly map the CGM of z~3 galaxies in emission and to determine its spatial distribution over large scales, as well as its thermodynamic state and total mass. Based on MUSE observations and on theoretical modelling, I will show that moderately massive galaxy haloes at z~3 likely still retain a large fraction of their baryons within the virial radius. I will discuss potential implications for the missing baryons problem, as well as how residual uncertainties will be mitigated by future observations and modelling.
Dwarf galaxies: evidence of differential tidal effects in the Large Magellanic Cloud
Piatti, Andrés E.
We used DECam images to build for the first time stellar density and/or surface brightness radial profiles for almost all known ancient Large Magellanic Cloud (LMC) globular clusters (GCs). These are the most extended radial profiles built for these GCs so far. The studied GCs located farther than ~ 5 kpc from the LMC centre would not seem to present any hint of extended stellar structures, like the family of different features seen in an important number of Milky Way old GCs. The apparent negative detection of such outer region structural tracers could suggest that the LMC potential has not been efficient in stripping stars off its GCs. Those GCs located closer than ~ 5 kpc from the LMC centre show an excess of stars distributed in the outermost regions with respect to the nominal amount of stars predicted by the best-fitting empirical King models. Such an excess of stars tightly depends on the position of the GCs in the galaxy, in such a way that the closer the GC to the LMC centre, the larger the excess of stars. In addition, the GC radii also show a remarkable trend with the position of the GC in the LMC disc, namely: the farther the GC, the larger the GC radius. These outcomes can be fully interpreted in the light of the known GC radial velocity disc-like kinematics, from which GCs have been somehow mostly experiencing the influence of the LMC gravitational field at their respective mean distances from the LMC centre. The different dimensions of the analysed GCs do not seem to be related to any systematic difference in their masses. Despite this, GCs with deprojected distances smaller than ~ 5 kpc have lived for many more median relaxation times. This behaviour might also be a result of the stronger tidal fields, which have made the GCs dynamically evolved faster by bringing stars towards the outermost GC regions sooner than what would have been expected in an scenario of isolated two-body relaxation.
On the Nature of Spiral Arms in Disk Galaxies. I. Structure
Pichardo, Barbara
Through a comprehensive set of high resolution N-body simulations, employing different codes, we have explored in detail the structural characteristics of spiral arms produced in barred, non-barred and satellite-induced arms galaxies. In terms of their dynamical influence, some of the most important characteristics studied here are: the pitch angle, the density law along, transverse, and perpendicular to the spiral arms, their scale-length, and time-scale. In this first study, analyzing different spiral arms along the whole evolution of the simulations (5 \Gyr), we find that, although the spiral arms efficiently wind up, as previous work have reported, particularly those in barless simulations, the pitch angle reduces in best cases just a few (five to ten) degrees, before the arms fade away completely; this means that, even if spiral arms seem to behave as material arms some part of their lifes, this period is so short that their dynamical influence would be of small importance to the whole galactic evolution compared to the period where the arms keep strongest. On the other hand, new spiral arms are born continuously, as long as the dominating trigger (bar, satellite, etc.) and they seem to be the same every time, i.e., new born arms keep similar in their structural characteristics. In this set of papers, we are interested in understanding the effective dynamical influence of spiral arms as they evolve (born, grow and vanish) in simulations confronting the results when posible with available optical/IR observations of spiral galaxies.
Constraints of habitability for the young Earth in a highly eccentric orbit
Pilat-Lohinger, Elke
In the last twenty years, thousands of planets outside the Solar system have been discovered, with exoplanets in different environments. Of course we cannot expect to find an exoplanetary system fully resembling our Solar System. Therefore, we consider a Solar System type configuration where the young Earth moves in an eccentric orbit and approaches the Sun to distances closer than Mercury.We focus on the study of young Earth 1 billion years ago, when the Sun’s extreme UV (EUV) flux was about 5 times higher than the current radiation. In case of eccentric motion of the Earth, strong variations of the EUV flux would influence the evolution of the planet’s atmosphere because maximum values of the EUV radiation of about 50 times the current EUV flux would be possible.Taking into account a certain amount of Nitrogen in the atmosphere of such a young Earth, we study the non-thermal loss of N2 over a long time interval. We therefore want to investigate to what extent eccentric motion will influence the conditions of habitability of a terrestrial planet.
The PRIMitive Asteroids Spectroscopic Survey Library: PRIMASS-L
Pinilla-Alonso, Noemi
The study of primitive asteroids is relevant to the origin and nature of volatile and organic material in the early Solar System. Interest in spectral data from primitive asteroids considered the most likely source of primitive near-Earth asteroids (NEAs) has increased in anticipation of the two sample-return missions that will reach their targets during 2018: NASA's OSIRIS-REx and JAXA's Hayabusa2. Concurrently, the discovery of water ice on the surfaces of two primitive asteroids (24 Themis and 65 Cybele) placed the focus on the outer-belt, where more asteroids could harbor water ice on, or below the surface.In 2010 we started our PRIMitive Asteroids Spectroscopic Survey (PRIMASS) with the goal of studying the surface of primitive asteroids at different locations in the main belt, by means of visible and near-infrared spectroscopy. Here we present PRIMASS-L, a spectral library that will contain the results of PRIMASS. As of March 2018, this library gathers spectra of about 500 asteroids from 10 collisional families and two groups of asteroids that had been sparsely studied before (85% of our targets did not have published spectra and only 40% had visible photometry). PRIMASS uses a variety of ground-based facilities, including the 3.0-m NASA Infrared Telescope Facility (IRTF) on Mauna Kea (Hawai, USA) or the 10.4-m Gran Telescopio Canarias (GTC) at the El Roque de Los Muchachos Observatory (ORM, La Palma, Spain). This survey is on-going and aims to contain about 700 spectra by 2019. Making PRIMASS-L publicly available at the Small Bodies Node of the Planetary Data System (SBN-PDS, NASA) will enable synergies with other data sets containing physical parameters (e.g. polarimetric properties and geometric albedo) and family affiliation. This will push the characterization of the families and of primitive material to a new level and improve our understanding of the evolution of our Solar System and other planetary systems.
Herschel PACS/SPIRE Point Source Catalogs
Pinter, Sandor
The Herschel Space Observatory was the fourth cornerstone mission in the European Space Agency (ESA) science programme. It had excellent broad-band imaging capabilities in the far-infrared and sub-millimetre part of the electromagnetic spectrum. The PACS and SPIRE photometric cameras observed about 8% of the sky in six different wavebands. The Herschel/PACS Point Source Catalog contains 491033 objects detected in wavebands centered at 70, 100 and 160 µm, while the Herschel/SPIRE Point Source Catalog contains 1693718 objects observed at 250, 350 and 500 µm nominal wavelength. With most Herschel maps being confusion limited, uncertainties in flux densities were established as a function of structure noise and flux density, based on the results of artificial source injection experiments into real observational timeline data along a range of different backgrounds. Many sources have been rejected that do not pass the imposed SNR threshold, especially at flux densities approaching the local confusion limit. The catalogs are available on-line through ESA's Cosmos portal and the Herschel Science Archive.
Galactic foreground of extragalactic objects based on high angular resolution multi-wavelength observations
Pinter, Sandor
We estimate the column density of the Galactic foreground interstellar medium (GFISM) in the direction of selected extragalactic sources. All-sky Planck survey data in six wavebands might be used to trace the GFISM with a resolution of 9.7 – 32.3 arcminutes, while in selected areas Herschel PACS/SPIRE gives us additional 6 wavebands towards the shorter wavelength with a magnitude higher (5 – 36 arcseconds) resolution. High spatial resolution observations of the GFISM may be important recalculating the physical parameters of gamma-ray burst (GRB) host galaxies (e.g. star formation rate, stellar & dust mass) using the updated foreground parameters. The resolution of the Planck/Herschel maps is better than other available all sky survey data on the Galactic ISM. We show how much that resolution gain matters calculating the actual foreground column densities, and then deriving an intrinsic column density.
The galaxy cluster of GRBH051022 at z=0.8 by Subaru HSC
Pinter, Sandor
Gamma-ray bursts (GRBs) are the most powerful explosions in the Universe. To determine whether their host galaxies (GRBH) are in special positions in their local neighborhood we performed high spatial resolution multi-wavelength Subaru Hyper Suprime-Cam observations toward GRB051022. From the deep images one can derive photometric redshifts for the nearby galaxies which can be used to indentify the galaxy cluster where the GRB occured. Than the parameters of those galaxies can be estimated using SED fitting methods to derive the position of the GRBH within the cluster as well as the difference of some physical properties compared to the cluster's average.
Low - frequency observations and Cosmic Ray propagation in NGC 6946
Piotrowska, Julia
Cosmic Ray electrons (CREs), which are propagating through the interstellar medium in the presence of magnetic field are traced by radio synchrotron emission. Since low radio frequency CREs can travel to more distance regions from galactic disk than at higher frequencies hence more extensive radio synchrotron halos are expected to appear at longer wavelengths. Observations of the grand-design face-on spiral galaxy NGC6946 was conducted with the LOFAR High Frequency Antennas (HBA) in order to explore CREs propagation in interarm regions and extended disk.We also study the local radio - FIR correlation between non-thermal radio emission at 150\,MHz and the far - infrared emission at 70\,$\mu$m in arm and interarm region at scales 1kpc.We compare obtained radial profile of radio emission at 150\,MHz with its counterparts at 330\,MHz and 1.4\,GHz to study scale lengths of outer disk. We determined total magnetic field by assuming equipartition between the energy density of CREs(synchrotron emission) and magnetic field. Analysis of integrated radio emission spectra shows no significant flattening at low - frequencies due to thermal (free - free) absorption.
Planetary dynamics from observations of planets and spacecraft (ephemerides EPM2017 at IAA RAS)
Pitjeva, Elena
Dynamics of planets have been obtained by constructing high-precision Ephemerides of Planets and the Moon (EPM20017, iaaras.ru/en/dept/ephemeris/epm/2017) at the Institute of Applied Astronomy of the Russian Academy of Sciences, based on 800000 observations of planets and spacecraft in 1913-2015 (Martian orbiters and landers, MESSENGER, Venus Express, Cassini) and LLR data in 1970-2016. The model of planetary motion includes the gravitation interactions between the Sun, planets, the Moon, asteroids and trans-neptunian objects. The most important improvements in EPM at past three years were: the updated model of the orbital and rotation motion of the Moon as an elastic body having a rotating liquid core; updated planetary motion model with Lense-Thirring acceleration, perturbations from the largest 301 asteroids, 30 TNO, and two discrete rotating annuli (the Main asteroid belt and the Kuiper belt); more accurate relativistic barycenter definition; the construction of the long EPM2017H ephemeris covering the timespan of 13000 years. More than 360 parameters of EPM20017 were determined from all observations, including the total masses of the Main asteroid belt and Kuiper belt. EPM ephemerides serve as the basis for the Russian Astronomical and Nautical Astronomical Yearbooks, are planned to be used in the GLONASS and LUNA-RESOURCE programs, and are being used for determination of physical parameters: masses of asteroids, parameters of rotation of planets, the solar gravitation constant (GM_Sun) and its secular variation, PPN parameters, upper limit on mass of dark matter in the solar system. EPM can also be used in search of the remote supposed 9-th planet.
Early indications of Gamma-Ray Burst properties
Pizzichini, Graziella
I shall show some cases of properties of Gamma-Ray Bursts which already started to appear in early observations of Gamma-Ray Bursts, although sufficient statistical significance was reached only later on.
Properties of Gamma-Ray Bursts with and without detected redshift
Pizzichini, Graziella
I shall compare some properties of Gamma-Ray Bursts, duration, fluence and peak flux, for which the redshift has been detected, with those for which it was not possible to do so.
The Expansion of the SMC SNR 1E 0102.2-7219 as Seen in X-rays
Plucinsky, Paul
We measure the expansion of the forward shock of the Small Magellanic Cloud supernova remnant 1E 0102.2-7219 in X-rays based on Chandra X-Ray Observatory on-axis Advanced CCD Imaging Spectrometer (ACIS) observations from 1999 through 2017. We estimate a blast wave global expansion rate of 0.0253% +/- 0.0044% yr-1 (~ 1/4 of the previous X-ray measurement). We combine the expansion rate with the blast wave and reverse shock radii to generate a grid of one dimensional shock models for a range of ejecta masses and swept-up masses to constrain the progenitor mass, explosion energy, age, circumstellar density and unshocked ejecta mass. We find a constant density ambient medium does not reproduce the observed values. Models with a power-law density profile ~r-2 (appropriate for a uniform steady progenitor stellar wind) better reproduce the observed values of forward/reverse shock radii and forward shock velocity. For ejecta masses 6-12 solar masses and swept-up masses 10-30 solar masses, we find a range of progenitor masses 16-42 solar masses with explosion energies 0.22-0.58x1051 erg, ages ~2700-3300 yr, ambient interstellar densities 0.13-0.40 cm-3, and unshocked ejecta masses of 0.40-3.9 solar masses. The explosion energies are consistently below 1.0x1051 erg for the range of assumed values indicating a relatively low explosion energy for this supernova. Our blast wave velocity implies a lower limit on the post shock electron temperature of 0.7 keV, assuming Coulomb heating, which is consistent with the estimate from X-ray spectral analysis. This indicates a significantly smaller amount of energy going into accelerating cosmic rays than previously estimated.
Metallicity and Ionization Parameter and the Impact of Diffuse Ionized Gas
Poetrodjojo, Henry
We present metallicity and ionization parameter maps of star-forming face-on spiral galaxies from the SAMI galaxy survey Data Release 1. Self-consistent metallicity and ionization parameter maps are calculated simultaneously to account for the interdependence of the strong emission line diagnostics. We find that SAMI galaxies share a mass-independent characteristic metallicity gradient of -0.12 pm 0.05 dex/Re. We calculate ionization parameter maps and find no significant correlation with either SFR, sSFR or metallicity. We find a typical ionization parameter range of 7.0 < log(q) < 7.7 for our sample which lead to systematic deviations of up to 0.3 dex for the PP04 O3N2 metallicity diagnostic. We also show the effects of diffuse ionized gas (DIG) and spatial smoothing on metallicity gradients. Using high resolution data from the TYPHOON survey, we separate and remove the effects caused by DIG and measure the true metallicity gradient with 5 metallicity diagnostics of M83. We then simulate a range of lower resolution observations and quantify the impact this has when measuring the metallicity gradient where DIG removal is not possible. We find that at resolutions exceeding 1kpc/spaxel, the spatial resolution of several large IFU surveys, it is impossible to retrieve the true metallicity gradient due to DIG contamination.
The warped potential of the Milky Way revealed by Gaia DR2
Poggio, Eloisa
Among the open questions about Galaxy evolution, the origin and the dynamical nature of the Galactic warp is one of the most challenging. Possible candidates for generating warped discs are the triaxiality of dark matter haloes, a misaligned infall of gas and tidal interactions with satellite galaxies (among the others), but which one is at work in our own Galaxy is still unkown. The study of stellar kinematics could shed some light on this highly debated topic, given the intrinsic connection with the underlying forces. With the advent of the second Gaia data release, kinematics can be explored with exquisite precision on unprecedented spatial scales. We detect the large scale signature of the Galactic warp (up to distances of 7 kpc from the Sun) in the kinematics of two stellar samples having different typical age. The two samples contain respectively upper main sequence stars and giants, selected using 2MASS photometry and Gaia DR2 astrometry, without using individual extinction estimates. The signal shown by the two samples is similar, indicating that the mechanism producing the warp must be common to both dynamically young and old stellar populations. We conclude that the warp is a purely gravitational phenomenon, reflecting a warp in the gravitational potential of the Milky Way.
Vertical distribution of HMXBs in NGC 55: Constraining their centre of mass velocity
politakis, babis
SN induced kicks are a key parameter in the formation and evolution of X-ray binaries and their descendants such as short Gamma Rey Bursts and gravitational wave sources. Edge-on galaxies provide a unique environment for directly measuring the offset of X-ray binaries from their birth places due to SN kicks. We present a study of the spatial distribution of HMXBs in NGC55 our nearest edge-on galaxy. We find that the vertical distribution of HMXBs is puffed-up compared to the distribution of star formation. We model this effect with a smearing gaussian with a s ~ 0.43 kpc. Given the average travel time of HMXBs we find a center of mass velocity of 36 km/s, consistent with similar estimations in the Milky Way but higher than the Magellanic Clouds, in agreement with models for higher fraction of electron capture SN in lower metallicity environments.
Analysis of gas/dust productivity and molecular composition of cometary comae, which were investigated in 2008-2017
Ponomarenko, Vasyl
In 2008-2017 years we estimated the gas and dust productivity of comets 8P/Tuttle, 46P/Wirtanen, 81P/Wild 2, 103P/Hartley 2, ?/2009 K5 (McNaught), C/2009 P1 (Garradd), C/2013 US10 (Catalina), C/2014 Q2 (Lovejoy). The research has been performed on the basis of the optical spectra with an average resolution (?/?? ˜ 1300 and ?/?? ˜ 14000). The spectra were obtained on the mountain observatory «Peak ??rsk?l» (MPC code B18) and at the observation station "Lisnyky" (MPC code 585) with the help of the reflecting telescopes Zeiss-2000 (D = 2.0 m; F2 = 16 m) and AZT-14 (D = 0.48 m; F2 = 7.7 m). Also on the basis of obtained spectral material has been carried out the identification of the spectral emission lines and bands of molecules CN, C2, C3, NH2 and other. With the help of Haser and Shulman models were calculated some physical parameters of neutral gaseous and dust cometary atmospheres. The distributions of general and reflected energy along the slit of the spectrograph have been built.The obtained data have been analysed. The performed analysis has showed that the ratio of gas productivity to relative dust productivity (Q/Af?) of comets can indicate on the size of the cometary nucleus. Probable for most large nuclei (D > 4 km) the ratio (Q/Af?) at the heliocentric distances (1 AU < r < 2 AU) has a much smaller value than for small nuclei (D < 0.6 km).
The Role of Halo Spin and Environment in Shaping Galaxy Morphology
Porras, Antonio J.
We use the semi-analytic model DARK SAGE to study the predicted relationship between halo spin, galaxy morphology, and environment. Recent studies have used hydrodynamical simulations to study the distribution of dark matter (DM) spin for dispersion and rotation dominated galaxies. However, no known study has linked the relationship between DM spin, morphology and the environment in which galaxies live in. In our study, we explore whether DM spin and/or environment play an important role in shaping the morphology of galaxies. We define high and low density regions using the density in a sphere with 8Mpc radius. Using a kinematic definition of morphology, our preliminary results show that at fixed halo mass, galaxy morphology changes with DM spin for galaxies in both high and low density environments. Surprisingly, bulge dominated galaxies have a slightly higher halo spin compared to disk dominated galaxies. Furthermore, for central galaxies this is true in both high and low density environments, while for satellite galaxies the correlation between DM spin and galaxy morphology is only present in low density regions.
Studying the circumstellar environments of B[e] supergiant binaries using high-cadence optical spectroscopy
Porter, Augustus
B[e] supergiants, supermassive stars exhibiting the B[e] phenomenon of strong Balmer line emission and forbidden line emission, are a rare and thereby poorly understood class of star. Both their formation pathways and the origin of their B[e] phenomena remain unclear. I will present a case study of GG Carinae (GG Car), a little studied and eccentric Galactic B[e] supergiant binary, based on successive Global Jet Watch spectroscopy data which has been collecting high-time-sampled optical spectra since early 2015. I use Fourier analysis to examine the behaviour of the orbital period of the inner binary, and how this is manifested in the circumstellar environment. I will also present an analysis of forbidden emission lines that have very different temporal characteristics from those that depend straightforwardly on the orbital period, and their connection to the circumbinary-orbiting material in this system. The equivalent width of the Ha line in GG Car is strongly dependent on the period of the inner binary, suggesting that the amount of emitting circumstellar matter varies strongly with orbital phase due to alternating accretion/decretion of material from the stellar surfaces. Despite GG Car having so far not been observed in the X-Ray band, if the secondary is a compact object then the system is similar in phenomenology to variable X-Ray binary sources consisting of classic Be and neutron stars, and the study of GG Car can shed further light on the physics of X-Ray binaries.
A photometric/spectroscopic modelling survey of FU Ori Objects with Herschel
Postel, Andreas
Episodic accretion plays a major role in the accretion history of young stars._x005F In particular, FU Orionis objects (FUOrs) undergo accretion outbursts during_x005F which the_x005F accretion rate rapidly increases from typically 10^-7 M_Sun / yr to 10^-4_x005F M_Sun / yr and stays high over time scales of several decades to hundreds of_x005F years. The origin of such accretion outbursts remains unclear and could be due_x005F to viscous-thermal instabilities in the disc, thermal instabilities induced by_x005F density perturbations due to e.g. a massive planet in the disc, tidal effects_x005F from close companions, a combination of gravitational instability and the_x005F triggering of the magnetorotational instability, or again accretion of clumps_x005F in a gravitationally unstable disc._x005F Herschel has observed 12 FUors with PACS and SPIRE in both photometric and_x005F spectroscopic modes. We will present results from our analysis, which combines_x005F Herschel and Spitzer data with ground-based data together with_x005F hydrodynamical simulations and thermo-chemical modeling using a modified_x005F version of the ProDiMo tool, with the goal to improve our understanding of_x005F episodic outbursts in the first steps of life of low-mass young stars.
EREBUS: the EuRopean Extinction BUmp Survey
Postel, Andreas
Dust in the interstellar medium (ISM) is intimately linked to the birth and death of stars. However, despite being of such fundamental importance to the evolution of our own and nearby galaxies, the dynamic behaviour and composition of the ISM are not yet fully understood. A number of observations by IUE of reddened Milky Way OB stars revealed a strong UV extinction feature around 2175 Å and a precipitous extinction rise to the far UV along the lines of sight. Whilst the carrier(s) for this are at present still being debated, multiple laboratory studies suggest carbonate grains to be the key constituent. EREBUS is a mission concept being developed to study the composition of the ISM in both the Milky Way and Local Group Galaxies, principally by mapping the spatial distribution of the UV extinction features. As the shape and position of both the bump and the rise are sensitive to the dust composition along the line of sight, the survey will provide a wealth of information about the spatial distribution of the carrier(s). In this way, we will be able to understand better the time evolving behaviour of the ISM, which is critical to the study of galaxy evolution. The mission proposes to deploy a satellite observatory equipped with a coarse UV spectrograph (R∼100 from 3000 to 1000 Å) to map the extinction curve variability in the Milky Way in 3 dimensions (in conjunction with data from Gaia) and in the Local Group in 2 dimensions. In this paper, we detail the scientific goals for the project, discuss a proposed observation strategy using an iterative process to develop a hierarchical map, and finally outline the instrument requirements and preliminary spacecraft architecture._x005F _x005F Keywords: Dust, UV bump, Interstellar Medium
Polycyclic Aromatic Hydrocarbon Space Telescope (PAHST): Towards a complete view of star formation in the early Universe at z = 4.5 - 6.0
Postel, Andreas
This paper presents the Polycyclic Aromatic Hydrocarbons Space Tele-scope (PAHST) mission concept which is designed to probe star formationin the Early Universe by detecting Polycyclic Aromatic Hydrocarbon (PAH)features and emission lines redshifted to 30 – 200 µm at 4.5 < z < 6.0, aregion where no earlier measurements exist. The mission will reveal the his-tory of star formation in the early Universe by probing star formation indistant galaxies. Secondary science objectives are the study of the structureof high density filaments in the Interstellar Medium (ISM) of our Galaxy, andan investigation into the nature of cool brown dwarfs and their surroundingdusty disks. These science objectives require an ESA L-class infrared spacetelescope. The spacecraft will be launched by an Ariane 6 launcher to anoperational orbit around Lagrange point L2. The telescope is an on-axis de-sign with a 8 m segmented, foldable mirror. Detectors are a high sensitivityspectrometer and photometer. This paper presents the science case for theprimary and secondary science objectives and details a feasible spacecraftdesign concept. The mission concept, science case and technical feasibilitystudy were carried out during the Alpbach Summer School 2017, “The DustyUniverse,” and its five-day follow-up session “Post Alpbach Event” at theESA Academy Training and Learning Centre in Redu, using the concurrentengineering approach.
Dynamical models of dwarf spheroidals in the Gaia era
Posti, Lorenzo
The Gaia mission is revolutionizing our knowledge of the Local Group by allowingthe 3D motions of individual stars to be measured even in the brightest dwarfSpheroidals (dSphs). These measurements are of vital importance for dynamical studiesof dSphs since they completely break the mass-velocity anisotropy degeneracy andthus they allow for a uniquely robust inference on how dark matter is distributed.As data quality is making a huge leap forward, dynamical models must keep up thispace to stand up for the challenge of finally pinning down the dark matterdistribution in the systems that currently pose the biggest threat to standardcosmological models.I will show how our pioneering measurement of the proper motion of stars in theSculptor dSph (obtained combining Hubble+Gaia, Massari et al. 2018) can be usedto constrain how dark matter is distributed in the galaxy. Novel multi-componentdynamical models generated with analytic distribution functions (that we introducedin Pascale et al. 2018) are crucial to this end: we demonstrate how the inferenceon the galaxy's physical properties changes when using our new Bayesian approach,maximizing the natural likelihood that is the distribution function, as opposed toa more classical approach, of merely fitting to the radially binned starcount/line-of-sight velocity profiles. The likelihood of the model strongly dependson the proper motions for stars that have them measured, while it is marginalizedover the tangential velocity for those that do not have proper motions.The distribution function models that we use not only account for the multiplestellar populations revealed in Sculptor, but they also well characterize theirdifferent kinematics, hence offering important constraints on dwarf galaxy formationmodels.
Internal properties of dwarf galaxies in the MATLAS survey and variation with environment
Poulain, Melina
The MATLAS project, aimed at studying the outer most regions and surroundings of a complete sample of nearby field Early Type Galaxies, has produced deep multi-band optical images with limiting surface brightness down to nearly 29 mag/arcsec2 in the g band. Such images obtained with MegaCam on the CFHT have optimal conditions (large scale of view, high sensitivity) for dwarf galaxies detection. We have made a systematic survey of the dwarf galaxy satellites located within 153 fields of one square degree each. Based on semi-automatic detection algorithms, we obtained a catalog of 3674 potential dwarf galaxies situated in low density environments. All candidates were visually inspected to exclude likely foreground/background objects or artifacts. Remaining projection effects are partly compensated by the high number statistics. Assuming for the satellites a distance corresponding to that of their host, we derived for all them their basic properties - color, mass, Sérsic index, effective radius, nucleation, morphology - and their variation with environment. We found a large number of dwarf ellipticals, with a significant fraction of nucleated ones, and ultra diffuse galaxies that was unexpected outside the cluster environment.
On the validity of the frozen-in approximation for acoustic wave propagation through solar granulation
Poulier, Paul-Louis
Solar acoustic waves interact with near-surface convection, such that seismic travel times may be affected. Since the wave period is of the same order as the correlation time of granulation, it is not obvious if the commonly used stationary-medium approximation is valid for the study of this acoustic wave scattering. Using Monte-Carlo simulations, we numerically simulate the propagation of acoustic wave packets in a 1D medium where the sound speed is treated as a random variable of time and space in a band of fixed width. We compute the first and second order moments of the waveforms over many realizations of the medium to study the impact of the turbulent medium.We find that the average (coherent) field is damped throughout the medium, and that the effective speed decreases, both effects being proportional to the mean square of the perturbation. The attenuation and the decrease in phase speed in a granulation-like medium are overestimated by considering a stationary medium. Acoustic scattering also triggers a deviation from the mean amplitude that is less sensitive to the correlation time of the medium than the mean wave field.In summary, we find that the frozen-in medium approximation is more appropriate to model the fluctuations of the wave field rather than to model the propagation of the mean wave field.
Optimal averaging for helioseismic measurements using the singular value decomposition
Pourabdian, Majid
Performing inversions in time--distance helioseismology is demanding due to the large amount of data and the high level of noise. Averaging the input data is required to increase the signal-to-noise ratio and make the problem tractable. Here, we use the singular value decomposition method to determine the optimal weights to recover flows at a given 3D location in the solar interior. We compare averaging kernels and noise levels for different choices of observables. We find that averaging kernels are more localized when using the cross-covariance function in frequency domain, rather than travel times as input data.
Probing superorbital variations in SMC X-1 with Suzaku through simultaneous timing and spectral analysis
Pradhan, Pragati
SMC X-1 was observed with Suzaku ten times during different intensity states of the superorbital variation in 2011. We present a broadband (0.3-70 keV)spectral analysis and a detailed joint comparison of the spectra in these intensity states for the first time and interpret the results to map accretion geometry/mechanisms. The spectrum in all the states can be described by an absorbed powerlaw with a smoothened high energy cutoff. Additional black-body component and Fe K emission line is detected, apart from few other low energy emission lines. The spectral shape is also dependent on flux with the hard X-ray spectrum steepening with increasing flux. Through spectral analysis, we probe the nature of the absorber in the precessing warp of SMC X-1 that cause the superorbital modulation. We have carried out orbital corrections for Doppler shift in the HXD lightcurves and report detection of pulsations in hard X-rays in all but one observation. Detection of the X-ray pulses in the low state help us limit the contribution of the scattering/reprocessed component of the X-ray emission in the low state.
Multitude of iron lines in OAO 1657-415 detected with Chandra
Pradhan, Pragati
We present a high resolution X-ray spectrum of the accreting X-ray pulsar, OAO 1657-415 with HETG onboard Chandra, revealing the presence of a broad line component at 6.3 keV in addition to the neutral iron K α line at 6.4 keV. This is interpretated as Compton shoulder arising from the Compton scattering of the 6.4 keV flourecense photons making OAO 1657-415 the second accreting neutron star where such a feature is detected. A Compton shoulder reveals the presence of dense matter surrounding the X-ray source. We did_x005F not detect any periodicity in the lightcurve and obtained an upper limit of ∼ 2% for the pulse fraction during this observation. This could be due to the smearing of the pulses when X-ray photons are scattered from a large region around the neutron star. In addition to the K α , Fe K β and Ni K α lines already reported for this source, for the first time, we also report the presence of Helium and Hydrogen-like iron emission lines at 6.63, 6.7 and 6.97 keV in the HETG spectrum. The detection of such ionized lines are rare in X-ray binaries and shows very high ionisation parameter in the surrounding medium.
Formation History of Binary Clusters in the Large Magellanic Cloud
Priyatikanto, Rhorom
Among tens of dwarf galaxies in the local vicinity, Large Magellanic Cloud (LMC) is known as the prototype of Magellanic Irregulars which is rich in gas and star formation. Global history of star or cluster formation in the LMC has beed the center of interest in several studies as it is thought to be influenced by tidal interaction with the Small Magellanic Cloud (SMC) and even the Milky Way. The last episode of close encounter between LMC and the Milky Way is believed to increase the velocity dispersion and probability of collision among molecular clouds which in turn induce formation of new stellar systems. With the right input of kinetic energy, formation of substructure within the system is possible and primordial binary cluster with appealing dynamical behaviour might be formed.In this study, we focus on the formation history of the LMC deduced from age distribution of its star clusters. In relation with the study of binary star clusters in this dwarf galaxy, the apparent binary fraction (e.g. percentage of cluster pairs) in different epoch are calculated and analyzed.From the established distributions, it can be deduced that the binary clusters tend to be young (~100 Myr) while their locations coincide with the locations of star forming complexes. There is an indication that the binary fraction increases as the rise of star formation rate in the last millions years. In the LMC, the increase of binary fraction at t = -100 Myr can be associated to the last episode of close encounter with the Small Magellanic Cloud at t = -150 Myr. This observational evidence supports the theory of binary cluster formation through the fission of molecular cloud where the encounter between galaxies enhanced the clouds velocity dispersion which in turn increased the probability of cloud-cloud collisions that produce binary clusters.
Prediction of Limb Flares Based on Coronal Images
Priyatikanto, Rhorom
Disregarding the existence of active longitudes in dynamical Carrington frame of reference, solar flares can be considered as isotropic phenomenon in heliographic longitude space. Flares may occur on any heliographical longitude and modern society requires ample capability to forecast their occurrence and their subsequent effects to Earth's space weather.This work aims to characterize solar active region based on the extreme ultraviolet coronal images. Photometric and geometric properties will be cultivated to characterize the active region. Characterization of emerging active region on the far east region will be the ultimate goal in this context. Flare probability model based on the observed brightness of solar corona above any active region will be established according to that charaterization.
Confronting Mixing Length Theory
Provencal, Judith
The dynamics of convection influence many key aspects of stellar modeling, ranging from the effects of convective overshoot to supernovae to stellar ages. The properties of stars inferred from stellar modeling are even used to determine the nature of associated exoplanets. We all know that convection is a highly turbulent, three dimensional process that involves nonlocal motions. Yet convection is traditionally treated using mixing length theory (MLT), a simple, local time independent phenomenological description of "average" convective cells. . Convection remains the largest source of theoretical uncertainty in all stellar modeling. We have developed a technique that provides empirical constraints on the behavior of convection in hydrogen and helium atmospheres. Convective light curve fitting recovers the thermal response timescale at the base of a pulsating white dwarf's convection zone. By sampling pulsating white dwarfs over a range of temperatures spanning the hydrogen and helium pulsation instability strips, we can place constraints on the development of white dwarf convection zones. Our results show that mixing length parameters vary with effective temperature for hydrogen atmosphere white dwarfs, and follow no obvious pattern for helium atmosphere white dwarfs. These results can be used to calibrate MLT, validate the newest 3D hydrodynamic simulations, explain differences in convection parameters in hydrogen and helium atmospheres, and expand on results from similar studies.
The depth dependence of solar equatorial Rossby waves
Proxauf, Bastian
Here we use local helioseismology and local correlation tracking of granulation to infer horizontal flows on the solar surface and in the solar interior. From these flows, we compute maps of the radial vorticity at different depths in order to study Rossby waves.We show that the frequencies of these waves agree well with a simple theoretical dispersion relation. Also, we show that Rossby waves have significant amplitudes in the first 20 Mm below the surface and investigate the dependence of the Rossby waves on depth. We find that, both in terms of power and phase, the waves do not exhibit a strong depth dependence.
Spectra Stellar Libraries
Prugniel, Philippe
Spectra stellar libraries are collections of spectra of either observed stars or synthetic models. They are often asembled for a specific purpose and accordingly their spectral coverage, spectral resolution, and coverage of a physical parameters space can be very different. They are essential tools for a variety of topics, as ingredient for building stellar population models or reference for stellar physics... or as technical tools for calibrating data-reduction process or exposure time calculators.This presentation will describe recent efforts made by an IAU Working Group under the G5 commission to improve the description and access to existing libraries, and help the evolution of new libraries. The characteristics and first applications of the new UV to NIR library of empirical spectra observed with the X-Shooter spectrograph will be discussed.
Kinematic surveys with the ELT
Puech, Mathieu
Integral-field spectroscopy of distant galaxies is now routinely obtained on 8m telescopes. However, there is still much to learn on the dynamics of distant galaxies: exploring the kinematics of galaxies at the lowest mass range out to z~2-3 or measuring dark matter profiles in galaxies out to z~4 are two examples of exciting surveys out of reach of current facilities but that the ELT will be make possible. I will present several such potential surveys that the ELT could conduct, illustrated with results of simulations we obtained over the past ~ 10 years, and discuss coordinated strategies between different instrument projects, in particular the first-light IFU spectrograph HARMONI and the MOS MOSAIC.
The Lyman Continuum Leakage of the dwarf galaxy Tololo 1247-232 under review
Puschnig, Johannes
The driving mechanism of the reionization of the Universe is yet not well constrained, but low- and intermediate mass galaxies are widely discussed as source of ionizing photons, i.e. Lyman Continuum (LyC). However, proof of emerging LyC emission is an ongoing observational challenge at all redshifts. Using highly resolved photometry and far-UV spectroscopy obtained with the Hubble Space Telescope (HST) as well as interferometric observations performed with the Karl G. Jansky Very Large Array (VLA), we have studied the ionized and neutral gas content in the local dwarf galaxy Tololo 1247-232. My talk is based on Puschnig et al. (2017), describing physical mechanisms that drive the LyC escape in Tololo 1247-232, which is to date one of the very few known/confirmed LyC emitters in the Universe.Using HST's Cosmic Origins Spectrograph (COS), in combination with an improved data reduction routine, we have directly measured the amount of LyC emerging from the galaxy, finding an escape fraction of 1.5+/-0.5 percent only, i.e. the lowest LyC escape fraction reported for the galaxy so far. We further use far-UV absorption line analysis to probe the neutral and ionized gas, e.g. the covering fraction of the neutral medium could be constrained. We show that the LyC photons emerge from density bounded regions and finally escape through a clumpy medium. However, from Lyman Alpha line analysis, we also conclude that an additional diffuse interclump medium must be present that prevents Lyman Alpha to be seen at systemic velocity. The LyC escpae is further supported by our VLA 21cm observations, from which a very low gas fraction of less than 20 percent could be derived.
An HST and VLA view of the physics that drive the emerging ionizing flux (LyC) in the local dwarf galaxy Tololo 1247-232
Puschnig, Johannes
The driving mechanism of the reionization of the Universe is yet not well constrained, but low- and intermediate mass galaxies are widely discussed as source of ionizing photons, i.e. Lyman Continuum (LyC). However, proof of emerging LyC emission is an ongoing observational challenge at all redshifts. Using highly resolved photometry and far-UV spectroscopy obtained with the Hubble Space Telescope (HST) as well as interferometric observations performed with the Karl G. Jansky Very Large Array (VLA), we have studied the ionized and neutral gas content in the local dwarf galaxy Tololo 1247-232. My talk is based on Puschnig et al. (2017), describing physical mechanisms that drive the LyC escape in Tololo 1247-232, which is to date one of the very few known/confirmed LyC emitters in the Universe._x005F Using HST's Cosmic Origins Spectrograph (COS), in combination with an improved data reduction routine, we have directly measured the amount of LyC emerging from the galaxy, finding an escape fraction of 1.5+/-0.5 percent only, i.e. the lowest LyC escape fraction reported for the galaxy so far. We further use far-UV absorption line analysis to probe the neutral and ionized gas, e.g. the covering fraction of the neutral medium could be constrained. We show that the LyC photons emerge from density bounded regions and finally escape through a clumpy medium. However, from Lyman Alpha line analysis, we also conclude that an additional diffuse interclump medium must be present that prevents Lyman Alpha to be seen at systemic velocity. The LyC escpae is further supported by our VLA 21cm observations, from which a very low gas fraction of less than 20 percent could be derived.
The Lyman Continuum Leakage of the dwarf galaxy Tololo 1247-232 under review
Puschnig, Johannes
The driving mechanism of the reionization of the Universe is yet not well constrained, but low- and intermediate mass galaxies are widely discussed as source of ionizing photons, i.e. Lyman Continuum (LyC). However, proof of emerging LyC emission is an ongoing observational challenge at all redshifts. Using highly resolved photometry and far-UV spectroscopy obtained with the Hubble Space Telescope (HST) as well as interferometric observations performed with the Karl G. Jansky Very Large Array (VLA), we have studied the ionized and neutral gas content in the local dwarf galaxy Tololo 1247-232. My talk is based on Puschnig et al. (2017), describing physical mechanisms that drive the LyC escape in Tololo 1247-232, which is to date one of the very few known/confirmed LyC emitters in the Universe._x005F Using HST's Cosmic Origins Spectrograph (COS), in combination with an improved data reduction routine, we have directly measured the amount of LyC emerging from the galaxy, finding an escape fraction of 1.5+/-0.5 percent only, i.e. the lowest LyC escape fraction reported for the galaxy so far. We further use far-UV absorption line analysis to probe the neutral and ionized gas, e.g. the covering fraction of the neutral medium could be constrained. We show that the LyC photons emerge from density bounded regions and finally escape through a clumpy medium. However, from Lyman Alpha line analysis, we also conclude that an additional diffuse interclump medium must be present that prevents Lyman Alpha to be seen at systemic velocity. The LyC escpae is further supported by our VLA 21cm observations, from which a very low gas fraction of less than 20 percent could be derived.
Analysis of the exoplanet containing system Kepler-13
Püsküllü, Çaglar
We have applied the close binary system analysis program WINFITTER, with its physically detailed fitting function, to an intensive study of the complex multiple system Kepler-13 using photometry data from all 13 short cadence quarters downloaded from the NASA Exoplanet Archive (NEA) (http://exoplanetarchive.ipac.caltech.edu). The data-point error of our normalized, phase-sequenced and binned (380 points per bin: 0.00025 phase interval) flux values, at 14 ppm, allows the model’s specification for the mean reference flux level of the system to a precision better than 1 ppm. Our photometrically derived values for the mass and radius of KOI13.01 are 6.8 ± 0.6 MJ and 1.44 ± 0.04 RJ. _x005F The star has a radius of 1.67 ± 0.05 Ro. Our modelling sets the mean of the orbital inclination i at 94.35 ± 0.14 degree, with the star’s mean precession angle φp = 49.1 ± 5.0 and obliquity θo = 67.9 ± 3.0 deg, though there are known ambiguities about the sense in which such angles are measured. We could confirm a small but steady diminution in the cosine of the orbital inclination over the 17 quarter timespan. This is accompanied by a slight increase of the star’s precession angle (less negative), but with no significant change in the obliquity of its spin axis. There are suggestions of a history of strong dynamical interaction with a highly distorted planet rotating in a 3:2 resonance with its revolution, together with a tidal lag of ~30 deg. The mean precessional period is derived to be about 1000 y, but at the present time the motion of the star’s rotation axis appears to be supporting the gravitational torque, rather than providing the balance against it that would be expected over long periods of time. The planet has a small but detectable backwarming effect on the star, which helps to explain the difference in brightness just after transit and just before occultation eclipses. In assessing these findings it is recognized that sources of uncertainty remain.
High-Resolution Empirical Profiles of Diffuse Interstellar Bands
Puspitarini, Lucky
Diffuse interstellar bands (DIBs) are a set of mysterious interstellar absorption features detected mostly in the optical and near infrared. Although we do not know utterly the carriers of the DIBs, they can be a promising tracer of the interstellar matter (ISM). DIB databases from stellar spectroscopic surveys can be used as a complementary tool for locating interstellar (IS) clouds. To perform an automated DIB fitting to the spectroscopic data, DIB shape model is needed. But unlike interstellar lines, the profiles of the DIBs are often asymmetric and have substructures. In this work, we establish new empirical individual DIB model based on the average profile of DIB by using high-resolution spectra recorded with NARVAL spectrograph. We also disscuss variations of the profiles and show correlations between individual DIBs.
Nearby void dwarf galaxies: recent results, the ongoing project and prospects
Pustilnik, Simon
Properties of dwarf galaxies formed and evolved in the lowest densityenvironment still remain largely unexplored and poorly understood. Especiallythis concerns the low-mass end, namely at M_B > -14, M_bar <~10^9 Mo. Weoverview the results of the only systematic study of the faintest void dwarfsbased on the sample of hundred galaxies in the nearby Lynx-Cancer void. Furtherwe describe the ongoing project aiming to form and study a nearby void galaxysample (R < 25 Mpc) over the whole celestial sphere. About 1500 objects of6830 known galaxies with distance less than 25 Mpc fall within 25 voidsdelineated by ~460 luminous galaxies/groups. The major sizes of voids rangefrom ~13 to ~28 Mpc. About 1150 of 1500 void galaxies reside deeply in voids,having distances to the nearest luminous neighbour of 2-11 Mpc. About 330 ofthem have M_B > -14, with the faintest objects reaching M_B~-10. About 200nearest void galaxies reside in the Local Volume (D < 11 Mpc). We summarizethe main statistical properties of the nearby void galaxy sample and someunexpected findings, and outline the prospects of study of both, the voiddwarf properties and the fine structure of voids.
Very gas-rich extremely metal-poor blue void dwarfs
Pustilnik, Simon
Half-dozen of extreme representatives of void dwarf galaxy population werefound in our study of evolutionary status of a hundred galaxies in the nearbyLynx-Cancer void. They are very gas-rich, extremely low-metallicity[7.0 < 12+log(O/H)<~7.3] objects, with blue colours of outer parts. Thecolours indicate the ages of the oldest visible stellar population of one toa few Gyr. They all are intrinsically faint, mostly LSB, with M_B range of-9.5 to -14 mag. Thus, their finding is a subject of the severe observationalselection. The recent advancement in search for such objects in other nearbyvoids resulted in doubled their total number. We summarize all available dataon this group of unusual void dwarf galaxies and discuss them in the generalcontext of very low metallicity galaxies and their possible formation andevolutionary scenarios.
The Dwarf Galaxy–Environment Connection as seen by the Next Generation Fornax Survey
Puzia, Thomas H.
The Next Generation Fornax Survey (NGFS) is a panchromatic imaging campaign that covers the virial sphere of the Fornax galaxy cluster in optical (u’g’i’, using DECam@CTIO) and near-infrared filters (JKs, using VIRCam@VISTA). The survey targets all baryonic structures down to point-source luminosities typical of globular clusters and reaches surface brightness limits deep enough to detect ultra-diffuse and LSB dwarf galaxies. Here we present the first map of the spatial distribution of a rich system of more than 600 dwarf galaxies inside half of Fornax' virial radius that demonstrates, for the first time, the transition from the dense central dwarf galaxy population to the less dense outer environment. We present strong evidence for spatial substructure in the dwarf galaxy distribution and show that dwarf galaxies are significantly clustered on spatial scales less than ~100 kpc. In the context of overall dwarf galaxy properties, we discuss our findings in relation to other ongoing surveys of the local universe led by our team.
The GEMS/GSAOI Galactic Globular Cluster Survey (G4CS)
Puzia, Thomas H.
We present the first results from the GeMS/GSAOI Galactic Globular Cluster Survey (G4CS) of the Milky Way globular clusters (GCs) NGC 3201 and NGC 2298. Using the Gemini South Adaptive Optics Imager (GSAOI) in tandem with the Gemini Multi-conjugate adaptive optics System (GeMS) on the 8.1-meter Gemini-South telescope, we have collected deep near-IR observations of the clusters, resolving their stellar populations down to Ks ? 21 Vega mag. Point spread function (PSF) photometry was performed utilizing a spatially-variable PSF to overcome AO-correction variations across the field of view. The resulting photometric catalogues were combined with data from the Hubble Space Telescope (HST) to augment the photometric wavelength coverage for both clusters spanning the near-ultraviolet (UV) to near-infrared (near-IR). We apply 0.14 mas/year accurate proper motion cleaning and differential reddening corrections, utilizing the characteristic scale length defined as the color-luminosity difference between the lower main sequence knee (MSK) and main sequence turn-off (MSTO). Given the quality of our data, we found that the Ks vs. F606W-Ks and F336W vs. F336W-Ks color-magnitude diagrams (CMDs) provided the most diagnostic power, and as such, we use them to derive the stellar population ages, distances and reddening values for both clusters. We perform isochrone-fitting using three different isochrone sets, deriving best-fit absolute ages of 12.46 ± 0.46 Gyr and 12.64 ± 0.38 Gyr for NGC 3201 and NGC 2298, respectively, using a weighted average over the two color combinations, following a pseudo-?-squared determination of the best-fit isochrone set. Our derived parameters are in good agreement with recent age determinations of the two clusters, with our constraints on the ages ranking among the most statistically robust. These findings demonstrate the power of GeMS/GSAOI as a tool for the exploration of both cluster characteristics and their constituent stellar populations.
Accurate OH maser positions in SPLASH
Qiao, Hai-Hua
Masers are important astrophysical objects which can be used to understand the chemical and physical environment of the interstellar medium (ISM). The hydroxyl radical (OH) was the first molecule discovered in the ISM and can produce strong stimulated spectral line emission (OH masers). Our research measured accurate positions of OH masers based on the results from the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH). SPLASH observed OH in four ground-state transitions across the inner Galactic plane (332 degrees < l < 10 degrees, |b| < 2 degrees; 358 degrees < l < 4 degrees, 2 degrees < b < 6 degrees; in total 176 square degrees). We used the Australia Telescope Compact Array to accurately determine the positions of these OH masers. We then compared these positions with the Methanol Multibeam survey, H2O Southern Galactic Plane Survey, Red MSX Source, SIMBAD and the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire maps to identify which kind of astrophysical object they are associated with. We have finished the accurate position measurements for 80 square degrees (Qiao et al. 2016a, Qiao et al. 2016b, Qiao et al. 2018, submitted). In my talk, I will present these results and some statistical work in details.
The timing properties of black hole transient MAXI J1535-571 during its 2017 outburst from HXMT observations
QU, Jinlu
We study the state evolution and QPO properties of the new black hole candidate MAXI J1535-571 duringits 2017 outburst from Insight-HXMT observations from 2017 September 6 to 23 . The results show that the source exhibits state transition from low hard state to hard intermediate state and the QPO phenomena. The energy dependence and time lags of the QPOs up to 100 keV are studied. The source is similar to typical BHT GX 339-4.
High Ionization State Ions in Galactic Gaseous Halos
Qu, Zhijie
The warm-hot gaseous medium is theoretically predicted to be an important component of the universe, contributing about 30-40 % of the total baryonic content. The hosts of cosmic high-temperature gas can be divided into: galactic gaseous halos; unvirialized intergalactic medium (cosmic filaments); and intra-group (cluster) gas. We built a semi-analytic gaseous halo model to connect the gaseous halo with the galaxy disk by assuming the star formation rate in the disk is balanced by the radiative cooling rate of the gaseous halo (Qu & Bregman 2018). This model reproduces most of the observed absorption column density of high ionization state ions for a wide range of galaxy masses (i.e., O VI, O VII, Ne VIII, Mg X, and O VIII). Convolving this model with the galaxy density (stellar mass function), we predict the gaseous halo contribution for the observed column density distribution of high ionization state ions. The predicted column density distribution reproduces the general shape of the observed column density distribution -- a broken power law with the break point at logN=14.0 for the O VI. Our modeling suggests that the high column density systems originate from the galaxies with particular mass ranges for different ions, where the virial temperature is about the temperature of the ionization fraction peak. Some differences at lower columns between our models and observations indicate that absorption by the intra-group(cluster) medium and intergalactic medium are also contributors to the total column density distributions. The emission for different ions is calculated in our gaseous halo model, which indicates that the emission survey can be complementary to the absorption studies to determine the properties of the hot gaseous halo.
Searching for chemical signatures of planet formation
Rab, Christian
In the last couple of years, high spatial resolution observations of protoplanetary disks have revealed structures such as gaps, rings, vortices and spiral arms. Those structures are probably signposts of ongoing planet formation indicating that protoplanetary disks are actually already planet-forming disks.Most of these structures have been detected using telescopes such as ALMA and SPHERE by observing the dust component, and it is not clear to what extent the gas follows the dust distribution and to what extent those structural features impact the chemistry in planet-forming disks. We model those three-dimensional structures using the 3D dust radiative transfer model MCMax3D and the thermo-chemical model ProDiMo (PROtoplanetary DIsk MOdel). With such an approach it is possible to infer self consistently the physical and chemical conditions at the location of ongoing planet formation such as inside a gap. Via synthetic observables for the dust and the gas, a direct comparison of the models to existing and future observations is also possible. This allows for deriving stringent constraints on properties such as the gas to dust ratio, temperature and chemical composition of the gas and the solids.We present first exemplary results for models with vortices, gaps and embedded planets. With those models we aim for answering questions such as: are the observed dust gaps also depleted in gas, and if yes to what extent; do dust overdensities have a significant impact on the gas-phase and ice chemistry and are planets required to explain those structures. Answering those questions provides stringent constraints for planet-formation theories and initial conditions for the formation of planetary atmospheres. We also discuss what we can already learn from modelling of existing observations and what kind of observations are required to provide further constraints on the planet formation process.
Constraining the stellar energetic particle flux in young solar-like stars
Rab, Christian
High energy ionization sources such as X-rays, cosmic rays and stellar energetic particles (stellar cosmic rays, SP) can ionize molecular hydrogen, the most abundant chemical species in the environment of young stars. Therefore, they play a crucial role in the chemistry and evolution of the circumstellar environment. Energetic particles are likely the reason for the abundance anomalies of short-lived radionuclides measured in meteoritic material. However, it is still unclear if those anomalies are a consequence of enhanced irradiation by cosmic rays (e.g. nearby supernovae) or enhanced irradiation by stellar energetic particles in the early stages of the solar system formation. We present models which allow for studying the impact of SP on the chemistry of the circumstellar material of young solar-like stars and the observability of this interaction.We use the radiation thermo-chemical disk code ProDiMo (PROtoplanetary DIsk MOdel) to model the impact of those high-energy ionization sources on the chemistry of planet-forming disks. The model includes X-ray radiative transfer and makes use of particle transport models to calculate the individual molecular hydrogen ionization rates in the disk. We study the impact on the chemistry via the ionization tracers HCO+ and N2H+. We argue that spatially resolved observations of those molecules combined with detailed models allow for disentangling the contribution of the individual high-energy ionization sources and to put constraints on the SP flux in T Tauri stars.We further present a new extension to ProDiMo, which allows modelling of the disk plus envelope structure of embedded stars (i.e. Class I). Recent observations indicate that enhanced stellar particle irradiation might already happen in those early phases of the star and planet formation process. We present first results of our self-consistent high energy ionization models for this early stages and discuss possible constraints for this scenario.
Spectral variability in the Fermi GBM GRBs'
Racz, Istvan I.
Gamma-ray bursts (GRBs) are the most powerful explosion in the far Universe. Studying the GRBs spectra may reveal some important physical information of GRBs. The Fermi satellite, which has two main instruments (Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT)), observed more than two thousand GRBs. The Fermi GBM catalogue contains GRB parameters (peak energy, spectral indices, intensity) estimated for both the total emission (fluence), and the emission during the interval of the peak flux. Our statistical analysis revealed an ordering of the spectra into a power law - Comptonized - smoothly broken power law - Band series. Using linear discriminant analysis we found a relationship between the spectral categories and the model independent physical data. We interpreted this result as a temporal variation of the spectrum during the outburst. We think that there is an significant synchrotron radiation in the GBM spectra because we found that the mean low-energy spectral index is in good correspondence with the canonical value of -2/3. We realized that this spectral index is smaller for the fluence spectra, which can be interpreted as a cooling effect appear in the later spectrum.
Backward integration method dependance on location in the main-belt
Radovic, Viktor
One of the main problems related to the research of asteroid families is estimation of their age. So far, a few methods for determination of the age of a family have been developed. Backward integration method (BIM) is probably the most accurate one and it could be applied only to younger families. The main idea behind the BIM is to numerically integrate the orbits of a dynamically stable family members into the past, in order to obtain the clustering of secular angles Omega and ?. This clustering should occur approximately around the moment of a family formation and from it we could estimate its age.Hence, it is interesting to examine how the minimum of a clustering of the secular angles depends on the age of the family. In previous work (Radovic, 2017) it is shown that BIM could be successfully applied to families not older than 18Myr, in the region of the Veritas family. Also, it is suggested that Yarkovsky effect and the location within the main-belt could significantly influence the clustering of the secular angles and possible application of the BIM. Therefore, this should be studied in more detail. In this work in order to examine the limitation of the BIM we divided the main-belt in distinct zones according to their secular frequency gradient. Then, for each zone we created a test family and numerically simulated its evolution in time. Using this simulations we estimated the limitations of the BIM and obtained results which show strong dependance on location especially for clustering of the longitude of perihelion.
Early solar system physical conditions and the origin: compatible models
Ragulskaya, Mariya
The origin and development of life on Earth was determined not only by conditions on the earth, but also by processes on the Sun and in the Solar System (SS). Significant factors for the early biosphere: 1. Radiation of the early Sun 2. Interdependence of the planets SS 3. Magnetic field of the Earth 4. Galactic cosmic rays (GCR).Young Sun (YS) had a circulation period of ~ 8 days, a mass of ~ 103% of the modern. The intensity of sporadic radiation exceeded the current one by several orders. The intense UV radiation of YS exerted a significant influence on the biosphere formation. The luminosity of YS was less by 30%. Then the surface of the Earth must be frozen. However, according to geological data, the temperature of the Earth's surface exceeded the modern. The paradox’s solution can lie in other reflection and absorption by the early Earth. The existence of biological films on the oceans’ surface is reported. They significantly altered the albedo of the planet and the composition of the atmosphere. Also, the early Earth could be closer to the Sun due to the migration of Jupiter and Saturn.The geomagnetic field (GF) protects the biosphere from intense cosmic rays. The formation of the GF occurred 2 billion years ago according to dynamo theory. According to paleomagnetic data there already was a magnetic field of the Earth 4.2 billion years ago. Its values were comparable with modern. The reason for the emergence of such a field could be the process of formation of the Earth-Moon system as well as tidal interaction of proto-Earth with migrating giant planets.The influence of space weather factors on the biosphere are observed to the present day. Saccharomyces cerevisiae strain Y-517 was studied by daily measurements in 2000-2012. During a minimum of solar activity, a significant contribution to the dynamics of cellular structures is made by GCR. At the maximum, the influence of solar activity and variations of the geomagnetic field are expressed.
Science literacy and scientific temper - lessons from India
Ramanujam, Niruj
India has a substantial and vibrant professional astronomy community, with strong links with mainstream astronomy communication organisations like amateur astronomy groups, planetaria etc. In addition, India also has a strong tradition of popular science movements mainly motivated by social justice aims, as well as informal teacher networks, that are predominantly semi-urban and rural. I will talk about the latter communities, and how their work on spreading science literacy and the uniquely Indian concept of 'scientific temper' aids the goals of critical inquiry, rationality and citizenship. In particular, I will talk about the astronomy component of these programs, specially in the context of my work both through the Public Outreach and Education Committee of the Astronomical Society of India, and at a personal level.
Developing Astronomy in Madagascar: the impact of the IAU support
Randriamanakoto, Zara
Madagascar is an island located in the southern part of Africa between the Indian Ocean and the Mozambique channel. Apart from being a future home to one of the African VLBI Network stations, the Red Island is also one of the eight african partner countries of South Africa, scheduled to host some of the future Square Kilometre Array (SKA) Phase II dishes. Since the involvment of the country in these gigantic projects, an interest in Astronomy has significantly increased among younger generation. In an effort to address these needs but especially to develop and advance Astronomy in Madagascar, an Astrophysics curriculum has been established at the Department of Physics of the University of Antananarivo and an organization known as Malagasy Astronomy & Space Science Association has been recently created. These are two notable actions among many others that have been taken. Throughout this journey, the IAU has regularly shown its support through the Office of Astronomy for Development, the Office for Astronomy Outreach and also its educational programme (the International School for Young Astronomers). In addition, graduate students and early researchers based in South Africa, who play an important role in shaping the future of Astronomy in Madagascar, have been awarded grants to present their works during IAU Symposia and meetings. This talk will report the current status of Astronomy in Madagascar and will give highlights on the role IAU has contributed in the development of Astronomy in the country. The expected impact by joining the union as a prospective member will also be discussed.
Growing Astronomy Public Outreach in Madagascar
Randriamanakoto, Zara
Founded in 2016, Malagasy Astronomy & Space Science or MASS is mainly a community of young professional astronomers and graduate students from Madagascar; though membership is also open to enthusiast amateurs. The creation of MASS stems for the need to promote Astronomy and Science education in the Red Island given the participation of the country to the large radio astronomy SKA project and the African VLBI Netowrk (AVN). One of the primary objectives of MASS, with the support from its IAU OAO National Outreach Contact, is to run regular outreach activities in the country. Since its launch, MASS has grown from simply using social media platforms to reach some of its targets into organizing annual primary/high school outreach events and Astro Quiz for graduate students. This paper reports such activities and also highlights the best practices being adopted to make these events successful. We will then discuss the challenges often encountered as a research astronomer devoted to public outreach. Finally, we will present the anticipated plan to bring Astronomy to more Malagasy people, as a pre-campain of the IAU centenary celebration.
Neutral Gas Phase Metallicities in Gas Associated with Dwarf Galaxies
Rao, Sandhya
Since small columns of metals are easily detected in absorption, observations of quasar absorption-line systems are powerful probes of metal abundances in foreground gas associated with galaxies. For predominantly neutral gas, with N(HI) > 1019 atoms cm-2, metallicities as low as [X/H] > -3 can be measured. At redshifts z < 1, the observed range of metallicities in neutral-gas systems mostly spans -1.5 < [X/H] < 0.5. These same systems have also been imaged with the aim of finding the associated galaxies. Although luminous galaxies are sometimes found to be along the quasar sightline, usually the best candidate for an absorbing galaxy must be a dwarf with luminosity < 0.1L*. Even in cases where luminous galaxies are found within an impact parameter of 100 kpc of the quasar sightline, it is virtually impossible to rule out the possibility that the sightline passes through gas in an unseen dwarf.In this contribution we discuss metallicity measurements in predominantly neutral-gas quasar absorption-line systems, which we conclude are strongly associated with dwarf galaxies. We also discuss a selection bias which indicates that the current estimate of the mean neutral-gas-phase metallicity may be over-estimated by up to a factor of 4.
Detached Eclipsing Binaries of B-type
Ratajczak, Milena
B-type stars in eclipsing binaries may serve as a tool for many stellar evolution aspects. Issues like convective core overshooting or mass determination of Beta Cephei variable stars can be tested with B-type stars in eclipsing binary systems. To achieve these goals, high resolution spectroscopy with high SNR and precise photometry are required, but since many of the targets are bright enough, the challenge is fair. The approach to examine both aspects of stellar evolution using observations of B-type stars obtained with a wide range of instruments, as well as BRITE-Constellation satellites, will be presented.
"Observations" of Simulated Dwarf Galaxies
Rathi, Shivangee
Dwarf galaxies are ideal systems to test the LambdaCDM cosmological theory for galaxy formation and evolution. Despite LambdaCDM's success in correctly reproducing large scale phenomena, it faces serious challenges on small scales, in the dwarf galaxy regime. One such persistent problem in the dwarf regime is the too-big-to-fail (TBTF) problem, which is an apparent mismatch between the expected number density of dwarf galaxies and their observed kinematics. We present our recent efforts to overcome these issues by bringing the analysis of dwarf galaxy simulations as close as possible to the observations. To this end, we construct synthetic radio datacubes for the simulated MoRIA suite of dwarf galaxies (Verbeke et al. 2015) and use observational tools such as GIPSY and 3DBarolo to analyze and interpret the HI kinematics of these simulated dwarfs. We show that this has consequences for the TBTF problem.We also reconstruct the star-formation histories (SFHs) of these simulated dwarfs based on their synthetic stellar Color-Magnitude diagrams using the techniques developed by the LCID team (Aparicio, A & Hidalgo, S. L. 2009). We compare this with the SFHs drawn directly from the simulations and discuss the effects of using different stellar evolution libraries. We emphasize the applicability and importance of using observational techniques to properly analyse simulated dwarf galaxies in order to robustly and reliably test LambdaCDM.
An Affordable Remotely Controlled Telescope for Research and Education
Ratzka, Thorsten
Viewing with a telescope objects that remain invisible to the naked eye is a fascination that not only astrophysicists share. Telescopic work naturally sparks the interest in basic research, but also in engineering sciences and informatics. A major challenge for teachers and tutors is the access to telescopes that can be operated in a professional way. Remote operation is a approach that has proven to be very efficient, but the number of telescopes is limited and the instruments (most often an imager) can not be changed._x005F At the Lustbühel Observatory in Graz (Austria) we successively developed a comparatively cheap infrastructure for the remote operation of our 50cm-telescope. Up to four different instruments can be mounted at the same time and switching between, e.g., imaging and spectroscopy only takes minutes. A camera inside the dome provides a view of the telescope and dome movements. Two all-sky cameras monitor the sky. Sensors measure the weather and sky conditions._x005F The telescope serves us well for our astrophysics research, plays an important role in the education of our students, and is a highlight of our public outreach events. While students very often prefer to operate the telescope from the control room, scientific programs can be performed from any office with internet access. During public demonstrations, the instrument control software and the obtained data can be shown side by side with the moving telescope and the sky above the observatory._x005F Our concept of combining a small-size telescope with a low-cost remote access was recently adapted to our "Ballistische Messkammer" and could be easily deployed on various sites, either with existing computer-controlled telescopes or with affordable new telescopes. The sites can be chosen with respect to their observing conditions and the already available infrastructure. The local and especially the remote users would benefit from a large freedom in developing educational and scientific programmes.
AGB star atmospheres modeling, as feedback to stellar evolutionary and galaxy models
Rau, Gioia
The chemical enrichment of the Universe is considerably affected by the contributions of Asymptotic Giant Branch (AGB) stars. These objects produce in their atmospheres heavy chemical elements, molecules, and dust, which, through the mass loss provided via their stellar winds, are placed into the interstellar medium. This talk will explore the modeling of cool, evolved stars, using ground-based interferometric facilities, and will introduce the capabilities of HST, and of future instruments onboard JWST.First, we will present our investigation of the O-rich AGB star R Peg in the near-IR with VLTI/GRAVITY (Wittkowski, Rau, et al., in prep.). We verified at different epochs the model-predicted variability of the visibility spectra, using CODEX model atmospheres for comparison with the observations. Our results, showing an anti-correlation between continuum radius and visual lightcurve, are consistent with 1D CODEX dynamic model atmosphere predictions.Second, following Rau et al. (2017), we present preliminary results on modeling with the grid of DARWIN dynamic model atmospheres, the atmosphere of V Oph, observed with VLTI/MIDI data, the (so-far) only known C-rich AGB star showing interferometric variability (Ohnaka et al. 2007). The comparison with the multi-shell model parameters by Ohnaka (2007) will provide additional constraints on C-rich AGB stars outer atmospheric composition. We will also introduce the capabilities of VLTI/MATISSE in advancing this work.Our work aims also to give feedback to stellar evolutionary models by comparison of our results to the evolutionary tracks by Marigo et al. (2013), to constrain stellar masses, C/O ratios, and ages.
JWST/NIRSpec MOS observations of massive galaxy clusters
Rawle, Timothy
Galaxy clusters are the largest gravitationally bound systems in the Universe, and hence offer a crucial laboratory to probe environmental effects on galaxy formation. At the same time, massive clusters act as powerful lenses, magnifying background objects and yielding a clearer view of otherwise faint galaxies at high redshift.Recent years have seen extensive Hubble imaging of massive galaxy clusters, particularly with programs such as CLASH, RELICS and the Frontier Fields. The next step will be to obtain spectroscopic information across these fields, ideally reaching a comparable depth. JWST/NIRSpec will provide a unique configurable MOS in space, allowing the selection and efficient observation of up to 100 targets chosen from both cluster field science cases. Furthermore, the ~3x3 arcmin field-of-view is ideally matched to the on-sky extent of intermediate-redshift (z~0.4) massive clusters.Here we discuss the practicalities, efficiency and limitations of using the NIRSpec MOS to enhance the current generation of Hubble studies of massive galaxy clusters.
Vortex stretching in self-gravitating protoplanetary discs
Regaly, Zsolt
Horseshoe-shaped brightness asymmetries of several transitional discs are thought to be caused by large-scale anticyclonic vortices. This vortices can efficiently collect dust particles, therefore they can play a major role in planet formation. Former studies suggest that the disc self-gravity weakens vortices formed at the edge of the gap opened by a massive planet in discs whose masses are relatively large, e.g. being in the range of 0.01 = Mdisc/M* = 0.1. In my talk, i present our investigation on the role of disc's self-gravity in the evolution of large-scale vortices excited at discs' dead zone outer edge. We performed our study by means of 2D numerical hydrodynamical simulations taking into account the disc's self-gravity in a locally isothermal approximation. Interestingly, vortices are found to be strongly affected by the disc's own gravitational field even for low mass discs, Mdisc = 0.005M* (Q<=50 initially) for which case the effect of disc's self-gravity was thought to be negligible. As a result of this azimuthal stretching, vortices have weaker azimuthal density contrasts and prone to decay faster than in non-self-gravitating discs. The vortex stretching can be explained by the combined action of a non-vanishing gravitational torque caused by the vortex itself, and the Keplerian shear of the disc. Based on our results, we conclude that the formation of long-lasting vortices requires a relatively small disc-to-star mass ratios being less than 0.5 percent and low disc viscosity. We also conclude that a former scenario in which a gravitationally stable disc fragments inside vortices, can not be a plausible pathway to planet formation, because of the vortex stretching tends to decrease the density enhancement at the vortex centre before fragmentation occurs.
Intelligent solutions for astronomical space instrumentation
Reimers, Christian
Scientific space missions for astrophysical purposes include complex instruments themselves again containing often several interacting computers dedicated to specific tasks. Aside from system control and communication, acquisition, guiding, sophisticated data handling and compression are key components to maximize the scientific data quality. The contribution of the University of Vienna is to develop low- and high-level applications for the logical units on-board and their operation. Each mission is different and therefore software frameworks, common standards, modular approaches and verification and qualification processes are used to develop the applications in short time with maximal product assurance. We present an insight into current projects and give an outlook on future developments.
Degradation process in TSI radiometers due to UV radiation
Remesal Oliva, Alberto
The degradation of the on-orbit TSI radiometer detectors must be studied on ground to understand the evolution of the irradiance data that we measure. Between the different processes that might induce degradation, UV radiation is most likely one of the most significant contributors. In order to estimate the effect of this radiation on the black paints applied to the radiometer detectors, we simulate with a Hg-Xe lamp the UV radiation that would hit on the detectors in a full life-time mission.We performed this experiment in two different coatings that might be used in future missions. The first one is a sprayable Carbon Nanotubes coating from Surrey NanoSystems and the second one is a glossy silicon base black paint.We study the reflectance of these detectors before and after the experiment, we evaluate the consequences of the radiation and estimate the degradation.
The Period-Luminosity Relations of RSGs in the M31 and M33
Ren, Yi
Previous studies have initially identified a number of Red Supergiant(RSG) candidates in M31 and M33.There are 437 candidates in M31 and 749 candidates in M33. For 365 RSG candidates in M31 and 655 RSG candidates in M33,they are further confirmed by color-magnitude diagrams (CMDs) to exclude the pollution of Asymptotic Giant Branch stars (AGBs) especially high luminosity AGBs. However, CMDs show that all RSG candidates from previous studies are not contaminated by AGBs.Finally,437 RSG candidates in M31 and 749 RSG candidates in M33 have been confirmed as RSGs. From the time-series photometric observations by the Palomar Transient Factory which cover nearly 2000 days, the period and amplitude of light variation are analyzed carefully using the methods of GLS ,PDM and WWZ.?According to the properties of light variation, these RSGs are classified into three categories: (1) 48 objects with semi-regular variation in M31 and 35 objects with semi-regular variation in M33,(2) 13 objects with Long Secondary Period (LSP) in M31 and 10 objects with LSP in M33,(3) others with too complex variation to get certain period or can’t ?be determined with reasonable accuracy because of the lack of data.For the semi-regular variables, the period-luminosity relation is analyzed in the visual, near-infrared and mid-infrared bands. It is found that the P-L relation is tight in the infrared bands such as the 2MASS JHKs bands.Meanwhile, the inhomogeneous extinction may cause the P-L relation to be relatively sparse in the R band. Finally,the results are compared with others P-L relationships for RSGs which in SMC,LMC and the Milky Way.
Stellar properties of dwarf galaxies and their connections with the Milky Way halo
Revaz, Yves
In this talk, relying on recent cosmological zoom-in chemo-dynamical simulations, I will describe the stellar properties of 27 dwarf galaxies emerging from a LCDM framework. In this context, I will show how, in addition to the galaxy global properties, the model galaxy_x005F velocity dispersion profiles, half-light radii, star formation histories, metallicity distributions, and [Mg/Fe] abundance ratios fit the observations with a level of details never achieved before. The formation and sustainability of the metallicity gradients and kinetically distinct stellar populations will also be discussed._x005F Those new models demonstrate that there is no missing satellite problem. In addition, they show that the majority of dwarf galaxies do not necessary require a strong interaction with a host Milky Way like galaxy._x005F However, dwarf galaxies with complex star formation histories like Carina and Fornax are much more difficult to reproduce. Those systems are often believed to result from an interaction with the Milky Way. I will show that when such interaction is taken into account in our high resolution simulations through ram pressure stripping, a much more complex reality appears.
Internal kinematics of blue-cored early-type dwarf galaxies in the Virgo cluster
Rey, Soo-Chang
Early-type dwarf galaxy (ETDG), the most abundant galaxy type in cluster, have been recently shown to exhibit a wide variety in their properties. Particularly, the presence of blue cores in some ETDGs supports the scenario of late-type galaxy infall and subsequent transformation into red, quiescent ETDGs. While several transformation mechanisms for these ETDGs within cluster environment have been proposed, all these processes are able to explain only some of the observational properties of ETDGs. In this context, internal kinematic properties of blue-cored ETDGs provide the most crucial evidence to discriminate different processes for the formation of these galaxies. We present a kinematic analysis of two blue-cored ETDGs in the Virgo cluster based on long-slit data obtained from Gemini Multi-Object Spectrographs (GMOS) observations. We found that the observed galaxies exhibit kinematically decoupled or disturbed components in the velocity profile. We also found that these galaxies are structurally compatible with low surface brightness component of blue compact dwarf galaxies. We suggest that a part of blue-cored ETDGs in the Virgo cluster were formed through galaxy merger in low density environment such as galaxy group or outskirt of the cluster, and then were quenched by subsequent effects within cluster environment.
NOC activities at France
Reylé, Céline
The poster present the NOC activities at France
Chemical Tracers in Proto-Brown Dwarfs – Observations and Modelling
Riaz, Basmah
Brown dwarfs bridge the gap between Solar-type stars and giant planets and share characteristics with both. This makes them interesting cases to study the analogies in the early formation and evolutionary stages with the proto-Suns and proto-planets. We have conducted the first substantial molecular line survey to study the chemistry in early-stage Class 0/I proto-brown dwarfs. Observations with the IRAM 30m telescope have confirmed detection in 16 molecular species. We have derived self-consistent physical+chemical models that can reproduce the observed molecular line emission and provide a first-order approximation to the internal structure of the proto-brown dwarfs. Results indicate that the species HCN, CS, DCO+, DCN, and N2D+ can trace the high-density emission towards the inner protoplanetary disk and can reveal the small-scale structures in the proto-brown dwarfs, whereas the HCO+, HNC, and CO molecules are severely depleted from the gas phase in the inner, dense regions. We find an enhanced abundance for HNC compared to HCN, which suggests that the chemistry of the nitrogen-bearing species is dominated by kinetic temperature gradients. The molecular abundances for the proto-brown dwarfs have been compared with Class 0/I protostars, covering a range of ~0.1 – 20 Lsun in the bolometric luminosities. We find a decline in the HCO+, HCN, and H2CO abundances with decreasing luminosities, while the species CS, CO, HNC, and CN are nearly constant and show no particular trend with the bolometric luminosity. There is a large spread of ~2 orders of magnitude in the molecular abundances for the proto-brown dwarfs, which reflects the source to source variations in their chemical composition and internal structure. We will discuss the similarities in the chemical structure of the proto-brown dwarfs with pre-stellar cores, protostars, and proto-planets, and the development of our physical+chemical models to understand the chemical evolution in proto-brown dwarfs.
Development of PALOP Knowledge in Radioastronomy
Ribeiro, Valerio A. R. M.
DOPPLER (DevelOpment of PaloP knowLEdge in Radioastronomy) is a recently awarded project through the Aga Khan Development Network and the Portuguese Science and Technology Foundation to foster ongoing and forge new collaborations in Mozambique. DOPPLER is born from ENGAGE SKA - a fully funded Portuguese Roadmap of Research Infrastructures of Strategic Relevance and leading the Portuguese efforts to join the SKA Organisation. ENGAGE SKA includes an International Cooperation and Science for Development workpackage which promotes ongoing endeavours, in particular with advanced training in areas of biodiversity, food security, resource management and radio astronomy. Through these advanced trainings DOPPLER will be in recognition of a number UNESCO sustainable development goals (4, 5, 7, 8, 9, 13, and 17). Along with advanced training we have an outreach team that has worked closely with a number of local communities including where the Square Kilometre Array South Africa project identified potential site locations.
The geometric distance and binary orbit of the HMXB PSR B1259-63
Ribó, Marc
The high-mass gamma-ray binary system PSR B1259-63/LS 2883 consists of a pulsar in a 3.4-year orbit with a high-mass Oe-type companion star. Every periastron passage, multi-wavelength flaring extending up to GeV and TeV energies is seen as the pulsar moves through the disk of material surrounding its O9.5Ve stellar companion. Using the Australian Long Baseline Array we carried out a 4.4-year astrometric campaign, fully sampling the binary orbit. We measured the parallax, inclination angle of the binary orbit, and the sense of the pulsar orbit on the plane of the sky. Together with high-precision pulsar timing results, all the astrometric and orbital parameters of the system are now fully determined. In this poster, we will present our results, which are consistent with the system having formed in the Cen OB1 association and receiving a modest velocity kick in the natal supernova. We also placed constraints on the mass of the stellar companion, and confirmed that the X-ray-emitting knot seen moving away from the system Is directed along the orbital semi-major axis, towards apastron.
Probing heavily obscured AGNs combining Herschel and Chandra datasets at z~2 in the COSMOS field
Riguccini, Laurie
We study the X-ray properties of 108 Dust-Obscured Galaxies (DOGs; F24/FR > 982) in the COSMOS field, all of which are detected in at least three far-infrared bands with the Herschel Observatory. Out of the entire sample, 22 are individually detected in the hard X-ray band by the Chandra COSMOS Legacy survey, allowing us to classify them as Active Galactic Nuclei (AGN). We find that 6 DOGs out of the 22 X-ray detected are Compton Thick candidates and that 15 are moderately obscured AGNs. Additionally, we estimate AGN contributions (>20%) to the IR luminosity (8-1000µm rest-frame) for 19 DOGs based on SED decomposition using Spitzer/MIPS 24µm and the five Herschel bands (100-500 µm). Only 7 of these are detected in X-rays, emphasizing the need for multi-wavelength analysis to obtain a complete census of the AGN population. We performed a X-ray stacking analysis for the 86 undetected DOGs. We find that the fraction of AGNs in the DOG population increases with 24µm flux and that it is higher than that of the general 24µm population. This motivates the combined use of X-ray and far-IR surveys to successfully probe a wider population of AGNs, particularly for the most obscured ones. Most of the AGN-DOGs are populating the main sequence of star-forming galaxies or below, while most of the star forming DOGs are still in the starburst regime. Our results support the evolutionary scenario where DOG is a rapid phase of galaxy evolution between gas-rich submillimeter galaxies and red, massive quiescent galaxies.
Baryonic feedback in scalar-field dark matter halos: dwarf galaxies as cosmological probes to constrain the nature of dark matter
Rindler-Daller, Tanja
The standard cold dark matter (CDM) paradigm has been challenged over the years, where discrepancies have been found between the predictions of CDM simulations and observations of galaxies, particularly dwarf galaxies: the cusp/core problem of dark matter density profiles, the predicted overabundance of Local Group satellite galaxies, and the too-big-too-fail problem. Scenarios have been invoked to resolve these problems through the additional effectsof baryonic physics, but they generally require strong feedback processes which may not be sufficient in all cases. Meanwhile, attempts to detect the standard CDM particle candidate WIMPs have so far failed. As a result, interest in alternative dark matter has increased, to resolve the small-scale structure issues of standard CDM while retaining its successes on large scales. Dwarf galaxies constitute a powerful probe to study such alternative models.We consider a class of models - scalar-field dark matter (SFDM), where all of the dark matter is comprised of ultralight bosons (m>~10^(-22)eV). SFDM dynamics differs from standard CDM on small scales, suppressing structure formation below a characteristic scale, thereby providing a possible cure to the above problems. This introduces novel effects with observable consequences, including the flattening of central halo density profiles. However, baryonic physics affects the observational constraints on dark matter particle parameters, and that impact depends upon galaxy formation history and halo mass. In this work, we thus consider the consequences of coupling SFDM to thebaryonic component, including baryonic dissipation and feedback. These effects will be addressed by a hierarchy of methods, from analytical models, to 1D numerical hydrodynamics, to simulationswhich incorporate a 2-phase interstellar medium and evolving chemical abundances and stellar populations. The implications of these results for SFDM as an alternative to standard CDM will be assessed.
Statistical analysis of polarized dust emission in the environment of Planck Galactic cold clumps
Ristorcelli, Isabelle
Magnetic fields are considered one of the key physical agents that regulate star formation, but their actual role in the formation and evolution of dense cores remains an open question. Polarized dust continuum emission is particularly well-suited to probe the magnetic field structure in the dense, cold interstellar medium. Such observations also provide tight constraints on the efficiency of dust alignment along magnetic field lines, which are needed to properly infer the magnetic field properties from observations. With the Planck all-sky survey of dust submillimetre emission in intensity and polarization, we can investigate intermediate spatial scales in the hierarchy of star formation, between global molecular cloud measurements and studies of individual prestellar cores. Planck further enables a statistical analysis of the polarization properties of clumps. We have recently built the first all-sky catalogue of Galactic Cold Clumps (PGCC, Planck collaboration XXVIII 2016), a fraction of which we have studied in detail with our Herschel Key Programme ‘Galactic Cold Cores’. The sources cover a broad range in physical properties and correspond to different evolutionary stages in the star formation process, from quiescent starless clumps and nearby cores to young protostellar objects. We present new results from our statistical analysis of the polarized 353GHz Planck data for the PGCC sources. We have in particular studied the variation of the polarization fraction as a function of the column density and of the polarization angle dispersion function. We have also analysed the magnetic field morphology and compared it to structures (filaments, striations) traced at higher resolution with Herschel in the environment of PGCC sources, searching for evolutionary signatures. Finally, we will discuss our results in the context of MHD simulations that include radiative transfer and the dust radiative torque alignment mechanism.
Kinematics of lensed galaxies with a 3D Bayesian model
Rizzo, Francesca
In the last decade observations of high-redshift galaxies, based on Integral Field Spectrographs (IFS) or interferometric data gave access to the resolved spatial information on the kinematics of ionized and molecular gas. However, although the number of high-z studies has been increasing in the last decades, the interpretation of the kinematic properties of the young galaxies is still controversial. This is mainly due to the low spatial resolution and low signal-to-noise ratio that make it difficult to derive reliable velocity and dispersion maps. The two limitations that characterise the observations of high-z galaxies are partly overcome by targeting lensed galaxies. The strong gravitational lensing offers the opportunity to study high redshift galaxies at much higher physical resolution. Furthermore, the magnifying power of gravitational lensing offers the possibility to study galaxies in the low mass range, ~108-109 M•, which is not achievable by the unlensed surveys.In this talk I will present a new 3D gravitational lens modelling code that simultaneously derives the lensing parameters and the rotation curves of lensed galaxies, using a modified 3D tilted ring model. This software takes advantage of the redundant information contained in the lensed data and it recovers reliable kinematics from a variety of different instruments including the new-generation IFUs, JWST and ALMA. I will describe the structure of the main algorithm and show that it performs much better than the standard 2D technique usually used for the extraction of the kinematic maps of high-z galaxies. Finally, I will show some applications of this software on a sample of lensed galaxies aimed at deriving the Tully-Fisher relation and their angular momentum distribution. I will show how the correlation between their angular momentum content and other physical properties can give fundamental clues on the evolution of the star-forming discs.
Ultraluminous X-ray sources as the brightest HMXBs
Roberts, Tim
The link between ultraluminous X-ray sources (ULXs) and high mass X-ray binaries (HMXBs) is now well-established, with the majority of observed ULXs thought to constitute a compact object (black hole or neutron star) feeding from a young and massive star. We present a new catalogue of 403 ULXs and 1064 less luminous point X-ray sources associated with nearby galaxies, derived from the 3XMM-DR4 catalogue, the majority of which we expect to be HMXBs. The applications of this catalogue are numerous: for example the identification of high amplitude long-term variability in ULXs, a possible indicator of pulsar ULXs transiting in and out of the propeller state; identifying new IMBH candidates from the most luminous ULXs; and extending detailed spectral-temporal studies from bright ULXs down to objects in the Eddington threshold regime (~1039 erg s-1). We can also begin to systematically examine the properties of HMXBs in nearby star-forming galaxies that possess sub-ULX luminosities, where large datasets exist. We present early results from stacking analyses that seek to do this, and argue why understanding these objects is important for understanding galaxy evolution at high redshifts.
The Arecibo 305-Meter Telescope: A Long History of Reinvention and Astronomical Discoveries
Robishaw, Timothy
This year marks 60 years since the inception of the 1000-foot Arecibo radio dish. During this time, the world's largest Radio/Radar telescope has reinvented itself several times, always stretching the limits of its discovery space. Even in 1958, the initial project study led by William E. Gordon included a wide range of cutting-edge disciplines where a huge spherical dish could contribute beyond its primary goal as an ionospheric radar back-scatter system. Three major upgrades have since kept Arecibo at the forefront of astronomical research. Among its many accomplishments, the giant dish has detected the first extrasolar planetary system, identified ice in the polar craters of Mercury, and contributed to the confirmation of the general theory of relativity, which led to the award of the 1993 Nobel Prize in Physics. Here, we trace the path that has led this instrument through its amazing achievements, has seen its survival despite natural disasters and other challenges, and is now carrying it towards a fruitful future.
The evolution code PEGASE.3 for distant radiogalaxies with JWST
Rocca Volmerange, Pr Brigitte
New observations (images and spectra) of distant radio galaxies with the satellite JWST on its unique wavelength coverage (visible to mid-infrared) and resolutions will require galaxy evolution models with dust attenuation and emission. The code PEGASE.3 (Fioc & Rocca-Volmerange, www2.iap.fr/pegase, on submission process) is specifically adapted to interpret JWST data, in particular in the puzzling 5 to 20 microns domain. Multiple aims are to identify stochastic effects on dust emission as well as to disentangle the various components from hot dust, star-formation zones, diffuse ISM and AGN torus, in possible relation with the growth of super massive black holes.
Filter Profile Service.
Rodrigo, Carlos
During the last years, and with the advent of several important photometric surveys, many astronomical studies are taking an increasingly multi-wavelength approach. But to combine photometric data coming from different sources it is necessary that these measures are described and characterized in sufficient detail to allow for the conversion to compatible flux density and spectral energy units.In the Spanish Virtual Observatory we maintain the "Filter Profile Service"(http://svo2.cab.inta-csic.es/theory/fps/), that provides standardized information, including transmission curves and calibration, about more than 4000 astronomical filters. The service is designed to be compliant to the Virtual Observatory Photometry Data Model and all the information is provided both as a web portal and VO services so that other services and applications can access the relevant properties of a filter in a simple way.In particular, all this information is used by VOSA (Virtual Observatory SED Analyzer) to analyze observational spectral energy distributions comparing them with the synthetic photometry corresponding to different collections of theoretical spectra or observational templates.In this presentation I will describe the main functionalities of theservice and its usage by Virtual Observatory tools like VOSA or Clusterix.
The evolution of large scale magnetic fields in spiral galaxies
Rodrigues, Luiz Felippe Santiago
We investigate how the large scale magnetic fields in the discs of spiral galaxies evolve through cosmic time. To do this, we couple the galaxy properties computed by a semi-analytic model of galaxy formation to the mean field dynamo equations. These are solved numerically as a function of time and galactocentric radius for a thin disc using the no-z approximation, with imposed axial symmetry, and the dynamical quenching non-linearity. A simple prescription for the evolution of the random (small-scale) magnetic field component and its relation with the mean (large-scale) component is adopted. This allows us to compute radial and time dependent properties of the interstellar medium of discs for a statistical sample of galaxies from z~7 until the present. We compute the distribution of the typical magnetic field strength at different redshifts and the dependence of these on galaxy mass. We examine the evolution of the growth rate of the mean disc magnetic fields of galaxies and discuss the steady state assumption. Finally, we analyse what is the sensitivity of our results to specific assumptions and to the galaxy formation model.
Coorbital evolution during the primordial migration in systems of natural satellites. Implications for Janus and Epimetheus
Rodriguez, Adrian
We analyze the orbital motion of two natural satellites initially in coorbital con g-uration with a third (guiding) migrating satellite embedded into a circumplanetary gasdisk. Through the solution of the exact equations of motion, including the effect of thedisk and the mutual gravitational perturbations, we investigate the orbital behaviorof the system after the guiding satellite crosses its Roche limit with the central planetdue to the induced orbital decay. The application is done for a system consideringSaturn as the central planet and Janus and Epimetheus as being the two coorbitals.By performing a large set of numerical simulations, varying the mass and the initialdistance of the main satellite, we compute the nal orbital con guration of Janus andEpimetheus and show that the horseshoe mutual coorbital motion appears as a naturaloutcome in the simulations.
Models of Very High Energy Emission of X-rays Binaries: Numerical GRMHD Simulations of Magnetic Reconnection Events and Radiative Transfer/Particle Calculations.
Rodriguez-Ramirez, Juan Carlos
Leptonic and hadronic non-thermal processes have been considered to model the very high energy (VHE) component of the emission spectrum of X-ray binaries. However, the hadronic models are still poorly developed. In this work we consider particle acceleration produced by magnetic reconnection in the core region of accreting black holes (BH) to numerically calculate the resulting VHE emission produced due to hadronic and leptonic processes. We first perform general relativistic magnetohydrodynamical (GRMHD) simulations of BH accretion disks seeking for strong magnetic reconnection events, and chose the appropriate environment profiles for our emission calculations. We then perform leptonic radiative transfer calculations on the chosen background snaptshots in order to obtain the photon field that will be the target for photo-hadronic interactions. Then, we inject high energy protons (according to the characteristics of the plasma in the reconnection regions) and compute photon fluxes stemming from the interactions of the injected protons with the background photon and magnetic fields (using the CRPropa3 code). Finally, we obtain the resulting spectral energy distributions and discuss the characteristics of their corresponding accretion disks sources and hosting X-ray binary systems.
A New Concept for the Asteroid Taxonomy with 3D Photometric Colors and its Application to Asteroid Families
Roh, Dong-Goo
Taxonomic classification of asteroids has been mostly based on spectroscopic observations with wavelengths spanning from the visible to the near-infrared. We measured VIS-NIR spectra of ~2,500 asteroids since the 1970s, and the Sloan Digital Sky Survey (SDSS) 4th Moving Object Catalog (MOC 4) was released with ~4×105 measurements of asteroid positions and colors in the early 2000s. A decade later, DeMeo and Carry (2013) made use of ~400 spectra to apply their taxonomy to ~1×105 MOC 4 asteroids. However, asteroids in their 2-dimensional parameter space (e.g., slope vs. i-z reflectance) were seen as a continuous distribution of clouds of data points and their boundaries are rather ambiguously defined. Therefore, we introduce an improved system of asteroid taxonomy. This approach is simply represented by a triplet of SDSS colors. The centers of each taxonomic class are determined mathematically and the class boundaries are statistically established. We apply our scheme to MOC 4 calibrated with VIS-NIR reflectance spectra of DeMeo and Carry. We successfully separate seven different taxonomy classifications: C, D, K, L, S, V, and X, with which we have a relatively sufficient number of spectroscopic datasets. We applied the newly defined taxonomic types to the SDSS MOC 4 in order to investigate the three dimensional color distribution of asteroids in the proper element space. Our preliminary plots coded with seven different colors reveal more detailed picture of asteroid families across the main-belt.
Henize 2-10: A Dwarf Irregular with a Massive Black Hole or a Supernova Remnant?
Rohr, Eric
Based on radio and X-ray observations, it has been suggested (Reines et al 2011) that a massive black hole resides in the low mass dwarf irregular galaxy Henize 2-10. This unusual finding has important implications for the formation of massive black holes in the early Universe since Henize 2-10 can be viewed as a low redshift analog to the first high-z galaxies. We present long-slit HST STIS spectra that pass over the suggested position of the massive black hole, marked by a compact (<3x1pc) 1 mJy radio source observed at 1.4 GHz by the LBA (Reines and Deller 2012). While recent MUSE-IFU spectroscopic observations showed no change in ionization near the radio source, calling into question the existence of an accreting massive black hole (Cresci et al 2017), our higher spatial resolution observations reveal a compact region of significantly lower ionization, with no velocity gradient across 0.1 arcseconds. Preliminary analysis suggests this emission, and the radio emission, are both consistent with a luminous supernova remnant. These observations weaken the case for a massive black hole in Henize 2-10.
Testing how massive stars evolve, loose mass, and collapse at low metal content
Rojas Montes, Eliceth Y.
In order to test massive star evolution above 25 Solar masses, we performspectral analysis on a sample of massive stars in the Small Magallenic Cloud that includes both O stars as well as more evolved Wolf-Rayet stars.We present a grid of non-LTE stellar atmospheres that has been calculatedusing the CMFGEN code, in order to have a systematic and homogeneous approach. We obtain stellar and wind parameters for O stars, spectral typesranging from O2 to O6, and the complete sample of known Wolf-Rayetstars. We discuss the evolutionary status of both the O and WR stars andthe links between them, as well as the most likely evolutionary pathtowards Black Hole formation in a low metallicity environment, includingtesting theoretical predictions for mass-loss rates at low metallicities.
An assessment of the MW thick disk star formation rate behavior with Galactocentric distance
Rojas-Arriagada, Álvaro
The chemical patterns of thin/thick disk stars (low- and high-alpha sequences) in the [A/Fe] vs [Fe/H] plane are quite variable with Galactocentric distance, revealing that the disk system might be a complex mix of stellar populations, of different nature and origins, depending of their radial location.The star formation history of a stellar system leave imprints in its observed chemical patterns; the MDF, and in particular, the metallicity position of the so called "knee", the turndown of its sequence in the [A/Fe] vs [Fe/H] plane. The knee position is important because it represents a proxy for the star formation rate (SFR) of the system. We present here results obtained with the Gaia-ESO survey arguing for a null variation of the knee position with Galactocentric distance for R_GC<9.5 kpc. We also discuss the seemingly different position of the thick disk knee with respect to that of the bulge metal-poor population. As Gaia parallaxes and proper motions might become available for our thick disk sample next April, we will investigate if the constancy of the SFR with Galactocentric radius change while considering guiding radius, or in general, dynamics, as obtained from orbit integration in a standard Galactic potential.
High-resolution VLBI observations of Active Galactic Nuclei
Ros, Eduardo
Active Galactic Nuclei are probed at sub-parsec scales by very-long-baseline interferometry (VLBI) at the highest resolutions. These are reached by the RadioAstron program with baselines larger than the Earth with a radio telescope in orbit; and also observing at high frequencies with the Global mm-VLBI Array (GMVA, 86 GHz) and the Event Horizon Telescope (EHT, 230 GHz). For the latter, the inclusion of beam formed ALMA since April 2017 provides enhanced sensitivity and imaging fidelity. In this poster we will show selected results of our observations of the innermost regions of the radio galaxies NGC 1052 and Centaurus A, and blazars such as 4C+01.28, among others.
Analyzing the long term variability of the Double Periodic Variable HD50526
Rosales Guzmán, Jaime Andrés
HD 50526 is a Double Periodic Variable (DPV) characterized by an long photometric cycle of 190.584 \pm 0.089 days that lasting on average of 28 time the orbital period. We have determined an improved orbital period of 6.701 \pm 0.001 days using the ASAS light curve. Also we performed a second photometric analysis with PanSTARRS-1 shown a new short period 22.096 \pm 0.1 d and a long period 137 \pm 10 d, possibly related to highly activity on the surface of the star caused by great changes into of stellar dynamo. We present a detailed spectroscopic study of the DPV HD 50526 Cen based on high-resolution with different spectrograph from years 2008 to 2015. The spectra of each component were disentangled with a method that is quite good for separating the absorption-lines widths of both stellar components González \& Levato (2006). The features of the donor star were modeled using the SPECTRUM code, and we found a little evolved donor star of T= 9500 $\pm$ 250 K, log$g$ = 2.5 $\pm$ 0.5, V$_{turb}$ = 0.0 km s$^{-1}$, Vsini = 60.5 km s$^{-1}$. We classified the donor star as spectral type A0I, while that for the companion we estimated a m$_{g}$ = 5.86 $\pm$ 0.02 m$_{\odot}$, T$_{g}$ 13500 K $\pm$ 500 K with a concave and geometrically thick disc and the system is seen under inclination 63º.0 \pm 0.2º. We must empathize that the research is not complete and we must continue for obtain the fundamental parameters and constraint the nature of the long cycle._x005F
Evolutionary process of the Double periodic Variable: V495 Centauri
Rosales Guzmán, Jaime Andrés
We presented a simple model for the Double Periodic Variable (DPV) V495 Cen, which evolve a binary system of intermediate mass, including an accretion disc. The theoretical model begins at the zero-age main sequence with rotation for both stars. We started the model using parameters obtained from Rosales et al. (2018), adopting an initial orbital period 4.0 d and and initial mass for the primary component (donor) $m_{i,d} = 3.45$ $m_{\odot}$ and $m_{i,g}= 3.25$ $m_{\odot}$ for the gainer, with a metallicity associated to this type of DPV of z = 0.02. For this purpose we use the evolutionary code MESA, developed to calculate evolution of stars in a wide range of environments. We described each evolutionary stage of both components until that the donor reaches the core Helium depletion ($X_{He_{c}}$) as stop criterion. Also we offer a complementary analysis for understand how the second period is linked to mechanism based of cycles on magnetic dynamo into of the donor star called Applegate mechanism, that was proposed as an explanation for the DPV long cycles by Schleicher \& Mennickent (2017). Currently, the theoretical model is consistent with published results for V495 Cen and we discuss how our predictions can help to develop efficients theoretical models for DPV stars.
New insight into the coma of comet 2P/Encke: apparitions of 2013 and 2017
Rosenbush, Vera
We present new results of photometric, polarimetric, and spectroscopic observations of comet 2P/Encke performed at the 6-m telescope of the SAO RAS during apparitions of 2013 and 2017. We observed the comet through the narrow-band filters isolating dust continuum domains BC (blue) and RC (red) and the emission band of NH2 as well as with broad-band SED500, V, and r-sdss filters to provide the best images. The full filter set of Encke images shows different morphology of the coma and variations in its size and structure as a function of wavelength that yields insight into the chemistry of the coma.As in the case of comet 67P/Churyumov–Gerasimenko (Rosenbush et al. 2017, MNRAS469), we found that the near-nucleus area of comet Encke is redder and more polarized than the adjacent coma. The dust color gradually changed from 1.0m in the innermost coma to about 0.3m in the outer coma. At the same time, the corrected for gas contamination radial profiles of polarization showed that the polarization in the near-nucleus area was almost 12%, dropped sharply to 6% at the distance 3000 km, and then gradually increased with projected distance from the nucleus, reaching 12% at 12000 km. Such radial variations of polarization and color in both comets, dust-poor comet Encke and dust-rich comet 67P/C-G, suggest a change in the particle properties and, hence, in the mean scattering properties of the grains on a time-of-flight timescale. To calculate the light scattering properties of individual scattering particles, the Sh-matrix method (Petrov et al. 2012, JQSRT 113) was used. Our simulation allowed us to determine the microphysical parameters of the model particles and describe the observed changes in color and polarization.We will demonstrate results of observations of comet Encke and discuss the possible reasons of diversity and similarity of physical characteristics of gassy comet Encke and dusty comet 67P/C-G.
An insight into the low level accretion in Be/X-ray transients
Rouco Escorial, Alicia
I will present the results of several Be/X-ray transients (i.e., GRO J1750-237, 4U 0115+63, GRO J1008-57, GX 304-1, KS 1947+300) after the end of their outbursts when the sources are thought to transit to quiescence. Our monitoring campaigns are focused on studying low-level accretion processes onto the magnetized neutron stars (1x1012-1x1013 G) present in these systems. We find that some sources decay directly to quiescence, a few systems settle in a decaying low luminosity state during which very short (timescales of only a few days) enhanced accretion episodes occur, while several other systems always stay in an intermediate accretion-rate level with X-ray luminosities of 1034-1035 erg/s and never appear to reach quiescence. I will discuss these results in the context of physical processes that could produce the observed phenomena, such as low-level direct accretion onto the neutron star (e.g., due to leakage of matter to the surface or accretion through a cold disk), accretion down to the magnetospheric boundary, or emission associated with the propeller effect that might be active in some systems.
Impact of intergalactic environment on the radio-morphologies of Giant sources.
Roy, Rupak
Radio galaxies are the known most giant radio sources in the visible universe. Although, all of them have prominent jet like outflows, considerable differences among their jet activities as well as in their morphologies can be found in their radio-images. This eventually lead us to a wide classification scheme : FR-I, FR-II, GRG, DDRG, Wide-angle tail and S-shape sources. Jets are launched from the center, very near to the supermassive black hole (SMBH) of the host galaxy, so certainly jet activities are governed by the central SMBH. However at sufficient distance from the host, in the intergalactic medium the flow of jet material is also influenced by the ram-pressure of the environment. In this presentation we will discuss the Impact of intergalactic environment on the radio-morphologies of Giant sources on the basis of local galaxy population around them. For this purpose we have used the data from the radio surveys conducted by VLA and the optical data from SDSS survey.
The star formation relation in atomic hydrogen dominated dwarf galaxies
Roychowdhury, Sambit
Star forming dwarf irregular (dIrr) galaxies are the most numerous galaxies in the nearby Universe, closely resembling the first galaxies that formed. They represent a goldmine in our own backyard for studying the baryon cycle in the smallest galaxies. Recent large multi-wavelength surveys of the Local Volume has made it possible to study these galaxies in considerable detail.Atomic hydrogen (HI) remains the primary tracer of gas in these systems as CO, the tracer of molecular gas, become harder to detect due to a decrease in the CO-to-H2 ratio with decreasing metallicity. The atomic gas traces the total gas reservoir in dwarf irregulars - and consequently the whole ecosystem within which stars form.I will start with recent results from my studies using the Faint Irregular Galaxy GMRT Survey (FIGGS). I show that when one measures the star formation rates (SFRs) correctly after accounting for the stochasticity, one finds the same 'Kennicutt-Schmidt relation' between surface densities of gas and SFR within resolved sub-kpc sized regions - in both dIrrs and outskirts of spirals, and a more efficient one than previously believed. More importantly, the relation is consistent with models of star formation which take the effects of stellar and supernova feedback into account.The importance of feedback from earlier generations of stars is reiterated in my study where I extend the range of validity of the 'extended Schmidt law' to the lowest metallicity galaxies, by showing that dIrrs also follow the law.Finally I will present my recent efforts to model the full baryon cycle in the lowest (<20% solar) metallciity star forming dwarfs from the well-defined DustPedia sample, which has multi-wavelength coverage in 42 bands ranging from the ultraviolet to submillimeter. Adding resolved HI maps, and using SFR and dust properties derived from SED fits using a hierarchical Bayesian approach, I create a model of the gas-stars-dust cycle using the latest chemical evolution models.
Determination of the stellar atmospheric parameters using full spectrum fitting against model atmospheres.
Rubtsov, Evgeniy
We present a new technique implemented in IDL for determination of the parameters of the stellar atmospheres, based on PHOENIX and BT-Settl synthetic stellar spectra. The synthetic spectra provide wide coverage in the Teff, logg, [Fe/H], [a/H] parameter space over a wide wavelength range and allow to fit observed spectra of a vast majority of stars. Our procedure also determines radial velocities and star rotation rates, and it takes into account flux calibration imperfections by fitting a polynomial continuum. We can also exclude certain spectral features, which are not included in the models, such as emission lines (chromospheric emission in late-type stars or discs around Be stars). We perform the non-linear chi2 minimization with the Lavenberg-Marquardt method that is applied to the entire spectrum, with the exception of areas with peculiarities: emission lines, model shortcomings (incompleteness of the list of spectral lines for model calculation). The main advantage of our technique is the physically reasonable calibration of stellar atmospheric parameters. We present the comparative statistical analysis with spectral libraries ELODIE, INDO-US, MILES, UVES-POP and discuss prospective applications of our technique.
Decameter Type IV burst associated with a behind-the-limb CME observed on 7 November 2013
Rucker, Helmut O.
We report on the results of observations of a Type IV burst made by the URAN-2 radio telescope (Ukraine) in the frequency range 22 - 33 MHz. The burst is associated with a CME initiated by a behind-the-limb active region and was also observed by the NDA (France) in the frequency band 30 - 60 MHz. After analysis of the observational data obtained with the URAN-2, the NDA, the STEREO A and B, and SOHO, we come to the conclusion that the source of the Type IV burst is the core of a behind-the-limb CME. We conclude that the radio emission can escape the center of the CME core at a frequency of 60 MHz and originates from the periphery of the core at a frequency of 30 MHz that is due to occultation by the solar corona at the corresponding frequencies. We find plasma densities in these regions assuming the plasma mechanism of radio emission.We show that the frequency drift of the start of the type IV burst is governed by an expansion of the CME core. The Type III bursts that were observed against this Type IV burst are shown to be generated by fast electrons propagating through the CME core plasma. A Type II burst was registered at frequencies 44 - 64 MHz and 3 - 16 MHz and was radiated by a shock with velocities of about 1000 km/s and 800 km/s, respectively.
Retrieving the spatial properties of the sources of solar radio bursts using the UTR-2 radio telescope
Rucker, Helmut O.
We present the results of the first experiments on spatial localization of solar radio bursts sources using the UTR-2 radio telescope. In order to obtain spatial properties of the bursts sources the radio telescope has been reconfigured to operate as local short-base interferometer. Two perpendicular baselines of 674m long were used. For illustration of this method’s capability a complex powerful Type II burst associated with narrow CME ejected at around 11 UT on 31 May 2013 has been chosen.The Type II burst consisted of two successive parts of quite different appearance on the dynamic spectrum, and revealed band splitting, herring-bone and harmonic structures. It was found that the sources of separate “lanes” of split Type II bursts did not coincide, with higher frequency lane being located lower in the corona. This fact speaks in favor of the upstream and downstream model of band splitting of Type IIs.The linear velocities of the bursts sources were detected by three independent methods: from optical observations by SOHO and STEREO missions, by frequency drift rate and by spatial displacement of the source in the sky plane. The velocities obtained by two last methods gave rather close values while the velocity got from space-borne coronagraphs appeared to be roughly two times smaller. The sources of the Type II bursts elements were found to be of about 15 arcmin in size in average, with the smallest ones reaching as low as 10 arcmin. Such sizes provide the effective brightness temperatures of the Type II burst up to 2·1012K. The polarization data from URAN-2 radio telescope is also shown.
Circumstellar Molecular Maser Emission of AGB and Post-AGB Stars
Rudnitskij, Georgij
Results of long-term studies of circumstellar molecular maser emission of late-type giant and supergiant stars are reported. The observations have been carried out during several decades in the H2O line at a wavelength of 1.35 cm (22-meter telescope in Pushchino, Russia) and in the hydroxyl (OH) lines at 18 cm (Nancay radio telescope, France). A sample of ~70 AGB long-period variable stars has been monitored in the 1.35-cm H2O line in 1980-2018. It includes Mira-type stars (U Ori, RS Vir, U Her, R Cas,…) and semiregular variables (R Crt, RT Vir, W Hya, VX Sgr,…) We have traced H2O maser variations and found them to follow the optical brightness variations with a time delay of 0.3-0.4 stellar period. Some strong H2O flares were observed, which occur every 10 to 15 periods, probably due to long-term changes in the mass-loss rate; good examples are U Ori, U Her, and RS Vir. Especially spectacular flares were demonstrated by the semiregular star W Hya, when its H2O peak flux density reached several thousand janskys, while on the average it did not exceed 50-100 Jy. The model of shock excitation of the H2O maser in combination with stellar radiation pumping is discussed. The same sample of AGB stars was observed in the 18-cm OH lines. For 53 of them, the emission was detected in at least one of three OH lines (1612, 1665, or 1667 MHz). Circular and linear polarization of the maser emission was measured, yielding all four Stokes parameters. Features probably due to Zeeman splitting were detected in the OH line profiles of several stars. Estimated magnetic-field strengths in the maser sources are a few milligauss. In particular, we discuss the data of 2007-2018 on the OH emission of the unique symbiotic star V627 Cas (AS 501, AFGL 2999) displaying maser emission in three ground-sate OH lines 1612, 1665, and 1667 MHz, with remarkable redistribution with time of their relative intensities, as well the new data on the OH and H2O emission of the post-AGB star AI CMi.
Observations of H2O and OH masers in star-forming regions
Rudnitskij, Georgij
We report long-term observations of H2O and OH maser emission sources at wavelengths of 1.35 and 18 cm associated with star-forming regions. The observations were carried out, respectively, on the 22-metre radio telescope of the Pushchino Radio Astronomy Observatory, Russia, and on the radio telescope of the Nançay Radio Astronomy Station, France._x005F The sample includes about 150 sources. Some of them are well-known masers, such as Ori A, W43M3, W51, W75N. Strong quasi-periodic flares of maser emission have been observed. We invoke, where available, interferometric data on the sources and trace the fate of individual maser features, the variations of their flux densities and radial velocities. In particular, the velocity drift of some features on a timescale of several years was observed. Several sources (in particular, G25.65+1.05, IRAS 16293-2422, Cep A) have displayed strong flares in the H2O line, when their peak flux desnity raised by a few orders of magnitude above the quiet state. Possible causes of this are discussed, among them consecutive excitation of the maser by a propagating shock wave and processes related to turbulence and graviatational instability in the circumstellar protoplanetary discs._x005F Other sources are new, recently discovered, strong emitters in the H2O and OH lines associated with quite young star-forming regions traced by Class I methanol masers radiating in the 44 GHz 70-61A+ transition of CH3OH.We attempt to range the sources observed according to the presence or absence of this or that maser (CH3OH, H2O, OH), thus creating an evolutionary sequence of the star-forming regions hosting these masers.
Full-spectral fitting techniques to characterise the stellar content in ultra diffuse galaxies
Ruiz-Lara, Tomás
Understanding the peculiar properties of Ultra Diffuse Galaxies (UDGs) via spectroscopic analysis is a challenging task that is now becoming feasible. The advent of 10m-class telescopes and high sensitivity instruments is enabling the gathering of high quality spectra even for the faintest systems. In addition, advances in the modelling of stellar populations, stellar libraries, and full-spectral fitting codes are allowing the recovery of the stellar content shaping those spectra with unprecedented reliability. In this talk we report on the extensive tests we have carried out using the inversion code STECKMAP. The similarities between the Star Formation Histories (SFH) recovered from STECKMAP (applied to high-quality spectra) and deep Colour-Magnitude diagrams fitting (resolved stars) in two Local Group dwarf galaxies (LMC and LeoA) are remarkable, showing the impressive performance of STECKMAP. We exploit the capabilities of STECKMAP and perform one of the most complete and reliable characterisations of the stellar component of UDGs to date using deep spectroscopic data. We measure recession and rotation velocities, SFHs and mean population parameters for a sample of UDGs in the Coma cluster. We prove the true UDG nature of three of the systems, not finding significant differences between the stellar populations of dwarf galaxies and UDGs. The SFHs of all the analysed galaxies are dominated by an old, metal-poor and alpha-enhanced population followed by a decline in the star formation which halts ~2Gyr ago (consistent with a bursty-declining SFH). As a consequence, we claim that UDG properties are independent of their SFHs. We also provide evidences favouring a dwarf-like rotation for UDGs. Accordingly, we suggest that UDGs are extended dwarfs whose properties are the outcome of internal processes (high-spin halo and/or bursty SFHs) as well as environmental effects for those located in groups or clusters.
Constraints on Circumbinary Planet Formation From ALMA and Sphere/IRDIS Imaging of V4046 Sgr.
Ruiz-Rodriguez, Dary
We present the highest-resolution continuum and scattered-light images obtained to date of the circumbinary disk orbiting V4046 Sgr, an actively accreting, close binary (K5+K7) T Tauri star system located a mere 72.4 pc from Earth. We observed the disk with the Atacama Large Millimeter/submillimeter Array (ALMA) at 850 µm (Band 7) during Cycle 4, and we analyze these data in conjunction with archival H band polarimetric images taken with the Sphere/IRDIS on the ESO Very Large Telescope (VLT). At 0.25" (20 au) resolution, the 850 µm emission reveals a ring with a maximum at 33 au and with an extension of ~ 90 au, while analysis of the 50 mas (4 au) resolution scattered light imaging confirms the presence of two dust rings peaking at ~ 15 and 25 au (see also Rapson et al. 2015; Avenhaus et al. 2018). From the 850 µm continuum emission, we infer a dust mass of ~ 64.0 MEarth for the 33 au radius ring. In addition, we combine two-dimensional two fluid (gas + particle) hydrodynamical calculations with three-dimensional Monte Carlo Radiative Transfer simulations to simultaneously model the potential observational signatures of protoplanet-induced gaps at millimeter and near-infrared (NIR) wavelengths. We find that a single planet with a mass in the range between 0.2 and 1 MJup orbiting at ~ 18 au from the central star can well reproduce the combination of a deep gap in scattered light and a surrounding bright 850 µm ring. The comparison of NIR and millimeter extensions suggests a flat disk with efficiently settling down of the grain particles to the midplane, as expected given V4046 Sgr's advanced age of ~ 20 Myr.
Object (3200) Phaethon — asteroid or dead comet?
Ryabova, Galina
Asteroid (3200) Phaethon was discovered in 1983 as 1983TB. Whipple [1] was the first who identified it as a likely parent body for the Geminid meteoroid stream. The origin of the asteroid is not clear. Apollo asteroids (155140) 2005 UD and 1999 YC were considered as possible members of the Phaethon–Geminid complex [2]. It was found that 2005 UD may be the remnant of the progenitor from which Phaethon and/or 1999 YC split [3]. Also a dynamical pathway was found from the Pallas family [4, 5], but how the Geminids could be generated on this pathway is not clear yet. Dynamical and spectral properties of Phaethon seem to support the asteroidal nature of the object. However modelling of the Geminid stream formation has shown that a cometary scenario [6] is in very good agreement with the observed structure features of the shower, as opposed to the collisional or eruptive scenarios. Lately (in 2009, 2012 and 2016) a weak recurrent activity in perihelion was observed. Thermal fracture/decomposition of the surface was considered the most probable mechanism for the activity [7], but it can not be the main Geminid source [8]. In 2017, Phaethon had a close encounter with the Earth, and many research teams observed both the asteroid and the Geminid meteor shower. In this report we’ll try to give a brief summary of the previous and new research data on this enigmatic object. At present the arguments for the Phaethon’s cometary origin prevail.[1] Whipple, F.L. (1983) IAU Circ., 3881, 1.[2] Ryabova, G.O. (2008) EPSC 2008, art. id. 226.[3] Ryabova, G.O. et al. (2014) ACM2014, 481.[4] de León, J. et al. (2010) A&A, 513, 26.[5] Todorovic, N. (2018) MNRAS, 475, 601.[6] Ryabova, G.O. (2007) MNRAS, 375, 1371.[7] Jewitt, D. and Li, J. (2010) AJ, 140, 1519.[8] Ryabova, G.O. (2018) MNRAS (submitted).
Dynamical instability criterion for asynchronous contact binary systems
S, Malu
We have studied the dynamical instability criterion for binary star merger with respect to the theoretical critical mass ratio (q_min) of contact binary systems. The merger hypothesis dictates a phase of tidal instability which would result in an ultimate merger of the two components. Assuming a synchronous configuration for the binary system, Rasio (1995) investigated the conditions leading up to merger using the Hut's criteria (Hut 1980) and Eggleton's (1983) formula for Roche lobes to derive a relationship between q_min and the dimensionless gyration radius (k1) of the primary component. Also, theoretically it has been predicted that critical mass ratio range of contact binaries varies from 0.07-0.09 (Arbutina 2007). And there is a general consensus that low mass ratio overcontact binary systems are prime candidates for merger (Sriram, K., S. Malu et al. AJ, 2016, 2017). But observationally, systems are found to merge before reaching q_min and those going below the theoretically predicted q_min are found to remain stable. Molnar et al. (2017) identified a contact binary system KIC 9832227 with a mass ratio of ~0.23 which is predicted to merge in the year 2022. Based on the standard equation, we estimated its J_spin/J_orb to be ~ 0.1 which is much less than Hut’s critical limit of 1/3 to trigger instability. Hence we propose an asynchronicity between the stellar rotation of the two components (beta parameter) and also between the orbital motion and stellar rotation of the system (alpha parameter) in order to explain systems like KIC 9832227. This asynchronicity can be caused due to rapid mass transfer after a critical mass transfer limit or due to a sudden mass loss spinning up the components creating an asynchronicity between the orbital motion which is more than what can be balanced by the transfer of orbital angular momentum to the spin angular momentum. We also revisit the relationship between the q_min and k1 upon introducing the asynchronicity parameters.
A radial velocity study of possible planets around A-type stars - can they really explain the strange signatures in 166 Kepler light-curves?
Sabotta, Silvia
Up to now very little is known about close-in planets of stars that aremore massive than the Sun. Detecting such planets is important because they challenge our current understanding of planet formation and migration.Balona (2014) identified 166 possible short-period planets around A-stars in the Kepler-survey based on strange features in their periodograms. He explains them as the consequence of differential rotation of the star and an orbiting exoplanet. The exoplanets do not show transits but the variations could be caused by the ellipsoidal, beaming and reflection effects on a Jupiter size planet. We have obtained about 230 spectra of a small subsample of those "Balona Stars" with the two echelle spectrographs at the Tautenburg and Ondrejov 2m telescopes. In ourposter, we provide upper limits for the masses of those possible planets and show if the upper limits agree with the variation of the lightcurves.
Unusual LSB dwarf companion of the interacting galaxy NGC4656
Saburova, Anna
We studied the dwarf low surface brightness galaxy with the enhanced UV brightness, NGC4656UV, belonging to the interacting system NGC4631/56. Regular photometric structure and relatively big size of NGC4656UV allows us to consider this dwarf galaxy as a separate group member rather than a tidal dwarf. Spectral long-slit observations were used to obtain the kinematical parameters and gas-phase metallicity of NGC4656UV and its companion - interacting galaxy NGC4656. Our rough estimate of the total dynamical mass of NGC4656UV allowed us to conclude that this galaxy is the dark-matter dominated LSB dwarf or ultra-diffuse galaxy. Young stellar population of NGC4656UV, as well as strong local non-circular gas motions in NGC4656 and the low oxygen gas abundance in the region of this galaxy adjacent to its dwarf companion, give evidence in favour of the accretion of metal-poor gas on to the discs of both galaxies.
A study of star formation sites in tightly interacting systems
Saburova, Anna
On the example of four strongly interacting systems (Arp 270, Arp 194, NGC4656, Arp305) we study the properties of ISM in star forming sites in the main bodies of the galaxies and in their vicinities: metal abundance and gas kinematics. For this purpose we used the long-slit spectral observations carried out at the Russian 6m telescope. All four systems are very different in their star forming history. In Arp 270 the emission gas is well chemically mixed, whereas in Arp 194 and Arp305 there are strong abundance and velocity gradients between the galaxies. In Arp 194 and NGC4656 we observe the evidences of continuing gas accretion onto the galaxies. In Arp194 and Arp305 we found a tidal dwarf candidates falling back into the parent galaxy. The close low surface brightness satellite interacting with NGC 4656 in contrast appears to be a metal-poor discy dwarf galaxy resembling ultra-diffuse galaxies where the mass of stellar population is low in comparison with the mass of dark matter and HI.We conclude that the observed star forming sites and emission knots connected with tidal debris have different history and chemical evolution depending on the presence or absence of accretion of metal poor gas on the system.
Star formation and environment: a step in understanding the formation and evolution of local dwarf galaxies
Sacchi, Elena
Over the past several years, it has become increasingly clear that the large-scale star formation is determined by a hierarchy of processes spanning a vast range of physical scales, and that different physical processes may lead to star formation in different interstellar and galactic environments. For nearby galaxies, we have the advantage of resolving the single stars, to study their stellar populations and star formation histories (SFHs) with the synthetic color-magnitude diagram technique and refine stellar evolution models by comparing them with the data. Within this framework, I will discuss the results obtained for the dwarf galaxies part of the HST Legacy ExtraGalactic UV Survey (LEGUS), whose aim is to investigate and connect the different scales of star formation, from young stellar clusters to local Universe galaxies. Our targets were studied both in the UV and optical bands, in order to recover their SFH from very recent to older epochs and to understand whether and how the star formation process may depend on the morphological, dynamical and environmental properties of the galaxies. In particular, we analyzed DDO 68, a very metal-poor dwarf irregular, and NGC 4449, a Magellanic irregular, finding clear correlations of SF enhancement with merging and interactions.
On the basins of convergence of the libration point in the axisymmetric restricted five-body problem: Concave case
Sachan, Prachi
In present paper, we have drawn and studied the Newton-Raphson basins of convergence associated with the libration points in the axisymmetric restricted five-body problem. We have discussed the motion of the infinitesimal mass (fifth body) moving under the mutual gravitational influence of four bodies which are fixed on the central configurations proposed by Érdi and Czirják (2016). The proposed central configuration can be easily visualized by taking a system of three masses on a straight line and then dividing the one of the mass into two equal halves to put them up and down in such a manner that the resulting four point masses configuration is symmetric about the x-axis. We have taken the concave case into consideration which can be obtained by splitting one of the other two peripheral masses to form a four-sided. Furthermore, we obtain two different type of concave configuration according to the fact that whether the center of mass of the system is enclosed by the polygon or not. We have numerically unveiled the domain of convergence corresponding to libration points by using the multivariate version of the Newton-Raphson iterative scheme. Moreover, we have successfully presented the correlations between the basins of convergence associated with the equilibrium point and the required number of iterations corresponding to it are also presented and discussed in detail. The present numerical analysis reveals that the evolution of the attracting domains in this complex dynamical system is worth studying._x005F Érdi, B., Czirják, Z.: Central configurations of four bodies with an axis of symmetry. Celest. Mech. Dyn. Astron. 125(1), 33–70 (2016) _x005F Gao, C., Yuan, J., Sun, C.: Equilibrium points and zero velocity surfaces in the axisymmetric restricted five-body problem. Astrophys Space Sci. 362:72 (2017)
High angular-resolution infrared imaging and spectra of the carbon-rich AGB star V Hya
Sahai, Raghvendra
The post-AGB star V Hya is believed to be in the very brief transition phase between the AGB and a planetary nebula. It is likely in the earliest stages of this transition of any known object. Using STIS/HST, we previously found a high-velocity (>200 km/s) jet or blob of gas ejected only a few years ago from near (<0.3'') the star. From multi-epoch high-resolution spectroscopy we previously found time-variable high-velocity absorption features in the CO 4.6 micron vibration-rotation lines of V Hydra. Modeling shows that these are produced in compact clumps of outflowing gas with significant temperature gradients. Here we present very high resolution (~100 mas) imaging of the central region of V Hya using the coronagraphic mode of the Gemini Planet Imager (GPI) in the 1 micron band and spectral-spatial imaging of 4.6 micron CO 1-0 transitions using the Phoenix spectrometer. We report successful detection of a compact central dust disk from GPI and molecular emission from the Phoenix observations at relatively larger scales. We discuss models for the central structures in V Hya, in particular disks and outflows, using these and complementary images in the optical and radio.
Gamma-ray emission from radio galaxies
Sahakyan, Narek
Fermi-LAT has recently detected gamma-ray emission from active galactic nuclei which do not show clear evidence for optical blazar characteristics or having jets pointing away from the observer (radio galaxies). These are interesting gamma-ray emitters providing an alternative approach to studying high energy emission processes. I will report on a detailed investigation of the gamma-ray emission from 21 radio galaxy, including eleven FRI and ten FRII radio galaxies/SSRQs based on the Fermi-LAT data accumulated during 2008-2015. Possible spectral changes above GeV energies are investigated with a detailed spectral analysis and the gamma-ray flux variability is studied using different light curves. The gamma-ray emission properties of the considered sources are compared with similar properties of blazars (their parent population). Also, the gamma-ray emission features of the individual sources will be discussed, for example, the rapid gamma-ray variability of NGC 1275, the emission from 3C 120 jet at small (nuclear region) and large scales (knots), etc.
Scaling relations and colors of dwarf galaxies
Saifollahi, Teymoor
The Fornax Deep Survey (FDS) (Iodice et al. 2016, Venhola et al. 2017) is a new ultra-deep imaging survey of 30 square degrees in 4 bands, in depth comparable to the Virgo NGVS survey. With as aim the study of galaxy formation and evolution in dense environments, it is studying a wide range of topics, including intracluster light and ultra-diffuse galaxies. My work consists of combining the FDS with near-IR VISTA observations in J and K. Near-infrared emission of galaxies mainly comes from old stellar populations, dominating the luminous mass of galaxies. In this work, for the first time, we use deep multi-band imaging in u, g, r, i, J and Ks, to map color, age and metallicity in Fornax cluster dwarf galaxies. Optical/near-infrared colors are good indicators of stellar populations (Roediger et al., 2011 and 2012, Urich et al., 2017) which can be used to break the age-metallicity degeneracy (Galaz et al, 2002). I will discuss scaling relations and radial color gradients.
Simulating the Water Vapor Flow through Enceladus' South Polar Cracks
Sakuler, Wolfgang
A plume of water vapor and ice particles has been discovered by the Cassini spacecraft orginating from the south polar terrain (SPT) of Saturn's icy moon Enceladus [1]. The observations by Cassini showed evidence that water vapor and ice particles are evaporating from a subsurface liquid ocean [2-4]. These particles flow through cracks in the ice shell, that have a crack depth between several 100 m and a few km [5] and an estimated crack width of ~0.1 - ~1 m [5].We analysed the water vapor flow through the vents via numerical simulations of the 2-dim Navier-Stokes equations. The distributions of pressure and the 2-dim velocity vector field inside the cracks have been computed. For the numerical simulations the open-source computing platform FEniCS (Finite Element Computational Software) [6] for solving partial differential equations (PDEs) has been employed. Simulations have been performed for different crack lengths and crack widths, and for various vent geometries, ranging from simple rectangles, i.e. having a constant crack width, up to more complicated structures with varying crack widths including throats, discontinuities, kinks, zig-zag lines, and forking branches.The calculations show that the distribution and magnitude of the velocity strongly depend on the vent geometry. Vents with varying crack widths experience strong velocity boosts around throat-like narrowings. The simulations for the more realistic vent geometries including throats and discontinuities provide velocity distributions at the upper vent opening that are consistent with observations.[1] Porco, C.C., et al., Science 311, 1393-1401, 2006.[2] Thomas, P.C., et al., Icarus 264, 37-47, 2016.[3] Cadek, O., et al., Geophys. Res. Lett. 43(11), 5653-5660, 2016.[4] Le Gall, A., et al., Nature Astronomy 1, 0063, 2017.[5] Nakajima, M., Ingersoll, A.P., Icarus 272, 309-318, 2016.[6] "The FEniCS Project page", https://fenicsproject.org
Interstellar, Circumstellar and Planetary Laboratory Astrophysics Studies with the NASA Ames COSmIC Facility – Recent Results and Progress
Salama, Farid
The COSmIC facility was developed at NASA Ames to study interstellar, circumstellar and planetary analogs in the laboratory [1]. COSmIC stands for “Cosmic Simulation Chamber” and is dedicated to the study of neutral and ionized molecules and nanoparticles under the low temperature and high vacuum conditions that are required to simulate space environments. COSmIC integrates a variety of instruments that allow generating; processing and monitoring simulated space conditions in the laboratory. It is composed of a Pulsed Discharge Nozzle (PDN) expansion that generates a plasma in a free supersonic jet expansion coupled to high-sensitivity, complementary in situ diagnostic tools, used for the detection and characterization of the species present in the expansion: a Cavity Ring Down Spectroscopy (CRDS) and fluorescence spectroscopy systems for photonic detection, and a Reflectron Time-Of-Flight Mass Spectrometer (ReTOF-MS) for mass detection. Recent advances achieved in laboratory astrophysics using COSmIC will be presented, in particular in the domain of the diffuse interstellar bands (DIBs) and the monitoring, in the laboratory, of the formation of dust grains and aerosols from their gas-phase molecular precursors in environments as varied as circumstellar outflows and planetary atmospheres. Plans for future laboratory experiments on cosmic molecules and grains in the growing field of laboratory astrophysics (NIR-MIR CRDS, Laser Induced Fluorescence spectra of cosmic molecule analogs and the laser induced incandescence spectra of cosmic grain analogs) will also be addressed as well as the implications of the on-going studies for astronomy.References:[1] Salama F., Sciamma-O'Brien E., Contreras C., Bejaoui S., Proceedings IAU S332, Y. Aikawa, M. Cunningham, T. Millar, eds, CUP (2018) and references therein.Acknowledgements: The authors acknowledge the support of NASA SMD/APRA and SSW programs.
The nature of the Triangulum-Andromeda stellar structures
Sales Silva, João
The Milky Way was formed in a complex chain of physical processes involving dissipative gravitational collapse, gas flows, and galactic mergers. The outer stellar halo is home to a number of substructures that are remnants of former interactions of the Galaxy with its dwarf satellites. Triangulum-Andromeda (TriAnd) is one of these halo substructures, found as a debris cloud by Rocha-Pinto, et al. (2004, ApJ, 615, 732) using 2MASS M giants. Recently, using SDSS data, Perottoni et al. (2018, MNRAS, 473, 1461) have uncovered several scattered dense excesses of main sequence stars situated in the TriAnd region. At least two of these excesses may represent new, not previously known, stellar structures, and one of them resembles a stellar stream. A similar discovery was made by Martin, et al. (2014, ApJ, 787, 19) in a smaller area around M 31. The better photometry in Martin, et al. (2014, ApJ, 787, 19) data points to a likely mix of stellar populations in these debris. I will present a study abundance patterns using high resolution spectroscopy of giant candidate stars that are situated in the overdensity regions of the stellar maps by Martin et al. (2014, ApJ, 787, 19) and Perottoni et al. (2018, MNRAS, 473, 1461), which may gives us clues on whether these stars may have been tidally stripped from a former dwarf satellite.
Testing the [Y/Mg] clock with open clusters
Sales Silva, João Victor
One of the greatest challenges of modern astronomy is the reliable age determination of the objects. This difficulty becomes more evident when we talk about estimates of the ages of field stars, which are usually linked to great uncertainties. Recently, some studies have attempted to overcome these difficulties by relating the age of stars to abundance ratios, exploring the mass indicators of these ratios. The [Y/Mg] ratio is one of the most promising ratios for age estimating. Open and globular clusters may play an important role in the verification of such a relation since clusters have well-defined ages. In this work, we determine the atmospheric parameters and the [Y/Mg] ratio for a sample of 29 single red giants of the open clusters NGC 2360, NGC 3680, and NGC 5822 using high-resolution spectroscopy. We employed the local thermodynamic equilibrium atmospheric models of Kurucz and the spectral analysis code MOOG. Our results indicate that the use of the [Y/Mg] ratio as a clock seems to be promising. However, this ratio for open clusters needs to be analyzed under the same methodology for a larger sample of clusters covering a wide range in ages.
Exploring DCO+ as a tracer of dust evolution in planet-forming disks
Salinas, Vachail
In planet-forming disks, deuterated species like DCO+ often show up in rings. Two chemical formation routes contribute: cold deuteration at temperatures below 30 K and warm deuteration at temperatures up to 80 K. In this work we reproduce the DCO+ emission in the disk around HD163296 using a simple 2D chemical model for the formation of DCO+ through the cold deuteration channel and a parametric treatment of the warm deuteration channel. We use data from ALMA in band 6 to obtain a resolved spectral imaging data cube of the DCO+ J=3–2 line in HD163296 with a synthesized beam of 0."53× 0." 42. The observed DCO+ emission is reproduced by a model with cold deuteration producing abundances up to 1.6e-11. Warm deuteration, at a constant abundance of 3.2e-12, becomes fully effective below 32 K and tapers off at higher temperatures, reproducing the lack of DCO+ inside 90AU. Throughout the DCO+ emitting zone a CO abundance of 2e10-7 is found, with ~99% of it frozen out below 19 K. At radii where both cold and warm deuteration are active, warm deuteration contributes up to 20% of DCO+, consistent with detailed chemical models. The decrease of DCO+ at large radii is attributed to a temperature inversion at 250 AU, which raises temperatures above values where cold deuteration operates. This return of the DCO+ layer to the midplane reproduces the local DCO+ emission maximum at ~260AU. We can use the morphology of DCO+ emission to trace the temperature substructures of disks produced by dust evolution processes. Outer disk temperature inversions, expected when grains decouple from the gas and drift inward, can lead to secondary maxima in DCO+ emission and a reduction of its radial extent. This can appear as an outer emission ‘ring’, and can be used to identify a second CO desorption front.
On the Kodylewski cosmic dust clouds formation
Salnikova, Tatiana
In this research we suggest a clarification of the phenomenon of appearance-disappearance of Kordyltewski clouds - accumulation of cosmic dust mass in the vicinity of the triangle libration points of the Earth-Moon system. In contrast with the Troyan asteroids in the vicinity of the Lagrange points of the Sun-Jupiter system, in our problem, under unavoidable gravitational and light perturbation of the Sun, the triangle libration points aren’t the points of relative equilibrium. However, there exist the stable periodic motion of the particles, surrounding every of the triangle libration points. Due to this fact we can consider a probabilistic model of the dust clouds formation. These clouds move along the periodical orbits in small vicinity of the point of periodical orbit. To continue this research we suggest a mathematical model to investigate also the electromagnetic influences, arising under consideration of the charged dust particles in the vicinity of the triangle libration points of the Earth-Moon system. In this model we take under consideration the self-unduced force field within the set of charged particles, the probability distribution density evolves according to the Vlasov equation.
Modeling of the full galaxy stellar mass function evolution
Salvador-Solé, Eduard
We present the results of AMIGA, a very complete self-consistent galaxy formation model that provides excellent fits to all the observed 13 independent cosmic histories, including the star formation and stellar mass density histories, of the Universe from z=15 to z=0. We show the predicted galaxy stellar MFs, derived down to the lowest galaxy stellar mass formed at every redshift. At the high-mass end those theoretical MFs fit the empirical ones derived from observation. At the low-mass end, they unveil the evolution of the dwarf galaxy population that is consistent with all the observed global cosmic properties.
V1187 Herculis, A Red Novae Progenitor, the Most Extreme Mass Ratio Solar-Type Binary
Samec, Ronald
Many solar type binaries have been found to undergo continuously decreasing orbital periods, presumably due to magnetic braking. A binary undergoing such a process will slowly coalesce over time as it loses angular momentum. This is due to ion winds streaming radially outward on stiff magnetic field lines rotating with the binary. Recently, overcontact binaries with decaying periods have been found to undergo a catastrophic merger (a Red Novae, RN). This leads to the formation of a single, fast rotating, spectroscopically, earlier-type star. As a part of the evolution of the RN progenitor, the binary’s mass ratio becomes more extreme and the Roche-lobe fill-out increases. It is believed that there is a maximum mass ratio leading to an instability and the occurrence of the RN. V1187 Her is apparently such a binary, and a progenitor of an RN. Complete BVRI photometric observations of V1187 Her were taken in May 2017 at Dark Sky Observatory in North Carolina with the 0.81-m reflector of Appalachian State University. Earlier, spectra were taken at Dominion Astrophysical Observatory with the 1.8m telescope. The spectral type is found to be F8±1V (6250 K) so the binary is of solar-type. V1187 Her was previously identified as a low amplitude (δV < 0.2 mag), short period, overcontact eclipsing binary (EW) with a period of 0.310726 d. Strikingly, despite its low amplitude, the early light curves show a total eclipse (eclipse duration: 31.5 minutes), which is a characteristic of an extreme mass ratio binary. A period study covering 11-years reveals a continuous period decrease (dP/dt= -4.7 X10-09 d/yr). The simultaneous W-D synthetic light curve solution gives a Roche Lobe fill-out of 79% along with a mass ratio of only 0.0440 ±0.0001. It has a cool spot region and its secondary component which is some 400 K hotter than the primary. The inclination is only 66.85±0.05˚ despite its total eclipses.
Recent Observations of Newly Coalesced Solar Type Contact Binaries (Shallow Contact Systems) CW Scl, V530 And, NSVS 5066754, DD Indi
Samec, Ronald
Short period solar type binaries manifest strong magnetic activity and X-rays. Winds flow outward along field lines carrying both mass and angular momentum away from the binary. This process causes orbital decay, one result being a semidetached or marginally detached to shallow contact binary transition. Another process that can operate about critical contact is thermal relaxation oscillations. This a cyclic process whereby the binary goes from a marginal detached state to a marginal contact state and back until firm contact is attained. Recent precision BVRI CCD observations were undertaken of four systems in a state of marginal contact. In these studies the light curves were simultaneously solved with the Wilson-Devinney Code (WD) and period studies were undertaken of each._x005F CW Sculptoris (T~ 6000K) was observed at Cerro Tololo InterAmerican Observatory (CTIO) with the 0.6-m SARA South reflector. An increasing period was determined from all available times of minimum light with a 1.14 ±0.16 X10-10 E2 quadratic term. Its mass ratio is~0.39, and the component temperature difference was 200 K. The Roche Lobe fill-out is only 7%. The inclination is 86˚. An eclipse duration of 19.5 minutes was determined for the primary eclipse, making the solution firmly determined._x005F V530 Andromedae was observed at Dark Sky Observatory (DSO) 0.81-m reflector of Appalachian State University. Our present curves reveal that V530 And as a totally eclipsing, shallow contact binary. As with CW Scl, the period study (over a 14 year interval) showed a decreasing period. The component temperatures were 6750 and 6030 K large for a contact binary. The fill-out, however, is a mere 5%. The mass ratio was found to be 0.39. Two magnetic star spots, were determined._x005F NSVS 5066754 (T1~5750 K) and DD Indus was (T1 ~ 5750K) will also be presented._x005F Conclusions will be drawn following the summarized results.
MAGNETIC ORBITAL DECAY OF SOLAR TYPE BINARIES AND THEIR GYROCHRONOLOGY
Samec, Ronald
A statistical study was begun with a poster session at the 2015 IAU GA--a compendium of more than 75 solar-type binaries was presented--each with a clearly decreasing orbital period. We conclude this study here by presenting new recently analyzed binaries to the previous study bringing the total to ~150 systems. These give strong evidence for the magnetic braking scenario regularly proposed by the binary community. Solar type binaries have strong magnetic activity and are X-ray sources. It is believed that binaries (for those of solar type), begin their existence as well detached fast spinning stars in groups that undergo gravitational interactions which leave them as binaries with several day periods. Since they are highly magnetic in nature, due to their convective envelopes and fast rotation, they undergo magnetic braking as plasma winds stream away from the stars on stiff rotating dipole fields. This action torques the binary, eventually bringing them into contact. They continue to coalesce and finally merge and undergo a cataclysmic event called a red nova, the aftermath of which is a single, earlier spectral type star (usually F or A)._x005F An age is computed for each binary, δt, based on the difference in the current orbital period and the proposed initial period, δP and the rate of orbital decay, dP/dt,_x005F δt= -δP/(dP/dt)._x005F The result is that the evolution of solar type binaries from formation to the present configuration averages more than two magnitudes faster than theory suggests. Further implications are explored.
Magnetically Active Noncontact Binaries: NSVS 2620909, NSVS 10083189, NSVS 10541123, GQ Cancri, FF Vulpecula
Samec, Ronald
Magnetic activity is common on solar type contact binaries and on the more massive RS CVn binaries. These exhibit magnetic spots, chromospheric activity (X-rays) and decreasing orbital periods due to magnetic braking. However, detached main sequence binaries should also should exhibit these characteristics since they are believed to be the progenitors of contact binaries. Recently observed detached binaries do indeed share these characteristics. Precision BVRI CCD observations were taken with the 0.81-m Dark Sky Observatory in North Carolina, and on the 1-m reflector at Kitt Peak National Observatory in 2013-2016. Analysis were done with the Wilson-Devinney (WD) program in noncontact (WD mode 2 or 4). _x005F FF Vulpecula has a period of 0.44 d. It is semidetached, i.e., with a V1010 Oph type configuration (larger component filling its critical lobe and the secondary under filing, mode 4). Thus, it is apparently approaching contact for the first time. The period is decreasing (dp/dt=-9.7×10-8d/yr). An equatorial hot spot was modeled on the cooler, secondary star, probably magnetic in origin. The component temperature difference, δt>1500 K. The solution confirms a total eclipse of 23 minutes duration. As expected, there is a magnetic cool spot region. NSVS 10541123 has a period of 0.59544 d. A quadratic ephemeris was determined, giving dp/dt= -5.96×10-7d/yr. The rapid period decline may indicate that the binary is undergoing magnetic braking and is approaching a contact configuration. It has a mass ratio of 0.5828, and a component δt of 2350 K. The large component difference confirms that the binary is not in contact. An apparent stream spot was computed with the primary component being the gainer. The fill-out is 96.3% for the primary component and 95.0% for the secondary component. The inclination is ~79˚. NSVS 10083189, GQ Cancri and NSVS 2620909 will also be highlighted. Conclusions are drawn following the significant results.
Astronomical Experience for Visually-Impaired People
Sanchez, Javier
With the ultimate goal of making visually impaired people participate in an astronomical experience, we have created two handy interfaces. One for converting solar observations into sounds and a second one for determining the color of stars in a stellar map. We implement both devices, capable of receiving the luminous emission and transform it into digital form through an arduino which carries the raw information to a Rasberry Pi platform.For the first implementation, by using a Sonic Pi program installed by default along with the operating system Raspbian, the received information is treated in the form of much more pleasant and harmonic tones for the sensitive ears of visually impaired people. In the second device, the mechanism directly transform the information into sound and vibrations for a touching experience.Both gadgets can be easily accomplished to be widely used at institutions and museums worldwide.
Determining the radius of an open cluster from stellar proper motions
Sanchez, Nestor
We propose a new method for calculating the radius of an open cluster in an objective way from an astrometric catalogue containing, at least, positions and proper motions. It uses the minimum spanning tree in the proper motion space to discriminate cluster stars from field stars and it quantifies the strength of the cluster-field separation. This is done for a range of different sampling radii from where the cluster radius is obtained as the size at which the best cluster-field separation is achieved. The novelty of this strategy is that the cluster radius is obtained independently of how its stars are spatially distributed. We test the reliability and robustness of the method with both simulated and real data from a well-studied open cluster (NGC 188), and apply it to UCAC4 data for five other open clusters with different catalogued radius values. NGC 188, NGC 1647, NGC 6603, and Ruprecht 155 yielded unambiguous radius values. However, ASCC 19 and Collinder 471 showed more than one possible solution, but it is not possible to know whether this is due to the involved uncertainties or due to the presence of complex patterns in their proper motion distributions.
ASTRONOMY AS A TOOL FOR INCLUSION OF BLIND AND VISUALLY-IMPAIRED STUDENTS AT UNIVERSITY
Sánchez, Yuly
In 2017 a pedagogical innovation project named “Feeling astronomy: astronomy for equity and inclusion” was approved to be funded by the Academic Office at the National University of Colombia. The project was selected among several other proposals due to the relevance of developing initiatives for the increasing population of blind and visually impaired students at the Bogota campus. In this work we present the experience of planning, designing and implementing an undergraduate course on astronomy, being the first time a course offered by the Faculty of Sciences represents an option to be taken by blind and visually impaired students. It has also the possibility of registration for student with full vision. Furthermore, this is the first time that such a course is officially registered in the curriculum of a colombian higher education institution. Students learned, among other topics, about the celestial vault, the Sun, the Moon, the Earth, eclipses, constellations, galaxies, cosmology, elementary particles, black holes, and dark matter. In the classroom, the board and conventional presentations are replaced by braille (tactile reading and writing system designed for blind people), embossed material, icopor, balloons, wool, bedbugs, pins, cardboard and even a kit of geometry in Braille, so that students can touch and feel what is being explained to them. Instructors were mainly composed by 8 teachers from the Physics Department and the National Astronomical Observatory of the university; a group of experts that assumed the challenge of preparing the class topics and the evaluations. Although astronomy is synonymous of visualization, we want to show that it can be understood with other senses, and that this initiative will help blind and visually impaired students to expand their perspectives into other fascinating topics that will help them to enlarge their perception of the world, giving to them a big picture of the human knowledge.
Quenching in the Virgo cluster down to logL = 6 Lsun
Sanchez-Janssen, Ruben
The Next Generation Virgo Cluster Survey (NGVS) has imaged the iconic nearest cluster out to its virial radius in visible and near-infrared wavelengths with unprecedented sensitivity and resolution. This has enabled detailed studies of the galaxy populations down to mass scales only previously probed in the Local Group, but with significantly larger statistical power. In this contribution I will summarise the main findings of the NGVS regarding the properties of cluster dwarf galaxies down to logL = 6 Lsun, with a specific emphasis on the fractions of quiescent and star-forming dwarfs as a function of stellar mass and clustercentric distance. I will discuss the results in the context of environmental quenching efficiencies and timescales in clusters compared to groups at these unprecedented mass scales.
Chemodynamics of z > 1 low-mass galaxies with MOSAIC: constraints to models of galactic feedback
Sanchez-Janssen, Ruben
A clear prediction from current hydrodynamical simulations of galaxy formation is that low-mass galaxies form the majority of their stars in episodic bursts. This is particularly true at high redshift, where the high accretion rates of metal-poor gas trigger intense starbursts which, in turn, drive metal-enriched outflows that can temporarily suppress star formation. A fundamental metallicity relation between the galaxy mass, its star formation rate and its metal content is thought to arise as a result of the interplay between inflows and outflows. However, spatially resolved chemodynamical information provides a more powerful diagnostic tool than integrated measurements of these quantities. Metallicity gradients are thought to be highly sensitive to the gas surface density, its kinematic structure (turbulence vs coherent rotation), and the prevalence of inflows and outflows. For example, feedback from starbursts is expected to completely erase any preexisting metallicity gradient. I will discuss how MOSAIC is perfectly poised to carry out the first statistically significant survey of the chemodynamical properties of low-mass galaxies at 1 < z < 3. The combination of spectral resolving power, sub-kpc spatial resolution and high sensitivity delivered by MOSAIC—together with the multiplex gain—will allow the study of radial metallicity gradients in large samples of high-z, low-mass systems. I will show how their chemical maps, further complemented with detailed kinematic information of the ionised gas across the galaxy, shall uncover the presence of infall-driven, turbulent star formation, as well as reveal the imprints of energetic outflows from supernovae.
The mass-metallicity relation in intermediate redshift clusters: the case of ZwCl 0024+1652
Sanchez-Portal, Miguel
The study of the distribution of galaxy metallicities with cluster-centric distance and local density is a powerful way to investigate evolution within clusters. The gas-phase metallicity is regulated by the interplay between star formation (SF), accretion of (metal-poor) gas and outflow of processed (metal-rich) gas. As galaxies fall into clusters and travel towards the cluster centre they interact with the intra-cluster medium (ICM) and other cluster galaxies, thus getting progressively stripped of their gas reservoir. This process is expected to influence their metallicity and possibly generate a gradient across a cluster. Intermediate- and low-redshift clusters are excellent candidates for studying the environment role in the metallicity. However, to date a limited number of studies of the metallicity of emission line galaxies (ELG) and its relationship with environment have been performed. Moreover, these studies arrived to controversial results: while some authors conclude that environment does not play a role in the metallicity of galaxies, others claim for either and enhancement/lowering of metallicity, as compared to field. Recent results suggest that the depletion of pristine gas in cluster galaxies is the main cause of the enhanced metallicity with respect to the predictions of the fundamental metallicity relation (FMR). In order to test this hypothesis, we have exploited the large sample of ELG compiled in our Halpha survey of the cluster ZwCl 0024+1652 at z = 0.395. We have separated pure SF galaxies from AGN and transition objects. For the pure SF objects, we have derived the metallicity by means of the N2 method and mass-metallicity relation (MZR). We correlate this information with the SFR) and galaxy morphology and also with environmental parameters such as local density estimates and the location of the galaxies in the projected velocity vs. cluster-centric distance phase space. The results from the study will be presented in this talk.
Quantifying the interplay of massive stars and the interstellar medium
Sander, Andreas
A significant part of our view on dwarf galaxies depends on understanding the young, bright, and massive stars in them. Their impact ranges from global quantities, such as the inferred star formation rate from the combined UV or H-alpha emission of a dwarf galaxy, over the chemical evolution due the enrichment with processed elements, down to the shaping of individual structures due to their ionizing and mechanical feedback.To substantially improve our picture of galaxy formation and evolution, the influence of massive stars has to be carefully studied and simulated. As stellar winds are inherent to all massive stars, this task requires a detailed, unified modelling of their outer layers and their winds. For hot stars, this requires complex radiative transfer calculations in an intricate non-LTE situation being performed in parallel with the explicit solution of the statistical equations for hundreds of atomic levels. Consequently, less than a handful of codes exist worldwide that are capable of performing this task for an expanding atmosphere with a line-driven wind. One of the most advanced among them is the Potsdam Wolf-Rayet (PoWR) code, nowadays applicable to hot stars of all kinds. The immense detail of the models allows applications drawing theoretical conclusions from models as well as the measurement of stellar parameters and feedback.Using PoWR as an example, this talk will give a brief summary about quantifying the impact of hot, massive stars with the help of modern atmosphere models. Apart from outlining the underlying physics that need to be taken into account, also challenges and powerful applications will be discussed, such as pinpointing the most important influencers in a cluster or predicting the spectral apperance of an unresolved stellar population. The talk will close by giving a brief overview of recent and oncoming applications that will allow to connect loose ends between the fields of massive stars and dwarf galaxies.
Exploring the Solar System with the Global Fireball Observatory
Sansom, Eleanor
Telescopes are observing increasingly smaller objects within the Solar System, though the number seen in the <10 m size range does not yet represent the true distribution and we know very little about these small objects. The Desert Fireball Network (DFN) monitors the sky across the Australian outback, observing and recording fireball events, with the underlying goal to remotely detect and physically collect meteorites. Although cometary meteors are well documented, these rarer fireball events (<4 Mag) typically represent larger material of asteroidal origin. With over 50 remote autonomous observatories covering a recoverable area of approximately 2.5 million km2, the DFN is the largest fireball camera network ever built. The DFN along with its 13 national and international partners have begun deploying systems worldwide forming a planet-scale facility. This Global Fireball Observatory (GFO) will conduct continuous coordinated observations of the night sky from both hemispheres, aiming to cover 2% of the Earth. Each remote station records horizon-to-horizon long exposures every 30 seconds throughout the night. If a fireball is captured on two or more camera systems, the event is triangulated, allowing a potential meteorite impact site and pre-entry orbit to be determined. Meteorites are the oldest rocks in existence, giving insights into Solar System evolution and formation. Attributing an orbit to these provides the key missing spatial context. As well as recent recoveries of meteorites with calculated orbits, the GFO is also able to provide continuous sky coverage for other astronomical transient observations.
KK69: a dwarf galaxy in transition?
Saponara, Juliana
Here we present new HI data of the dwarf galaxy KK 69, obtained with the Giant Metrewave Radio Telescope (GMRT). While optical images of KK 69 suggest it is a faint dwarf spheroidal galaxy, our high-resolution GMRT maps reveal the presence of a considerable amount of HI offset from the stellar body, indicating it may be a transitional dwarf galaxy. Tidal interactions between KK 69 and the nearby spiral galaxy NGC 2683 may be responsible and are being investigated. Furthermore, we are able, for the first time in this galaxy, to separate the cold and the warm neutral phases of the interstellar medium using a Gaussian decomposition method and a stacking routine. We will discuss our results taking into account the relation between the interstellar medium and the star formation activity in the galaxy, the role played by the environment and the influence of these phenomena in the galaxy's evolution.
The Local Group Dwarf Galaxies. The Star Formation Histories derived using the Long Period Variable Stars
Saremi, Elham
Dwarf galaxies in the Local Group (LG) represent a distinct as well as diverse family of tracers of the earliest phases of galaxy assembly and the processing resulting from galactic harrassment. Their stellar populations can be resolved and used as probes of the evolution of their host galaxy. In this regard, we present the first reconstruction of the star formation history (SFH) of them using the most evolved AGB stars that are long period variable (LPV). LPV stars trace stellar populations as young as ~ 30 Myr to as old as the oldest globular clusters. For the nearby, relatively massive and interacting gas-rich dwarf galaxies, the Magellanic Clouds, we found that the bulk of the stars formed ~ 10 Gyr ago for the LMC, while the strongest episode of star formation in the SMC occurred a few Gyr later. A peak in star formation around 0.7 Gyr ago in both Clouds is likely linked to their recent interaction. The Andromeda satellite pair NGC147/185 show different histories; the main epoch of star formation for NGC185 occurred 8.3 Gyr ago, followed by a much lower, but relatively constant star formation rate (SFR). In the case of NGC147, the SFR peaked only 6.9 Gyr ago, staying intense until ~ 3 Gyr ago. Star formation in the isolated gas-rich dwarf galaxy IC1613 has proceeded at a steady rate over the past 5 Gyr, without any particular dominant epoch.Due to lack of sufficient data, we have conducted an optical monitoring survey at the Isaac Newton Telescope (INT), of 55 dwarf galaxies in the LG to reconstruct the SFH of them uniformly. The observations have been made over ten epochs, spaced approximately 3 months apart, as luminosity of LPV stars vary on timescales of months to years. The system of galactic satellites of the large Andromeda spiral galaxy (M31) forms one of the key targets of our monitoring survey. We present the first results in the And I dwarf galaxy, where we discovered 92 LPVs among over 10,000 stars.
Infrared Studies of the Variability and Mass Loss of Some of the Dustiest Asymptotic Giant Branch Stars in the Magellanic Clouds
Sargent, Benjamin
The asymptotic giant branch (AGB) stars with the reddest colors have the largest amounts of circumstellar dust, which in turn suggests extremely high mass-loss rates. AGB stars vary in their brightness, and studies show that the reddest AGB stars tend to have longer periods than other AGB stars and are more likely to be fundamental mode pulsators than other AGB stars. Such dusty AGB stars are difficult to study, as their colors are so red due to their copious amounts of circumstellar dust that they are often not detected at optical wavelengths. Therefore, they must be observed at infrared wavelengths to explore their variability. Using the Spitzer Space Telescope, my team and I have observed a sample of very dusty AGB stars in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) over Cycles 9 through 12 during the Warm Spitzer mission. For each cycle, we typically observed a set of AGB stars at both 3.6 and 4.5 microns wavelength approximately monthly for most of a year. These observations reveal a wide range of variability properties. I present results from our analysis of the data obtained from these Spitzer variability programs, including light curve analyses and comparison to period-luminosity diagrams. Potentially the most interesting set of stars we observed is the sample of 13 stars from the LMC included in the set of so-called Extremely Red Objects (EROs) that were studied by Gruendl et al (2008, ApJ, 688, L9), who determined these carbon stars to have among the highest mass-loss rates of the LMC's carbon-rich AGB star population. Paradoxically, we found most of these stars to have little to no variability, perhaps suggesting these stars are reaching or have just reached the end of the AGB phase of their lives.
Infrared Spectroscopic Studies of Gases in the Circumstellar Environments of Young Stellar Objects
Sargent, Benjamin
The building blocks of planets in planet-forming ("protoplanetary") disks are assembled early in the lifetime of a young star. The gas disks are relatively short-lived, with a half-life of about 3 million years, as chemical reactions modify the reservoir of material from the natal molecular cloud. 5-7.5 micron wavelength Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of about a dozen T Tauri stars in the Taurus-Auriga star-forming region showing emission from water vapor and absorption from other gases in these stars' protoplanetary disks will be presented. Some of these stars' spectra show a strong emission feature at 6.6 microns due to the ?2 = 1-0 bending mode of water vapor, with the shape of the spectrum suggesting water vapor temperatures >500 K. Other stars' spectra show a strong absorption band, peaking in strength at 5.6-5.7 microns, which appears consistent in some cases with gaseous formaldehyde (H2CO) and in other cases with formic acid (HCOOH). Modeling of these stars' spectra suggests these gases are present in the inner few AU -- i.e., in the planet-forming regions -- of their disks. SOFIA-EXES spectra of YSOs that follow up on these Spitzer-IRS studies will be presented. How the gaseous features observed between 5-7.5 microns relate to those at other wavelengths will be discussed. Future directions for this research, including both pursuing confirmation of HCOOH and H2CO features at these and other wavelengths and modeling of the gas features at these wavelengths in other Spitzer-IRS spectra of protoplanetary disks around young stars, will also be discussed. This work suggests that water and organic molecules, which are crucial for life as we know it, are present in the habitable zones of stars at a very early age [of 1-3 million years].
Early Evolution of Icy Planetesimals: How Much Volatiles and Organics Are Lost Prior to Planetary Interactions?
Sarid, Gal
Early thermal and structural processes that affect planetesimals have strong implications for planet formation scenarios and the attributes of large dusty aggregates in proto-planetary disks. Observations and models of our solar system's planetary bodies have shown that outer nebula material has mixed with the inner parts of the solar disk, at various stages. The extent of this mixing is not entirely clear, but has been suggested to affect both atmosphere and surface compositions. Analogues processes may occur around other stars. We focus here on a less-studied epoch, between natal disk and planet evolution, in which small planetesimals form in the outer parts of a planetary disk and experience early bulk processing. We model the evolution of small icy planetesimals (up to ~10 km), such that radioactive heating, melting and convection play a negligible role, at most. Our starting point will rely on canonical comet models, which will then vary by: stellar radiation flux (affecting the major source of energy input), orbital lifetimes (derived from dynamical stability calculations), gas disk lifetimes (affecting surface pressure, material ablation and volatile loss rates), sizes (affecting heating/cooling timescales), initial porosity values (affecting heat and mass transfer) and composition ratios (water relative to silicate and volatile species relative to water). Emphasis is put on the emerging mechanical strength, heat input history, amorphous-to-crystalline water ice transition, and potential retention of volatile and organic species. At the end stage, whatever is not incorporated in planetary building blocks has little chance of being incorporated into the planets themselves.The varied thermal histories impose an additional composition gradient to that inherited from the disk’s physical-chemical state.Our framing question is: How much icy and volatile material is out there to be delivered to the atmospheres and surfaces of terrestrial planets?
The Ever Changing Centaur: Relating Activity, Orbital and System Evolution of Minor Bodies in the Giant Planet Region
Sarid, Gal
Centaurs roam the outer solar system region, mostly between the heliocentric distances of Jupiter and Neptune. The dynamical lifetime of the population is much shorter than the age of the solar system and these bodies may encounter many gravitational perturbations from the outer planets, thus making it a transient population (akin to the inner solar system's NEAs). Centaurs are transition objects not just by virtue of their dynamics, but also because they can exhibit both asteroid and cometary properties – Observed activity, surface composition, density. Several such objects have been observed to show cometary activity, in the form of observable comae, at least 2 objects (Chariko and Chiron) have a sustained ring system, and at least 2 known binary systems (Ceto/Phorcys and Typhon/Echidna) have derived densities between those of large and small KBOs. Notably there has been some tentative evidence for 2 active objects (29P and Echeclus) to also have a signature of a fragment or small moon associated.We develop a modeling scheme that connects sublimation-driven outgassing of species more volatile than water (CO, CO2, CH4, CH3OH) with the formation and retention of extended components (rings, moons, binaries), as a function of an object's dynamical environment (orbital variation, surface impacts). We utilize thermos-physical, dynamical and hydrocode calculations to track the outcome in terms of activity patterns, color/composition variations, sustained ring systems and effects of secondary bodies.Centaurs have a potentially crucial role in understanding the feedback between outer and inner solar system asteroid/comet populations. In addition, the process of initiating and maintaining activity beyond the water-activation distance is related to our basic understanding of how volatile species behave, both in the interior and surface of icy-rocky bodies
Instrumentation for Super DIOS
Sato, Kosuke
Super DIOS is an improved program to replace DIOS (Diffuse Intergalactic Oxygen Surveyor), aiming at wide-field spectroscopy of cosmic plasmas. The launch is expected after 2030. The instruments will consist of a large array of TES microcalorimeters with about 30,000 pixels, combined with an X-ray telescope with angular resolution about 10 arcseconds. The field of view will be about 30-40 arcmin in diameter, and the effective area will be more than 1000 cm2. We will also consider including a small gamma-ray burst monitor and a fast repointing system. The mission will be developed under international collaboration with Japan, US and Europe. We will describe the design of the instrumentation and the prospect of future development.
Playing to the Strengths of Non-Majors Students in Astro 101
Sato, Takashi
Astro 101 is a generic label for introductory survey courses for non-majors. A common struggle for instructors of Astro 101 is working with, or around, the students’ deficiencies in science and mathematical preparation. This paper describes an implementation of Astro 101, now in its eighth year, where the paradigm has been turned around to work with the strengths of the non-major students, rather than focusing on their deficiencies. Kwantlen Polytechnic University (KPU) is an undergraduate university outside Vancouver, Canada, where all classes are limited to 35 students. The typical Astro 101 student at KPU is an arts major. Although the course carries a first-year number, students can be in years 1, 2, 3 or 4 of a four-year degree. When they enter the Astro 101 class, students typically bring with them skills and experiences exceeding those of typical science undergraduates, in areas such as paper writing, active group learning, public speaking and group presentations.In this paper, one major course component, the term paper, is illustrated. The assignment comprises of four elements: proposal, written paper, abstract and participation in a panel discussion. With the small class size, the students have opportunities to work with the instructor on the proposal. Once the papers are complete, abstracts for the entire class are compiled into a booklet and circulated. The panel discussion provides a forum for students to share their new knowledge with the class, transforming what might have been a solitary exercise of the term paper into a culminating community experience.
DECIGO project for detection of gravitational wave in space
Sato, Shuichi
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the planned Japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz and 10 Hz and thus to open a new window for gravitational wave astronomy and for the universe. DECIGO will consist of three dragfree spacecraft, 1000 km apart from each other, whose relative displacements are measured by a Fabry-Perot Michelson interferometer. We plan to launch smaller-sized DECIGO, B-DECIGO, first to detect gravitational waves from mainly binary systems, and to demonstrate the technologies required to realize DECIGO.
4-D dust trail calculation of 2018 October Draconid
Sato, Isao
October Draconid is a meteor shower originated from 21P/Gicobini-Zinner. It is predicted to be seen from Europe this year. In primary dust trail theory in one dimension, a meteoroid is supposed to be ejected from the parent comet at the perihelion with a velocity in the direction of the velocity vector. But the author calculated a prediction with a dust trail theory in 4 dimensions, namly, a meteoroid is supposed to be ejected from any time on the orbit in 3-D velocity vector. As the result, the minimum ejection velocity to colide the Earth from the parent comet is 20m/s at 200 days after the perihelion passage of the 1946 dust trail. The peak time of apparition will be October 8th 22h50m.
Two Different Grain Distributions within the Protoplanetary Disk around HD 142527 Revealed by ALMA Polarization Observation
Satoshi, Ohashi
We present ALMA polarization observations of the 0.87-millimeter dust continuum emission toward the circumstellar disk around HD 142527 with high spatial resolution to identify the polarization mechanisms. There have been proposed three mechanisms for the polarized emission: grain alignment with magnetic fields, grain alignment with radiation gradient, and self-scattering of thermal dust emission.We confirm that the polarization vectors in the northern region are consistent with the self-scattering theory. Furthermore, we find that the polarization vectors in the southern region are likely explained by the grain alignment with the magnetic fields.To understand the difference in the polarization mechanisms, we propose a simple grain size segregation model: small dust grains ($\lesssim$ 100 micron) are dominant and aligned with the magnetic fields in the southern region, while middle-sized ($\sim100$ micron) grains in the upper layers emit the self-scattered polarized emission in the northern region because the grain size is $\sim\lambda/2\pi$, where $\lambda$ is the observing wavelength in the self-scattering theory.The grain size near the middle plane in the northern region cannot be measured because the emission at 0.87 mm is optically thick. However, larger dust grains ($\gtrsim$ cm) may be accumulated due to the gas pressure bump.This is consistent with the previous analysis of the disk in the senses that large grain accumulation and optically thick emission from the northern region. This model is also consistent with the theories where the smaller dust grains are aligned with magnetic fields. The magnetic fields are toroidal at least in the southern regions.
Photometry and spin rates of 3 Near Earth Asteroids observed in 2017 by the Mexican Asteroid Photometry Campaign
Saucedo Morales, Julio Cesar
We present photometric observations of (143404) 2003 BD 44, 2014 JO 25 and (3122) Florence, 3 large Near Earth Asteroids (NEAs) classified as “potentially hazardous” by the Minor Planet Center. With these data we obtained light curves and measured their spin rates. This work represents a step forward in our goal to contribute in the characterization of NEAs as well as of asteroids in general. The soaring discovery rate of asteroids seen in the last few decades is not matched by the rate with which they are individually studied to obtain crucial information about them. With this in mind, in 2015 a network was implemented to carry out photometric observations of asteroids: the Mexican Asteroid Photometry Campaign (CMFA). It has published spin rates for a dozen main belt asteroids, but up to the middle of 2017 only one NEA had been reported by the CMFA: (4055) Magellan, for which a rotation rate of 7.479 h was obtained. The observations of the NEAs reported here were taken near their approaches to Earth in 2017 by 3 different observatories: the 42 cm telescope of the Carl Sagan Stellar Observatory of Universidad de Sonora, the 36 cm Universidad de Monterrey Observatory and the 84 cm telescope of the National Astronomical Observatory on Sierra San Pedro Martir (OAN-SPM), Baja California. The rotation rates obtained for the NEAs are: 78.617 h for (143404) 2003 BD 44 (accepted for publication), 4.52 h for 2014 JO 25 and 2.29h for (3122) Florence. These results, as well as the related amplitudes in the light curves are in general agreement with those obtained by others. We discuss how this information is complementary to other studies.
The kinematics of galaxies with low dark matter fractions
Saulder, Christoph
Inspired by the kinematics of NGC 7507, which requires only a very low fraction of dark matter, we searched for galaxies with similar properties in numerical simulations that explicitly consider baryonic matter. Several galaxies, which we found in the Illustris and Eagle simulation, allowed us to study how they gain a surplus of baryonic matter or get deprived of dark matter. We also investigated the impact of the lower dark matter fraction on the angular momentum and kinematics of theses galaxies. Furthermore, we looked for correlations between the angular momentum and other parameters that help us to quickly identify galaxies with low dark matter fractions in large-scale surveys.
Resolving the ancient star formation of dwarf galaxies in the Local Group and beyond.
Savino, Alessandro
I will present a new approach that, for the first time, combines classical colour-magnitude diagram analysis with horizontal branch modelling, allowing to measure the star formation history of resolved galaxies with greater precision and detail than previously done. The combined modelling of many features on the colour-magnitude diagram helps to soften the age-metallicity degeneracy and permits to recover the ancient star formation of nearby galaxies with a precision of ~500 Myr. I will present the results of this modelling on a sample of Local Group dwarf spheroidal galaxies. The horizontal branch in all these galaxies show signs of a more complex ancient star formation history than has previously been realized. I will explain how the horizontal branch can be used to reveal detailed ancient star formation properties and look for commonalities in the early history of a sample of galaxies that are probes of the state of the Local Group in the early Universe. With the advent of next generation facilities, this new method has also the potential to extend or knowledge of ancient stellar populations to neighbouring galaxy groups, within several Mpc, providing a meaningful comparison with simulations over a cosmological representative volume.
Radio luminosity function at z = 6
Saxena, Aayush
We present a model to predict the luminosity function for radio galaxies and their linear size distribution at any redshift. The model takes a black hole mass function and Eddington ratio distribution as input and tracks the evolution of radio sources, taking into account synchrotron, adiabatic and inverse Compton energy losses. We first test the model at z = 2 where plenty of radio data are available and show that the radio luminosity function (RLF) is consistent with observations. We are able to reproduce the break in luminosity function that separates locally the Fanaroff–Riley class I and Fanaroff–Riley class I radio sources. Our prediction for linear size distribution at z = 2 matches the observed distribution too. We then use our model to predict an RLF and linear size distribution at z = 6, as this is the epoch when radio galaxies can be used as probes of reionization. We demonstrate that higher inverse Compton losses lead to shorter source lifetimes and smaller sizes at high redshifts. The predicted sizes are consistent with the generally observed trend with redshift. We evolve the z = 2 RLF based on observed quasar space densities at high redshifts, and show that our RLF prediction at z = 6 is consistent. Finally, we predict the detection of 0.63, 0.092 and 0.0025 z = 6 sources deg2 at flux density limits of 0.1, 0.5 and 3.5 mJy. We assess the trade-off between coverage area and depth and show that LOFAR surveys with flux density limits of 0.1 and 0.5 mJy are the most efficient at detecting a large number of z = 6 radio sources.
The EREBOS project - Studying the influence of substellar companion on stellar evolution
Schaffenroth, Veronika
Planets and brown dwarfs in close orbits will interact with their host stars, as soon as they evolve to become red giants. However, the outcome of those interactions is still unclear. Recently, several brown dwarfs have been discovered orbiting hot subdwarf stars in very short orbital periods of 0.065 - 0.096 d. More than 6% of those stars might have close substellar companions. This shows that such companions can significantly affect late stellar evolution and that sdB binaries are ideal objects to study this influence. More than a hundred new eclipsing sdB binary systems with cool low-mass companions with periods from 0.05 to 0.5 d were discovered based on their lightcurves by the OGLE project. We want to use this unique and homogeneously selected sample to derive the mass distribution of the companions, constrain the fraction of substellar companions and determine the minimum mass needed to strip of the red-giant envelope. We are especially interested in testing models that predict hot Jupiter planets as possible companions. Therefore, we started the EREBOS (Eclipsing Reflection Effect Binaries from the OGLE Survey), which aims at analyzing as many of the newly discovered HW Vir systems as possible based on a spectroscopic and photometric follow-up of all targets. For this we were granted with an ESO Large Program for ESO/VLT-FORS. Here we will introduce the project and give the current status together with the first results.
Population Synthesis of Planets Around M Dwarfs
Schlecker, Martin
Planet Population Synthesis is a statistical approach to study the conditions necessary for planet formation and evolution. The utilization of the Bern model of planet formation and evolution (Alibert et al. 2013) within a population synthesis framework (Mordasini et al. 2009) has led to testable predictions, such as the now-confirmed minimum in the planetary mass distribution between a few Earth masses and ~40 Earth masses (Mordasini et al. 2009).Ongoing efforts aim at applying this technique to the observational sample of the CARMENES survey, which searches for Earth-mass planets around nearby M-dwarf stars. By confronting our simulations with the planets and non-detections in the sample, we can improve our understanding of key processes in planet formation around low-mass stars. For this purpose, we extend our model to the regime of late-type stars, accounting for the different conditions in their protoplanetary disks. Changes to the original setup include a smaller inner disk radius, a down-scaled disk mass distribution, distinct morphologies for the solid disk and the gas disk, and N-body interaction between protoplanets.As a test case, we create a population of systems with a host star mass of 0.1 solar masses and compare it to observables of the TRAPPIST-1 multi-planet system (Gillon et al. 2017). By randomly drawing initial locations for 50 lunar-mass planetary embryos from a log-uniform distribution between 0.02 au and 10 au, we find that many features of this unique system can be reproduced. Using the resulting mean planetary mass as a metric, we find a domain in initial disk solid mass and disk extent favorable for the formation of systems similar to TRAPPIST-1.
VMC Proper motions of the outer LMC and the Magellanic Bridge
Schmidt, Thomas
Dwarf galaxies enable us to study early phases of galaxy evolution and are key to many open questions about the hierarchical structure of the Universe. The Large and Small Magellanic Cloud (LMC and SMC) are the most luminous dwarf galaxy satellites of the Milky Way. They are most likely gravitationally bound to each other and their last interaction occurred about 200 Myr ago. In addition, they are in an early phase of minor merging with the Milky Way and will impact the Galactic structure in the future because of their relatively large mass. However, there are still major uncertainties regarding their origin and their interactions with one-another and with the Milky Way.To gain greater insight into the Magellanic system, we used the VMC (VISTA near-infrared survey of the Magellanic Clouds) to calculate proper motions. These are used to study the internal kinematics of the galaxies and their interaction, which is possible due to the multi-epoch nature of the VMC survey. In this contribution, I am going to present first results on the study of the Large Magellanic Clouds and the Magellanic Bridge.
The peculiarity of the accretion process in the magnetic Ae star HD104237
Schoeller, Markus
We have studied the magnetospheric accretion in the Herbig Ae binary system HD104237 using spectroscopic parameters of the He I 10830, Pa gamma, and He I 5876 lines, formed in the accretion region. Employing 21 spectra obtained with ISAAC and X-shooter, we found that the temporal behavior of the diagnostic lines can be explained by a variable amount of matter being accreted in the region between the star and the observer. Using a periodogram analysis of the diagnostic line parameters, we examined the possible origin of the accretion flow in HD104237 and considered the following four scenarios: matter flows from the circumbinary envelope, mass exchange between the system's components, magnetospheric accretion (MA) from the disk onto the star, and fast high-latitude accretion from a disk wind onto a weakly magnetized star. Based on a correlation analysis, we were able to show that the primary component is responsible for the observed emission line spectrum of the system. Since we do not find any correlation of the spectroscopic parameters with the phase of the orbital period (P ~ 20d), we can reject the first two scenarios. However, we found a variation period of P = 5.37+-0.04d of the diagnostic line parameters, which likely represents the stellar rotation period of the primary and favors the MA scenario. An estimation of the radius of the magnetosphere (Rm ~ 2Rstar) also supports the MA scenario for HD104237. Yet, we cannot exclude that fast high-latitude accretion from a disk wind takes place in HD104237.
Astronomy for Africa: Student Support for Astronomy Modules via Distance
Schroeder, Anja
We obtained an OAD grant to support African students to register for astronomy courses at UNISA to learn more about Astronomy. This poster presents the project and the outcome.
The Very Young Be-Star X-ray Binary Circinus X-1
Schulz, Norbert
Accretion conditions and morphologies of X-ray transients containing neutron starsare still poorly understood. Circinus X-1 is a specifically enigmatic case where we observe X-ray flux changes covering four orders of magnitude. We observed Circinus X-1 many times since the launch of the Chandra X-ray Observatoryusing the high energy transmission grating spectrometer andeach time the source gave us a vastly different look. Most recently we caught the source at its very lowest X-ray flux at a flux of 1.8×10-11 erg cm-2 s-1.Its spectrum, a single 1.7 keV blackbody spectrum, showed a low emission radius of 0.4 kmwhich implies a high magnetic field between 1.7 and 4.8×1011 G depending on neutron star radius. Photoionized line emissions suggesta large emission volume and low plasma densities. The observed bluehifts of ~400 km s-1and emission volume is consistent with the ionized but distorted wind of a B5Ia supergaint companion confirming a previous identification. We argue that the companion of Cir X-1 isfast rotating Be-star and its stellar disk provides much of the observed excess column densities. We paint a scenario in which a precessing oblateBe-star rotator may explain the vast X-ray flux variations in the past.
Connecting Dynamical and Morphological Properties of Early-Type Galaxies at Different Redshifts
Schulze, Felix
Several recent studies using novel observational techniques, especially integral-field spectroscopy, suggest that the formation history, and thus the closely related in- and outflow of matter, is encoded in the stellar kinematics and angular momentum of galaxies. State-of-the-art integral field surveys like ATLAS3D, SLUGGS, CALIFA, SAMI, and MaNGA provide large data sets of kinematical observations of early-type galaxies (ETGs), yielding constraints on the formation of ETGs. Using the cosmological hydrodynamical Magneticum Pathfinder simulations, we investigate the paradigm of fast and slow rotating ETGs in a fully cosmological context. We show that the ETGs within the Magneticum simulation are in remarkable agreement with the observations, revealing fast and slow rotators quantified by the angular momentum proxy ?R and the flattening e with the observed prevalence. Taking full advantage of the three-dimensional data, we demonstrate that the dichotomy between fast and slow rotating galaxies gets enhanced, showing an upper and lower population separated by an underpopulated region in the edge-on ?R-e plane. Following the evolution of our sample through cosmic time, we show that the slow rotating population gets statistically significant below z = 2, while the considerable fraction of these galaxies transitions from fast to slow rotators on a short timescale, in most cases associated to a significant merger event. Furthermore, we connect the M*-j* plane, quantified by the b-value, with the ?R-e plane, revealing a strong correlation between the position of a galaxy in the ?R-e plane and the b-value. Going one step further, we classify our sample based on features in their velocity map, finding all five common kinematic groups, also including the recently observed group of prolate rotators, and connect their characteristic features to various fundamental properties.
Orbital Resonances of the Galactic halo
Schuster, William
Orbital resonances in the Galactic halo have been studied using a scaled Allen& Santillán (1991) Galactic mass model, which includes a Galactic bar. For the two moving groups of the Galactic halo, G18-39 and G21-22, originally detected by Silva et al. (2012), we find that with an angular rotation speed of the bar of 45-55 km/s/kpc the majority of stars in both groups appear trapped in two resonances over the Galactic plane, generated by the bar and which cross the solar vicinity. So, in reality these two moving groups are part of stellar supergroups which populate these two resonances. The position of these two groups in the (U,V) plane (the Bottlinger diagram) can be explained approximately by means of the mean (U,V) field generated by these two resonances crossing the solar vicinity, in contrast with the alternate explanation of Silva et al. (2012) based on the simulations of Meza et al. (2005) which consider that these two groups, seen as two peaks in the U Galactic velocity, have been created by the accretion of a dwarf galaxy by the Milky Way, such as that of Omega Centauri.
Astronomy in Mexico during the first years of the IAU.
Schuster, William J.
In 1918 the only Mexican institution dedicated professionally to astronomical work was the National Astronomical Observatory, which began operations in 1878. During the nineteenth year of the 20th century, Mexico was immersed in the armed movement known as the Mexican Revolution, which strongly affected both the social structure and the economics of the country. The Mexican astronomers saw their group drastically reduced and their infrastructure limited; however, they made great efforts to continue their participation in the international project of the "Carte du Ciel", since they were part of the 18 observatories that originally participated in it. Despite the limitations they suffered, they soon joined the group of 7 nations that in 1919 formed the International Astronomical Union (IAU), and two members of that National Astronomical Observatory actively participated in the first IAU General Assembly held in Rome in May, 1922.
The first astronomical text published in the American continent.
Schuster, William
In 1539 the Italian, Giovanni Paoli, better known as Juan Pablos, began operating in Mexico City the first printing press that existed in the New World. The first books he printed were religious texts, vocabularies of some indigenous languages of Mexico, and compilations of ordinances and laws. In 1556 he published the Sumario compendioso de las cuentas, a text of arithmetic and algebra that was the first American mathematics book. A year later, he published the Physica Speculatio, a text of Natural Philosophy that dealt with Aristotelian works such as Physics, On the Heavens, and Meteorology. As part of this book, was included the text of geocentric astronomy written during the thirteenth century by the Italian mathematician Giovanni Campano de Novara, entitled Tractatus de Sphaera, where the author discussed, from a geometric perspective, the cosmic structure and the stellar distribution. No doubt this is the first astronomical treatise that was published in the entire American continent, which is why it is emphasized here.
The Mexican Asteroid Photometry Campaign: Aiming for Asteroids' Rotation Periods.
Schuster, William
More than 750,000 asteroids are currently known and thousandsmore are discovered every year. The asteroid discovery rateis by far larger than the rate of determination of their physicalproperties. Taxonomical classifications, albedos, colors, androtation periods, among other properties, are useful to fullycharacterize an asteroid. In 2015, a group of researchers andstudents of various Mexican institutions established an observationalprogram to study asteroids photometrically using equipment atseveral observatories. The program was named the Mexican AsteroidPhotometry Campaign and aims to determine asteroids' rotation periods.The program is at an introductory stage that will allow us to gainthe abilities and basic knowledge related to asteroid main properties.The first observing campaign started during the second half of 2015,and two more annual campaigns have been organized since then. UntilDecember 2017 more than thirty asteroids have been observed and adozen light curves and rotation periods have been published. Theasteroids selected are bright, V<16 while in opposition, and most ofthese are located in the main asteroid belt. Four NEOs have also beenincluded. In this contribution, the main results obtained during thecourse of the observing campaigns and a brief description of plansfor the near future are presented.
The cosmic radio dipole
Schwarz, Dominik
The most pronounced anisotropy of the cosmic microwave background (CMB) is a dipole. It is believed to be caused by the proper motion of the Solar system, but this is a hypothesis that must be tested. Tests based on the Planck data allow for a 40% non-kinetic contribution to the CMB dipole. Large radio continuum surveys can test this proper motion hypothesis and probe the largest observable cosmic structures. We present estimates of the cosmic radio dipole at several frequency bands, based on catalogues from TGSS, WENSS, SUMSS and NVSS. The resulting radio dipole directions are consistent with the CMB dipole. However, the inferred radio dipole amplitude exceeds the expectation based on the proper motion hypothesis significantly and seems to depend on frequency. We discuss possible issues and explanations.
Exocomets in the Proxima Centauri system and their importance for water transport
Schwarz, Richard
The scenario and the efficiency of water transport by icy asteroids and comets are still amongst the most important unresolved questions of planetary systems. The detection of Proxima Centauri b (PCb), which moves in the habitable zone of this system, triggered a debate whether or not this planet can be habitable depending on its formation history and available water content. A better understanding of cometary dynamics in extrasolar systems shall provide information about cometary reservoirs and give an insight into water transport especially to planets in the habitable zone.In our study we perform numerous N-body simulations with PCb and an outer reservoir of comets. We investigate close encounters and collisions with the planet, which are important for the transport of water. Observers found hints for a second planet with a period longer than 60 days. Our studies show, that from the dynamical point of view, two planets are stable even for a massive second planet with up to ~ 12 Earth masses. In a third model we perform simulations including exocomets, a second planet, and the influence of the binary alpha-Centauri.The studies on the dynamics of exocomets reveal that the outer limit for water transport is between 100 and 200 au. In addition we could show that water transport would be possible for a close in planetesimal cloud (1-4 au) which was detected by Anglada et al. 2017. From our simulations we estimate the water mass delivered to the planets to be between 0 and 30 Earth oceans.Anglada G., et al., 2017, ApJ, 850, L6
The Nearby Evolved Stars Survey: Project description and initial results
Scicluna, Peter
Outflows of asymptotic giant branch (AGB) and red supergiant (RSG) stars drive the chemical evolution of galaxies in the local Universe. Thanks to Spitzer, a number of Local Group galaxies have been observed in detail, allowing the dust-production rates of all AGB stars and RSGs to be determined, and hence the total dust injection rate for the galaxies. However, measuring the gas mass-loss rates for stars outside our galaxy is prohibitively difficult, making it unlikely that both components of mass loss can be studied for a large sample in the foreseeable future beyond our galaxy. Such systematic studies in the Milky Way remain conspicuously absent. The Nearby Evolved Stars Survey (NESS) aims to fill this gap, through a large multi-telescope project targeting a volume-limited sample of approximately 400 evolved stars within 2 kpc. We intend to derive the dust and gas return rates in the Solar Neighbourhood, and to constrain the physics underlying these processes. So far, the project includes an ongoing JCMT survey of CO (2-1), (3-2) and dust continuum towards the Northern and equatorial parts of the sample, an APEX programme to observe the Southern sources, and a pilot program at the Nobeyama observatory to observe CO (1-0). The key science goals of NESS include determining the total gas- and dust-mass returned to the local interstellar medium, constraining the onset of dust- and pulsation-driven winds, constraining mass-loss variability, gas-to-dust ratios, and dust properties in the outflows of evolved stars, measuring the 13C/12C ratio from CO isotopologues to constrain nucleosynthesis and stellar evolution, and statistical studies of Galactic AGB stars as a population. I will present a detailed description of the project, including the motivation and strategy, and highlight some of our early results. I will also briefly introduce the tools we are developing that will, along with all raw and reduced NESS data, be released to the community to aid reproducibility.
Observing the mass-loss of nearby red supergiants through high-contrast imaging
Scicluna, Peter
Mass-loss in cool supergiants remains poorly understood, but is one of the key elements in the final stages of their evolution, helping to determine when a given star will explode as a supernova, and what kind of supernova it will become. Some show evidence of asymmetric mass loss, discrete mass-ejections and outbursts, with seemingly little to distinguish them from more quiescent cases. Various explanations have been put forward, including multiplicity, magnetic effects and starspots, but consensus has yet to emerge. To explore the prevalence of discrete ejections and companions we have conducted a high-contrast survey using near-infrared imaging and optical polarimetric imaging of nearby southern and equatorial red supergiants, using the extreme adaptive optics instrument SPHERE, which was designed to image planets around nearby stars. I will present a highly-automated pipeline designed to reduce this data and the initial results of the survey, including the detection of large (approximately 0.5 um in radius) dust grains in the ejecta of VY CMa and a candidate dusty torus aligned with the maser ring of VX Sgr, in which there are also suggestions of large dust grains. These will be compared with observations of circumstellar material at other wavelengths. I will briefly speculate on the consequences for our understanding of mass loss in these extreme stars.
NESSI and ‘Alopeke - speckle imaging for exoplanet validation and characterization
Scott, Nicholas
NESSI and `Alopeke are two new speckle imagers built at NASA's Ames Research Center for community use at the WIYN and Gemini telescopes, respectively. Both instruments operate in the visual band and provide two-color channels simultaneously. The instruments have speckle and wide-field modes. NESSI has a FoV of 19'' for speckle mode and 56'' for wide-field mode; while 'Alopeke has a FoV of 7'' for speckle mode and 60'' for wide-field mode. Both instruments have evolved from the Differential Speckle Survey Instrument (DSSI). A primary role of these instruments is exoplanet validation for the Kepler, K2, TESS, and many RV programs. The diffraction-limited imaging available through speckle effectively eliminates distortions due to the presence of Earth's atmosphere by `freezing out' changes in the atmosphere by taking extremely short exposures and combining the resultant speckles in Fourier space. This technique enables angular resolutions at the diffraction limit. Our instruments provide the highest spatial resolution available today on any single telescope. Contrast ratios of 6 or more magnitudes are easily obtained with the instrument's two emCCD cameras. Simultaneous dual-color speckle observations down to 17th magnitude (at Gemini) can help characterize detected companions. High resolution imaging enables the identification of blended binaries that contaminate many exoplanet detections, leading to incorrectly measured radii. In this way small, rocky systems, such as Kepler-186b and the TRAPPIST-1 planet family, may be validated and thus the detected planets radii are correctly measured. The wide field imaging mode enables fast time-series and traditional photometry with narrow band or SDSS filters.
How do X-shaped radio galaxies form?
Sebastian, Biny
We present our low-frequency radio study of an extended sample of X-shaped sources using the Giant Metrewave radio telescope (GMRT) done with a primary aim to distinguish between various models for the formation of X-shaped radio sources. This study concentrates on the study of spectral properties of the active lobes versus the off-axis emission observed in X-shaped radio galaxies. The combined sample consists of 26 X-shaped radio galaxies which were observed using the GMRT at two frequencies (610 and 240 MHz). We find that the general class of X-shaped radio galaxies tend to show comparable spectral indices in both the active lobes and the wings and the steepening of spectrum that is usually seen in a general FR II radio galaxy population is observed rarely. We speculate that such a behaviour is due to the re-acceleration of the plasma due to the turbulence induced by a merger of galaxies. We have also tried to explore the possibility that several different mechanisms play a role in the formation of these objects rather than a single unified model for the entire class of X-shaped radio sources. We will also discuss the role of twin AGN models in the formation of such objects.
Challenges with Gender, Immigration and Diversity for Astronomers from Developing Countries
Sekhar, Aswin
Firstly, in the present global immigration climate, astronomers (and scientists in general) from the developing and less privileged countries face various exterior challenges when it comes to travel, migration and funding. These factors affect early career researchers as well as permanent staff in multiple ways. Some pivotal issues in this regard will be presented. Secondly, a comparative study with respect to gender gaps in astronomy from multiple cultures will be discussed. Latest statistics show that gender parity figures are much better in Latin American, Eastern European and South East Asian cultures compared to the more prosperous Western cultures. Thirdly, it would be interesting to find the broader reason and logic for such gender gap variations amongst diverse cultures from different parts of the world. All these exercises aim to contribute towards the wider inclusiveness and bridging diversity elements amongst astronomers from different parts of our planet.Reference:Sekhar A. 2018, Letters to Editor, Nature (accepted)Sekhar A. 2017, Contributed Talk to Inclusiveness and Diversity Session, European Planetary Science Congress, Riga, Latvia (kindly funded by Europlanet RI)
Association of Radio Polar Cap Brightening with Bright Patches and Coronal Holes
Selhorst, Caius
Radio-bright regions near the solar poles are frequently observed in Nobeyama Radioheliograph (NoRH) maps at 17 GHz, and often in association with coronal holes. However, the origin of these polar brightenings has not been established yet. We propose that small magnetic loops are the source of these bright patches, and present modeling results that reproduce the main observational characteristics of the polar brightening within coronal holes at 17 GHz. The simulations were carried out by calculating the radio emission of the small loops, with several temperature and density profiles, within a 2D coronal hole atmospheric model. If located at high latitudes, the size of the simulated bright patches are much smaller than that of the beam size and they present the instrument beam size when observed. The larger bright patches can be generated by a great number of small magnetic loops unresolved by the NoRH beam. Loop models that reproduce bright patches contain denser and hotter plasma near the upper chromosphere and lower corona. On the other hand, loops with increased plasma density and temperature only in the corona do not contribute to the emission at 17 GHz. This could explain the absence of a one-to-one association between the 17 GHz bright patches and those observed in extreme ultraviolet. Moreover, the emission arising from small magnetic loops located close to the limb may merge with the usual limb brightening profile, increasing its brightness temperature and width.
Comparison of solar radio and extreme ultraviolet synoptic limb charts during the present solar maximum
Selhorst, Caius
We analyze daily images at 304 and 171 Å obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The 17 GHz maps were obtained by the Nobeyama Radioheliograph (NoRH). To construct synoptic limb charts, we calculated the mean emission of delimited limb areas with 100'' wide and angular separation of 5o. At the equatorial region, the results show a hemispheric asymmetry of the solar activity. The northern hemisphere dominance is coincident with the first sunspot number peak, whereas the second peak occurs concurrently with the increase in the activity at the south. The polar emission reflects the presence of coronal holes at both EUV wavelengths, moreover, the 17 GHz polar brightenings can be associated with the coronal holes. Until 2013, both EUV coronal holes and radio polar brightenings were more predominant at the south pole. Since then they have not been apparent in the north, but thus appear in the beginning of 2015 in the south as observed in the synoptic charts. This work strengthens the association between coronal holes and the 17 GHz polar brightenings as it is evident in the synoptic limb charts in agreement with previous case study papers. The enhancement of the radio brightness in coronal holes is explained by the presence of bright patches closely associated with the presence of intense unipolar magnetic fields. However, observations with better spatial resolution and also at different radio wavelengths will be necessary to fully understand the physical mechanisms that link these features.
The X-ray Binary Populations of M81 and M82
Sell, Paul
We present a detailed study of the X-ray point source populations of the nearby, star-forming, spiral galaxy M81. Using deep HST data, we uniquely classify the X-ray binary (XRB) populations on the basis of their donor stars and local stellar populations. We measure the X-ray luminosity functions (XLFs) of the different XRB sub-populations (early-type main sequence, supergiant, low-mass, globular cluster), and we compare these results with predictions from XRB population synthesis models. This more robust classification (than the common, simple bulge/disk spatial separations) of XRBs minimizes contamination between different sub-populations, and it shows that high-mass XRBs have steeper XLFs than the “canonical” star-forming galaxy XLF commonly used. In the case of globular clusters, we find that more massive and denser globular clusters are more likely to be associated with XRBs. We also compare these results with the XRB populations of the prototypical starburst galaxy, M82, for which we present the deepest XLF reported for a starburst galaxy. We discuss the variations of the XRB populations in regions of M82 dominated by star-formation episodes at different ages, and in the context of predictions from XRB formation and evolution models.
Development of a Web-based Testbed System for Korean Astronomical Records Service
Seo, Yoon Kyung
Korea has kept its records of astronomical phenomena since around 2,000 years ago. However, the contents and scope of relevant service have been limited for researchers who need those records due to lack of complete data collection. In this regard, it is necessary to establish efficient collection and management systems of Korean astronomical records by utilizing an environment that is easily accessible. This study is intended to complete the development of a testbed system that allows researchers to systematically input and validate, in a Web environment, multiple astronomical records among the historical documents until Modern Joseon after the Three Kingdoms Period. Recognition of the pre-translated data and tables in advance is followed by its storage in the database built on the Web. Then, data validation is implemented by providing a retrieval service according to a specific form to only a finite number of researchers who have access authority. This study is targeted at a testbed system that takes around three months to be completely developed. The completed testbed system is expected to allow internal and external researchers of an organization to easily access the service on the Web. This will ensure that the accuracy of the data can be verified mutually and help identify areas of service improvement. The opinions collected regarding service improvement will be reflected in the future system. Eventually, domestic astronomical records will subsequently be able to be utilized internationally through the multilingual service.
Polarization as a Probe of Thick Dust Disk in Edge-on Galaxies: Application to NGC 891
Seon, Kwang-il
Radiative transfer models were developed to understand the optical polarizations in edge-on galaxies, which are observed to occur even outside the geometrically thin dust disk, with a scale height of ˜ 0.2 kpc. In order to reproduce the vertically extended polarization structure, we find it is essential to include a geometrically thick dust layer in the radiative transfer model, in addition to the commonly-known thin dust layer. The models include polarizations due to both dust scattering and dichroic extinction which is responsible for the observed interstellar polarization in the Milky Way. It is found that the magnetic fields in edge-on galaxies are in general vertical (or poloidal) except the central part, where the magnetic fields are mainly toroidal or have no coherent pattern. We also find that the polarization level is enhanced if the clumpiness of the interstellar medium, and the dichroic extinction by vertical magnetic fields in the outer regions of the dust lane are included in the radiative transfer model. The predicted degree of polarization outside the dust lane was found to be consistent with that (ranging from 1% to 4%) observed in NGC 891.
A new dynamical code for hot, exozodiacal dust
SEZESTRE, Elie
Near-Infrared interferometric observations have constrained the presence of hot, subµm-sized and C-rich dust grains in the inner part of numerous extrasolar planetary systems. This so-called hot exozodiacal dust is a challenge at different levels, the most difficult conundrums being the origin of this dust itself and its survival time. The classic picture is that the hot dust originates from the outer parts of planetary systems and slowly drifts inward by Poynting-Robertson drag until it sublimates when it gets sufficiently close to the star. The hot dust dynamics is such that its survival timescale implies a complete replenishment each year for the brightest systems.Here, I will present a new numerical code treating consistently all individual forces acting on a dust grain migrating inward by P-R drag. The code resolves the critical sublimation time period and follows the grain trajectory from its release point up to its expulsion from the system by radiation pressure or until complete sublimation.First, we show that, contrary that what has been assumed so far in the literature, it is not possible to create nanometer-sized dust grains from larger, compact grains through this process. Indeed, we find that the grains are expelled from the system by radiation pressure before reaching this size. This minimum accessible grain size is furthermore predictable. In a second step, we test different physical processes that could increase the dust lifetime in order to mitigate the dust replenishment mass rate necessary to maintain disks observable over long timescales. We explore the impact of stellar magnetic field on the dust dynamics, and evaluate under which conditions magnetic trapping could occur and extend the grains lifetime close to the star.I will conclude on the future applications and developments of this code, including the implementation of mutual collisions between the grains, and the ability to produce images and SED directly comparable with the observations.
The Open Universe and Data-driven Astronomy
Shah, Priya
Activities related to access to astronomical facilities and data could offer an effective, entry-level path for outreach and astronomy education. The Government of Italy proposed the Open Universe initiative that was adopted by the United Nations Office of Outer Space Affairs. Education in astronomy is a key method to promoting rational thinking and the scientific method. We shall discuss how new methods using available data need to be used for outreach and education to help vizualise and understand actual data. We shall show, using GAIA DR2 data, how present data analysis and visualization tools can be used to identify star clusters, moving groups and runaway stars. Thus, with this example, real data can be used to understand stellar dynamics in the galaxy.
In the Pursuit of Astronomy Education and Outreach in India
Shah, Priya
I shall discuss various efforts being made at the level of citizens, school and college students and university researchers as an individual, team as well as part of the Public Outreach and Education Commitee of the Astronomical Society of India. I shall discuss the Lunar Eclipse Campaign, aimed at confronting supersitions and false beliefs in people regarding eclipses. I shall talk about the Zero Shadow Day Campaign as well as the different simple experiments done in schools with minimum tools to explain important concepts about the Sun and the Moon's movements. The Astronomy Olympiad program in India will also be discussed. We are organising an Astro-Expt themed workshop to set up a repository of experiments that can be adopted by Physics Departments in the country to address the lack of experiments in our education system. I shall also talk about "Shrishti Astronomy" and various activities conducted in Hyderabad, India to reach out to people. I shall also discuss the pitfallls and challenges and suggest working models that may prove more effective.
Modeling of the 35-day optical variations of HZ Her/Her X-1
Shakura, Nikolay
The photometric optical light curve of the X-ray binary Her X-1/HZ Her collected over more than 40 years of observations (including those of the authors) is analysed. The model 35-day light curve of the system is calculated and compared with observations. The model include a precessing warped accretion disk around a neutron star which freely precesses with the 35-day period. The precession of the disk is locked to the neutron star precession via dynamical interaction of gas streams forming the accretion disk. The X-ray diagram shape formed by the complex accretion structure around the neutron star magnetic poles is also taken into account for the calculation of the X-ray illumination of the optical star atmospher which shapes the observed optical light curves. The proposed model well describes the observed changes of the 35-day light curve with the precession period phase, which cannot be explained by the precession of the accretion disk only.
Characterizing the Obliquity Variability of Terrestrial Habitable Zone Planets
Shan, Yutong
Obliquity variations could play an important role in the climate evolution and habitability of a planet. Orbital modulations caused by planetary companions and the planetary spin axis precession due to the torque from the host star may lead to resonant interactions and cause large amplitude obliquity variability. We discuss the spin-axis dynamics of terrestrial planets in multi-planet systems, using two specific habitable zone exoplanets, Kepler-62f and Kepler-186f, for illustration. Using numerical and analytical techniques, we characterize regions in parameter space where their obliquities are variable. We find that the locations of variability in lower obliquity regimes (?40 deg) are fine-tuned over the planetary properties and system architecture. As an example, if rotating at 24h, the obliquities of both Kepler-62f and Kepler-186f are stable below -40 deg, whereas the high obliquity regions (?60 deg) allow moderate variabilities. However, for other rotation periods, the lower obliquity regions could allow large-amplitude oscillations. We show how extra undetected planetary companions and/or the existence of a satellite could also destabilize obliquity at various values. Even small deviation from coplanar configurations could greatly amplify variability. Our analytical results has implications for characterizing obliquity evolution, and in turn climate stability, as a consideration for habitability.
The research of metallicity effect on the L8-LIR relation in nearby universe
Shao, Xu
SFH plays a fundamental role when people try to understand the evolution of galaxies. FIR observation is considered to be ideal to measure SFR bacause most of the FIR emission arises from dust heated by star formation activities. The low spatial resolution and dust temperature bias of FIR selected galaxies bring the main uncertainty of their SFR estimation. Especially for high redshift galaxies, the peak of their FIR emission has shifted to longer wavelength, such as sub-mm. This will make it difficult to measure their FIR emission and estimate their SFR. To improve these disadvantages, the polycyclic aromatic hydrocarbon (PAH) radiation is introduced to be a tracer of IR luminosity. The PAH selected galaxies have the advantages of high spatial resolution and dust temperature independence. Moreover, PAH emission of galaxies with different redshifts can be observed by different telescopes. Establishing accurate "L8-LIR" relation gives us an opportunity to measure uniform SFR of galaxies with different redshifts and study their evolution.Based on a large PAH selected sample in nearby universe, we studied the metallicity effect on 8um luminosity and "L8-LIR" relation. By cross-matching the Spitzer IRAC 8um photometry catalog with spectral observation of MMT and SDSS, we selected star forming galaxies with PAH emission at 0.02<z<0.3. the="" herschel="" pacs="" and="" spire="" have been="" used="" to="" estimated dust="" temperature="" and far="" infrared="" luminosity.="" we="" find="" that="" lir="" l8="" ratio="" deviates="" from="" main="" sequence="" indicated="" by="" elbaz="" et="" al.="" (2011)="" at="" faint-end="" of="" l8.="" the lir="" keeps="" constant="" 12+log(o="" h)="" >8.6="" becomes="" high="" in="" low-metallicity="" environments. this="" trend="" may="" be="" result="" weak="" pah="" emission="" environment,="" which="" is="" also="" our="" results.="" after="" correcting="" metallicity="" effect="" on lir="" ratio,="" obtained="" accurate "l8-lir"="" relation="" this="" will="" help="" study="" star="" formation="" redshift="" galaxies="" using="" forthcoming="" jwst.<="" z<0.3.><="" p=""> </z<0.3.></z<0.3.></z<0.3.></z<0.3.></z<0.3.>
Non-parametric SED fitting of galaxies and measuring of their star formation histories
Shao, Zhengyi
A new approach is built to modeling the SED of galaxies including their photometric passband observations and Lick index from spectroscopic data. This method is based on a construction of the non-parametric star formation history (SFH) which is divided into discrete time intervals and fitting the average rate of star formation in each interval. Based on the Bayesian framework, the full probability density functions of the fitting star formation rates are obtained and it is flexible to reconstruct these rates to some new parameters, such as the total stellar mass, time scale of the SFH, recent SFR, etc. The method is validated by applying it to monometallic synthetic photometric catalogues created with different input SFHs, assessing how the accuracy of the recovered stellar masses and SFHs depend on the photometric passband set, signal-to-noise ratio and redshift. The results show that it is possible to distinguish an early burst of star formation from a late one, provided an appropriate passband and Lick index set is used. Moreover, the Bayesian Evidence is used to assess the synthetic spectral libraries and the initial mass functions. Fitting results of Local group dwarfs are discussed.
BH/PSR Binaries in the Galaxy
Shao, Yong
We have performed population synthesis calculation on the formation of binariescontaining a black hole (BH) and a neutron star (NS) in the Galactic disk.Some of important input parameters, especially for the treatment of common envelopeevolution, are updated in the calculation. We have discussed the uncertainties from the starformation rate of the Galaxy and the velocity distribution of NS kickson the birthrate ($ \sim 0.6-13 \rm\, Myr^{-1}$)of BH/NS binaries. From incident BH/NS binaries, by modelling the orbital evolutionduo to gravitational wave radiation andthe NS evolution as radio pulsars, we obtain the distributions of the observable parameterssuch as the orbital period, eccentricity and pulse period of the BH/pulsar binaries.We estimate that there may be $\sim 3-80 $ BH/pulsar binaries in the Galactic disk and around10\% of them could be detected by the Five-hundred-meter Aperture Spherical radio Telescope.
Mixture Model for Kinematics and Memberships of Open Cluster
Shao, Zhengyi
The Mixture-model approach is improved to measure the kinematics of open clusters, while all astrometric data, such as the coordinate position, proper motion and radial velocity, are used simultaneously to separate the motion of the cluster from that of the field stars. A Bayesian inference approach is employed to deal with the case of missing data of proper motion or radial velocity, and the Bayesian evidence is calculated to estimate the necessity of the mixture-model,since it is a quantitative identification of the existence of a cluster. The involving of multiple kinds of observational data, especially the high-precision radial velocity, significantly decreases the contamination degree of the cluster and field stars, and leads to the much more accurate value of the mean proper motion of the cluster. Based on the UCAC5 and radial velocities from RAVE and APOGEE, about 2000 clusters are determined. Meanwhile, the kinematic membership probabilities of individual stars are calculated. This method is expected to apply to the homogenous data from GAIA-DR2 to establish the cluster sample with full kinematic parameters. Furthermore, the dynamics of the Milky way disk will be analyzed by tracing of the open clusters.
Observational Evidence in Favor of Scale Free Evolution of Sunspot Groups
Shapoval, Alexander
The hypothesis stating that the distribution of sunspot groups versus their size s follows a power law in the domain of small groups was recently highlighted but rejected by Muñoz-Jaramillo et al (Astrophys. J. 800, 48, 2015) in favor of a Weibull distribution. In this paper, we re-consider this question and come to another conclusion. We suggest a new definition of group size, namely the spatio-temporal ``volume'' (V) obtained as the sum of the observed daily areas instead of a single area associated with each group. With this new definition of ``size'', the width of the power-law part of the distribution s~1/Vß increases from 1.5 to 2.5 orders of magnitude. The exponent ß is close to 1. A bump and an abrupt turn down to the right follow the power law segment: we show that such a transition from a power function to a quick bend down does not fit adequately a Weibull distribution. The best fits to the truncated power-law and Weibull distribution functions are estimated by the maximum likelihood method. Our findings are stable with respect to the selection of different catalogues and the choice of computational parameters. The right end of the power law segment corresponds to the groups whose area estimated as several hundred millionths of solar hemisphere corresponds to supergranules. Supergranulation likely determines an upper characteristic size of solar magnetic structures, and the power law segment extends up to this characteristic size. The existence of a wide 1/V part of the distribution s suggests that self-organized criticality underlies the generation and evolution of sunspot groups and that the mechanism responsible for it is scale-free over a large range of sizes.
Testing Star Formation Laws Using ALMA On A High-Redshift Lensed Galaxy
Sharda, Piyush
Using high-resolution (sub-kpc scale) submm data obtained from ALMA, we analyze the dust spectral energy distribution (SED) and kinematics of CO (5-4) in a molecular cloud in SDP.81, a high-redshift lensed galaxy at z~3. We fit the SED by a modified blackbody (MBB) function and subsequently obtain the bestfit temperature and emissivity as 39.5 K and 2.5, respectively. Integrating the bestfit MBB (to estimate far infrared luminosity) and using the Kennicutt luminosity-SFR relation, we calculate the observed SFR surface density (?_SFR) in this clump to be 357+135-85 MT per year per kpc².We use a new gradient subtraction algorithm to find the turbulent velocity dispersion in the plane of sky. By evaluating the gas surface density, free fall time and turbulent Mach number, our calculations reveal that the role of turbulence is vital to explaining the observed SFR in this clump. Using the measured ?_SFR and gas properties, we test three popular star formation relations on this extreme starburst clump: the Kennicutt-Schmidt relation, the Krumholz-Dekel-McKee relation and the Salim-Federrath-Kewley relation. While the gas surface density based Kennicutt Schmidt (KS) relation predicts a ?_SFR = 52±17 MT per year per kpc², the single-freefall time based Krumholz, Dekel and McKee (KDM) relation predicts ?_SFR = 106±37 MT per year per kpc². On the contrary, the multi-freefall (turbulence) based Salim, Federrath and Kewley (SFK) relation estimates the ?_SFR = 491+139-194 MT per year per kpc². Although the SFK relation overestimates the SFR in this clump (possibly due to the negligence of magnetic fields), it provides the best prediction of the SFR in this clump. We also compare the star formation and gas properties of our high-redshift molecular clump to local star-forming regions and find that the SFK relation provides good estimates of ?_SFR in both local and high-redshift clouds.
Population gradients in dwarf spheroidal galaxies KKs 3 and ESO 269-66
Sharina, Margarita
We compare the properties of stellar populations for globular clusters and field stars in two dwarf spheroidal galaxies (dSphs): ESO 269-66, a close neighbor of the giant S0 NGC 5128, and KKs 3, one of the few truly isolated dSphs within 10~Mpc. The star formation histories of the galaxies are known from the results of the deep stellar photometry of Hubble Space Telescope (HST) images performed in previous studies. The age and metallicity for nuclear star clusters in KKs~3 and ESO~269-66 are known from literature spectroscopic studies: T=12.6~Gyr, [FeH]=-1.5 and -1.55 dex. We analyze the surface density profiles of low and high metallicity (blue and red) stars in KKs3 and ESO 269-66 using the Sersic law. We argue that 1) the density profiles of red stars are steeper than those of blue stars, which evidences in favor of the metallicity and age gradients in the galaxies; 2) globular clusters in KKs 3 and ESO 269-66 contain approximately 4 and 40 percent of all stars with [FeH]~-1.5- -1.6 dex and the age of 12-14 Gyr, correspondingly. Therefore, globular clusters are relics of the first powerful star-forming bursts in the central regions of the galaxies. KKs 3 has lost a smaller percentage of old low-metallicity stars than ESO 269-66, probably thanks to its isolation.
Accreting supermassive black holes, their jets and their nuclear environment at z~0: A multi-wavelength study including GMRT, ASTROSAT, ATCA and Chandra
Shastri, Prajval
We will present results from a multi-wavelength investigation of very nearby accreting supermassive black holes that seeks to understand the interaction between accretion, jets and the host galaxy environment, and test the hypothesis that imprints of AGN feedback are present at z~0. Our sample contains about 130 AGN which were chosen to have redshifts less than 0.02. Consequently our typical imaging has several spatial resolution elements across the host galaxy. We have completed optical IFU measurements for all the 130 objects in our sample and have some radio imaging for a majority. Results for individual objects as well as two data release papers from this study (the ‘S7’ project) have been published. We take this investigation further by adding GMRT imaging and archival VLA imaging for subsets of this sample, and also ATCA, ASTROSAT and Chandra observations for select objects. Our most recent results include Far-UV imaging with ASTROSAT of a galaxy in a rich cluster environment, and Chandra imaging of a dual AGN system. Systematics for the whole sample including the relationship between the radio jets and the nuclear environment will also be presented.
Some reflections on the total lunar eclipse campaign of January 2018
Shastri, Prajval
A total lunar eclipse occurred on the 31 January 2018, starting around moon rise throughout South Asia. Eclipses continue to draw responses of fear and superstition in large sections of the public in India, even among people with tertiary educational qualifications. It is of concern that the learning of science in formal spaces appears to be having only a minimum impact on mindsets, and that despite the generous funding that scientific research institutions have received over several decades, scientific thinking is in deficit in larger society. A campaign was organised around the total lunar eclipse of January 2018 in order to use the inspirational cosmic event to build scientific awareness and maximise viewing of the eclipse throughout India. Information in multiple languages was made available, and dissemination of information and resources was done using a combination of the internet, social media and country-wide popularisation networks. The details of the campaign and some of the lessons drawn will be discussed.
What does the angular momentum imply about the formation history of an elliptical jellyfish galaxy?
Sheen, Yun-Kyeong
An elliptical galaxy emanating long ionized gas tails from a rotating gas disk in the galaxy center was discovered in Abell 2670 (z = 0.076) using VLT/MUSE IFU data (Sheen et al. 2017). Based on asymmetric distributions of gas tails and star-forming blobs to the opposite direction of the cluster center, we suspect that the elliptical galaxy is subjected to strong ram-pressure stripping in a massive cluster halo. While the origin of rich gas component in the elliptical galaxy remains unresolved, we examined stellar kinematics of the galaxy with MUSE spectra. Firstly, it did not show any hints of a stellar disk in its stellar velocity map while the MUSE data revealed a clearly rotating gas disk in the galaxy center. Consdiering large velocity dispersions of the stellar component, it seems that a central stellar disk arising from the star-forming gas disk has not been developed yet. Secondly, we found that the kinematic parameter, lambda_R, of the galaxy is distinct from general characteristics of slow and fast rotators. It occupies the region in between slow and fast rotators in the parameter space of lambda_R vs. ellipticity, and presents a very flat lambda_R profile out to the effective radius. When we compared the velocity dispersion (sigma) map and the lambda_R profile with the simulations in Naab et al. (2014), it was confusing because the characteristics of the galaxy did not correspond well to their classification scheme for stellar kinematics accroding to different formation histories. Further discussion will be presented about an implication of the angular momentum for the formation scenario of the elliptical jellyfish galaxy.
The origin of Wolf-Rayet stars at the low metallicity environment of the Magellanic Clouds
Shenar, Tomer
Through their radiation, stellar winds, and supernova explosions, massive stars shape the evolution of their host galaxies. Wolf-Rayet (WR) are evolved, hydrogen depleted massive stars that exhibit strong mass-loss and dominate the stellar feedback on their environments. It is generally not known whether the majority of WR stars in the Magellanic Clouds originate via stripping in binary systems or via intrinsic stripping due to mass-loss. We performed a complete spectral analysis of all known WR binaries in the Small and Large Magellanic Clouds (SMC, LMC), as well as additional orbital analyses, and constrained the evolutionary histories of these important stars. In my talk, I will summarize our study's findings regarding the origin of WR stars in the Magellanic Clouds and their feedback on their environments. I will further describe the our study's implications on gravitational wave progenitors and on the initial mass function as at sub solar metallicities.
Disassembling MaNGA Galaxy Disks
Shetty, Shravan
In recent years a growing body of evidence has emerged indicating a strong correlation between the angular momentum and other global galaxy properties. If, as the evidence suggests, the processes driving galaxy evolution can be traced by the angular momentum of their stellar populations then it is crucial that the distribution and evolution of angular momentum in galaxies is understood.Since 1925, it has been observed that the young stellar populations in the Solar Neighborhood are likely to have a higher rotational velocity than their older counterparts. This relation, known as the Stellar Age – Velocity Dispersion Relation (AVR), has since been confirmed with ever larger stellar surveys of the Milky Way and, using novel techniques on high resolution data, has been recently observed in M31 and M33. However the source of this phenomenon has remained elusive and without a larger data set progress may be slow.In this poster we present the results of our research to develop a methodology to probe the AVR in galaxies observed in the MaNGA IFU survey. To this end we have developed two techniques, one using empirical stellar spectra and another using single stellar population models, to disentangle the rotational velocities of co-spatial young and old stellar populations in disk galaxies. Using disparate assumptions, the consistent results between these techniques demonstrate the confidence in the derived velocities of the two populations in real MaNGA galaxies. We further demonstrate the reliability of the techniques by comparing the results for select spaxels taken from real galaxy datacubes with results from a a Bayesian analysis. Additionally using realistic MaNGA-like mock spectra we have tested the accuracy and robustness of the techniques to probe the AVR of galaxies in a range of stellar ages, star formation histories, AVR shapes etc.
Dynamical environments of MU69: a state of chaotic clearing
Shevchenko, Ivan
The second (after Pluto) plausible target object for the New Horizons mission is 2014 MU69. It is a classical TNO, a primordial contact binary. Identifying any material in the vicinities of a target object is of on especial concern for planning cosmic fly-byes, as it is hazardous for a space probe. Luckily, no such material has been reported for MU69 up to now. The point of our report is that this lucky absence is just a dynamical consequence of the physical nature of MU69. Spinning gravitating dumbbells create zones of dynamical chaos around them, and this has a clearing effect: any material put in orbits around a rotating dumbbell (e.g., any material ejected from its surface) cannot be long-lived in such zones; it either escapes into space, or returns to the parent body's surface. As the orbiting matter is removed in this way, a spinning gravitating dumbbell clears its vicinities. We show that MU69 is able to create such a clearing, making itself a safe and hospitable target for a space mission. Therefore, the guest probe is expected to be safe on arrival.
Resonant multi-lane patterns in circumbinary young debris disks
Shevchenko, Ivan
Formation of resonant multi-lane patterns in circumbinary young debris disks with planets is considered in a set of representative massively simulated models. We find that the long-term-stable resonant patterns are generically formed, shepherded by embedded planets. The patterns are multi-lane, i.e., they consist of several concentric rings. Statistical dependences of their parameters on the planetary orbital parameters are recovered. Relevant additional massive simulations of planetesimal disks in systems with parameters of Kepler-16, Kepler-34, and Kepler-35 are accomplished and described. We find that the co-orbital patterns generically form in systems with moderate orbital eccentricities of the binary's and planetary orbits (like in Kepler-16 and 35 cases). We argue that any observational identification of characteristic resonant ring-like patterns in disks of the considered class may betray presence of planets shepherding the patterns.
Potentially habitable circumbinary worlds in the Solar neighbourhood
Shevchenko, Ivan
We analyze avalable databases on binary stars in the Solar neighbourhood, and for each binary we (1) calculate the radii of the inner and outer borders of the annular circumbinary habitable zone (CBHZ), if present, and (2) calculate the radius of the circumbinary zone of orbital chaos (the circumbinary chaotic zone, CCZ). Then we identify those binaries for which the CCZ borderline is inside the CBHZ (i.e., the CCZ radius is greater than the CBHZ inner radius but smaller than the CBHZ outer radius). As soon as the CCZ border is just the place where a pile-up of circumbinary planets (CBP) is expected (both on theoretical and observational grounds), the identified stars may host potentially habitable CBP; therefore, they represent promising targets for future observations.
Massive identification of resonant and chaotic exoplanetary systems
Shevchenko, Ivan
Data on the known exoplanetary systems are considered to extract subsets of (1) multiplanet exosystems (exosystems with more than one planet) and (2) exosystems of binary (and, generally, multiple) stars. Both subsets are analyzed on the subject of the presence of resonant and/or chaotic orbital behaviours. For this purpose, numerical integrations of planetary orbits (with known and most probable values of parameters and initial conditions) are accomplished on suitable time intervals. The resonant behaviour is revealed by means of analyzing the time behaviour of the resonant arguments of mean motion resonances up to prescribed orders. The chaotic behaviour is revealed by means of computation of the maximum Lyapunov exponents. Lists of nominally resonant and chaotic exosystems are constructed, and their statistical analysis is performed.
Star Formation Rate with Support Vector Machine
SHI, FEI
The emission-lines of galaxies originate from massive young stars or supermassive blackholes.As a result, the star formation rate (SFR) from emission-line of spectra relates closelyto formation and evolution of galaxy and SFR is a key parameter in the study of galaxy evolution.To find efficient and automatic SFR determination method for emission-line galaxies,especially in large surveys and huge databases, a support vector machine(SVM) regressionalgorithm is applied to a sample of emission-line galaxies from the Sloan Digital Sky Survey(SDSS) data release 9 (DR9) provided by the Max Planck Institute and the Johns HopkinsUniversity (MPA/JHU). A two-step approach is adopted:(i) The SVM must be trained witha subset of objects that have the known SFR, treating the strong emission line flux measurementsas input feature vectors in an n-dimensional space, where n is the number of strongemission line flux. (ii) After training on a sample of emission-line galaxies, the SFR of remaininggalaxies are automatically determined. In the calculation process, we use a five-foldcross-validation technique. We show that the SVM based on redshift plus the emission-lineflux, such as [N ii], Ha, [O iii], Hß, [Ne iii], [O ii], [Ar iii], [S ii], and [O i], and physical propertiesof galaxies( Excitation parameter P, Dust attenuation tV, Color, 4000Å break, Chemicalabundance and Stellar mass), allows to determine SFR of emission-line galaxies. The SVMmethod can easily be extended to any SFR determination task when redshift and the flux ofthe emission-lines can be measured.
High Frequency Quasi-periodic Oscillations Produced from Magnetohydrodynamical Waves in Low Mass X-ray binaries
Shi, ChangSheng
We suggest a possible explanation for the high frequency quasi-periodic oscillations (QPOs) in_x005F low-mass X-ray binaries. By solving the perturbation magnetohydrodynamic equations, we find_x005F two stable modes of the Magnetohydrodynamical wave in the accretion disks. We suggest that these_x005F two modes may lead to the double high frequency QPOs if they are produced in the innermost accretion disk. This model naturally accounts for some phenomena (e.g. the parallel tracks of kHz QPOs in NS-LMXBs, the 3:2 relation for the upper and lower frequencies of the QPOs in BH_LMXBs).
SUPER STRONG MAGNETIC FIELDS OF NEUTRON STARS IN BE X-RAY BINARIES
Shi, ChangSheng
We re-estimate the surface magnetic fields of neutron stars (NSs) in Be X-ray binaries (BeXBs) with different_x005F models of torque. In particular, a new torque model is applied to three models of magnetosphere radius. Unlike the previous models, the new torque model does not lead to divergent results for any fastness parameter. The inferred surface magnetic fields of these NSs for the two compressed magnetosphere models are much higher than that for the uncompressed magnetosphere model. The estimated surface magnetic fields for NSs BeXBs in the Large Magellanic Cloud, the Small Magellanic Cloud and the Milk Way are between the quantum critical field and the maximum “virial” value by the spin equilibrium condition.
CCD Photometry of Main Belt Comets 176P/LINEAR, 238P/Read and 288P/2006 VW139
Shi, Jianchun
The study of Main Belt Comets (MBCs) has attracted a great deal of interest in recent years since the recognition of MBCs as a new class of comets in 2006. To study activity and physical properties of three MBCs 176P/LINEAR, 238P/Read and 288P/2006 VW139, we carried out broadband CCD photometry of three MBCs. The upper limit of the nucleus radius, the color index, the Afrho values and the dust production rates were derived. Finally,the activity of three MBCs were discussed.
Metallicity gradients in local strong line emitters
Shim, Hyunjin
We investigate the spatially resolved chemical abundance distribution of ionized gas emission in local "Halpha emitters" of which Halpha equivalent width as large as that of strong star-forming galaxies at z>4. Most of the galaxies have flat metallicity gradient which is expected to be the result of the metallicity mixing. Based on the emission line ratios, most Halpha emitters lie in the region of a low-metallicity HII galaxies, yet are also explained by the low metallicity AGN with high ionization parameter.
Dependence of substructure abundance of clusters on large-scale filaments
Shim, Junsup
Substructure abundance of clusters in large-scale filaments is studied to investigate the environmental dependence of halo formation by using the dark matter halos of Big Multidark-Planck simulations. The abundance of substructures with (M = 1012h-1M?) in cluster halos with (M = 1014h-1M?) are examined, as a function of the specific size of host filament defined as the spatial extent divided by the number of member clusters. The clusters in filaments with larger specific size tend to have fewer substructures or vice versa. This anti-correlation persists, even if the formation epoch of the clusters or the number of member clusters of the host filament is constrained. Assuming the filaments with the larger specific size form in higher tidal coherence regions, we claim that the stronger development of the flows perpendicular to the filament, obstructs satellites infalling and matter accreting onto the clusters.
Solar-C_EUVST mission
Shimizu, Toshifumi
The Japanese solar physics community has proposed Solar-C_EUVST mission concept to ISAS/JAXA in reply to 2017 Announcement of Opportunity for competitive M-class missions launched by Epsilon rockets around 2025. This mission is designed to comprehensively understand the energy and mass transfer from the solar surface to the solar corona and interplanetary space, and to investigate the elementary processes that take place universally in cosmic plasmas. This is a fundamental step for answering how the plasma universe is created and evolves, and how the Sun influences the Earth and other planets in our solar system. The two scientific objectives for Solar-C_EUVST are: (I) to Understand how fundamental processes lead to the formation of the solar atmosphere and the solar wind, and (II) to Understand how the solar atmosphere becomes unstable, releasing the energy that drives solar flares and eruptions. The main instrument is an EUV spectrometer that will observe the solar atmosphere from the chromosphere up to the corona with seamless temperature coverage. The instrument capabilities (the spatial, spectroscopic and temporal resolutions) will supersede those of previous instruments by an order of magnitude in order to achieve the timescales of plasma dynamics throughout the solar atmosphere. This instrument is the highest priory instrument recommended in the report from Next Generation Solar Physics Mission’s Science Objectives Team (NGSOM-SOT) and will make major contribution to the formation of constellation of solar physics satellites in mid 2020s. The instrument will be developed and operated with participation from various institutes in US and European countries. This talk will introduce this mission concept to the Division E community in IAU.
A statistical Study of Cluster Formation
Shimoikura, Tomomi
In order to carry out a statistical study of cluster formation, we have conducted observations toward 15 star-forming regions. We used the NRO 45m telescope to observe the regions with several molecular lines at 100 GHz (e.g., C18O) and 45 GHz (e.g., CCS). We also conducted the analyses using the 2MASS Point Source Catalog to reveal the star density distribution around the regions. We identified 24 clumps, and found that 16 of them are associated with young clusters. To characterize the clumps and clusters in terms of cluster formation, we categorized them into four types according to the spatial coincidence of gas and star density: Clumps having no associated clusters are classified as Type1, clumps showing good correlations with clusters are classified as Type2, clumps showing poor correlations with clusters are classified as Type3, and clusters with no associated clumps are classified as Type4. The Type2 clumps have a typical mass of ~103Msun and have morphologies that are similar to the clusters, suggesting that the clumps are in an early stage of cluster formation and the associated clusters are still embedded in an amount of gas and dust. We found that some of the Type2 clumps are infalling on the clump-scale to form clusters at the clump center, which should commonly occur in the beginning of cluster formation. We suggest that the clump + cluster systems should evolve from Type1 to Type4. To investigate this hypothesis in terms of chemical reactions, we examined the chemical compositions of the clumps by comparing the fractional abundances of the observed molecules with chemical models in literature. To our surprise, all of the clumps classified to Type1 are older than the Type2 clumps in terms of chemical compositions. We suggest that they are the Type1 clumps being gravitationally stable without collapsing for a long time due to the strong magnetic field. Type1 clumps younger than the observed Type2 clumps should be rare to find due to their short lifetime.
The detection of abundant cold methanol gas in the Small Magellanic Cloud
Shimonishi, Takashi
Observations of organic molecules in metal-poor systems will provide crucial information for understanding chemical processes in high-redshift galaxies where the metallicity was significantly lower than the present solar neighborhood. The Small Magellanic Cloud (SMC) is a nearby star-forming dwarf galaxy, whose metallicity is lower than typical Galactic values by a factor of five. We here report the first detection of a complex organic molecule, methanol (CH3OH), in the SMC based on submillimeter observations towards a high-mass young stellar object with ALMA. Besides CH3OH, we also detect the dust continuum as well as emission lines of CS, C33S, H2CS, SO, SO2, H13CO+, H13CN, SiO, and tentatively HDS from the observed region. The target infrared point source is spatially resolved into two dense compact sources; one is associated with an embedded high-mass young stellar object, another is not associated with an infrared source but shows rich molecular lines. The first detection of CH3OH in the SMC has a strong impact on the formation of complex organic molecules in metal-poor environments. The fractional abundance of CH3OH gas in the observed dense cloud is estimated to be (0.5--2) x 10^-8, which is comparable with those of similar Galactic cold sources despite a factor of five lower metallicity in the SMC. This would indicate an enhanced production or a suppressed destruction of gas-phase CH3OH in the observed SMC source compared to Galactic counterparts. The gas temperature is estimated to be about 10 K based on the rotation analysis of CH3OH lines, suggesting that non-thermal desorption would contribute to the production of the observed CH3OH gas. This work provides observational evidence that an organic molecule like CH3OH, which are largely formed on grain surfaces, can be produced even in a significantly lower metallicity environment compared to our Galaxy.
Current status of Japanese Virtual Observatory portal
Shirasaki, Yuji
Japanese Virtual Observatory (JVO) portal is a data service toseamlessly access to all the virtual observatory (VO) services,and also provide with dedicated search interface for Subaru,ALMA, Nobeyama and Gaia data sets.The VO search interface of the JVO portal has been updated toversion 2 since 2015. By this update the design of the four VOsearch interfaces were unified, and their usability was muchimproved,The Subaru, ALMA, and Nobeyama data search system provides with theWeb-based quick look system, FITS WebQL. Using this system users canview the data content on the web without downloading all theinterested data, which is useful before deciding which data to bedownloaded, especially for the case of large ALMA data (currentmaximum file size ~ 80 GB). Those data can also be found on theJVOSky, which is a GUI where users can search the data on the skymap like a google map.The Gaia data search system is build on a distributed databasesystem, which allows users to execute even the all sky queryon 1.6 billion of data.The JVO portal is accessible at jvo.nao.ac.jp/portal/.
Luminous Blue Variables candidates in M31
Sholukhova, Olga
We present the results of spectroscopic and photometric study of Luminous Blue Variable (LBV) candidates in the Andromeda galaxy. Six targets with optical spectra in M31 galaxy from Massey's list have been observed with the 6-m Russian telescope BTA from 2012 to 2015 in the optical range. The infrared spectra and photometric estimates in the IR bands were obtained with the 3.5-m telescope at the Apache Point Observatory. Using these data in combination with other archive photometric data we produce multi-epoch spectral energy distributions (SED) of these stars. Taking into account an inherent property of LBVs that their bolometric luminosity of LBV stars is constant, we use SEDs to determine the stellar temperatures and radii in different LBV states, as well as the extinction. We use these data to classify of the candidates into three subclass: LBVs or LBV-candidates, B[e]-supergiants and supergiants (dormant LBVs).
Sun, Solstice and Makar Sankranti: An Astronomical Significance in our Cultural Practice
Shrestha, Pritisha
In many cultures around the world, Sun is revered as life giving component on earth. People of the past have therefore created various celebratory festivals to mark the importance of the star. And one of such festivals is Makar Sankranti, which is celebrated in the region of Indo-Gangetic Plain. Unlike other festivals, it follows a solar calendar.Predominantly performed by Hindus, the festival marks a transition or transmigration of the sun from Sagittarius to Capricorn zodiacal constellation. To be more specific, the festival takes place when we have winter solstice and the sun moves from the Tropic of Cancer to the Tropic of Capricorn. What it predominantly indicates is that the people of the past were not only very observant of the celestial events, but also commenced festivals around such cosmic occurring. Therefore, my paper would propose that by studying such festivities at various cultural settings would arm scientific researchers further with the indigenous and cultural knowledge of astronomy. Furthermore, by bridging the gap between ancient practice and new findings, such intangible cultural heritages could additionally be given scientific back up as well as new research areas could be traced back to the past knowledge. I would be presenting the very significance of the annual festival in relation to astronomy education and how the cultural practice has been celebrated since the time immemorial. The second portion of the paper would focus on how the festival follows a solar calendar instead of lunar and what it implies.
Pecularities of super-Eddington flares from HMXB LMC X-4 with NuSTAR
Shtykovsky, Andrey
We present the results of analysis of high-mass X-ray binary LMC X-4 using the NuSTAR observatory data. We discuss pecularities appearing during pulsar switching into ultraluminous state (peak luminosity Lx ~ (2 - 4) × 1039 erg/s). The pulsar spectrum is well approximated by the thermal Comptonization model (comptt) both in a quiescent state and during flares. The order of magnitude increase in luminosity during flares is observed primarily at energies below 25–30 keV, whereas at higher energies (30–70 keV) the shape of the spectrum and the source flux remain practically unchanged. The pulse profile during ultraluminous increase of the pulsar luminosity in the energy range of 3–40 keV becomes approximately triangular, and the pulsed fraction increases with increasing energy, reaching 60–70 % in the energy range of 25–40 keV. We discuss possible changes in the geometry and properties of the accretion column, which can explain variations in spectra and pulse profiles.
Magnetic field effects on the ISM structure and galactic outflows
Shukurov, Anvar
We explore the effect of magnetic fields on the vertical distribution, multiphase structure and outflow of the gas and turbulence in simulations of interstellar medium (ISM) driven by supernova (SN) explosions. Magnetic field makes the ISM more homogeneous and reduces the fractional volume occupied by the hot phase. Magnetic pressure generally weakens systematic gas flow away from the mid-plane. Magnetic field strength is maximum at about the height |z| = 0.3 kpc above the mid-plane, and magnetic pressure gradient counteracts the outflow at the smaller heights and facilitates it above. The downward magnetic pressure gradient at |z| < 0.3 kpc leads to an almost uniform gas distribution along z near the mid-plane. The role of magnetic tension is weaker at the base of the halo than often assumed. Remarkably, an imposed magnetic field affects the ISM structure differently from a large-scale field generated self-consistently by the dynamo action: the dynamo magnetic field evolves together with the ISM and its effects on the gas are more diverse and subtle than those of an imposed magnetic field.
On the role of space-born UV instruments in search for hidden Warm and Hot Baryonic Matter in the near Universe
Shustov, Boris
As it now widely understood baryons are missing at all astronomical scales in Universe (see e.g. Nicastro 2014). Independent of the different models for the evolution of the Universe, the major baryonic component of the Universe must be associated with the intergalactic medium (IGM). About 30 to 50% of the baryons in the local Universe are in a hot phase and Warm-Hot Inter Galactic Matter (WHIM), and the dominant ions have their ground state resonance transitions in the UV and X-ray domains. Share of missing baryons in the local Universe (z = 2) is much higher than that in the more distant Universe. This is because the distant objects, which emit/absorb in UV, are observable in optical range due to cosmological shift. UV emitting/absorbing plasma (WHIM and Lya-absorbers) seems to be a major reservoir of missing baryons in the near Universe. To observe this gas we need space-born UV or X-ray instrument. A brief review of search for WHIM baryons with UV space instruments is presented. Special attention is paid to capabilities of the coming WSO-UV observatory. The observatory will be equipped with 170 aperture telescope, high resolution FUV and NUV spectrographs and FUV and NUV cameras. Relative contribution of X-ray and UV- instruments to revealing the missing baryons in the WHIM is discussed.
On the role of heavy elements loss in formation and maintaining radial metallicity gradients in disk galaxies
Shustov, Boris
We reconsider results of our early work [Wiebe, D. S.; Tutukov, A. V.; Shustov, B. M. Astronomy Reports, 2001], in which we summarized the influence of heavy elements loss in formation and maintaining radial metallicity gradients in disk galaxies. The major mechanisms of loss of heavy elements into the circumgalactic space are: (1) the expulsion of dust by stellar radiation pressure and (2) galactic wind. In both processes, the fraction of ejected heavy elements depends on the mass of the galaxy: e.g. low-mass galaxies eject matter more efficiently. Here we analyze recent progress on the topic. We discuss various origins for the formation of the heavy-element abundance gradients observed in nearly all disk galaxies in the framework of evolutionary models. We confirm that galaxy-IGM mass exchange processes play an important role in formation of the gradients especially at early stages of galactic evolution. This implies that typical disk galaxies with radial metallicity gradients are open systems not only in terms of infall but also in terms of mass loss.
Extended gaseous disks in S0 galaxies: why the star formation is anemic?
Silchenko, Olga
Despite the common opinion that lenticular galaxies are `red and dead', they often possess a noticeable amount of cold gas; and about a half of gas-rich S0 galaxies reveal some level of current star formation. However even those are falling usually below the star formation main sequence. We have tried to search for reasons why star formation in gaseous disks of S0s is so inefficient. We have observed a sample of gas-rich S0 galaxies with the scanning Fabry-Perot interferometer of the Russian 6m telescope and have mapped the ionized-gas velocity fields. Though regularly rotating, these velocity fields demonstrate often decoupled orientation of the angular momentum. The higher is the inclination of the gas rotation plane to the main stellar disk, the lower incidence of the current star formation is found. I discuss the origin and dynamics of the extended gaseous disks within several particular nearby S0 galaxies and restrict the conditions of the star formation triggering in these disks.
Early chemical enrichment of the Milky Way dwarf satellites from high-resolution and NLTE analysis of VMP stars
Sitnova, Tatyana
Current knowledge of the first stages of star formation in galaxies is still poor. The stellar abundance trends and dispersions of very metal-poor (VMP) stars reveal the nature of the first generations of stars, their masses, numbers, and spatial distribution, the energetics of the explosion of supernovae, and the level of homogeneity of the interstellar medium. The proximity of the Local Group dwarf spheroidal galaxies (dSphs) allows the derivation of chemical abundances with comparable quality as in the Milky Way (MW). The comparison of these galaxies with very different masses, star formation histories, and level of chemical enrichment can provide crucial information regarding the universality of the physical processes at play. We present the non-local thermodynamic equilibrium (NLTE) abundances of up to 10 chemical species in a sample of about 60 VMP (-4 < [Fe/H] < -2) stars in the seven dSphs and in the MW halo. Our results are based on high-resolution spectroscopic datasets and homogeneous atmospheric parameters. Once the NLTE effects are taken into account, the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax reveal a similar plateau at [alpha/Fe] = 0.3 for each of the alpha-process elements: Mg, Ca, and Ti, similarly to the MW halo. We put on a firm ground the evidence for a decline in alpha/Fe with increasing [Fe/H] in the Bootes I ultra-faint dwarf galaxy (UFD), that is probably due to the ejecta of SNeIa. The dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the classical dSphs, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr. Our three UFDs - Bootes I, UMa II, and Leo IV are depleted in Sr and Ba relative to Fe and Mg, with very similar ratios of [Sr/Mg] = -1.3 and [Ba/Mg] = -1 on the entire range of their Mg abundances. The subsolar Sr/Ba ratios of Bootes I and UMa II indicate a common r-process origin of their n-capture elements.
The prevalence and properties of ultra-diffuse galaxies in local clusters
Skelton, Rosalind
Ultra-diffuse galaxies (UDGs) are an unusual class of low surface brightness galaxies that have recently come into the spotlight for their low stellar masses (similar to those of dwarf galaxies) but large sizes and total masses much closer to those expected in a more massive galaxy, such as the Milky Way. How they form and remain intact within the strong tidal fields of the clusters they are typically found in remains unknown, but their locations and properties in relation to their larger-scale halos may provide clues. We present our results on the distribution of UDGs found in clusters in the relatively deep Stripe 82 region of the Sloan Digital Sky Survey. The clusters are selected from the redMaPPer catalogue out to z~0.2. A comparison of these diffuse low-mass galaxies with more typical dwarf galaxies in clusters may shed light on the processes affecting their evolution.
Phenomenon of the wave ordering and the diagram "mean density - global period" in the Solar planetary system
Skulskyy, Mykhaylo
The study of wave and gravitational factors that reflect the spatial characteristics of the Solar planetary system was conducted._x005F It is proved that the spatial structure of the Solar system can be reflected in two related algorithms of the same wave mechanism. The outer planets are located at distances from the Sun in accordance with a certain length of the standing wave. This algorithm is also valid and for well-known dwarf planets and comet families. The algorithm of the inner planets is ordered by the dependence in which the lengths of their orbits are in proportion to the same length of standing wave or its harmonics._x005F At the same time, it is detected that such a wave-space structure of the Solar System is connected to the global oscillations of the planets and Sun as a whole.This detected coherence of their global oscillations was studied taking into account the most massive satellites of planets and dwarf planets. All main objects of the Solar system have formed a clear functional relations between the periods of their global oscillations and their mean densities. Graphically, it is represented as a diagram "mean density - global period" which shows the ability of the self-organization in Solar planetary system. In particular, the planets and other groups of objects on this diagram are discretely ordered and the locations of many massive satellites of the planets are due to the effects of tidal forces._x005F Overall, the wave and gravity factors are represented in obvious interrelations and create an indivisible natural phenomenon. This generalized phenomenon does not look accidental leaving open the question of its origin and formation in the Solar planetary system and the options for its interpretation._x005F Key words: Solar system structure, wave ordering, means densities, global oscillations
X-ray binary Beta Lyrae and its donor component structure
Skulskyy, Mykhaylo
We propose an explanation of the steady state of X-rays of the massive interacting Beta Lyrae system – about 3 ?? for a donor and 13 ?? for an accretor. It was based on our spectral observations that led, in particular, to the study of the donor's magnetic field and the dynamics of developed circumstellar structures. Based on the analysis of magnetic field curves, curves of intensities and radial velocities of spectral lines with orbital phase we show that the mass transfer structure is having place due to the presence of a specific configuration of a magnetic donor field. The energy effect of a collision with the disk of a magnetized plasma increases greatly due to a rapid counter rotation of the disk rim towards the falling gas. As a result of such collisions, a significant heating of the disk side facing the donor is observed and the gas scattering shell is generated, which partially masks the components of this binary system outside of the Lyman limit and completely masks them in the soft X-ray region. This X-ray radiation is associated with Thomson scattering in a stellar wind and circumstellar jet-like structures. Considering Beta Lyrae as a system that is finishing an active phase of the first mass transfer and its donor fills a Roche lobe, we have calculated the inner structure of such star preceding a forming of massive degenerate dwarf. We have applied the two-phase model in which core of the donor is isothermal and degenerated and outer envelope is described with politropic equation of state with index range of 4.9 - 4.95. Angular velocity is assumed to be constant. By integrating the the equilibrium equation we have obtained the macroscopic characteristics of the degenerate core – its mass and radius, as well as size of the outer envelope. Also, we have solved the inverse problem – the parameters of the core have been found, namely, a parameter of relativism in the stellar center, a parameter of chemical composition and a central temperature.
Radio Morphology as a Probe of the Environment: the Radio Galaxy 3C 382
Slavcheva-Mihova, Lyuba
We present a study of the interaction of the radio structures in the FR II BLRG 3C 382 with the environment.According to colour maps and 2D decomposition of the optical images, 3C 382 is E or S0 galaxy. There is a couple of filaments to the northeast-east (NE-E), another one to the south (S), and a complex of arcs in the circumnuclear region that all appear blue. The NE filaments manifest a notable match with the radio structure and the S filament traces the location of the opposite lobe displacement.The velocity of the warm absorber outflow in 3C 382 is of the order of 103 km s-1. The jet Eddington ratio exceeds the critical one regarding feedback. Thus, not only positive feedback is not expected, but the jet, driving the outflow, meets the criterion for an effective negative feedback.There is an object at the origin of the S filament that is most probaby a star. Besides, a galaxy is closely projected to the N hotspot. The redshift derived from our optical spectra shows that it is a physical companion.The hotspot spectra on both sides of 3C 382 are similar giving rise to the idea of a single injection spectrum. We suggest that the NE filament gas interacts with the jet and deflects it; light jets can be easily bent by diffuse medium. The S filament, on its turn, interacts with the backflowing plasma of the opposite lobe and causes its offset. The disturbed features in the galaxy are of tidal origin. The filaments represent gas stripped off the companion or/and resident in the body of 3C 382 in the course of interaction. Both the bar and disturbed spiral structure of the companion may be induced by the interaction with 3C 382.The lifetime of such tidal features is of order of a few 108 yr up to 109 yr, while FR II jet lifetime is up to about 108 yr. Thus, it is reasonable for the filaments to precede the jet, which makes this scenario viable. This may also mean that the interaction with the companion can be related to the onset of nuclear activity of 3C 382.
Towards the search of the difference in physical and dynamical properties between the L4 and L5 swarms of Jupiter Trojans
Slyusarev, Ivan
From the beginning of the study of Jupiter Trojans, there is a well-known difference in number of objects between L4 and L5 groups. For a long time, this difference has been attributed to the observational selection effect. However, as the number of discovered Trojans increase, L4 Trojans the difference become even more noticeable. At present, there are 4599 objects known in L4 and 2433 in L5 population, i.e. L4 Trojans are more numerous than L5 in 1.9 times. We found that the shape of the orbital inclinations distribution in the L4 and L5 swarms are also different (Slyusarev 2013). The L5 population shows significantly wider distribution with a plateau in the range from 5° to 17° and a weak maximum at 27°. The distribution of the L4 population demonstrates a sharp maximum at 7°, after which the number of Trojans with specified inclinations decreases exponentially. These two manifestations of asymmetry in the L4 and L5 swarms weren't explaned yet. The asymmetry of L4 and L5 swarms is difficult to explain basing on dynamical models. We search for possible differences in physical parameters between Trojans belonging to the L4 swarm and to that belonging to L5 swarm using our own observations and literature data.
A Predicted Astrometric Microlensing Event by a Nearby White Dwarf
Smart, Richard
We used the Tycho-Gaia Astrometric Solution catalogue, part of Gaia Data Release 1, to search for candidate astrometric microlensing events expected to occur within the remaining lifetime of the Gaia satellite. Our search yielded one promising candidate. We predict that the nearby DQ type white dwarf LAWD 37 (WD 1142-645) will lens a background star and will reach closest approach on November 11th 2019 (± 4 days) with impact parameter 380 ± 10 mas. This will produce an apparent maximum deviation of the source position of 2.8 ± 0.1 mas. In the most propitious circumstance, Gaia will be able to determine the mass of LAWD 37 to ~3%. We discuss this event and other work we are carrying out in preparation for the Gaia mission.
Chemical abundances of Gaia-ESO metal-poor stars compared to stars in dwarf galaxies
Smiljanic, Rodolfo
Some of the Galactic metal-poor stars likely originate from stellar systems that have been accreted by the Milky Way. These systems include dwarf spheroidal galaxies. It has been shown in the past that stars in these systems can have distinct [alpha/Fe] vs [Fe/H] trends when compared to the general stellar population of the Galaxy (e.g., Venn et al 2004). In particular, because of a different chemical evolution history, low-[alpha/Fe] ratios are present in stars of lower metallicity than in the Milky Way. It has also become clear that the Galactic halo contains a fraction of stars that has likely been accreted (e.g., Smiljanic et al. 2009). In this work, we compare the chemical abundances of a sample of Galactic metal-poor stars with abundances of stars in dwarf spheroidals. The Galactic stars have been observed within the Gaia-ESO spectroscopic survey. Data for stars in dwarf spheroidals are taken from the literature. Based on the chemical abundances, we identify a subsample of Galactic stars that could have been accreted from external systems. We present an overview of other stellar properties (e.g., kinematics) that might support or reject the accretion hypothesis for these stars.
The dynamics of the ionized gas associated with the SMC Cluster NGC 346
Smith, Linda
The young resolved cluster NGC 346 in the SMC provides us with the opportunity to study the details of cluster formation and the efficiency of feedback mechanisms at low metallicity. We present high resolution (7 km/s) spectroscopy of the ionized gas, and find that the gas is largely quiescent over the extent of the ionized region N66. We find that some of the young sub-clusters are associated with broad emission-line components and discuss their origin. Overall, we find that the winds of the cluster O stars are not sufficient to clear N66 of gas and that stellar radiation is the dominant process shaping the interstellar environment of NGC 346.
Updates to the SDSS $u'g'r'i'z'$ Standard Star Network
Smith, J. Allyn
We present an update to the Sloan Digital Sky Survey (SDSS) u'g'r'i'z' standard star network. This system was orginally published in 2002 and was developed to support the SDSS. The initial system contained about 150 stars in the northern hemisphere and around the equator. Since then, we have enhanced the network with the inclusion of some fainter northern and equatorial stars and a fully developed set of standards in the southern hemisphere. The southern extension has been available for nearly 12 years, though only via electronic download. We include plans for the release and publication of the system. These stars were used as part of the initial calibration of the Dark Energy Survey and the upcoming release is made timely by the upcoming LSST project which will use similar filters.
Efficient sub- and super-Nyquist frequency-identification in Kepler delta Scuti and gamma Doradus stars
Sódor, Ádám
We compare the performance of different frequency-identification methods suitable for coherently pulsating variable stars, such as, but not only, delta Scuti and gamma Doradus stars. We show that all methods perform equally well in identifying significant frequencies, however, with tremendous difference in computing resource costs, that is, time demand. We prove that the CLEAN algorithm is capable of reliably identifying significant frequencies and corresponding amplitudes and phases with precision equal to classical hybrid time- and frequency-domain prewhitening methods, however, orders of magnitude faster than any other method. We also find that the CLEAN algorithm is capable of performing reliable super-Nyquist frequency identification on sufficiently long Kepler data sets. We investigate and discuss the issue of extracting significant spurious peaks from strongly multiperiodic space photometric data. We offer a solution to mitigate this problem.
HST Proper Motions of Dwarf Galaxies in the Local Group
Sohn, Tony
The universe evolves hierarchically with small structures merging and falling in to form bigger structures. Due to its proximity, the Local Group (LG) is the best place to study these hierarchical processes in action. Stellar systems in the LG have therefore become the benchmark for testing several aspects of cosmological theories. Despite the advancements in both observational and theoretical grounds in the past decade or so, many fundamental properties (e.g., total mass and mass profiles) of the LG galaxies and their satellites remain poorly constrained primarily due to the limited information on their transverse motions. Our HST studies are making significant progress in this field by measuring proper motions with unprecedented accuracies. I will present our past and ongoing HST projects for measuring absolute proper motions of dwarf galaxies in the Local Group. I will also discuss the synergy between HST and Gaia as astrometric instruments in the coming years.
Kalman filtering as a novel approach to determine celestial reference frames
Soja, Benedikt
The conventional approach to determine celestial reference frames (CRFs) is by estimating constant radio source coordinates in a least-squares adjustment. However, several radio sources exhibit coordinate variations that go beyond the traditional constant coordinate model considering nowadays’ growing accuracy requirements. Since it is currently very difficult to correct for the effects causing such variations (e.g., source structure) on the observational level, we have decided to use a time series representation of the radio source coordinates that constitute our CRF solutions. We treat radio source coordinates as stochastic processes and estimate them in a Kalman filter and smoother. The selection of the process noise model, which regulates the temporal variations of the resulting time series, is essential in the application of Kalman filtering. We test different approaches to derive the process noise model, for example based on the variability of the source flux and the jet direction. We compare the Kalman filter CRF solutions with traditional ones by assessing their performance in the VLBI data analysis, in particular concerning the estimated source coordinates and nutation parameters.
Cycle-dependent and cycle independent surface tracers of solar magnetic activity
Sokoloff, Dmitry
We consider several tracers of magnetic activity that separate cycle-dependent contributions to the background solar magnetic field from those that are independent of the cycle. The main message is that background fields include two relative separate populations. The background fields with a strength up to 100 Mx cm$^{-2}$ are very poorly correlated with the sunspot numbers and vary little with the phase of the cycle. In contrast, stronger magnetic fields demonstrate pronounced cyclic behaviour. We discuss how this result can be included in the above-mentioned concepts of solar dynamo studies. Small-scale solar magnetic fields demonstrate features of fractal intermittent behavior, which requires quantification. We investigate how the observational estimate of the solar magnetic flux density B depends on resolution D in order to obtain the scaling $\ln BD = - k \ln D +a$ in a reasonably wide range. The quantity k demonstrates cyclic variations typical of a solar activity cycle. $k$ depends on the magnetic flux density, i.e. the ratio of the magnetic flux to the area over which the flux is calculated, at a given instant. The quantity a demonstrates some cyclic variation, but it is much weaker than in the case of $k$. The scaling is typical of fractal structures. The results obtained trace small-scale action in the solar convective zone and its _x005F coexistence with the conventional large-scale solar dynamo based on differential rotation and mirror-asymmetric convection. The research is supported by RFBR projects 18-02-00085 and 17-02-00300. By D.D.Sokoloff, V.N.Obridko, I.M.Livshits, A.S.Shibalova.
The XIIIth General Assembly of the IAU in Prague, inauguration of the Ondrejov 2-m telescope and the Prague Spring 1968
Solc, Martin
The XIIIth General Assembly of the IAU took place in Prague on August 22-31, 1967. For the second time, astronomers from more than 30 countries met on the eastern side of the iron curtain (for the first time it was in Moscow, 1958). This honour was influenced not only by the astronomical tradition of Prague – Brahe, Kepler, Doppler, Mach, Einstein – but also by the contribution of Czechoslovak astronomers to the development of astronomy since the first years of IAU. On August 23, the new 2-metre Zeiss telescope was officially opened in the presence of the IAU officers and representatives of Czech scientific, state and political institutions. The history preceeding this act will be discussed on basis of the archive documents.The IAU president for 1964-1967, Prof. Paul Swings (Belgium), was succeeded by Dr. Otto Heckmann from West Germany. The new secretary was Dr. Lubos Perek (Czechoslovakia) and the Vice-presidents were from Argentina, Czechoslovakia, India, Italy, USA, USSR and West Germany. This successful IAU meeting enabled Czechoslovak astronomers to foster better worldwide contacts and helped to politically liberate Czechoslovak science generally.
Performance Update on EtaGen, an Event Trigger Generator based on the Hilbert-Huang Transform
Son, Edwin J.
An event trigger generator based on the Hilbert-Huang transform, named ?Gen (EtaGen), has been introduced at 29th IAUGA in 2015. The original ?Gen requires large amount of computational cost due to the ensemble empirical mode decomposition (ensemble EMD, EEMD) that is used to obtain reliable intrinsic mode functions. In the current version of ?Gen, we replace EEMD with the weighted sliding EMD, an online EMD algorithm, which reduces the computational cost without noticeable loss of the virtue of EEMD. In addition, we introduce a waveform reconstruction algorithm in ?Gen to improve the estimation of SNR.
Astronomy Outreach Activities in Uruguay
Sosa, Andrea
Uruguay is a small country, in the southern-east part of South America, with a valuable tradition in Astronomy education and outreach, as well as in research on planetary sciences. In this poster I present some of the most remarkable outreach activities recently done, in progress, or to be done during 2018. As an example, on September 2, 2016, was inaugurated the Astronomical Observatory of the “Centro Universitario Regional del Este”, in Rocha, under my responsibility. This is the only university observatory in Uruguay, and is devoted to support educational courses on Astronomy for school and highschool teachers, to perfom some research projects for students and teachers, and to coordinate public activities for the observation and explanation of astronomical events. We teach courses on fundamental astronomy, astro-photografy (with and without telescope) for general public, and most recently, we colaborate in a course on archeo-astronomy, and on the rol of Astronomy in Culture. We also continue promoting the public awareness about preserving the darkness of the night sky.There are of course other institutions in Uruguay that contribute to outreach, like the Department of Astronomy at the Faculty of Sciences in Montevideo, the Municipal Planetarium of Montevideo, the Observatorio of Montevideo (which belongs to Secondary Education), the “Inspeccion Nacional de Astronomia”, the Amateur Asociation of Astronomy, the Uruguayan Astronomical Society “Sociedad Uruguaya de Astronomia”, etc. Since Astronomy is still a program course in the schools and highschools, some teachers also contribute to outreach, by doing activities with their students beyond the program.This poster paper is intend to present an actual and comprehensive review of the specific national activities of the main institutions and individuals involved in Astronomy Outreach in Uruguay, supported on statistical and cuantitative data, with some evaluation of the present and future impact of such activities.
Dynamical evolution of comet pairs
Sosa, Andrea
Some Jupiter family comets in near-Earth orbits (thereafter NEJFCs) show a remarkable similarity in their present orbits, like for instance the comets 169P/NEAT and P/2003 T12 (SOHO), or the comets 252P/LINEAR and P/2016 BA14. By means of numerical integrations we studied the dynamical evolution of these objects. We integrated the orbits of the objects plus 1000 clones for each one of them, for 10,000 years in the past and in the future. We found that 169P and P/2003 T12 move on stable orbits for the past 10,000 years, avoiding very close encounters with Jupiter, in good agreement with Fernandez and Sosa 2015 ( Planetary & Space Science 118, pp. 14-24). By the contrary, we found that 252P and P/2016 BA14 move on highly unstable orbits, with frequent very close encounters with Jupiter. For 169P and P/2003 T12 we found some well defined minima of their relative spatial distance, almost coincident with a minimum of their relative velocity. In order to study if a breakup of a parent body could be the most probably origin for this comet pair, we simulated the orbital evolution of hypothetical fragments of 169P. Our aim is to reproduce the actual orbit of P/2003 T12 by modeling a fragmentation of 169P. Might be exist several causes for the fragmentation of the parent body, like thermal stress, rotational instability, collisions, or tidal forces if the object pass too close to a masive body (like the Sun or Jupiter). Some of the main model parameters are the relative ejection velocity (a few m/s), the orbital point at what the fragmentation could have happened (e.g. perihelion), and the elapsed time since fragmentation. Tentative values for this last parameter were based in the minima of the relative distance and velocity that we found in the past dynamical evolution of the comet pair. The robustness of the results are also evaluated.
The temporal evolution of neutron-capture elements in the Galactic discs
Spina, Lorenzo
Important insights into the nucleosynthetic history of elements are contained in the chemical compositions of stars. In this talk I will review the results obtained from the high-precision abundance determinations of 12 neutron-capture elements over a sample of 79 solar twin stars. This valuable dataset allowed us to study the [X/Fe]-age relations over a time interval of 10 Gyr and among stars belonging to the Galactic thin and thick discs. These relations showed that the s-process has been the main channel of nucleosynthesis of n-capture elements during the evolution of the thin disc, while the thick disc is richer in r-process elements due to its rapid and intensive formation. In addition, abundances of the heavy (Ba, La, Ce) and light (Sr, Y, Zr) s-process elements revealed important details on the dependence between the yields of AGB stars and the stellar mass or metallicity.
Chemical signatures of rocky accretion in young solar-type stars
Spina, Lorenzo
It is well known that newly formed planetary systems undergo processes of orbital reconfiguration and planetary migration. As a result, planets or protoplanetary objects may accrete onto the central star, being fused and mixed into its external layers. Such dramatic events may result in a modification of the chemical composition of the stellar photosphere in an observable way, enhancing it with elements that were abundant in the accreted mass. Open clusters are groups of stars that formed from the same nebula and started as chemically homogeneous, thus they are the ideal targets for the identification and the study of chemically anomalous stars that may have accreted planets. In this talk I will review our recent results on the chemical content of five solar-type members of Pleiades. Our analysis has revealed that chemical anomalies exist among these cluster members and that the abundance differences between the members are correlated with the condensation temperature. This finding strongly supports that planet engulfment events are frequent among Sun-like stars.
Innovators Developing Accessible Toools for Astronomy (IDATA)
Spuck, Timothy
Perhaps you have seen those spectacular images from the Hubble Space Telescope: pillars of greenish gas and dust giving birth to new stars and planets, incredibly detailed spiral arms in galaxies millions of light-years away, but you can’t look through a telescope and see these amazing wonders of nature. Light from these distant objects is converted into numerical data and computers use that data to generate the images we see. In reality, in many ways, we are all blind to this data. We simply choose to convert these numbers into images, but there are other ways, beyond our eyes, to analyze this data. IDATA, a United States National Science Foundation-supported project explores computational thinking and learning in astronomy and the impact of engaging students in authentic software design/development, invents blind and visually impaired (BVI) accessible image/data analysis software, and develops curricular resources to support computation in astronomy explorations and software use. Come learning about the project and how you can access these resources when they are made available.
Astronomy in Chile Educator Ambassadors Program
Spuck, Timothy
ACEAP is a collaboration between AUI, the National Radio Astronomy Observatory, AURA, National Optical Astronomy Observatory, and Gemini Observatory, and is supported by the United States National Science Foundation. The Program brings amateur astronomers, planetarium personnel, and K-16 formal and informal astronomy educators to astronomy facilities in Chile. While at these facilities, ACEAP Ambassadors will receive extensive training about the instruments, the science, data products, and communicating science, technology, engineering, and mathematics (STEM) concepts. When they return home, the Ambassadors will share their experiences and observatory resources with schools and community groups across the US. The program is creating a unique newtwork of excellent astronomy educators in formal and informal education to amplify the voices of the observatories creating an informed citizenry at home and abroad.
The search for black holes and black hole binaries using GPU accelerated supercomputers
Spurzem, Rainer
Black Holes are difficult to detect through electromagnetic radiation alone. Indirect evidence for their existence in our universe has been accumulated on a large range of black hole mass scales (supermassive in galactic nuclei, stellar in X-ray binaries and most notably recently by direct gravitational wave detection through LIGO/Virgo). Intermediate mass black holes may exist too, but remain the most speculative variety of their kind. Recently, gravitational waves from coalescing stellar mass black holes have been detected by the LIGO instruments. This is considered a first direct evidence of the existence of black holes and their binaries. In our team we have been working on the interaction of black holes on all mass scales with stellar clusters surrounding them - globular and nuclear star clusters with stellar mass black holes and galactic nuclei with supermassive ones. We study with some of the largest possible computer simulations (direct N-body simulations on GPU accelerated parallel supercomputers) realistic star clusters including a full stellar population (singles and binaries). Ultimately compact black hole binaries form, and with Post-Newtonian general relativity (if needed) we follow how they evolve, disrupt stars, and emit gravitational waves. The talk will give an overview of simulations, methods used and results obtained. Astrophysical topics are for example the ``detection'' of black hole mergers like observed by LIGO in our N-body models; we derive the expected gravitational wave spectrum and waveforms of black hole mergers happening in our computer model and compare it to the observed ones by LIGO. The results give us (with still high uncertainties) clues about the possible origin of observed LIGO events.
Modelling circumstellar gas and dust in Magellanic Cloud and Galactic carbon stars
Srinivasan, Sundar
Carbon is one of the most crucial products of AGB nucleosynthesis; AGB stars with initial masses in the range 1--4 Msun transport it into their outer layers via third dredge-up, eventually turning in C--rich AGB stars. After carbon monoxide, acetylene (C2H2) is one of the most abundant species in these shells, and it is the starting point for the synthesis of more complex hydrocarbons, and is also important for dust formation.Gas close to the photosphere is detected in near- and mid-IR spectra as deep absorption bands, which progressively weaken as emission from the increasing dust content fills in these features. The presence of C2H2 absorption on top of the dust continuum challenges this scenario however, suggesting that dust formation does not consume all available complex molecules, and that significant quantities of such molecules exist well outwards of the dust-formation radius. The absorption features are deeper at lower metallicities -- dusty Magellanic Cloud carbon stars show more prominent absorption than their Galactic counterparts, and simple models indicate a correlation between the dust-production rate and the column density of the circumstellar gas (e.g., Matsuura et al. 2006).We have analysed the Spitzer spectra of all the carbon stars in the Large and Small Magellanic Cloud, as well as in the Galaxy, by simultaneously modelling the dust spectrum and the gas absorption features. This allows us to investigate correlations between the various gas and dust parameters (e.g., the C2H2 column density and excitation temperature, and the dust-production rate) in a statistically significant sample. In addition, the large dataset allows us to probe any differences due to metallicity.
Modelling dust in the Nearby Evolved Star Survey (NESS) targets
Srinivasan, Sundar
The Nearby Evolved Stars Survey (NESS) is a multi-telescope project targeting a volume-limited (d < 2 kpc) sample of $\sim$400 evolved stars. NESS includes a 500-h ongoing JCMT survey of dust continuum as well as CO (2-1) and (3-2) line emission. The NESS sample includes XX oxygen-rich and YY carbon-rich AGB stars, as well as ZZ red supergiants, and many post-AGB stars and planetary nebulae. The NESS JCMT data facilitate the determination of the circumstellar dust distribution and estimation of the mass-loss history in the circumstellar shells, including any deviations from spherical symmetry (Dharmawardena et al., in prep). Radiative transfer models of this dust must update fits to mid-infrared spectral energy distributions (SEDs) to fit the far-IR and sub-mm information, and should reproduce the results from JCMT observations.In this poster, we present preliminary results of modelling dust in W Hya and U Ant. [W Hya information here]. NESS data has also revealed U Ant's detached shell for the first time in the sub-mm continuum. We first fit the mid-IR SEDs with models from the GRAMS grid (Sargent et al., 2011; Srinivasan et al., 2011), tacitly assuming spherical symmetry. Using these models as a starting point, we use the radiative transfer code 2Dust to explore ranges of parameters that will reproduce the radial profiles as determined by Dharmawardena et al. (in prep), including any evidence of detached shells and/or variable mass-loss rates.These models are the first step towards detailed modelling that incorporates data from optical through sub-mm SEDs and spectra, as well as other data such as interferometric visibilities. Modelling the large number of AGB stars targeted by NESS will lead to robust estimates of dust-production rates across the entire range of evolutionary stages along the AGB. Combined with modelling of the NESS CO line data, these can also be used to determine the gas-to-dust ratio throughout the circumstellar shell for the entire sample.
The angular momentum distribution and history of the Local Group as seen by the HESTIA simulations
Steinmetz, Matthias
HESTIA (High-resolution Environmental Simulations of The Immediate Area) is a large-scale simulation project to study the properties, formation and evolution of the Local Group and its galaxies including the effects of gravity, gas dynamics, magnetic fields, cosmic rays and state-of-the-art models for feedback by late stages of stellar evolution as well as by supermassive black holes. The initial conditions are constrained by the local velocity field as derived from the CosmicFlows3 survey and by the positions and masses of prominent local features such as the Virgo and Coma galaxy clusters. We will present some first results on the angular momentum distribution and history of the group and its galaxies and how that compares with the analogue features in less special environments. Furthermore we will adress the alignments of angular momentum with the local cosmic web and its implication on the emergence of vast planes of satellites.
Solar soft X-rays spectroscopy using Bragg crystals
Steslicki, Marek
After years of intense studies, the basic physical processes of energy release in the plasma of solar corona are still not well known. During a flare, magnetic energy in the corona is released through drastic restructuring of the magnetic field via reconnection. Electrons and ions are then accelerated by yet poorly understood processes. The most promising tool allowing the study of physical conditions in the energetic coronal sources is spectroscopy. In the multi-million degree solar corona, the atoms are highly ionized, up to the helium- and/or hydrogen-like ionization stages. Hot plasma contribute to emission spectra in the range between 0.1 and 5 nm, i.e. the soft X-ray range. Observed line profiles depends on local plasma conditions prevailing in active regions and flares (T in the range between 1 and 50 MK). Spectral information completed by Dopplerometry, and possibly polarimetry, constitute a powerful tool to diagnose the properties of the hot plasma in the atmosphere of our star. In this context, we present a space instruments SolpeX and ChemiX currently under development at the Space Research Centre of Polish Academy of Sciences designed to observe in detail properties of the solar soft X-ray spectra.
The effect of ram pressure on Dwarf Galaxies
Steyrleithner, Patrick
Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral galaxies passing through the hot inter-galactic medium of galaxy clusters. Since the dominant morphological type of dwarf galaxies (DGs) in clusters is provided by the gas-free early-type DGs these must have suffered gas evacuation already long ago. This process can, however, not be observed at DGs in the denser cluster region, because for low-mass DGs it must happen already in the outskirts of clusters. While this was difficult for a long time, since the last decade such DGs in ram-pressure transformation are in fact observed by a few objects in close-by galaxy clusters.Although for DGs this RPS process sounds analytically simple, a wide range of various structures is observed from the total gas evacuation to partial gas stripping, respectively. In contrast to the RPS in massive spiral galaxies star formation (SF) occurs in stripped gas clouds of DGs. In addition, SF seems to be partially enhanced by the ram pressure exerted on DGs. Moreover, some early-type DGs within clusters contain blue cores, witnessing recent SF, or could even retain dense gas in their centers.From all these facts several questions must be addressed, as e.g., when, where, and how the gas is stripped-off from DGs, how the interstellar medium (ISM) in DGs is affected by the ram pressure, how gas-rich DGs are already influenced when they move through low-density inter-galactic gas, and further more.By numerical simulations of the RPS acting on DGs, applying the massively parallel AMR code FLASH, we aim at answering the above-mentioned questions and at investigating the gas loss by ram pressure, its effect on the gas within DGs, e.g. by compression, and on the SF in the retained ISM and in the stripped gas clouds.For this, we not only compare the evolution of RPS-affected DGs with models of isolated DGs, but also discuss the physical causes that either trigger of prevent SF in the stripped-off clouds.
Observing high-redshift dwarf galaxies with JWST
Stiavelli, Massimo
We have carried out high resolution numerical simulation to study the formation of pristine and metal poor galaxies before the reionization era in order to make observability predictions for the James Webb Space Telescope.
Using mHz QPOs to put constraints on neutron star size and equation of state
Stiele, Holger
4U 1636-536 is a well-studied LMXB, consisting of a neutron star (NS) in a 3.8 hr orbit with a companion star of about 0.4 solar masses. Showing the full range of rapid time variability, 4U 1636–53 is an ideal source for studying nuclear burning on the surface of a NS._x005F We performed a variability study of archival XMM-Newton data of 4U 1636-536 and investigated the energy dependence of its low frequency variability. Here we present the results of our waveform analysis and phase resolved spectral investigations of the mHz quasi-periodic oscillations (QPOs). Our study showed that the oscillations are not caused by variations in the blackbody temperature of the NS, but revealed a correlation between the change of the count rate during the mHz QPO pulse and the spatial extent of a region emitting blackbody emission. The maximum size of the emission area allowed us to obtain a lower limit on the size of the NS that rules out equations of state that prefer small NS radii. Up-coming NICER data will allow us to reduce the statistical uncertainty in the lower limit on the NS radius, which together with better estimates of the hardening factor and distance, will allow for improved discrimination between different equations of state and compact star models.
The Search for Intermediate Mass Black Holes in Dwarf Galaxy Mergers
Stierwalt, Sabrina
Massive black holes in today's dwarf galaxies offer a unique window into not only the typical masses of early black holes and the properties of the galaxies that host them, but also how these seeds may have formed. Mergers among massive galaxies are observed to fuel central AGN but whether or not this process happens at lower masses in dwarf-dwarf interactions is unknown. I will present the latest results from the TiNy Titans survey of interacting dwarf galaxies to determine whether interacting dwarfs can harbor and fuel their own active massive black holes.
A JWST ERS Study of the Starburst-AGN Connection in Merging LIRGs
Stierwalt, Sabrina
Galaxies evolve through a combination of secular processes, such as cold gas accretion, and nonsecular processes, such as galactic mergers, which can trigger massive starbursts and powerful AGN. JWST will transform our understanding of galactic evolution, providing a detailed look at the physics of star formation and black hole growth in nearby merging galaxies. By using NIRSPEC, NIRCAM and MIRI, our ERS program will provide a rich dataset for understanding the dynamics and energetics of the ISM on scales of 50-100pc in the nuclei of local Luminous Infrared Galaxies (LIRGs). Our four targets (NGC 3256, NGC 7469, VV 114, and IRAS 08572+3915) cover a range of starburst-to-AGN power, merger stage, and IR spectral properties. I will summarize our ERS program science goals for unraveling the complex galactic ecosystems in active and starburst galaxies at low redshifts and our plans for science-enabling data products. Co-Author: Lee Armus (Caltech) and the GOALS ERS Team
CHANG-ES - an overview
Stil, Jeroen
CHANG-ES (Continuum Halos in Nearby Galaxies - and EVLA Survey) is a survey of 35 nearby edge-on galaxies with the JVLA in L band (B, C, and D configuration) and C band (C and D configuration) in all four Stokes parameters. Science goals include the origin of radio halos in galaxies, magnetic fields at the interface between disks and halos, cosmic ray transport, the far-infrared-radio correlation, and large-scale magnetic field structure in the halos of galaxies. On this poster we introduce the survey on behalf of the CHANG-ES team, and present a selection of results from the survey so far.
Star Clusters and Young Populations in the Leo A Galaxy
Stonkute, Rima
We have studied young stellar populations and star clusters in the dwarf irregular galaxy Leo A using multicolour photometry data obtained with the Subaru Telescope and HST ACS. Analysis of the main sequence and “blue loop” stars allowed us to determine the star formation history in the Leo A galaxy during the last 500 Myr. Also, we have discovered numerous star clusters in the main body of the Leo A galaxy. The colour-magnitude diagrams and integrated photometry data of the newly discovered star clusters were used to study cluster population in the Leo A galaxy.
Envidence for discrete star formation events in the Small Magellanic Cloud based on 6.5m Magellan Telescope observations
Strantzalis, Achilles
The Small Magellanic Cloud (SMC) is a nearby gas rich dwarf irregular galaxy and interacts both with its neighboring Large Magellanic Cloud and with the Milky Way. Due to its relatively small mass (~ 10-2 MMW ) and inter-galaxy interactions, it has an interesting star and cluster formation history as well as a complex geometry. The SMC presents us with a unique opportunity to study in detail quenching as seen from stellar populations and galactic archeology, as well as the effect of environmental processes (interaction with the LMC and the Milky Way) on star formation processes. With the 6.5m Magellan Telescope at the Las Campanas Observatory in Chile we have acquired multi-filter observations (B, R, I) in four 0.44o fields covering the entire area of the main body of the SMC, yielding accurate photometry for 1,068,893 stars down to ~24th magnitude, with a spatial resolution of 0.201 arcsec/pixel. Colour-magnitude diagrams and luminosity functions (corrected for completeness) have been constructed, yielding significant new results that indicate at least three discrete star formation events over a period from 0.1 to 4 Gyr ago.Additionally, exploiting the high spatial resolution and large extent of this survey we have applied an automated statistical technique in order to identify star clusters (thus allowing verification of the cluster nature of previously published clusters and the discovery of new ones) and study their characteristics (structural parameters and ages).
Time Domain Studies of High-Mass X-ray Binaries
Stringfellow, Guy
Work in progress on the time domain studies of HMXBs will be presented. Multi-filter optical imaging over a range of cadences from minutes to years are being conducted on several key HMXBs, including those believed to harbor black hole companions, to ascertain how variable/stable the systems are. Additionally, moderate-to-high-resolution optical and near-infrared spectroscopy are being obtained. These combined datasets will yield new insights into the orbital interaction behavior of the high-mass primary, compact secondary, and any disk formed/dissipated (when present) and their associated accretion/disk activity over time. Light curves and spectral analysis will be presented.
Low Frequency Radio Spectrometer on board Chinese CE-4 lunar lander
Su, Yan
Low Frequency Radio Spectrometer(LFRS) is a scientific paylad hosted by the Chinese Chang'e-4 (CE-4) lunar lander, expected to be launched in 2018. The main mission consists of three parts, a relay around the Earth-Moon L2 point, a lander and a rover on the far said of the Moon. The LFRS is a low frequency radio instrument that serves as a pathfinder for space-based exploration. Its frequency range is 100kHz up to 40MHz. As quiet radio zone of the far side of the moon preventing from Earth's ionosphere and interference from the earth, its sciences goals include observing solar activities and Characterizing the radio interferences environment around the moon. The LFRS system consists of three 5m long monopole antennas mounted at the outer wall of the lander connected to a low noise amplifier and a digital receiver system. Cross-correlating signals from all polarization could be captured. The analogue signals are fed into three high-resolution (14 bit, 100 M samples per second) analogue to digital converters. EMC tests have been done and there is strong self-generated interference originating from the lander unfortunately, one 20cm short dipole is designed to measure the background interference. It is expected to reduce the noise by approaches correlating signals to extent. If this problem could be sorted out successfully, the LFRS could cover wider science cases that include observing Jupiter, pulsars even dark ages signal.
What are the implications of stellar chemical abundances in dwarf galaxies?
Suda, Takuma
Chemical abundances of stars provide us with rich information on the star formation history and the chemical evolution of the universe. Thanks to the many efforts to derive the abundances of individual stars in dwarf galaxies, it is possible not only to compare them with those in the Milky Way but to compare among dwarf galaxies in the local group. We have constructed a database of stellar abundances in the local group dwarf galaxies by extending the existing database for Milky Way stars (The Stellar Abundances for Galactic Archaeology database, sagadatabase.jp, see Suda et al. 2008, PASJ, 60, 1159). We analyzed the data in the new database, which contain more than 6000 stars in 24 dwarf galaxies together with more than 4500 stars in the Milky Way. The large dataset of stellar abundances enables us to explore the characteristics of dwarf galaxies with various approaches. In this presentation, we elaborate our analyses on the chemical abundances of stars in the local group dwarf galaxies and discuss the constraints on their origins. Our statistical approach provides a hint to inspect the star formation history of individual galaxies, using cumulative metallicity distribution functions. In addition, the compilation of all the available data on the abundances of carbon and neutron-capture elements has revealed the variations of the population of carbon-enhanced metal-poor stars, which gives an important insight into our understandings of the chemical enrichment history of galaxies. The inspection of the relationship between Eu and Ba abundances confirms an anomalously Ba-rich population in Fornax, which indicates a pre-enrichment of interstellar gas with r-process elements. We also checked the anti-correlations in O–Na and Mg–Al abundances to see a similarity with the Galactic globular clusters, which results in no evidence of the abundance anti-correlations in any dwarf galaxies. (Reference: Suda et al. 2017, PASJ, 69, 76)
An X-ray study of Wolf-Rayet binaries
Sugawara, Yasuharu
We present the results from the X-ray spectral analysis of the WR+O colliding wind binaries. Wolf-Rayet binaries represent an important stage in the evolution of massive binary systems. In addition, some colliding wind binaries show periodic infrared excess, indicating periodic dust formation. These winds affect the circumstellar environment. The X-ray spectrum is the best measure of conditions in the hot postshock gas, and the crucial time for observations is around periastron passage when densities and emitting volume are changing most rapidly. We performed the X-ray spectral analysis of the WR+O colliding wind binaries. As the results, these X-ray spectra show the phase-locked variations. In this paper, we will report the wind properties of these binaries, and discuss the effect for the circumstellar environment.
Enquiry based module for understanding Lunar Observations
Sule, Aniket
It has been widely reported that students, teachers and general public hold several misconceptions about observational phenomena related to the moon. These include connecting the earth's shadow to the lunar phases, thinking lunar phases will be different at different locations on the earth etc. Typical remedial actions suggest improved explanations in the textbook or improved explanations by the instructor. Here we present a new approach to address these problems. We have developed a stand alone learning unit which encourages students to make their own conclusions from lunar observations. The structure of the unit dispels all these commonly held misconceptions through enquiry based approach. This unit was developed under a new talent nurture programme of Government of India and early trials with some participating teachers demonstrate its tremendous potential.
AGN parameters in the ELAIS field using CIGALE
Suleiman, Nofoz
We present a sample of AGN galaxies in ELAIS N1 field at various redshifts. We combined the new Herschel point source catalogue data with Sloan Digital Sky Survey (SDSS), 2MASS, Spitzer, WISE and other archival photometry data, creating spectral energy distributions (SEDs) that cover the rest-frame wavelength range from far-UV to far-IR (from 0.15 to 160 micrometer). The SEDs were modeled using the CIGALE software, deriving galaxy properties with a high reliability by fitting the attenuated stellar emission and the related dust emission at the same time. We also compared our results to former studies (without the new Hershel photometry and using MAGPHYS), especially focusing on the star formation rate, stellar mass, dust luminosity and dust attenuation. The comparison shows minor differences in the stellar mass, and dust attenuation, but significant differences in dust luminosity. Differences in the star formation rate were also seen at some galaxies.
Astronomy education in Jordan
Suleiman, Nofoz
I present a brief status report for the education of astronomy in Jordan at different stages: primary schools, secondary schools, and universities. I have collected detailed information contacting members of science faculties’ staff at various higher education institutions, also from the official curriculum in the ministry of education, and official websites as well. I will show, that astronomy and space science is well represented among the science subjects for both primary and secondary schools, and an interest is seen on both the side of educators and students. But that interest is missed in higher education for a sundry reason, that there is no astronomy department at all at any Jordanian university. Several attempts from individual and collaborate potentials have been made to develop this field in Jordan but it still needs more practical solutions. Therefore, I recommended to award regional and international grants for number of students annually. These grants will promote them to study the Astronomy in specialized way, and to build up an astronomical society and astronomers who will be capable for competitive research activities in the future.
A large-field IFU with 8192 fibers for FASOT
Sun, Weimin
The Integral Field Unit (IFU) is a very important device for imaging spectroscopy, especially in astronomy. In this paper, we describe the design details of a large-field IFU with 8192 fibers for the Fiber Arrayed Solar Optical Telescope (FASOT). This IFU is made up of two input ports and eight output ports. The two input ports allow to observe two 30.4×30.4 arcsec² fields under orthogonal polarization states. Each input port has 64×64 units, which corresponds to 0.475 arcsec. To fit the requirements of FASOT, the size of fibers is chosen as 35/110/125µm and the NA is 0.12. Fibers with acrylate buffer from YOFC China are qualified to build the IFU. Quartz plates with micropores and quartz V-grooves are made using laser processing technology for assembling the optical fibers. Using low-stress optical fiber assembly technology, the fibers are assembled in two rows in a staggered arrangement. This kind of optical fiber arrangement makes the spectrograph of highest spectral efficiency and makes the fiber have thicker fiber cladding. To reduce the influence of stress from the optical cable on the tracking accuracy of the telescope, the optical cable with 520 core and 0.10kg/m has been designed and a model cable was tested. The transmission efficiency of the modal cable is greater than 85%, and the output focal ratio is slower then F/4.5. In order to validate the feasibility of the technology, a small IFU with 242 fibers was built for a new FASOT prototype. The small IFU proves the feasibility of all technologies for the 8192-fiber IFU.
Two studies using space sports in education and outreach - Sailing on Titan and equestrian sports on Mars
Sundin, Maria
Numerous people are interested in space and many are interested in sports. Combining these subjects can be one way to create curiosity for astronomy and science far beyond the reach of either subject by itself.The idea of space sports most likely originated in science fiction. Since, we have had real examples such as golf on the moon or an astronaut playing baseball in the ISS. Apart from adapting sports from Earth to space, developing new sports could become a reality in the future e.g. in weightlessness. As soon as you leave the Earth, every sport will change. Probably, everyone who is interested in a certain sport will find this intriguing. Discussing why can lead to a deeper understanding of physics and astronomy.Two concept studies within space sports have been done by our team. (1) Sailing on Titan and (2) Equestrian sports on Mars. The studies have been presented as popular science papers, in radio/TV, at sports conferences, during outreach talks, for teachers and in university courses.The purpose of this paper is to present short versions of these two studies, and the experience gained from using them in education and outreach. A second purpose is to create a discussion of further possibilities of using space sports to reach new groups with astronomy and science.For different reasons some people find astronomy far from their liking or feel that it has nothing to do with their lives. Using interdisciplinary aspects such as art, history, myths, navigation, psychology or music as an introduction to astronomy can work quite well as a starting point for more learning or as a key to enthusiasm. Space sports fits well in this context.Due to the interdisciplinary nature of the topic, the project has been done by a team with highly different backgrounds. Included in the team are researchers and professionals in astrophysics, hydrodynamics, marine technology, practical philosophy, space art, equestrian sports and a former world champion in Star boat.
RR Lyrae Stars in the Ultra-Faint Dwarf Galaxies in the Southern Sky
Sung, Eon-Chang
We report the first detection of RR Lyrae variable stars in the Crater II dwarf galaxy, a recently discovered ultra-faint satellite of the Milky Way. Based on B, V time series photometry obtained with the Korea Microlensing Telescope Network (KMTNet) at CTIO, Chile, covering about a 3×3 degree field around Crater II, we have identified ~83 fundamental-mode (ab-type) and ~11 first-overtone (c-type) RR Lyrae stars by adopting template light-curve fitting method. Our preliminary analysis suggests an Oosterhoff-intermediate classification of this galaxy from the mean period of the RRab stars, <pab> ≃0.631 days, and the location of them on the period-amplitude diagram. We also estimated the mean metallicity, ⟨[Fe/H]⟩RRab = −1.65 ± 0.15, reddening, ⟨E(B − V )⟩RRab = 0.05 ± 0.02, and distance of Crater II, (m − M)0 = 20.25 ± 0.10 and d⊙ = 112 ± 5 kpc, from the pulsation properties and the mean apparent magnitude, ⟨VRR⟩ = 20.95±0.01, of the RR Lyrae stars. The stellar population model we have constructed indicates that Crater II is dominated by an old population of ∼10.5 Gyr, but is relatively younger than the oldest globular clusters in the MW in good agreement with its red HB morphology compared to the low metallicity. We will discuss the properties of the RR Lyare stars in other southern ultra-faint dwarf galaxies.</pab>
Faraday rotation signatures of fluctuation dynamos in young galaxies
Sur, Sharanya
Observations of Faraday rotation through high-redshift galaxies has revealed that they host coherent magnetic fields that are of comparable strengths to those observed in nearby galaxies. These fields could be generated by fluctuation dynamos. In this talk, we will report on the resulting rotation measure (RM) and the degree of coherence of such fields obtained from idealized numerical simulations of fluctuation dynamos in forced compressible turbulence up to rms Mach number of 2.4. We show that the rms values of RM at dynamo saturation is of the order of 45 - 55 per cent of the value expected in a model where fields are assumed to be coherent on the forcing scale of turbulence. The dominant contribution to the RM in subsonic and transonic cases comes from the general sea of volume filling fields, rather than from the rarer structures. However, in the supersonic case, strong field regions as well as moderately overdense regions contribute significantly to the RM. Our results are in agreement with the observed RMs in young galaxies.
Fractal basins of convergence of the libration points in the Copenhagen problem with quasi-homogeneous potential
Suraj, M S
The Newton-Raphson basins of convergence, corresponding to the libration points also known as attractors, are unveiled in the Copenhagen problem, where instead of the Newtonian potential and forces the quasi-homogeneous potential created by two primaries are considered. The multivariate version of the Newton-Raphson iterative scheme is used to reveal the attracting domain associated with libration points on the various type of the two-dimensional configuration planes.The correlations between the basins of convergence and the required number of iterations corresponding to it are also presented and discussed in detail. The present numerical analysis reveal that the evolution of the attracting domains in this dynamical system is enormously complicated but worth studying issue.
Spectroscopy of Globular Clusters in the Halo of M81, M82, and NGC3077
Suwannajak, Chutipong
We present integrated spectroscopy of 12 globular clusters located in the halo of the interacting system of M81, M82, and NGC3077. All clusters were observed with the Long-Slit spectrograph on the OSIRIS instrument at the 10.4m Gran Telescopio Canarias (GTC). Ten of these clusters are newly spectroscopically confirmed, with eight clusters located in the halo of M82, making this the first spectroscopic study of a relatively large sample of its globular cluster system. In general, the halo globular clusters in M81, M82, and NGC3077 are similar to the previously known globular clusters in M81, M31, and the Milky Way. With one exception, all globular clusters are metal-poor, with the mean metallicity similar to that of the metal-poor population of globular clusters observed in the inner region of M81. One cluster in M82 is significantly more metal-rich, with metallicity similar to that of the metal-rich population in M81, suggests that this galaxy may have both metal-rich and metal-poor populations of globular clusters. All Clusters in our sample have old ages, with the metal-rich cluster being a few Gyr younger than the other clusters. A kinematic analysis of the clusters shows no evidence of rotation, suggest that they are associated with the halo. The clusters also show no evidence of radial metallicity gradient in the halo of both M81 and M82. These are consistent with the halo populations of globular clusters in M31 and the Milky Way, which suggest that their halo globular cluster systems are similar, both kinematically and chemically.
Four French astronomers president of the IAU (1919-2019)
Suzanne, DÉBARBAT
Four French astronomers have been president of the IAU between 1919 and the present time : Benjamin Baillaud (1848-1934), Ernest Esclangon (1876-1954), André Danjon (1890-1967) and Catherine Cesarsky(born 1943). All of them, remaining to the Académie des sciences, three of them were also director of the Observatoire de Paris and members of the Bureau des longitudes. Catherine Cesarsky, from the Commissariat à l’énergie atomique (CEA), is the first woman to be president of the IAU.
Re-analysis of highest-resolution Solar Maximum Mission X-ray spectra using Bayesian deconvolution
Sylwester, Janusz
Spectra collected in early 1980s by the Bent Crystal Spectrometer (BCS) aboard Solar Maximum Mission still constitute the highest resolution astrophysical database in the X-ray range 1.7 – 3.2 Å. More than 100,000 raw flare spectra are available from NASA archives (ftp://umbra.nascom.nasa.gov/pub/smm/xrp/data/). These spectra were mostly emitted by hot plasmas associated with flares observed in the periods 1980 and 1984-1989. Early analysis of BCS spectra indicated a number of effects previously unseen, like turbulent line broadening and the presence of blue-shifted line components. More recently, substantial progress has been made for both the theory of spectra formation in hot, possibly non-equilibrium flaring plasmas and spectral data reduction and interpretation using new BCS instrument parameters (Rapley, Sylwester and Phillips, 2017, Solar Physics, 292: 50). Using synthetic and observed BCS spectra, we show here how these advances contribute to a better understanding of the physical processes in flare plasmas. In particular, we will illustrate how advanced Bayesian methods can be used to derive physical line profiles and to detect weak line components.
Is a hot plasma component present in the solar corona during periods of the lowest activity?
Sylwester, Barbara
Using spectra collected by the Polish spectrophotometer SphinX, we address the intriguing question of whether a ~10 MK plasma exists in the corona when no active regions ("no-AR") are present on the disk. SphinX observed the integrated soft X-ray radiation ("Sun as a star") throughout most of 2009. This included times of exceptionally low activity when not even small ARs were apparent in X-ray and EUV images and no sunspots in visible light. The SphinX instrument had the highest sensitivity in the spectral range above 1.2 keV of any instrument then in orbit and also good spectral resolution (FWHM = 460 eV). SphinX spectra were recorded over numerous no-AR times lasting up to a few consecutive days. We analysed these spectra on an isothermal and multi-temperature assumption (covering a temperature range 1 MK to 15 MK). For the multi-temperature modelling, we used Bayesian differential emission measure (DEM) deconvolution tested on appropriate sample spectra. We first discuss results of these tests showing the capability of this DEM inversion, and then the DEM inversion as applied to SphinX measurements, in particular no-AR spectra summed over time periods (ensuring that the total number of photon counts in the spectrum above 1.2 keV exceeded ~106). We discuss the derived DEM distributions in terms of the heating mechanisms involved in the Sun's quiet corona.
The New Emerging Flux as a Cause of Quasi-Periodic Pulsations with Large Periods
Szaforz, Zaneta
As quasi-periodic pulsations (QPPs) we define specific, fast and impulsive, changes visible in light curves of some solar flares. Subsequent maxima of QPPs are recorded in fairly regular intervals, while the amplitude of the individual pulses of radiation can change in time. They are usually interpreted as the manifestation of magnetohydrodynamic (MHD) processes in flaring magnetic structures or as the result of repetitive regimes of the magnetic reconnection.Selected flares which reveal QPPs simultaneously in the RHESSI and GOES light curves will be presented. We focused on events with large periods of QPPs - of the order of few minutes. We suggest that QPPs of those flares can be caused by the external modulation of the reconnection process with the new emerging flux.
Laboratory characterization of bent monocrystal wafers for Bragg X-ray spectroscopy
Szaforz, Zaneta
Solar X-ray spectra are a source of information about the composition of solar coronal plasma, plasma temperatures and densities, and also plasma velocities. In order to reveal the X-ray spectra, an X-ray spectrometer must be well-calibrated and use high quality crystals. X-ray spectrometers operate based on the Bragg law, utilizing the specific arrangement of atoms in the crystal lattice.Correct interpretation of the observed spectra requires an understanding of properties of the crystals used. We should have in mind that real crystals properties can vary from their theoretical "perfect" equivalents. That is why precise measurements of the crystal surface and curvature irregulations are necessary.We introduce our laboratory procedures for precise measurements of bent monocrystal wafers lattice shape where Bragg reflection takes place. The described procedure will be used to measure the properties of the crystals that will be used as the dispersive elements in the future solar X-ray spectrometers i.e. SolpeX and ChemiX.
Time-variability and disk geometry in Herbig Ae/Be disks
Szakats, Robert
Herbig Ae/Be stars are young, intermediate mass stars. They exhibit variability at optical and infrared wavelengths, whose physical origin is mainly related to their circumstellar disk. Accretion from the inner disk onto the stellar surface, or temporary increase of the extinction in the line-of-sight caused by passing circumstellar dust clumps are examples for these variability processes. Here we present new results from our coordinated multi-wavelength and multi-epoch observing campaign of nine Herbig Ae stars. The observations covered two weeks with daily cadence, obtaining optical BVRI, near-infrared JHK, and mid-infrared Spitzer photometric monitoring data. We used the data to outline the brightness and color variations during the observing period. One goal of our analysis was to document and understand the response of the inner disk on the changing irradiation by the central star. The intensity and color of the response can be interpreted in terms of the geometry of the inner disk. Another aspect of our study is to reveal the wavelength dependence during UX Orionis-type fading events, which provide direct information on the size of the obscured disk region. Our sample allows us to explore the similarities and differences among the disk structures of Herbig Ae stars, and will help to observationally test the various theoretical models of disk geometry.
Population of AGB stars in the Outer Galaxy
Szczerba, Ryszard
Working on a systematic study of star formation in the Outer Galaxy, we have found that hydrodynamical models of AGB and post-AGB evolution (Steffen, Szczerba, Schoenberner, 1998 A&A, 337, 149) allow for identification of AGB stars of both chemistry on some color-color diagrams. In this respect, K-[24] vs. K-[8] diagram is the best for sources detected in [24] MIPS band (Szczerba et al. 2016, J. Phys.: Conf. Ser. 728, 042004). During my talk I will present details of the selection method, and will discuss properties of AGB stars selected from the “Spitzer Mapping of the Outer Galaxy” survey (SMOG; PI Sean Carey) that covered ~24 deg2 region in the Outer Galaxy: l = (102o, 109 o), b = (-0.2 o, 3.2 o) in the IRAC 3.6–8.0 µm and MIPS 24 µm bands. The analyzed sample contains about 3 millions sources, however, mostly with purely photospheric colors. The selected population of AGB stars from the Outer Galaxy will be compared to the populations of such stars in Magellanic Clouds, as well as to the sample of AGB stars identified toward Galactic bulge.
Statistical analysis of period-eccentricity distribution for large samples of close binaries
Sztakovics, János
Period–eccentricity distribution of eccentric eclipsing binaries (eEB) has major importance in the study of various tidal circularization (and synchronization) processes. Recent space missions as well as ground-based observations provide a large amount of continuous and precise light curves, which enable us to determine several accurate stellar and dynamical parameters for thousands of eEBs. For statistical analysis we developed a fast, automated, although approximating method for determining eccentricity and argument of periastron from the displacement of the secondary minima and the difference of the primary and secondary eclipse durations for large samples of eclipsing lightcurves. We applied this method to nearly 15,000 eEBs in the fields of the primordial and secondary Kepler (and K2), CoRoT space missions, furthermore to OGLE Bulge Survey systems. We present a comprehensive statistical analysis of the period–eccentricity distribution, and we also investigate other orbital as well as stellar parameters of eEBs.
Twinkle little stars: Massive stars are quenched in strong magnetic fields
Tabatabaei, Fatemeh
I present a recent discovery of the role of the magnetic fields and cosmic rays in decelerating the formation of massive stars in the center of NGC1097. Full polarization VLA/radio continuum observations combined with the SMA/CO and the HST/H-alpha and Paschen-alpha data, allowed us to separate the thermal and synchrotron emission, map the ordered & turbulent magnetic field strength, and investigate the energy balance on scales of giant molecular clouds. The strong magnetic field in the central kpc region of NGC1097 is mainly turbulent on observed scales. A comparison of the mass-to-magnetic flux ratio of the molecular clouds shows that most of them are magnetically supported against gravitational collapse needed to form cores of massive stars. Moreover, the star formation efficiency of the clouds drops with the equipartition magnetic field strength. Such an anti-correlation holds with neither the turbulent gas nor the thermal gas pressure. Magnetic fields supporting the molecular clouds prevent collapse of gas to densities needed to form massive stars. Instead, cloud fragmentation will continue to reach the regime for the low density gas to form many low-mass stars.
Compact object mergers driven by gas fallback
Tagawa, Hiromichi
Recently several gravitational wave detections have shown evidence for compact object mergers. However, the astrophysical origin of merging binaries is not well understood. Further, there is a problem that existing astrophysical models for neutron star mergers typically predict a lower merger rate than observed. To solve the problem, we have proposed a new channel for mergers of compact object binaries. We examine the binary evolution following gas expansion due to a weak failed supernova explosion, neutrino mass loss, core disturbance, or envelope instability. In such situations the binary is possibly hardened by ambient gas. We investigate the evolution of the binary system after a shock has propagated by performing N-body/smoothed particle hydrodynamics simulations. We find that significant binary hardening occurs when the gas mass bound to the binary exceeds that of the compact objects. This mechanism represents a new possibility for the pathway to mergers for gravitational wave events.
Chemo-dynamic analysis of the stellar component of Local Group isolated dwarf galaxies
Taibi, Salvatore
The study of dwarf galaxies is of great importance to understand galaxy evolution at the low-mass end. In the Local Group (LG) the great majority of them are found to be satellites of the Milky Way or M31. The closest ones have been studied in great detail, however it is hard to constrain if their present-day observed properties are mainly caused by internal or environmental mechanisms.In order to minimize environmental effects and gain insights into the internal mechanisms that shape the properties of dwarf galaxies, we are studying some of the LG dwarf galaxies that are found in isolation, i.e. located far beyond the virial radius of the Milky Way and M31. Our sample includes two of the three LG isolated early-type, passively evolving dwarf galaxies (Cetus and Tucana), and a similarly luminous gas-rich, transition-type (Aquarius). We note that the isolated early-type galaxies are of particular interest since they break the morphology-density relation found for the LG, where the early-type dwarfs are generally found to be satellites of the main galaxies, while the late-types are all found in isolation.We present here results from a sizable spectroscopic sample of individual red giant branch stars taken with the VLT/FORS2 instrument for each individual galaxy. The spectra have a resolution of R~2600 and cover the region of the near-infrated CaII triplet, from which we obtain line-of-sight velocities and metallicities ([Fe/H]). The wide-area coverage of our data allows us to obtain information on the large-scale dynamical and chemical properties of the considered galaxies, such as the possible presence of rotation, metallicity gradients, and multiple chemo-kinematic components. Results on the Cetus and Tucana early-types place more stringent constraints on the formation mechanisms that led to their present-day morphology, while the study of Aquarius showed an unexpected kinematic correlation between the stellar and the gas component.
YIELDS OF PAIR INSTABILITY SUPERNOVAE AND COMPARISON WITH OBSERVATIONS
Takahashi, Koh
Recent theory predicts that a first star is born with a massive initial mass of > ~100 Msun. Pair instability supernova (PISN) is a common fate for such a massive star. Our final goal is to prove the existence of PISN and thus the high mass nature of the initial mass function in the early universe by conducting abundance profiling, in which properties of a hypothetical first star is constrained by metal-poor star abundances. In order to determine reliable and useful abundances, we investigate the PISN nucleosynthesis taking both rotating and non-rotating progenitors for the first time. We show that the initial and CO core mass ranges for PISNe depend on the envelope structures: non-magnetic rotating models developing inflated envelopes have a lower-shifted CO mass range of ~ 70–125 Msun, while non-rotating and magnetic rotating models with deflated envelopes have a range of ~ 80–135 Msun. However, we find no significant difference in explosive yields from rotating and non-rotating progenitors, except for large nitrogen production in non- magnetic rotating models. Furthermore, we conduct the first systematic comparison between theoretical yields and a large sample of metal-poor star abundances. We find the predicted low [Na/Mg] ~ -1.5 and high [Ca/Mg] ~ 0.5–1.3 abundance ratios are the most important to discriminate PISN signatures from normal metal-poor star abundances, and confirm that no currently observed metal-poor star matches with the PISN abundance.
Three-dimensional simulations of accretion onto a star from a magnetized accretion disk: Fast funnel-wall accretion
Takasao, Shinsuke
We show the results of global three-dimensional magnetohydrodynamics simulations of an accretion disk with a rotating, weakly magnetized central star. The disk is threaded by a weak large-scale poloidal magnetic field. The central star has no strong stellar magnetosphere initially and is only weakly magnetized. We investigate the structure of the accretion flows from a turbulent accretion disk onto the star. Our simulations reveal that fast accretion onto the star at high latitudes is established even without a stellar magnetosphere. We find that the failed disk wind becomes the fast, high-latitude accretion as a result of angular momentum exchange mediated by magnetic fields. The rapid angular momentum exchange occurs well above the disk, where the Lorentz force that decelerates the rotational motion of gas can be comparable to the centrifugal force. Unlike the classical magnetospheric accretion model, fast accretion streams are not guided by magnetic fields of the stellar magnetosphere. Nevertheless, the accretion velocity reaches the free-fall velocity at the stellar surface owing to the efficient angular momentum loss at a distant place from the star. Our model can be applied to Herbig Ae/Be stars whose magnetic fields are generally not strong enough to form magnetospheres, and also provides a possible explanation why Herbig Ae/Be stars show indications of fast accretion. A magnetically-driven jet does not blow from the disk in our weak field model. The differential rotation cannot generate sufficiently strong magnetic fields for the jet acceleration, because the Parker instability, which only occurs in 3D, interrupts the field amplification.
Cloud density for Equilibrium Cloud Condensation Model of Jupiter's atmosphere
Takeuchi, Satoru
Equilibrium Cloud Condensation Model (ECCM) is a popular and simple one-dimensional model for studies of vertical structures of Jovian atmospheres (Weidenschilling and Lewis, 1973). The model predicts vertical distributions of temperature, pressure, mixing ratios of some condensable vapors, and ones of cloud densities after condensations at each altitude. Wong et al.(2014), however, pointed out that the cloud densities predicted by the ECCM exceed vapor's densities before condensations and that the ECCM violates consavation law of mass. In this study, we attempt to introduce more relevant formula of cloud density for the ECCM to keep mass conservation.We think that there are some confused uses between total column values above an altitude and volume values on same altitude in discussion of cloud density of Weidenschilling and Lewis (1973). So, to avoid this confusion, we will construct new formula of cloud density without use of any column values.As a first step, a term of cloud density is added in equation of hydrostatic equilibrium. This term corresponds to pressure decrese by condensation, which is equal to difference between over-saturated partial pressure of an apor before condensation and saturated pressure of same vapor deteremined by temperature at an altitude. Thus, cloud density can be estimated from this connection. The new formula can estimated cloud densities, which don't exceed vapor densities before condensation, and can save conservation law of mass.
Near-IR imaging polarimetry of the RCW 106 cloud complex
Tamaoki, Shohei
We have carried out near-IR imaging polarimetry toward RCW 106 with the JHKs-simultaneous imaging polarimeter SIRPOL mounted on the IRSF 1.4m telescope at SAAO, in March and May, 2017 and January, 2018. We have observed 29 fields and covered mostly the southern part of the giant molecular cloud complex associated with the HII region RCW 106, which is located at a distance of 3.5 kpc and is elongated approximately in the north-south direction with a size of ~70x15 pc. Our preliminary analysis indicates that the magnetic field seems to globally run along the complex elongation, unlike many other elongated clouds that are often reported to have their global elongations perpendicular to the magnetic fields. The RCW 106 complex consists of many small filaments or clumps. Some of such filaments seem to parallel to the magnetic fields, but some others perpendicular. Around the central part of the HII region RCW 106, the magnetic field appears to be influenced by the expansion of this HII region.Here, we present our preliminary results by comparing with the archival molecular line and far- to mid-IR data.
Age-Depth Relation between the Galactic Supernovae and Antarctic Ice Core Records
Tanabe, Kenji
Nitrate ion (NO3-) concentrations(spikes) in the Antarctic ice core produced by cosmic gamma ray are possible records of galactic supernovae remnants (1). However, such spikes were occasionally contaminated with large-scale volcano explosions. Fortunately, during 11th century , because of no big volcano explosion, three set of conspicuous spikes are seen in the Antarctic Ice core extracted in 2001 from Japanese Antarctic station named Dome Fuji(3810meter height).First two spikes successfully coincide with SN1006 ,SN1054(Crab nebula)(2) .On the contrary the third double-peaked spike does not coincide with any SN but probably the very bright outbursts of the symbiotic binary R Aquarii(3) .This was recorded in Korean historical guest star official documentation in the year of 1073 and 1074 AD(4).Making use of these 11th century historical records(year) and the depth(meter) data of the nitrate ion spikes in the ice core, we can obtain an Age(year)-Depth(meter) relation. A tentative formula is as follows:y(year)=2003(67) - 19.6(1.3)x(meter)Applying this formula to the other conspicuous nitrate ion spikes, we can estimate the year of SNRs .References:Rood,R.T. et al 1979 Nature 282,701Motizuki,Y. et al 2009,eprint arXv0902.3446Tanabe K., Motizuki, Y., 2012, Memorie della Societa astronomia ItalianaVol.83 N.2,840Yang,H.-J.et al. 2005 A&A 435,207
Dark Memories of the Past: Discovery of Ultra-Diffuse Objects around NGC 1068
Tanaka, Ichi
NGC 1068 is one of the most famous Type-2 Seyfert galaxies. Due to its close vicinity to us, the galaxy has played an important role for a unified model of AGNs. We have searched for a sign of the past dynamical disturbance event on the galaxy using deep and wide optical imaging data by the Subaru Telescope. The data taken by Hyper Suprime-Cam as well as the archived data by Suprime-Cam reveal several interesting faint outer structures of the galaxy, most of which were never reported before. We discover three large (re=3~5.5kpc), extremely diffuse objects (UDOs) within 45kpc from the center of NGC 1068. We suggest that two of these UDOs are actually a part of a large loop-like structure surrounding NGC 1068. Such an extremely faint loop or stream is the direct evidence for a past minor merger event. The other UDO has a distorted morphology, suggesting that it is under the influence of strong tidal interaction. Furthermore, we have identified two smaller and very diffuse (µ0,r >25 mag arcsec-2) dwarf candidates within ~140 kpc from NGC 1068. We speculate that these ultra-diffuse dwarfs could be the Tidal Dwarf Galaxies related to the mass assembly of NGC 1068 long time ago. We also detect an asymmetric outer one-arm structure emanated from the western edge of the outermost disk of NGC1068 together with a ripple-like structure at the opposite side. These structures are also expected to arise in a late phase (up to several billion years ago) of a minor merger, according to numerical simulations. We discuss about the possible link between our discovery and the current AGN activity.
Spatially-resolved Measurement of Hydrogen Volume Density in the Central Molecular Zone of the Milky Way
Tanaka, Kunihiko
Star formation in the Galactic central molecular zone (CMZ) exhibits several characteristics that are rare elsewhere in the Galaxy: formation of young massive clusters, mini-starburst in the Sgr B2 complex, and low star formation efficiency in the vast majority of the GMCs. We present the result of spatially resolved measurement of hydrogen volume density in the CMZ, which is one of the most important parameters in the dynamical processes of the GMCs. We have measured the three-dimensional (position-position-velocity) distributions of volume density, gas column density, kinetic temperature, and fractional abundances of eight molecules (HCN, HCO+, CS, H2CO, SiO, N2H+, HC3N, HNC), through excitation study using various published survey data and the HCN 4-3 data newly obtained with the ASTE 10-m telescope. The hierarchical parameter inference technique is used to suppress artificial correlations among the parameters due to the deficiency in simple one-zone LVG analysis. The main results are summarized as follows: (1) the typical volume density and temperature are measured to be 104.1 cm-3 and 101.8 K, respectively, for the gas visible in high-density tracer lines; meanwhile, low-J CO lines are likely to originate from gas with lower density and temperature, whose mass is comparable to that of the high-density gas. (2) CMZ clouds are generally affected by shockwaves, as indicated by the spatial correlation between the temperature variation and that in the abundances of shock-tracer molecules. (3) the parameters that distinguish the clouds with signatures of SF (water masers and HII regions) from quiescent clouds are found to be the virial parameter and volume density, through linear discriminant analysis. These results are consistent with the picture that the CMZ clouds generally have high density typical of SF clouds in the Galactic disk, but their star formation is suppressed by high internal pressure support provided by interaction with shocks.
An analysis of M31 and its satellites' populations through RR Lyrae.
Tanakul, Nahathai
RR Lyrae variable stars are powerful tools to study their host stellar populations. Information such as distance, metallicity, reddening, and age can be obtained from their pulsation properties. Dwarf spheroidal (dSph) galaxies are the most common type galaxies in the Local Group. They are found around massive hosts such as the Milky Way (MW) and M31 and are suggested to be the present-day counterparts to systems from which spheroids and stellar halos of larger galaxies were assembled. By comparing RR Lyraes in these dSphs and their host galaxies, we might understand more about the formation of these galaxies. In this study, we aim to: 1) Investigate the Oosterhoff type of RR Lyrae stars in M31 and its satellites including eight dSphs and compare them with the MW to better understand the formation of these galaxies. 2) Investigate the early formation history of these galaxies through knowledge of their RR Lyrae stars. In order to achieve these goals, we have analyzed 6 fields in M31 using archival imaging from the Hubble Space Telescope. Published data for M31, M33, and several M31 dSphs are also included. The results are then compared with those in the MW to better constrain the early history of the Local Group and the galaxies therein.
Simulations of low-velocity collisions among agglomerated asteroids
Tancredi, Gonzalo
We present numerical simulations on the study of propagation of impact-induced seismic waves into the interior of an agglomerated asteroid and low-velocity collision of two agglomerates.The numerical simulations are done with a parallel multithreading algorithms for self-gravity computation implemented in the package ESyS-Particle. ESyS-Particle applies the Discrete Element Method to simulate an ensemble of interacting particles under several contact and body forces. It was conceived to improve the computational efficiency of simulations involving large number of particles. Taking into account the different time scales of the process involved in the problem (gravitation interaction and contact among particles), a parallel mesh-based algorithm that speed up the self-gravity calculation is proposed, and it is integrated with the contact force calculation. We call this new package: ESyS-Gravity. One set of numerical experiments consist on a spherical asteroid, maintained by selfgravity which is impacted on the surface by a small projectile. The propagation of impact induced seismic waves into the interior is studied as well the ejection of low-velocity particles from the entire surface. In another ser of experiments we consider two agglomerates colliding at low-velocity (hundreds m/s). The ejection of particles and the deformation of the interiors are analyzed.The asteroids are modeled as agglomerates of individual spherical particles as well as agglomerates of irregular boulders formed by spherical particles. These results are relevant to understand the outcomes of impacts in rubble/gravel pile asteroids, as well as the formation of families.
On the asymmetric features in circumstellar disks
Tang, Ya-Wen
Current detection of exoplanets is mostly obtained at optical and near IR wavelengths toward disks where dense gas has been dissipated. In order to look for planets at earlier evolutionary stage, indirect evidences are invoked, such as rings of dust free region within dense disks, or spiral patterns. With the starting of ALMA early science observations, these indirect evidences at the millimeter (mm) and sub-mmm wavelengths have been detected in several disks. In this poster, we report high angular resolution (0.1") observations with ALMA of the 1.3 mm continuum and 12CO J=2-1 emission from the inner 100 AU of the disk surrounding the Herbig Ae star AB Aurigae. The continuum emission shows three distinct feature: a compact (~ 2 au) dust disk around the star, the asymmetric dust ring at 120 AU, and previously undetected extended emission about 30 AU around the star along the rotation axis of the system. The CO emission is dominated by two prominent spiral-like arms. After correction for the large scale flux resolved out by these observations, these arms appear to be about twice brighter than their surrounding medium. Their kinematics is consistent with Keplerian rotation at an inclination of 30 degree. The apparent two arm spiral pattern is best explained by tidal disturbances created by an unseen companion located at 60--80 au, with dust confined in the pressure bumps created outside this companion orbit. However, the residual continuum emission, coinciding with the peak CO brightness and a large pitch angle of the spiral at this location, suggests another hidden object here, which would help to explain the overall emptiness of the cavity. Alternative mechanisms to excite the spirals are discussed. The origin of the large pitch angle detected here remains puzzling.
New relativistic precession model of the earth for a long time interval
Tang, Kai
Tang et al. (2015) provided a numerical solution of the Earth’s precession in the relativistic framework for a long time span. Now we use a new hybrid integrator to calculate the motion of the solar system in the BCRS and the Earth's rotation in the GCRS. All the main relativistic effects are included following Klioner et al. (2010), especially we considered several relativistic reference systems with corresponding time scales, scaled constants and parameters. We improve this work to give new parameters to represent the precession. The results are still consistent with other long-term precession theories. The relativistic influences are obtained and analyzed here.
Evidence for the internal dissipation origin in the high-energy prompt emission of the Fermi-LAT GRB
Tang, Qingwen
The origin of the prompt high-energy >100 MeV emission of gamma-ray Bursts (GRBs), detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, for which both an external shock origin and internal dissipation origin have been suggested, is still under debate. In the internal dissipation scenario, the high-energy emission is expected to exhibit significant temporal variability, tracking the keV/MeV fast variable behavior. Here, we report a detailed analysis of the Fermi data of GRB 170214A, which is sufficiently bright in the high energies to enable a quantitative analysis of the correlation between high-energy emission and keV/MeV emission with high statistics. Our result shows a clear temporal correlation between high-energy and keV/MeV emission in the whole prompt emission phase as well as in two decomposed short time intervals. Such a correlation behavior is also found in some other bright LAT GRBs, e.g., GRB 080916C, 090902B and 090926A. For these GRBs as well as GRB 090510, we also find the rapid temporal variability in the high-energy emission. We thus conclude that the prompt high-energy emission in these bright LAT GRBs should be due to an internal origin.
An Unexpected Dip in the Solar Gamma-Ray Spectrum
Tang, Qingwen
The solar disk is a bright source of multi-GeV gamma rays, due to the interactions of hadronic cosmic rays with the solar atmosphere. However, the underlying mechanism is not understood, except that its e_x005Fciency must be greatly enhanced by magnetic elds that redirect some cosmic rays from ingoing to outgoing before they interact. To elucidate the nature of this emission, we perform a new analysis of solar atmospheric gamma rays with 9 years of Fermi-LAT data. We detect signi cant gamma-ray emission from the solar disk from 1 GeV up to ~200 GeV. The overall gamma-ray spectrum is much harder than the cosmic-ray spectrum. We nd a clear anticorrelation between the solar cycle phase and the gamma-ray flux between 1-10 GeV. These observations now span nearly the full 11-year solar cycle. Surprisingly, we observe a dip around 30{50 GeV in an otherwise power-law spectrum. This was not predicted and is not understood. The bright ux above 100 GeV, especially during the upcoming solar minimum, poses exciting opportunities for HAWC, LHAASO, and IceCube.
Discovery of GeV gamma-ray emission from the LMC B0443-6657 with the Fermi Large Area Telescope
Tang, Qingwen
I would like to report the discovery of gamma-ray detection from the LMC B0443-6657 using the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. LMC B0443-6657 is a flat spectrum radio source and possible to associate with a supernova remnant in the Large Magellanic Cloud (LMC N4). Employing the 8 years of the LAT observations between 0.2-100~GeV, our result reveals a significant excess (>9.4 sigma) above the background, which is based on either the 4-years LAT catalog (Acero et al. 2015 ApJS) or the best source model of 73.3 months data (Ackermann et al. 2016 A&A). The hadronic model predicts a low X-ray or TeV flux while the leptonic predicts an observable flux in these two energy bands. The follow-up observations of the LMC B0443-6657 in X-ray or TeV band would help constrain the contribution from the CR electrons and protons.
Spectral evolution and super Eddington accretion of the new Black hole candidate MAXI J1535-571 during its 2017 outburst
Tao, Lian
The black hole candidate MAXI J1535-571 is a recently discovered X-ray transient. We report on the observations with Insight-HXMT and other X-ray telescopes during the outburst. We present the state transition from the hard state to the soft state overall observation duration. When the source is not in the hard state, detailed spectral analyses using a multi-temperature disk model reveal that the disk luminosity is flatter than the inner disk temperature to the fourth power, and the disk temperature profile varies as the disk radius raised to the power of -0.5, consistent with the behavior of a slim disk, implying that the disk structure has been modified due to the high luminosity of ~1039 erg s-1.
Protoplanetary disc vortices strengthened by gas thermodynamics
Tarczay-Nehéz, Dóra
Large-scale horseshoe-like brightness asymmetries in transitional protoplanetary discs are thoughtto be caused by anticyclonic vortices. These vortices can play a key role in planet formation asmm-sized dust the building blocks of planets can be accumulated inside them. Anticyclonicvortices form by Rossby wave instability, which can be excited at gap edges of giant planets or atsharp viscosity transitions of accretionally inactive region edges. It is known that vortices proneto stretching and later dissolving due to disc self-gravity for canonical disc masses by assuminglocally isothermal gas. To improve the hydrodynamic model of protoplanetary discs, we includethe disc thermodynamics too. In my talk, I present our results on the evolution of the vorticesformed at the outer edge of an accretionally inactive region (dead zone) assuming politropic equa-tion of state for the gas and self-gravitating disc. We found that disc thermodynamics results inlonger lifetime and stronger vortices mitigating the vortex weakening effect of disc self-gravity.Our results suggest that the hypothetical vortex-aided planet formation scenario is favored indiscs where thermodynamics are important.
Extragalactic Cepheid Database
Tarczay-Nehéz, Dóra
Since the early 20th century it has been known that d Cephei type stars serve as standard candles to measure distance of the hosting cluster or galaxy with the period-luminosity relation. So with this relation extragalactic distances can be determined. For being such a good indicator, we need tocalibrate the period-luminosity relation accurately. Beyond our galaxy almost 100 galaxies are known to host more than 10000 Cepheid variables, but the type of some of them is uncertain. There is not a comprehensive, up to date list or database on these variables at the moment.In our work we construct a database from the known extragalactic Cepheids gathering their positions and physical properties – periods, photometric magnitudes, light curve and radial velocity data – to make data analysis more easy.
Optical observations of quasars for the link between ICRF and the future Gaia CRF
Taris, François
As in the radio domain, it can be reasonably postulated that quasar optical flux variations can alert us to potential changes in the source structure. These changes could have important implications for the position of the targets photocenters (together with the evolution in time of these centers) and in parallel have consequences for the link of the reference systems.In the case of some targets that are well observed by the TAROT telescopes, the Allan time variance shows that the largest averaging period of the magnitudes is in the range 20d-70d. The observation period by Gaia, for a single target, largely exceeds these values which might be a problem when the magnitude variations exhibit flicker or random walk noises.The Allan time variance could also help to quantify the optical stability of a target and, then, could help to ?nd new suitable targets for the link between the reference frames.Preliminary computations show that if the coordinates of the targets studied in this work were affected by a white phase noise with a formal uncertainty of about 1 mas (due to astrophysical processes that are put in evidence by the magnitude variations of the sources), it would affect the precision of the link at the level of 50 µas.In order to obtain long and well sampled time series, that could also be of interest to bring constraints to astrophysical models of AGN, the SYRTE department of the Paris Observatory has the project to build a 1m robotic telescope to monitor the magnitude variation of AGN. The results of the seeing campaign and the first images, obtained in remote mode with a 50cm test telescope, will be presented.
The role of asymptotic giant branch stars in the chemical evolution of the Galaxy
Tautvaisiene, Grazina
Asymptotic branch stars play an important role in enriching galaxies by s-process elements. Recent studies showed that their role in producing s-process elements in the Galactic disk was underestimated and should be reconsidered. Based on high-resolution spectra obtained with the ESO VLT UVES and 2.2 m MPG/ESO FEROS spectrographs, we have determined abundances of neutron-capture elements in a sample of more than 300 stars located in the field and open clusters towards the Galactic centre and investigated an elemental enrichment pattern according to their age and galactocentric distance.
Carbon and oxygen abundances in dwarf stars of the Solar neighbourhood
Tautvaisiene, Grazina
Stars and planets form from the same material, thus some of their properties are expected to be inter-connected. In order to characterize exoplanets, we need to investigate the planet-hosting stars. Occurrence of different types of planets and their orbital parameters may depend on chemical abundances of their hosting stars. The study of carbon and oxygen in stars is crucial because these elements are quite abundant and play an important role in stellar interiors by generating energy in thermonuclear reactions. Abundances of C and O may influence water availability on exoplanets. The C/O ratio also controls an amount of carbides and silicates that can be formed. We are performing a uniform study of C/O ratios in a large sample of stars located towards the northern ecliptic pole which will be targeted by the TESS and JWST space missions. The first results for a sample of 140 stars analysed will be presented.
A Newly Discovered Reservoir of Dwarf Galaxies in the Centaurus A Group
Taylor, Matthew
Recent years have seen an acceleration in the discovery rate of dwarf galaxies in the Local Universe. The subsequent unveiling of coherent satellite phase-space structures like groups and planes has led to a renaissance in the study of low-surface brightness dwarf galaxies, including their utility in near-field cosmological studies. In an effort to push this field further, optical u’g’r’i’z’ imaging of 22 deg^2 centered on the nearby giant elliptical galaxy NGC5128, as part of the “Survey of Centaurus A’s Baryonic Structures” (SCABS) campaign, has been searched for new dwarf galaxies in the Centaurus A group. We will present first results of the stellar mass and stellar population properties for several dozens of promising new candidates, including several dwarf pairs appearing within a few pc in projection that may indicate physical associations. These new dwarf galaxies extend the size-luminosity relation toward fainter total luminosities and smaller sizes for known dwarf galaxies outside the Local Group, and are broadly consistent with the properties of nearby dwarf spheroidal galaxies. Altogether, these new results show NGC5128 to be the host of a large reservoir of low-mass dwarf galaxies that is at least as rich as that of the Local Group and is ripe for detailed follow-up observations.
Main pileup in exoplanet period distribution is double-peaked, being separated by a gap, for planets of metal-rich sunlike single stars
Taylor, Stuart F.
We present major new features in the log period distribution of the counts of a primary population of planets, those 40% of planets hosted by stars that are metal-rich and sunlike in surface gravity: The main pileup of these planets’ distribution in log period that broadly peaks at several hundred day periods is composed of not one but two peaks, with a prominent gap separating these two peaks. This double-peaked shape is unexpected, and is not present in the periods of planets of the main other populations of stellar hosts: Stars with low surface gravity, and metal-poor sunlike stars. The gap is at least partially absent for periods of planets of sunlike stars with stellar companions. These readily verifiable features appear important to the how distribution of eccentricities by period shows a correlation with metallicity at shorter periods that goes away in the gap region where the metal-poor population peaks. This correlation appears to more weakly come back in the period range of the longer period peak. We discuss how other parameters vary in the short period peak, gap, and long period peak regions.
Constraining Metal Mixing and Feedback Using Spatially Resolved Metal Production Histories in M31
Telford, Grace
A comprehensive theory describing how the energetic feedback and metal production due to star formation affect the evolution of entire galaxies remains an elusive goal. A promising way forward is to connect spatially and temporally resolved star formation histories (SFHs) to the evolution of global ISM properties within galaxies. The SFH is tightly coupled to the history of metal production within a galaxy via ejective feedback from both young and evolved stellar populations. Therefore, given knowledge of the spatially resolved metal production history and the present-day distribution of metals in a galaxy disk, metals can be leveraged as tracer particles to constrain the necessary feedback due to star formation over the galaxy’s history. M31 is a unique case in which the necessary data to make such measurements are available. The ancient SFHs within ~kpc sized regions have been derived in M31 from color-magnitude diagrams of resolved stars from the Panchromatic Hubble Andromeda Treasury survey (Williams et al. 2017). We use these CMD-based SFHs to calculate spatially resolved histories of metal production in M31. We model when and where Type II SNe, Type Ia SNe, and AGB stars inject O, C, N, and Fe into the ISM. We calculate the total metal mass formed up to the present as a function of radius, predicting the spatial distribution of metals if metals remain in the location where they formed. But if metals are transported within the disk (via turbulent mixing) and/or ejected into the gaseous halo and possibly re-accreted (via SN feedback, galactic fountain), then the distribution of metals will change. We compare our predicted radial metal gradient for the case of no metal transport to the metal gradient inferred from observations of the stars, gas, and dust in M31. This assessment of global metal mixing in a galaxy disk provides a unique test of the required feedback in a disk galaxy with sustained, low-level star formation over several Gyr timescales.
Physical and chemical properties of narrow-line regions in z~3 radio galaxies through multi-line analysis
Terao, Koki
Physical and chemical properties of the interstellar medium (ISM) in galaxies and their redshift evolution are important to understand the formation and evolution of galaxies. The ISM properties of massive galaxies at z > 2 are particularly interesting, because the evolution of massive galaxies had been already completed at such high redshift. However, normal massive-galaxies at z > 2 are too faint to be examined in detail. On the other hand, emission-line spectra of narrow-line regions (NLRs) in active galactic nuclei (AGNs) offer an alternative approach to investigate the ISM properties of high-z massive galaxies. _x005F In this work, we use the rest-UV spectra of three radio galaxies at z ~ 3 observed with VLT/FORS2 for trying to measure the flux of several emission lines including relatively faint ones. As a result, we detect some faint emission lines such as the NIV]λ1486, OIII]λ1665, and [NeIV]λ2424. In addition, we collect the UV-emission line fluxes of seven z ~ 3 radio galaxies from the literature. We diagnose the physical and chemical properties of the ISM for each object through the comparison between the measured emission-line fluxes and detailed photoionization models with Cloudy. We confirm that the metallicity of NLRs in AGNs at z ~ 3 is higher than the solar metallicity, without assuming the gas density and ionization parameter thanks to the newly detected faint emission lines. This result suggests that high-redshift radio galaxies have matured chemically at z ~ 3. More interestingly, the inferred gas density and ionization parameter are systematically higher than those seen in NLRs of low-z SDSS AGNs. This result implies that ISM properties of AGN host galaxies show redshift evolutions.
BCGs radio analysis from a EGMRT and CLASH sample of galaxy clusters
Terni de' Gregory, Beatrice
Among the radio galaxy hosts, the Brightest Cluster Galaxies (BCGs) witness special conditions, being large objects at the center of a deep potential well.To properly evaluate the contributions of Star Formation (see Fogarty K. 2015 and Donahue M. 2015) and of their active nucleus to the radio emission, we are studying a sample of eleven BCGs selected mainly from the radio EGMRT (Kale R. 2015) and the optical CLASH (Postman M. 2012) surveys.In this talk I will present important results from this study pointing out the radio properties of these galaxies in relation with the dynamical status of their environment. Both Star Formation and AGN activities are important components of feedback mechanisms proposed to reconcile the discrepancy between the predicted and the observed cooling rate in cool core clusters.
The role of magnetic field in star formation
Tessema, Solomon Belay
In this paper we present the role of magnetic field in star formation. Star formation in magnetized molecular cloud (MC) needs clear understanding of how the magnetic pressure counteracts gravity and prevent gravitational collapse. In other hand, magnetic field transports excess angular momentum from the central core. Thus the outflow of angular momentum causes the mass to fall onto the central core. Therefore, magnetic fields are important at every scale in the star formation process. We focus on questions regarding the role of magnetic fields in star formation such as: What is the effect of magnetic fields on MC core collapse? Do magnetic fields tend to suppress collapse or enhance the core collapse? In case of the weak field the cloud core collapses in a freefall time. But if the field is strong the cloud may not collapse unless external pressure dominates this field. Therefore, in this work we need to show theoretically how the strong magnetic field is dragged inward by the external pressure during the core collapse and formulate the critical mass of the core in the presence of magnetic pressure and external pressure as well as show the interplay among gravity, magnetic pressure and external pressure.
A Transit Timing Variation Analysis of Extra-solar Planetary System Qatar-1
Thakur, Dr. Parijat
We present three new transits of the extra-solar planetary system Qatar-1 observed with the 2-m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle, India between June 2016 and September 2016. In order to examine transit timing variation (TTV), our three transits data are combined with thirty five previously available transit light curves. These thirty eight transit light curves allow us to estimate the physical and orbital parameters, as well as to refine the ephemeris for the orbital period and mid-transit time to investigate the possible transit timing variation (TTV) in this extra-solar planetary system. It is found that there is no evidence of transit timing variation (TTV) to confirm the presence of additional planet in the extra-solar planetary system Qatar-1.
Dwarf galaxies as hosts of massive explosions - a view in 3D
Thöne, Christina
Massive stars are connected to highly star-forming environments and galaxies, and hence are their explosive deaths. Gamma-ray bursts (GRBs) and superluminous supernovae (SLSNe) are the most luminous of those stellar explosions. Both classes of objects are hosted in starburst galaxies with low metallicities and young stellar populations, which, at redshifts below 1-2 are mostly dwarf galaxies. Integral field data now allow us to study the most nearby and brightest of them with resolved spectroscopy. Here, we present a sample of z<0.5 GRB hosts observed with FLAMES and MUSE to study their spatially resolved abundances, star-formation (SF) and kinematics. GRBs are usually found in regions with low metallicity and high star-formation rate, but not at the site with the most extreme properties. In fact, most are located at the edge of the most extreme region in their host. The kinematics of these galaxies mostly do not show evidence for SF triggers due to major interactions or merger. However, we do find evidences for outflows from these galaxies, underlining the extreme SF activity. Last, we also present the curious case of a seemingly solar metallicity SLSN host and SLSN environment, where star-formation history modeling reveals the contribution of a young low-metallicity population, the likely origin of the SLSN progenitor. This shows that detailed 3D studies are crucial, not only for the hosts of massive stellar explosions but for understanding the star-formation history and triggers of dwarf galaxies in general.
New limit on delta alpha/alpha from an analysis QSO spectra
Thong, Le
A new stringent limit relating to the variation of the fine-structure constant (alpha) has been extracted from Ritz wavelengths of 27 quasi stellar object (QSO) absorption spectra lines of Fe II. The calculation was combined with laboratory wavelengths and QSO spectra to obtain the result delta alpha/alpha = (0.027+-0.832)x 10 -6 . This result proposes how dedicated astrophysical estimations can improve these limitations in the future and can also constrain space-time variations.
Searching for delta alpha/alpha from analysis QSO spectra
Thong, Le
We report new stringent limit relating to the space-time variation in the fine-structure constant from an analysis of quasar J110325-264515 towards zabs = 1.8389 . We find delta alpha/alpha = (1.56+-1.78)X10-6 from a comparison of laboratory wavelengths of Fe II with those found in quasar spectra. The obtained result proposes how inferred measurements of cosmic can improve these limitations in the future and can also constrain space-time variations.
Strong limit on delta alpha/alpha from analysis QSO spectra
Thong, Le
We use the observed spectra from the white dwarf star G191-B2B to constrain the space-time variation of the fine-structure constant. The analysis was combined with laboratory and astronomical lines in [Ni V] to find delta alpha/alpha = (-0.003+- 0.072) x 10-6 . This result represents the most stringent limit on delta alpha/ alpha compared with the results using the same data published in the literature.
Solar disk radius determined from Sun occultation by the Moon using bolometric and photometric instruments onboard the PICARD satellite
Thuillier, Gerard
Despite the importance of having an accurate measurement of the solar disk radius, there are large uncertainties of its value due to the use of different measurement techniques and instrument calibration. Measurements of the solar disk radius is a basic metrological quantity of the solar system. Furthermore, is the solar radius constant or changing with time in particular with solar activity. The solar radius value depends on the solar atmosphere opacity, which allows solar model validation by comparing model predictions with the observations.Three instruments onboard the PICARD spacecraft, the Bolometric Oscillations Sensor (BOS), the PREcision MOnitoring Sensor (PREMOS), and a solar sensor (SES), are used to derive the solar disk radius using the light curves produced when the Sun is occulted by the Moon. Nine eclipses from 2010 to 2013, resulted in 17 occultations. The calculation of the solar disk radius uses a simulation of the light curve taking into account the center to limb variation provided by the Non local thermodynamic Equilibrium Spectral SYnthesis (NESSY) code and the relative positions of Sun, Moon and spacecraft. The solar disk radius for each occultation was obtained for 4 spectral domains in the visible and IR solar continuum and two in UV. No relation with solar activity being found, we derived a more precise radius value by averaging these values. At one astronomical unit, we obtain 959.79” from the bolometric experiment; from PREMOS measurements, we obtain 959.78” at 782nm; 959.76” at 535nm. We found 960.07” at 210nm, which is a larger value than the others given the photons at this wavelength originate from the upper photosphere and lower chromosphere. The minimum solar disk radius is found around 600nm.We point out that the Moon provides a stable reference for instruments in space allowing long term studies by using simple photometers, which are robust instruments able to survive without significant aging in the harsh orbital environment.
Mass Discrepancy-Acceleration Relation from Giant Elliptical Galaxies to Dwarf Galaxies
Tian, Yong
The discrepancy between the dynamical mass and the baryonic mass is strongly related to the gravitational acceleration of 153 spiral galaxies from SPARC database. This is called the mass discrepancy-acceleration relation (MDAR). We studied an extensive elliptical galaxies catalog of giant elliptical galaxies and dwarf galaxies (Dabringhausen & Fellhauer 2016). We found that the MDAR of 500 elliptical galaxies agreed well with the result in spiral galaxies (McGaugh et al. 2016).
Evolution of the Stellar Haloes
Tissera, Patricia
The stellar haloes are ubiquitous components of galaxies which have been identified surrounding galaxies of different morphologies. Observations and numerical simulations agree that most of their stellar populations were contributed by accreted dwarf galaxies. Several questions remain to be answered:When this accretion occurred and when the stars in the stellar haloes at z=0 where formed and accreted? What do cosmological models predict about the formation and evolution of the properties of the stellar haloes?In this poster, we present first results on the analysis of the evolution of the metallicity and density profiles of the stellar haloes in numerical simulations.
Dual AGN in cosmological simulations
Tissera, Patricia
We present a study of Dual AGN in the largest cosmological simulation of the EAGLE project. We define a Dual AGN as two active black holes (BHs) with a separation of 30 kpcs or lower. We find that Dual AGN are rare events in the simulation. Rapid variability in hard X-ray luminosity at scales of megayears is present during the evolution of Dual AGN. This AGN variability could affect the detection of the Dual systems. We also find an increasing trend of Dual AGN distribution as a function of decreasing separation at z=0.8-1. A large peak is prominent in the Dual AGN distribution at 20 kpc that corresponds to the last passage of the host galaxies after they merged. We also find that 75 percent of the host galaxies underwent or are undergoing a recent merger with stellar mass fraction larger than 0.1.
Unveiling the impact of the environment on the properties of galaxies
Tissera, Patricia
Patricia B. Tissera, Yetli Rosas-Guevara, Enrique Paillas, Nelson Padilla, Claudia LagosWe study the role of the environment at large scale on the main properties of galaxies such as sSFR, metallicity, colours, ages and so on. For that, we use the EAGLE simulations that are designed to produce a virtual Universe that closely matches the observed properties of galaxies at low redshift. We use the void catalogue of Paillas et al 2017, where voids are identified as spherical underdense regions. We split our sample of galaxies into three different groups depending on the distance at the centre of the voids and also they match the same stellar mass function. In this poster, we present the first results when we compare the properties of the galaxies as a function of the distance of the voids.
Metallicity gradients of the stellar population from the EAGLE simulation
Tissera, Patricia
Rubens E. G. Machado (UTFPR), Patricia B. Tissera (UNAB), Yetli Rosas-Guevara (UNAB)Metallicity gradients of the stellar population hold information aboutthe chemical evolution and the assembly of disc galaxies. We aim toexplore metallicity and age gradients as a function of redshift in acosmological context. Using disc galaxies from the EAGLE simulation,we analysed metallicity and age gradients of the stellar populationwithin the effective radii up to redshift z=2.5. Preliminary resultsindicate that the median metallicity gradients are generally verysmall. At higher redshifts they are also flat, although the dispersionis larger. There seems to be little dependence on either stellar massor effective radius. The median age gradients, on the other hand,decrease with stellar mass. Some low-mass galaxies even exhibitpositive age gradients.
The stellar haloes beyond the discs
Tissera, Patricia
Andrea Mejias (UNAB), Patricia Tissera (UNAB)The stellar haloes are now considered common components of galaxies, regardless of morphology, this haloes such as that of the Milky Way or Andromeda, show clear signals of satellite accretion.In the context of a hierarchical clustering scenario such as Lambda Cold Dark Matter models, stellar haloes are predicted to form principally by the accretion of satellites galaxies with a contribution of in situ stars. The latter are concentrated in the central region and include disc-heated stars.We use the Milky-Way mass-sized haloes of the Aquarius Project which provide us six haloes of galaxies similar in mass to that of the Milky Way.In this poster we focus on the analysis of halo stars located close to the disc plane.We carry out a comparative analysis of the distribution of age, metallicity and corotating and counterotating components of these populations.
Geodetic VLBI, Earth rotation and the Sagnac effect
Titov, Oleg
Geodetic Very Long Baseline Interferometry (VLBI) measures the group delay and phase delay rate in the barycentric reference frame. These both observables are sensitive to the geocentric velocities of the telescopes. This results in a non-zero closure delay and closure delay rate (as a sum of the three values around the closed triangle of baselines). The group delay equation includes a term consistent to the Sagnac effect (usually applied to the ring laser interferometer technique or GNSS modeling) and, therefore, could be used to estimate the instantaneous vector of the Earth angular velocity. However, the delay rate suggests more effective way to do this job because it manifests as the Sagnac effect in the primary term of the relativistic model. The instantaneous vector of the Earth angular velocity is estimated with accuracy of 10-12 - 10-13 1/sec with a small set of modern geodetic VLBI data. This provides an opportunity to detect the Thomas (geodetic) precession, the Lense-Thirring effect (frame-dragging) and even the angular rotation of the Galaxy using the full 40-year set of geodetic VLBI observations.
High-resolution radio imaging of two luminous quasars beyond redshift 4.5
Titov, Oleg
Radio-loud active galactic nuclei in the early Universe are rare. The quasars J0906+6930 at redshift z=5.47 and J2102+6015 at z=4.57 stand out from the known sample with their compact emission on milliarcsecond (mas) angular scale with high (0.1-Jy level) flux densities measured at GHz radio frequencies. This makes them ideal targets for very long baseline interferometry (VLBI) observations.We present sensitive high-resolution VLBI images of J0906+6930 and J2102+6015 at two observing frequencies, 2.3 and 8.6 GHz. The data were taken in an astrometric observing programme involving a global 5-element radio telescope array. We combined the data from 8 di erent epochs from February 2017 to April 2018. For one of the highest-redshift blazars known, J0906+6930, we confirm that this source has a sharply bent helical inner jet structurewithin about 3 mas from the core. The quasar J2102+6015 shows an elongated radio structure in the east–west direction within the innermost ~2 mas that can be described with a symmetric 3-component brightness distribution model at 8.6 GHz. Analysis of individual positions of J2102+6015 collected since 2012 reveals a tiny proper motion of 12.8 +/- 2.3 muas/y to the eastern direction confirming the conclusion obtained with a limited imaging data. Our results demonstrate that VLBI observing programmes conducted primarily with astrometric or geodetic goals can be utilized for astrophysical purposes as well.
Infrared properties of optically-faint radio galaxies/quasars discovered by Subaru/HSC and FIRST
Toba, Yoshiki
We present physical properties of optically-faint (i_AB > 21) radio galaxies/quasars newly discovered by Subaru Hyper-Supreme Cam (HSC) and VLA Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. By cross-matching 3579 HSC-FIRST galaxies/quasars (Yamashita et al. 2018) with Wide-field Infrared Survey Explorer (WISE) data, we selected 2354 radio galaxies/quasars with infrared (IR) data. We investigated their mid-IR properties and compared those with optically-bright (i_AB < 21) FIRST galaxies/quasars detected by the Sloan Digital Sky Survey (SDSS). We found that (i) 3.4 micron - 4.6 micron color and 4.6 micron - 12 micron color of HSC-FIRST galaxies/quasars are redder than those of SDSS-FIRST galaxies/quasars given a redshift, and (ii) the dust extinction, E(B-V) of HSC-FIRST galaxies/quasars that is derived from the SED fitting of optical and near-IR data, are systematically larger than those of SDSS-FIRST galaxies/quasars. These results suggest that HSC-FIRST galaxies/quasars are more dusty and IR luminous objects heated by strong SF/AGN radiation. We also investigated the physical properties of HSC-FIRST galaxies/quasars such as stellar mass and star formation rate (SFR) based on the SED fitting to the multi-wavelength dataset of u-bad (KiDS DR3), near-IR (VIKING DR3), mid-IR (ALLWISE), and far-IR (Herschel PSC).
Synthetic Observations of A Young Forming Circumstellar Disk
Tomida, Kengo
Angular momentum transport is one of the key processes in star and circumstellar disk formation. While many physical processes such magnetic braking, outflows and gravitational torque via asymmetric structures can contribute to angular momentum transport, their relative importance must be constrained by observations. Also, since observations of young circumstellar disks are developing rapidly especially with ALMA, realistic theoretical models that can be directly compared with observations are highly demanded. Synthetic observations with post-processing radiation transfer calculations allow us to derive physical quantities such as spectral energy distribution and intensity distribution from hydrodynamic simulations. We perform a long-term resistive MHD simulation of star and circumstellar disk formation. The formed circumstellar disk is initially small but grows as accretion continues. A pair of spiral arms are formed due to gravitational instablity, and they transform angular momentum efficiently. These spiral arms disappear by winding on a short dynamical time scale, but they form recurrently as gas accretion makes the disk unstable again. We perform synthetic observations and compare our results with the ALMA observation of Elias 2-27 (Perez et al. 2016), whose circumstellar disk has a pair of grand-design spiral arms. We find that the spiral arms are in good agreement with material spiral arms formed by gravitational instability. It is important to consider such a massive disk as the initial and boundary conditions for planet formation.
On a new empirical calibration of synthetic stellar libraries
Torelli, Marianna
Synthetic stellar libraries are quite popular to constrain the stellar populations (age and metallicity distribution) of unresolved systems. However, they are typically based on theoretical Spectral Energy Distributions (SEDs). The main aim of my work is to build up empirical synthetic stellar libraries covering a broad range in ages (globular clusters, old open clusters), chemical compositions (iron, alpha, CNO) and dynamical properties (nearby dwarf galaxies). I am taking advantage of 70 globular clusters for which we have already secured multi-band optical (UBVRI) photometry collected with both ground-based and space telescope (HST). They will allow us to improve our SED fitting codes to deeply investigate high redshift galaxies. I am planning to present preliminary results concerning the sample selection and the difference with canonical models. Finally, I am also planning to discuss the role that accurate and deep NIR photometry collected with MICADO at E-ELT will play in this context, and in particular, in constraining the Star Formation History (SFH) of high redshift galaxies.
The star formation history in the M31 galaxy derived from Long-Period-Variable star counts
Torki, Maryam
The determination of the star formation history is a key goal for understanding of galaxies. In this paper we developed a new method to reconstruct the star formation history in the Andromeda galaxy. This galaxy is a nearest and biggest spiral galaxy to the milky way and this is a great chance for us to study the formation and evolution of this galaxy. Over findings suggers that long period variables stars are the powerful tool for estimate the star formation history in nearby galaxies because of their evolutionary phase. In this method at first we convert-k band magnitude of evolved stars to mass and age and from this we reconstruct the star formation.
The origin of interstellar asteroidal objects like 1I/2017 U1 ’Oumuamua
Torres, Santiago
We study the origin of the interstellar object 1I/2017 U1 ’Oumuamua by juxtaposing estimates based on the observations with simulations. We speculate that objects like ’Oumua- mua are formed in the debris disc as left over from the star and planet formation process, and subsequently liberated. The liberation process is mediated either by interaction with other stars in the parental star-cluster, by resonant interactions within the planetesimal disc or by the relatively sudden mass loss when the host star becomes a compact object. Integrating ’Oumua- mua backward in time in the Galactic potential together with stars from the Gaia-TGAS cat- alogue we find that about 1.3 Myr ago ’Oumuamua passed the nearby star HIP 17288 within a mean distance of 1.3 pc. By comparing nearby observed L-dwarfs with simulations of the Galaxy we conclude that the kinematics of ’Oumuamua is consistent with relatively young objects of 1.1–1.7 Gyr. We just met ’Oumuamua by chance, and with a derived mean Galactic density of ~ 3 × 105 similarly sized objects within 100 au from the Sun or ~ 1014 per cubic parsec we expect about 2 to 12 such visitors per year within 1 au from the Sun.
Dynamics of the Oort Cloud in the Gaia Era
Torres, Santiago
Comets in the Oort cloud evolve under the influence of internal and external perturbations, from giant planets to stellar passages, the Galactic tide, and the interstellar medium. Using proper motions, parallaxes and radial velocities from Gaia DR2 and combining them with the radial velocities of several catalogues, we constructed a catalogue of the closest stars to the Sun within 50pc. Then we calculated the closest encounters that the Sun has had in the recent past and will have in the near future, with a special focus on the stars within 2pc from the Sun, for being the ones with major impact to the Oort cloud. We constructed an artificial Oort cloud and by using the closest stars found it, we investigated the secular effect over the Oort cloud in +/-10Myr. We will present our latest results.
An outstanding Star Party in Mexico and Latin America - November 2017
Torres-Peimbert, Silvia
As it has been the practice since the International Year of Astronomy 2009, simultaneous star parties were organized in Mexico. Last year November 25th, 100 different sites throughout the country participated. There were also five sites in Colombia and two more in Argentina. The number of participants this year, in all sites involved, was very large, more than 200,000 persons. Altogether, since 2009, the total number of participants of this yearly event is well above a million and a half persons.As part of this celebration a day long fair at the Universidad Nacional Autonoma de Mexico campus in Mexico City has taken place in 2017. On this site the celebration has traditionally been outstanding. On this particular one, there were 850 volunteers, 220 telescopes installed, 59 thematic tents, 395 public lectures, and a large number of astronomy related activities; altogether 80,000 people attended. This star party has become an expected event by the local general public.
The temperature and density from permitted O II lines in the planetary nebula NGC 7009
Torres-Peimbert, Silvia
We have used spatially- and velocity-resolved spectroscopy of NGC 7009 to determine the electron temperature and density structure based upon O II lines. We find a strong gradient in the O II -based electron temperature. It agrees with the electron temperature determined by collisionally-excited lines in part of the nebular volume, but also differs by more than 6,000K in other parts of the nebular volume. This result supports the hypothesis that NGC 7009 contains two plasma components, one of which emits collisionally-excited lines and the other that does not. For the component that does not emit collisionally-excited lines, we find a lower limit to the electron density of 104 cm-3 from the O II lines, which is higher than derived from collisionally-excited lines. We are unable to determine whether the two plasma components are in pressure equilibrium from our data, but there exist temperature and density combinations that allow this equilibrium for temperatures between 600 K and 6,000 K. For most of the temperature and density conditions allowed for the component without collisionally-excited lines, its mass of O+2 is less than that of the plasma component that emits collisionally-excited lines.
Low mass star formation in quiet and violent environments
Toth, L. Viktor
The formation of Solar System might happened in a violent environment. On the other hand solar mass stars may also form without external trigger. Recently Galactic cold clumps (PGCC) were located based on Planck all sky mapping data. Our radio spectral line observations uncovered the distribution and physical properties of cold interstellar medium in dozens of PGCCs. These are faced to all kinds of external effects being embedded into various environments. Heiles cloud 1 also known as L1251, and Heiles cloud 2 bearing TMC-1 will be shown as two examples of low mass star forming clouds in different environments.
Chemistry in HCL2
Tóth, L. Viktor
While there are excellent models for star formation it is till a challenge to test the duration of the phases of the evolution of clouds from the low density diffuse phase to the dense star forming cores. One possibility to derive the ages of interstellar clouds is to use the fact that the chemical composition of these objects is also varying with time.One of the most important environmental effects on the actual chemistry of an interstellar cloud is the energy density of the ultraviolet radiation field it is exposed to, other important parameters are density and temperature. We observed lines and derived the column densities of two time sensitive chemical species NH3, and HCO+ in the most massive part of the Taurus Molecular Cloud complex, the HCL 2. We may assume that the UV field is approximately the same for the parts of HCL 2. The other physical conditions were derived from multi-wavelength archival data, including Herschel far-infrared and CO spectral line data.We used the UMIST-2012 gas phase network with 467 species and the 6173 possible reactions between them to determine the time dependent chemical evolution in clouds with physical parameters similar to the parts of HCL 2. We compared the derived time dependent relative abundances of NH3, and HCO+ to our observed density ratios, and estimated the chemical ages of the sub-clouds of HCL 2.
The super-Eddington X-ray outburst of SMC X-3: Nearby ultra-luminous X-ray sources and the orbital parameter distribution of Be/X-ray binaries
Townsend, Lee
In 2016, SMC X-3 underwent an long-duration X-ray outburst of extreme brightness. It's luminosity peaked at 1.2 x 10^39 erg/s, making it one of the closest known ultra-luminous X-ray sources (ULX). In light of the recent discovery of ULX pulsars, finding similar systems in nearby galaxies is important as it allows a much more detailed study of the multi-wavelength properties of these systems. I will highlight the recent ULX outburst of SMC X-3 and discuss the other known or potential ULX systems in the Magellanic Clouds.The second part of my talk will focus on the binary parameter distribution of Be/X-ray binaries (BeXRB). I will review the current distribution of parameters in the Galaxy and in the Small Magellanic Cloud (SMC), highlighting the similarities and differences in these populations. SMC X-3 is the 8th system in the SMC to have its orbital parameters determined, adding to the growing number of binaries studied outside of the Milky Way.
Multi-wavelength Observations of Dual AGN (MODA) – the cases of Mrk463 and NGC6240
Treister, Ezequiel
Nowadays, we know that most Active Galactic Nuclei (AGN) are observed to be triggered by internal, secular processes and minor galaxy mergers. Nevertheless, the most luminous AGN – quasars (QSOs) – are hosted by major mergers. In addition to that, AGN activity in mergers is seen to peak at nuclear separations shorter than 10kpc. Non intuitively, the number of AGN pairs found at those distances (also known as dual AGN) are not frequently identified: only a few percent of mergers host such systems. Although technical limitations may play some role in this, system-intrinsic physical properties definitely will (e.g., AGN duty-cycle shorter than that of mergers; extreme nuclear obscuration; etc...). As a result, we are conducting the Multi-wavelength Observations of Dual AGN (MODA) survey targeting 17 known dual AGN systems at z<0.1 and aims to characterize their physical properties of the ionized, atomic, and molecular gas, as well as the dust. This presentation will present the results on Mrk463 reported by Treister et al. (2018), where optical, near-infrared and ALMA millimeter observations were brought together to reveal the large and small scale properties of the system. Specifically, the evidence for a biconical outflow and ionized material outflowing at >600 km/s (a rate in rough balance with the molecular gas infalling onto the system), and an AGN-photoionized region indicating that the Eastern nucleus was up to 20 times more active in the past 10's thousand years. In addition, the current work being done toward NGC6240 will also be revealed, where ALMA data is resolving the gas bridging the two AGN nuclei down to ~25pc scales.
Dust-production of AGB stars in the Solar Neighborhood
Trejo, Alfonso
Asymptotic Giant Branch (AGB) stars dominate the total dust injection into the interstellar medium (ISM) of galaxies. Studies providing total dust injection rates in the Milky Way (Jura & Kleinmann 1989) and nearby galaxies (Riebel et al. 2012; Srinivasan et al, 2016) show the importance of accurately estimating this contribution.In this work we revisit the total dust mass-loss rate from AGB stars in the Solar neighborhood. Such an update is necessary, especially for an all-sky sample, as contrary to recent and old studies.One of the challenges for Galactic and dusty AGB sources is the distance determination, which we are primarily interested in, as they are the highest mass-loss rate objects. Using present-day all-sky infrared facilities (WISE, 2MASS, AKARI). We constructed spectral energy distributions for all the AGB candidates withinwithin 2 kpc from the Sun, which we fit with models from the GRAMS grid (Sargent, Srinivasan & Meixner 2011; Srinivasan, Sargent & Meixner 2011) to estimate their dust-production rates.We find an integrated dust production rate of ~ 4 X 10^-5 Msun/year or an average of ~ 2 X 10^-8 Msun/year per object is obtained. We compare our results to those of the Magellanic Clouds and other Local Group galaxies, for which the distance determination problems do not exist. Separating the contribution into C- and O-rich AGB is alsopresented and is compared with estimates from the LMC and SMC as well.This work presents new insights into the contribution of low- and intermediate-mass stars to the ISM, and the discrepancy between the dust produced by AGB stars and the estimated reservoir in the ISM.
A Comparison of Galaxy Spiral Arm Pitch Angle Measurements Using Manual and Automated Techniques
Treuthardt, Patrick
The established relationship between galaxy spiral arm pitch angle (PA) and supermassive black hole (SMBH) mass provides a powerful and time-efficient means of estimating the mass of the black hole found in the nucleus of most galaxies. A single, uncalibrated, broadband image with sufficient contrast provides the data necessary to determine SMBH mass via the PA-SMBH relationship and predict which galaxies might harbor intermediate mass black holes (MBH < 105 M?). In order to better understand the accuracy of different methods used in measuring spiral arm PA in galaxies, we tested four different PA measurement techniques including SpArcFiRe, the Ringermacher & Mead (RM) formula, standard input P2DFFT, and P2DFFT with input from visually traced arms. The tests were conducted on images of simple, artificially generated logarithmic spiral arm galaxies (toy models) of various pitch angles, numbers of arms, and arm widths. We further tested three of the techniques (sans RM) on a set of 9 real spiral galaxy images of various morphologies ranging from non-barred to strongly barred and from early- to late-type. We find that our tracing method in combination with P2DFFT generates the most accurate results with the toy models. For the set of real galaxies, SpArcFiRe and P2DFFT with traced arm input produced consistent results. Improvements to standard input P2DFFT are also explored.
Spatially resolved solar spectral irradiance in NUV with Solar Ultraviolet Imaging Telescope (SUIT) on board Aditya-L1 mission
Tripathi, Durgesh
In order to fully comprehend the Sun-climate relations, it is of paramount importance to measure and monitor spatially resolved solar spectral irradiance in the wavelength range of 200 - 400 nm. The solar radiation emitted in within this wavelength range is known to play important role in the chemistry of Oxygen and Ozone in the stratosphere of the Earth’s atmosphere. The Solar Ultraviolet Imaging Telescope (SUIT) on board the first Indian solar mission Aditya-L1 aims to perform such measurements. SUIT will provide near-simultaneous full disk images of the Sun with a spatial resolution of 1.4 arcsec using 11 filters sensitive to different wavelengths within 200-400 nm. Three out of 11 filters cover the wavelength range of 200-242 nm, 242 - 300 nm and 320-360 nm. The other 8 filters are chosen such that they slice through different heights in the solar atmosphere, thereby providing an opportunity to study the processes involved in the transfer of mass and energy within the lower solar atmosphere.
PAGaN: Revealing the Nature of Blazar Radio Cores through Multi-Frequency Polarization Observations with the Korean VLBI Network
Trippe, Sascha
We study the linear polarization of the radio cores of eight blazars simultaneously at 22, 43, and 86 GHz with observations obtained by the Korean VLBI Network (KVN) in three epochs between late 2016 and early 2017 in the frame of the Plasma-physics of Active Galactic Nuclei (PAGaN) project. We investigate the Faraday rotation measure (RM) of the cores; the RM is expected to increase with observing frequency if core positions depend on frequency due to synchrotron self-absorption. We find a systematic increase of RMs at higher observing frequencies in our targets. The RM–? relations follow power-laws with indices distributed around 2, indicating conically expanding outflows serving as Faraday rotating media. Comparing our KVN data with contemporaneous optical polarization data from the Steward Observatory for a few sources, we find indication that the increase of RM with frequency saturates at frequencies of a few hundreds GHz. We claim that blazar cores become fully transparent, with no more core-shift occurring, above that frequency. This implies that, at high frequencies, the radio core is a standing recollimation shock. The Faraday screens of our sources seem to be external to their jets; a sub-relativistic sheath surrounding a relativistic jet is a promising candidate for the location of the Faraday rotating medium. We detect sign changes in the observed RMs of CTA 102 on time scales of months, which might be related to new superluminal components emerging from its core undergoing acceleration/deceleration and/or bending. We see indication for quasars having higher core RMs than BL Lac objects, which could be due to denser inflows/outflows in quasars.
The Star-forming Progenitors of Local Passive Galaxies Quenched Primarily through Starvation
Trussler, James
Star-forming galaxies can be transformed into passive systems by processes that quench star formation, such as the halting of gas accretion or the rapid removal of gas. However, it remains unclear which processes are the most significant, primary drivers of the SF-passive bimodality. We address this issue by analysing the systematic difference in stellar metallicity between star-forming, green valley and passive galaxies, using the statistical power of SDSS DR7 to study 70,000 galaxies. We use stellar metallicity differences as a tracer of quenching mechanisms, enabling us to distinguish between slow (e.g. starvation) and rapid quenching (e.g. sudden gas removal). Our analysis reveals that the progenitors of local passive galaxies quenched primarily through starvation, over a mass-dependent quenching timescale that decreases from 3 Gyr at log M = 9.5 to 1.5 Gyr at log M = 11.0. For low-mass (log M < 10) progenitors, we find that models including a combination of starvation and minor outflows best match the data, suggesting that both starvation and weak outflows played an important role in quenching the progenitors of low-mass passive galaxies. On the other hand, we find that models including rapid gas removal are inconsistent with observations, indicating that powerful outflows played a minor role in quenching the progenitors of local passive galaxies. Furthermore, our analysis shows that local green valley galaxies have typically been quenching through starvation for 2.5 Gyr, which is consistent with the stellar age difference between local green valley and star-forming galaxies. Finally, we investigate the role of the environment in galaxy quenching. We find that the quenching of central galaxies is independent of environment, while we find that quenching by strangulation preferentially operates on low-mass satellite galaxies in high density environments. We intend to apply the same methodology to study spatially-resolved stellar metallicities in MaNGA galaxies.
Accretion-Ejection MHD simulations in Protostars
Tsinganos, Kanaris
By using as initial conditions analytical self similar solutions for MHD outflows, we have modeled the magnetosphere of young, low mass, stars with a stellar jet surrounded by accretion columns and an equatorial static dead zone connecting the star to the disk. The use of analytical solutions as initial conditions allows to attain steady or quasi steady solutions within a few stellar rotations showing that such solutions are remarkably stable. The simulations are performed with the PLUTO code on supercomputers, such as OCCIGEN on GENCI.In the simulations we vary the ratio of the mass accretion rate to the mass loss rate and also the size of the static dead zone. We have found that by varying this ratio within a range of observed values, we obtain a bimodal final state. Either a state wherein the stellar jet is separated from the accretion zone by a relatively low density, force-free region is obtained, or, we get a state where the low density region is replaced by episodic mass ejection coming from the disk and bouncing on the stellar atmosphere, creating thus a type of coronal mass ejections. Hence, the presence of episodic magnetospheric ejection is not compulsory but it depends on the value of this ratio. It is interesting that this ratio is similar to the observed range of ratios in T Tauri systems, i.e., for a mass accretion rate exceeding 15 to 20 times the mass loss rate. Thus, it is very likely that such a bimodal behavior may be observed in T Tauri environments. By further increasing the accretion rate, we are investigating the transition from the T Tauri to the FUOR systems. In that case we conjecture that the cylindrically collimated jet may be replaced by a conical wind, which can also be explored with the same numerical technique.
Relativistic MHD rotating spine jets in Kerr metric
Tsinganos, Kanaris
By using a nonlinear separation of the variables of the general relativistic MHD equations, we construct a semi-analytic model of magnetohydrodynamic jets around rotating black holes. The model provides axisymmetric solutions, which describe the outflow in the spine jets of Active Galactic Nuclei (AGN) or Gamma Ray Bursts (GRB). These spine jets start at the exobase, at some distance above the black hole. The composition of the jet can be hadronic, if the plasma originates from the accretion disk, or leptonic if it is induced by in-situ pair production. Both hypotheses can be tested in order to distinguish which one is more realistic for the composition of the spine jet in terms of temperature and expected radiation. This model allows to constructing full MHD solutions describing the plasma outflow from the horizon to infinity.
Activities during the year 2019 for IAU100 in Athens/Greece
Tsinganos, Kanaris
The activities for IAU100 will be organized in the Athens metro area in Greece before and during the European Researchers’ Night on 27-28 September 2019. They will be part of the International Astronomical Union’s (IAU) 100th anniversary celebrations in 2019. The venues which will participate are the Observatory of the University of Athens (UoA), The Planetarium of the Evgenidis Foundation, the National Observatory of Athens (NOA), the Stavros Niarchos Foundation Cultural Cente, Several Schools in the Athens area, e.g. the Arsakeia-Tositseia schools. Activities will include: Preparation of a leaflet with the program of the various activities, Public outreach talks and lectures popularizing recent results of modern astronomy to the general public and covering the main areas of contemporary astrophysics and space physics, Observation of the night sky at the participating Observatories, School visits, in Athens wherein researchers will visit selected top schools of the Athens area in the Spring of 2019 to create awareness among the students about the potential of astronomy and encouraging them to consider astronomy and space science as a career choice and asso perform in the schools simple astronomy experiments to increase the excitement for science, Hands-on astronomy activities corner, for children and families at the premises of the National Observatory of Athens (NOA) and the Stavros Niarchos Foundation Cultural Center using the facilities and experience of the expert personnel of the visitor centers of NOA, Creation of a dedicated web site at the officiall site of the Hellenic Astronomical Society (Hel.A.S.), and also announcements at the web sites of the UoA and NOA, Activation of contacts with newspapers, magazines and TV and mailing lists of the amateur astronomers, Organisation of a special edition of the Hel.A.S. journal Hipparchos for IAU100.
ALMA View of the IR Stars in the Vicinity of Sgr A*
Tsuboi, Masato
The Galactic center is a nucleus of the nearest spiral galaxy, Milky Way. It harbors the Galactic center black hole, Sgr A*, which has a vast mass of M~4x 10^6 Mo. The proximity of D~8kpc makes it possible to depict the structures less than 1000 AU using ALMA. Therefore, the observation of the Galactic center is important for all studies of any galactic nuclei as a template. There are ~100 OB and WR stars within r<0.5 pc of Sgr A*. This is called the Nuclear star cluster (NSC). It would be difficult to form stars near Sgr A* in a way by which stars are usually formed in the disk region because of both the tidal force of Sgr A* and the strong Lyman continuum radiation from the cluster itself. In any formation mechanism for such cluster, there may be some traces in the motion and distribution of the stars around Sgr A*. Such studies have been performed by IR telescopes (IRTs). However, ALMA is superior to them as a precision astrometry tool for the NSC because ALMA can always observe the position of Sgr A* but IRTs can observe it only at the flare.We observed the NSC using ALMA at 230 and 340 GHz. The angular resolutions using “uniform weighting” are 0".03 and 0".09, respectively. The well-known IR objects, IRS16 cluster, IRS13E complex, IRS21 cluster and so on have been first detected in the sub-millimeter continuum map.We derived the proper motions of the members of the IRS13E complex from the comparison of these observations on trial. Because ALMA has potentially a smaller beam size than VLA, astrometry with ALMA is promising.
Sporadic r-process events found in the Draco dwarf spheroidal galaxy
Tsujimoto, Takuji
One of the last frontiers in nuclear astrophysics is identifying the origin of elements produced through the rapid neutron-capture process (r-process). Although modelling of core-collapse supernovae and compact object mergers has been intensively conducted as plausible candidates of the r-process site, no evidence for these events has been thus far obtained by direct observations. On the other hand, recent studies support that stellar record on elemental abundances in faint satellite galaxies is crucial to assess its nature because such small stellar systems could be significantly affected by a single r-process event, as found in the ultra-faint dwarf galaxy Reticulum II. The smallness of the systems, however, prevents us from collecting a sufficient number of stars from individual satellites. Hence, it remains unclear whether the discovery of a remarkable-r-process-enrichment event in the Ret II catches the nature of r-process or an exception. Here we report on r-process abundances obtained by high-resolution spectroscopy for twelve metal-poor stars in the Draco dwarf spheroidal galaxy in a narrow metallicity range of -2.5<[Fe/H]<-2. We find that these stars are clearly separated into two groups by r-process abundances with a difference by one order of magnitude. Our finding suggests that the high r-process group is formed by a sporadic r-process event, indicating that a sporadic event discovered for the Ret II is not unique but is also found for the Draco. In addition, the r-process feature at less metallicity, i.e., for earlier epochs of the Draco, implies the presence of at least one separate event lifting a primordial r-process abundance to that close to the low r-process group. Including the object with no detection of r-process elements by previous study, we identify three populations with different r-process abundances, built by two r-process events enriching gases with more than one-order different levels, one of which is not found in the Ret II.
Low-level accretion onto highly magnetized neutron stars
Tsygankov, Sergey
In my talk I will consider the case of transient highly magnetized neutron stars accreting in a broad range of rates, focusing on their behaviour in the very end of the outbursts. At low mass accretion rates the centrifugal inhibition of the accretion (aka “propeller effect”, one of the most direct evidence of the ultra-strong magnetic field presented in the vicinity of the neutron stars) was discovered in a few systems. I will review observational manifestations of the propeller effect in X-ray pulsars with broad range of the magnetic fields from 108 to 1014 G with main focus on our recent discoveries. In the second part of my talk I will introduce a model explaining the existence in some X-ray pulsars of an unexpected quasi-stable state characterized by the accretion rate of ~1014-1015 g/s. We associate this state with the accretion from cold (non-ionised) disc with temperature below ~6500 K. We argue that a transition to such accretion regime should be observed in all X-ray pulsars with certain combination of the rotation frequency and magnetic field strength.
Cosmological simulations in Fourier space
Tugay, Anatoliy
We propose a new method of simulation of large-scale structure of the Universe. We use hydrodynamical equations of dust (dark) matter in own Newtonian gravitational field. Instead of N-body simulation we use Fourier harmonics for density contrast and potential of irrotational velocity field. We consider periodic structure of plane waves in 100 Mpc cube. We obtained equations for harmonics in 3D case and prepared a code for simulation. In this work we described the regimes of runaway, when quasinonlinear approach becomes irrelevant. Further development will allow to test Wick theorem for average values and to constrain the methods of perturbation theory in cosmology. Simulated matter distribution will be compared with observational data such as power spectrum of QSO Ly-alpha forest and correlation functions of galaxies.
The Shared Evolution of Stars and their Planetary Systems
Tylor, Christopher
The prevalence of solar neighbourhood exoplanets enables detailed studies of the evolution of stars and their planets as evolving systems. This approach, in turn, informs the search for habitable exoplanets and supports proxy studies of solar system evolution. Here we present an overview of our research that includes exoplanet detections and characterisations, stellar magnetic field mapping and wind modelling, and dynamical modelling of solar system bodies and exoplanets. Our work is focused on combining stellar and exoplanet surveys from existing facilities, as well as the development of new Australian facilities for enhanced surveys. These new facilities are Mt Kent Observatory’s MINERVA-Australis telescope array designed to support the NASA Transiting Exoplanet Survey Satellite mission, an on-site SONG asteroseismology node, and the 3.9m Anglo-Australian Telescope’s new Veloce spectrograph. These new facilities will support ongoing research into stellar magnetism and activity, and the detection, characterisation and evolution of planetary systems around active stars.
Systematic study of Quasar Radiative Feedback in High-z Universe
Uchiyama, Hisakazu
High-z luminous quasars are thought to appear through a major merger of gas-rich galaxies. It is, hence, speculated that they preferentially reside in galaxy overdense regions, where galaxy merger frequently happens. On the other hand, there could be an important feedback process from quasar to galaxies, photoevapolation, which could be effective in protocluster regions around quasars, especially for low-luminosity galaxies. Low luminous galaxies are closely bound up with the surrounding inter-galactic medium. The photoionization heating by strong ultra-violet (UV) background from quasar evaporates the collapsed gas in the halo and in hibits gas cooling. We have carried out deep and wide field imagings with Suprime-Cam targeting for 11 quasar fields in order to systematically study the photoionization effect for low luminous galaxies at z~2-3. The quasars are selected to have various properties, such as radio-quiet/loud, less/more massive black hole mass, and bright/faint in order to examine a variation of the ionization effects. We selected Lyman alpha emitters (LAEs) in each quasar fields to obtain 1297 LAEs in total. The vicinity of quasars was defined by the region where the local UV radiation is expected to be enhanced compared with the UV background. We found that LAEs with high rest-equivalent width of Lyman alpha emission, EW0 ? 150A or faint UV luminosity, MUV ? -17.0, are averagely segregated in the vicinity of the quasars. The value of EW0 or MUV corresponds to the notably smaller halo mass Mh ~ 109 - 1010M?. The LAEs with such halo mass are expected to be subjected from quasar photoevaporation in a hydrodynamical simulation. The feedback seems to be less effective in Hyper luminous or dusty quasar fields, implying that the quasars are thought to be in the early stage of quasar active phase. In addition, it is found that the quasar pair tend to reside in the LAE overdense regions.
Planetesimal Formation at the Dead-zone Inner Boundary and Its Observational Signatures
UEDA, Takahiro
The inner region of protoplanetary disks is the birthplace of rocky planetesimals and planets. One preferential site of rocky planetesimal formation is the inner edge of the dead zone. Across the dead-zone inner edge, the turbulent viscosity arising from magneto-rotational instability steeply decreases from inside out, resulting in a local maximum in the radial profile of the gas pressure. The pressure maximum traps solid particles and the local dust-to-gas mass ratio increases, leading to rocky planetesimal formation via the streaming instability.We performed simulations of dust and gas disk evolution with a broad range of the critical fragmentation velocity of silicate dust and the strength of turbulence in order to investigate the dust-pileup at the dead-zone inner boundary. Around the dead-zone inner boundary, dust particles are easy to fragment into small particles because of its high temperature, which interferes with the dust-pileup. We derived criteria for the dust-pileup as a function of the critical fragmentation velocity and the strength of turbulence, and found that if the critical fragmentation velocity is 1 m/s, the classical alpha value for turbulent strenght in the dead-zone should be lower than 0.0003 to operate the dust-pileup. Using the dust distribution obtained above, we also performed the radiative transfer simulations with RADMC3D to construct a model of the inner region of protoplanetary disks including the effect of the dust-pileup. We found that if dust particles strongly concentrate on the dead-zone inner boundary, the dust-pileup acts as a optically thick dust wall which could be observed as a bright ring next to the bright ring of the inner rim of the dust disk. And also, this dust wall casts a shadow behind the dead-zone inner boundary, which can be extended up to 10 au. These characteristic structures could be tracers of the dust-pileup operating the planetesimal formation.
Comprehensive analyses of panchromatic data sets and photo-ionization modeling of PNe
Ueta, Toshiya
Planetary nebulae (PNe) have been favorite spectroscopic targets because their bright spectra are rich in emission lines. Recent opportunities in the far-IR/sub-mm have yielded spatially-resolved fine-structure line emission maps as well as thermal continuum emission maps for a sample of PNe, filling the remaining major spectral gap in this wavelength range of the multi-wavelength complement of the observational PN data. Exploiting panchromatic PN data from X-ray/UV to sub-mm/radio, we can now perform detailed quantitative investigations into the physical conditions of each of the ionized, atomic, and molecular gas and dust components in PNe with a minimum amount of assumptions. For example, we can perform an entirely empirical accounting of the circumstellar mass and abundances for each of the ionized, atomic, and molecular gas and dust components. We can then confront with the present theoretical understanding of evolutionary models and their roles in the chemical evolution of the Milky Way Galaxy and beyond. We will review our most recent attempts to comprehensively analyze the existing panchromatic data and generate one of the most comprehensive Galactic PN models ever constructed.
Planetary Nebulae detected in the AKARI Far-IR All-Sky Survey Maps
Ueta, Toshiya
The AKARI Infrared Astronomical Satellite produced the far-IR all-sky survey (AFASS) maps at roughly arc-minute spatial resolution, enabling us to investigate the whole sky in the far-IR for objects having surface brightnesses greater than a few to a couple of dozen MJy sr−1. Here, we verify that point-source photometry using the aperture correction method based on the empirical point-spread-function templates derived directly from the AFASS maps reproduces fluxes in the AKARI bright source catalogue (BSC) without any additional correction. This means that far-IR photometry of any source can be done by summing all the pixel values within an appropriately defined aperture of the intended targets in the AFASS maps. We then carry out aperture photometry for Galactic planetary nebula listed in the University of Hong Kong/Australian Astronomical Observatory/Strasbourg Observatory Hα Planetary Nebula (HASH PN) database, establishing far-IR fluxes for Galactic PNe including a few hundreds of additional PNe not listed in the BSC. A comparison between presently derived and BSC catalogue fluxes of these PNe suggest that direct aperture photometry with the AFASS maps should be done to obtain more accurate fluxes for sources that are not necessarily point sources such as PNe.
Herschel Planetary Nebula Survey Plus (HerPlaNS+)
Ueta, Toshiya
HerPlaNS+ (Herschel Planetary Nebula Survey Plus) is a far-IR imaging/spectroscopic survey and archival search of planetary nebulae (PNe) using the Herschel Space Observatory and Herschel Science Archive. In this presentation, we review our simultaneous investigations into both of the gas and dust components of a sample of Galactic PNe to comprehensively understand the physical properties of the nebulae. We find that there is a significant amount of flux in the far-IR emitted by PNe, which allows us to probe the photo-dissociated region of the target PNe, amounting to nearly 80% of the observed circumstellar mass. We will also exploit the high spatial resolution of the data to address the spatial distributions of each of the gas and dust components and the gas-to-dust mass ratio distributions.
Excavating Mass Loss History in Extended Dust Shells of Evolved Stars (MLHES): AKARI Mission Programme
Ueta, Toshiya
A far-IR imaging survey of the circumstellar dust shells of 144 evolved stars (mostly AGB stars) was performed as a mission program of the AKARI infrared astronomical satellite using its Far-Infrared Surveyor (FIS) instrument. This survey produced maps of roughly 10 arcmin by 40 arcmin or 10 arcmin by 20 arcmin areas of the sky around the target evolved stars in the four FIS bands at 65, 90, 140, and 160 microns. The detected extended dust shells, most of which show a departure from circular symmetry or offsets with respect to the central star, are found in dozen oxygen-rich and dozen carbon-rich objects. We report far-IR flux measurements made for these objects with the latest surface brightness correction method. Flux measurements for the central star and circumstellar shell are made separated for the first time to allow proper accounting of the amount of the circumstellar cold dust mass.
Morpho-Kinematics of the Circumstellar Environments around Post-AGB Stars
Ueta, Toshiya
We report our investigations into the morpho-kinematics of the circumstellar environs around post-asymptotic giant branch (post-AGB) stars representative of each of the two morphological classes, elliptical and bipolar, by means of ALMA observations using the 12CO and 13CO J=3-2 lines in relation to the distribution of neighboring continuum emission. The issue to be addressed is whether the central torus that seems to be generated by the end of the AGB phase is the consequence of intrinsic bipolar outflows carving out a cavity that defines the bipolar axis or the origin of bipolar outflows steered into the intrinsic biconical openings. We look into how the CO outflow velocity field differs in these nebulae, especially the latitudinal dependence of CO outflows. We also aim at resolving the longitudinal/azimuthal motion to see if the central torus exhibit the Keplerian rotation. The 12CO/13CO distribution is also used as a proxy of the 12C/13C abundance ratio distribution, which can vary due to the change in the 13CO abundance. Based on these pieces of dynamical evidence we will determine the role of the central torus in the CSE shaping during the AGB mass loss.
Comprehensive analyses of panchromatic data sets and photo-ionization modeling of PNe
Ueta, Toshiya
Planetary nebulae (PNe) have been favorite spectroscopic targets because their bright spectra are rich in emission lines. Recent opportunities in the far-IR/sub-mm have yielded spatially-resolved fine-structure line emission maps as well as thermal continuum emission maps for a sample of PNe, filling the remaining major spectral gap in this wavelength range of the multi-wavelength complement of the observational PN data. Exploiting panchromatic PN data from X-ray/UV to sub-mm/radio, we can now perform detailed quantitative investigations into the physical conditions of each of the ionized, atomic, and molecular gas and dust components in PNe with a minimum amount of assumptions. For example, we can perform an entirely empirical accounting of the circumstellar mass and abundances for each of the ionized, atomic, and molecular gas and dust components. We can then confront with the present theoretical understanding of evolutionary models and their roles in the chemical evolution of the Milky Way Galaxy and beyond. We will review our most recent attempts to comprehensively analyze the existing panchromatic data and generate one of the most comprehensive Galactic PN models ever constructed. The techniques and methodologies presented here can be extended to PNe beyond the Milky Way.
SPHEREx: Exploring the Origin and Evolution of Interstellar and Biogenic Ices
Unwin, Stephen
Many of the most important building blocks of life are locked in interstellar and protoplanetary ices including H2O, CO, CO2, and CH3OH. The cores of dense molecular clouds and the mid-plane of protoplanetary disks contain much more of these species in the form of ices rather than the gas phase. These key species are thought to be delivered to young planets through collisions with ice-bearing bodies. We wish to understand the role of cloud density and temperature, presence or absence of embedded sources, external FUV and X-ray radiation, gas-phase composition, and cosmic-ray ionization rate, on the ice composition of clouds at similar stages of evolution. Ultimately, our goal is to understand how these findings connect to our own Solar System. Currently, there are too few ice absorption spectra toward Galactic molecular clouds, less than 250, to permit an exploration of these effects and understand their contributions.SPHEREx would change that in a major way. It is an all-sky spectroscopic survey, currently in Phase A study, and it would provide optical and near-IR spectra, including the 2.5 to 5.0 µm region which encompasses the above biogenic ice features. With a spectral resolution of R=135 at the long-wavelength end, SPHEREx would deliver more than 105 spectra of illuminating background continuum sources for absorption spectroscopy with SNR = 100 per spectral resolution element, allowing detection and abundance measurement of several ice species. Having a huge number of such high-SNR ice absorption spectra would allow us to explore a wide variety of regions distributed throughout the Galaxy and reveal correlations between ice content and environment not possible with the limited sample currently available. SPHEREx would overlap with JWST beyond 2022, allowing SPHEREx to identify the most valuable ice sources for JWST follow-up.
Dust Structure around Asymptotic Giant Branch Stars
Upadhyay, Devendra Raj
This paper presents mass, temperature profile variation of Planck function in different region, energy out flow nature. The physics of the Interstellar medium (ISM) is extremely complex because the medium is very inhomogeneous and is made of regions with fairly diverse physical conditions. The composition of our galaxy is made of stars that provide a mass of approximately 1010-1011 solar masse and the ISM that provides a mass of nearly 109 solar mass. The conversion of the ISM to stars occurs typically at the star formation rate of 3 solar mass per year. The contribution of mass from the stars to the ISM occurs through supernovas (0.3 solar mass per year), staller winds of OB stars (0.08 -0.5 solar mass per year) and stellar winds from red giants (0.3 -1 solar mass per year). Approximately 99% of the mass of the interstellar medium is in the form of gas with the remainder primarily in dust. The asymptotic giant branch (AGB) is the region of the Hertzsprung-Russell diagram populated by evolving low to medium mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars (0.6–10 solar masses) late in their lives. Asymptotic giant branch (AGB) stars are generally classified as oxygen-rich (M-type) or carbon-rich (C-type) based on the chemistry of the photosphere and or the outer envelope.The physical phenomena such as dust, grain encountered in arena of ISM are inhomogeneous and anisotropy, the technique to solve such problem will be described.
We determine the distance 91 longer period Mira variables using 3.4µm Period Luminosity Relation
Urago, Riku
We present distance determination 91 for longer (log P > 2.7) period Mira variables (also known as OH/IR stars) covered with thick circumstellar dust shells. They are thought to be younger (~100Myr) population and could be a good tracer of the arm structure of our galaxy. However, they have thick dust circumstellar dust shells and are heavily reddened by circumstellar extinction.In order to estimate their distance using Period-Luminosity Relation (PLR), we need to consider the contribution of circumstellar extinction. In fact, the K band PLR for the Mira variables in LMC shows large scatter for the longer period and so it is difficult to estimate the distance. In contrast, the 3.4 um PLR we constructed using OGLE-III Mira variables in LMC shows a tight and linear correlation with the root mean square residuals of 0.29 mag for the period range of 2.0<logp<3.0. it is necessary to correct the only interstellar extinction when we apply the 3.4um plr for observed data because the 3.4um plr contains the contribution of circumstellar extinction in it. to estimate the amount of interstellar extinction, we need to know the intrinsic color of long period mira variables including circumstellar extinction. we examined the j-h and h-k colors of lpvs founded in the catalina sky survey. since css survey covers only high galactic latitude, we can reasonably assume that they suffer almost no interstellar extinction but includes the contribution of circumstellar extinction, if they have.="" we found that css lpvs show the linear sequence in the j-h and h-ks color diagram, and can estimate the amount of interstellar extinction comparing the position of apparent color with them.finally, we demonstrate the galactic distribution of 91 longer-period mira variables monitored at kagoshima university for which the 3.4um plr is applied and the interstellar extinction is estimated by our new method.<="" p="">
</logp<3.0.></p>
Observations of near-Earth object 2012 TC4 — The high-time resolution lightcurve with the Tomo-e Gozen camera
Urakawa, Seitaro
Explorations of Itokawa by Hayabusa space probe revealed that asteroids can take a rubble pile structure in which numerous pieces of the rock are weakly constrained by gravity. On the other hand, asteroids that are constructed from a piece of rock itself are called monolithic asteroids. The monolithic asteroids can be said to be the smallest unit object constructing rubble pile asteroids. To clarify the structural strength and/or the constituting substance of the monolithic asteroids help us to understand the physics of asteroids more deeply. A near-Earth object 2012 TC4 (hereafter TC4) was observed in 2012, and the rotation period was to be 12.24 minutes. The fast rotation indicated that TC4 was a monolithic asteroid. The observation opportunity of TC4 had come again in October 2017. This apparition was a very good observation opportunity to investigate the surface of monolithic asteroid that was not covered with the regolith layer. We conducted the observation campaign of TC4 at the Kiso Observatory, the Bisei Spaceguard Center, the Nishi-Harima Astronomical Observatory, the Nayoro City Astronomical Observatory, and the Anan City Astronomical Observatory. In particular, we succeed to obtain the high-time resolution lightcurve of TC4 with the Tomo-e Gozen camera. The Tomo-e Gozen camera is the world's first wide-filed CMOS camera mounted on the 1.05 m Schmidt telescope at the Kiso Observatory. The power spectrum from the period analysis shows the rotation period of 12.252 minutes, and the precession period of 8.479 minutes. Thus, TC4 is a tumbling asteroid. We made the shape model of TC4 from the lightcurve. When we assume TC4 is an ellipsoidal body, the normalized axis lengths are around 2.4, 1.6, and 1.0. Moreover, the visible and near-infrared photometry shows that the taxonomy class of TC4 is X-type. In this presentation, we present the observation results of TC4 and discuss the structural strength and/or the constituting substance of TC4.
Six decades of Astronomy in Nigeria: Successes and Challenges
Urama, Johnson
Modern astronomy came into Nigeria in the early 1960s. Prof John Gaustad had in 1962 introduced courses in astronomy in the Department of Mathematics of the University of Nigeria, Nsukka. About the same time, NASA’s space tracking facility was set up in Kano, Nigeria, for monitoring the missions of Gemini, Apollo and Skylab spacecraft. Presently, many Universities and Research Centres here are involved with teaching, research and outreach in astronomy and astrophysics. This work reviews the growth and progress of astronomy in Nigeria. Challenges and prospects are also discussed.
Radio/X-ray monitoring of the broad-line radio galaxy 3C 382
Ursini, Francesco
We present a unique radio/X-ray monitoring programme on the broad-line radio galaxy 3C 382, carried out in 2016 (Ursini et al., submitted). The campaign consisted of five joint XMM-Newton/NuSTAR observations, 20 ks each and separated by 12 days, performed simultaneously with VLBA. The high-energy (UV to hard X-rays) data are consistent with a two-corona scenario, in which the UV emission and soft X-ray excess below 1-2 keV are produced via thermal Comptonization in a warm (kT≈0.6 keV), optically thick (τ≈20) corona consistent with being a slab fully covering a nearly passive accretion disc, while the hard X-ray emission is due to a hot corona intercepting ~10% of the soft emission. These results are remarkably similar to those generally found in radio-quiet Seyferts (Petrucci et al. 2017), thus suggesting a similar inner flow structure. We also discuss the radio properties as seen with VLBA and their relation with the high-energy emission.
Soft gamma-ray radio galaxies: a high-energy view of jetted AGNs
Ursini, Francesco
We discuss results of a multiwavelength study of a sample of ~70 radio galaxies, selected in the soft gamma-ray band from INTEGRAL and Swift/BAT catalogues (Bassani et al. 2016), focusing on the X-ray view. This ongoing study is aimed at characterizing for the first time the broad-band emission of a statistically significant sample of radio galaxies, thus constraining the accretion/ejection mechanisms at play in AGNs. The sample contains a significantly larger fraction of giant radio galaxies (linear size > 0.7 Mpc) than typically found in radio surveys; a talk focused on the properties of these peculiar objects is also proposed at this meeting (Bruni et al.). Concerning the X-ray absorption properties of the whole sample (Panessa et al. 2016), an intriguing result is the lack of heavily absorbed (Compton-thick) sources, which could hint for a discrepancy between the average absorption properties of radio-loud and radio-quiet AGNs (Ursini et al. 2018). We also study the relation between X-ray absorption and 21 cm HI absorption, finding a higher probability of 21 cm detection among X-ray absorbed sources. This might in turn suggest that at least part of the X-ray obscuration is due to atomic hydrogen seen at radio frequencies, and that could reside at distances larger than the classical pc-scale torus.
Looking for new water-fountain stars
Uscanga, Lucero
We present simultaneous observations of H2O and OH masers, and radio continuum at 1.3 cm with the Very Large Array towards four water-fountain candidates. Water fountains (WFs) are evolved stars, in the AGB and post-AGB phase, with collimated jets traced by high-velocity H2O masers. Up to now, only 15 sources have been confirmed as WFs through interferometric observations. We are interested in the discovery and study of new WFs. A higher number of these of sources is important to understand their properties as a group, because they may represent one of the first manifestations of collimated mass-loss in evolved stars. These observations provide information about the role of magnetic fields in the launching of jets in WFs. Our aim is to ascertain the WF nature of these candidates, and investigate the spatial distribution of the H2O and OH masers.
The interplay between pulsation, mass loss, and third dredge-up: More about Miras with and without technetium
Uttenthaler, Stefan
We follow up on a previous paper (Uttenthaler, 2013) that showed that Miras containing the 3DUP-indicator technetium (Tc) in their atmosphere follow a different sequence of dust mass-loss rate as a function of pulsation period than Miras without Tc, where the dust mass-loss rate is probed by a near- to mid-infrared colour such as K-[22]. Contrary to what one might naively expect, Tc-poor Miras show redder K-[22] colours (i.e. higher dust mass-loss rates) than Tc-rich Miras at similar periods. In the meantime, the previous sample was extended and the analysis was expanded towards other colours and dust spectra. Near- and mid-IR photometry and ISO dust spectra of our stars were investigated where available. We analysed new optical spectra and expanded the sample by including more stars from the literature. We also investigated if the same two sequences can be revealed in the gas mass-loss rate. For this end, literature data of gas mass-loss rates of Miras and semi-regular variables were collected and analysed. Our results show that Tc-poor Miras are redder than Tc-rich Miras in broad range of the mid-IR, suggesting that the previous finding based on the K-[22] colour is not due to a specific dust feature. Probably, Miras without Tc experience a higher mass-loss rate than Miras with Tc. The relation log(M_dot,gas)=0.393x(K-[22])-7.431 is found to be valid in a broad range of K-[22] colour. We also find that the 13 µm feature disappears above K-[22]~=2.17, corresponding to M_dot,gas~=2.6x10-7 Msun/yr. Similar sequences of Tc-poor and Tc-rich Miras in the gas mass-loss rate vs. period diagram were however not found, most probably owing to limitations in the available data. Different hypotheses to explain the observation of two sequences in the P vs. K-[22] diagram are discussed and tested. We conclude that the interplay between pulsation, mass loss, and 3DUP deserves further attention.
Radio-Loud Unification: Multiple Radio Frequency Study
Vaddi, Sravani
AGN unification scheme attempts to unite different classes of AGN based on the idea that intrinsically similar objects appear different when viewed at different angles with respect to the line of sight. In AGNs with powerful radio emission known as radio-loud (RL) AGN, the unification scheme claims that radio galaxies are parent populations of RL quasars (RLQ) and BL Lac objects. AGN unification scheme has gained considerable success, however, there are still unsolved issues. We address these issues by studying a sample of RLQ and FR II radio galaxies using 1.4 and 5 GHz observations at matched resolution with the Very Large Array (VLA). We find that radio-loud unification largely holds but environmental factors also play an important role and cannot be ignored.
Characterizing exoplanets with JWST/NIRSpec – a NIRSpec GTO program overview
Valenti, Jeff
The Near Infrared Spectrograph (NIRSpec) is one of the science instruments on the James Webb Space Telescope that is scheduled for launch in 2019. NIRSpec offers four distinct observing modes to proposers 1) multi object spectroscopy (MOS) of 10s to 100s of sources in a ~9 arcmin field of view (FOV), 2) integral field spectroscopy (IFS) with a 3” x 3” FOV, 3) high contrast slit spectroscopy of individual objects and 4) time series observations of bright sources, e.g. transiting exoplanets host stars. The instrument offers seven dispersers are available in all observing modes: a prism covering the wavelength range from 0.6 to 5.3 micron with a spectral resolution R of ~30 to 300, and two sets of three gratings covering 0.7 to 5.2 micron with medium (R~1000) and high (R~2700) spectral resolution. The NIRSpec guaranteed time observer (GTO) team will use ~56 hours of NIRSpec guaranteed time to carry out spectroscopic time series observations of transiting exoplanets as well as integral field spectroscopy of directly imaged exoplanets with NIRSpec.We will present the science goals and targets for the exoplanet GTO program and discuss the implementation of the observations.
Chemistry, masses and ages of RAVE-K2 metal poor stars
Valentini, Marica
Metal poor stars are key to understanding the history of our Galaxy. In their element abundances pattern is encoded the chemical composition of the first stars and therefore, when the stellar age is available, hints on the chemical enrichment and evolution of the Milky Way. However, obtaing precise ages for field metal poor stars is a challenging task: at present only an handful of very metal-poor stars have ages, derived by using nucleo-cosmo-chronology (via Thorium and Uranium abundances).Asteroseismology in recent years demonstrated to be a powerful tool to derive masses, and hence ages, of red giant stars. By applying this technique to metal poor stars we hope to increase the number of metal poor objects with an age measurement.For this purpose we selected 5 giants ([Fe/H]<-1.5 dex) from RAVE survey flagged as metal poor candidates by Matijevic et al. 2017. We obtained seismic information from the light curves collected by the K2 space mission, and detailed chemical abundances, from ESO-UVES high resolution spectra. We derived iteratively the atmospheric parameters, by taking into account the seismic surface gravity. We then derived precise abundances taking into account NLTE effects. The final atmospheric parameters and abundances, together with the seismic information and, when available, Gaia parallaxes, were used for infer stellar masses, radii and ages, via Bayesian fitting on a set of isochrones.We obtained a unique set of metal poor stars, for which we determined precise ages. For the first time a consistent and complete approach have been adopted, in order to quantify the impact of temperature shifts, different mass-loss approaches, alpha-enrichment and corrections on seismic scaling relations. This exploratory sample, obtained from the first K2 Campaigns, shows how it is possible to obtain ages for field metal poor giants, and therefore add a chronology to the chemical enrichment of the Galactic halo.
New determination of primordial helium using HII region NGC346 of the small Magellanic cloud
Valerdi, Mabel
To place meaningful constraints on big bang nucleosynthesis models, an important determination is the primordial helium abundance. Low-metallicity HII regions have allowed to estimate the primordial helium abundance (Y_P), whose statistical uncertainties are very small. We present long slit spectra of the HII region NGC346 of the small Magellanic cloud. Spectra were obtained using three 409''X0.51'' slits divided into 96 windows. They cover the lambda3600-lambda7400A range, with a resolution of Delta_lambda/lambda=1/1500. We used pyNeb, and standard procedure to determine the physical conditions and chemical composition. NGC346 chemical composition is characterized by X=0.7400, Y=0.2560, and Z=0.0040. Due to its low metallicity, NGC346 requires a relatively small correction of Y_NGC346-Y_P. It also has the advantage that typical uncertainties are minimized (such as underlying absorption or collisional excitation of the B line which occurs in HII regions with T>15000K). These properties, together to its proximity and to the fact that is relatively bright, allow us to determine a He abundance with small systematic errors, compared to previous values reported in the literature.
Characteristics of sunspots from solar cycle 23
Valio, Adriana
Sunspots are the signatures of surface magnetic field on the Sun. This work analyses the physical characteristics of sunspots during cycle 23, detected using computer vision techniques. Images in visible light and magnetograms of the MDI instrument (Michelson Doppler Imager) of the space telescope SOHO (Solar and Heliospheric Observatory) were used for the detection of sunspots and the extraction of their characteristics. The number of spots, number of sunspot groups, area, temperature, brightness and the average magnetic field of sunspots were also studied. Based on the sunspot data, the behavior of these characteristics and relationships between them were verified along the periods of solar minimum and maximum. We detected and analyzed 32,317 sunspots, with longitude between -40 and 40 degrees, throughout the entire solar cycle. Nonlinear correlations were found regarding area and extreme magnetic field, as well as regarding temperature and area, and finally regarding temperature and magnetic field. It was also found that these correlations presented small variations over the time of the solar cycle 23, and that larger, colder sunspots and with stronger magnetic fields occur more frequently during periods of maximum activity.
Determining the effect of a non-uniform AGB outflow on its chemistry
Van de Sande, Marie
The chemistry within the outflow of an AGB star is determined by its elemental C/O abundance ratio. Due to the strong molecular bond of CO, no C-rich species are expected in the inner wind of O-rich stars, as all the carbon is expected to be locked up in CO. Similarly for C-rich stars, where no O-rich species are expected in the inner wind. Inner wind chemical models that take into account the effect of shocks, induced by the pulsating AGB star, can account for the presence of most unexpected species, but not all._x005F An alternative mechanism to the formation of the unexpected species is the penetration of harsh interstellar UV photons in a non-uniform outflow. Thanks to the advent of high angular resolution observations, it is clear that most outflows do not have a smooth density distribution, but are distinctly inhomogeneous or "clumpy". In such clumpy outflows, UV photons are able to reach the otherwise shielded inner wind region through the porous channels between the clumps. This leads to the photodissociation of CO, releasing the deficient element and allowing for the formation of the unexpected species in the inner wind._x005F We have included a clumpy density distribution in our chemical kinetic model by using a porosity formalism. The formalism provides us with a mathematical framework in which the increased leakage of UV photons is accounted for by modifying the optical depth of the outflow. Moreover, it also allows us to include the effects of the relative overdensity of the clumps. Both the leakage of UV photons and the overdensity of the clumps play an important role in the chemistry throughout the AGB wind. We explore the parameter space characterising the specific clumpiness of the outflow and describe its effect on the chemistry. We find that our results can explain the existence of certain species in the inner wind and add to the results of the non-thermodynamic equilibrium inner wind chemical models.
SAMI Galaxy Survey Data Release 2: Absorption-line Physics
van de Sande, Jesse
We present the second data release from the Sydney-AAO Multi-bundle Integral field Spectrograph (SAMI) Galaxy Survey at the Anglo-Australian Telescope. The data release will contain reduced spectral cubes for 1559 galaxies at 0.02 < z < 0.10. This release will also include stellar kinematic and stellar population value-added products derived from absorption line measurements, and all emission line value-added products from Data Release One. Our poster will highlight several galaxies from the SAMI Galaxy Survey that have interesting stellar and gas kinematics. For more information about data release 2, please see: https://protect-au.mimecast.com/s/anaNC3Q8Z2FVYo1LSgubFF?domain=sami-survey.org
Spectroscopic variability of proto-planetary nebulae
Van de Steene, Griet
We are carrying out a long-term radial velocity study of seven bright proto-planetary nebulae (PPNe) that possess bipolar or ellipsoidal nebulae and have been classified as “shell” sources, due to the infrared excess caused by their circumstellar shell. These objects are distinct from “disc” post-AGB sources studied by Van Winckel an collaborators. The most popular explanation of the shaping mechanism of bipolar nebulae attributes it to the interaction of a binary companion. However, none of the seven show clear evidence of variability due to binarity ! This puts severe constraints on possible undetected companions. All PPNe are found to vary in velocity, but these are dominated by semi-regular pulsations.We present our latest findings in the ongoing analysis of the line and radial velocity variablity in these objects.
An Unbiased High-Contrast Near-Infrared Imaging Survey of Nearby Herbig Ae/Be Stars: Are All Group I Disks Transitional?
van den Ancker, Mario
The process of clearing the disks surrounding pre-main sequence stars is still not well understood. Several competing theories have been proposed, by which either the disk is cleared through photo-evaporation, or due to clearing due to dynamical interactions with newly formed planets. The group of intermediate-mass young stars known as Herbig Ae/Be stars (HAeBes) have been classified in two groups, depending on the strength of the far-infrared excess in their spectral energy distribution. (Maaskant et al. 2013, 2014) have proposed that the group I sources, which have a larger far-infrared excess, may all have gaps, which could indicate the presence of newly formed planets in their disks.This proposal predicts a larger extent of the disk in scattered light in group I sources compared to group II HAeBes. We have used SPHERE, the high-contrast adaptive optics system at the VLT, to test this hypothesis by observing a sample of 24 nearby HAeBes. Using a novel method to reduce speckle noise, we have spatially resolved six disks in this sample, allowing us to test the Maaskant et al. hypothesis. In addition we have detected four new companion candidates.
Under what conditions does the Sun produce inverse FIP plasma composition?
van Driel-Gesztelyi, Lidia
Title: Under what conditions does the Sun produce inverse FIP plasma composition?Authors: L. van Driel-Gesztelyi, D. Baker, D.H. Brooks, G. Valori, D.M. Long In the solar corona low first ionization potential (FIP; < 10 eV) elements are enhanced by a factor 2-4. However, since Doschek et al 2015, we now know that inverse FIP (IFIP), where low FIP elements are depleted or high FIP elements are enhanced, is also present in the solar atmosphere in the vicinity of large sunspots. To date, there are 8 active regions where IFIP has been observed at specific locations in flaring active regions during and outside of flare times. We analyze the magnetic evolution of the 8 known active regions containing IFIP patches. The IFIP patches can be classified into 2 categories. One category is transient IFIP patches which appear at footpoints of sigmoidal flare loops (see abstract of Baker et al). The other category is persistent IFIP patches which always appear in complex active regions where repeated flux emergence leads to collisions between emerging and pre-existing sunspots. The collision of sunspots and flux emergence from under existing sunspots (another characteristic of the IFIP-producing active regions) are highly suggestive of sub-photospheric reconnection taking place at the locations of IFIP patches. The Laming FIP/IFIP model (Laming, LRSP, 2015) can explain how the persistent IFIP patches are created.
Searching for young radio pulsars located in new SMC SNR candidates
van Jaarsveld, Johanna
The SMC went through relatively recent star formation episodes, producing a large number of O and B stars, many of which are companions in high mass X-ray binary systems. A recent census by Haberl & Strum (2016) identified 120 HMXBs in the SMC - similar to the population in the Milky Way, despite the fact that the SMC is only one-fiftieth the mass, we therefore know that the SMC harbours many neutron stars and many interesting binaries. However, despite this large population of neutron stars only five rotation powered pulsars have been discovered in the SMC through various Magellanic Cloud radio surveys. To improve on the sensitivities achieved in the previous surveys, we conducted the deepest, most sensitive observations with the 20 cm Parkes Multi-Beam receiver of 6 new SNR candidates located in the SMC, aiming to find new radio pulsars, some of which could be progenitors to HMXBs or members of double neutron star binaries. We will report on any newly discovered radio pulsars, and in the case of not detecting any radio emission, we will determine a reasonable luminosity limit by using the increase in sensitivity with respect to the previous surveys, which we can then compare with potential PWNe to constrain the neutron star properties.
IMFR11GHz : RADIO INTERFEROMETER MICHELSON TYPE AT 11 GHz FOR EDUCATION.
Vanegas, Santiago
Development, commissioning and operation of radio astronomical instruments and their software tools to increase the local technical and scientific knowledge in Colombia represent a big effort at the Observatorio Astronomico Nacional. With these projects is possible to make investigations and labs for students, who can learn astronomy via observational sessions under cloudy skies. As part of a master degree in Astronomy at the Observatorio Astronomico Nacional, the development of a Michelson Doppler Radio Interferometer at 11GHz based on Jin Koda at Stony Brook University1 was proposed.The interferometer was build on a guide rail, where all the reflecting surfaces are located. Two of those flat mirrors are located at the end of a guide rail, at a certain separation (baseline). Each mirror reflect the radio waves to another mirror at the closer to the middle of the guide rail, which in turn reflect the waves onto a broadcast satellite parabolic dish located at the geometric middle of the guide rail. Signals arriving from both sides of the guide rail are then reflected and added by the dish and finally detected by the detector located at the focal point of the dish. Moving the external mirrors we can change the baseline and the interference pattern and the spatial resolution to obtain measurements of the solar diameter.The whole system was built with a motorized pier for azimuthal rotation and a electric actuator to move in elevation. This configuration make possible to find and locate with easy the Sun or any other radio source and sweep the interferometer beam across extended sources to obtain the interference pattern at several baselines.The IMFR11GHz is a high impact instrument that brings radioastronomy, interferometric principles concepts to the whole secondary, undergraduate and graduate community in Colombia. All of hardware and software tools are Open Source and low cost, making it easy to replicate by other universities..Website: https://goo.gl/5MPPtf
Sunspot Observations Made by Hallaschka during the Dalton Minimum
Vaquero, José Manuel
We present the sunspot observations made by F. Hallaschka in Czech Republic during the years 1814 and 1816. These observations have a special interest because were performed during the so-called Dalton minimum and some of those records can complete observational gaps in the sunspot observation databases. We compare the sunspot records made by Hallaschka with other ones carried out by contemporary astronomers concluding that they are very similar. On the other hand, unfortunately, an analysis of the sunspot areas and positions registered by Hallaschka showed that they are too inaccurate for scientific use. The observations by Hallaschka confirm a low level of the solar activity during the Dalton minimum.
FR-type radio sources in COSMOS: relation to large-scale environment
Vardoulaki, Eleni
The radio sources associated with active galactic nuclei (AGN) can exhibit a variety of radio structures, from simple to more complex, giving rise to a variety of classification schemes. Here we present an analysis on the radio structure of radio AGN from the VLA-COSMOS 3-GHz Large Project in relation to the environment their hosts lie within. We classify these as FRI (jet-like) and FRII (lobe-like) radio AGN based on the FR-type classification scheme, and compare them to a sample of jet-less radio AGN at 3-GHz VLA-COSMOS. The purpose of this project is to explore the differences in the radio structure between FRIs and FRIIs and relate them to the large-scale environment. As environmental probes we take the X-ray groups (hundreds kpc) and the density fields (~Mpc-scale) in COSMOS. We find that the large-scale environment does not explain the observed dichotomy in jet- and lobe-like FR-type objects as both types are found on similar environments, but it does affect the shape of the radio structure introducing bents for objects closer to the centre of an X-ray group.
Konkoly optical catalog of young stars
Varga-Verebelyi, Erika
We present a new and so far most complete catalog of optically selected young stars and give a statistical overview of the Galactic star forming regions within our 2-kpc environment.The basis of this work is an extensive literature search for young stars in all the known star forming regions included in both volumes of the Handbook of Star Forming Regions.We collected data on known young (< 10 Myr) stars detected in optical bands.The catalog contains information (such as sky coordinates, name of the stars, name of the enclosing star forming regions, the identification methods, references and binarity) about 12 600 YSOs and it is already in use by the Gaia Photometric Science Alerts Team to help identify variable YSOs. The catalog was cross-correlated with Gaia DR2 and obtained flux and distance estimations for 86% of the stars.
Looking at the stars as an instrument for peace and reconciliation
Vargas Dominguez, Santiago
After more than 50 years living under an internal conflict, Colombia has left war behind with the disarmament and demobilization of FARC ex-combatants, and is currently facing their reintegration to the civil society.The Universidad Nacional de Colombia, the largest university in the country, has been and important actor, leading from the academia the peace process. Since 2016 a group of professors and students started a project called “Knowledge spaces for peace”, going to several regions historically affected by the conflict to create spaces for dialogue between former communities in discord.This work shows the experience at the Jaime Pardo Leal Transitional Standardization Zone (currently called Territorial Training and Reincorporation Spaces) located in Colinas, Guaviare, one of the concentration camps of ex-combatants of the FARC.One of the objectives sought is to promote the interest of these communities for the environment that surrounds them and to strengthen their links with knowledge, particularly with disciplines such as mathematics, physics and biology, through astronomy. We highlight the importance of a society based on knowledge to procure a long-term reincorporation of ex-combatants fostering a complete peace reestablishment.
Solar photospheric plasma velocity associated to magnetic field dynamics in a solar active region
Vargas Dominguez, Santiago
The solar photosophere displays convective flows at different spatial and temporal scales (granulation, mesogranulation, and supergranulation)This work analyzes the evolution of a solar active region centered on the distribution of velocities prior to the fully emergence of the associated sunspot by means of time series of filtegrams. In addition, magnetic field data from LOS magnetograms is obtained in order to study the dynamics of magnetic flows. These data were obtained from the Solar Dynamics Observatory (SDO).The distribution of plasma velocities reveals a strong correlation between the plasma motions and the dynamics of magnetic elements during the evolution of the active region, that is mantained until intense magnetif flux elements start to emerge in the field of view under study.
Exoplanets detection using empirical mode decomposition
Vasconez, Christian
The ultimate goal of exoplanets exploration is to discover potential habitable planets and even finding evidence of life beyond [Mayor & Queloz, 1995; Gillon et al., 2017; Alberti et al., 2017]. In fact, together with the technology, astrometry continuously reaches new levels of accuracy and precision, getting us closer to these goals. Now, it becomes crucial to improve and search new methods for astrophysical-information extraction from astrometric data. Here, an adaptive and a posteriori decomposition method, in which the basis functions are directly derived from the non-stationary data, is applied. This method, the empirical mode decomposition (EMD) [Huang et al., 1998] is used to study the public photometric data from the Kepler space mission. We focus on the system Kepler-41, where we identified two clear timescale contributions, respect to less-energetic modes. The first of these modes is positively attributed to Kepler-41b [Santerne et al., 2011]. Meanwhile, the second mode of the system let us to propose the existence of a non-identified exoplanet, transiting its solar-type star with an orbital period of 4.71375 days, and a semimajor axis of 0.05654 AU.
Galactic ambient of host galaxies of GRBs
Vásquez, Nicolás
The study of GRBs host galaxies and its vicinity could provide constrains on the progenitor and an opportunity to use these violent explosions to characterize the nature of the high redshift universe. Studies of host galaxies of Gamma Ray Burst reveal a population of starforming galaxies with great diversity, spanning a wide range of masses, star formation rate, and redshifts. In order to study the galactic ambient of GRBs we used the S. Savaglio catalog from 2015 where 245 GRBs are listed with RA-Dec position and z. We choose 50 GRBs Hosts galaxies from Savaglio catalog and SDSS DR12, and galaxies in a local vicinity of 10 h -1 Mpc radius to determine some photometric and population characteristics. We calculate the volumetric density population of galaxies around the GRB Hosts, within a volume of an sphere whit radius of 10 h -1 Mpc and find a low density compared with a typical group of galaxies. In order to know the galaxies stellar formation state, in regions where GRBs are formed, we made an analysis of color index using SDSS data of µ [? 3543], r[? 6231] and calculate the indexes µ-r. We find a value µ-r=2.63, it means that the galactic ambient of GRBs Host regions are statistically redder than void and wall regions on a indirect way (Voids:µ-r=2.043; Walls:µ-r=2.162). Futhermore, we used a inverse concentration index analysis, ICI=R 50 /R 90 and find that galaxies in GRBs Hosts vicinity are also of slightly early type than void and wall galaxies.
Development, calibration and implementation of an autonomous Water Cherenkov Detector using REDPITAYA in Quito
Vásquez, Nicolás
At Escuela Politécnica Nacional, we have developed an autonomous station capable of detecting the rate of Cosmic Rays arriving near the zero latitude at 2848 m.a.s.l. Furthermore, we also measure the temperature, the pressure and the relative humidity at the station. The fluxes of secondary particles have been simulated with CORSIKA for the detector location; we determine the muon fluxes for an hadronic shower and for an electromagnetic shower for primary particles with energies from 1 Tev to 10 TeV. The detector aims to perform a continuous monitoring of the solar activity and it is part of the Ecuadorian Network of Astroparticle physics, cosmic rays and space weather.The autonomous station is composed by a Water Cherenkov detector, a PhotoMultiplier Tube (PMT) and a system of data acquisition. The PMT is an EMI XP1805, which is the sensor element for detecting the Cherenkov radiation produced by relativistic charged particles when they travel through a dielectric medium. The data of the conditioned signals from the photomultiplier tube and from the environmental sensors is acquired and processed using a RedPitaya board that counts with two Fast Analogue Digital Converters for digitalizing the signals at 125 MHz and offers the possibility of having integrated the capabilities of an FPGA interfaced with a GNU based operative system; additionally, the synchronization of the collected information is done by taking advantage of the precision of a GPS. In order to generate power to operate the station, a solar panel is used, and it has been designed to work for up to two days without the need of insolation. The development of this project has made it possible to implement a low cost monitoring station that provides useful information for the analysis of the behavior of the space weather as seen from the middle of the world.
Project: Center of archeology and astronomy in Coaque
Vásquez, Nicolás
The astronomical history of Ecuador has been misinterpreted during decades, it is believed that astronomy starts on the XVIII century. Ecuador is one of the countries where the equatorial line crosses. Before the Incas, cultures as Valdicia (3000 B.C) , Jama Coaque (500 B.C) show understanding of astronomical phenomena on the archaeological register. The interpretation of iconography suggest recursive images related to the sun, the moon and the stars and the evidence of a developed agriculture suggest the understanding of the solar time. In the coast of Ecuador in the province of Manabí, there is a iconic place where astronomy has converge during the whole story of the country. Beginning with prehispanic cultures as Valdivia and Jama Coaque the history of astronomy began. In 1736 the French Geodesic Mission arrive to Punta Palmar, in Manabí Ecuador and determine the first 0 Latitude point for his work. And finally, studies of astroparticle astrophysics are propose since the 0 Latitud offers the highest magnetic rigidity for particles coming from the cosmos. Nevertheless the region of Manabí is one of the poor regions of the country. After the earthquake in 2016, Manabí is the region with problems on education, gender, inequality, natality and lack of services. In association with Escuela Superior Politécnica de Manabí (ESPAM), Universidad San Francisco de Quito (USFQ) and Escuela Politécnica Nacional (EPN) and the community of COAQUE we propose to build an interactive museum combining the arqueological resources of the site combining with geodesic history of the region.
Lidov-Kozai mechanism in asteroid families
Vavilov, Dmitrii
We have studied the secular perturbations induced by the Lidov-Kozai mechanism in the main asteroid belt. This mechanism induces coupled long-period oscillations of the inclination, i, and eccentricity, e. The oscillations depend on the argument of perihelion and become substantial in the case of high inclinations and large eccentricities. In this work we have calculated the amplitudes of i and e-oscillations for several asteroid families by the empirical method. This method uses distributions of orbital elements to obtain secular perturbations. After excluding classical secular perturbations, the Lidov-Kozai oscillations of the elements became visible in the distributions of orbital elements of the family members. This allows us to derive the amplitudes of the element oscillations. We also obtained the amplitudes by numerical integration. Jupiter on a circular orbit was taken as a perturbing body. For each value of initial eccentricities and inclinations (argument of perihelion equals p/2) we have obtained the amplitudes of sini and eccentricity (Asini, Ae) as well as the net amplitude A = (Asini2 + Ae2)1/2. As a result, the two-dimensional surface A(e,sini) was constructed, and two main lines were identified on this surface: the bound between circulation and libration regions and the line of the stationary solution, where amplitudes equal zero. The results for considered asteroid families are in good agreement with the amplitudes obtained by the empirical method.
Is the extremely elongated shape of Oumuamua (1I/2017 U1) a result of dust bombardment?
Vavilov, Dmitrii
The first discovered interstellar asteroid Oumuamua, observed on 19 October 2017 by Pan-STARRS, paid huge attention of scientific community and media not only because of its reliable hyperbolic orbit but by its extremely elongated shape as well. The asteroid looks like an ellipsoid of revolution with the semi-major axis a = 230 m and semi-minor axis b = 35 m. In this work we propose the mechanism for creating such an object from a slightly elongated asteroid. We assume that Oumuamua came to the Solar system from a big interstellar dust cloud and the collisions with the dust particles increased the a/b ratio. Our simulations claim that 1I could be 330*135m initially and got its current shape by passing 20 parsecs at the speed of 20 km/s through the dust cloud with 10-27 g/cm^3 dust density. From this follows that the interstellar bodies, initially smaller than Oumuamua, would possibly not survive passing through a dust cloud and therefore we will not find so highly elongated small interstellar asteroids.
Multi-wavelength properties of the isolated AGNs in the Local Universe
Vavilova, Iryna
We present a complete analysis of multi-wavelength properties of 61 isolated AGNs, which are limited to Ks = 12.0m and Vr < 15 000 km/s. We used all the available databases obtained with ground-based and space observatories. We show that the observed nuclear activity of these AGNs is connected with the internal galaxy parameters (relative mass/size, dark/visible matter content, multi-wavelength properties of gas-dust medium in accretion disks, tor's structure, central black hole mass etc.). These objects were poorly investigated, especially in X-rays, and our study has allowed 1) to separate the internal evolution mechanisms from the environment influence and consider them as two separate processes related to fueling nuclear activity, 2) to explore absorption features and the X-ray continuum radiation from accretion disks around SMBHs. In the case of detecting the Fe K emission line, it was possible to analyze the physical conditions in the AGNs innermost parts in more details. Using the spectral Hß-line data we were able to estimate the SMBH masses of several isolated AGNs and to show their systematical lower values than the SMBH masses of AGNs located in a dense environment. To evaluate X-ray properties, we processed the spectral data obtained by XMM-Newton, Swift, Chandra, INTEGRAL, and NuStar. We determined spectral models and values of their parameters (spectral index, intrinsic absorption etc.) using a cumulative soft and reconstructed hard energy spectrum. The spectral parameters for most of these 61 isolated AGNs were obtained for the first time. We found a significant excess content of Sy 2 type galaxies in comparison with Sy 1 type galaxies (41% and 10%); isolated AGN hosts of all spectral types are located at the more far distances as well as they are mostly of late morphological types. It means a close encounter appears capable of activating an evolution sequence where a normal galaxy becomes first a starburst, then a Sy2 and finally a Sy1 galaxy.
The automated morphological classification of galaxies from the SDSS at z<1.0 by the machine learning technique
Vavilova, Iryna
We evaluated a new approach for the automated morphological classification of big samples of galaxies which is based on the combination of three methods: visual classification for training samples; diagrams «color indices – concentration index»; machine learning technique (Random forest). This approach was tested and applied for the SDSS samples of 317,018 galaxies at z<0.1 (Dobrycheva, Vavilova, Melnyk, Elyiv, 2017, arXiv:1712.08955). Namely, we used a well-known fact that galaxy morphological type is correlated with the color indices, luminosity, de Vaucouleurs radius, inverse concentration index etc. We plotted the diagrams of color indices g-i and one of these parameters and discovered that these parameters may be used for galaxy classification into three classes: E -- elliptical and lenticular, S -- types Sa-Scd, and L -- types Sd-Sdm and irregulars. The accuracy is 98% for E, 88% for S, and 57% for L types. The combinations of "color indices g-i and inverse concentration index R50/R90' and "color indices g-i and absolute magnitude M_r" gave the best result: 143263 E type, 112 578 S type, 61177 L type (Dobrycheva, Melnyk, Vavilova, Elyiv, 2015, Astrophysics). After this, we undergone a training sample of 5,000 galaxies classified visually into early E (E, S0, S0a) and late L (Sa to Irr) types using a machine learning technique. To define an accuracy of classifiers we applied the 5-folds validation and found that Random Forest provides the highest accuracy. Applying it to the SDSS DR9 sample of 60,561 galaxies at z<0.1 we obtained that 47% E and 53% L types are among these galaxies.To be sure in this approach, we prepared a sample of about 1,800,000 galaxies at z<1.0 and provided the automated morphological classification. The effectiveness of this approach for galaxies at different cosmological scales, details of creation of this sample and accuracy of applied methods, as well as the obtained results will be discussed in this report.
The oldest astronomical observatories at the territory of the modern Ukraine
Vavilova, Iryna
The stone complex on the mountain Lysyna Kosmatska - we refer to the calendar sanctuary. It is located on the southern slope of the mountain and covers an area of about 400 m2. The sanctuary is an elongated (10 × 40 m) east-west slope of gigantic stone slabs. The top plates of enormous size form a 6 m long tunnel in the direction of the north-east - south-west. The astronomical character of the sanctuary on Lysyna Kosmatska is confirmed by the observations of the participants of the ethnological and archaeological expedition "Carpathians - Dniester" by Prof. Kohutyaka on June 21-22, 2007. The scheme of astronomical observations on Lysyna Kostakska coincided with the Stonehenge plan, On the Lysyna Kosmatska the correspondence to Stonehenge alley is a stone tunnel. Sunset on a day of summer sunshine in Stonehenge fixed a stone, on Lysyna Kosmacki this function was provided by a sacrificial pit.Among the most interesting astronomical places of the Eneolithic era in the Crimea, pointing to the existence of ancient observatories, - the Crimean Skye menhir near the city of Bakhchysaray (mepale rocky ceilings, II millennium BC). Although the place is not as great as the Stonehenge. In the beginning of 2000 the BakhchisarayMenhir (44 ° 46 '06.5 "N, 33 ° 54' 57.2" E) was studied by A. Lagutin. He discovered that if you approach the menhir and look east, you can see the hole (window) in the rock on the opposite side of the beam (at a distance of approximately 300 m), through a kind of but the sky. Menhir and the window were served as two diopters of a huge optical instrument that fixed Seduced east-west visor axis, on which only on certain days (near spring and autumn Equinox) could be observed. To confirm this hypothesis, it took several years (through early fog and clouds), but the success was exciting: through this window in the rock rays the descending Sun fell into the eye observer near Menhir
Lightcurve Photometry of 2525 O’Steen with the new "Milankovic" robotic 1.4 m telescope at AS Vidojevica
Vchova Bebekovska, Elena
The Astronomical Station (AS) Vidojevica is an observation site established by the Astronomical Observatory of Belgrade. It is located on the top of the mountain Vidojevica at 1150m altitude. The observations have been started since 2010 with the 60 cm Cassegrain telescope "Nedeljkovic". In April 2016 a new ASA AZ1400 "Milankovic" Ritchey–Chrétien 1.4m telescope was mounted in a roll roof pavilion. It is planned that the automated dome will be constructed before the end of 2018 and that “Milankovic” will become a part of the Worldwide Network of Robotic Telescopes.On 28 March 2017, the asteroid 2525 O’Steen, a member of the Themistian asteroid family, was observed by the "Milankovic" telescope. It is believed that members of this Hirayama family have a composition similar to that of carbonaceous chondrites. Recently Ferrín [1] showed that O’Steen and some other Themis members might have a low-level cometary activity. Our aim is to use the lightcurve of 2525 O’Steen obtained at the AS Vidojevica with the combination of lightcurves obtained in other observatories [2] during previous apparitions at various geometric conditions of the asteroid, for the calculation of the spin vector, rotational properties and estimation of its preliminary shape model. Increasing the number of asteroids with known physical characteristics is important for studies of collisional families and for the understanding of the evolution of our planetary system.References:[1] Ferrín, I., Pérez, M.; Rendón, J., Planetary and Space Science, Volume 137, p. 52-63, 2017[2] Apostolovska, G.; Ivanova, V.; Borisov, G. Minor Planet Bul. 31, 44-45, 2004
Exoplanetary Science and Instrumental Developments at LBTO
Veillet, Christian
With its pair of 8.4m mirrors on a single mount, the Large Binocular Telescope (LBT) offers the gathering power of an 11.8m telescope and the angular resolution of a 22.8m telescope. With its pair of deformable secondary mirrors, it offers excellent adaptive optics (AO) performance, as demonstrated by the imaging of extrasolar planets in the early days of its AO operations.Since then, various programs in Exoplanetary Science were launched, including the NASA HOSTS mission using the LBT Interferometer (LBTI). We will describe the main scientific objectives of the currently ongoing programs, which also include high spectral resolution transit observations.We will close the presentation with an overview of the new instruments in development, such as visible and near-IR extreme-AO imagers and a near-IR AO-fed high-resolution and high-stability spectrograph, or in their infancy (interferometry in the visible). They all have exoplanets are targets of choice! Extrasolar Science will contribute to establish LBT as a forerunner of the ELTs, which are still a decade or more away from their full operation.
3D kinematics of the Galactic thin disc stars from the Gaia DR2 and PMA data.
Velichko, Anna
Joint usage of proper motions and radial velocities provided by the Gaia mission allows to get a full view about stellar kinematics in the solar neighborhood.Using kinematic criterium thin disk stars were selected from the ~7.2 mln Gaia DR2 subsample containing radial velocities, resulting in ~5 mln (~70%) stellar subset. For these stars of mixed spectral composition kinematic parameters of the Ogorodnikov-Milne model (OMM) from the Gaia DR2 and PMA data depending on distance to the stellar sample from 100 to 1000 pc were derived. We carried out two solutions of the OMM equations by the least square method: joint (proroper motions plus radial velocities) and separate (using proprer motions only).As a result, we can make several conclusions. First, 3D and 2D calculations give us very close values of the kinematic parameters. Second, using relation between value of V component of the solar peculiar velocity relative to the centroid chosen and mean age of stars included to the corresponding stellar sample (Dehnen & Binney(1998), Gontcharov (2012)), we decided that the latter for our stellar subsample of thin disk stars is about 4.0 Gyrs. Third, value of the rotational velocity of the Galaxy at the solar distance (8.0 pc, Vallee (2017)) Vrot derived from the PMA data is systematically lower than one derived from the Gaia DR2 data by about 15 km/s.We trace the OMM parameters depending on distance to the stellar sample. Note that the ?3 and M12+ do not have any notisable trends depending on distance. ?2 and ?1 are meaningful only for the nearest stars up to 300 and 500 ps respectively, then they become equal to zero within 3s. M23+,M22+,M13+ also gradually decreases to zero while M11+, on the contrary, increases with distance. M33+ is not meaningful almost in all cases.
Circumstellar chemistry of Si-C bearing molecules in the C-rich AGB star IRC+10216
Velilla-Prieto, Luis
A significant contribution to ISM dust enrichment is produced by AGB stars, where nucleation of grain seeds occurs near the photosphere. Dust formation and growth is far from being well understood because there are many unknowns in the formation pathways; the condensation sequences of refractory species; and the dependence on stellar and circumstellar properties.Silicon carbide together with amorphous carbon are the main components of dust grains in the atmospheres of C-rich AGB stars. Therefore, the study of gas phase carriers of Si-C bonds in the envelopes of C-rich stars is a promising approach for shedding light on the formation of SiC dust. Small gaseous Si-C bearing molecules (such as SiC, Si2C, and SiC2) are efficiently formed close to the stellar photosphere. They likely condense onto dust seeds owing to their highly refractory nature at the lower temperatures (i.e., below about 2500 K) in the dust growth zone which extends a few stellar radii from the photosphere. Beyond this region, the abundances of Si-C bearing molecules are expected to decrease until they are eventually reformed in the outer shells of the circumstellar envelope, owing to the interaction between the gas and the interstellar UV radiation field.Our goal is to understand the time-dependent chemical evolution of Si-C bond carriers probed by molecular spectral line emission in the circumstellar envelope of IRC+10216 at millimeter wavelengths. Here, we will present our latest results derived from the analysis of single-dish (IRAM-30m) and interferometric data (SMA, NOEMA, and ALMA) of Si-C bearing molecules in the circumstellar envelope of this prototypical AGB star.
Understanding the evolution of dwarf galaxies in the Fornax cluster using the Fornax Deep Survey data
Venhola, Aku
A variety of environmental and internal processes affect the evolution of dwarf galaxies. To understand the importance of these processes, we need to statistically analyze compete galaxy samples with homogeneous data and measurements. The Fornax Deep Survey (FDS) is a new survey providing ultradeep u'g'r'i'-data covering 26 deg2 area in the Fornax cluster and the Fornax A group. The data allows high resolution analysis of dwarf galaxies down to absolute r-band magnitude Mr ~ -10 mag. Using the FDS-data, we have generated the most extensive magnitude and size limited catalog of dwarf galaxies in the Fornax cluster including more than 600 cluster dwarfs. We fit the light distributions of these dwarf galaxies with Sersic-profiles using GALFIT to obtain their structural parameters, and measure aperture colors. We also classify the dwarf galaxies into late- and early-types according to their morphology and study them separately. We then analyze the projected distribution, luminosity function, structure and colors of the dwarf galaxies in the cluster, and study how these properties change in different cluster-centric bins. Finally, we discuss how our results can be interpreted with the current understanding of environmental processes taking place in galaxy clusters.?
Optical/IR follow-up of Near-Earth Asteroids from Mount Abu Infra-red Observatory
Venkataramani, Kumar
Near-Earth asteroid flybys of Earth gives a good opportunity to examine the asteroids with larger precision. Smaller ground based telescopes which might not detect these asteroids at larger distances, will do so effectively during their Earth flybys. A larger effective phase angle can also be covered in a short period of time during the course of the flyby.We have covered three near-Earth asteroids spectroscopically using the 1.2m and 0.5m telescopes at the Mount Abu Infra-red observatory. The optical low resolution spectrograph LISA and the Near-Infrared Camera Spectrometer(NICS) have been used to obtain the asteroid spectra in the optical and near infra-red wavelengths respectively. The optical spectra of the asteroids 2015 TB145 and 2014 JO25 were obtained during their close flybys of Earth in October 2015 and April 2017 respectively. The asteroid 2015 TB145 showed a minor absorption feature near 4300 angstroms. Although the spectrum of the asteroid 2014 JO25 was featureless, it exhibited a rarely seen phenomena of phase-bluing. The near infra-red spectra of the asteroid 1983 TB (3200 Phaethon) was obtained in December 2017, when the asteroid was relatively closer to Earth. Apart from the spectroscopic follow-ups, optical photometry of the asteroid 2012 TC4 was also carried out in October 2017 and the visual light curve was obtained.These results are important as these near Earth asteroids come from different asteroid families and also from various regions (different inclination angles and semi-major axis) in the solar system. The results also depict the important role played by small telescopes in following up the near Earth Asteroid flybys.
Astronomy outreach for supporting the underserved and dispossessed
Venugopal, Ramasamy
Astronomy and Space topics hold a universal fascination. Astronomy is deeply rooted in various cultures around the world. Thus astronomy outreach can (and has) been a bridge to indigenous communities and underserved populations. Astronomy outreach has also been deployed in war ravaged regions to instill a sense of oneness that emerges from the astronomical perspective. Exposure to astronomy topics serve to inspire people and leads to an uptake in science and STEM subjects. So, astronomy outreach campaigns to remote regions are also effective tools of education.The IAU Office of Astronomy for Development (OAD) has supported various outreach projects that used astronomy to support the underserved and dispossessed. Examples include using astronomy to bring solace to students in earthquake affected regions, to bring together children from different sides of a conflict region, to educate remote, underserved communities, tactile astronomy to teach visually impaired children and astronomy for economic empowerment of remote communities (astro tourism). The OAD Regional Offices provide a readymade structure to deploy such efforts around the world according to local conditions. I will be sharing some of the experiences of coordinating these projects on behalf of the OAD.
IAU Office of Astronomy for Development
Venugopal, Ramasamy
The Office of Astronomy for Development (OAD) aims to use astronomy, including its tools, practitioners and their skills, to benefit society. The OAD, a joint project of the International Astronomical Union and the South African National Researach Foundation, has the vision of using 'Astronomy for a better world'. The OAD coordinates and funds projects that use astronomy to tackle the sustainable development goals (SDG) defined by the United Nations. Having funded more than 120 projects over six years, the OAD is in a position to look back and learn from these projects, their challenges, shortcomings and successes. It also provides the opportunity to learn where and how projects have applied astronomy effectively to contribute to sustainable development as well as the gaps in project ideas. This presentation will focus on various ways past OAD projects have tackled a number of the SDGs and kickstart discussions on our future heading.
Astronomy for Development
Venugopal, Ramasamy
Our modern, technological world owes much to science research and investment. But in the recent past, science has alienated itself from the public and public support for science is dwindling in several countries. The relevance of pure science research is being increasingly questioned. Curiosity about the natural world is no longer an accepted justification for science investments. Recently, a handful of organizations from various disciplines (Physics for Development, Data for development, Astronomy for Development) have taken the lead on using and shaping scientific knowledge and expertise to contribute to the United Nations Sustainable Development Goals (SDG). Using science to directly impact on the world's biggest challenges could both bolster the public view of science and scientists as well as bring science closer to the people. Since 2011, the IAU Office of Astronomy for Development (OAD) has been funding and coordinating projects that use astronomy to benefit society. These projects contribute to the OAD vision of using 'Astronomy for a better world'. Astronomy for development, and broadly science for development, provide an approach for communicating the continued relevance of science with the emphasis on people and society. This poster conceptualizes the idea of Astronomy for development including a few practical examples of OAD funded projects that have used Astronomy to impact lives as well as the possible role and collaboration with other fields of science.The OAD is a joint partnership between the International Astronomical Union and the South African National Research Foundation.
The Too-Big-To-Fail problem in the field - Insights from realistic dwarf simulations
Verbeke, Robbert
We test whether advanced galaxy models and analysis techniques of simulations can alleviate the Too-Big-To-Fail problem(TBTF) for late-type galaxies(Papstergis et al. 2015), which states that isolated dwarf galaxy kinematics imply that dwarfs live in lower-mass halos than is expected in a ?CDM universe. Furthermore, we want to explain this apparent tension between theory and observations.Previously, we have used the MoRIA (Models of Realistic dwarfs In Action) suite of dwarf galaxy simulations (Verbeke et al. 2015) to investigate whether observational effects are involved in TBTF for late-type field dwarf galaxies. To this end, we created synthetic radio data cubes of the simulated MoRIA galaxies and analyse their HI kinematics as if they were real, observed galaxies.We found that for low-mass galaxies, the circular velocity profile inferred from the HI kinematics often under-estimates the true circular velocity profile, as derived directly from the enclosed mass. Fitting the HI kinematics of MoRIA dwarfs with a theoretical halo profile results in a systematic underestimation of the total mass of their host halos. We attribute this effect to the fact that the interstellar medium of a low-mass late-type dwarf is continuously stirred by supernova explosions into a vertically puffed-up, turbulent state to the extent that the rotation velocity of the gas is simply no longer a good tracer of the underlying gravitational force field. If this holds true for real dwarf galaxies as well, it implies that they inhabit more massive dark matter halos than would be inferred from their kinematics, solving TBTF for late-type field dwarf galaxies (Verbeke et al. 2017)In this talk, I will present results from a suite of new, even more realistic dwarf galaxy simulations and discuss the Too-Big-Too-Fail problem in the field and potentially other cosmological questions.
Preparing for the WEAVE Galaxy Clusters survey: XSL-based stellar population models
Verro, Kristiina
With the next generation wide-field spectroscopic facility WEAVE for the William Herschel Telescope, dwarf galaxies in different environments up to a redshift of 0.04 will be accessible. WEAVE’s Galaxy Clusters survey will provide single-fibre and IFU spectroscopic information for thousands of dwarfs, with resolving power R = 5000, and 366-959 nm wavelength coverage. We are developing a new interpolator and stellar population models based on X-Shooter spectral library (XSL) that will exceed the resolving power and wavelength coverage of WEAVE. The XSL covers the entire HR diagram, including M dwarfs and M giants that help us understand the old stellar populations of early-type dwarf galaxies. The new stellar populations models will allow us to study early-type dwarfs in clusters, answering questions about the influence of the environment on these systems.
Finding flares in Kepler data using machine learning tools
Vida, Krisztián
Long photometric surveys, like the Kepler database is a gold mine for studying flares. However, identifying them is a complex task: while in the case of single-target ground observations it can be easily done manually by visual inspection, this is nearly impossible for year-long time series for several thousand targets. Although there exist automated methods for this problem, several problems are difficult (or impossible) to overcome with traditional fitting and analysis approaches. In this poster we introduce a method for identifying flares based on machine learning methods, which are intrinsically adept in handling such data sets.
Stellar coronal mass ejections and their possible effects on habitability
Vida, Krisztián
Flares and coronal mass ejections (CMEs) are the most prominent, most energetic events of stellar activity. These events can have high importance in exoplanet studies they can erode or irreversibly alter the atmospheres of orbiting planets, rendering them uninhabitable. On the Sun, CMEs are studied in high detail, both by observation and modeling, and they are seen rather frequently: 0.5-6 CME/day. On other stars, however, there are only a handful of CMEs observed up to now. We present an extensive search of observational archives - the virtual observatory - in the hope of finding the missing events, and consider how these eruptions could influence the circumstellar planets and their habitability.
The Carbon Continuum Among Asteroids: UV Clues to Location of Origin in the Solar System?
Vilas, Faith
Carbonaceous species evolve from hydrocarbons and organics to amorphous and glassy carbons to graphites with increasing levels of thermal processing and irradiation. Due to this evolution, a carbon continuum is present throughout the solar system, with overall less-processed organics more present in the outer solar system and overall more-processed carbonized materials in the inner solar system. Spectral signatures of carbonaceous species mark the amount of processing experienced by a solar system object surface. Generally speaking, with exposure and processing (thermal, irradiation), carbons and organics begin to lose their hydrogen component, ultimately leading to carbonization and graphitization. In the outer solar system, complex organics exhibit diagnostic spectral features in the UV and infrared. With more maturity, organics are expected to evolve from aliphatic (linear molecular chains) to aromatic (molecular rings). On this continuum, diagnostic features should appear, especially in the UV (<300 nm). As processing of carbon species occurs and H is lost, a UV absorption feature at ~ 220 nm forms. As more H is lost, the UV absorption narrows and shifts toward longer wavelengths, and is accompanied by an increasing brightness toward shorter wavelengths, the FUV rise, such as is seen at Ceres. The more evolved carbonaceous surfaces in the inner solar system should exhibit a stronger UV absorption feature and associated far-UV rise. We propose that this change in UV spectral signature could flag an asteroid's formation location in the primitive solar system, and that this diagnostic feature could be used to determine whether asteroids were shifted during a violent mixing episode in early solar system history. Asteroid families represent one way to test these ideas. Careful observations would accommodate space weathering effects. Future observations require space-based observations.
ALMA observations a 1mm and the detection of Propynal
VILLICANA PEDRAZA, ILHUIYOLITZIN
Past surveys at mm wavelengths from the prototypical starburst galaxies NGC 253 and M82 have shown chemical abundance of molecular species to vary significantly as a function of the evolutionary stage of each starburst nuclear region. Multi-line ALMA studies of NGC 253 at 3mm and 0.85mm were published in 2015 and 2017 which reports the tentative detection of molecules previously undetected from single dish observations.We report a first part of ALMA observations using an array of 38 antennae in band 7 of the starburst galaxy NGC 253 at 1mm, we mapped at an angular resolution of 0.26 arcseconds toward the starburst galaxy NGC 253. Amongst other molecules, we did a tentative detection of Propynal and prebiotic molecules. We determined the flux density for each molecule with components and transitions; we studied the spatial distribution and present the corresponding integrated maps, also the position velocity maps. Flux is consistent with previous authors of the same source with ALMA. We compare our results with those from other sources and other frequencies as well as with the Galactic Center.
Citizen Science and the virtual observatory with college students
VILLICANA PEDRAZA, ILHUIYOLITZIN
The Citizen Science Astronomy (CSA) as a collaboration of scientists, software developers and educators, is an excellent project to motivate college students to be young scientist. In order to introduce the students to be part of the citizen science we teach in the astronomy classes to the students how can they can study and analyze the astronomical objects. We are trying to combine the Citizen Science and the Virtual observatory. Some of the students are not from STEM, but they are introduced in the real life of a scientist and the problems that we have in our careers, in special with financial support of the projects, and one day they can be motivated to help the science projects and invite more people like them. Here we present an experiment from around a year with college students using the Citizen Science and the Virtual Observatory.
Evolution of N/O ratios in galaxies from cosmological chemodynamical simulations
Vincenzo, Fiorenzo
We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual ISM regions within single spatially-resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients which have settled in the galaxy interstellar medium, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where -- at any redshift -- less massive galaxies have lower average O/H and N/O ratios than the more massive ones. For both local and global relations, the predicted N/O--O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy interstellar medium gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O--O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially resolved galaxy.
Optical counterparts of two ultraluminous X-ray sources NGC4559 X-10 and NGC4395 ULX-1
Vinokurov, Aleksandr
We study the optical counterparts of ultraluminous X-ray sources NGC 4559 X-10 and NGC 4395 ULX-1. Their absolute magnitudes, after taking the reddening into account, are MV ≈ −5.3 and MV ≈ −6.2, respectively. The spectral energy distribution of the NGC 4559 X-10 counterpart is well fitted by a spectrum of an A-type star, whereas NGC 4395 ULX-1 has a blue power-law spectrum. Optical spectroscopy of NGC 4395 ULX-1 has shown a broad HeII λ4686 emission, which puts this object in line with all the other spectrally-studied ULXs. Analyzing the absolute magnitudes of 16 well-studied ULX counterparts we find that the intrinsically fainter counterparts with MV > −5.5 have on average black body like or power law spectral energy distributions. In other ULX counterparts with MV < −5.5 we may observe a power law like SED, the only one donor is in NGC 7793 P-13 (the ULX-pulsar). One may suggest that as the original accretion rate decreases (but nevertheless remains supercritical), the optical luminosity of the wind becomes lower and the donor star might dominate. Using the Swift archival X-ray data for NGC 4395 ULX-1, we have found a period of 62.8 ± 2.3 days. The X-ray phase curve of the source is very similar to the precession curve of SS 433.
Building the detailed rotation maps of the LMC featured in Gaia Data Release 2
Vitorino da Silva, André Filipe
While the rotation in proper motion of the Large Magellanic Cloud (LMC) has been observationally established for two decades, studies have been based in up to a few tens of stars, only allowing to envisage the global direction and speed of rotation.Gaia Data Release 2 (DR2) has delivered parallaxes and proper motions for more than 1.3 billion sources. The roughly 24 million of these sources in the direction of the LMC have allowed to create maps showing with great detail the rotation field of the LMC. These maps have been highlighted in the European Space Agency (ESA) web pages and DR2 press releases. Their fingerprint appearance has captured popular interest, having featured in many traditional and web media.In this poster, we discuss the data selection criteria and present the data treatment and visualisation techniques used for creating the rotation maps of the LMC.
On the evolution of the scale height of the Milky Way disc
Vitorino da Silva, André Filipe
In the absence of direct detections of dark matter, the study of dark matter induced perturbations in the Galactic disk is done by analysing the morphology and kinematics of the detectable constituents. These include the continuous interstellar medium, and discrete objects such as giant molecular clouds, individual stars and star clusters. One key morphological indicator is the scale height of the (thin) disc and its evolution. However, the scale height evolution of the different types of objects can be driven by different phenomena. These must be well understood if the effects of dark matter perturbations are to be isolated.The scale height of open star clusters in the Milky Way exhibits a well known increase with age. This increase is usually attributed, in a vague way, to disc heating mechanisms similar to those that act on individual stars. In this poster, we address the evolution of the scale height of open clusters from a different angle. We present a dynamical model that follows the orbits of open clusters and includes their disruption due to interactions with the disc, mostly encounters with giant molecular clouds. We show how simulations with this model reproduce the observed open cluster vertical distributions remarkably well. Still, the current compilations of open cluster parameters are affected by a number of selection effects and some of them are contaminated by significant numbers of non existing clusters. We discuss these sample effects in the light of the possibilities brought by Gaia Data Release 2 as well as future releases from Gaia and other astrometric surveys.
Possible relations between outbursts and diamagnetic cavities in comet 67P/Churyumov-Gerasimenko
Voelzke, Marcos Rincon
On 2014 August 06 the Rosetta spacecraft arrived at comet 67P/Churyumov-Gerasimenko. Since then, the spacecraft accompanied the comet on its journey around the Sun (Glassmeier et al. 2007a), until the end of the mission on 2016 September 30. This work tries to understand the possible connections between the 665 reported diamagnetic regions (Goetz et al. 2016), detected from April 2015 to February 2016 around the comet 67P/Churyumov-Gerasimenko, with the fluxgate magnetometer of the Rosetta Plasma Consortium (RPC-MAG), when the heliocentric distance of the comet from the sun varied from 1.8 to 2.4 AU and the 34 reported outbursts (Vincent et al. 2016), detected from July to September 2015, with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras, when the ESA´s Rosetta spacecraft changed the cometocentric distance from 155 to 817 km.
On the expected accuracy of classical nova identifications among historical far-eastern guest star observations
Vogt, Nikolaus
More than 100 guest star observations have been obtained by Chinese, Korean, Japanese and Vietnamese astronomers between ~ 600 BC and ~1690 AD. Based on 8 supernova recoveries among these historical sources, we estimate that a typical positional accuracy of the order of ± 3 degrees could also be expected for the error bar between a classical nova observed as a guest star and its modern counterpart among known cataclysmic variables (CVs). However, there are considerable disagreements among modern authors in the interpretation of ancient far-eastern texts, emphasizing the need to consult again the original historic sources, in order to improve our interpretation. Finally we present a statistical analysis of the probability of casual miss-identifications, based on frequency and galactic distribution of CVs in the AAVSO-VSX catalogue.
Training at the telescope for students of Moscow State University
Voloshina, Irina
The preparation of students for research is very important for their education. During undergraduate years students often decide on areas of research and enter graduate programs in those areas. So professional training of the students is very important for their future successful work. A new observatory of Sternberg Astronomical Institute,- Caucasian Mountain Observatory, which was build recently in surroundings of Kislovodsk, gives a very good possibilities for young astronomers for training at the telescope with 2.5m telescope. Another good possibility for professional training of our students is Crimean Observational Station of Sternberg Atronomical Institute with 5 telescopes.
Results of Light Curves Analysis for Eclipsing Dwarf Nova ASASSN-13cx
Voloshina, Irina
The star was observed with the 50-cm and 60-cm telescopes and a CCD photometer during the variable’s outburst of August–September 2014 and in a period of quiescence in October–November 2016. The light curves of ASASSN-13cx were plotted by these data. We used two models to determine the parameters of the ASASSN-13cx in different activity states. Parameters of the system are derived from the light curves in quiet state using a “composite” model that takes into account the presence of a hot spot on the lateral surface of the geometrically thick disk and of a region of enhanced energy release near the disk edge, at the base of the gas low (the so-called “hot line”). The light curves obtained during the outburst are also used together with a “spiral” model that additionally takes into account the presence of geometric perturbations on the accretion disk surface. The parameters of ASASSN-13cx determined using these models provide good accuracy in reproducing the system’s light curves in both states. The basic parameters of the system have been determined for the first time: the component mass ratio q =M1/M2 = 7.0, the orbital inclination i = 79.9-80.1o, the distance between the components’ centers of mass a0 = 0.821(1)Ro and sizes and temperatures of the stars: R1 =0.0102(4)Ro, T1 = 12 500+/- 280 K, R2 = 0.194(3) Ro, T2 = 2 550+/- 400 K, corresponding to M4–9V for the spectral type of the secondary. Parameters of the accretion disk have been derived for both activity states. The mass of matter in the accretion disk increased by almost a factor of two during ~400 orbital periods in quiescence. The ASASSN-13cx system is confirmed to be a SU UMa variable.
Superhumps Phenomenon in SU UMA Stars
Voloshina, Irina
Dwarf novae belong to the class of cataclysmic variables and represent the close binary systems in the late evolutionary stages. They consist of a white dwarf and a red dwarf which fills its Roche lobe and transfers mass to the white dwarf. The gas stream flows from the secondary to the primary white dwarf forming an accretion disk around it. Dwarf novae undergo outburst in semi-periodic intervals of time, when the brightness increases by 3m to 5m. For most of them, the faint state (or quiescence) is a normal state. There are 3 types of dwarf novae: U Gem, Z Cam and SU UMa. The last ones have orbital periods about 80-180 min, mass of the secondary 3 times less or even more than white dwarf mass. Two types of outbursts are observed in these systems: frequent normal outbursts and superoutbursts which last longer and rise to slightly higher luminosities. During superoutburst they exhibit so-called “superhumps”, - brightness increase on the small part of the light curve repeated with the period a few percents longer than the orbital one and amplitude of about 0.1 – 0.3m. Superhumps are the most striking phenomenon which exhibited SU UMa dwarf novae and make them interesting and promising objects for study. According to the tidal-thermal model (Osaki, 1996) superhumps are due to gravitational disturbances from the secondary. These disturbances became most effective then the matter of accretion disk reach the 3:1 resonance of the orbital motion of the secondary. The beating of the orbital and precessional periods cause periodic variations, identified as superhumps. Positive and negative superhumps are described. The evolution of superhumps is considered together with the changes of superhump period during the outburst. The criterion for classification of WZ Sge dwarf novae (sub-type of SU UMa) are summarized. Rebrightenings or echo outbursts are one of the most striking characteristics of WZ Sge objects.
Dust dynamics and growth in young protostellar disks
Vorobyov, Eduard
I will report on the early evolution of dust in gravitationally unstable protostellar disks with different values of the viscous alpha-parameter and dust fragmentation velocity. The disk evolution is studied using numerical hydrodynamics simulations modified to include a dust component consisting of two parts: sub-micron-sized dust and grown dust. The former is strictly coupled to the gas, while the latter interacts with the gas via friction and gravity. The conversion of small to grown dust, dust growth, settling, and dust self-gravity are also considered.I will show that the process of dust growth known for the older protoplanetary phase also holds for the embedded phase of disk evolution. The process of small-to-grown dust conversion is very fast once the disk is formed. The total mass of grown dust in the disk reaches hundreds of Earth masses already in the embedded phase of star formation, and even a greater amount of grown dust drifts in the inner, unresolved 1 AU of the disk. Nevertheless, the bulk of the disk is usually dominated by small dust, except for the inner several tens of AU where grown dust prevails, thanks to efficient inward radial drift of grown dust and continuing replenishment by small dust from the infalling envelope. Dust does not usually grow to radii greater than a few cm, with a notable exception of models with alpha <= 10-3, in which case a zone with reduced mass transport develops in the inner disk and dust can grow to meter-sized boulders in the inner 10 AU. The efficiency of grown dust accumulation in spiral arms is stronger near corotation where the azimuthal velocity of dust grains is closest to the local velocity of the spiral pattern. The implications of fast dust growth for planet formation will also be discussed.
Knotty protostellar jets as a signature of episodic protostellar accretion?
Vorobyov, Eduard
The possible causal link between the knotty jet structure in CARMA 7, a young Class 0 protostar in the Serpens South cluster, and episodic accretion in young protostellar disks will be demonstrated. The protostellar accretion history was derived using numerical hydrodynamics simulations of gravitationally unstable disks around solar-mass protostars showing luminosity bursts caused by dense gaseous clumps spiraling on the protostar (Vorobyov & Basu 2015, ApJ). I will show that the time spacings between the luminosity bursts correlate with the time spacings between the knots in the jet of CARMA 7, if a certain correction for the (yet unknown) inclination angle with respect to the line of sight is applied to the observational data. Implications of episodic accretion for dust growth, chemical disk composition, stellar evolution, and planet formation will be discussed.
Supernova remnants in dwarf elliptical galaxy NGC185
Vucetic, Milica
In this paper we present our optical observations of NGC185 galaxy, which aimed to retrieve final status of supernova remnants (SNRs) in this dwarf elliptical companion of Andromeda galaxy. Previously, it was reported that this galaxy hosts one SNR. Our recent deep photometric study through narrow-band Hα, [SII] and continuum filters has revealed complex structure of the interstellar medium in the center of the galaxy, also proposing that there could be more than one SNR. In order to confirm the SNR origin and study the kinematics of the detected nebulae, we carried out spectroscopic observations using the SCORPIO multi-mode spectrograph at the 6-m telescope at Special Astrophysical Observatory of the Russian Academy of Science, both in low (FWHM~500 km/s) and high (FWHM~120 km/s) resolution modes. We revealed the enhanced [SII]/Hα and [NII]/Hα line ratios, as well as high expansion velocities of the observed nebulae, indicating their nature as SNRs.
Discovery of a dying, giant radio galaxy in the distant Universe
Wadadekar, Yogesh
We report the discovery of a intriguing relic Giant Radio Galaxy (GRG) J021659-044920 at redshift z~1.3 that exhibits large-scale extended, nearly co-spatial, radio and X-ray emission from radio lobes, but withoutdetection of Active Galactic Nuclei core, jets and hotspots. The total angular extent of the GRG at the observed frame 0.325 GHz, using Giant Metrewave Radio Telescope observations is found to be ~2.4 arcmin,that corresponds to a total projected linear size of ~1.2 Mpc.The integrated radio spectrum between 0.240 and 1.4 GHz shows high spectral curvature with sharp steepening above 0.325 GHz, consistent with relic radio emission that is ~8 X 10^6 yr old. The radio spectralindex map between observed frame 0.325 and 1.4 GHz for the two lobes varies from -1.4 to -2.5 with the steepening trend from outer-end to inner-end, indicating backflow of plasma in the lobes. The extended X-ray emission characterized by an absorbed power law with photon index ~1.86 favours inverse-Compton scattering of the Cosmic Microwave Background (ICCMB) photons as the most plausible origin.Using both X-ray and radio fluxes under the assumption of ICCMB we estimate the magnetic field in the lobes to be 3.3 microG. The magnetic field estimate based on energy equipartition is ~3.5 microG. Our work presents a case study of a rare example of a GRG caught in dying phase in the distant Universe.
Learnings from multilingual astronomy outreach in eight Indian states
Wadadekar, Yogesh
Over the last decade, the author who is a research astronomer, has carried out more than 50 outreach programs in eight Indian states in 4 languages (3 Indian languages + English) to a variety of audiences ranging from students at the most privileged schools to students at rural, underprivileged poorly funded schools where the students are almost always the only literate people in their family. These interactions have ranged from formal slide presentations to night sky gazing (with and without a telescope) to informal question and answer sessions on science in general and astronomy in particular.All over India, like perhaps everywhere in the world, interest in astronomy is universal and at these outreach programs, it is common to see school children bringing their parents and grandparents along. Field astronomy is the cheapest, most universally accessible and most interesting introduction to science, particularly in societies where science literacy is very low. Many ideas in mathematics, physics, geography and the especially rich mythology ofIndia can be illustrated through astronomy demonstrations. Many misconceptions derived from the deeply entrenched astrological beliefs can also be discussed in a modern astronomical context.I will share my experiences and thoughts on how astronomy concepts can be introduced to students at the high school level in an interesting, inclusive and non-condescending way while still maintaining scientific accuracy.
The GMRT Archive Processing Project
Wadadekar, Yogesh
The GMRT Online Archive houses over 80 terabytes of interferometricobservations obtained with the GMRT, since the first public observingcycle in 2002. The utility of this vast archive of raw UVvisibilities, likely the largest of any Indian telescope, can besignificantly enhanced if first look (and where possible, scienceready) processed images can be made available to the usercommunity. We have initiated a project to pipeline process GMRT imagesin the 150, 240, 325 and 610 MHz bands. The SPAM pipeline developed byHuib Intema is being used for this purpose. A prototyping run on about4 TB of data from 3 observing cycles has been successfully completedand issues with the processing have all been resolved. In Feb 2018, wehave initiated a production run on a cluster with about 250 cores.The thousands of processed continuum images that we will produce willprove useful in studies of distant galaxy clusters, radio AGN, as wellas nearby galaxies and star forming regions. Besides the scientificreturns, a uniform data processing pipleine run on a large volume ofdata can be used in interesting ways. For example, we will be able tomeasure various performance characteristics of the GMRT telescope andtheir dependence on waveband, time of day, RFI environment, backend,galactic latitude etc. in a systematic way. Since the SPAM pipelinealso carries out direction dependent modeling of ionospheric phaseerrors, we will also be able to measure differential ionospheric phasedelays over thousands of sightlines over the entire solar cycle tobetter understand the properties of the earth's ionosphere.A variety of data products such as calibrated UVFITS data, sky images,Hierachical Progressive Survey (HiPS) images, PyBDSF catalogs and AIPSprocessing logs will be delivered to users via the NCRA Archive andProposal Management system (NAPS). Data products will be compatiblewith standard Virtual Observatory protocols.
Cultivating Talented Youth with Big Data Teen Astronomy Cafés
Walker, Constance
The Education and Public Outreach group at the U.S. National Optical Astronomy Observatory has designed an outside-of-school education program to excite the interest of talented youth in future projects like the Large Synoptic Survey Telescope (LSST) and the NOAO Data Lab – their data approaches and key science projects. Originally funded by the LSST Corporation, the Teen Astronomy Café program cultivates talented youth to enter Science, Technology, Engineering and Math (STEM) disciplines and serves as a model to disseminate to observatories worldwide.One Saturday a month during the academic year, high school students have the opportunity to interact with expert astronomers who work with large astronomical data sets in their scientific work. Students learn about killer asteroids, the birth and death of stars, colliding galaxies, the structure of the universe, gravitational lenses, dark energy, dark matter, and more. The format for the Saturday science cafés has been a short presentation, discussion (plus food), a computer lab activity and more discussion (with pizza), in particular about careers. They last about 2.5 hours and have been planned by a group of interested local high school students, undergraduate student coordinator, graduate students, presenting astronomers, program director and evaluator.For example, high school youth leaders help ensure an enjoyable and successful program for fellow students. They help their fellow students with the activities and help evaluate how well the science café went. Their remarks shape the next science café and improve the program. The experience offers youth leaders ownership of the program, opportunities to take on responsibilities and learn leadership and communication skills, as well as foster their continued interests in STEM.We will discuss outcomes and lessons learned from the dozen science cafés implemented thusfar, plans to disseminate the program to other IAU observatories and plans to expand the program locally.
Globe at Night: Citizen-Science Assessing the Darkness of our Skies
Walker, Constance
Globe at Night (GaN) encourages citizen-scientists worldwide to record the brightness of the night sky. During ten-days per month of moonless evenings, children and adults match the appearance of a constellation with star maps of progressively fainter stars found at www.globeatnight.org/webapp/. In the 12 years of the program, over 175,000 observations from 180 countries have been contributed to the campaign.The GaN (open) database is a source of research projects. With GaN, citizen-scientists measured the darkness of the daytime sky for the total solar eclipse (TSE) in the USA in 2017. (Plans are forming for the TSE in Chile in 2019.) Students conducted research to understand the lesser long-nosed bats’ avoidance of city center at night. On-the-fly mapping enables citizen-scientists to see contributed observations immediately. The 12 campaigns per year offer 4 ways of taking measurements. The online app for data submission is in 28 languages. STEM activities allow young children and problem-based learning activities for older students to experience real-life scenarios: role-playing sea turtles hatching (misdirected by lights on shore) or analyzing an ISS image of Houston to estimate the wasted energy, cost and carbon footprint. In-situ and on-line workshops have been given on using GaN in all its capacities, as well as for the activities. Our Facebook page exists to encourage dialogue and bring cutting edge news. To entice interest, we had monthly newsletters and serial podcasts starring the Dark Skies Crusader. GaN has been part of special campaigns like with the National Park Service and the National Geographic BioBlitz. Partnerships also include SciStarter (working with participants), Fieldscope (working with data analysis), and STARS4ALL (working with other light pollution initiatives). We have built a community of practitioners in various ways worldwide and plan to continue to help reduce the effects of light pollution through awareness and action.
Towards an IAU Position and Public Statement on Terrestrial Climate Change
Waller, William
As the largest organization of astronomers in the world, the International Astronomical Union (IAU) has a responsibility to explain important astronomical findings and to communicate agreements on key definitions, fundamental standards, naming conventions, etc. The IAU typically does not take stands on terrestrial issues, unless there is a strong astronomical connection. In the case of terrestrial climate change, the connection is both strong and revealing. Earth is not alone in having an atmosphere that contains greenhouse gases. Both Venus and Mars have atmospheres that are dominated by carbon dioxide – a potent greenhouse gas. Venus, in particular provides startling evidence for drastic surface warming due to its thick blanket of carbon dioxide. In this poster, I present quantitative interplanetary perspectives on terrestrial climate change, and how these perspectives could inform an IAU position and public statement on this vital topic.
Measuring spatially resolved gas-to-dust ratios in AGB stars
Wallstrom, Sofia
Asymptotic Giant Branch (AGB) stars form significant circumstellar envelopes of gas and dust, but the relation between these two components is not well understood. The gas-to-dust ratio across the envelope carries vital information about, e.g., the dust-condensation efficiency, and is often used to assume a gas mass from a measured dust mass and vice versa. A canonical value of 100 or 200 is often used for Galactic stars. Knapp (1985) measured gas-to-dust ratios in Galactic evolved stars -- finding ratios around 160 for O-rich stars, and 400 for C-rich stars -- which remains the only direct measurement of this ratio for evolved stars in the Solar Neighbourhood. We have directly measured gas and dust masses for a sample of 15 nearby AGB stars, using JCMT CO-line and continuum observations. This serves as a pilot study for the Nearby Evolved Stars Survey (NESS; PI: P. Scicluna) project which will provide similar observations of ~400 AGB stars in a volume-limited sample out to 2 kpc.The addition of submm continuum data to existing IR photometry allows us to constrain the cold dust component and hence calculate dust masses from near-IR to submm SED fits (Dharmawardena et al., in prep). The continuum observations are matched with multi-pixel CO 3-2 observations and mapping observations of CO 2-1, providing spatially resolved gas-to-dust ratios. We derive gas masses by fitting the CO emission with an improved version of the line radiative transfer code presented by Kemper et al. (2003). It now includes a sophisticated algorithm to explore parameter space and find the best fit model to the observations and robust statistical uncertainties. The model also provides results at a range of impact parameters throughout the circumstellar envelope and can correctly account for data from different telescopes, both single-dish and interferometric, allowing us to fit spatial information along with the line profiles. This code will be publicly released as part of the NESS project.
Activities of UK IAU National Outreach Coordinator 2018
Walsh, Robert
This poster will outline some of the major outreach and public engagement activites undertaken in the UK in 2018.
Blackpool PIER (Physics: Inspire, Engage, Research)- working with low science capital communities in the UK
Walsh, Robert
The seaside resort of Blackpool, Lancashire, UK holds a unique place in the affections of British people. Known for it’s iconic landmarks of the Blackpool Tower and Pleasure Beach, a busy summer season is followed in autumn by the Blackpool Illuminations, attracting over 4 million visitors.However, government statistics reveal Blackpool as England’s fourth most deprived area, with soaring deprivation measures. In particular, the percentage of pupils achieving good school exit exam grades is declining and is substantially below the UK average (40% compared to 65% nationally). Consequently, it is estimated that only 12% of young people will enter higher education. Blackpool is a prime example of a region with exceptionally “low science capital”. The concept of science capital is a science-related form of cultural and social capital employed as a theoretical lens for explaining differential patterns of aspiration and educational participation in science amongst young people (Archer et al, 2015, J Res Sci Teach, 52: 922).This work will outline the 1st year results of an ambitious 3 year longitudinal public engagement programme with a specific cohort of young people as they are followed from their last year in primary school (10/11 years old) through to their early years in secondary education (12/13). Funded by the UK’s Science and Technology Facilities Council Leadership Fellow programme, this work consists of school visits and community events plus trips to specialized facilities at the University of Central Lancashire (UCLan).With overall aims to improve the experience of astronomy for this targeted cohort and to inspire them through activities that increase their exposure to and enhance their confidence in engaging with STEM, the approach to relationship building with the cohort will be discussed. Also the evaluation of any improvement of the their science capital metrics in the first year of interventions will be explored and compared to other external benchmarks.
Preparing for MAGIXS: exploring the solar corona from 6 to 24 Angstroms via a multi-stranded, episodic heating approach
Walsh, Robert
For decades, X-ray, EUV, and UV spectral observations have been used to determine the physical properties of the solar atmosphere. There have been substantial improvements in the spectral, spatial, and temporal resolution of the observations in the EUV and UV wavelength ranges. However, at wavelengths below 100 °A, observations of the corona with simultaneous spatial and spectral resolution are limited; in fact, not since the late 1970’s have spatially resolved solar X-ray spectra been measured. As this soft X-ray regime is dominated by emission lines formed at high temperatures, X-ray spectroscopy yields insights to fundamental physical processes that are not accessible by any other means.Using a novel implementation of corrective optics, the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) will measure, for the first time, the solar spectrum from 6 – 24 Angstroms with an approximate 6 arcsec resolution (2.8 arcsec/pixel) over an 8 arcmin slit. MAGIXS is scheduled for launch on a sounding rocket in Summer 2019.With its powerful set of plasma diagnostics, MaGIXS will probe the high temperature coronal plasma and make a number of unique measurements including;observe emission from Fe xvii - Fe xx to undertake measurements of the temperature distribution above 4 MK in an active region;search for signatures of impulsive heating by measuring the composition of high temperature plasma,;characterize the temporal variability of high temperature plasma using spectroscopic observations of Fe xvii at high cadence.Employing a multi-stranded coronal loop model that introduces small-scale, episodic heating bursts along the strands, it is possible to predict the basic nature of these MAGIXS observations across the relevant spectral lines for a range of heating frequency scenarios. Thus this work will investigate the observable differences between different energy depositions and provide important constraints on coronal heating parameters.
Long-term tidal evolution: the role of mantle convection
Walterova, Michaela
The long-term orbital evolution of planets and moons is closely linked to their internal evolution: the tidal deformation of the planet and the corresponding torque depends on its temperature-dependent rheological properties. As the planet evolves, the heat is transported from the deep parts of the body to the surface and the internal temperature tends to decrease, making the planet less deformable. At the same time, the tidal deformation of the planet can lead to a significant internal heating and to the increase in temperature, together with decrease in the mantle viscosity. This would, on the other hand, result in a more deformable body.The aim of this study is to assess the role of internal dynamics in the long-term orbital evolution of differentiated terrestrial (exo)planets and icy moons subjected to tides. The thermal evolution is investigated by a model of parameterized (1D) subsolidus convection (see e.g. [1]), while the tidal response of the planet is described by the set of partial differential equations derived in [2]. This enables the prescription of arbitrary linear viscoelastic rheology with different temperature-dependent material parameters in each layer (see also [3]) and the computation of frequency-dependent complex Love numbers. These parameters govern the evolution of both the spin rate and the orbit, as described in [4]. We perform several parametric studies concerning the dependence of the Love numbers and stable spin states on the internal structure and compare them with a time-evolving, convecting model. Semi-analytical results are also compared to a fully numerical 3D model [5].[1] Hussmann, H., Spohn, T. (2004). Icarus, 171(2), 391-410.[2] Wu, P., Peltier, W. R. (1982). Geoph. J., 70(2),435–485.[3] Tobie, G., et al. (2005). Icarus, 175(2), 496-502.[4] Kaula, W. M. (1964). Rev. Geophys., 2(4), 661–685.[5] Walterová, M., Behounková, M. (2017). Celest. Mech. Dyn. Astr., 129(1-2), 235–256.
Climate model for habitable locked planets (Mini conference on planetary astronomy)
Wandel, Amri
Habitable Zone planets of M-dwarfs are likely to synchronously orbit their host star. Recent detections of planets in the habitable zone of Proxima Centauri, Trappist-1, and many other nearby M-type stars, as well as the easier detection of bio-signatures of planets orbiting M-dwarfs by future telescopes, raise the need for a simple climate model for such planets, that can calculate actual habitability limits for many atmosphere types. We derive a simple 1-D semi-analytical model for the surface temperature distribution of synchronously rotating planets, taking into account their atmospheric properties. The atmospheric impact on the temperature is quantified in terms of the greenhouse heating, stellar irradiation, albedo and heat redistribution (Wandel 2018, ApJ). The results suggest that planets orbiting M-type stars may have life-supporting temperatures, at least on part of their surface, for a wide range of atmospheric properties.
WD+AGB star as the progenitors of type Ia supernovae
Wang, Bo
The origin of the progenitors of type Ia supernovae (SNe Ia) is still uncertain. The core-degenerate (CD) channel has been proposed as an alternative way for the production of SNe Ia. In this channel, SNe Ia are formed at the final stage of common-envelope evolution from a merger of a carbon-oxygen white dwarf (CO WD) with the CO core of an asymptotic giant branch companion. However, the birthrates of SNe Ia from this scenario are still not well determined. In this work, we performed a detailed investigation on the CD channel based on a binary population synthesis approach. The SN Ia delay times from this scenario are basically in the range of 90Myr-2500Myr, mainly contributing to the observed SNe Ia with short and intermediate delay times although this scenario can also produce some old SNe Ia. Meanwhile, our work indicates that the Galactic birthrates of SNe Ia from this scenario are no more than 20% of total SNe Ia due to more careful treatment of mass transfer. Although the SN Ia birthrates in the present work are lower than those in Ilkov & Soker, the CD scenario cannot be ruled out as a viable mechanism for the formation of SNe Ia. Especially, SNe Ia with circumstellar material from this scenario contribute to 0.7-10% of total SNe Ia, which means that the CD scenario can reproduce the observed birthrates of SNe Ia like PTF 11kx. We also found that SNe Ia happen systemically earlier for a high value of metallicity and their birthrates increase with metallicity.
The Role of Magnetic Field in State Transitions of BHXBs
Wang, Ding-Xiong
The role of magnetic field in state transitions of black hole X-ray binaries (BHXBs) is roughly described, and the following issues are discussed: (i) Why does each outburst of BHXBs always start from low/hard state (LHS), tracing an anti clockwise path in HID? (ii) Why are Episodic relativistic jets associated with intermediate state (IMS)? (iii) Does jet power correlate with black-hole spin? (iv) Why are steady jets associated with LHS, while disk winds appear in high/soft state (HSS)? It turns out that magnetic field can be regarded as the‘second parameter’ determining state transitions of BHXBs.
ONe WD+He star systems as the progenitors of intermediate-mass binary pulsars
Wang, Bo
It has been suggested that accretion-induced collapse (AIC) is a non-negligible path for the formation of the observed neutron stars (NSs). An ONe white dwarf (WD) that accretes material from a He star may experience AIC process and eventually produce intermediate-mass binary pulsars (IMBPs), named as the ONe WD+He star scenario. However, previous studies can only account for part of the observed IMBPs with short orbital periods. In this work, we investigate the evolution of about 900 ONe WD+He star binaries to explore the distribution of IMBPs. We found that the ONe WD+He star scenario could form IMBPs including pulsars with 5-340 ms spin periods and 0.75-1.38 Msun WD companions, in which the orbital periods range from 0.04 to 900 d. Compared with the 20 observed IMBPs, this scenario can cover the parameters of 13 sources in the final orbital period-WD mass plane and the Corbet diagram, most of which has short orbital periods. We found that the ONe WD+He star scenario can explain almost all the observed IMBPs with short orbital periods. This work can well match the observed parameters of PSR J1802-2124 (one of the two precisely observed IMBPs), providing a possible evolutional path for its formation. We also speculate that the compact companion of HD 49798 (a hydrogen depleted sdO6 star) may be not a NS based on the present work.
The Transneptunian Automatic Occultation Survey (TAOS II) Project
Wang, Shiang-Yu
The Transneptunian Automated Occultation Survey (TAOS II) will aim to detect occultations of stars by small (~1 km diameter) objects in the Kuiper Belt and beyond. Such events are very rare (< 10-3 events per star per year) and short in duration (~200 ms), so many stars must be monitored at a high readout cadence. TAOS II will operate three 1.3 meter telescopes at the Observatorio Astron´omico Nacional at San Pedro M´artir in Baja California, M´exico. With a 2.3 square degree field of view and a high speed camera comprising CMOS imagers, the survey will monitor 10,000 stars simultaneously with all three telescopes at a readout cadence of 20 Hz. We expected to detector more than 10 occultation events every year based on the system paprameters. Construction of the site began in the fall of 2013, and the site preparation was completed in 2017. The commissioning of the telescopes, cameras and the control system for the survey started in late 2017. The survey will begin in the summer of 2018. In this report, the details of the project and the current status of the project will be presented.
Probing ancient High-energy explosions using Radiocarbon in tree rings
Wang, Fayin
Cosmic rays interact with the Earth's atmosphere to produce 14C, which can be absorbed by trees. Therefore, rapid increases of 14C in tree rings can be used to probe previous cosmic-ray events. By this method, three 14C rapidly increasing events have been found. Plausible causes of these events include large solar proton events, supernovae, or short gamma-ray bursts. However, due to the lack of measurements of 14C by year, the occurrence frequency of such 14C rapidly increasing events is poorly known. In addition, rapid increases may be hidden in the IntCal13 data with five-year resolution. Here we report the result of 14C measurements using an ancient buried tree during the period between bc 3388 and 3358. We found a rapid increase of about 9‰ in the 14C content from bc 3372 to bc 3371. We suggest that this event could originate from a large solar proton event.
Particles Acceleration in the Kilonovae Shock
Wang, Xin
Cosmic ray generally can be accelerated by the astrophysical shock,e.g. for SNR or AGN. The cosmic ray energy spectrum with its largeenergy range from GeV to ZeV (~1021eV). Generally, the energyspectrum below "knee" (3.5X1015eV) can be accelerated by thegalactic origins. But the energy spectrum beyond "knee" could beoriginated from the extragalactic Universe, this part remain poorlyunderstood. Magnetic field and the amplification in theastrophysical burst will play important role on the particlesacceleration at the astrophysical shocks. However, there is scarcelytheoretical model can directly verify the astrophysical magneticfield in galactic origins accelerate the particle energies to the "knee" energy range. In this work, we perform a simulation tocalculate the particles acceleration processes at the kilonovaeshock. We suggest that the kilonova environment driven a shock couldaccelerate the particles to the energy spectral "knee" with theiramplification of the magnetic turbulence.
Particles Acceleration in Heliosphere Converging Shocks
Wang, Xin
Observations by spacecraft such as ACE, STEREO, and others, showthat there are proton spectral ``breaks'' with energy Ebr at 1-10MeVin some large CME-driven shocks. Generally, a single shock applyingdiffusive acceleration mechanism would not predict the ``broken''energy spectrum. The present talk focuses on two converging shocksto identify this energy spectral feature. In this case, twoconverging shocks include the one forward CME-driven shock on13-Dec-2006 and the another one backward Earth-bow shock. Wesimulate the detailed particles acceleration processes in convergingshocks region by Monte Carlo method. As a result, we do not onlyobtain an extended energy spectrum with a higher energy ``tail'' upto a few 10MeV than that in previous single shock model, but also wefind an energy spectral ``break'' occurring on ~ 5.5MeV. Thispredicted energy spectral shape is consistent with the observationsfrom multiple spacecraft. The spectral ``break'', then, in this caseis caused by the interaction with the CME shock and Earth's bowshock, and otherwise would not be present if Earth were not in thepath of the CME. The electron energy spectral ``break'' is alsoverified by the DAMPE satellite.
Particles Acceleration in the Pileup Shocks
Wang, Xin
Many observations show that large ground-level enhancement (GLE)events are often associated with twin coronal mass ejections(CMEs).The pileup shock scenario means that the preceding CME-drivenshock provides an enhanced-level turbulence at the upcomingCME-driven shock with a more large bulk velocity. In this work, wefocus on the GLE event on 2012 May 17, which would be associatedwith the twin-CME interactions. Using the particle simulation methodto examine the particle acceleration and the energy spectral featureby the impact of the preceding CME-driven shock interacting with theforthcoming CME-driven shock. In this case, we use the precedingCMEs-driven shock to produce an enhanced seed proton populationinjecting into the later CME-driven shock for particlere-acceleration. As results, we simulate the pileup shockinteractions and obtain the energy proton spectrum. We find that thepileup-shock interactions lead to an ``ankle-like" proton spectralslope in their GLE production. This simulated property is consistwith some observations from the heliosphere spacecraft.
The Formation Rate of Short Gamma-Ray Bursts and Gravitational Waves
Wang, Fayin
In this talk, we use the Lynden-Bell c- method to study the luminosity function and formation rate of short gamma-ray bursts without any assumptions. A strong evolution of luminosity L(z)?(1+z)4.47 is found. After removing this evolution, the luminosity function is ?(L)?L-0.29±0.010 for dim sGRBs and ?(L)?L-1.07±0.010 for bright sGRBs, with the break point 8.26×1050 erg s-1. We also find that the formation rate decreases rapidly at z<1.0, which is different with previous works. The local formation rate of sGRBs is 7.53 events Gpc-3 yr-1. Considering the beaming effect, the local formation rate of sGRBs including off-axis sGRBs is 203.31+1152.09-135.54 events Gpc-3 yr-1. We also estimate that the event rate of sGRBs detected by the advanced LIGO and Virgo is 0.85+4.82-0.56 events yr-1 for NS-NS binary.
The Near-infrared Optimal Distances Method Applied to Galactic Classical Cepheids Tightly Constrains Mid-infrared Period–Luminosity Relations
WANG, SHU
Classical Cepheids are well-known and widely used distance indicators. Since distance and extinction are usually degenerate, it is important to develop suitable methods to robustly anchor the distance scale. Here, we introduce a near-infrared (near-IR) optimal distance method to determine both the extinction values of and distances to a large sample of 289 Galactic classical Cepheids. The overall uncertainty in the derived distances is less than 4.9%. We compare our newly determined distances to the Cepheids in our sample with previously published distances to the same Cepheids with Hubble Space Telescope parallax measurements and distances based on the IR surface brightness method, Wesenheit functions, and the main-sequence fitting method. The systematic deviations in the distances determined here with respect to those of previous publications is less than 1-2%. We hence constructed Galactic mid-IR period-luminosity (PL) relations for classical Cepheids in the four Wide-Field Infrared Survey Explorer (WISE) bands (W1, W2, W3, and W4) and the four Spitzer Space Telescope IRAC bands ([3.6], [4.5], [5.8] and [8.0]). Based on our sample of hundreds of Cepheids, the WISE PL relations have been determined for the first time; their dispersion is approximately 0.10 mag. Using the currently most complete sample, our Spitzer PL relations represent a significant improvement in accuracy, especially in the [3.6] band which has the smallest dispersion (0.066 mag). In addition, the average mid-IR extinction curve for Cepheids has been obtained: A_W1/A_Ks=0.560, A_W2/A_Ks=0.479, A_W3/A_Ks=0.507, A_W4/A_Ks=0.406, A_[3.6]/A_Ks=0.481, A_[4.5]/A_Ks=0.469, A_[5.8]/A_Ks=0.427, and A_[8.0]/A_Ks=0.427 mag.
Gauss' Law for Gravity with Cylindrical Distribution of Gravitational Field Flux to Interpret Flat Rotation Curve and Baryonic Tully-Fisher Relation of Disk Galaxies
Wang, Te Chun
This report proposes an interpretation, by considering an integral Gauss’s law of gravity with anisotropic gravitational flux distribution, for the flat rotation curve as well as Baryonic Tully-Fisher relation of disk galaxies.It is pointed out that a flux distribution of cylindrical symmetry on the side wall of outer part of a disk galaxy may convert the inverse square radius dependence of the Newtonian gravitational field into a direct inverse dependence and the flat rotation curve can directly be derived under the circular motion approximation.It is also shown that the Baryonic Tully-Fisher relation can be proved valid if we assume the gravitational field flux distribution switches from spherical symmetry to cylindrical symmetry at a critical field strength near 10^(-10) m/s^2.Related consequences and implications of this an-isotropic gravitational field picture are discussed.
Studies of Global Solar Magnetic Field Patterns Using a Newly Digitized Archive
Webb, David
The McIntosh Archive consists of a set of hand-drawn solar Carrington maps created by Patrick McIntosh from 1964 to 2009. McIntosh used mainly H-alpha, He 10830Å and photospheric magnetic measurements from both ground-based and NASA satellite observations. With these he traced polarity inversion lines (PILs), filaments, sunspots and plage and, later, coronal holes, yielding a unique 45-year record of features associated with the large-scale organization of the solar magnetic field. We discuss our efforts to preserve and digitize this archive. The original hand-drawn maps have been scanned, a method for processing these scans into digital, searchable format has been developed, and a website and an archival repository at NOAA’s National Centers for Environmental Information (NCEI) has been created. Presently more than half of the final processed archive is complete, from SC 20 through to the start of SC 24, but with long gaps in SCs 20, 21 and 22. Here we present some examples of the maps and how the data base is being utilized for scientific applications. We compare the evolution of the areas and boundaries of CHs with other recent results, and we use the maps to track the global, SC-evolution of filaments, large-scale positive and negative polarity regions, PILs and sunspots.
The effect of carbon grain destruction on chemical structure of protoplanetary disks
Wei, Chen-En
The bulk composition of Earth is dramatically carbon poor compared to that of the interstellar medium, and this phenomenon extends to the asteroid belt. A gradient in the amounts of refractory carbon relative to silicate is shown in our solar system. To interpret the carbon deficit problem, we focus on two issues: (1) The carbon depletion gradient in the inner solar system. (2) Test the carbon grain destruction observationally.We assume two kinds of central stars T-tauri star and Herbig Ae star for the former and the latter issues, respectively. The results of the chemical models with and without the carbon grain destruction show significant differences especially near the midplane in the inner disk, where CO gas is abundant and not photodissociated. Carbon bearing species, e.g., HCN, become abundant while oxygen bearing species, e.g., H2O, becomes less abundant in the model with carbon grain destruction inside 2 au near the midplane in the T Tauri disk. Meanwhile, we calculate the solid carbon fraction relative to the total elemental abundance of carbon as a function of radius in the inner disk. In the model without carbon grain destruction, the ratio is about 75 % and doesn’t change very much at different radii since the majority of the carbon is locked in the refractory form. In the model with carbon grain destruction, the solid carbon fraction decreases in the inner disk as icy carbon-bearing species evaporate into gas inside their snowlines. However, in order to match the gradient in the solid carbon fraction in our solar system quantitatively, we will need a more comprehensive model.Furthermore, we consider HCN and its isotopologue, H13CN, as our candidate tracer of the carbon grain destruction, and make a prediction for the ALMA observations. The results indicate the difference in the HCN/H13CN line emitting regions as well as their intensity ratio are useful tracers of the carbon grain destruction.
Mars Probe Orbit Determination with Combined OCN and XNAV
WEI, Erhu
The precise autonomous navigation for deep space exploration by combination of multi-sourceobservation data is a key issue for probe control and scientific applications. In this paper, the performance of an integrated Optical Celestial Navigation (OCN) and X-ray Pulsars AutonomousNavigation (XNAV) system is investigated for the orbit of Mars Pathfinder. Firstly, OCN andXNAV single systems are realised by an Unscented Kalman Filter (UKF). Secondly, the integrated system is simulated with a Federated Kalman Filter (FKF), which can do the informationfusion of the two subsystems of UKF and inherits the advantages of each subsystem. Thirdly,the performance of our system is evaluated by analysing the relationship between observationerrors and navigation accuracy. The results of the simulation experiments show that the biasesbetween the nominal and our calculated orbit are within 5 km in all three axes under complexerror conditions. This accuracy is also better than current ground-based techniques.
The SAGA Survey for Satellites around Analogs of the Milky Way Galaxy: Satellite Properties
Weiner, Benjamin
Dwarf satellite populations are key to understanding the early stages of galaxy formation and the assembly of the stellar halo. However, models based on N-body simulations often predict more Milky Way satellites than observed, and predictions for satellite velocity dispersions (hence masses) also disagree with the data. Critically, most satellite studies are based on the Milky Way and M31 systems, and we do not know if these are representative or how satellite systems depend on formation history. The SAGA project aims to measure the distribution of satellite galaxies around a large number of systems analogous to the Milky Way, down to the luminosity of the Leo I dwarf galaxy (M_r< -12), to determine whether the MW and M31 are typical, and to measure the variance in satellite systems between different host galaxies. We have published complete, spectroscopically confirmed satellite galaxy luminosity functions for the satellite systems around eight Milky Way-like host galaxies, after taking spectra of thousands of candidate objects (Geha et al 2017). Surprisingly, the majority (26/27) of our satellites are star-forming, as compared to 2 of 5 star-forming Milky Way satellites in the same luminosity range. I will update the progress of the SAGA survey, including spectroscopy of satellite systems around more hosts, and discuss the properties of the satellites we find, in particular their star formation rates and metallicities. The SFRs and mass-metallicity relations may offer probes of the processes affecting satellites after accretion into the host halo.
Catch me IFU can: the hunt for tracers of the connection between spin and cosmic filaments in the kinematics of galaxies.
welker, charlotte
In this talk, I will use a synergy between hydrodynamic simulations and IFS data to review the deep connection between the build-up of galactic angular momentum and cosmic flows shaped by the cosmic web on Megaparsec scales, at different stages of galaxy evolution. Using the state-of-the-art cosmological hydrodynamic simulation Horizon-AGN and IFS mocks tailored to the SAMI IFS survey, I will in particular highlight the importance of the hydrodynamic vorticity and helicity fields and I will show how such flows inform the anisotropic accretion onto galaxies, leaving clear signatures in the kinematics of galaxies and in the scatter of scaling relations such the j*-M* relation, with specific features for central and satellite galaxies. Starting from our recent detection of spin alignments with cosmic filaments in SAMI, I will develop how the kinematics provided by IFS surveys can be used as a powerful tool to not only detect the connection between galactic angular momentum and cosmic filaments but also to infer information from the very cosmic flows that gave rise to the observed population of galaxies.
The MESAS Project – Stellar Atmospheres as a Source of Flux Bias in Debris Disks
White, Jacob
The planet formation process shapes the morphology and grain size distribution of circumstellar disks, encoding the formation history of a given system. Remnants of planet formation, such as comets and asteroids, collisionally evolve and can replenish the dust and small solids that would otherwise be cleared on short timescales. These grains are observed through their thermal emisison at submm to cm wavelengths.The spectrum of the mm/cm emission reveals details of the grain population. However, one confounding parameter in studying these grains around stars is the stars themselves. The emission from stars in the mm/cm is nontrivial and generally not well-constrained. I will present examples of debris systems (HD 141569 and Fomalhaut) studied by ALMA and the VLA, in which unconstrained stellar emission may be contributing to the observed flux densities. Such contamination in turn biases the inferred emission from the disk and the corresponding dust properties. In some cases, the behavior of the observed A/B stars can exhibit an emission profile that has similarities to that of the Sun's mm/cm emission, although the same processes are not thought to necessarily occur in the atmospheres of massive stars.To address the uncertainty in stellar emission at mm/cm wavelengths, we present ongoing radio observations (JCMT, SMA, VLA) of Sirius A, which is a bright, nearby star with no known debris. We seek to use this system to set an observationally determined standard for stellar atmosphere modeling and debris disk studies around A stars, as well as to take the first step toward characterizing potential intrinsic uncertainty in stellar emission at these wavelengths. This presentation highlights the effort to characterize stellar atmospheres through a project known as MESAS (Measuring the Emission of Stellar Atmospheres at Submillimeter/millimeter wavelengths) which is imperative to the success of current and future debris disk studies.
ISM and AGN Study in the Environment of Radio Galaxies using ALMA Observations
Wibowo, Ridlo
Powerful radio-AGN are mostly hosted by massive early-type galaxies (ETGs), which frequently reside in a dense concentration of galaxies. These galaxies are normally very poor in molecular gas. The gas is usually detected as a circumnuclear disk necessary to feed the accretion disk around the central supermassive black hole, generating the nuclear activity. Dust emission is mainly detected in the far-infrared (FIR) which is assumed to be thermal and originated from heating processes either by young massive stars or by the active galactic nuclei (AGN). Different mechanisms were proposed to explain the origin of these emissions but their respective contributions are not yet conclusive. ETGs have shown no independent evidence of high star formation rates, suggesting that either the older stars or the AGN are responsible for much of the FIR emission. One also argued that in ETGs the gas is unrelated to the stellar populations and favor an external origin of the molecular gas. It is then crucial to study the ISM properties of the host galaxy and also the galaxies around it, to be able to understand the creation, evolution, and feedback of the radio sources with their environment. In this study, we examine some of the most powerful radio galaxies (RGs) observed by the Atacama Large Millimeter/submillimeter Array (ALMA), which offers unprecedented sensitivity and high spatial resolution, to investigate particularly the environment of RGs. We exploit the data from the calibration observations performed for each science project of ALMA. By combining the accumulated compatible data and careful analysis of the noise and possible bias, we must be able to obtain deep submillimeter images with a sufficiently low noise level at tens µJy. We measure the thermal and synchrotron emission in the central RGs and in the field, to study the distribution of the ISM and the interplay between the central AGN and its environment. We also detect several absorption lines towards these RGs.
ATLASGAL - Kinematic distances and the dense gas mass distribution of the inner Galaxy
Wienen, Marion
High-mass stars and clusters form in the densest regions within giant molecular clouds. The initial conditions of the process are still little understood. Further progress requires to study objects in these early evolutionary stages, which are so cold that they can only be probed at far-infrared and longer wavelengths. The APEX Telescope Large Area Survey of the Galaxy, ATLASGAL, the first unbiased dust continuum survey of the whole inner Galactic plane at 870 micron, has therefore been carried out. It provides a statistically representative sample of molecular clumps at various stages of high-mass star formation.Molecular line observations are an essential tool to obtain important parameters such as temperatures, linewidths and distances. Especially the high density tracer ammonia is an excellent probe of massive clumps with low temperatures. Using the Effelsberg and Parkes telescope we thus followed up a large sample of ATLASGAL sources in the (1,1) to (3,3) ammonia inversion transitions. We derive a large range of linewidths from 1 to 7 km/s and of rotational temperatures between 10 and 25 K. The determination of masses and sizes requires the derivation of distances using the measured ammonia velocities and further velocities from the literature. We identify about 700 complexes consisting of about 3500 ATLASGAL sources based on spatial and kinematic information. From their radial velocities and a rotation curve model we determine their distances. For complexes within the solar circle two distances are possible and HI data are used to resolve these ambiguities. A correlation between the source number as a function of galactocentric radius and the position of the spiral arms reveals a link between them. Most clumps exceed the mass-size threshold for massive star formation and are likely to be unstable to gravitational collapse. Our results show that most ATLASGAL sources are already forming massive stars or have the potential to form high-mass stars in the future.
Observational signposts of shock-induced magnetic field compression in star-forming environments
Wiesemeyer, Helmut
This contribution summarizes the observational signposts for the shock compression of magnetic fields in star-forming environments. The evidence stems from the polarimetry of cloud-cloud collisions, and of PDRs exposed to the UV radiation and winds from young stellar clusters. Besides their dynamical role, compressed magnetic fields increase the cosmic ray flux above the Galactic average. The trapped cosmic ray particles contribute to the heating budget of the shocked gas. This mechanism is assumed to account for the anomalously high excitation in the Orion bar, a scenario which is also suggested by the submm dust polarization presented in this contribution. The observational findings are compared with studies of shock-compressed molecular gas exposed to expanding supernova remnants.
Detection of Longitudinal Albedo and Metallicity Variations of Asteroids with Ground-Based, Part-Per-Million Polarimetry
Wiktorowicz, Sloane
The linear polarization and albedo of rocky solar system bodies is anticorrelated: dark surfaces, dominated by single scattering, are strongly polarized, but multiple scattering in bright surfaces randomizes the electric field orientation and reduces polarization. As an asteroid rotates, both shape changes and surface albedo variations affect reflected light flux, causing difficulty in the identification of albedo variations. Polarimetry, however, is insensitive to shape changes: as total flux varies with instantaneous cross-sectional area, fractional polarization does not. Thus, rotational variability in linear polarization is a hallmark of albedo inhomogeneity, and it cannot be identified with photometry alone._x005F Until now, polarimeters have only discovered high significance rotational variation of linear polarization for (4) Vesta. We report on Lick 3-m observations of Main Belt asteroids with the POLISH2 polarimeter, which utilizes photoelastic modulators instead of a waveplate. We have not only confirmed rotational variations in (4) Vesta, but we have also discovered variations in (1) Ceres and (7) Iris. The amplitude of variations for both (4) Vesta and (7) Iris are stronger than those of (1) Ceres due to the latter’s relatively homogeneous surface._x005F Circular polarization, which may originate from multiple scattering or from the phase retardance introduced by a metalliferous surface, has been observed in nearly all Solar System bodies except for asteroids. POLISH2 simultaneously measures linear and circular polarization, and we report the discovery of non-zero circular polarization from both (7) Iris and the metallic (216) Kleopatra. This is in stark contrast to the non-detection of time-averaged circular polarization from the differentiated (1) Ceres and (4) Vesta. Therefore, optical circular polarization may provide a new way to identify metalliferous asteroidal surfaces.
Resolving the Missing AGN Problem with Radio Selection
Wilkes, Belinda
The complex nuclear structures of active galactic nuclei (AGN)lead to strong selection effects in most wavebands, including the X-ray.Highly obscured AGN are hard to find, and identify. Estimating theirnumbers, a function of luminosity and redshift, remains a major questboth for AGN science, and in understanding the level of accretionpower particularly in the early Universe.Multi-wavelength observations of the low-frequency, radio-selected 3CR luminousAGN sample (z>0.5) largely avoid selection biases, revealing the obscured AGN,and probing both their intrinsic, and orientation-dependent properties.Chandra, Spitzer, Herschel and multi-wavelength observations confirm thatthe FIR (> ~40um) does not depend on orientation and that ~half the sampleis significantly obscured with ~a quarter being Compton thick. This is alarger fraction than typically estimated for optically- or X-ray-selected,high-luminosity samples. Once the primary X-ray power-law is obscured, AGNX-ray spectra are complex, and detecting and estimating X-ray obscurationlevels becomes highly uncertain. This is particularly true for sources closeto the flux limit. The loss or miss-classification of obscured AGN in surveysalso results in large (*10-1000) uncertainties on their intrinsic luminosities.This may explain discrepant obscured fractions reported for variousoptical- and X-ray-samples, and may also affect the shape of derived luminosityfunctions. The use of independent measures of the AGN power, suchas the low-frequency radio, or [OIII] emission line luminosity, both used here, help tocounteract such problems, and so to probe the intrinsic AGN properties. Other properties which effect a radio galaxy's spectral energy distribution even when limiting the redshift range include: gravitational lensing (e.g. 3C220.3), and merger history.
K-Type Supergiants in the Large Magellanic Cloud
Wing, Robert
The brightest stars of the Large Magellanic Cloud are supergiants with magnitudes in the V = 11-14 range and a very uneven distribution in color: there are large numbers of both very blue (types O, B, and A) and very red (type M) supergiants, but only a few confirmed supergiants of intermediate types (F, G, K). The lack of K supergiants in the Large Cloud is particularly noteworthy because the Small Magellanic Cloud contains large numbers of them. Are K-type supergiants really absent from the LMC, or have they simply been missed by the survey techniques employed to date? Near-infrared objective-prism surveys by Westerlund and Blanco identified several hundred M supergiants on the basis of their TiO bands but had no way of identifying K stars. On the other hand, the Case survey by Sanduleak and Philip used blue objective-prism plates of such low dispersion that no spectal features (not even TiO) could be seen, but they catalogued several hundred "suspected late-type supergiants" on the basis of their red slope in the blue region and an apparent magnitude in the right range to be supergiant LMC members. Most of the Case sample had not been picked up in the Westerlund or Blanco surveys and must have had types earlier than M2. Does the Case sample include the "missing" K-type supergiants, or are they foreground stars of lower luminosity? To settle this question, the writer has been obtaining two-dimensional spectral classifications for the Case suspected supergiants which were not already known to be M stars - a total of 433 targets. The observations consist of narrow-band photometry on a 5-color system that measures bands of TiO and CN in the near infrared. Although the follow-up observations are not yet complete, nearly 100 stars have been confirmed as K stars of luminosity class I, while many others are M stars of types M0 and M1 which escaped detection on the TiO-based infrared surveys. Only a small minority are found to be foreground stars of lower luminosity.
Atmospheric Mass Loss due to XUV radiation from Sgr A* in Planetary Lifetime
Wislocka, Agata
In recent years, there has been a noticeable rise in interest in the damage caused to planetary atmospheres as a result of exposure to XUV radiation (capable of driving hydrodynamic winds) emitted by super massive black holes (SMBH) as they accrete matter. These studies have mainly concentrated on the theoretical mass loss of Earth-like planets as a function of distance from our own SMBH, Sgr A*, located at the centre of the Milky Way Galaxy. The focus of our work is the quantification of total mass loss as a function of planet distance, bulk density and age experienced by all Earth-like planets discovered to date, as well as the 16 Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) exoplanets known to reside in the bulge of the Milky Way Galaxy. Based on the current body of evidence, Sgr A* went through an active phase approximately 8 Gyrs ago. This would indicate a more severe loss of atmosphere for some planets in our sample, with ages of host stars exceeding 8 Gyrs. For planets orbiting stars younger than 8 Gyrs, we find the mass loss to be negligible under the assumption that Sgr A*’s luminosity has remained constant, at its current value LSgr A* = 10-8.5 LEdd since the end of its active galactic nucleus (AGN) stage.
A carbon star sheds its skin
Wittkowski, Markus
While the basics of this mass-loss process from AGB stars are understood, we are still investigating how it begins near the surface of the star. Here, we present recent near-IR H-band aperture synthesis images of the carbon AGB star R Sculptoris with an angular resolution of 2.5 mas obtained with the PIONIER instrument at the Very Large Telescope Interferometer. The data show a stellar disk of diameter ~9 mas exhibiting a complex substructure including one dominant bright spot. It has a peak intensity of 40% to 60% above the average intensity of stellar disk. This contrast is significantly higher than expected for photospheric convection, and we also expect the photosphere to be obscured by molecular and dusty layers of the atmosphere. The companion of R Sculptoris, as detected through previous ALMA images, is too far away to cause this complex substructure close to the surface. We interpret the complex structure as caused by giant convection cells, resulting in large-scale shock fronts, and their effects on clumpy molecule and dust formation seen against the photosphere at distances of 2-3 stellar radii. We obtained a Rosseland radius of 355 ± 55 Rsun, an effective temperature of 2640 ± 80 K, and a luminosity of log L/Lsun = 3.74 ± 0.18. These parameters match evolutionary tracks of initial mass 1.5 ± 0.5 Msun and current mass 1.3 ± 0.7 Msun. These constraints are important for the modelling of the mass loss history of the star and the interpretation of the spiral structure seen by ALMA at larger scales. Our visibility data are best fit by a model without a wind, which may point to problems with the wind models at low mass-loss rates._x005F I will also give an outlook to similar aperture synthesis imaging of red supergiants, including V766 Ven with its in-contact or common-envelope companion. I will discuss ongoing work to compare results from aperture synthesis imaging to 3D models.
Infrared Variability of Young Stars
Wolk, Scott
One of the recent changes to our understanding of young stars is the realization of how dynamic these systems are in the infrared. I present time series data from the CFHT and Spitzer observatories. We have monitored thousands of young stars down to J˜ 20 using the WFCAM and [4.5] ~ 13 using Spitzer/IRAC. Most of the young stars with disks are significantly variable. By studying variability in young stellar objects (YSOs) in the H - K, K color-magnitude diagram, we are able to distinguish among physical mechanisms of variability. Many variables show color behavior indicating either dust-extinction or disk/accretion charges. At the Spitzer wavelengths, more than 80% of the Class I, flat spectrum, and Class II sources are found to vary. The amplitude of the variability is larger in more embedded YSOs. Most of the Class I/II objects exhibit redder colors in a fainter state, which is compatible with time-variable extinction. A few become bluer when fainter, which may be explained by significant changes in the structure of the inner disk.
Touching the Stars: Lessons learned in 3D printing parts of the high energy Universe
Wolk, Nancy
Scientists, amateur astronomers, and communicators have been using Chandra's two-dimensional images, along with Chandra videos and podcasts, as an aid in discussing X-ray astronomy with non-experts since Chandra's launch in 1999. With new research techniques, however, we have begun mapping X-ray data (along with other multiwavelength data) of astronomical objects in three dimesions. Holding a 3D print can be an invaluable tool to learn about otherwise unreachable phenomena and data for people of all ages and of varying interests and abilities. In this talk, we will detail our lessons learned in 3D printing, from best practices for reaching blind and visually impaired audiences, to technical advice on print resolution and size, to our new adventures in powder-based printing in full color.
TIGvival -- High-resolution spectroscopic monitoring of long-period variables using TIGRE
Wolter, Uwe
Since 2013, we have been carrying out a longterm spectroscopic monitoring campaign of long-period variables (LPV). We use the TIGRE 1.2 meter robotic telescope, located in La Luz, central Mexico. We obtain low-noise, high-resolution spectra covering the whole optical regime from 3800 Å to 8800 Å with a spectral resolution of 20000.Our target sample currently consists of 7 LPVs with periods between 90 and 400 days, Mira is one of them. The targets were chosen to represent different chemical and variability properties. To date, we have collected more than 300 spectra that evenly sample the cycles of our targets, as far as ground-based observations allow.Here, we present an overview of our dataset and preliminary results. We demonstrate the data quality and illustrate TIGvival's potential to help gauging future 3D simulations. The acronym TIGvival (TIGRE vigila variables de largo periodo a largo plazo = TIGRE long-term monitoring of LPVs) is meant to illustrate the long-term nature of our project: we plan to continue TIGvival for at least ten more years.
Radio Galaxy Zoo: mapping AGN evolution via radio galaxy morphologies
Wong, O. Ivy
Visual inspection remains the primary method for extended radio morphology classification. Statistically-significant sample sizes of radio morphologies are required to further our understanding of radio AGN evolution. Radio Galaxy Zoo is an online citizen science project that enlists the help of the public to cross-match radio sources from the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia Telescope Large Area Survey (ATLAS) surveys, to host galaxies observed in the infrared images from the Wide-field Infrared Survey Explorer (WISE) and the Spitzer Space Telescope at 3.6 microns. The project is currently 75% complete. I will present a summary of recent results and the upcoming data release of ~75,000 radio sources. Despite using decades-old archival datasets, we have made new discoveries of rare classes of radio AGN that are useful for constraining the physical processes associated with radio jet formation and evolution (Banfield et al 2016, Kapińska et al 2017). Radio Galaxy Zoo is also collaborating with several international machine learning teams in the use of our catalogues as training sets for developing advanced deep learning algorithms that will benefit the upcoming pre-SKA surveys from which we expect tens of millions of radio sources._x005F (References: Banfield, Wong et al 2015 MNRAS, 453, 2326; Banfield et al 2016 MNRAS, 460, 2376; Contigiani et al 2017 MNRAS, 472, 636; Kapińska et al 2017 AJ, 154, 253; Lukic et al 2018, in press MNRAS)
The location of the gamma-ray emitting region in blazars
Wu, Qingwen
The core-shift effect can be resoved at pc-scale for many blazars with radio VLBI observations. The equapartition magnetic field distribution can be derived along the jet. We model the simultaneous or quasi-simultaneous multi-band spectral energy distributions (SEDs) for a sample of blazars with a one-zone leptonic model and Markov chain Monte Carlo technique, where the core shift effects of these sources have been measured. Assuming the magnetic field strength in the γ-ray emitting region as constrained from the SED fitting follows the magnetic field distribution as derived from the radio core-shift measurements, we then can derive the location of the gamma-ray emitting region for these blazars. We find that the gamma-ray emitting region roughly locate at 2*104 Rs, or ~ 10 RBLR(RBLR is the size of broad line region), which suggest that the most of the jet energy may dissipated at outside of BLR and roughly within the torus. The possible jet physics in nearby galaxies (e.g., M 87) will also be discussed.
PERFORMANCE AND STATUS OF GRM ONBOARD SVOM
Wu, Bobing
SVOM (Space-based multiband astronomical Variable Objects Monitor) is a Chinese-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) from the visible band to the gamma ray band, which is expected to be launched at the year of 2021. We make use of the mass modelling technique to estimate the background and the expected performace of GRM (Gamma Ray Monitor) onboard SVOM. The progress and stastus of GRM are also introduced.
Emission-line diagnostics of nearby HII regions including interacting binary populations
Xiao, Lin
The evolution of binary-star systems vary from that of single stars as they can interact with their companions. This leads to mass loss, mass gain, or stellar mergers. We now know that most massive stars are binary stars interact with a binary companion (Sana et al., 2012, 2014). Therefore, in observed stellar populations their properties will be largely determined by past and ongoing binary interactions. We modelled nebular emission from young HII regions in great detail by combining the Binary Population and Spectral Synthesis (BPASS) code with the photoionization code cloudy (Ferland et al., 1998, 2013). We have compared these models to two different samples of observed HII region samples. We found that binary interactions must be considered as they can provide harder ionizing photons at later population ages beyond 10 Myr. These harder photons arise due to the production of less-massive helium stars which are not possible from single-star populations. These are the stars that go on to explode as type Ibc CCSNe. The existence of stellar populations with these helium stars means that we must reexamine the emission line diagnostics of HII regions. We currently have not include the accretion luminosity from X-ray binaries in our model populations since accretion physics is beyond the scope of our models. This can be significant at lower metallicities as the typical black hole mass in our populations increases; therefore our predictions for ionizing fluxes should be considered as a lower bound without this included. While accretion events are short lived, they are also extremely luminous and so may have an appreciable effect on the integrated spectrum of a stellar population in any given time bin. We would thus expect that once an accurate model of accretion onto compact remnants is included there will be an extra source of hard ionizing radiation within our models.
Rediscover the cultural relics of Beijing Ancient Observatory
xiao, jun
Last year we have a project to collect the data of the cultural relics in Beijing Ancient Observatory.This project consists of three parts: three-dimensional scanning modeling, traditional rubbing (Stone Rubbing) and two-dimensional high-definition heritage photography, which classifies the overall shape, components, astronomical information, decorative details and other elements of the cultural relics, targeted for three-dimensional data acquisition processing, rubbing and two-dimensional high-precision and multi-angle data collection and processing.In this Project , all the ancient instruments are 2 meters higher and too large to High precision 3D scan. Hand-held scanners & High-Precision Structured-light scanners were applied to acquire geometry informations to fulfill relics document requirement .Meanwhile, for the requirement of High-fedility color information preservation, this Project have also used IBMR(Image-Based Modeling and Rendering) technology to acquire textures. Color information from Single Lens Reflex camera, geometry information from structured-light scanner, the 3D scanner have assured the precision of geometry, color informations are transferred with baking technology. The digital document is focused on high-fedility, high-precision from beginning to end.5 months, 8 Main instrument & More than 20 relics have been successfully scanned and digitalized with advanced computer graphic technologies. Models are finally processed as Unity 3D scenes to display and basic interaction.Based on the results of the data collections of Ancient Observatory cultural relics by Beijing's municipal financial projects, we could rediscover the cultural meaning of astronomy instruments in ancient observatory, and understand the Chinese traditional concept of harmony between human and nature deeply. This will strengthen the depth and breadth of management, research, and scientific popularization of the collections in Beijing Ancient Observatory.
Evidence for the effective magnetic field decay of radio pulsars from the statistical properties of their spin frequency's second derivatives
Xie, Yi
We report a new evidence of effective magnetic field decay of isolated neutron stars, from the analysis of the timing data of a large sample of radio pulsars \citep{2010MNRAS.402.1027H}. There is an approximate symmetry between the frequency's second derivatives of the pulsar spins with positive and negative signs in this large sample, since they are dominated by the effects of quasi-periodic structures in timing noise. We find that the approximate symmetry has in fact been statistically reduced, which is caused by the long-term monotonic decay of the effective magnetic fields of these pulsars on a timescale around $4-8~{\rm Myr}$. The determination of the timescale would not be significantly effected by any specific theories of the magnetic field decay of isolated neutron stars.
GECAM: a dedicated mission to monitor gravitational wave electromagnetic counterpart in X/gamma-ray
Xiong, Shaolin
Multi-messenger observation of the first binary neutron star merger both in gravitational wave (GW) and electromagnetic wave (EM), GW170817 and EM170817, heralded a revolution era of astronomy. During the observation campaign of GW170817, the X/gamma-ray electromagnetic counterpart, named as GRB1701817A, has played a very important role both in the joint observation and in the physics research related to the GW/EM source. This GRB, however, features a short time delay (~1.7 s) with respect to GW signal, short duration (~2 s) and weak and soft in spectrum, making it very difficult to catch using the existing GRB detectors. Here we report a dedicated mission called Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor or GECAM. It consists of two identical small satellites (<150 kg) and each GECAM satellite employs 25 gamma-ray detectors made with LaBr3 scintillator read out by SiPM and 8 charged particle detectors. GECAM highlights an instantaneous Field of View (FOV) of 100% all-sky, localization accuracy of a few degrees, very low energy limit (down to 6 keV) and wide energy band (up to 5 MeV), as well as high sensitivity (~2E-8 erg/cm2/s), making GECAM much easier to detect and localize GRB170817A-like GW EM events. After the expected launch in 2020, GECAM shall play a critical role in monitoring high energy counterpart for GW sources and other transients, such as Fast Radio Bursts and High Energy Neutrinos.
SPIN EVOLUTION AND THE BIMODAL DISTRIBUTION OF BE/X-RAY PULSARS
Xu, Xiao-Tian
Recent years, Knigge et al. (2011) reported that there are two populations of Be/X-ray pulsars (BeXPs), which arerelated to different accretion modes (Cheng et al. 2014). In this work, we investigate the spin evolution of BeXPs bytaking into account dipole radiation, the outburst phase and the quiescent phase of the type I outburst, advection-dominated accretion flow, disk wind, and the type II outburst. We demonstrate that the type II outburst is capableof generating the population with spin period P < 40s and the observed BeXPs are in or near the spin equilibriumstate. We adopt the Markov chain Monte Carlo method to fit our model to the observed distribution, which is well reproduced by our model with reasonable parameters. Our results implies that the outburst rate and duration of the type II outburst potentially depends on the orbital parameters, and, from the perspective of spin evolution, magnetars may exist in the population with P ~ 1000 s.
Gas kinematics in radio-AGN
Xu, Dawei
Narrow-line Seyfert 1 galaxies are a sub-class of active galactic nuclei (AGN) with low-mass black holes and high accretion rates. Only a small fraction of them is radio-loud. Our analysis of SDSS spectroscopy of these galaxies has shown that their emission lines are highly shifted. If interpreted as outflow, these imply radial velocities exceeding up to 2000 km/s in the highest-ionization gas. We further find a strong ionization stratification, and a lack of zero-velocity high-ionization gas, implying a large NLR fraction is affected by the outflow. All galaxies of the mini-sample have high L/LEdd and also possess strong radio jets. Therefore, both mechanisms are potential drivers of the outflow, i.e., large-scale winds and jet-NLR interactions. Based on predictions from hydrodynamic simulations, the high observed outflow velocities can be understood, if the AGN are in an early stage of their evolution, not much older than 1 Myr.
On the origin of density filaments in the magnetized and turbulent interstellar medium
Xu, Siyao
This study is motivated by recent observations on ubiquitous interstellar density filaments and guided by modern theories of compressible magnetohydrodynamic (MHD) turbulence. As the fundamental dynamics of compressible MHD turbulence, perpendicular turbulent mixing entails elongated density structures aligned with the local magnetic field, accounting for low-density parallel filaments seen in both diffuse media and diffuse regions of molecular clouds (MCs), e.g., HI filaments, striations and subfilaments in MCs. Differently, in highly supersonic MHD turbulence in MCs, shocks driven by supersonic flows result in dense filaments. Simple shock physics involving magnetic effects can well explain the preference on observing dense filaments perpendicular to magnetic fields in MCs as shown by Planck, which set up the necessary condition for the self-gravity to take over the gas dynamics and initiate the subsequent star formation.
X-ray Investigation on the Statistical Properties of Cataclysmic Variables in the Galactic Bulge
xu, xiaojie
The Galactic Bulge X-ray Emission (GBXE) is a composition of weak point sources, which were suggested to be catalysmic variables (CVs). Using archival Suzaku observations on the GBXE and on CVs in solar neighborhood, we put constraints on the CV population in the GBXE by comparing the EW and flux ratios of Fe emission lines. The main findings are: A) non-magnetic CVs, instead of magnetic ones, dominate the GBXE;B) The mean WD mass in CVs in GBXE is ~0.8 solar mass, which is consistent with that of CVs in solar vicinity.
Extremely Rapid X-Ray Flares of TeV Blazars in the RXTE Era
Xue, Yongquan
Rapid flares from blazars in very high-energy (VHE) gamma-rays challenge the common understanding of jets of active galactic nuclei (AGNs). The same population of ultra-relativistic electrons is often thought to be responsible for both X-ray and VHE emission. We thus systematically searched for X-ray flares at sub-hour timescales of TeV blazars in the entire Rossi X-ray Timing Explorer archival database. We found rapid flares from PKS 2005-489 and S5 0716+714, and a candidate rapid flare from 1ES 1101-232. In particular, the characteristic rise timescale of PKS 2005-489 is less than half a minute, which, to our knowledge, is the shortest among known AGN flares at any wavelengths. The timescales of these rapid flares indicate that the size of the central supermassive black hole is not a hard lower limit on the physical size of the emission region of the flare. PKS 2005-489 shows possible hard lags in its flare, which could be attributed to particle acceleration (injection); its flaring component has the hardest spectrum when it first appears. For all flares, the flaring components show similar hard spectra with Gamma = 1.7-1.9, and we estimate the magnetic field strength B~0.1-1.0 G by assuming synchrotron cooling. These flares could be caused by inhomogeneity of the jets. Models that can only produce rapid gamma-ray flares but little synchrotron activity are less favorable.
The ISM properties of low-mass galaxies with extremely strong emission lines at z=0.3-0.8 discovered with Subaru/HSC
Yabe, Kiyoto
Revealing the nature of low-mass galaxies with strong emission lines is of importance to understand the early stage of galaxy formation and evolution. The detailed studies at high redshift, however, are not easy because of various observational limitations. Thus, it is important to examine similar galaxies at lower redshift in details. Thanks to its deep and wide imaging data, we are conducting a survey to search for strong emission line galaxies by using Subaru Hyper Suprime-Cam (HSC). We select candidates of strong emission line galaxies at up to z~0.8 with excesses of broad-band filters. The selected galaxies correspond to high redshift version of Green Pea galaxies in the SDSS, which are thought to be similar to galaxies in the early Universe. Our spectroscopic follow-up for the candidates is currently ongoing. In a previous observation, we confirmed the spectroscopic redshift of 19 galaxies at z=0.35-0.83 using Gemini/GMOS-S. From 4 galaxies, we detected very strong [OIII]5007 emission with the rest-frame equivalent width of > 1000A and other multiple emission lines including weak [OIII]4363 with high significance. The stellar mass ranges from ~10^7 to ~10^9 Msun and the SFR ranges from ~0.1 to ~1000 Msun / yr. According to the stellar mass and [OIII]5007/Hb ratio, the contribution from active galactic nuclei (AGNs) seems to be low. The [OIII]5007/[OII]3727 emission line ratio ranges from ~3 to ~10, which is comparable to that of the SDSS Green Pea galaxies and Lya emitters (LAEs) at z=2-4, indicating extreme ionization states. The resulting oxygen abundance based on the “direct” method using [OIII]4363 is 12+log(O/H)<8.0. One of the sample shows very low oxygen abundance of 12+log(O/H)~7.3, which is comparable to extremely metal poor galaxies in the local Universe. In this presentation, we give an overview of our project and discuss the possible origin of these galaxies with low metallicity and high ionization state.
Highlights of NOC Ethiopia's Major Activities
Yacob, Alemiye Mamo
In Ethiopia the pace of Astronomy and Space science development is improved from time to time. The Currently established Ethiopian Space Science and Technology Institute (ESSTI) under the Ministry of Science and Technology (MOST) along with Ethiopian Space Science Society (ESSS) are the two main actors that play a great role in development of Astronomy and Space Science in Ethiopia. NOC Ethiopia is therefore playing a key role in coordinating and accelerating the efforts made by such an organization and other educational bodies in the country in communicating Astronomy and Space science at large to the public. The poster is therefore depicts the major outreach activities that are performed in the country.
Models of binaries containing giants
Yakut, Kadri
In this study, we modelled 60 relatively long-period binaries with giant component(s) using their observed physical parameters. Most of the selected systems consisting of a cool, evolved star and a hotter less evolved component. We compared our model results with the observed mass, radius and temperature values for each components in the systems. Theoretical models include core convective overshooting, mass-loss, and tidal friction. We found out that some of the systems have overevolved secondary. Explanation being that the primary component is the merged remnant of a former short-period sub-binary in a former triple system. We will give the detail of study in this presentation.
X-Ray Binaries as Gravitational Wave Sources
Yakut, Kadri
We catalogued well-determined physical parameters of low-mass X-ray binary (LMXB) and high mass X-ray binary (HMXB) systems. Angular momentum loss (AML) mechanism via gravitational radiation (GR) and magnetized stellar winds (MSW) are calculated for some LMXB and HMXB systems. Gravitational wave amplitudes (h) of the relatively short period X-ray binary systems have been compared with the limit of the Laser Interferometer Space Antenna (LISA).
Astrometric Data Reduction (JASMINE case)
Yamada, Yoshiyuki
Astrometric data reduction is very tough work with complex system identification. We Japanese team plan Nano-JASMINE and Small-JASMINE missions. Observational strategyof Nano-JASMINE is very similar to that of Gaia, and data reduction software development is being done as collaboration with Gaia AGIS team. On the other hand, Small-JASMINE will observe bulge region with step-stare strategy. We are now start software develpment. International Collaboration(s) will be also planned.Astrometric Data Reduction will be done by iterative least square fit, and need to very large matrix inversion. Stellar motion of primary stars are simple, but calibration model will become complex. Matrix inversion part will be hard computational work but relatively simple as a software enginnering problem. But matrix generation part will need to be flexible because the systems model will change during the mission. It may be challenge in software development. We will discuss how the software development will be done in JASMINE case, and which point can be common with other astrometric missions like Theia.
Astronomical Activity in Japan (NOC report)
Yamaoka, Hitoshi
Japanese people have been engaged the astronomical activity very well. There are more than 300 planetariums, and also are many public observatoies with >1.0m aperture telescope. These facilities are very good place to meet together with astronomy fans. Every research intstitutes make efforts in educating and popularizing astronomy and space sciences. Two domestic monthly commercial-based astronomy magazines are published, as well as the other science magazines written in Japanese. Under such situation, the role of NOC would be concentrate to connect them with the international activities. NameExoWorld contest was the first such case. Name proposals from Japan were numerous, and we got 4 official names which were greatest number in the world. But it needed to get over the language vareer. With Japanese language, we set up the instruction web page for every procedures. wrote many articles, made many lectures and so on. However, we got a small number of vote at that time. We discuss the reason why we could not reach people who could vote, and the strategy for the next chance.
Optically-faint radio galaxies found by Subaru HSC-SSP and FIRST catalogs
Yamashita, Takuji
We will present statistical optical and radio properties of optically-faint radio galaxies found by an on-going project, a Wide and Deep Exploration of Radio Galaxies with the Subaru HSC (WERGS). Radio galaxies are bright sources in radio wavelength, involving powerful radio-jets, which could give a so-called feedback effect on host galaxies. Because the host galaxies are thought to be typically massive, radio galaxies are important for understanding the evolution of massive galaxies and also the nuclear supermassive black hole. However, while there exist wide and deep radio surveys, compatible wide optical surveys have been not enough deep. The SDSS has identified optical counterparts of only ~30 % among the FIRST radio sources due to the faintness in optical (i < 21 mag).In order to overcome this situation, we carried out the search for optically-faint radio galaxies by combing both the Subaru HSC-SSP catalog and the FRIST catalog (Yamashita et al. 2018 in prep.). The HSC-SSP compiles faint sources down to i = 27 mag. As a result, we identified ~3,600 radio galaxies in the field of 156 square degree. The number of the matches is equivalent to ~50 % of FIRST sources in the search field. In particular, we found a large number of radio galaxies with large radio-loudness (log R > 4) at an optically-faint regime (i > 21 mag). These optically-faint radio galaxies are mostly located at photometric redshifts z_ph > 1. The results may infer high-z optically-faint radio galaxies have low accretion rate or obscured nuclei. The optical color of optically-bright HSC-FIRST radio galaxies at z_ph ~< 1is consistent with that of passive galaxies. Meanwhile, the optically-faint radio galaxies at z_ph > 1 show blue color of g-z < 2, which is not consistent with that of passive galaxies but can be explained by predominant young stellar populations. The optically-faint radio galaxy sample found by Subaru HSC-SSP and FIRST may include “evolving” radio galaxies that are star-forming.
On the nature of the X-ray outbursts in Be/X-ray binaries
Yan, Jingzhi
Be/X-ray binaries are a major subclass of high mass X-ray binaries. Two different X-ray outbursts are displayed in the X-ray lightcurves of such systems. It is general believed that the X-ray outbursts are connected with the neutron star periastron passage of the circumstellar disk around the Be star. The optical emission of the Be star should be very important to understand the X-ray emission of the compact object. We have monitored several Be/X-ray binaries photometrically and spectroscopically in optical. The relationship between the optical emission and X-ray activities are found, which is very useful to explain the X-ray outbursts in Be/X-ray binaries.
The History of Solar Radio Astronomy in China
Yan, Yihua
The Solar Radio Research in China started in 1950s when the solar total eclipse event occured in Hainan Island. Since then the solar radio observation at single frequency had been conducted. Later the solar radio antennas at several sites were set up and campaigns were organized during 1980s. In later 1990s the Chinese Broadband Fast Dynamic Spectrometers were developed in Beijing, Nanjing and kunming, and solar radio fine structures have beeb observed. In recent years a spectral radioheliograph has been developed in Mingantu, Inner Mongolia of China, i.e., MUSER -- Mingantu Spectral Radioheliograph with two arrays of 40 4.5m antennas covering 400MHz-2GHz and 60 2m antennas covering 2-15 GHz, which will play an important role in solar physics and space weather studies. Mingantu Observing Station has been constructed and future plan will be introduced as well.
Direct infall signatures and complex organic molecules toward an isolated embedded protostar BHR71
Yang, Yao-Lun
Star formation processes such as infall, accretion, and outflows increase the complexity of molecules, allowing us to use those molecules to probe the physical environments where stars form. The most deeply embedded protostars present particularly rich spectra of molecules due to their dense envelope and active infall and outflows, making them best probed by molecular spectroscopy. Stars form via the infall of mass from a core, but direct evidence for such infall has been elusive. The most direct probe of infall is redshifted absorption against the central continuum source, which is best shown in dense gas tracers, such as HCO+ and HCN. Our ALMA observations of these two molecules show such redshifted absorption toward an isolated core, BHR71. Both lines show a similar redshifted absorption profile, but the HCN line has a wider (9 km/s compared to 5 km/s) line width, suggesting that it traces faster infalling gas closer to the central protostar. We model the line profiles with 1D and 3D radiative transfer calculations to further constrain the physical properties of the collapsing envelope. We also found emissions of complex organic molecules around 345 GHz. BHR71 shows a similar suite of lines compared to another isolated core, B335, which only has 10% of the luminosity of BHR71 but is at a similar evolutionary stage. We found that complex organic molecules emit from a compact region centered on the continuum source, which is barely resolved with a beam of 0.27", corresponding to ~50 AU. We identify the origins of this emission and constrain the excitation environment to compare with current paradigms of the structure of inner envelope and disks. We investigate the physical environment in the inner 50 AU via emission of complex organic molecules; combined with the redshifted absorption we can follow material from the envelope to the central protostar.
Clear anti-correlation between X-ray luminosity and pulsed fraction in the Small Magellanic Cloud pulsar SXP 1323
Yang, Jun
We report the anti-correlation between pulsed fraction (PF) and luminosity of the X-ray pulsar SXP 1323, found for the first time in a luminosity range \boldmath{$10^{35}$}--$10^{37}$ erg s$^{-1}$ from observations spanning 15 years. The phenomenon of a decrease in X-ray PF when the source flux increases has been observed in our pipeline analysis of other X-ray pulsars in the Small Magellanic Cloud (SMC). It is expected that the luminosity under a certain value decreases as the PF decreases due to the propeller effect. Above the propeller region, an anti-correlation between the PF and flux might occur either as a result of an increase in the un-pulsed component of the total emission or a decrease of the pulsed component. Additional modes of accretion may also be possible, such as spherical accretion and a change in emission geometry. At higher mass accretion rates, the accretion disk could also extend closer to the neutron star (NS) surface, where a reduced inner radius leads to hotter inner disk emission. We will discuss the implication of these modes and the beam configuration.
Climate change and solar activities during the last millennium
Yang, Hong-Jin
Korean chronicles have a large amount of observational records of natural phenomena, including astronomical and meteorological events over two thousand years. Here we examine the correlation of solar activity and climate change from historical sunspot and frost records in the Korean chronicles. There are 43 sunspot records in Goryeo dynasty (AD 918-1392) and 13 records in Joseon dynasty (AD 1392-1910). It is known that the sunspot records in Goryeo dynasty show a periodicity well in match with the well-known solar activity of 11.3 years. Korean sunspot records suggest that the solar activity in Joseon dynasty decreased compared with the previous ~500 years. In order to examine the long-period variation of solar activity, we include Chinese historical sunspot records in our analysis to supplement the lack of Korean records, and find the new ~240-yr long-period solar activity from the power spectrum analysis. Korean chronicles also have around 600 frost records during the last millennium. We investigate these frost records and find a sign of cooling down that can be interpreted as climate change during the last millennium. We also find ~240-yr cooling period from the historical frost records, which is well in accord with that of 240-yr period solar activity. Therefore, we claim that the solar activity has decreased during the last one thousand years and also has a long-term variation of ~240 years.
NON–DEFORMING ADVECTION
Yankova, Krasimira
The aim is to study the extension on advective hypothesis in the general relativity. As well to trace the prerequisites and consequences in the space-time metrics from excitation and action of the non-deforming advection. This mechanism is proposed to the unified the model high-energy state at accretion in the AGN and non-ACTIVE(sleeping) galactic nucleusses and micro-quasars for completeness. Such type advection is related the occurrence of the connections between the elements in quasar; and for that allows to research the evolution of the mechanism in some of them due to the development of these intercomponent connections.
Infrared astrometric satellite, Small-JASMINE, --Clarification of the formation process of the super massive black hole--
Yano, Taihei
Small-JASMINE (hear after SJ), infrared astrometric satellite developed mainly at National Astronomical Observatory of Japan, will measure the positions and the proper motions which are located around the Galactic center, by operating at near infrared wave-lengths. SJ will clarify the formation process of the super massive black hole (hear after SMBH) at the Galactic center. In particular, SJ will determine whether the SMBH was formed by a sequential merging of multiple black holes. The clarification of this formation process of the SMBH will contribute to a better understanding of merging process of satellite galaxies into the Galaxy, which is suggested by the standard galaxy formation scenario. A numerical simulation (Tanikawa and Umemura, 2014) suggests that if the SMBH was formed by the merging process, then the dynamical friction caused by the black holes have influenced the phase space distribution of stars. The phase space distribution measured by SJ will make it possible to determine the occurrences of the merging process. SJ will determine whether the SMBH was formed through merging process of multiple black holes with high confidence level.
A Blind Analytical CMB Foreground Removal Method: ABS
Yao, Jian
Recovering CMB temperature information out of received signal which includes complex foregrounds, calculating the power spectrum and then comparing with the related models to get cosmological parameters is a kind of basic pipeline in CMB research field. We focus on the first step which is a challenging task and present an analytical algorithm aiming at extracting CMB signal, then test it under different compositions of input signal, including dust, synchrotron, free-free and AME, which are simulated by PYSM, a python package. The power spectra recovered by our algorithm have shown a high consistency with the input values and performed well even in the extreme case. In the future, we will expand the application to CMB polarization, which contains much more information of cosmology.
Star Formation in the Extreme Outer Galaxy
Yasui, Chikako
The extreme outer Galaxy (EOG) has a very different environment from that in the solar neighborhood, with low metallicity (less than -0.5 dex), much lower gas density, and small or no perturbation from spiral arms. The EOG is an excellent laboratory for the study of the star formation processes that happened during the formation period of the Galaxy, nearby dwarf galaxies, and damped Lyman-alpha systems.In our previous NIR surveys of the EOG, we have suggested as follows: i) major triggers of star formation seem different from that in the solar neighborhood (e.g., by supernova remnant and high-velocity cloud accretion), ii) initial mass function (IMF) is consistent with that in the solar neighborhood down to ~0.1M?, iii) the fraction of stars with a K-band excess (which originates from the inner circumstellar dust disk at radii of r ? 0.1 AU) is significantly lower than those in the solar neighborhood.We are planning parallel MIRI/NIRCAM imaging (? = 1.15-21 µm) of Digel Cloud 1 and Cloud 2, which are very young star-forming regions (<1 Myr old), for a GTO cycle 1 observation (PI: Michael Ressler (JPL); GTO1237). For targets that are two of the most distant known regions with Rg ? 20 kpc, we expect to detect sources down to 8 M_J and to distinguish whether stars down to 0.5 M? still have disks. The sensitivity and spatial resolution of JWST will enable us to study star- and planet-forming processes in the EOG at the same depth as the solar neighborhood for the first time. i) we will classifiy the evolutionary stages of YSOs (Class 0 to III), clarify the relationship of classified YSOs with their surrounding environment, and suggest possible formation mechanisms. ii) we will derive the IMF in this low metallicity environment down to the very low-mass end (< 0.1 M?), which is suggested to be a sensitive function of the formation environment and initial conditions. iii) we will gain new insights into the disk evolution of planet-forming region (~0.1-5 AU).
Numerical simulations of intermittent radio jets
Yates, Patrick
Feedback from Active Galactic Nuclei on the host environment is required to maintain the delicate heating/cooling balance in massive galaxies over the latter half of the Hubble time. The process usually invoked is kinetic feedback from radio jets, which do work on their host hot atmospheres through supersonic outflows, shocks and gas uplifting._x005F I have carried out numerical hydrodynamical simulations of radio jets from active galactic nuclei in order to investigate the effect of different environments and intermittency of energy injection on the resulting dynamics, energetics, and observable properties of jet-inflated lobes._x005F Key features of these simulations include the pressure collimation of initially conical jets, and the inclusion of both active and passive jet evolution phases._x005F These simulations show that the environment into which a radio jet is propagating plays a large role in the resulting morphology and continuum surface brightness distribution of the radio source._x005F Additionally, feedback efficiency is found to be strongly dependent on the environment.
Ground-based astronomical observations for supporting and testing the results of selected space missions
Yatskiv, Yaroslav
Ground-based astronomical observations for supporting and testing the results of selected space missions(SOHO,JUNO,CASSINI,GAIA and others)carried out in Ukrine using the world largest radio telescopes UTR-2 and GURT as well as the several optical 2.0 m optical telescopes(2.0m.and 0.7m.) are briefly outlined.Observation examples in the field of Heliophysics,Planetary physics and Positional astronomy are given.
Kinematics of neutral and ionized gas in the candidate protostar with efficient magnetic braking B335
Yen, Hsi-Wei
The magnetic field in collapsing dense cores is expected to slow down the gas motions and transfer the angular momentum of the collapsing material outward, and thus suppress the formation of large-scale Keplerian disks, the so-called "magnetic braking". However, this effect of the magnetic field is observationally not well understood. In this presentation, I will introduce our observational results of the kinematics of neutral and ionized gas in the Class 0 protostar B335. With the single-dish, SMA, and ALMA observations in the neutral molecular line, C18O (2-1), we found that the specific angular momentum in B335 decreases with decreasing radii from 0.1 pc to 100 au scales, and on a 100 au scale the specific angular momentum is a factor of two lower than the expectation from the collapse model where the angular momentum is conserved. In addition, no Keplerian disk with a size larger than 10 au was observed with ALMA. Thus, B335 is a promising candidate with efficient magnetic braking. We have also observed B335 in the ionized molecular line, H13CO+ (3-2), with ALMA. The infalling velocity in the protostellar envelope on a 100 au scale around B335 measured from the H13CO+ emission is consistent with that from the C18O emission within the uncertainty, and our observations put an upper limit of the ion-neutral velocity drift to be 0.3 km/s on a 100 au scale. These results suggest that the magnetic field remains rather well coupled to the bulk neutral material on a 100 au scale, and that any significant field-matter decoupling, if present, likely occurs only on a smaller scale, leading to an accumulation of magnetic flux and thus efficient magnetic braking in the inner envelope. However, due to our limited angular resolution, we cannot rule out that there is a significant velocity drift only in the midplane of the infalling envelope. Future observations with higher angular resolutions are needed to establish the definite presence of ambipolar diffusion in B335.
Forecasts of hourly proton peak fluxes using Long-Short Term Memory and autoregressive methods
Yi, Kangwoo
It is certainly believed that proton flux at geosynchronous orbit (GEO) is an important index to measure space weather risks. Solar activities are well-known sources of distinct proton flux enhancements. A solar proton event (SPE) is defined as an event that the >10 pfu (particle flux unit) of >10 MeV protons. In this study, we apply a Long-Short Term Memory method to hourly proton peak flux prediction using GOES proton data from 2011 to 2016 for training and 2017 for test. To find better optional parameters for the LSTM model, we have tried two different structures (240 units with 1 fully-connected layer and 6 units with 2 fully connected layers), different State conditions (Stateful and Stateless) and different hyper parameters (Adam and AdaDelta optimizers; mean squared error and mean absolute error loss functions; several epoch numbers to avoid over fitting problem). We compare our LSTM predictions with the conventional autoregressive prediction. Our major results are as follows: First, our all LSTM models give us better prediction results than the autoregressive model. Seconds, two LSTM models, which use (A) Adam optimizer with mean squared error loss function and (B) Adam optimizer with mean absolute error loss function, give us the best results with about 10% relative error for 24 hour prediction while the autoregressive method with about 50% relative error. Third, A model is relatively better for rapid enhancement phases while B model for beginning of decreasing phases.
The blue compact dwarf galaxies in MaNGA
Yin, Jun
The nature of possible evolutionary pathways between various types of dwarf galaxies is still not fully understood.Blue compact dwarf galaxies (BCDs) provide a unique window into dwarf galaxy formation and evolution and are often thought of as an evolutionary stage between different classes of dwarf galaxies. In this study we selected a BCDs sample from MaNGA MPL-6, and seperated the starburst (SB) components from the underlying hosts of BCDs via the 2D spectrum. We want to compare our results to the previous photometry-based studies, and investigate the connections between the SB components and the hosts, the structural differences between different types of dwarf galaxies.
THE DIFFUSE GALACTIC -RAY EMISSION AS A PROBE OF COSMIC RAY ANISOTROPY
Yin, Qian-Qing
The diffuse Galactic gamma-ray emission is resulted from the interactions of cosmic rays with the interstellar gas and radiation fields of the Milky Way; the main radiation mechanisms are proton-proton collisions, electron bremsstrahlung, and inverse Compton scattering. Observations of these diffuse emissions provide a tool to study some spatial structures, i.e, the anisotropy of cosmic rays. The pearson correlation coefficient method are used to do correlation analysis between the diffuse Galactic gamma-ray maps and the the cosmic ray maps, and then some correlation spectra are obtained. These spectra show that the spatial correlations between two maps vary as energies of gamma-ray. Hence, the variations of the spectra help to understand the possible radiation mechanisms in the anisotropy of cosmic rays.
Anomalous distributions of deuterated formaldehyde in the low-mass protostar L1527
Yoshida, Kento
We present our works on anomalous distributions of deuterated molecular species found in the Class 0 low-mass protostar L1527. From ALMA observations, we have recently found that the distributions of formaldehyde (H2CO) and the deuterated species (HDCO and D2CO) are clearly different from each other. The emission of H2CO is concentrated on the vicinity of the protostar (r<250 au), indicating the efficient evaporation from dust grains. On the other hand, the deuterated species mainly reside in the outer envelope (r~1000 au), and do not show the emission from the vicinity of the protostar. It has been believed that H2CO and its isotopologues are produced not only in the gas-phase but also on dust grains and released into the gas phase in the warm region near the protostar (T>40 K). This process is indeed the case for H2CO, because its distribution is concentrated around the protostar. On the other hand, our result indicates that the deuterated species are not. According to their distributions, they are likely produced in the gas phase and/or released from dust grains via non-thermal processes in the outer envelope. The D/H ratios in the outer envelope are derived to be high (D2CO/HDCO~30%) in comparison with the other species reported so far (~a few percent in this source). Isotope ratios in molecules can vary along the evolution from interstellar clouds to protostars. As shown above, detailed comparisons of distributions of the isotopic ratios will be useful for understanding how such an evolution in the molecular isotopic ratios occurs. Furthermore, such studies can be extended to disk-forming regions with ALMA, which will provide us with rich information bridging the interstellar chemistry and the planetary chemistry.
Observation campaigns of (3200) Phaethon and (155140) 2005UD for the DESTINY+ mission
Yoshida, Fumi
The DESTINY+ (Demonstration and Experiment of Space Technology for INterplanetary voYage, Phaethon fLyby and dUSt science) is an upcoming JAXA/ISAS flyby mission to asteroid (3200) Phaethon, the parent body of Geminid meteor shower. The spacecraft will investigate the dust trail of Phaethon, a dust distribution and compositions of the dust nearby Phaethon, surface/geology of Phaethon, and so on.We organized the ground-based observation campaign of Phaethon in 2017 for gathering as much scientific knowledge about Phaethon as possible before the spacecraft launch. And we will host another ground-based observation campaign for 2005UD in 2018, which is a possible breakup body of Phaethon and a possible second flyby target of DESTINY+.
A spatially resolved view of molecular clouds at reduced metallicity in the Magellanic Clouds
Zahorecz, Sarolta
The Magellanic Clouds offer the opportunity to obtain a spatially resolved view of external galaxies at reduced metallicity with no distance ambiguity. Especially, the SMC represents a unique astrophysical laboratory because of its proximity, lower ISM metallicity, and tidally disrupted interaction status. The SMC offers a rare glimpse into the physical processes in an environment with a metallicity that is below the threshold of 1/4–1/3 Zo, where the properties of the ISM in galaxies change significantly. We have performed ALMA observations in various molecular lines toward the active star-forming region N83C in the SMC. The observations first revealed subparsec-scale molecular structures in 12CO and 13CO (2-1) emissions (Muraoka et al. 2017). We found strong CO peaks associated with YSOs and derived a typical gas density of ~104 cm-3 and gas temperature of 40-60 K from the excitation analysis. The high gas density and temperature are presumably due to the effect of the HII region under the low-metallicity environment in the SMC; far-UV radiation can easily penetrate and photodissociate the outer layer of 12CO molecules in the molecular clouds, and thus only the innermost parts of the molecular clouds are observed even in 12CO emission. This molecular gas distribution is compared with that in the LMC and the Galaxy, where the filamentary structure is dominated, with the same actual spatial resolution; ALMA for the LMC, and large/small single dish telescopes for the Galaxy. We have recently carried out ALMA observations toward N83C in [CI] (1-0) to investigate the photodissociation of CO in the low metallicity environment. The column density ratios N(CI)/N(CO) are generally high throughout the cloud compared with the Galaxy, ranging from 0.2 to 2.0. A peak of the ratio is observed toward a CO peak associated with a massive protostar; the enhancement of the ratio toward the dense gas is rarely seen in molecular clouds in the Galaxy.
ALMA view of a cold cloud: unbound cores with chemical differentiation
Zahorecz, Sarolta
Herschel and Planck detected cold, dense clouds in emission throughout the Galaxy. Unlike targeted and area-limited surveys toward the inner part of the Galaxy, these new observations provided an unbiased catalog of the star forming clumps in the outer part of the Galaxy also. We have examined the physical properties of a homogeneous Galactic cold core sample obtained with the Planck satellite across the Galactic plane with the use of Herschel Hi-GAL observations. We calculated and analyzed the basic physical parameters of 48 Planck clumps as a function of location within the Galaxy. About 25% of the clumps are massive enough to form high-mass stars and star clusters. Planck clumps toward the Galactic center region show higher peak column densities and higher average dust temperatures than those of the clumps in the outer Galaxy. Based on our data, the Hi-GAL data showed no apparent differences in the properties of Planck clumps with and without star formation.We performed a high-resolution follow-up study of G191.51-0.76. It has a network of filaments converging into a central clump forming a hub-filament system and it does not show 70 micron sources making it a younger, scaled-down version of massive hub-filament systems, e.g. IRDC SDC13, G33.92+0.11. We observed the continuum, N2H+, HNC and 13CS emission toward it with ALMA to determine its small-scale physical structure and level of fragmentation. We identified two dense low-mass clumps (with a radius of 0.08pc) based on the SCUBA-2 data. These clumps further fragment at higher-angular resolution into four main dense cores (with a radius of 0.02pc) and a few small fragments detected only in selected tracers. No continuum source is detected in our high-sensitivity images of ALMA. The dense cores show chemical differentiation: while the N1 core is the youngest with bright HNC emission, the southern region is the most evolved with some evidence of CO depletion present in its hosting clump.
Deuteration of formaldehyde - an important precursor of hydrogenated complex organic molecules - during star formation in our Galaxy
Zahorecz, Sarolta
The formation of deuterated molecules is favoured at low temperatures and high densities. Therefore, the deuteration fraction is expected to be enhanced in cold, dense prestellar cores and to decrease after protostellar birth. Previous studies have shown that the deuterated forms of species such as N2H+ (formed in the gas phase) and CH3OH (formed on grain surfaces) can be used as evolutionary indicators and to constrain their dominant formation processes and timescales. Formaldehyde (H2CO) is crucial in any chemical networks because it is very abundant and it is an important precursor of hydrogenated complex organic molecules (COMs). Non-energetic (atom bombardment) reactions offer one of the pathways toward COM formation at temperatures as low as 10 K.H2CO and its deuterated forms can be produced both in the gas phase and on grain surfaces. However, the relative importance of these two chemical pathways is unclear. Comparison of the deuteration fraction of H2CO with respect to that of N2H+, NH3, and CH3OH can help us to understand its formation processes and timescales. With the new SEPIA Band 5 receiver on APEX, we have observed rotational lines of HDCO and D2CO at 193 GHz and 175 GHz toward eleven massive star-forming regions hosting objects at different evolutionary stages: high-mass starless cores, high-mass protostellar objects, and ultracompact HII regions.Our observations show that singly and doubly deuterated H2CO is detected toward all sources and that the deuteration fraction of H2CO increases from the starless to the protostellar phase and then sharply decreases in the latest evolutionary stage. H2CO may display a similar fractionation pattern as that of CH3OH in massive young stellar objects. This finding suggests that solid-state reactions dominate its formation.
A double cold core in Auriga-California Molecular Cloud
Zahorecz, Sarolta
A detailed study of the densest cold core in the Auriga-California Molecular Cloud is presented based on ammonia line measurements with the Effelsberg-100m telescope applying a radiative transfer model with two 3-dimensional spheres. Our high spectral resolution high S/N observations shows two different velocity components with a separation of 0.5km/s.Radiative transfer modeling of NH3 line emission were performed. We have used cppsimu, a non-LTE Monte-Carlo radiative transfer simulation. In this, each cell in the model box is essentially described by its gas content's density, kinetic temperature, line of sight and turbulent velocity components and the given species' abundance. Our model box, was constructed as the sum of two spherically symmetric density and temperature distributions in each cell, aiming to reproduce the observed double line profile. We used a Plummer-like profile to describe the spheres' density distributions. (A Bonnor-Ebert profile based fit yields mass estimates consistent with a Plummer one within 1 sigma, hence it qualitatively does not change our results.)The radiative transfer equation was then solved by cppsimu propagating photon packages through this box. It then produced mock spectra with a matched beam size and spacing to our Effelsberg-100m observations.These model spectra were optimized against our NH3 (1,1) and (2,2) data in 34 positions simultaneously by changing nine parameters in the model: kinetic temperatures, sizes, central densities, line of sight velocities and turbulent velocity components of each clumps independently and their separation perpendicular to the line of sight. The initial values of these and the line of sight velocities were based on measured ones derived from our observations.The model optimization was performed with a Bayesian-approach.
Modelling the jet kinematics of OJ287: paradigm for other blazars?
Zajacek, Michal
OJ287 belongs to one of the best candidates among active galactic nuclei to host the binary supermassive black hole at very close separation. Based on a recent analysis of 120 VLBA (Very Long Baseline Array) observations at 15 GHz by Britzen et al., we set up a basic kinematical model to explain the motion of jet components. The model involves the jet precession, on top of which we find an indication of additional nutation-like motion for the first time. The ratio of the precession and nutation periods is about 20. The precessing motion is quite natural in the supermassive black hole binary system, due to the torques exerted by the companion black hole on the accretion disc around the primary. The other explanation is provided by the disc misalignment with respect to the spin of a single black hole. The jet precession then occurs due to the Lense-Thirring effect. Both scenarios indicate a rich merger history of OJ287, which may be a general characteristic of blazars. This model contribution is complementary to the observational contribution by Britzen et al.
Radio-spectral index distribution of SDSS-FIRST sources across optical diagnostic diagrams
Zajacek, Michal
For a selection of a few hundred intermediate-redshift SDSS-FIRST galaxies, we performed radio-continuum observations at 4.85 and 10.45 GHz with the Effelsberg 100-m telescope. The selected sources cover mainly the Composite-AGN part in the optical diagnostic diagrams (ODDs). The ionization-state information and the radio loudness at 1.4 GHz was complemented by spectral-index distribution between 4.85 and 10.45 GHz. We performed an extensive analysis of the distribution of steep, flat, and inverted radio sources across ODDs. Three main classes of objects were found: (i) sources with steep radio index, high ionization ratio and large radio loudness, (ii) sources with flat radio index, lower ionization ratio and intermediate radio loudness, and (iii) sources with inverted radio spectra, low ionization ratio and low radio loudness. The groups (i), (ii), and (iii) are prominent on the transition from Seyferts to LINERs in the direction of the decreasing ionization-line ratio, where the trend of radio-spectral index flattening is found. These findings are interpreted in terms of the recurrent nuclear/jet activity, partially driven by galaxy interactions and mergers.
Magnetized stars embedded in AGN accretion disks and tori
Zajacek, Michal
A population of magnetized stars (neutron stars, white dwarfs, young T Tauri stars, and chemically peculiar Ap and Bp stars) is expected to be embedded within an accretion disk or a torus near a supermassive black hole (SMBH) in active galactic nuclei (AGN). The dipole-type magnetic field can significantly influence the gaseous environment within the region of influence around the star, depending on the intrinsic strength of its dipole and parameters of the surrounding medium. We estimate the fraction of the volume in the accretion disk/torus where the structure must be entirely changed by the presence of the embedded magnetized stars, as compared with an unperturbed solution.
Gravitational wave signal from neutron star mergers as a tool to constrain EOS for nuclear matter
Zakharov, Alexander
Gravitational wave signal from the neutron star merger has been detected recently. We present a set of gravitational wave templates which are calculated with different choices of equation of state (EOS) for neutron stars. We discuss opportunities to rule out or/ and constrain some EOS from future observations of gravitational wave signals and their electromagnetic counterparts.
Opportunities for discoveries of hairy black holes in Horndeski gravity with the Event Horizon Telescope
Zakharov, Alexander
The classical general relativity (GR) is remarkably confirmed in different astronomical tests. Recently, gravitational waves have been detected from binary black holes and binary neutron star systems. Moreover, constraints on alternative theories of gravity have been obtained, it means that such theories if massive gravity, if they are realized in nature, have to be very close to GR. In spite of a great progress of GR now there exist a number of alternative theories of gravity. A main reason to introduce alternative theories of gravity is a hope to explain dark matter and dark energy phenomena as gravity effects. Scalar-tensor theories proposed by Horndeski (1974) are among popular alternatives for classical general relativity (GR). Babichev et al. (2017) constructed a set of hairy static black hole solutions (for quartic Hordeski Lagrangian of scalar-tensor theory of gravity). We derive analytical expressions for shadow size for static asymptotically flat black holes considered by Babichev et al. (2017) and one could compare theoretical predictions and observations for black holes with a scalar hair which mimics an electric charge. We present analytical expressions for shadow size for static black hole solutions with de-Sitter and anti-de-Sitter asymptotics. The relations could be used for comparison of the theoretical models of hairy black hoiles with observational data obtained with the Event Horizon Telescope for the black hole at the Galactic Center or in the back hole in galaxy M87.
Improvement perspectives for graviton mass bounds from an analysis of bright star orbits near the Galactic Center
Zakharov, Alexander
Recently, the LIGO-Virgo collaboration discovered gravitational waves and in their first publication on the subject the authors also presented a graviton mass constraint as mg < 1.2 * 10-22 eV (Abbott et al. 2016) . In our previous papers we considered constraints on Yukawa gravity parameters [1] and on graviton mass from analysis of the trajectory of S2 star near the Galactic Center [2]. In the current studies we analyze a potential to reduce upper bounds for graviton mass with future observational data on trajectories of bright stars near the Galactic Center. These new data will be obtained with current and forthcoming large observational facilities Keck, VLT, GRAVITY, TMT, E-ELT, JWST. Since gravitational potentials are different for these two cases, expressions for relativistic advance for general relativity and Yukawa potential are different functions on eccentricity and semimajor axis, it gives an opportunity to improve current estimates of graviton mass with future observational facilities. In our considerations of an improvement potential for a graviton mass estimate we adopt a conservative strategy and assume trajectories of bright stars and their apocenter advance will be described with general relativity expressions and it gives opportunities to improve graviton mass constraints. We present our expectations to improve current constraints for graviton mass, assuming the GR predictions about apocenter shifts will be confirmed with future observations (VLT, Keck, GRAVITY, TMT, E-ELT). We concluded that if future observations of bright star orbits during around fifty years will confirm GR predictions about apocenter shifts of bright star orbits it give an opportunity to constrain a graviton mass at a level around 5.0 * 10-23 eV or slightly better than current estimates obtained with LIGO observations._x005F _x005F References_x005F _x005F 1. D. Borka et al., JCAP 11 (2013) 050._x005F _x005F 2. A. F. Zakharov et al., JCAP 5 (2016) 045.
Probing the Mass Assembly of Galaxy Systems With Weak Lensing
Zamorano Vitorelli, André
Several indicators have been proposed as proxies for early formed galaxy systems: magnitude gaps (the difference in magnitude between the central galaxy and the brightest satellite in the inner region), the physical offset between the central galaxy and the luminosity centroid, the mass-concentration relation, and the luminosity of the brightest galaxy among others. We investigate the nature of fossil systems (those with very large magnitude gaps) in particular, and the mass assembly history of galaxy systems in general, using weak lensing to characterize their mass-concentration relations and overall mass distributions, and compare it to the other indicators and their luminosity functions in data from several current (SDSS, CS82) and upcoming (Blink, JPAS) surveys, as well as their luminosity functions across several redshift slices.
The action of gaseous matter and the principle of the formation of two stars
Zhang, Man Ping
[The effect of the atmosphere on celestial bodies]_x005F I think the two with the atmosphere of the celestial bodies in the universe when they met the first contact with the earth's atmosphere can not directly collided, two objects to collide with the atmosphere conditions must be away the atmosphere, (two celestial atmosphere contact gravity is less than the attraction of two objects themselves for gas, two gas own gravity cannot both unity) between the two objects at a distance to meet the need of gravity away atmosphere to make two gas both unity can collide, push not collided atmospheric walk or not. Don't ignore the atmosphere that is depends on how much is the content of the atmosphere, atmosphere and material away it needs power, such as the atmosphere around the earth to the other half the ball to the other half of the ball pressure will increase by resistance, so the atmosphere is two celestial body resistance (mutual gravity when the two objects and two celestial atmosphere to the resistance of the force balance) between two objects distance on the force balance neither close to or separate, two celestial atmosphere in the form of a sphere contact form binary phenomenon. Binary stars are captured and formed when the third and more objects are captured. (a two-star phenomenon must be a celestial body with an air layer, and a small object with no air layer is directly into any object that has an atmosphere.)_x005F Author: zhang manping_x005F Application_x005F Hello: I applied to participate in the 30th Congress of the International Astronomical Union, thank you for allowing non-professionals to register for this Congress! I hope my application for participation in the meeting has been approved. Thank you!_x005F Applicant: Cheung Man Ping
The Insight-HXMT observation of the newly discovered transient X-ray pulsar Swift J0243.6+6124
ZHANG, Yue
Since the discovery of the Be/X-ray binary Swift J0243.6+6124 in an outburst showing up around 2017 October 3, Insight-HXMT has continuously monitored on this source in a broad energy band covering roughly 1-250 keV. With these observations the orbital ephemeris of the system are derived and refined later on, according to the variability of the spin frequency, which denotes a canonical Doppler effect endorsed by the orbital motion in a NS binary system. We therefore estimate the orbital ephemeris of Swift 0243.6+6124, thanks to the long term observations from Insight-HXMT. The orbital parameters are then obtained by us with a period around 27.35 days, a semi-major axis around 199 light-seconds, an eccentricity around 0.0842. We find from Insight-HXMT data that, both the pulse profile and phase-resolved spectrum evolve strongly with luminosity, which points to the complexity of the outburst exhibited by Swift J0243.6+6124.
The 17 pairs of double neutron star systems and their evolutionary links with HMXBs
Zhang, Chengmin
For the observed 17 pairs of double neutron star systems, we analyze their eccentricity and orbital period, and find that theses DNSs can be classiffied into theee types, which may correspond to the NS formation history, e.g. by supernova or electron capture. Their relations with the progenitor HMXBs are investigated. We simulate the processes, with various initial conditions, and the observed DNS distribution can be satisfactorily explained.
Machine Learning for RR Lyrae Stars
Zhang, Yanxia
We explore machine learning to target RR Lyrae stars from large survey databases (SDSS and GALEX). Classification of RR Lyrae stars from other types of stars belongs to the imbalance learming issue. Therefore the usual machine learing algrithms are not fit for this kind of issue. In this paper,cost-sensitive support vector machine,cost-sensitive random forest and fast boxes are applied to select RR Lyrae stars from other types of stars. Experimental results show that fast boxes is the best performer and the infomation added from ultraviolet band is helpful to seperate RR Lyrae stars.
Proposed VLBI Observations in the FAST Commissioning Stage
Zhang, Haiyan
The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega science project, and the main structure of the telescope had been completed in September 2016. Now the FAST is in the commissioning stage._x005F As the most sensitive single-dish radio telescope, Very Long Baseline Interferometry (VLBI) research with FAST is one of the key goals. Due to its extremely collecting area and the location, FAST will greatly improve the sensitivity of VLBI observations, and detect more weak radio sources than ever before. For instance, if FAST joins into the European VLBI Network (EVN), the image sensitivity will be increased to 4.5 uJy/beam. Several scientific goals have been proposed for FAST VLBI observations, such as compact radio sources survey, and study the physical mechanism of Active Galactic Nuclei (AGNs); pulsar Astrometry, radio stars etc._x005F However, the complexity and the innovative nature of the FAST systems pose many challenges. The observations in draft–scan mode have been proposed to avoid the complex scan patterns and fast driving/switching of the telescope. Several new pulsars have been detected by FAST successfully recently._x005F For VLBI test observation with FAST, the objective is to establish VLBI observation system and detect the first VLBI fringe. In the commissioning stage, several adjustment and early sciences goals have been considered, such as observing calibrators to detect the first fringe, detecting strong OH and HI maser sources etc. Till now, the FAST VLBI backend using ROACH2 board has been developed and tested in the laboratory. The disk-based Mark 6 has also been built to record the observing data. The first VLBI fringe of FAST is expected in 2018.
Gas dynamics and NH$_2$D chemistry in high-mass pre/protocluster clumps
Zhang, Chuanpeng
The initial stage of star formation is very difficult to study due to its high density ($n_{\rm H_2} >$ 10$^6$\,cm$^{-3}$) and low temperature ($T_{\rm dust} <$ 18\,K), which lead to many molecules depleted from the gas phase by freezing out onto dust grains. However, the deuterium species like NH$_2$D could survive in the extreme condition. In this work, we present NH$_2$D, NH$_3$ (1,\,1) and (2,\,2) observations using PdBI and VLA, respectively, towards eight massive precluster clumps (G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71). We use 3D \textit{Gaussclumps} to extract NH$_2$D cores and provide a statistical view of their deuterium chemistry. The NH$_2$D cores are gravitationally bound, and have potential to form intermediate- or high-mass stars in future. We find that NH$_2$D emissions are not associated with either a dust continuum or NH$_3$ peak position or infrared source, but just surrounding the central continuum cores, suggesting they are prestellar or starless cores. We detect extreme high deuterium fractionation of $0.03 \leqslant D_{\rm frac} \leqslant 1.41$ with a median value of 0.45$\pm$0.01. We find that the correlation between $D_{\rm frac}$ and $T_{\rm kin}$ is a positive-correlation from 13 to 16.5\,K, but anti-correlation from 16.5 to 22\,K. The most suitable habitat for NH$_2$D reaction may be at the temperature of around 16.5\,K. The detected NH$_2$D lines are very narrow with a median value of around 0.94$\pm$0.09\,$\kms$. The line widths are still dominated by both thermal motions and turbulence. Using NH$_3$ (1,\,1) as a dynamical tracer, we find a very complicated dynamical movement towards all the eight clumps, either outflow and rotation, or convergent flow and collision, or large velocity gradient. The sample generally present obvious characteristic of Keplerian disk, suggesting that accretion is keep going and increasing gradually from prestellar core to evolved source stages.
Burst probe to XRB accretion and Insight-HXMT observation
Zhang, Shu
Although corona has been being well used in modelling accretion of XRBs, especially on aspects of the spectral state transitions and correlation with launching of a jet, so far its nature is still less known, especially on aspect of the formation mechanism. To probe this puzzle observationally, one has firstly to have a proper probe like the intense short soft X-ray shower, since the corona is in definition less emissive and can only be lighted up with the incident soft X-rays. This probe, however, falls short in BH XRBs, but fits well the thermal nuclear flashes occurring on the NS surface. We therefore took the type-I burst to probe the accompanied disk/corona evolution and obtained an atoll sample which shows that corona can be cooled off by the burst shower. Further studies suggest that, a variety of issues apart from corona can be addressed as well by taking this probe. The current shortage in observations at hard X-rays is the relatively poor statistics of the data, which can be diminished by the HXMT mission.
Spectrum-energy Correlations in GRBs: Update, Reliability, and the Long/Short Dichotomy
Zhang, Zhi-Bin
Spectrum-energy correlations of peak energy with total prompt ?-ray emission energies, namely Ep,i - Eiso, Ep,i - Eg , and Ep,i - Lp, had been studied for long gamma-ray bursts (GRBs) previously by many authors. These energy correlations were proposed to measure the universe and classify GRBs as useful probes. However, most of these relations were built by non-Swift bursts. The spectrum-energy correlations of short bursts have not been systematically established yet; in particular, how the newly found GRB170817A matches these energy relations is unknown to date. We will ?rst refresh the three spectrum-energy relations of Swift/BAT and Fermi/GBM long bursts and build the corresponding relations of short bursts. Then, we con?rm whether they are commonly available as a discriminator of short and long GRBs. Some potential violators to these relations will be investigated. Combining with the plane of peak energy versus ?uence, we select 31 short and 252 long GRBs with well-measured peak energy and redshift to study the issue of GRB classi?cations connected with the above energy relations statistically. We ?nd that the three energy relations do exist in our new GRB samples and they are marginally consistent with some previous results. We report for the ?rst time that short GRBs hold the three corresponding energy relations having the consistent power-law indices with long GRBs. It is found that these energy relations can be adopted to discriminate GRBs successfully if they are put in the peak energy versus ?uence plane. Excitingly, we point out that GRB090510 matches the energy relations of Ep,i - Eiso and Ep,i - Lp, but violates the Ep,i - Eg relation. More excitingly, we ?nd that GRB170817A is an outlier to all the three energy correlations.
The Radio Flux-Redshift Dependence of Gamma-Ray Bursts and Their Host Galaxies
Zhang, Zhi-Bin
Using multi-wavelength observations of radio afterglows, we confirm the hypothesis that flux density of Gamma-Ray Bursts (GRBs) will become invariable as the GRBs locate far enough, that is to say the detection rate will be approximately independent of redshift. It is found that short and SN-associated GRBs marginally match the flux-redshift relationship in nearby universe and they could be outliers. We study this novel behavior theoretically and find that it can be well explained by the standard forward shock model involving a thin shell in both ISM and wind circumstances. A potential relation of medium density with redshift, namely $n\propto(1+z)^4$, has been ruled out according to the current measurements of $n$ and $z$ for short and long GRBs. In addition, the possible dependence of host flux on the redshift is also investigated. We discover the similar flux-redshift independence as well, which implies the detection rate of radio hosts might be also independent of the redshift. For the first time. Finally, we predict the detection rates of radio afterglows by next-generation radio telescopes such as FAST, LOFAR, MeerKAT, ASKAP and SKA.
TMRT observations on H2CO & H213CO toward molecular clouds in our Galaxy
Zhang, JiangShui
We present observations of the 110-111 and 211-212 absorption lines of H2CO and the 110-111 lines of H213CO toward a large sample of more than 100 Galactic molecular clouds, through the Shanghai 65m Tianma Radio Telescope (TMRT). Complementary continuum at 2 cm and 6 cm through TMRT were also performed to determine the optical depth and further determine better the isotope abundance ratio. We got 38 sources with all lines and continuum data. Our preliminary results show that the abundance ratio of H212CO and H213CO tends to increase with increasing galacocentric distance, though the scatter of the ratio is large. Further modeling works are necessary and important to discuss the optical depth effect on the isotope ratio 12C/ 13C.
Research on asteroid physical characteristics and its distribution
Zhao, Haibin
In this lecture, we will investigate the distribution of the spin state of asteroids and the elementary physical characteristics of asteroids by using of the light-curve survey observation of China Near Earth Object Survey Telescope (CNEOST), where three key scientific issues of planetary science and the Chinese asteroidexploration mission, i. e., the three dimension shape, the thermal physical model and irregular gravitation field will be substantially explored. Additionally, the statistical distribution with asteroid size and location, theformation and evolution process of asteroid families will be concerned and explored. Through the implement of this survey program, the globally characteristics for asteroid belt will be eventually achieved, which may provide concrete scientific information to Solar System bodies formation and evolution.
The introduction of the HXMT Data Analysis Software
Zhao, Haisheng
The Hard X-ray Modulation Telescope consists three main payloads: the High Energy X-ray Telescope, the Medium Energy X-ray Telescope and the Low Energy X-ray Telescope. The science analysis of the data from each payload is organized in three stages: calibration, screening and extraction of high-level scientific products. The HXMT Data Analysis Software is designed to meet the requirements of the three stages and provide several tasks with each task is to accomplish a single function in one of the three stages. These tasks are written in ftools style and fully compatible with the HEASoft software. This work will introduce the three stages for each payload and the Data Analysis Software.
Isotope fractionation in the photochemical escape from Early Mars
ZHAO, Jinjin
The isotope ratios of C and O on Mars record important information about the past atmosphere evolution of the planet. 13C/12C and 18O/16O in the modern Martian atmosphere have been measured by multiple planetary missions. Martian meteorites are the most important isotopic composition indicator for the early Martian atmosphere. In this work, a 3-D Monte Carlo Model built to investigate isotope fractionation of C and O during the photochemical escape. Ionosphere and thermosphere structures for 1, 3, 10, and 20 times the present solar XUV flux, corresponding to solar activity levels at 2.5, 3.8, and 4.1 Gyrs ago, are considered in this model. Preliminary results show that the fractionation factor for 18O relative to 16O is constant ˜0.65, while that of 13C relative to 12C from 0.5 to 0.8 with solar XUV flux increasing. To make the observed C and O isotopic ratios consistent with the values of d13C=46 (VPDB) and d18O=48 (VSMOW) from Curiosity, our model suggests that ˜40 mbar CO2 and ˜180 mbar H2O have been lost to space due to DR-induced photochemical escape. Such estimates are lower limits because other important loss mechanisms such as photodissociation, sputtering, carbonate deposition for C, and iron oxidation for O, are not considered. Besides, the present C isotopic ratio in Mars atmosphere could be dominated by the contribution of CO2 released to the atmosphere through volcanism or polar cap sublimation during the period of DR-induced escape.Based on the D/H isotope fractionation factor observed by Curiosity, >120 m GEL of water could have been lost, but most of the oxygen sink could have been iron oxidation (e.g. through serpentinization of the crust). Based on estimates of volcanic outgassing rates, >400 mbar CO2 could have been released into the atmosphere, but most carbon loss could be due to carbonate formation in subsurface hydrothermal. Our results provide a preliminary estimate of the contribution of non-thermal escape to Mars atmosphere evolution.
The Distance to and the Near-infrared Extinction of the Monoceros Supernova Remnant
Zhao, He
Supernova remnants (SNRs) contain information on the influence of supernova explosions on dust properties. Based on the color indices from the Two Micron All Sky Survey and the stellar parameters from the SDSS–DR12/Apache Point Observatory Galactic Evolution Experiment and LAMOST-DR2/LAMOST Experiment for Galactic Understanding and Exploration spectroscopic surveys, the near-infrared extinction law of and the distance to the Monoceros SNR are derived together with those of two nebulae close to it, the Rosette Nebula and NGC 2264. The distance is found at the position of the sharp increase of the interstellar extinction with distance, and the nebular extinction is calculated by subtracting the foreground interstellar extinction. The distance to the Monoceros SNR is determined to be 1.98 kpc, larger than previous values. Meanwhile, the distance to the Rosette Nebula is 1.55 kpc, which is generally consistent with previous work. The distance between these two nebulae suggests no interaction between them. The distance to NGC 2264, 1.20 kpc, exceeds previous values. The color excess ratio, EJH/EJKs, is 0.657 for the Monoceros SNR, consistent with the average value of 0.652 for the Milky Way. This consistency results from the fact that the SNR material is dominated by interstellar dust rather than by supernova ejecta. EJH/EJKs is equal to 0.658 for the Rosette Nebula, further proving the universality of the near-infrared extinction law.
PROPERTIES OF THE LOCAL LENS MAPPING USING MICROLENSED LINES OF THE X-RAY SPECTRA FROM ACTIVE GALACTIC NUCLEI.
Zhdanov, Valery
The profiles of relativistic lines in the X-ray spectra of active galactic nuclei (AGN) contain important information about the AGN "central machine". If AGN is the source of a gravitational lens system with microlensing events, additional data can be obtained about both the accretion disk around the central black hole and the parameters of the local lens mapping. We performed simulations of the microlensed lines formed in the thin accretion disk during the High Amplification Events. Several models of the accretion disk structure and approximations concerning the the local lens mapping are discussed. We have shown that the time dependence of the line profiles depends strongly on the caustic orientation with respect to the disk, which makes it possible to estimate this orientation along with the distribution of the line intensity over the disk.
VLBI applications in high accuracy tracking of lunar and deep-space probes
Zheng, Weimin
The Chinese VLBI (Very Long Baseline Interferometry) Network – CVN consists of five radio telescopes and one data processing center. CVN is a powerful tracking and navigation tool in the Chinese lunar exploration project. To meet the quick response of the CE lunar probes navigation requirements, station observation data must be sent to the VLBI center and processed in real time mode. CVN has demonstrated its ability in the CE-1 and CE-2 missions of tracking the circumlunar probes. In 2013, the CE-3 lander was successfully sent to the lunar surface and the Yutu rover was released. CVN has not only supported the softlanding mission but also successfully determined the relative position of the rover with about 1meter accuracy.In these lunar exploration missions, different kinds of onboard beacons, such as the telemetry signals, the special VLBI signals, the data transmission signals and the Differential Oneway Range (DOR) signals were used. The e-VLBI technique made the observable turnover time as short as 20~40 seconds. Normally, VLBI group delay and rate are used for probe tracking. In CE-3 mission VLBI group delay residuals after orbit determination was nearly 0.5ns. The accuracy of landing position is better than 100 meters. To get a more accurate result, we have carried research on the Interferometry imaging technique and VLBI phase delay observables.The paper also introduces the imaging results of ChangE lunar and Mars Express probes. The measured ChangE-3 (CE-3) Rover relative position accuracy is about 1 m by this method. The 1 m accuracy is verified by comparisons with Rover null position and the onboard stereo vision measurement results. The successful imaging of spacecraft indicates that the interferometry imaging and real-time same beam VLBI technology can be used for the accurate spacecraft positioning, probe rendezvous and docking and docking, the earth-moon baseline space VLBI experiment and the Chinese planetary probes in the future.
Field Distortion Model Based on Fredholm Integral
Zhou, Jianfeng
Field distortions in imaging process can cause serious loss of accuracy. These distortions are normally caused by geometric errors of imaging devices, installation errors or environmental vibration. We propose the Fredholm Integral Model to describe an imaging process with distortion. A polynomial approximation is proposed to estimate the distortion kernel with sufficient accuracy to micro-pixel.
Which supernova remnant results from the “guest star” of AD 386
Zhou, Ping
The ancient records of “guest star” provide crucial information for modern supernova remnant (SNR) studies. However, most of our knowledge about historical supernovae was obtained from those observed after AD1000. A few early-time “guest star” records with medium or long duration of visibility have not been successfully connected to known SNRs. With accumulating multi-wavelength observations in the past decades, it is now possible to measure the SNR ages, distances and absorptions with better accuracy. These parameters may help find new SNR counterparts of the early-time “guest stars”, and enlarge the small sample of historical supernovae. We start with the “guest star” of AD 386, which was recorded visible in a 3-month period. There are a few X-ray-emitting SNRs projected in the vicinity of this “guest star”. By comparing the properties of these SNRs, we investigate which SNR is most likely related to it.
Vertex Reconstruction of Neutrino Interactions in Liquid Scintillator
Zhou, Jianfeng
Reconstruction including vertex and momentum in neutrino experiments always needs plenty of accurate charge and time information. We using slow liquid scintillator to get more detailed two information rather than the single material such as water or normal scintillator. A maximum likelihood algorithm is used to process the data from the simulation with the condition in Jinping neutrino experiment, which has a energy resolution of ~ 10%/ E(MeV)1/2 and vertex resolution is relative to the received photon numbers. The separation of liquid scintillator and Cherenkov photons play a vital role in direction reconstruction, which has been used in Jinping real 1 ton model analysis.
A discrete chemo-dynamical model of the dwarf spheroidal galaxy Sculptor: mass profile, velocity anisotropy and internal rotation
Zhu, Ling
The difficulty of core and cusp problem, comes from the limited number of data points, as well as the degeneracies between the mass profiles and the internal dynamical properties of the tracer stars, velocity anisotropies and internal rotations. We present a new discrete chemo-dynamical axisymmetric modeling technique, which we apply to the dwarf spheroidal galaxy Sculptor. The major improvement over previous Jeans models is that realistic chemical distributions are included directly in the dynamical modelling of the discrete data. This avoids loss of information due to spatial binning and eliminates the need for hard cuts to remove contaminants and to separate stars based on their chemical properties. Using a combined likelihood in position, metallicity and kinematics, we find that our models naturally separate Sculptor stars into a metal-rich and a metal-poor population. The spherical assumption of this galaxy resulted in strong constraint of a cored halo in the literatures. Allowing for non-spherical symmetry, our approach provides a central slope of the dark matter density of gamma = 0.5 +- 0.3. The metal-rich population is nearly isotropic (with beta_r^red = 0.0+-0.1) while the metal-poor population is tangentially anisotropic (with beta_r^blue = -0.2+-0.1) around the half light radius of 0.26 kpc. A weak internal rotation of the metal-rich population is revealed with v_max/sigma_0 = 0.15 +- 0.15.We run tests using mock data to show that a discrete dataset with ~ 6000 stars is required to distinguish between a core (gamma = 0) and cusp (gamma = 1), and to constrain the possible internal rotation to better than 1 sigma confidence with our method.
The diversity of stellar metallicity gradients across the HUBBLE sequence
Zhuang, Yulong
We analyze the radial stellar metallicity gradients out to 1Re for 249 CALIFA galaxies which range from morphological type E to Sd, to study the driving mechanisms of stellar metallicity gradients. Our results show that linear metal fraction (Z) gradients offer a clearer correlation with galaxy morphological type - with early type galaxies showing the steepest gradients. As these galaxies show more concentrated surface mass density profiles, we show that the Z gradients simply reflect the local mass-metallicity relation within a galaxy. This suggests that the radial stellar population distribution within Re is primarily a result of the in-situ local star formation history. In this simple picture, the mass density gradient directly predicts the metallicity gradient of a galaxy. We show that this correlation and its scatter can be reproduced entirely by using independent empirical galaxy structural and chemical scaling relations. Using Schwarzschild dynamical models, we explore the link between a galaxy's local stellar populations and its orbital structure. We find that galaxies' angular momentum and Z gradients show diametric behavior in different mass regimes: for low mass galaxies the angular momentum increases as the Z gradient becomes steeper, while for higher mass galaxies vice versa. We show these are driven by a mass density-angular momentum correlation rather than a causal link between stellar dynamics and metallicity gradients. This suggests that these gradients in the inner disk are not strongly shaped by radial migration, which is confirmed by the lack of correlation between the metallicity gradients and observable probes of radial migration in the galaxies, such as bars and spiral arms.Finally, we find that galaxies with positive metallicity gradients become increasingly common towards low mass and late morphological types - consistent with stellar feedback more efficiently modifying the baryon cycle in the central regions of these galaxies.
Cluster star formation quenching probed by gas metallicity
Ziegler, Bodo
In Maier+16 we presented an analysis of gas metallicity (O/H abundances) in the CLASH cluster MACS0416 at z=0.4 subdividing 76 members in phase space into accreted and infalling galaxies finding a stark contrast: the fraction of metal-rich galaxies is in the inner region much higher than in the outskirts (63% to 28%). The high O/H abundances are not in line with the Fundamental Metallicity Relation and violate simple bathtub model predictions. Chemical evolution models instead demonstrate that a shut-off of (primordial) gas accretion onto the disk is required that can be achieved by strangulation mechanisms that also quench ongoing star formation. Currently, we expand this study by analysing galaxies in six LoCuSS clusters at z=0.2 revealing a "slow-then-quick" quenching process for infalling galaxies. These observational results are compared to cosmologically zoom-in simulations coupled to nebular-emission models by Hirschmann+17 to trace the impact of various star formation histories of cluster galaxies. Altogether we investigate quantitatively the physical processes of the transition of active galaxies into passive cluster members.
Cambridge Photometric Calibration Server 2.0
Zielinski, Pawel
Transient astrophysical events, e.g., supernovae, microlensing events, often require immediate follow-up observations soon after their discovery. With dozens of new alerts every day it is essential to carefully select those, which are of highest scientific interest or are rare examples of events. Early multi-band photometry informs on how an event develops in brightness and colour, allowing for early characterisation and helping decide on further follow-up observations.The Cambridge Photometric Calibration Server (CPCS) has been designed to respond to the need of automated rapid photometric data calibration and disemination for transient events, primarily from Gaia space mission. CPCS is in operation since 2013 and has been used to calibrate around 50 000 observations of hundreds of transients. We will present the status of the tool and demonstrate its newest version, which is enhanced with build-in profile photometric measurement. The Server is able to combine data from multiple telescopes and is intended to provide science-ready photometric data within minutes from observations.
Star Formation Science Highlights from the Airborne Infrared Observatory SOFIA
Zinnecker, Hans
SOFIA, short for Stratospheric Observatory for InfraredAstronomy, has been observing the mid- and far-infrared skyin both the northern and the southern hemisphere since 2011,with dedicated broad-band cameras (FORCAST, HAWC+) andhigh-resolution spectrometers (GREAT, FIFI-LS, EXES). In this poster, we summarize some of the highlights of theseobservations:1) imaging: -- IRc4, a new luminous protostar in the Orion BN/KL region -- eps Eri, a solar system analog with a spatially resolved debris disk -- the Rho Oph dust cloud and the geometry of its magnetic field2) spectroscopy: -- infall motion (collapse) of an ATLAS-GAL protocluster cloud -- a far-infrared luminosity outburst (factor 10) and light echo due to episodic disk accretion in the massive YSO S255-IRS3 -- water in absorption (6.1 mu ground state ro-vib transition) in the AFGL 2591 protostellar envelopeSOFIA also discovered a number of new light molecules in the ISMand in protostellar envelopes, such as SH, OH, OD, H2D+, HD2+, all in absorption against strong far-IR continuum sources(eg. IRAS 16293 or W49N).SOFIA is currently the only far-IR Observatory for years to comeand is open world-wide to Cycle 7 proposals (deadline 7 Sept 2018).
An idea for a SOFIA nearby galaxies far-IR legacy survey
Zinnecker, Hans
In this poster, we propose a combined large (~100 hr)continuum and line emission far-IR legacy survey of nearby star forming galaxies with the SOFIA air-borne NASA/DLR Observatory (2.5m telescope), using the far-IR camera HAWC+ and far-IR integral fieldspectrometer FIFI-LS, with a FOV of 1' or more(in the case of HAWC+).We first select a distance-limited sample of 50-100 nearbystar forming galaxies (10-40Mpc), each of which fit intothe FOV and are, for scheduling, conveniently distributed all over the sky.We will study the spatial distribution of far-IRdust emission at several HAWC+ far-IR wavelengths (53, 89, 154, 214 micron) and will measure their total far-infrared luminosities (a proxy fortheir total star formation rates). In addition,we will also map, with HAWC+, the multi-wavelength (53 and 89 micron) spatial distributionof polarized dust emission due to aligned dust grains,allowing us to infer the large-scale orientation ofmagnetic fields in these galaxies at 5-10" spatial resolution.(Herschel could not do this, as neither PACS nor SPIRE hada polarimetric mode).In the second part of this proposal, we will use FIFI_LSto measure the integral flux of the most important 158 micron [CII]ISM gas cooling line of these same star forming galaxies.We can then deduce the far-IR line-to-continuum luminosityratio of L_[CII]/L_FIR and can check to what extent is itindeed universal (of the order of 1%). This in turn is atest of the hypothesis that the [CII] luminosity is agood reliable star formation rate indicator, as is widely(but blindly) assumed in the high-z star formation community.Such an investigation of the "local truth" would seem to behighly desirable before accepting far-reaching extrapolationsof early universe star formation rates based on the detection ofhigh-redshifted [CII] emission with submm telescopes(e.g. with ALMA and NOEMA).We invite interested far-IR/submm astronomers to join and helpwith this SOFIA legacy proposal (new deadline: 7 Sept 2018).
How galactic feedback regulates the angular momentum content of haloes and their galaxies
Zjupa, Jolanta
Recent cosmological simulations have shown that feedback from supernovae and AGN is the crucial ingredient to produce a galaxy population with realistic sizes and morphologies. The mechanism through which galactic feedback regulates the AM content of haloes and their galaxies was however yet unknown. We employ a galaxy population form the cosmological hydrodynamical simulations Illustris and IllustrisTNG (TNG) to answer this question with a statistical ansatz. We have derived the AM properties for more than 300.000 haloes and their galaxies yielding an unprecedented statistics, and find the AM of the baryons at z=0 to be enhanced by a factor of ~2 compared to the dark matter in both simulations exhibiting a realistic galaxy population. Thereby, Illustris and TNG make use of different subgrid models for feedback physics which allows us to identify the mechanism driving baryonic AM enhancement that is independent of the detailed feedback prescription and thus of physical nature. Comparison of the Illustris and TNG simulation results shows that the specific feedback model regulates the relative strength of galactic winds launched by supernovae and AGN feedback at a given halo mass. However, taking the population as a whole, galaxy haloes lose on average _x005F~40% of their gas content due to feedback driven outflows independent of the employed feedback model. I will show how this can be used to estimate the enhancement in baryonic spin and that this single mechanism is sufficient to explain the resulting amount of AM in the baryonic component of a whole galaxy population, as measured in Illustris and TNG. I will expand on how we aim to confirm this mechanism, and also on our next steps to better understand the role of feedback in regulating the AM content of individual galaxies with specific morphologies.
Optical monitoring of a sample of FR II-type QSO
Zola, Staszek
We will present results derived from a monitoring program of a sample of FR-II type radio quasars.The variabilities detected in their densly covered light curves, that have being gatheredover a period of more than 9 years, are analyzed with statistical methods (WWZ, DFT andthe structure function). Based on our findings we will draw preliminary conclusions on theproceses that may cause flux variations in the optical band.
Sunspot observations in the beginning of the seventeenth century
Zolotova, Nadezhda
One of the early sunspot observers of the sunspots using a telescope was Galileo Galilei. Here, we analyse his original manuscripts, which were not mentioned in the Hoyt and Schatten database of the sunspot group numbers. Handwritten documents contains 107 drawings of the solar disc in 1612 and 1613. Several drawings were later printed in the book Istoria published in 1613. Another source of data on sunspots on the eve of Maunder minimum are the drawings in the 1630s made by Pierre Gassendi. First of all, these observations intrigue the solar community by the fact that even before the start of the Maunder minimum the spots tend to appear in the southern hemisphere. We present the preliminary results on the extraction of the number of groups, their heliographic positions and area. We also discuss discrepancies between manuscripts and published books.
Centennial cycle of the north-south asymmetry in the solar magnetic field
Zolotova, Nadezhda
Various solar phenomena are north-south asymmetric in amplitude and phase. We analyzed the position of the heliospheric current sheet (HCS) relative to the ecliptic plane and sunspot areas over 19th and 20th centuries. We found that both variables experience simultaneous changes in terms of dominating hemisphere around the solar activity cycles 14-15 and 19-20. The same changes occur in the differential rotation velocity. We came up with the conclusion that the north-south asymmetry of the analyzed phenomena has the same global source and varies regularly with nearly centennial periodicity.
Collisional excitation of highly-excited water lines
Zóltowski, Michal
Water is one of the most abundant molecules in the interstellar medium. During the early phases of star formation, water plays an important role in the gas cooling and is a useful probe of gas dynamics. Here, we present quantum-chemical calculations of collisions of water with molecular hydrogen for gas temperatures as high as 1500 K. Our calculations provide insight into water excitation at the wavelength range that will be observed by the MIRI instrument on board the James Webb Space Telescope.
LAMOST OBSERVATIONS IN THE KEPLER FIELD. II. DATEBASE OF THE LOW-RESOLUTION SPECTRA AFTER THE SECOND ROUND
Zong, Weikai
The LAMOST-Kepler (LK-) project was initiated to use the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) to make spectroscopic follow-up observations for the targets in the field of the Kepler mission. The Kepler field is divided into 14 subfields that are adapted to the LAMOST circular field with diameter of 5 degrees. During the regular survey phase of LAMOST, the LK-project took data from 2012 June to 2017 June, covered all the 14 subfields at least twice. In particular, we describe in this paper the second Data Release of the LK-project, including all spectra acquired through 2015 May to 2017 June together with the first round observations of LK-project from 2012 June to 2014 September. The LK-project now counts 227 870 spectra of 156 390 stars, among which we have derived atmospheric parameters (log g, Teff and [Fe/H]) and heliocentric radial velocity, RV, for 173 971 spectra of 126 172 stars. These parameters were obtained with the most recent version of the LAMOST Stellar Parameter Pipeline v 2.9.7. More than one third, namely 58 805 targets, are observed both by LAMOST and Kepler telescopes. These spectra, establishing a mass spectroscopy library, will be useful for the entire astronomical community, particularly for planetary science and stellar variability on Kepler targets.
Morocco Oukaimeden Sky Survey Telescope in the top 10 since 2012
Zouhair, Benkhaldoun
With more than 1.5 million astrometric measurements sent to MPC, 6 NEO and 4 comets, the MOSS (Morocco Oukaimeden Sky Survey) telescope at the Oukaimeden Observatory (IAU code J43) is one of the most successful asteroids program in the world behind the NASA funded American surveys (PanSTARRS, CSS, Spacewatch…). The 1073 rediscoveries credited to MOSS team on Feburary 3 2018 place the Oukaimeden Observatory at the 26th place for all time since the discovery of Ceres in 1801.Morocco Oukaimeden Sky Survey is the most prolific amateur program in the world. During the period 2011-2017 the MOSS 50 cm F/D=3 scope has taken more than 300k images for an accumulate size of more than 5 Tbit of data. This data ought to be check with automatic process for extracting new supernovae, novae and variable stars.Located in the High Atlas mountains in Morocco, the Oukaimeden observatory benefits of good observing conditions: the median number of observable or clear night is around 230 each year. A weather station is installed in situ since 2010 and the seeing is measured continually since 2015. The median zenith seeing is around 1.0 arcsec.We propose here to describe the characteristics of the instrumentation involved, but above all, the observation and data reduction strategy that made this success possible.
Light propagation in the Solar System
Zschocke, Sven
We report on recent advancement in the theory of light propagation in the Solar System aiming at the sub-micro-arcsecond level of astrometric accuracy. Trajectories of light signals in the gravitational field of N Solar System bodies in arbitrary motion are determined in the post-Newtonian (PN) approach. In line with the IAU recommendations, harmonic coordinates are used and the gravitational fields of the Solar System bodies are expressed in terms of their intrinsic mass-multipoles and spin-multipoles, allowing for arbitrary shape, inner structure, oscillations, and rotational motion of these bodies. In particular:_x005F (1) The solution for light rays in 1.5PN approximation is obtained in the gravitational field of N arbitrarily moving bodies of arbitrary shape, inner structure, oscillations, and rotational motion._x005F (2) The solution for light rays in 2PN approximation is obtained in the gravitational field of one arbitrarily moving pointlike body.
Brightness variations of young Sun-like stars from ground-based and space telescopes
Zsidi, Gabriella
Young stellar object are stars in the early stage of their evolution. They often show photometric variability, which may be due to non-steady accretion from the circumstellar disk onto the star, but other physical processes, such as rotating cold spots or the transit of a dust cloud can also change the observed brightness of the star. Variability is well examined at optical wavelengths, but nowadays more and more infrared data are available as well. The wavelength dependence of the variability carries information on the physical cause of the changing brightness. Here, we examine seven T Tauri-type stars known for their large amplitude variability selected from the Campaign 13 field of the Kepler K2 mission. We complemented the K2 light curves by nightly multi-filter optical monitoring observations made with the 90 cm Schmidt telescope of Konkoly Observatory. In order to extend our wavelength coverage, cadence, and temporal coverage, we complemented these data with 3.6 and 4.5 micrometer infrared photometry obtained with a nightly cadence with the Spitzer Space Telescope. We constructed K2, B, V, R, I, and infrared light curves and investigated the brightness and color variations of our targets, to establish the origin of the variability and separate the different physical effects.
NOC activities at Nicaragua
Zuniga Hernández, Emilio
The poster present the NOC activities at Nicaragua
High-mass X-ray Binaries: Evolutionary Population Synthesis Modeling
Zuo, Zhao-Yu
Using an evolutionary population synthesis code, we modeled the universal, featureless X-ray luminosity function of high-mass X-ray binaries (HMXBs) in star-forming galaxies. We put constraints on natal kicks and super-Eddington accretion factor, and presented the detail properties of modeled HMXBs, which may be investigated further by future high-resolution X-ray and optical observations.
Constraints from luminosity-displacement correlation of high-mass X-ray binaries
Zuo, Zhao-Yu
We have modeled the luminosity-displacement correlation of high-mass X-ray binaries with an evolutionary population synthesis code. Detailed properties including offsets of simulated HMXBs are presented under both common envelope prescriptions usually adopted, i.e., the αCE formalism and the γ algorithm. We suggest that the distinct observational properties may be used as potential evidence to discriminate between these two types of models.