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="">
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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="">
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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="">
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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="">
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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