Oral Contributions Abstracts
Differential Astrometry with Gaia simulated observations
Abbas, Ummi
We will describe the method of differential astrometry in defining a small field inertial differential astrometric reference frame at the micro-arcsecond level of precision using simulated observations of stars by Gaia.Different systematic effects due to physical effects such as those relativistic in nature, those due to the star's proper motion and the scanning motion of the satellite, along with instrumental effects due to the geometric instrument model, all affect the accuracy of such a definition. Over short intervals of time spanning several spin periods of Gaia we will show the reliability in modeling and estimating such systematics and in establishing the stability of the differential reference frame down to the micro-arcsecond level.This method has far-reaching applications in the study of key Gaia science cases over different characteristic time scales such as relativistic deflection of light experiments, extrasolar planets, and microlensing events. We will provide illustrative examples of these scientific applications.
Outbursts of young Sun-like stars may change how terrestrial planets form
Abraham, Peter
While the Sun is nowadays a quiet and well-balanced star, in its first few million years it might have been often out of temper, like those young low-mass stars which episodically undergo unpredictable outbursts. The prototype of one of the two classes of young erupting stars, EX Lupi, had its historically largest outburst in 2008. It brightened by a factor of 30 for six months, due to elevated accretion from the circumstellar disk on to the star. Our group observed the system during the outburst, and discovered the crystallisation of amorphous silicate grains in the inner disk by the heat of the outburst (Ábrahám et al., Nature, 2009). Our mid-infrared monitoring of the freshly produced crystals revealed that their emission in the inner disk quickly dropped already within a year after the outburst (Juhász et al. 2012). Here we report on new observations of the 10 micrometer silicate feature, obtained with the MIDI and VISIR instruments at Paranal Observatory, which demonstrate that within four years practically all forsterite disappeared from the inner disk. We attempt to model this process by a stellar wind that transports the crystals from the terrestrial zone to outer disk regions where comets are supposed to assemble. We also performed ALMA observations of a set of key molecular lines, whose intensity - according to our chemical evolutionary models - should reflect how chemistry changed in the disk due to the extra irradiation provided by the outburst. Since the eruptions of EX Lup seem to be recurrent, we speculate that the early Sun also experienced similar brightenings, and the forming planetary system might have incorporated some of the mineralogical and chemical yields provided by the outbursts. EX Lup, as a proxy for the proto-Sun, may be a telltale object to help to understand the origin of molecules and minerals we routinely encounter on planet Earth.
TOWARDS ASTROBIOLOGICAL EXPERIMENTAL APPROACHES TO STUDY UV SURFACE ENVIRONMENTS: FROM THE EARLY SOLAR SYSTEM TO EXOPLANETS
Abrevaya, Ximena C.
To determine the conditions about the existence and emergence of life in the universe, it is essential to study stellar radiation which itself can be a constraint for life development. Particularly, UV radiation wavelengths (200-400 nm) can reach the surface of the planets. Even though several studies have analyzed the UV surface environments on planetary bodies considering UV radiation as a limiting factor, this has only been approached partially from a theoretical point of view and experimental approaches are missing so far, e.g.: biological effects are based on theoretical calculations. All these points can be addressed more accurately through an interdisciplinary approach. To this end we carry out two international collaborations by combining a team of experts in astrophysics, microbiology, photobiology and cosmochemistry: The BioSun project and the EXO-UV project whose aim is to analyze the influence of stellar UV radiation on life in a comprehensive way. Our approach includes: (i) astrophysical studies focused on the characterization of the radiation environments by using observational data and considering potential atmospheric compositions; (ii) 1-D radiative transfer modeling of the planetary atmosphere; (iii) simulation of these UV environments in laboratory experiments to study the effects of radiation on life. Within these projects we aim to to study the conditions for the origin, evolution and habitability of life on the early Solar System as well as in other planetary bodies. During this talk I will show the first advances of this collaboration and the first results of the experimental simulations of these UV radiation environments in laboratory experiments by using radioresistant microorganisms.
Publication Changes during the IAU History
Abt, Helmut A.
During the 100 years of the International Astronomical Union, the worldwide astronomical publications have grown exponentially, converted almost entirely to English, and changed format from observatory publications to journals to online publications. Observatory publications have nearly disappeared in usefulness for research.
The dwarf galaxy population as revealed by ALFALFA
Adams, Elizabeth
The ALFALFA HI survey is a blind neutral hydrogen survey of nearly 7000 square degrees of extragalactic sky with ~31,000 extragalactic detections. The combination of sensitivity and large sky coverage of ALFALFA has enabled the detection of difficult to observe low mass galaxies in large numbers, including dwarf galaxies overlooked in optical surveys. Three different, but connected, studies of dwarf galaxies from the ALFALFA survey are of particular interest: SHIELD (Survey of HI in Extremely Low-mass Dwarfs), candidate gas-rich ultra-faint dwarf galaxies, and field gas-rich ultra-diffuse galaxies.SHIELD is a systematic multiwavelength study of all dwarf galaxies from ALFALFA with M_HI < 10^7.2 Msun. The star formation, gas, and dark matter properties of the first 12 galaxies have been studied in detail, and an investigation of the full sample of 82 galaxies is underway. The low metallicity star-forming galaxy, Leoncino, was identified through this study. Candidate gas-rich ultra-faint dwarf galaxies extend the dwarf galaxy population to even lower masses. These galaxies are identified as isolated HI clouds with no discernible optical counterpart but subsequent high resolution HI imaging with WSRT and deep optical imaging with WIYN/(p)ODI reveal that many are extremely faint, gas-dominated galaxies. Leo P, discovered first as an HI detection, and then found to be an actively star-forming galaxy, bridges the gap between these candidate galaxies and the SHIELD sample.A population of field gas-rich ultra-diffuse galaxies was identified in the ALFALFA survey; their optical counterparts in SDSS are too faint to be trusted without the additional information of the HI detection. The HI kinematics indicate these are hosted by dwarf galaxy dark matter halos, possibly with a higher than average spin. Coma P, with a peak surface brightness of ~26.4 mag arcsec^-2 in g', demonstrates the sort of extreme low surface brightness galaxy that can be discovered in an HI survey.
Reports Commission B6: Important photometric and polarimetric topics
Adelman, Saul
TBA
The ASTRA Spectrophotometric Telescope
Adelman, Saul
The first scientific observations from the ASTRA Spectrophotometer and its 0.5-m automated telescope should be available this summer. ASTRA should observe stars whose declination range is at least +85° to -28°. The instrument will obtain flux calibrated spectra at classification dispersion. From these fluxes studies of the continuum spectra can be performed and the strongest lines can be measured. A small CCD camera finds and centers the target and then guides on the zeroth order spectrum. The spectrophotometer uses both a grating and a cross-dispersing prism to produce spectra from both orders simultaneously. In an hour exposure time the system should obtain S/N = 200 observations of stars as faint as 9.5 mag. Vega will require about 25 seconds for the exposures and readout of both orders. The telescope will find its next target in less than a minute. The square 30 arc second sky fields for each order do not overlap. The resolution is 7 Å in second and 14 Å in first order. The wavelength range is approximately ??3300-9000. We initially will use about 10 minutes/hour to observe Vega and secondary standard candidates. Our scientific CCD is electronically cooled to -50° C with a water recirculation system heat sink. The same 4° C recycling water system provides thermal stabilization of the instrument. The ASTRA telescope is rocked to expose the image from the top to the bottom of the entrance aperture. Three LINUX servers will have databases of ASTRA observations. ASTRA can observe standard stars at a regular rate throughout the night, any accessible target at a given time, variable stars, slow moving targets, and targets of opportunity. ASTRA will produce considerable high-quality data: of order 15000 standard stars and 40000 target objects per year. The four P. I.’s will operate the system. Due to the large volume of data expected each year, they will work in collaboration with other astronomers to make the best scientific usage of ASTRA.
Optical rest-frame spectroscopy to study the filaments and galaxy clusters outskirts at z~1
Afonso, Ana
The VIMOS Spectroscopic Survey of a Supercluster in the COSMOS field (VIS³COS) aims to accurately map in 3D a superstructure at redshift between 0.8 and 0.9, which contains 3 massive X-rays confirmed clusters (Finoguenov et al., 2007) and shows a striking filamentary structure in the HiZELS Ha survey at z=0.84 (Sobral et al., 2011). The ~500 spectroscopic confirmed members probe a wide range of densities and environments (from fields to the clusters outskirts and rich groups). The unprecedented nature of this survey (Paulino-Afonso et al., A&A submitted) allows a detailed study of the evolution of these objects across cosmic time as well as link observations and theories in and around cluster galaxies by e.g. characterizing the star formation activity and the ionized gas properties of galaxies in a large density range. I will present the observed depression of star formation and local changes on electron densities with the environment (depending on galaxy stellar mass) at z~1, where most changes occur in cluster outskirts and filament-like regions. At this epoch, the intense life in the cluster galaxies suburbs seems to provide essential clues on the physical mechanisms that can affect the shape of galaxy clusters and their understanding.
Historical Meteor outbursts and its parent comets
Ahn, Sang-Hyeon
Comets emit debris at their perihelion passage, and such debris initially form meteor streams. When the Earth encounters with those streams during its revolution, the cometary debris fall into the Earth's atmosphere and form a meteor showers. If the encounter were made with a fresh meteor-stream, a large number of meteors occur intensively in a short time scale, which are called meteor outbursts. This astronomical phenomena are so brilliant that they have attracted human interest from the early time of history to be recorded in historical archives._x000D_ Usually meteors form at the altitude of 70-100km, while a small fraction of them survive to fall to the ground and found to be called meteorites. These have been witnessed and collected to be left in history books. A little bit larger impact formed craters on ground. Impact craters on the surface of the Earth, as well as on the Moon, give us precious data to investigate the solar system activity from tens of thousands years ago to hundreds of millions years ago. Likewise, Historical records can give us unique chance investigate the thousand-years-term variations of meteor activity in the Solar system, which must be closely related with the orbital variations of minor bodies in the Solar system._x000D_ Here in this presentation, I will report the results for meteor outbursts identified from historical archives all around the world throughout the human history, and additionally historical records of meteorites written in Korean royal chronologies. Due to the precession of parent comets, the appearance dates of meteor outbursts also show temporal variations. From these observations, we can pick out at least 12 meteor outbursts that can be identified with their own parent comets. In addition, a couple of Korean records for meteorites give detailed information to be analyzed physically to give us a hint for their type.
Chemistry in Protostellar Cores and Forming Disks
Aikawa, Yuri
Protostars are formed by the gravitational collapse of dense coloud cores. If the angular momentum of a parental core is conserved, a rotationally supported disk of radius \sim 100 au is expected to form, as well. Angular momentum could be, however, extractedd from the system via disk winds/outflows and magnetic fields. ALMA now provides subarcsecond (\lesssim 100 au in the nearby star forming region) image of the central region of protostellar cores, revealing infalling gas and forming disks around several class 0-I protostars. Various molecular lines, including complex organic molecules (COMs) are also detected in this central region. Since the abundances and chemical timescales of molecules sensitively depend on the temperature and densities, spatial distributions of emission lines vary among species, and could be used to probe the circumstellar structures. I will review recent progresses in the study of protostellar cores and forming disks, with emphasis on chemical signatures.
How publication and peer review are evolving in the life sciences: implications for astronomy
Allen, Liz
Publication has traditionally been defined to include functions such as registration, certification, dissemination and archiving. However, with the growing number of articles being published, it is becoming increasingly important to have filtering and selection, and to provide routes and metrics for behaviours to be recognised and rewarded.This session will discuss the limitations and challenges facing traditional journal-level article selection, and make the case for why the current peer review paradigm needs to be separated into two discrete stages – technical peer review and peer review for interest/impact.The value of a piece of research can take many forms. Currently assessment of impact generally focuses on novelty; however, this assessment needs to take a more nuanced approach to evaluating an article’s potential contribution, from generating robust data for future research, to providing a new resource to support teaching and training for the next generation.Researchers are uniquely placed – while they are writing, publishing and reviewing literature – to identify what look to be useful pieces of research that have value for their own research, the broader scientific community, and for society and all its consumers of research.Using the example of F1000Prime in the life sciences, this presentation discusses the establishment of a journal-agnostic route for qualitative research evaluation in astronomy, returning control of research evaluation to the research community.
Strategies for flux calibration in massive spectroscopic surveys
Allende Prieto, Carlos
Optical large-scale medium-resolution spectroscopic surveys such as SDSS, LAMOST, DESI, WEAVE or 4MOST are subject to constraints that limit the choice of flux calibrators, and the attained precision. The use of optical fibers, a large but limited field of view, the tiling strategies and tight schedules, are all factors that call for a careful evaluation of the flux calibration procedures. These and other issues such as the current state of the art for model atmospheres and model spectra, or the current knowledge available for potential calibration targets, must be considered and will be discussed in this presentation.
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.
The International Terrestrial Reference Frame: ITRF2014 and future plans
Altamimi, Zuheir
We review the progress and continuous improvements being made since more than 30 years in the determination and development of the International Terrestrial Reference Frame (ITRF). We evaluate the precision and accuracy of the main geodetic and geophysical products of the latest ITRF release, namely the ITRF2014, using some key performance indicators. These indicators include the evaluation of the performance of the annual and semi-annual signals and Post-Seismic Deformation (PSD) models: the two main innovations introduced in the ITRF2014 elaboration. A special emphasis will be given to discuss the Earth Orientation Parameters (EOPs) resulting from the ITRF2014 combination. We evaluate in particular the impact of estimating periodic signals on the EOPs, versus applying a non-tidal atmospheric loading model. We discuss the level of agreement between techniques in terms of Earth Orientation Parameters, but also of the frame physical parameters (origin and scale). A short discussion on the transformation between the ITRF and the ICRF will be made in the light of the ITRF2014 EOP results. Main conclusions will be drawn to guide and improve our analysis and combination strategy for future ITRF releases.
Age gradients in the nearby star formation regions: the Blue Streams
Alves, Joao
In this talk, I will summarize recent results in the literature on age gradients in nearby star-forming regions and report on the discovery of a 300 pc long, dynamically cold stellar structure comprising hundreds of massive OB stars towards Orion. We measure a clear age gradient along this long structure, from young-to-old as one moves away from the Orion clouds, suggesting a common origin. Rather than expanding, the Orion OB I association seems to be streaming as part of a much larger stream. Our results confirm the existence of Blue Streams (Bouy & Alves 2015), large co-moving groups of young stars, and suggest that star formation and dispersal processes are more coherent than previously thought. I will briefly describe possible scenarios for the origin of the Blue Streams and their impact the local neighborhood.
The Initial Mass Function in the ELT era
Alves, João
The stellar initial mass function (IMF) is one of the main pillars of modern astrophysics. Although taken as a universal constant, there has been in the recent literature tantalizing evidence for drastic variations. Is the stellar IMF approximately constant across the local universe? The advent of the ELTs will allow one to probe the local universe for critically needed resolved IMF studies of various stellar populations. Spectroscopy, even from the ELTs, will be observationally inefficient to allow for the characterization of a sufficient number of sources, so our ability to measure the IMF in the local universe depends critically on our ability to constrain masses from photometric data. In a recent paper (Ascenso 2018), we showed that this can be done reliably even with near-infrared data alone, circumventing the need for the wide wavelength coverage typically necessary to build SEDs. In this talk, we will present results from an investigative study for resolved IMFs in the local universe done with SIMCADO (the ELT-MICADO simulator (Leschinski et al. 2018)). Although ELT PSFs make life very difficult, we conclude that 1) ELT-MICADO can get well into the Brown dwarf regime (>0.01Msun) for all clusters within 8kpc of the Sun, 2) It will just miss out on the BD knee in the LMC (>0.1 Msun), but it will catch the true structure of the 0.5 Msun knee, and 3) densities of ~1000 stars/arcsec^2 are easily resolvable while 5000 stars/arcsec^2 is possible only if we have good knowledge of the PSF. The latter is equivalent to every star in an Arches-like cluster at a distance of the LMC. An ONC-like cluster would be fully resolvable (assuming no extinction) in Leo I Dwarf (220kpc). In the LMC, meaning MICADO can basically resolve out all the stars in every YMC listed in Portegies-Zwart 2010. We will end presenting the distance limit for resolved IMFs for a broad range of conditions.
The JWST near-infrared spectrograph NIRSpec
Alves de Oliveira, Catarina
The near-infrared spectrograph NIRSpec is one of four instruments aboard the James Webb Space Telescope (JWST). NIRSpec is developed by ESA with AIRBUS Defence & Space as prime contractor. It offers seven dispersers covering the wavelength range from 0.6 to 5.3 micron with resolutions from R~100 to R~2700. Using an array of micro-shutters, NIRSpec will be capable of obtaining spectra for over 100 objects simultaneously. It also features an integral field unit with a 3 by 3 arcseconds field of view, and various slits for high contrast spectroscopy of individual objects and time series observations, including those of transiting exoplanets. We will provide an overview of the capabilities and performances of the three observing modes of NIRSpec, and how these are linked to the four main JWST scientific themes.
Stellar populations of high-z protoclusters from the CARLA survey
Amodeo, Stefania
Studying the evolution of galaxy properties in clusters is important to test theories of galaxy formation and the role of the environment on galaxy evolution. We will present results on the stellar populations of galaxies in confirmed dense structures at z>1.4. At this epoch, clusters are still in the process of forming and most of the assembly is ongoing, while the cosmic star formation rate density peaks in the history of the Universe (Madau & Dickinson 2014). The Spitzer/IRAC survey CARLA (Clusters Around Radio-Loud AGN) has targeted high-z radio-loud AGNs, which are known to reside in dense environments (Wylezalek et al. 2013), and selected the 20 richest fields to be followed-up with HST, from which 16 structures in the range 1.4 < z < 2.8 were spectroscopically confirmed (Noirot et al. 2018). Optical (i-band) imaging for eight of these targets have also been obtained with the Gemini and William Hershel telescopes (Cooke et al. 2015). This is the largest sample of protoclusters at z>1.5 at present. We will discuss the colour-magnitude relation of the spectroscopically confirmed galaxies and of the galaxies selected by their Spitzer colours ([3.6] - [4.5])AB > - 0.1. We will compare our data to different stellar populations models and discuss the presence or absence of a red-sequence, the fraction of star-forming and quiescent galaxies from rest-frame UVJ colors, as well as the dependence of the galaxy properties on the proximity to the AGN. This study, done for the first time on an homogeneous statistical sample of spectroscopically confirmed clusters at high redshift, is ideal to investigate the quenching mechanisms in dense environments.
The evolution of the Milky Way's radial metallicity gradient as seen by APOGEE, CoRoT, and Gaia
Anders, Friedrich
The time evolution of the radial metallicity gradient is one of the most important constraints for Milky Way chemical and chemo-dynamical models. In this talk we review the status of the observational debate and present a new measurement of the age dependence of the radial abundance gradients, using combined asteroseismic and spectroscopic observations of 418 red giant stars located close to the Galactic disc plane (6 kpc < RGal < 13 kpc). The radial iron gradient traced by the youngest red-giant population (-0.058 +- 0.008 +- 0.003 dex/kpc) reproduces the results obtained with young Cepheids, while for the 1-4 Gyr population we obtain a slightly steeper gradient (-0.066 +- 0.007 +- 0.002 dex/kpc). For older ages, the gradient flattens again to reach values compatible with zero at around 10 Gyr. We compare our results to state-of-the-art chemo-dynamical Milky Way models and recent literature results obtained with open clusters and planetary nebulae. We will also present first results from APOGEE+Gaia-DR2-derived ages of turn-off stars.
Recovering and discovering clusters and moving groups with Gaia
Anders, Friedrich
Gaia DR2 will likely increase the known Galactic star cluster population by orders of magnitude. Using Gaia DR2, I will demonstrate the usefulness of a combined dimensionality reduction/clustering approach to detecting groups of comoving stars, and estimate the number of new clusters that may be discovered with DR2 using different statistical methods. I will also highlight the prospects of using combining spectroscopic survey data with Gaia DR2 for chemical and chemo-kinematical tagging in the Galactic disc.
IAU General Secretary 1997-2000
Andersen, Johannes
The IAU is an old house, and each of us arrives with our own toolbox, set of skills, and priorities; after several General Secretaries, the house is hopefully in reasonable shape. The IAU General Secretary is in principle responsible for everything, which takes more time than you have. While some tasks appear more important, surprises (like Pluto in 1999) may occur at any moment._x000D_ In my case, I’d like to be remembered for four major initiatives during my term:_x000D_ An IAU policy on Near Earth Objects. None existed before; now NEOs are on the UN Agenda. _x000D_ Proper Terms of Reference for the IAU Minor Planet Centre, including an open data policy. _x000D_ Streamlining the IAU education-like activities – the nucleus of the future IAU Strategic Plan. _x000D_ The new collaboration to award the Gruber Cosmology Prize and the Fellowships. _x000D_ Then there’s always housekeeping and IAU books to do, e.g. giving the Secretariat, the Information Bulletin, and the web page (or the Statutes and By-Laws!) a facelift, but those are minor items.
Accurate Parallaxes of Classical Cepheids: Opportunities and Challenges for the Distance Scale
Anderson, Richard I.
The cosmic distance scale (CDS) is currently undergoing significant renovation thanks to Cepheid parallaxes being measured with 30-100 µas accuracy by Gaia and the Hubble Space Telescope (HST). These extremely accurate parallaxes are expected to significantly improve the calibration of the Leavitt law (period-luminosity relation) and thus play a crucial role for elucidating the nature of dark energy and understanding recently reported tension between the Hubble constant (H0) measured via the CDS and H0 inferred using the Cosmic Microwave Background assuming standard cosmology. H0 tension may point to missing physics in the cosmological model; however, careful analyses must address possible systematics involved in the calibration of the CDS before such a claim can be made. Here we present recent research aimed at unveiling CDS systematics related to classical Cepheids, their companion stars, and their occurrence in clusters. Part one presents a detailed vetting process of high-quality Galactic Leavitt Law calibrators based on an unprecedented catalog comprising of >15,000 precise radial velocity measurements of more than 300 Galactic classical Cepheids. We systematically search for (spectroscopic) binaries that may bias or increase the uncertainty of parallaxes measured using sparse data (HST) or short temporal baselines (Gaia DR2, 22 months). We have thus discovered more than a dozen new binaries and determine upper limits on non-detections in support of the measured parallax accuracy.In part two, we use deep HST imaging of M31 to directly measure the mean photometric bias due to cluster companions on Cepheid-based distances. We quantify the combined H0 bias from close associations (binaries and clusters) to be approximately 0.3% (0.20 km s-1 Mpc-1) for the passbands commonly used. We thus demonstrate that stellar association bias does not explain H0 tension and does not prevent achieving the community goal of measuring H0 with an accuracy of 1%.
Dust Cloud at Mars
Andersson, Laila
Mars has a rich dust environment, including incoming interstellar dust and dust lofted up from the atmosphere. There is no indication that the moons of Mars contribute significantly to the dust environment. The conclusion that some of the observed dust originates from the atmosphere is based on observations of dust plumes with densities up to ~2 #/m3 extending to altitudes of 1000 km. All observations presented here are from electric field instrument measurements, which provide only limited information about dust origins. Further complicating the measurements, the spacecraft frequency moves from high-density plasma to low-density plasma changing the signatures of dust detection. This presentation will discuss how to separate interplanetary dust from planetary dust and present the time variation of the observed dust over the ~4 years of MAVEN spacecraft operation around Mars.
Interstellar Dust Grain Alignment
Andersson, B-G
Of the available probes of interstellar magnetic fields, dust induced dichroic extinction and emission, are the observationally most straightforward, both in terms of facilities and calibration. Its interpretation has, however, long been handicapped by the lack of a quantitative, observationally supported, understanding of the required grain alignment. Over the last decade this deficiency has been remedied, with the establishment, and observational confirmation, of Radiative Alignment Torque (RAT) theory. With our growing confidence of RAT alignment, measurements of dust induced polarization can now not only be used for more reliable characterization of the magnetic field, but also to constrain and probe other characteristics of the environment and the dust. I will review the basics of RAT alignment, some of the empirical support of the theory and some of the new tools for interstellar astronomy made possible by these developments.
Observing Planet Formation
Andrews, Sean
Planetary systems form in the disks of gas and dust that orbit young stars. In the past few years, very high angular resolution observations of disks in nearby star-forming regions have started to uncover some key signatures of the planet formation epoch. This talk will focus on what we are learning about the distribution of disk material on spatial scales of only a few astronomical units, largely based on state-of-the-art measurements with the Atacama Large Millimeter/submillimeter Array (ALMA), and the corresponding implications for the assembly and early evolution of planetary systems.
Astrophysics with Gaia Wide Binaries
Andrews, Jeff
With orbital periods in excess of thousands of years, wide binaries have traditionally been identified by finding common proper motion stars within astrometric catalogs. Using the additional inclusion of parallax measurements, sophisticated Bayesian algorithms designed to mine the first Gaia data release have robustly identified thousands of new wide binaries. Already, we are using this sample to place new constraints on stellar multiplicity, the strength of gravity in the weak acceleration regime, and the potential for chemical tagging to identify unique Galactic subpopulations. The much larger second Gaia data release provides precise proper motions and parallaxes for over 1 billion stars, allowing for the identification of wide binary samples of an unprecedented scale; however coupled with this opportunity is a challenging data science problem requiring modern statistical tools, efficient algorithms, and large computing clusters to accurately classify stellar pairs as wide binaries rather than the chance coincidence of unassociated stars. I will discuss the status of our search for wide binaries within the second Gaia data release, as well as how our resulting samples can help solve several open stellar and galactic astrophysical problems, particularly when our sample is cross-matched with large scale spectroscopic surveys such as APOGEE and GALAH.
Protoplanetary Disks Demographics with ALMA
Ansdell, Megan
TBA
The Characterization and Properties of Earth-like Planets
Apai, Daniel
In this talk, I will review the observational challenges to characterize earth-sized (and possibly earth-like) planets. I will summarize our current knowledge on the properties of the small exoplanet population. I will also discuss how observations with future facilities will be able to further characterize the habitable zone rocky planet population and what observational strategies we may follow in identifying and confirming habitable planet candidates.
ASTROdata Chile: An example initiative using astronomy for economic development in Chile
Arancibia, Demian
The ASTROdata program is funded by the Strategic Investment Fund of the Economy Ministry of Chile, through the Digital Transformation Agency (CTD) of the Chilean Economy Development Agency (CORFO). Its mission is to identify and initiate measures and investments to diversify and grow Chilean economy in Big Data, using our natural resources for Astronomy and the field data-driven challenges. According to the strategy of CORFO and its CTD, the capacity to add data-driven value will be critical for competitive edges across industries over next decade, and a driver for diversification of the Chilean productive matrix. We worked with scientific and industrial communities to facilitate multi-sector agreements about what are our opportunities to achieve this mission. In our first year of work, we produced a high-level system concept that is potentially fit for capacity development, technology transfer and is sustainable from an economic point of view.
Chemistry and binarity in the early Universe: what is the role of metal-poor AGB stars?
Arentsen, Anke
To research the earliest times in the Universe we do not have to go to high redshift. Our Milky Way still hosts remnants from these times in the form of metal-deficient stars, which probably carry the imprint from First Star supernovae. However, if they were born in binary systems, their chemical patterns today can also be influenced by a companion going through an AGB phase. Disentangling these two enrichment scenarios will progress our understanding of both First Stars and AGB star chemistry at extremely low metallicities._x000D_ At the lowest metallicities, the fraction of stars that are strongly enhanced in carbon dramatically increases. These carbon-enhanced metal-poor (CEMP) stars come in two main types: CEMP-s stars show additional enhancement in s-process elements, CEMP-no stars do not and occur at even lower metallicities. CEMP-s stars are thought to have received their carbon and s-process elements in mass-transfer from an AGB companion that has evolved earlier. This has been supported by radial velocity monitoring (e.g. Hansen et al. 2016a) which found many (but not all) of these stars to be in binaries. The CEMP-no stars - of which the majority show no velocity variations - would instead reflect the chemistry of their birth gas cloud._x000D_ Although CEMP-no stars are not typically in binary systems, some of them do show radial velocity variations consistent with an unseen companion. This provokes the question if some extremely low-metallicity AGB companions (currently white dwarfs) could have polluted their atmospheres. In this presentation I will focus on the results of a large extension of our radial velocity monitoring program for CEMP-no stars. Compared to earlier work (Starkenburg et al. 2014; Hansen et al. 2016b), the number of known CEMP-no binaries has now more than doubled. An interesting pattern starts to emerge, raising questions about the origins of CEMP-no stars and their possible relation to (extremely metal-poor) AGB stars.
The future of the International Schools for Young Astronomers
Aretxaga, Itziar
The 5-decade old ISYA program is evaluated in the context of the experienced gathered in the field: 41 schools organized in 27 countries with a grand total of ~1400 students to date. In the new era of fast internet connectivity, social media, virtual networks, big public surveys and machine learning, the value of face-to-face graduate tuition for regions with limited up-to-date astrophysics research is presented, together with the plan to develop the IAU program into the next decade.
The future of the International Schools for Young Astronomers
Aretxaga, Itziar
The 5-decade old ISYA program is evaluated in the context of the experienced gathered in the field: 41 schools organized in 27 countries with a grand total of ~1400 students to date. In the new era of fast internet connectivity, social media, virtual networks, big public surveys and machine learning, the value of face-to-face graduate tuition for regions with limited up-to-date astrophysics research is presented, together with the plan to develop the IAU program into the next decade.
Abundances of C, N and O in AGB Giants and Model Atmospheres
Aringer, Bernhard
Atmospheric models of AGB giants are usually calculated with a scaled solar chemical mixture, except for carbon and maybe some s-process elements. However, due to the combination of nuclear processes in their interior and dredge-up events, also the surface abundances of nitrogen and oxygen might be significantly altered in those objects. We have produced a large number of C and M-type COMARCS models, where different C, N and O abundances are taken into account. Based on these computations we discuss the corresponding effects on synthetic spectra and photometry of individual stars, as well as possibilities to include them in population synthesis models for galaxies. We will for example show that for photometric studies it should be enough to consider the metallicity and [C-O] values of single objects.In addition, we discuss the possibilities of measuring an enhancement of oxygen or nitrogen, as well as the [C-O] or C/O values from a theoretical point of view, demonstrating the importance of a consistent treatment of opacities in the models and spectral synthesis and investigating the uncertainties connected to stellar parameters, dust obscuration, pulsation and massloss. It will be shown that with the models available today accurate abundance determinations are only possible for warmer and less pulsating AGB giants.
The Maunder minimum of solar activity as documented by historical sunspot observations
Arlt, Rainer
A period of very low solar activity in the 17th century was identified already 130 years ago from the inspection of historical sunspot observations. The minimum lasted from about 1650 to 1710. This talk will give an overview of our present knowledge of these observations and the interpretation of them. Physical quantities can actually be derived from the drawings of the solar disk. The differences in behaviour of the solar cycle from today may be the key to understand the mechanism behind the solar magnetic variability, the solar dynamo.
Large-scale mass distribution in the IllustrisTNG simulation
Artale, Maria Celeste
We explore the large-scale spatial distribution and physical properties of gas, metals, and ions in the cosmological hydrodynamical simulation IllustrisTNG. The aim of this work is to investigate the so-called missing baryon problem through the analysis of one of the state-of-the-art hydrodynamical cosmological simulations. IllustrisTNG includes an updated scheme for galactic winds, and a new kinetic black hole feedback model for the low accretion state. We compare our findings with those from Illustris simulation and observational data.
The role of dwarf galaxies from the peak epoch of cosmic star formation to the epoch of reionization
Atek, Hakim
Thanks to a major progress in observing facilities and numerical simulations, there is now a growing interest in the population of dwarf galaxies at high redshift, which play a central role in various studies across cosmic time, since they are the most representative objects of the galaxy population. Such importance is based on their contribution to the star formation history of the Universe, their different physical properties and time evolution compared to their massive counterparts, and their dominant contribution to the ionizing background at the epoch of reionization. In this talk, I will summarize our current views on the low-mass galaxies at redshifts z>1 based mainly on NIR spectroscopy from ground- and space-based observations and gravitational lensing that allowed to study galaxies down to stellar masses of 10^7 - 10^8 solar masses. At very high redshift, the very steep faint-end of the UV luminosity function observed at z>6 suggest that faint galaxies probably played a major role in the reionization process. I will discuss the great progress made during the past few years thanks to gravitational lensing, and the routes to move forward to detect a potential turnover of the UV LF, where cosmological simulations predict suppression of the star formation activity in the smallest dark matter halos.
Angular momentum and the evolution of disc galaxies
Athanassoula, Lia
I use high resolution hydro-dynamical simulations of the formation and evolution of the disc component in spiral and lenticulars galaxies to establish and understand the link between angular momentum and radial stellar migration. I show that the latter determines the formation of the break in the stellar radial projected density profile as well as the inner and outer disc scale lengths. I will also discuss the redistribution of the angular momentum within the disc galaxy, and in particular the transfer of angular momentum from the inner parts of the disc (the bar/bulge region) to the halo, due to the bar growth and evolution. Thus I will show how the angular momentum redistribution is linked to the place of the galaxy in the SA / SB branches of disc galaxies in the Hubble diagram.
Time evolution of the metallicity gradients
Athanassoula, Lia
I will present results from over two dozens high resolution chemodynamical simulations of disc galaxies, including both isolated and merger-related cases. In particular, I will present the radial metallicity gradients for stellar populations at different distances from the equatorial plane and their evolution with time. I will also discuss recent results on the distribution of stars in the [Mg/Fe] versus [Fe/H] plane in my simulations and how this evolves with lookback time. In the same way as for the radial metallicity gradients, I will consider either all disc stars, or only populations from specific radial and vertical bins, as well as age bins. Preliminary comparisons with observations show a good agreement, particular concerning the multi-component signatures. My results allow me to discuss the effect of radial migration on these distributions and radial gradients.
Morphology and kinematics of the cold gas inside the central kiloparsec of nearby AGN with ALMA
Audibert, Anelise
One of the problem to fuel black holes and trigger the AGN is to remove a large amount of angular momentum to drive the gas to the center. The dynamical mechanisms invoked depend on the scale under consideration: at 10kpc scales, torques are produced by galaxy interactions and mergers; at kpc scales, bar instabilities, either internally driven by secular evolution, or triggered by a companion can first feed a central starburst and fuel the massive BH. At 100pc scales, the nested bars scenario, together with m=1 instabilities, are believed to dominate as dynamical mechanisms.Our goal is to probe the cold molecular gas in galaxy disks in a sample of nearby AGN (Seyfert/LINER), spanning more than a factor of 100 in AGN power (X-ray and radio luminosities), a factor of 10 in star formation rate (SFR), and a wide range of galaxy inner morphology. We aim at (i) identifying what are the mechanisms driving gas from the disk towards the nucleus, removing its large angular momentum and forming large non-axisymmetric perturbations and (ii) considering a large number of cases, deriving in which phase of their fuelling/feedback cycle they are observed, and deduce the different steps of the process.We will show the study of the morphology and kinematics of the cold dense gas inside the central kpc of 5 galaxies of our NUGA (NUclei of GAlaxies) program. We present ALMA observations of CO(3-2) and dense molecular gas tracers HCN(4-3), HCO+(4-3) and CS(7-6) for 5 galaxies with 0.14-0.3” resolution, centred on the nucleus and covering the whole nuclear disks and rings. We quantify the AGN fuelling by measuring torques on the gas computed from the stellar potential with the well-tested algorithm reported in Garc ´ia-Burillo et al. (2005); Combes et al. (2014).
CGM emission predictions from cosmological zoom-in simulations
Augustin, Ramona
Gas flows in and out of galaxies are poorly constrained and understanding these processes is crucial to studies of galaxy evolution.Observations of the Circum-Galactic Medium (CGM), where these processes take place, are therefore essential for making progress in understanding gas flows but remain challenging as this medium is intrinsically thin and very faint.To improve observing strategies, we have made CGM emission predictions from dedicated cosmological zoom-in simulations.We use hydrodynamical AMR RAMSES simulations down to z=0 with a maximum spatial resolution of 380 pc/h in the central region.Using CLOUDY emissivity models for different lines (e.g. Ly-alpha, CIV, OVI, OVIII), we post-process galaxy halos from the simulation with these models and compute the expected emission from the gas in the CGM.These post-processed simulated halos then give the flux for different lines at different redshifts and can be used as estimates for the observations in different wavelength regimes (X-Ray, UV, optical, IR).
Observing the CGM with ELT/HARMONI
Augustin, Ramona
Gas flows in and out of galaxies are poorly constrained and understanding these processes is crucial to studies of galaxy evolution.Observations of the Circum-Galactic Medium (CGM), where these processes take place, are therefore essential for making progress in understanding gas flows but remain challenging as this medium is intrinsically thin and very faint.The next milestone in this research area will be the access to the ELT with its large collective area, increasing the sensitivity to faint extended emission. Its first light IFU HARMONI will give both spatial and spectral information on the CGM.We use dedicated zoom-in cosmological RAMSES simulations and post-process galaxy halos with emission predictions from photoionisation modelling to estimate the typical fluxes from the CGM. Those are used as input into the HARMONI Simulator (HSIM) to predict the expected signal from the CGM with HARMONI observations and to optimise observing strategies.We also compare the outcome with the signal that we would get from existing IFUs, such as MUSE and SINFONI on the VLT, to estimate the improvement over those for CGM studies.
Study of Sanskrit inscriptions of South East Asia as sources of records of celestial events.
B S, Shylaja
Inscriptions in Sanskrit are seen in Cambodia,Nepal, Srilanka, in general all over South East Asia from about 4th Century CE till about 13th century. These are records of grants and other religious deeds with valuable documentation of celestial events like eclipses, planetary conjunctions and even comets. A study of these records also throws light on the evolution of the calendar and influence of other types of calendars. Possible mention of the 1054 supernova event also is discussed.
Review of the evolution of large single dishes
Baars, Jacob
In 1937 Reber completed his home-built parabolic reflector antenna of 10 m diameter. He systematically scanned the sky at a wavelength of 1.9 m and produced the first research paper in radio astronomy in 1940. After WW-2 radio astronomy became an active research field in several countries and the paraboloidal reflector became the telescope of choice at wavelengths shorter than about one meter. Radar antennas of up to 7.5 m diameter were widely used in the early years. In the early fifties proposals for large parabolic dishes with a size between 15 and 75 m were advanced. The design of these movable structures that had to point accurately in a desired direction and maintain its shape with varying attitude angle, posed new challenges to the structural engineers, who were recruited mainly from the domains of bridge building and aircraft manufacture._x000D_ I shall illustrate how physicists and engineers created the design tools (e.g. finite element analysis), fabrication methods (composite structures), material choices (carbon fiber reinforced plastic), control systems and algorithms to realize the radio telescopes of ever expanding size and precision to penetrate deeper into the cosmos at high angular resolution and at all accessible wavelengths. This process will be illuminated by the examples of those instruments where progress in the state of the art is most clearly visible without going into details of the telescope’s realization._x000D_ The progress over the last 60-70 years has been impressive: from 10 –20 m diameter reflectors that barely functioned at 20 cm wavelength, via 40-75 m telescopes operating at short cm-wavelengths to 100 m antennas that can be used a 3 mm wavelength. At the extremes there is FAST, a 500 m diameter fixed spherical bowl in China for cm/dm wavelengths, and the ALMA array in Chile with more than 6o dishes of 12 m diameter that reach the shortest wavelength of 0.2-0.3 mm where the atmosphere is partially transparent.
Calibration Strategies for the Hubble Space Telescope Wide-field Channel 3 IR detector
Baggett, Sylvia
TBA
Towards Realistic Understandings of Gas Dynamics in Protoplanetary Disks
Bai, Xuening
The gas dynamics and long-term evolution of protoplanetary disks (PPDs) play a crucial role in almost all stages of planet formation, yet they are far from being well understood largely due to the complex interplay among various microphysical processes. Primarily, PPD gas dynamics is likely governed by magnetic field, and its coupling with the weakly ionized gas is described by non-ideal magnetohydrodynamic (MHD) effects. Incorporating these effects, I will present the first fully global simulations of PPDs aiming to incorporate most realistic disk microphysics. Accretion and disk evolution is primarily driven by magnetized disk winds with significant mass loss comparable to accretion rate. The overall disk gas dynamics strongly depends on the polarity of large-scale poloidal magnetic field threading the disk owing to the Hall effect. The flow structure in the disk is highly unconventional with major implications on planet formation.
Long-Term Model-Based Reconstructions of the Solar Irradiance
Ball, Will
To understand how our climate has changed in the past, and will evolve in the future, it is important to estimate changes in Earth's primary energy source: the Sun. Solar irradiance is a fundamental component of any climate modelling study. Variations in both the total, and spectral, solar irradiance are essential to determine the magnitude of the impact that the Sun has made, and will make, to the climate. Here, I will provide an up-to-date review of the main long-term total and spectral irradiance reconstructions relevant to forcing climate models, which can show a large range of both total and spectral variations on decadal and centennial timescales. To put in context the century-scale reconstructions, for which direct irradiance observations do not exist, it is important to also discuss the irradiance models with respect to the observations that have accumulated over the last 40 years, since the beginning of the satellite era. Therefore, I will also give an overview of the uncertainties that remain in the observations used to constrain and verify models, and the forcing range that the long-term reconstructions will provide to reconstruct past climate behaviour, and make future projections.
Serving Astronomy: the Aim of the IAU
Baneke, David
The IAU was founded in 1919 “to facilitate the relations between astronomers of different countries where international co-operation is necessary or useful” and “to promote the study of astronomy in all its departments.” These aims have led the IAU throughout the century of its existence, but the way it has tried to fulfill them has changed. Johannes Andersen, Claus Madsen and I have tried to trace the changing role of the IAU in the international astronomical community through the twentieth century and into the twenty-first. The IAU has striven – occasionally struggled – to protect international scientific cooperation across the deep political divides that characterized the 20th century, while maintaining an important function in the context of the rapidly evolving science itself and the changing fabric of institutions involved in astronomy. We especially argue how the emphasis of the IAU’s activities has shifted from the first aim – facilitating collaboration by organizing meetings and defining common standards – to the second aim: promoting astronomy by outreach and development programs.
pre-main sequence stars
Baraffe, Isabelle
TBA
Large-Scale Diffuse Intergalactic Magnetic Fields Constraints With the Cherenkov Telescope Array
Barai, Paramita
Magnetic fields of the order of µ-Gauss are observationally detected in galaxies and clusters, which are believed to be created by the amplification of much weaker primordial seed fields. These fields should be carried out by strong galactic outflows, magnetically enriching the InterGalactic Medium (IGM) at larger cosmological distances. However direct observation of magnetic fields in the IGM is scarce. In this talk, I will give a review of how Intergalactic Magnetic Field (IGMF)'s strength and filling factor can be constrained using numerical simulations and gamma-ray observations.We are performing cosmological hydrodynamical simulations containing dark-matter and all relevant physical processes for the baryons. We analyze the simulations following the methodology of Barai (2008, ApJ, 682, L17), and compute the magnetic field in the simulation volume IGM. Our objectives are: to explore the evolution of IGMFs through cosmic times, and to compute the contributions of galactic outflows (driven by SN versus AGN) in the advection of magnetic fields from the galaxies to the IGM.On the observational side, high-energy TeV photons emitted by distant blazars can interact with the cosmic extragalactic infrared/optical background light, producing electron-positron pairs, and initiating electromagnetic cascades in the IGM. The charged component of these cascades is deflected and delayed by IGMFs, thereby reducing the observed point-like TeV flux, and creating an extended image in the GeV energy range, which can potentially be detected with gamma-ray telescopes (Fermi-LAT, HESS, CTA). Studies [e.g., Neronov & Vovk (2010, Science, 328, 73); Dolag et al. (2011, ApJ, 727, L4)] have put lower limits on the IGMF strength of the order of 10-16 - 10-15 G, and filling factors of 60%. I will overview such work; and describe the constraints on the IGMF which the Cherenkov Telescope Array sensitivity is expected to give(Acharya et al. 2017, CTA consortium science paper).
Revised estimates of the frequency of Earth-like planets in the Kepler field
Barbato, Domenico
The search for Earth-like planets around Sun-like stars and the evaluation of their occurrence rate is a major topic of research for the exoplanetary community. Two key characteristics in defining a planet as 'Earth-like' are having a radius between 1 and 1.75 times the Earth's radius and orbiting inside the host star's habitable zone; the measurement of the planet's radius and related error is however possible only via transit observations and is highly dependent on the precision of the host star's radius. A major improvement in the determination of stellar radius is represented by the Gaia astrometry satellite, which promises to provide unprecedented precision on stellar parameters.We present a new estimate of the frequency of Earth-sized planets orbiting inside the host stars's habitable zones, obtained using Gaia measurements of parallax for solar-type stars hosting validated planets in the Kepler field as input for reassessing the values of planetary radius and incident stellar flux. This updated occurrence rate can be an important element in coordinating future observational efforts searching for Earth-like system in the Sun backyard using next-generation astrometric missions.
Understanding the Where and the How Big of Solar Flares
Barnes, Graham
The approach to understanding solar flares generally characterizes global properties of a solar active region, for example the total magnetic flux, the total free magnetic energy, or the total length of a sheared magnetic neutral line. We take here a different tack, characterizing not the region as a whole, but estimating the energy-release prospects of different sub-regions within the region. We have considered two active regions (NOAA ARs 10978 and 11283) which are similar in their overall size and classification, but produced radically different distributions of flares, with AR 10978 producing nothing larger than C-flares while AR 11283 produced a sequence of M and X-flares, with very few smaller flares. We modeled the coronal magnetic field using the CFIT non-linear force-free extrapolation code, and identified individual current systems within the the extrapolation whose energy might be released in a single reconnection event. We present here early results comparing the energy associated with the individual current systems with the magnitude of the flares originating from each region.This material is based upon work supported by the US National Science Foundation under Grant No. 1630454. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
Exploring the taxomony of metallicity gradients in SDSS-IV MaNGA interacting galaxies
Barrera-Ballesteros, Jorge K.
Observational evidence suggests that for a non-interacting star-forming galaxy, the radial distribution of the gas metallicity follows a negative gradient supporting the inside-out galactic evolution scenario. On the other hand, due to tidal-induced radial movements towards galactocentric regions, interactions and mergers have been advocate to flatten the observed negative gradient in isolated galaxies. The lack of a large sample with spatially resolved maps of metallicity has hampered the study of the statistical impact of mergers in metallicity gradients. In this study we present the gas-phase metallicity radial distribution derived in more than 500 interacting galaxies included in the Integral-Field Unit (IFU) SDSS-IV MaNGA survey. Thanks to the large IFU MaNGA sample, we are able to compare these gradients with more than 3000 non-interacting control galaxies. We explore the variety of shapes observed in the metallicity gradients for interacting galaxies as well as quantify the impact of global parameters.
The United Nations Open Universe Initiative for Data in Space Science
Barres de Almeida, Ulisses
”Open Universe” is an initiative under the auspices of the Committee on the Peaceful Uses of Outer Space (COPUOS) that aims at stimulating a dramatic increase in the availability and usability of space science data, extending the potential of scientific discovery to new participants in all parts of the world, especially for developing and underdeveloped Countries. The initiative is carried out in cooperation with the United Nations Office of Outer Space affairs (UN- OOSA) as part of the activities in preparation for UNISPACE+50 and the United Nations Space2030 agenda. Open Universe seeks to trigger a major evolution of current space science data availability fostering the publication of all existing open space science data in a way that is easily discoverable and immediately usable, thus responding to the global demand for transparency. A number of technical activities are currently in development towards the launch of the initiative, which include a prototype, multi-discipline (astrophysics, planetary sciences, cosmic- ray and atmospheric physics) and multi-messenger Open Universe Portal at the Italian Space Agency (ASI). The purpose of the Open Universe actions is to integrate and render as interoperable as possible a large number of space science data sets, analysis tools, and general information services, provided by many online space science data archives, based on VO-technology. The Open Universe is designed to answer the needs of professional scientists and common citizens alike, offering services and data products,which can be used to learn about space science or perform scientific analyses. This presentation will briefly illustrate the principles behind the Open Universe initiative and provide a description of the main features currently under development, specially for science in the multi-messenger era.
CI Camelopardalis: The first sgB[e]-High Mass X-ray Binary Revisited Twenty Years on
Bartlett, Elizabeth
Supergiant B[e] (sgB[e]) stars are a rare type of evolved, very massive star with complex hybrid spectra. The standard explanation for these spectra is a two component stellar wind which includes a dense, slowly expanding disc and/or torus, many times larger than that of a classical Be star. Binary interactions are thought to be the formative agent for this torus, but identifying bona fide sgB[e] binaries has proved extremely difficult due to the extreme stellar winds and high levels of local extinction (attributed to the torus). The Galactic supergiant B[e] star CI Camelopardalis (CI Cam) was the first sgB[e] star detected during an X-ray outburst. The star brightened by 5 orders of magnitude within hours before decaying to quiescence in less than 2 weeks. Such X-ray activity firmly establishes this source as a High-Mass X-ray Binary but the nature of the compact object, as well as binary system parameters, are still a topic of debate 20 years on. Since the outburst of CI Cam, a number of sgB[e] stars have been identified as X-ray overluminous for a single star (i.e., LX > 10-7Lbol). This small population is highly hetergeneous and has recently expanded to include two Ultra Luminous X-ray sources (ULX), Holmberg II X-1 and NGC300 ULX-1/supernova imposter SN2010da. In this talk I will report on our recent discovery of dramatic variability in the quiescent X-ray spectrum of CI Cam in the context of binarity, and discuss the X-ray bright sgB[e] stars as a population and their importance for other fields of astronomy.
Some issues in stellar modelling
Basu, Sarbani
Stellar models are only as good as the inputs used to construct them. These may be microphysics inputs, such as radiative opacities and equation of state, or macrophysics effects such as diffusion and gravitational settling, convective overshoot, and rotation-induced mixing. I shall review how uncertainties in some key inputs to stellar models affect our interpretation of stellar data, and what needs to be done to make stellar models more robust.
Statistical properties of Faraday rotation measure from large-scale magnetic fields in intervening disc galaxies.
Basu, Aritra
Cosmic evolution of the large-scale magnetic field in star-forming galaxiesremains an open question in observational astronomy. A major tool to probemagnetic fields in distant galaxies would be through statistical measurement ofFaraday rotation measure (RM) towards quasar absorption line systems, which aretracers of galaxies in the high redshift Universe. The distribution of RM oftwo quasar samples, with and without absorption line systems, are compared tostatistically infer the properties of magnetic fields in the intervening galaxypopulation. To extract as much information on the properties of coherentmagnetic fields, we present analytical and empirical form of the probabilitydistribution function of RM when random lines of sight are shot through asample of galaxies with random inclination, impact parameter and azimuthalangle, and assuming that the magnetic field is confined to the disc withaxisymmetric spiral geometry. Interestingly, the dispersion in RM produced bythe large-scale fields in the intervening galaxies is comparable in magnitudeto that observed in previous studies. We find that the width of RMdistribution is directly related to the mean coherent field strength of theintervening galaxy population provided the dispersion within the sample is low.Finally, we discuss sample selection criteria that are crucial for cleaninterpretation of the observations. Selecting high metallicity DLAs as theintervener is the best choice to study magnetic field amplification driven bygalactic dynamo action.
Before OAD
Batten, Alan H
OAD, the Office of Astronomy for Development, one of the most significant innovations within the IAU, was instituted at the XXVII General Assembly in Rio de Janeiro in 2009 and opened in South Africa in 2011. The new Office brought together and strengthened several activities of the IAU aimed at helping astronomers in developing or isolated countries to keep in touch with their colleagues elsewhere and up-to-date with the developments in our science. Those activities were mediated through the old commission structure by Commission 38 (Exchange of Astronomers) and Commission 46 (Teaching of Astronomy) which oversaw the International Schools of Young Astronomers (ISYA), the Visiting Lecturer Programme (VLP) and Teaching for Astronomy Development (TAD). In addition, Jorge Sahade, during his term as IAU President (1985-1988), formed the Working Group for the Promotion and Development of Astronomy as a sub-committee of the Executive Committee, and asked the present writer, then a Vice-President, to act as chair. That Working Group (later renamed the Working Group for the Worldwide Development of Astronomy, WGWWDA) operated within the context of the already existing services of the IAU and in cooperation with the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS). In this paper, the writer gives an account of the activities of the WGWWDA both during and between General Assemblies, until the year 2000, shortly after which he relinquished responsibility for them.
The Origins Space Telescope and Solar System Science
Bauer, James
The Origins Space Telescope (OST) is the mission concept for the Far Infrared Surveyor, a study in development by NASA in preparation for the 2020’s Astronomy and Astrophysics Decadal Survey. With approximately three orders of magnitude gain in sensitivity over previous far-infrared missions, the telescope also provides high angular resolution to overcome spatial confusion in deep surveys, and new spectroscopic capabilities to detect water and other volatiles in planet forming disks as well as solar system objects. OST’s spectroscopic capabilities will facilitate an unprecedentedly large statistical study of volatile isotopes. With more than 100 comets from multiple reservoirs of diverse origin, including the Oort Cloud, Halley Type, and Jupiter Family comets, the mission will provide a better understanding of the delivery of volatiles to terrestrial planets, and their evolution across varying environments and histories of insolation. By expanding the measurements of D/H in comets to statistically meaningful numbers, OST will be able to map this ratio in much fainter and less active comets than current facilities can reach, and provide insight into the possible origins of Earth’s oceans.OST will also characterize the most distant bodies in the solar system. OST will discover thousands of new TNOs while and measuring their sizes down to ~10km, thus providing size distributions that will test theories of their formation and origin. The high spatial resolution will detect activity in the most distant of comets, as well, and allow thermal imaging of extended structures of dark material or low-albedo binary companions that may accompany these distant bodies. We will introduce the vast array of solar system science that this survey mission offers.
Brown dwarfs in the context of ELTs
Bayo, Amelia
Even though substellar objects were first imaged already more than twenty years ago (and theoretically predicted more than 50 years ago), many fundamental questions regarding these objects remain open: their dominant mechanism of formation, their complex atmospheres, etc. In this talk I will summarize the state-of-the-art of some of these open challenges and how the ELTs with their first and second generation instrumentation and the synergies with other developping facilities will pave the way to answers.
Commission B4 – Present and Future
Beasley, T.
TBA
Cosmic Distance Scale
Beaton, R.
TBA
The gNUVA interface for collaborative project on small UV projects
Beitia, Leire
Cubesat technology is maturing rapidly, becoming versatile and opening the possibility to fly, for modest costs, surveying experiments that will have a tremendous impact in astronomy. This technology has many advantages that includes the quick manufacturing times that adapt well to the rapid evolution of technology and data science. Their low cost will make space research accessible to small groups and Universities favouring the rapid development of science and technology. However, this brilliant future is hampered by the launching facilities. Creating fast-track launching programs for cubesats is a must for this revolution to take place. The IAU WG on UV astronomy has developed an interface to assist teams interested in developing small 1-15 U cubesat type project to advertise, look for partners and start collaborations. The tool will be described during the session.
The Astrophysics of BH-BH/NS-NS Mergers with LIGO/Virgo
Belczynski, Krzysztof
I will discuss the astrophysical importance of the recent LIGO/Virgo direct detections of gravitational-waves. Despite majority of the expectations, it was not neutron star mergers being detected first, but the series of exotic massive black hole mergers. I will describe the leading theories of the formation of such black hole systems. I will also comment on a detection of NS-NS merger. This particular detection may provide striking constraints on binary evolution. Several astrophysical implications are beginning to emerge despite the fact that the exact origin of LIGO/Virgo sources is not yet known.
Metallicity gradients in the nearby Universe: shedding new light on the role of gas flows in galaxies with MaNGA
Belfiore, Francesco
Theoretical models demonstrate that galaxy evolution is largely shaped by the interplay between inflows, star formation and feedback processes. Since chemical abundances are sensitive to the integrated effect of gas flows and star formation, they constitute the ideal tool to improve our understanding of these phenomena._x000D_ I will present a new study of metallicity gradients in the low-redshift Universe from SDSS-IV MaNGA, the largest integral field spectroscopy survey of nearby galaxies to date. The observed dependence of the metallicity gradient on stellar mass will be discussed in the context of an updated 'bath-tub' model, which we have developed to extend the previous model formalism to resolved scales in galaxies. In particular, I will focus on the importance of including inside-out growth in the models, and on the relation between metallicity profiles and other observables (e.g. SFR, stellar mass)._x000D_ Intriguingly, our results confirm the presence of a statistically significant flattening of the metallicity gradient at large radii. I will conclude discussing the possible implications of this result for our understanding of gas flows and recycling in galaxies.
Land- and skyscape within Astronomy and World Heritage initiative: Spanish study cases
Belmonte, Juan Antonio
During the International Year of Astronomy IYA 2009, UNESCO and IAU promoted the Astronomy and World Heritage Initiative to study and analyze the relationship between land- and skyscapes and human interest in the celestial vault that could drive to the promotion of certain tangible and intangible astronomical heritage as human World Heritage. Since then, numerous actions have been carried out that finally drove to the creation of IAU Comission C.C4 "World Heritage and Astronomy" within Divission C "Outreach, Education and Heritage" at the IAU GA in Honolulu in August 2015. In this contribution, a brief analysis of a few study cases centred in the author's experience in Spain will be presented: an already successful paradigm in Antequera, a state of the art initiative of a cultural land- and skyscape in the evaluation process at Gran Canaria, a new address to a controversial proposal in Menorca and future ongoing plans for future cross-national collaborative effforts within the same framework in the Iberian southwest. Future perspectives will also be briefly discussed.
Extremely dark asteroids linked to asteroid families
Belskaya, Irina
Several asteroid families which contain low albedo asteroids were identified in the inner part of the main asteroid belt [e.g. Delbo et al. Science 357, 1026, 2017]. Such families are considered to be primordial ones which constrain planetesimals population. Typically all asteroids with geometric albedo <0.12 are considered as belonging to the low albedo C-complex. The diversity inside the C-complex was not taken into account. However, for the long time it was known a relative abundance of the low albedo F-type asteroids in the inner asteroid belt. A large fraction of the F-asteroids were associated with the Nysa-Polana family [Cellino et al. Icarus 152, 225, 2001]. Recent classifications are not able to distinguish the F-type asteroids from B or C-types. The spectroscopic study of low-albedo asteroids from the Polana-Eulalia family complex was not able to reveal spectral diversity of these objects [De León et al. Icarus 266, 57, 2016; Pinilla-Alonso et al. Icarus 274, 231, 2016]. We will show that polarimetric and photometric measurements give a way to separate low-albedo types. The F-type asteroids revealed particular polarimetric and photometric properties different from those of the B and C-type asteroids. The only plausible explanation of the observed particularity of the F-type asteroids is an assumption of their extremely dark surfaces. Among 24 known F-type asteroids, 13 asteroids have similar proper elements within the Polana-Eulalia complex but they are not considered as family members. Moreover, four F-asteroids were classified as belonging to the Hertha family. We need to take into account a diversity of low-albedo asteroid classes to confirm reliability of low albedo family membership.
Gravitational Microlensing Results Challenge the Core Accretion Theory
Bennett, David
The gravitational microlensing planet detection method is currently the only method sensitive to low-mass exoplanets orbiting beyond the snow line, where the core accretion theory predicts that planet formation should be most efficient. I present a comparison between the mass ratio distribution of exoplanets from microlensing found by Suzuki et al. (2016) to theoretical population synthesis calculations by two different groups. The Suzuki et al. (2016) mass ratio distribution conforms to core accretion expectations that Neptune mass planets are much more common than Jupiters. However, both population synthesis simulations of core accretion predict a deficit of planets at intermediate masses (between Neptune and Saturn) that is not seen in the microlensing data. This mass gap in the core accretion prediction is due to the runaway gas accretion that is thought to occur once giant planet cores reach a critical mass threshold. The microlensing observations suggest that this gap may not exist. Perhaps, the formation of gas giant planets is more complicated than previously thought, or it might be that the variations in the planet formation process in different systems are so large that the gap is washed out in a statistial sample, like that of Suzuki et al. (2016). Finally, I discuss how the microlensing test of the core accretion theory will be improved with a mass measurements of microlens planets and their host stars, as well as a larger sample of planetary microlensing events.
Exoplanet Astrometry Methods for WFIRST
Bennett, David
The Wide Field Infrared Survey Telescope (WFIRST) is NASA’s first flagship survey telescope. One of its major surveys will be the WFIRST exoplanet microlensing survey that will find planets down to the mass of Mars in orbits wider than 0.5 AU. When combined with the results from Kepler, WFIRST will provide a statistical of planets down to low masses at all orbital separations. The microlensing light curves provided by WFIRST will yield direct measurements of the planet-star mass ratio, but WFIRST’s high angular resolution will allow astrometric measurements of the unresolved host and source stars that can determine the masses of the host star and planet. I present new results that demonstrate this method with high angular resolution follow-up observations from the Hubble Space Telescope and adaptive optics observations with the Keck-2 telescope. I also discuss astrometric microlensing observations that can be made with WFIRST that can measure the masses of planets orbiting stellar remnants. Finally, I discuss a novel method for WFIRST’s wide field camera to obtain astrometry of nearby stars that may allow the detection of habitable zone terrestrial planets orbiting a handful of nearby stars.
Electron Acceleration in Nanoflares and Preflares - Relevant for Coronal Heating?
Benz, Arnold O.
A significant fraction of the energy of solar flares is first released into energetic electrons. The acceleration process is still controversial. We discuss here the gyrosychrotron emission of relativistic electrons and compare it to the soft X-ray emission of the flare plasma by thermal bremsstrahlung. The ratio of radio to soft X-ray luminosities is a measure of the acceleration efficiency. In regular flares and coronae of active stars, the ratio is constant over many orders of magnitude in flare size. However, the quiet Sun does not follow the ratio observed for flares. Here we present new observations by the Nobeyama Radioheliograph and the RHESSI X-ray satellite. In small preflares we find their radio-to-X-ray ratio at least an order of magnitude smaller than in the main flare phase. The trend of small flares to be less efficient electron accelerators was also noticed in previous observations, indicating that they have a softer hard X-ray spectrum and thus are lacking in electrons accelerated to high energy. It is also a general trend that flares start with a steep hard X-ray spectrum (few high-energy electrons) and harden during the event. Most significantly, microflares in the quiet region, also known as (large) nanoflares, are clearly radio-poor often by more than an order of magnitude, thus are poor accelerators. One of the currently viable scenarios for coronal heating is energy release by nanoflares that are smaller than previously observed. Thus the question arises whether they also accelerate electrons. The emissions of such electrons in gyrosynchrotron radiation or hard X-rays have not yet been observed, but would be a crucial test of the theory. In the case of radio emission, the thermal background makes it impossible. We report on the estimated flux of the hard X-ray emission of accelerated electrons and discuss the possibility for detecting it with upcoming missions, in particular with STIX on Solar Orbiter.
Biohaze as an atmospheric biosignature of an early Earth
Berdyugina, Svetlana
On the current Earth, the surface biosphere emits a substantial amount of bioaerosols to the atmosphere, where they comprise up to 25% of total airborne particle mass. SImilarly, on the Earth with early life, bioaerols could be continuousy emitted into the atmosphere and create biohazes and cloud droplets containing biopigments and other partially decomposed biomass. Here, we employ our spectro-polarimetric laboratory measurements of various photosynthetic bacteria for modeling planetary atmospheres polluted by bioaerosols, such as living and partially degraded bacteria and biopigments. Using our model for stellar light scattered by a planetary atmosphere, we compute polarized light-curves and spectra from planets with biohazes and cloud droplets containing bacteria and photosynthetic pigments. We estimate the minimum concentration of biomass in the atmosphere necessary for remote detection on distant exoplanets similar to the early and present Earth.
Characterization of Earth-like planets with the Exoplanet Surface Imaging (EPSI) technique
Berdyugina, Svetlana
We demonstrate an inversion technique to image indirectly exoplanet surfaces using observed unresolved reflected light variations over the course of the exoplanets orbital and axial rotation: ExoPlanet Surface Imaging (EPSI). Under various geometric conditions the reflected light curve contains enough information to detect both longitudinal and latitudinal structures and to map exoplanet surface features. We demonstrate this using examples of Solar system planets and moons as well as simulated planets with Earth-like life. Such albedo maps obtained in different wavelength passbands can provide "photographic" views of distant exoplanets and may lead to unambiguous detection of life.
Intracluster magnetic field: primordial field or dynamo?
Beresnyak, Andrey
The intracluster medium have magnetic fields with strength of a few µG and the correlation scale of a few tens of kpc, the largest scales of the magnetic field so far observed in the Universe. Can this magnetic field be used as a test for the primordial magnetic field? I would argue that if the initial cluster field was modified by the nonlinear dynamo, the process would be insensitive to the value of the initial field. My model relies on statistics of turbulence from simulations of cluster formation in a fully cosmological context as well as nonlinear dynamo theory. Although the initial field is not a parameter of this model, it predicts length scale and magnitude of the magnetic field which are compatible with observations.
CHemical Abundances Of Spirals: Understanding Gas Content and ISM Conditions through CHAOS
Berg, Danielle
Accurate and robust measurements of extragalactic metallicities are essential to constrain models of chemical enrichment, chemical evolution, and the cycle of baryons in the cosmos. Despite this strong dependence on chemical abundances, an absolute calibration of gas-phase abundances from nebular emission lines has not been definitively established. The CHemical Abundances of Spirals (CHAOS) project leverages the combined power of the Large Binocular Telescope (LBT) with the broad spectral range and sensitivity of the Multi-Object Double Spectrographs (MODS) to uniformly measure ``direct" abundances in large samples of HII regions in spiral galaxies. Thus far, CHAOS has increased, by more than an order-of-magnitude, the number of H II regions with high-quality spectrophotometry to facilitate the first detailed measurements of the chemical abundances of a statistically significant sample of nearby disk galaxies. These observations, which include a large number of low excitation H II regions, have led to several unexpected results, challenging our current understanding of the trends in gas conditions, ionization correction factors, relative abundances, and more. Fortunately, the unprecendented number of sensitive diagnostics in the rich CHAOS dataset allows for new approaches to investigate these issues. In addition to helping us understand nearby galaxies, calibrating the nebular abundances of massive galaxies has important implications for deciphering the ISM in more distant galaxies and properly calibrating the spatially resolved abundances from IFU surveys.
Chemistry of Protoplanetary Disks
Bergin, Edwin
With the continuing successful operations of the Atacama Large Millimetar Array (ALMA) we are able to characterize the initial stages of planet formation in great detail. With ALMA we have begun the search for understanding the development of chemiscal complexity into the age of planet formation and I will present a sample these results. By far the largest effect that has been inferred to be present is the large discrepencies between gas masses measured by CO and those measured by dust. This implies either that there is singnificant decline in the CO gas phase abundance, even in layers above the sublimation temperature, or that the gaseous disk dissipation is rapid and gas giant formation must occur on short ~Myr timescales. We will discuss the evidence that this major effect is likely due to changes in the CO abundance through a combination of gas-dust interactions and chemical processing in the gas. This has implications on abundances of major carriers of elemental C and O which may leave an imprint in the resulting chemical composition of forming gas giants. Thus, we will also discuss the link between disk chemistry and planet formation.
StarDICE: An artificial star for absolute broadband flux calibration
Betoule, Marc
StarDICE is an absolute flux calibration experiment hosted by the Observatoire de Haute Provence (OHP), whose purpose is to confront the broaband calibration of the CALPSEC spectral library to the instrumental flux scale established by the NIST. It consists in the use of a stable, convenient and NIST-calibrated polychromatic light-source called DICE to measure the broadband response to point-like illumination of a short focal length robotic telescope. The dedicated telescope is then used to follow the evolution of the broadband fluxes of spectrophotometric standard stars as a function of airmass over a very large number of nights. The experiment is currently in the last stage of its test phase whose goal is to evaluate the accuracy of the calibration transfer accross the atmosphere.In this contribution, we will review the experiment, present early results from the test phase and discuss prospects for the next phase.
Newly discovered Planetary Nebulae population in Andromeda (M31): PN Luminosity function and implications for the late stages of stellar evolution
Bhattacharya, Souradeep
Stars with masses between ~0.7 and 8 M? end their lives as Planetary Nebulae (PNe) following the AGB phase. Because of their relatively strong [OIII] 5007Å emission, PNe can be readily identified in continuum-subtracted narrowband images, and their spectroscopic follow up provides information on the kinematics and oxygen abundance in regions where the surface brightness of the parent stellar population is too faint for absorption line spectroscopy. With the MegaCam@CFHT, we have carried out a survey of the inner central 24 sq. degrees of Andromeda (M31) reaching the outer disk and halo, using a narrow-band filter centered on the [OIII] 5007Å emission line and a broad-band g filter. This survey extends the previous PN sample by Merrett et al. 2006 (MNRAS, 369, 120) both in uniform area coverage and depth. It promises to answer the open questions on the kinematics of the stellar halo in Andromeda galaxy and the shape of the PN luminosity function (PNLF) at the faint end. From the continuum-subtracted narrowband images, we identify ~4000 PNe in M31, of which ~3000 are newly discovered. We obtain PNe down to ~6 mag below the bright cut-off of the PNLF, ~2 mag deeper than in previous works. We find that the bright cut-off of the PNLF is consistent with previous determinations, however, we are now able to detect a steep rise in the number of PNe ~5 mag fainter than the bright cut-off. This steep increase persists in the PNLFs obtained at different projected elliptical radii in M31, and is reminiscent of the morphology of the PNLF measured for the Large Magellanic Cloud (Reid & Parker 2010, MNRAS, 405, 1349). The next steps include the association of the PN population with the RGB stars from the Pan-Andromeda Archeological Survey (PAndAS) and discussion of possible causes of the steep rise at the faint end of the PNLF in the framework of the post-AGB stellar evolution models.
Dust gradients and solid-phase metallicity
Bianchi, Simone
The recent Herschel mission has allowed to study the distribution of cold dust in nearby galaxies with unprecedented resolution. Radial gradients in the dust mass have been found to be flatter than the stellar, and intermediate between those of the molecular and gas components. In principle, dust and gas resolved observations can be used together to derive the metallicity gradient in the solid phase. There are however several potential pitfalls: dust properties might vary with the environment, and thus bias the mass estimates over that predicted using grain models for the diffuse MW ISM; the shape of the SED - and again the mass estimate - might depend on an uncertain local inter-stellar radiation field; also, the solid-phase metallicity depends on uncertain, metallicity and environment dependent, conversion factors to obtain the total molecular gas from observations of CO. Nevertheless, a number of attempts have been made to derive the dust properties, dust-to-gas ratio and CO-to-H2 conversion factors from far-infrared observations. I will report on these studies, focusing on the results from DustPedia, a database of almost all resolved galaxies in the local Universe observed by Herschel.
Extreme jet distortions in low-redshift radio galaxies
Birkinshaw, Mark
Jets commonly display bends and knots at which the flows may change character. Some extreme distortions have implications for the nature of jet flows and their interactions. We will present the results of recent radio mapping of 3CRR and other radio galaxies. In the case of NGC 7385 the cause of the distortion is a collision with a foreground magnetised gas cloud which causes Faraday rotation and free-free absorption, and is triggered into star formation: the highly-ionized cloud in PKS 2152-699 may be similar. For NGC 6109 the distortion is more extreme, but no deflector can be identified in cold or hot gas: a similar distortion in NGC 7016 is apparently associated with an X-ray gas cavity. The results will be related to encounters with substructures in the intergalactic medium and the compositions and speeds of the jets.
Neutral atmospheric escape in the Solar and extrasolar planetary systems
Bisikalo, Dmitry
New data obtained by space missions to various objects in the Solar system and observations of the outer Solar system and exoplanets by space and ground-based telescopes allowed us to conclude that the atmospheric escape plays an important role in the evolution of the terrestrial planets in the Solar system (Marov et al., 1996). Observations and theoretical models of the exoplanet atmospheres exposed to the extreme fluxes of X-ray and UV radiation of the parent star provide a remarkable opportunity to test theoretical understanding of the key processes - thermal and non-thermal escape. Such improved models of the neutral escape will lead to a better understanding of the paleoclimate and the evolution of the of primary and secondary atmospheres of terrestrial planets (Massol et al., 2016). It is known, that a prediction of escape rates due to thermal and nonthermal processes defines the long-term evolution of planetary atmospheres, therefore atmospheric escape has long been a subject of interest in the comparative planetology, and in recent years especially in understanding of the evolution of exoplanet atmospheres. A critical feature is that escape occurs in the rarefied atmosphere, which is usually called the exosphere, where the state of the gas is significantly nonequilibrium. Accordingly, continuum models are no longer applicable, so that only kinetic modeling at the molecular level of the description allows us to accurately predict the structure of the atmospheric gas flow and escape rate. The report presents the kinetic approach to the problem of neutral escape from planetary atmospheres. As an example, the recent measurements by Mars Express and MAVEN spacecraft are compared with the calculations of neutral escape with the aim to understand the atmospheric loss at Mars. Also the recent calculations (Ionov et al., 2018) of the mass-loss rates of the exoplanet atmospheres leading to the formation of hot Neptune desert will be presented.
Evidence of a distant decimetric radio source connected to the main flare site: First high temporal and spatial GMRT observations
Bisoi, Susanta Kumar
We present a study of decimetric radio activity, using the high time cadence (0.5 s) and high spatial (12 arcsec) observations at the fixed frequency of 610 MHz imaged by the Giant Meterwave Radio Telescope (GMRT), associated with GOES C1.4 and M1.0 class flares, and a coronal mass ejection (CME) that erupted on 20 June 2015. A bright radio source, associated with the M1.0 flare and CME, is located near the flaring site, while, in contrary, a bright radio source, associated with the C1.4 flare, with no corresponding coronal or magnetic features nearby, is rather located about 500 arcsec away from the flare site. The bright radio source, at the start and during the maximum of C1.4 flare, show burst activity, which coincides with the type-III bursts observed by the Solar Broadband Radio Spectrometer at Yunnan Astronomical Observatory. A multi-wavelength analysis, in combination with potential field source surface extrapolation, is carried out to investigate the genesis of non-thermal radio emitting electrons, which revealed that the distant decimetric radio source, noticed during the C1.4 flare, is connected to the main flare site by a high arching loop. The apparent shift of the location of the bright radio source could have resulted by ducting of electron beams along the high arching loop, which is interacting with other closed and open field structures at the electron acceleration site.
Resolving star and planet formation with ALMA
Bjerkeli, Per
Disks around young stars are the sites of planet formation. As such, the physical and chemical structure of disks have direct impact on the formation of planetary bodies. The innermost disk regions are particularly interesting, due to the potential for planet formation. These are also the regions where winds, capable of affecting the disk build-up itself, are launched magnetically. Until very recently, we have lacked the facilities to provide the necessary observational constraints and insights into what is actually going on the smallest scales during the earliest stages of solar system formation, meaning it is completely uncharted territory.Within the framework of the "Resolving star formation with ALMA" program (PI: P. Bjerkeli), we are targeting young disks and outflows with ALMA in its largest possible configuration (16 km baselines, yielding a resolution of 2-6 au) to zoom in on early disk evolution, outflow launching, and star- and planet-formation. We will here present an overview of the program, focusing on the first/initial results. The first resolved images of outflow launching from a disk were recently reported towards the Class I source TMC1A (P. Bjerkeli, et al., 2016, Nature, 540, 406). Since then, we have continued our observations towards TMC1A and in addition included a younger system in the study. The observations allow us to constrain the detailed kinematics and structure of the disks (D. Harsono et al., in prep.), but also to constrain the launching mechanism and the physical properties of outflows on the smallest scales (e.g. mass and momentum; M. H. D. van der Wiel, et al., in prep.).
The evolution of DARWIN - the current status of wind models for AGB stars
Bladh, Sara
The slow, massive winds observed in evolved asymptotic giant branch stars are usually attributed to a combination of effective dust formation in the dynamic inner atmosphere and momentum transfer from stellar photons interacting with the newly formed dust particles. Dynamical models of the atmosphere and wind calculated with the DARWIN code (Höfner et al. 2016), using this mass-loss scenario, successfully produce outflows with dynamical and photometric properties compatible with observations, for both C-type and M-type AGB stars (e.g. Eriksson et al. 2014, Bladh et al. 2015). In this talk I will present the recent development in the DARWIN wind models for both M-type and C-type AGB star. I will show results from a new large grid of M-type AGB star models, spanning a wide range in effective temperature, mass and lumiosity, as well as results from models for C-type AGB stars at low metallicities, compatible to those in LMC and SMC.
Plenary Session: Near-Field Cosmology and Astrometry
Bland-Hawthorn, Joss
TBA
Transforming Research (and Public Engagement) through Citizen Science
Blickhan, Samantha
Processing our increasingly large datasets poses a bottleneck for producing real scientific outcomes and citizen science - engaging the public in research - provides a solution, particularly when coupled with automated routines. In this talk we will provide a broad overview of citizen science approaches and best practices. We will also highlight in particular recent advances through Zooniverse, the world’s largest platform for online citizen science, engaging more than 1.6 million volunteers in tasks including discovering exoplanets, identifying features on Mars’ surface, transcribing artist's notebooks, and tracking resistance to antibiotics.
Future high-redshift observations of HI kinematics
Blyth, Sarah
Recently, large optical IFU surveys have shown that angular momentum is tightly correlated with galaxy morphology and seems to be a key driver of galaxy formation and evolutionary processes. With SKA-pathfinder instruments coming online this year and the SKA1 hot on their heels, even deeper investigations of the role of angular momentum in galaxy evolution will be possible. In addition to the stellar angular momentum measurements from optical data, we will use radio observations to measure the contribution from the neutral hydrogen (HI) gas which, like most of the angular momentum, is located at larger effective radii than typically probed by IFU surveys. The exquisite sensitivity of these new radio telescopes will enable surveys which will probe HI kinematics (spatially resolved and unresolved) in thousands of galaxies to much higher redshifts than previously possible. I will discuss some of the possibilities for these studies using SKA and its pathfinders.
Testing jet formation in a new sample of radio galaxies
Boccardi, Bia
In the recent years, radio galaxies proved to be the the ideal targets for studies aimed at investigating the launching mechanism of relativistic jets. Inferring the intrinsic properties of the jet base through high-resolution radio observations is, in fact, easier in misaligned objects due to the reduced impact of Doppler boosting and projection effects. So far, very-long-baseline interferometry studies of jet formation have been performed in selected nearby objects (mainly in M87, Cygnus A, and 3C84), and have provided important observational evidence in support of the magnetic launching models.In this talk, I will discuss the attempt to identify a larger sample of radio galaxies suited for such analyses, and I will present first results concerning the collimation properties and the internal structure of the plasma flow in still unexplored sources down to scales of hundreds Schwarzschild radii.
The Parkes Telescope
Bock, Douglas
“The Parkes Telescope is probably one of the most successful research instruments ever built”. This statement is as true today as it was when John Bolton made it in 1973. The nearly 60-year-old structure has been complemented throughout its life with regularly refreshed state-of-the-art instrumentation. Access based on scientific merit engages high impact research teams from around the world. Among its notable achievements are its role in identifying the first quasar (3C273), supporting the first moon landing, mapping neutral hydrogen in the Milky Way, discovering more than half of known pulsars, and discovering Fast Radio Bursts.
VHE Gamma-Ray Observations of Radio Galaxies by H.E.S.S.
Boettcher, Markus
Only a handful of radio galaxies have been detected invery-high-energy gamma-rays with ground-based CherenkovTelescope facilities. The theoretical interpretation of the gamma-ray emission seen from these misaligned jet sources remains problematic due to the expected smallDoppler boosting (or even de-boosting). In this talk,I will review recent results from H.E.S.S. and co-ordinatedmulti-wavelength observations of radio galaxies, focusingon two prominent examples, namely Centaurus A, and PKS 0625-354. Centaurus A provides clear evidence fortwo spectral components in the combined Fermi-LAT +H.E.S.S. spectrum, while SED and variability patternsof PKS 0625-354 suggest a blazar-like jet orientation on small scales, contrasting the misaligned large-scalejet structure that led to the source's classification asradio galaxy.
Hot X-ray halos as probes of galaxy formation
Bogdan, Akos
The existence of hot X-ray halos in the dark matter halos of galaxies is a fundamental prediction of galaxy formation models, and hence, observations of these halos can be used to probe the key physical processes that influence the evolution of galaxies. Although hot halos are well explored around elliptical galaxies, these halos remained unexplored around spiral galaxies for several decades. Our group played a key role in detecting several X-ray halos around massive spiral galaxies using Chandra and XMM-Newton observations. We have characterized the properties of these hot halos, and confronted the observed results with those predicted by state-of-the-art hydrodynamical galaxy formation models. This comparison pointed out that the properties of hot halos are extremely sensitive to the incorporated physics in the simulations, and hence observations of X-ray halos provide a powerful method to constrain the physical processes that play an essential role in the evolution of galaxies from the early Universe to the present epoch.
CALSPEC: HST Spectrophotometric Flux Standards from 0.115 to 30 µm
Bohlin, Ralph
The STIS and NICMOS low dispersion spectometers on the Hubble Space Telescope (HST) have flux calibrations tracable to the three unreddened, pure-hydrogen WDs, G191B2B, GD153, and GD71, which are in the effective temperature range 33590–59000 K. STIS covers the 0.115–1 µm range with 5 gratings at a resolution of R~500, while NICMOS has three grisms covering 0.8–2.5 µm at R~100. The fluxes, i.e. spectral energy distributions (SEDs), of these primary standard stars are established using the Rauch Tu ¨bingen NLTE model atmosphere code to determine the relative flux vs. wavelength. Alternate NLTE Tlusty models for the same temperature and gravity differ in their relative flux distributions and are used to define the systematic uncertainties. The absolute normalization of the three models is from a weighted average of the absolute flux of Vega at 5556 °A and the MSX absolute flux measures of Sirius at 8–21 µm. The result of this reconciliation of the visible and mid-IR implies a flux for Vega at 5556 °A of 3.44 erg cm-2 s-1 °A-1 ±0.5%.Once calibrated using the three standard candles, the STIS and NICMOS spectrographs on HST measure the absolute flux of secondary stars from 0.115–2.5 µm. The SEDs of several dozen secondaries and the three primary stars reside in the CALSPEC1 database along with the covariance error matrix of uncertainties. Challenges to achieving the goal of 1% precision in the measured CALSPEC fluxes include non-linearities, changing sensitivity with time, and the high premium on HST time. However, synthetic photometry from the CALSPEC stars agrees with precision Landolt photometry to ~1% (10 mmag) in the B, V, R, and I bands. Model stellar atmospheres that fit these measured SEDs to ~1% extend the wavelength range to the JWST limit of 30 µm.1 www.stsci.edu/hst/observatory/crds/calspec.html
On the turbulent life of disk galaxies in distant clusters
Böhm, Asmus
I will present first results from VLT-KMOS integral field spectroscopy of galaxies in two evolving clusters at redshift z=1.5. Our targets were selected from narrow-band imaging of the HyperSuprimeCam Survey and are following the star formation main sequence at their redshift. The KMOS data cubes of 26 cluster galaxies allowed to extract extended Halpha rotation velocity fields. We found a high fraction (>50%) of kinematically disturbed objects. Only roughly one third of the galaxies with derived kinematics are regular rotators, in the sense that they establish a rotation velocity-stellar mass (Tully-Fisher) relation. Including a comparison to our own studies at lower redshifts, I will discuss the connection between galaxy evolution and environment during cluster build-up 9 Gyr ago.
The Interstellar Medium and Star Formation in Dwarf Galaxies
Bolatto, Alberto
I will review our understanding of the properties of the interstellar medium (ISM) in dwarf galaxies in connection to their star formation activity. What are the dominant phases of the ISM in these objects? How do the properties of these phases depend on the galaxy properties? What do we know about their cold gas content and its link to star formation activity? Does star formation proceed differently in these galaxies? How does star formation feedback operate in dwarf galaxies? The availability of observations from space-based facilities such as FUSE, Spitzer, Herschel, and Fermi, as well as observatories such as SOFIA and ALMA, is allowing us to make significant strides in our understanding of these questions.
Identification of asteroid families older than 2 billion years
Bolin, Bryce
Asteroid families are the remnant fragments of asteroids broken apart by collisions. There are only a few known Main Belt (MB) asteroid families with ages greater than 2 Gyr (Brož et al., 2013; Spoto et al., 2015). Estimates based on the family producing collision rate suggest that the lack of > 2 Gyr-old families may be due to a selection bias in classic techniques used to identify families. Family fragments disperse in their orbital elements, semimajor axis, a, eccentricity, e, and inclination, i, due to secular resonances and the non-gravitational Yarkovsky force. This causes the family fragments to be more difficult to identify with the hierarchical clustering method (HCM), which attempts to find cluster in orbital element space, when applied to family fragments’ elements as the fragments age. We have developed a new technique that is insensitive to the spreading of fragments in e and i by searching for V-shaped correlations of family members in a and asteroid diameter, D. A group of asteroids is identified as a collisional family if its boundary in the a vs. 1/D plane has a characteristic V-shape which is due to the size dependent Yarkovsky effect. The V-shape technique is demonstrated on the known families and families difficult to identify by HCM, and used to discover a 4 Gyr-old family linking most dark asteroids in the inner MB not included in any known family (Delbo' et al., 2017). The 4 Gyr-old family reveals asteroids with D > 35 km that do not belong to any asteroid family implying that they originally accreted from the protoplanetary disk and support recent theories on the formation of asteroids (Morbidelli et al., 2009).
Identification of asteroid families older than 2 billion years
Bolin, Bryce
Asteroid families are the remnant fragments of asteroids broken apart by collisions. There are only a few known Main Belt (MB) asteroid families with ages greater than 2 Gyr (Brož et al., 2013; Spoto et al., 2015). Estimates based on the family producing collision rate suggest that the lack of > 2 Gyr-old families may be due to a selection bias in classic techniques used to identify families. Family fragments disperse in their orbital elements, semimajor axis, a, eccentricity, e, and inclination, i, due to secular resonances and the non-gravitational Yarkovsky force. This causes the family fragments to be more difficult to identify with the hierarchical clustering method (HCM), which attempts to find cluster in orbital element space, when applied to family fragments’ elements as the fragments age. We have developed a new technique that is insensitive to the spreading of fragments in e and i by searching for V-shaped correlations of family members in a and asteroid diameter, D. A group of asteroids is identified as a collisional family if its boundary in the a vs. 1/D plane has a characteristic V-shape which is due to the size dependent Yarkovsky effect. The V-shape technique is demonstrated on the known families and families difficult to identify by HCM, and used to discover a 4 Gyr-old family linking most dark asteroids in the inner MB not included in any known family (Delbo' et al., 2017). The 4 Gyr-old family reveals asteroids with D > 35 km that do not belong to any asteroid family implying that they originally accreted from the protoplanetary disk and support recent theories on the formation of asteroids (Morbidelli et al., 2009).
Magnetic field in galaxy clusters: observations, simulations and theoretical models
Bonafede, A.
TBA
Inferences of the Deep Solar Meridional Flow
Böning, Vincent
Here, I present the main results from my PhD. thesis, to which a number of publications are entering.The solar meridional flow is a crucial ingredient in modern dynamo theory. Seismic estimates of this flow have, however, been contradictory in deeper layers. Here, we develop and validate a method for computing spherical Born approximation kernels for time-distance helioseismology and we employ these kernels to invert for the deep solar meridional flow using 652 days of GONG data from 2004 – 2012.Above about 0.85 solar radii, our inversions confirm the result obtained by Jackiewicz et al. with the ray approximation regarding the general structure of the flow. This especially concerns a shallow return flow at about 0.9 solar radii, although some differences in flow magnitude are apparent.Below about 0.85 solar radii, we obtain several different results that are consistent with the measured travel times within the measurement errors. While one result is similar to the original single-cell flow found by Jackiewicz et al., the other results exhibit a multi-cell flow structure in the southern hemisphere. To reach an unambiguous conclusion on the meridional flow in this region, the errors in the measured travel times have to be considerably reduced.We conclude that an unambiguous detection of the meridional flow is limited to a much shallower region than previously thought. This is a partial relief to the controversy about measurements of the deep solar meridional flow.
Plenary Session: Stellar physics and chemistry in the ELT era & ELTs
Bono, G.
TBA
Understanding diffuse baryons in galaxy clusters with simulations
Borgani, Stefano
In my talk I will review the state-of-the-art in the description of the thermo- and chemo-dynamical properties of the intra-cluster medium (ICM) using cosmological hydrodynamic simulations. I will hyghlight how the inclusion of different sources of stellar and AGN feedbaack allow modern simulation codes to produce populations of synthetic clusters that reproduce several observational properties, such as the mass of the brightest cluster galaxies, the cool-coreness and the pattern of metal enrichment of the ICM. In particular I will highlight how the combined study of the metal enrichment in the external regions of the ICM and future observations of proto-clusters at redshift z~2 would provide unique information about the history of feedback and of the cosmic cycle of baryons in the cluster environment.
The structure and strength of meteorite producing meteoroids
Borovicka, Jiri
Meteorites are the best studied macroscopic samples of interplanetary material. They represent, however, only the strongest parts of the meteoroids they are delivering them. Almost all meteoroids fragment to some extent during their passage through the Earth’s atmosphere. The strength of the fragmenting body can be roughly estimated as the dynamic pressure acting at its front side at the moment of fragmentation: p = ρv2, where ρ is atmospheric density and v is velocity. Previous investigations showed that the strengths are much lower than tensile strengths of meteorites (which are typically 5-50 MPa). The low strengths are probably caused by internal cracks acquired during collisions in interplanetary space. We analyzed seven falls of ordinary chondrite meteorites with good data on atmospheric trajectories, velocities and light curves from the cameras of the European Fireball Network. A fragmentation model was applied to the data in order to reveal fragmentation points and to estimate the fragmented mass. The sample was supplemented with several other meteorite producing fireballs where the meteorites were not recovered. This way, stony meteoroids ranging in size from ~10 cm to about two meters were analyzed. It was found that meteoroid strengths are not random and cumulate in two regions, 0.04 -0.12 MPa and 1-3 MPa in most cases. There are therefore two types of cracks, which we call weak ones and common ones. Weak cracks are not always present, the common ones are only rarely absent (e.g. in the Carancas crater-forming meteoroid). For comparison, we analyzed also the carbonaceous meteorite fall Maribo. Though the data are restricted it is obvious that that meteoroid behaved differently and fragmented all the way along the trajectory. We found no evidences for rubble pile meteoroids. Even bodies that re-accumulated from different meteorite types (e.g. Benešov) have bulk strengths similar to that of weak cracks.
Asteroid Family-Forming Events and Their Connections to Impact Showers
Bottke, William
Asteroid collisional breakups and the dynamical evolution of their fragments have helped shape the main asteroid belt. These processes not only give us insights into planetesimal formation/evolution but they also help us understand terrestrial planet impact histories. We can broadly characterize these processes over the last few Gyr with this sequence of events: (1) A large asteroid in the main belt undergoes a catastrophic collision that creates a swarm of smaller fragments close to the impact site.. (2) Family members with diameter D < 30 km obtain mobility from non-gravitational forces such as the Yarkovsky effect, defined as a thermal radiation force that causes asteroids to drift in semimajor axis via the absorption and reemission of sunlight. Smaller fragments drift faster than bigger ones, such that the family’s orbital distribution can be used “as a clock” to date the time of the break-up. (3) Some fragments migrate into planetary resonances that drive them onto planet-crossing orbits. A few go on to strike the terrestrial planets. The history of asteroid breakups, therefore, is partially constrained by our knowledge of near-Earth objects and craters on inner solar system worlds (and vice versa). Here we will discuss recent advances in our attempts to link changes in the impact history of the Earth and Moon to the evolution of specific asteroid families (e.g., Baptistina, Flora, Gefion). A few large and well-placed families are likely connected to substantial changes in the impact flux of inner solar system worlds, but the precise timing and magnitude of these impact showers, as well as the evidence supporting changes in the impact flux, remain interesting issues for on-going work.
Modelling the rotation of icy satellites with application to exoplanets
Boue, Gwenael
The rotation dynamics of terrestrial exoplanets plays an important role in their physical evolution. It affects not only the climate at their surface, but also the amount of energy produced by tides. Indeed, most of the known rocky exoplanets orbit close to their parent star and are thus subject to strong tidal dissipation. Moreover, many of them are in multiplanetary systems where non vanishing eccentricities and inclinations perturb their rotation. Until recently, studies of exoplanet deformation relied on oversimple models of tides. In the last years, physically motivated rheologies have been introduced but exoplanets are still mostly described as homogeneous bodies. We may nonetheless expect some of them to be composed of a solid crust floating on a viscous mantle with a solid core, as in the case of the Earth for instance. This type of internal structure enriches the dynamics but it also requires an efficient mathematical formalism allowing to explore large parameter spaces.In our solar system, several icy satellites hold an underneath ocean making them composed of three layers as described above. Furthermore, these bodies have been accurately analysed thanks to spacial missions. This enables to test complex internal models against observations. In the case of Titan, for example, an obliquity of 0.3 degree---which cannot be explained if this satellite were entirely rigid---as been measured by the Cassini mission. In this talk, we will present our fully analytical three-layer model based on a Hamiltonian formalism. The agreement with the observations and with an hydrodynamic code will be shown. And finally, the application to the exoplanet field will be discussed.
The first president of the IAU, Benjamin Baillaud
Bougeret, Jean-Louis
Benjamin Baillaud was appointed president of the First Executive Committee of the International Astronomical Union which met in Brussels during the Constitutive Assembly of the International Research Council (IRC), on July 28th, 1919. He served in this position until 1922, at the time of the First General Assembly of the IAU which took place in Roma, May 2-10. At that time, Baillaud was director of Paris Observatory. He specialized in celestial mechanics, and he was a strong supporter of the Carte du Ciel project. He also was the founding president of the Bureau International de l'Heure (BIH).We will briefly present some of his activities, particularly those concerning international programs and the building of the IAU.
Dynamics, temperature, chemistry, and dust: ingredients for a self-consistent AGB wind
Boulangier, Jels
For decades it has been known that the mass loss of evolved, low-mass giant stars is one of the major contributors to the chemical enrichment of galaxies. Yet, the actual mechanisms governing this mass loss still elude us. The general hypothesis is that the mass loss of these Asymptotic Giant Branch (AGB) stars is generated by a combination of pulsations and radiative pressure on dust grains. However, the physical and chemical conditions of AGB winds are poorly understood. Considerable effort has been made in modelling these winds dynamically and radiatively. Yet, all studies assume gas-phase chemical equilibrium.We have developed a self-consistent hydrochemical model, improving on the current wind models. This approach is needed because of the intricate interplay between dynamics and chemistry that is caused by shocks and cooling/heating processes. The chemical composition determines which cooling/heating mechanisms influence the thermal evolution of the gas. In turn, the temperature acts on the dynamical behaviour of the wind which again will impact the rate of chemical reactions. Therefore, we take into account most important chemical reactions and thermal mechanisms.Our initial results strengthen the hypothesis that dust is necessary to drive these stellar winds. They also predict that ideal dust formation conditions (i.e. cold and dense) could arise close to the star. Because of this, we've included kinetic nucleation theory for TiO2 and Al2O3, whose large clusters can act as seeds for dust formation. Hereby, we eliminate the need for assumptions on seed particle abundances and their position in the wind. The seeds can then grow to become larger dust grains via dust formation/destruction mechanisms. This seed-to-dust approach allows to more self-consistently predict abundances and grain size distribution across the stellar winds.This work lays the basis for dust-gas chemistry complemented with dust acceleration, striving for a more accurate AGB wind model.
Data for Development: a Global Perspective
Boulton, Geoffrey
The generation and application of new knowledge and the technologies by which we acquire and disseminate it, have always been the most powerful drivers of human material and social progress. The replacement of analogue processes by digital processes of acquisition, analysis and transmission of data and information in the early years of the 21 st century have ushered in a digital revolution of world historic significance in the way that knowledge is acquired, transmitted and used. It has created enormous potential for scientific discovery, for efficiency and productivity in business, the economy and education, for socio-political innovation, and for the minimization of risk. Whole societies are struggling to understand and harness this potential. The SDGs represent the most ambitious, most coherent set of objectives that the international community has ever committed itself to. The tools of the digital revolution have by far the greatest potential impact on the realisation of those goals. It is vital that we exploit them. For these reasons that ICSU-CODATA, regional bodies and international partners have been working to develop the means to exploit this revolution through the creation of regional Open Science Platforms. For example, inspired by the collaborations developing through the Square Kilometre Array, a Pan-African vision is being realised in the building of a digital ecosystem, the African Open Science Platform, with the aim of supporting researchers in finding, depositing, managing, sharing and reusing data; to develop capacities at all levels of national science systems; and as a forum for exchange of ideas, best practices and opportunities. A parallel international programme is also being developed to create the procedures that will permit integration of the data that underpins key issues for the SDGs, initially in the domains of infectious disease, disaster risk reduction, resilient cities and agriculture.
The impact of the APOGEE Survey on Galactic metallicity gradients
Bovy, Jo
Determining the structure of the Milky Way is one of the oldest problems in astronomy and yet it still has surprises in store. A new generation of surveys is expanding our high-resolution view of stellar populations in the Milky Way from a small region around the Sun to the entire radial range of the stellar disk. I will present new results on the global chemical and spatial structure of the disk from the APOGEE survey. These results challenge long-held assumptions about the basic structure of galactic disks, the importance of mergers for their evolution, and the physical conditions under which stars form throughout cosmic time.
Mapping the Milky Way's dark matter with high-precision astrometry
Bovy, Jo
Stellar tidal streams originating from disrupting globular clusters in the Milky Way’s halo hold enormous promise as probes of both the large-scale structure of the Milky Way halo’s density distribution and its small-scale structure. As such, the observed density, spatial, and kinematic structure of stellar streams can provide important new constraints on the interactions and small-scale structure of dark matter. I will discuss recent progress on modeling the dynamics of stream formation and its application to fitting observed stellar stream data from photometric, spectroscopic, and astrometric observations. I will in particular focus on the crucial role of high-precision astrometry in mapping the small-scale structure of streams and how this will help answer the fundamental question: Is dark matter cold?
The Impact of AGB Stars on Galaxies
Boyer, Martha
At the end of their evolution, asymptotic giant branch (AGB) stars undergo strong pulsation, mass loss, and dust production. Their mass loss results in substantial chemical and dust enrichment of the interstellar medium. Dust evolution models and isotope abundances in presolar grains suggest that AGB stars play a key role in both dust evolution and the star formation process. They are also the brightest stars in galaxies, potentially dominating in the near-infrared. As a result, AGB stars have a significant influence on the evolution and appearance of their host galaxies and thus must be accounted for when interpreting a galaxy’s integrated light. I will review the current understanding of the impact AGB stars have on galaxies, highlighting new observations of AGB stars in nearby galaxies and recent advances in modeling. Finally, I will comment on how future observations with upcoming telescopes could impact our understanding of this important phase of stellar evolution.
IGR J17329-2731: the birth of a symbiotic X-ray binary
Bozzo, Enrico
I will report on the results of the multi-wavelength campaign carried out after the discovery of the INTEGRAL transient IGR J17329-2731. The optical data collected with the SOAR telescope allowed us to identify the donor star in this system as a late M giant at a distance of 2.7(+3.4,-1.2) kpc._x000D_ The data collected quasi-simultaneously with XMM–Newton and NuSTAR showed the presence of a modulation with a period of 6680±3 s in the X-ray lightcurves of the source. This unveils that the compact object hosted in this system is a slowly rotating neutron star. The broad-band X-ray spectrum showed the presence of a strong absorption (_x001D_10^23 cm^−2 ) and prominent emission lines at 6.4 keV, and 7.1 keV. These features are usually found in wind-fed systems, with the emission lines resulting from the fluorescence of the X-rays from the accreting compact object on the surrounding stellar wind. The presence of a strong absorption line around ∼21 keV in the NuSTAR spectrum suggests a cyclotron origin, thus allowing us to estimate the neutron star magnetic field as ∼2.4×10^12 G. All evidence thus points to IGR J17329-2731 being a symbiotic X-ray binary._x000D_ As no X-ray emission was ever observed from the location of IGR J17329-2731 by INTEGRAL during the past 15 yr in orbit and considering that symbiotic X-ray binaries are known to be variable but persistent X-ray sources, we concluded that IGR J17329-2731 was most likely caught by INTEGRAL when the source shined as a symbiotic binary in X-rays for the very first time. The Swift XRT monitoring_x000D_ performed up to ∼3 months after the discovery of the source, showed that it maintained a relatively stable X-ray flux and spectral properties. This supports the idea that IGR J17329-2731 might have become a persistent X-ray source in our Galaxy.
GW170817: multi-messenger observations of a binary neutron star merger
Branchesi, Marica
The detection of the first signal from the colascence of two neutron stars by the Advanced LIGO and Virgo interferometers gave rise to the largest multi-messenger observational campaign ever. The discovery of an optical counterpart in NGC4993 was followed by late X-ray and radio detections. The collected multi-messenger data confirmed theoretical models developed years ago. But at the same time, the richness of details of the data required to develop new scenarios to be interpreted. The talk will give a summary of the multi-messenger observations, intepretation and astrophysical implications.
The new exploration of the Universe through gravitational-wave observations
Branchesi, Marica
The experiments to develop gravitational-wave detectors have recently become observatories able to detect transient gravitational-wave signals. This led to ground-breaking discoveries, which started on September 14, 2015, with the first detection of gravitational waves from the coalescence of a binary system of black holes by the Advanced LIGO detectors. Another epochal discovery happened on August 17, 2017, with the first observations of gravitational waves from the inspiral and merger of a binary neutron-star system by the Advanced LIGO and Virgo network, followed 1.7 s later by a weak short gamma-ray burst detected by the Fermi and INTEGRAL satellites. A world-wide observing campaign involving about 100 instruments led to the detection of multi-wavelength electromagnetic signals associated with this event. A new exploration of the most energetic transients in the sky started. The talk will give an overview of the recent gravitational-wave and multi-messenger observations, their astrophysical implications and the prospects for the upcoming years.
The Baryon and Metal Content of Halos of Galaxies
Bregman, Joel
TBA
Arcus: Exploring the Formation and Evolution of Structure in the Universe
Bregman, Joel
TBA
Research on Astronomy Education
Bretones, Paulo
The goal of this talk is to show the activities of the IAU WG on Theory and Methods in Astronomy Education. Initially the history, needs and goals of the WG are addressed. Then, the main project on the surveys is discussed. The project includes literature reviews of scholarly production that already exists on PhD and MSc theses, published papers in journals and works in proceedings of meetings. The steps to be followed for the surveys are sketched: 1) Provide a list of references; 2) Get the pdf files of works; 3) Make them available online; 4) Analyze and classify the works by: year of publication, the authors' institutions, school level, study focus in education, content, kind of academic work, theoretical framework; 5) Publish papers about the results showing trends and gaps in the production. The surveys made from some countries and the setup of the WG webpage are shown as examples of the latter procedure. As an example of survey of thesis, make their references available and publish a paper with the analysis, made in Colombia is presented. A talk entitled “Astronomy Education Research: impact and future directions", in the ise2a meeting held in Utrecht, 2017 given by this author presented the results of the consult to the WG and C1 members about the achievements and challenges of AER. We hereby focus on the challenges about how to: promote surveys in more countries and languages; encourage new studies and bind together the community; give visibility to the productions and encourage the teachers in the schools, students, professors and researchers of universities; and finally obtain the indexation of the publications in ADS, Google Scholar etc. Even though researchers on education and astronomers belong to different communities, in this project their collaboration is very fruitful. One of the achievements was the new Associate Members, invited because of the contribution they have done. Therefore, we invite the colleagues to join us for collaboration.
Overview of the AER landscape
Bretones, Paulo
When the landscape of a research area is analyzed, its scientific production is mainly identified by the following publications: theses, monographs, conference proceedings and journal articles. The present work deals with review articles published in Astronomy Education Research (AER), their results and suggestions. Later on we present surveys based on categories like: year, institution, school level, focus of the study in education, type of academic research and the theoretical framework taken from IAU, RELEA and other sources. These surveys show trends and gaps, already discussed in the literature of the area and point towards the less addressed contents and recommendations for further work. The answers to a questionnaire of IAU CC1 and WG on Theory and Methods in Astronomy Education members about the achievements and challenges of AER are discussed. Recent surveys of publications from some countries are also shown evidencing the dispersion of AE literature. The role and goals of astronomy teaching are discussed next considering contents, methods, levels, resources and purposes. Given the needs and complexity of education nowadays and the role of astronomy in this context, the potential of education research is also evaluated, considering knowledge, practices, policies and the training of teachers. The formation of a community in an area where the astronomers are trained as scientists and the need of training of education researchers are considered. About this, the different approach of hard sciences, very different from the social sciences in which education is inserted is pointed out and discussed. Finally, collaborations for surveys, literature reviews and the advertisement of such materials, aiming to strengthen the training of researchers and the practitioners as well are also encouraged.
A history of IAU Commission C1: a look from the Newsletters
Bretones, Paulo
TBA
Early planetary atmospheres and surfaces, origin of the Earth's water, crust and atmosphere
Breuer, Doris
The origin of early planetary atmospheres is controversially discussed. There are two competing models, i.e. the atmosphere is either formed by outgassing from the interior or by a late delivery from comets or volatiles-rich asteroids after most of the planet has been formed. Of these models, the former is currently preferred. Meteorite compositions as well as radial mixing during accretion derived from planetary formation models suggest that the building blocks of the terrestrial planets contained some volatiles. Processes like dehydration by hydrous melting, oxidation, impact devolatilization, and in particular degassing during magma ocean solidification lead to a significant volatile loss of the interior and to the formation of a dense atmosphere during the early stages of planetary evolution. These processes also influenced the oxidation state of this early atmosphere, i.e. whether it was more strongly reduced or oxidized.Despite the efficient volatile loss, some water likely remained in the interior and was redistributed between silicate mantle, crust and atmosphere in the subsequent evolution. Under favourable temperature and pressure conditions, which depend on atmospheric pressure, composition and solar radiation, atmospheric water vapour condenses and precipitates on the surface. The main processes responsible for the redistribution of water are volcanic outgassing by partial melting of the silicate mantle and associated formation of the crust and recycling of water-rich crustal material. An important difference between the terrestrial planets is the predominant tectonic style on the planet. For the Earth with its plate tectonics, recycling of water is very efficient and can even balance the outgassing. For terrestrial planets in the stagnant lid regime of mantle convection such as Mars, the exchange of water between the interior and the surface/atmosphere is mainly in one direction and results in a continuous depletion of the interior.
Understanding the assembly histories of early-type galaxies from the kinematics of stars and globular clusters
Brodie, Jean
The SAGES Legacy Unifying Galaxies and GlobularS (SLUGGS) survey has generated large-scale, spatially resolved stellar kinematic data, along with high precision velocities for thousands of globular clusters (GCs), out to many effective radii in nearby early-type galaxies (ETGs). Although challenging to observe, the outskirts of galaxies retain valuable information about their assembly histories because of their longer dynamical time-scales and the fact that the majority of a galaxy’s angular momentum resides in its outskirts. We compare the kinematic properties of our galaxies with those from various simulated galaxies. Similarities and differences between predictions from simulations and these observational constraints are challenging our popular scenarios for ETG formation.
Epoch of Merger-Driven Star Formation and AGN in High Redshift Clusters
Brodwin, Mark
Over the last few years, studies of distant galaxy clusters have found compelling evidence for a major epoch of merger-driven star formation and AGN fueling in z > 1 galaxy clusters. I will briefly review the observations from the IRAC Shallow and Distant Cluster Surveys (ISCS/IDCS) that contributed to this new paradigm, and discuss new observations that extend it in both redshift (to z = 1.75) and mass (to M > 10^15 Msun) in the IDCS, SPT and other surveys. As a case study I'll highlight the z = 1.75 IR-selected cluster IDCS J1426.5+3508 that, with a mass of 4 x 10^14 Msun, is the most massive cluster known at z > 1.5. This extremely distant cluster has high levels of both star formation and AGN activity, yet is a relaxed, self-similar, cool-core cluster apparently in hydrostatic equilibrium.
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.
How Do Galaxies Populate Low Mass Halos?
Brooks, Alyson
In just a few short years the Large Synoptic Survey Telescope will begin survey operations, leading to the discovery of hundreds of Local Group dwarf galaxies, including hundreds of dwarf galaxies in the untra-faint regime. These tiny galaxies provide a test of both our understanding of dark matter and of star formation. But are we ready for these discoveries? Will be able to easily interpret the information that they hold? In this talk, I will highlight uncertainties in our theoretical modeling that lead to degenerate predictions that will complicate our interpretation of even pure dwarf galaxy number counts. I will also discuss potential paths toward breaking degeneracies, and identifying the clues that dwarfs will provide about the physical conditions necessary for the earliest star formation.
Ultraviolet Surveys: the needs and the means
Brosch, Noah
This is a crucial time in the history of astronomy with major all-sky surveying work being carried out in all spectral bands, as well as in astrometry. The results of this activity are advancing all fields of astrophysical research, from the investigation of exo-planetary systems to the study of the chemical evolution of the Universe. Full sky surveys are available from the radio domain to X-ray wavelengths but not in the ultraviolet range (UV). While large UV missions are currently under discussion within the astrophysical community and at the major Space Agencies, the efficient use of resources requires preparatory work that can fill the UV surveying gap. This contribution address the on-going activities in this field.
Gaia Data Release 2
Brown, Anthony
An overview of Gaia DR2 will be presented focusing on the photometry, radial velocities, astrophysical parameters, and variable stars.
Precise measurements of galaxy spectral energy distributions
Brown, Michael
We present spectral energy distributions of individual galaxies and quasars spanning from 0.1 to 35 microns (and in some instances 0.1 to 300 microns). Spectral energy distributions are used for photometric redshifts, k-corrections, star formation rate calibrations, exposure time calculators, modelling object selection and validating photometry. The spectral energy distributions incorporate (but are not limited to) photometry and spectroscopy from FUSE, IUE, Hubble, SDSS, PanSTARRS, Skyampper, IRTF, GNIRS, XShooter, Akari, Spitzer and WISE. Accurate calibration and measurement of photometry and spectrophotometry was critical to the construction of our spectral energy distributions, and we identified and mitigated background over-subtraction, filter curve errors and photon coincidence losses (for extended sources). The WISE W4 effective wavelength error in particular illustrates how non-stellar sources can be used to identify and mitigate calibration errors. The templates have also been used to identify and mitigate wavelength dependent errors in GAMA survey photometry.
Plenary Session: The GAIA Mission and the GAIA Mission Extension
Brown, Anthony
TBA
Julia asteroid family versus adaptive-optics observations of (89) Julia
Broz, Miroslav
There is a small family in the vicinity of (89) Julia. Our preliminary analysis assured the family can be associtated with this 140-km asteroid, given its large escape velocity of about 100 m/s. We then constructed an N-body orbital model, Monte-Carlo collisional model, and an SPH simulation of the respective event. We fully explain the distribution in the space of proper elements, and determine the dynamical age to be 10 to 100 Myr. The size-frequency distribution clearly corresponds to a cratering event, with the (transient) crater size reaching 60 km according to the SPH.This is spectacularly confirmed by direct observations of (89) Julia. ESO VLT/SPHERE/ZIMPOL adaptive-optics instrument allowed us to acquire 40 images, which were deconvolved using a stellar PSF, and Mistral algorithm. The pixel scale is 3.6 mas which correponds to 3 km at the distance of Julia. For the inversion and shape reconstruction, 38 additional light curves, and 2 occultations were used. The resulting shape indicates there are three craters, with rim-to-rim sizes ranging from 40 to 70 km. We can even prefer one of them, because it is located on the southern hemisphere which seems to be more suitably oriented with respect to the family. For the first time, we were able to suggest such a link solely on the basis of ground-based observations. This may be considered a beginning of a new era of asteroid-family studies, which shall include families -> craters identifications.
Dynamics of protoplanets embedded in gas/pebble disks and its complex dependence on parameters
Broz, Miroslav
Several-Earth-mass protoplanets interact with the gaseous and pebble disk in a complex way. The hot-trail effect arises as a consequence of accretion heating, it raises planetary eccentricities, and may prevent resonant captures of migrating planets (see Chrenko et al. 2017, or Eklund & Masset 2017). Here we study the dependence of this effect and subsequent evolution on parameters such as the surface density, viscosity, pebble flux, mass, or the number of protoplanets. For modelling we use Fargo-Thorin 2D hydrocode which incorporates all necessary terms.In particular, for a disk with high surface density (3x MMSN) there are numerous "unsuccessful" two-body encounters which do not lead to a merger or a coorbital. Only later, when the 3rd embryo arrives to the convergence zone, three-body encounters lead to mergers. For a low-viscosity disk (10-6 in code units) there is a massive coorbital (two times 8 ME) as a possible outcome, for which a pebble isolation develops and the coorbital is further stabilised.Interestingly, for many low-mass protoplanets (120 times 0.1 ME) the dynamics is totally different, mostly because the spiral arms overlap with each other and affect not only a single protoplanet but many in the surroundings. The evolution of semimajor axes and eccentricities is no longer smooth, but rather random-walk. The latter task is computationally very expensive, because we need to resolve the Hill sphere, both in radial and tangential directions, fulfil the Courant condition, and compute disk->planet interactions for all of them, so it essentially scales as N4.
Magnetic fields in the intergalactic medium and in the cosmic web
Brueggen, M.
TBA
Probing restarting activity in soft gamma-ray selected giant radio galaxies
Bruni, Gabriele
Cross-correlating the INTEGRAL/IBIS - Swift/BAT AGN population with radio catalogs (NVSS, FIRST, SUMSS), we found that 25% of extended radio sources are Giant Radio Galaxes (GRG), i.e. the largest individual objects in the Universe. This fraction is four time more abundant than what found in previous studies. In 2014, we observed a pilot sample of these soft-gamma ray selected GRG at low radio frequencies with the GMRT, with the aim of studying the morphological and spectral properties of these objects. Thanks to these data, we discovered the second X-shaped GRG to date, and a previously unidentified radio galaxy. Another object, observed both at kpc and pc scales (VLBI), showed an extreme jet re-orientation (about 90 degrees). Moreover, the majority of these objects show signs of restarting activity from previous observations in the literature.Given these intriguing premises, we embarked on a radio observing campaign, using both single dish (Effelsberg) and interferometers (VLBA), to probe the lifecycle of these soft gamma-ray selected GRG. The results of this campaign will be presented, that potentially shed light on the origin and evolution of the radio phase for this extreme class of objects (and radio-loud AGN in general), and the connection with high-energy emission. The X-ray properties, and in particular the correlation between the X-ray luminosity of the AGN and the radio luminosity of both the core and the lobes, will be discussed as well.
The Role of TP-AGB and P-AGB Stars in Stellar Populations
Bruzual, Gustavo
Thermally pulsing AGB (TP-AGB) stars contribute a large fraction of the NIR emission in intermediate age stellar populations. Post AGB (P-AGB) stars have proven to be an important source of ionizing radiation in early type galaxies (e.g., Binette et al. 1994). These phases of stellar evolution thus must be treated carefully in population synthesis models aimed to explore the spectral properties of galaxies at different cosmic times. 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.
Status of Cosmic Microwave Background Observations
Bucher, Martin
Observations of the Cosmic Microwave Background (CMB) anisotropy have played a key role in constraining models of the Early Universe and characterizing the initial conditions of the Universe. I will review the current status of CMB observations, emphasizing recent developments. I will also discuss future initiatives and opportunities, in particular efforts from both the ground and space to detect primordial gravitational waves generated during inflation through the B mode CMB polarization anisotropy.
Inversions in helio- and asteroseismology: constraints on chemical mixing processes and the solar modelling problem
Buldgen,
TBA- IAU PhD Prize 2018
HMXBs as progenitors of gravitational wave mergers
Bulik, Tomasz
Formation of merging binary compact objects must be preceded by a stage including a compact object and a non compact massive companion on a relatively tight orbit. At this stage the compact object will be acreting matter from the wind and should be visible as a high mass X-ray binary. I will review the properties of the known high mass X-ray binaries and discuss the possibility that they will lead to formation of coalescing compact object binaries.
From halos to disks: the physics of angular momentum profiles
Bullock, James
The angular momentum distribution of dark matter as derived from dark matter only LCDM simulations provides an important starting point for interpreting galaxy disk sizes, however full hydrodynamics are required to get a complete picture. The gas that builds disk galaxies in the LCDM paradigm is typically accreted as cold along filaments, which are sourced with ~4 times more specific angular momentum than the dark matter. These filamentary cold flows deliver significant mass and angular momentum to galaxy halos, and provide an ample source for building large disk galaxies. A growing body of observational evidence suggests that this process is borne out in the real universe.
Galaxies in the epoch of reionization: the high redshift Universe with ELTs and JWST
Bunker, Andrew
I will discuss the importance of follow-up spectroscopy with ELTs on high redshift galaxies, in particular at z>6 - within the first billion years, and spanning the reionization of the Universe. This field has blossomed in the past 15 years, thanks to the advent of the Hubble Ultra Deep Field, GOODS and COSMOS, coupled with improved near-infrared imaging from the ground. However, a key current limitation is the lack of spectroscopic follow-up for most sources. This means that the contamination rates, exact redshifts, and key spectral diagnostics of stellar populations remain highly uncertain, which has potentially huge implications for the inference of luminosity functions which are key to addressing the assembly of stellar mass in galaxies, and to addressing the question of the role of galaxies in reionizing the Universe. Some progress will be made by JWST NIRSpec in pencil-beam surveys (and I will discuss our joint NIRSpec-NIRCam GTO JWST Advanced Deep Extragalactic Survey, JADES), but a wider-field facility will be more effective in building up the numbers on the rarer brighter sources. Optical/near-IR spectroscopy from the ground on ELTs, working between the sky lines at spectral resolving power R~3000 out to H-band, will be very competitive with JWST sensitivity. ELT MOSAIC, TMT WFOS & IRMS, and GMACS & GMTIFS on GMT, offer great opportunity not only for redshift confirmation, but also for studies of evolution of the ionization state of the IGM with redshift, and the nature of the underlying stellar populations in the most distant galaxies. In particular, potential population-III signatures such as HeII(1640) can be probed. I will discuss the role of ELT spectroscopy in the context of other upcoming high redshift surveys from JWST, Euclid and LSST.
Realistic modeling of collisional water delivery during the late stages of planet formation
Burger, Christoph
Even most state-of-the-art N-body simulations of late-stage planet formation still assume perfectly inelastic merging once two bodies collide. This strong simplification of the actual collision physics falsifies results in general, and particularly for volatile constituents like water, which are in addition found preferentially at or close to the surface. Our aim is to investigate how the outcome of individual collisions can influence the overall picture of water transfer and loss during (terrestrial) planet formation, believed to be one of the most important factors for planetary habitability._x000D_ High resolution Smooth Particle Hydrodynamics (SPH) simulations of self-gravitating, differentiated planetary embryos enable us to study the principal outcome as well as the detailed fate of different materials in collisions, covering all outcome regimes from low-velocity, almost perfect merging, to fast and highly erosive, as well as hit-and-run encounters. The latter are characterized by two instead of one large surviving fragment which makes them complicated to describe, but also interesting and important for studying volatile delivery. While combined (projectile & target) water losses in a single collision can amount to 50% and more – provided large enough impact velocities – more moderate encounters often leave the larger of the colliding bodies relatively intact, while the smaller one is still stripped of a majority of its volatile inventory. Yet higher water losses can be expected once high enough impact energies result in a significant fraction of vaporized volatiles, then potentially subject to atmospheric loss processes._x000D_ Understanding the behavior of water inventories in collisions is a major prerequisite for including realistic modeling of collisions in the upcoming next generation of N-body planet formation simulations.
The Astrometric Gravitation Probe Mission Concept
Busonero, Deborah
The Astrometric Gravitation Probe (AGP) is the concept of a space mission for Fundamental Physics tests in the Solar system, based on high precision differential astrometry, in a modern rendition of the 1919 Dyson-Eddington-Davidson experiment.The key innovation is a space-borne telescope with built-in permanent eclipse provided by a coronagraphic system.The precision goal on the "$\gamma$" and "$\beta$" parameters of the Parametrised Post-Newtonian formulations of General Relativity and competing models is respectively in the $10^{-8}$ and $10^{-7}$ range, improving by one or two orders of magnitude with respect to the expectations on current or near future experiments.Such precision is suitable to detect possible deviations from the unity value (associated to generalised Einstein models for gravitation) in the weak field limit applicable to the Sun neighbourhood, with potentially huge impacts on our understanding of the cosmological distribution of dark matter and dark energy from a Solar system scale experiment.The measurement principle is based on the differential astrometric signature on the stellar positions, i.e. based on the spatial component of the effect rather than the temporal component as in recent experiments using radio link delay timing variation (Cassini).The instrument concept is based on multiple field, multiple aperture Fizeau interferometry, observing simultaneously regions close to the Solar limb, embedding coronagraphic techniques, and other fields in opposition to the Sun.The design is focused on systematic error control through multiple field simultaneous observation and calibration.We describe the science motivation, the proposed mission profile, the instrument concept and the expected performance.Furthermore, we describe the potential for upgrade to larger scale experiments throughout the current century.
A search for warm-hot baryons in the cosmic web using Sunyaev-Zel'dovich effect
Cai, Yan-Chuan
In the context of the standard model, observations of galaxies and galaxy clusters in the local universe can not fully account for the baryon content inferred from measurements of the cosmic microwave background and from big bang nucleosynthesis. Locating the missing baryons has been one of the major challenges in cosmology. Cosmological simulations predict that they are spread throughout filamentary structures in the cosmic web, forming the warm-hot intergalactic medium (WHIM). I will present a recent detection of WHIM in filaments through the thermal Sunyaev-Zel'dovich effect by stacking pairs of galaxies from the SDSS CMASS sample. Part of the talk will be based on this paper: https://arxiv.org/abs/1709.10378.
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.
C60 in interstellar and circumstellar environments
Cami, Jan
In recent years, fullerenes (and in particular C60) have been detected in a variety of astrophysical environments – from the circumstellar carbon-rich surroundings of evolved stars to interstellar reflection nebulae and young stellar objects. Understanding how these species form, evolve and respond to their environment yields important insights into astrochemistry and the characteristics of large aromatics in space, thought to be the main reservoir of organic material in space.In this talk, I will present an overview of what we have learned about cosmic fullerenes from multi-wavelength astronomical observations, theoretical calculations and recent laboratory experiments, and show how fullerenes have significantly changed our understanding of interstellar chemistry. I will discuss the conditions that appear to be conducive to the formation and/or detection of fullerenes, and highlight some of the difficulties we still face in understanding the formation of fullerenes, especially in planetary nebulae.
Radiative Feedback from Massive Stars as Traced by Multiband Imaging and Spectroscopic Mosaics
Cami, Jan
Massive stars disrupt their natal molecular cloud material by dissociating molecules, ionizing atoms and molecules, and heating the gas and dust. These processes drive the evolution of interstellar matter in our Galaxy and throughout the Universe from the era of vigorous star formation at redshifts of 1-3, to the present day. Much of this interaction occurs in Photo-Dissociation Regions (PDRs) where far-ultraviolet photons of these stars create a largely neutral, but warm region of gas and dust. PDR emission dominates the IR spectra of star-forming galaxies and also provides a unique tool to study in detail the physical and chemical processes that are relevant for inter- and circumstellar media including diffuse clouds, molecular cloud and protoplanetary disk surfaces, globules, planetary nebulae, and starburst galaxies.We will provide template datasets designed to identify key PDR characteristics in the full 1-28 µm JWST spectra in order to guide the preparation of Cycle 2 proposals on star-forming regions in our Galaxy and beyond. We plan to obtain the first spatially resolved, high spectral resolution IR observations of a PDR using NIRCam, NIRSpec and MIRI. We will observe a nearby PDR with well-defined UV illumination in a typical massive star-forming region. This will, for the first time, spatially resolve and perform a tomography of the PDR, revealing individual IR spectral signatures from the key zones and sub-regions within the ionized gas, PDR and molecular cloud. These data will test widely used theoretical models and extend them into the JWST era. We will assist the community through several science-enabling products (maps of spectral features, template spectra, calibration of narrow/broad band filters in gas lines and PAH bands, data-interpretation tools e.g. to infer gas physical conditions or PAH and dust characteristics). This project is supported by a large international team of one hundred scientists collaborators.
Synergy between asteroseismology and exoplanet science: an outlook
Campante, Tiago
Over the past decade, space-based asteroseismology has played an important role in the characterization of exoplanet-host stars and their planetary systems. The future looks even brigther, with space missions such as TESS, CHEOPS and PLATO ready to take on this legacy. In this talk, I will start by reviewing current key synergies between asteroseismology and exoplanetary science, such as the precise determination of radii and ages of host stars, the measurement of spin-orbit alignment, and the determination of orbital eccentricity via asterodensity profiling. I will conclude with an outlook on future synergies (e.g., the precise characterization of super-Earths/Neptunes orbiting solar-type stars and the prospect of conducting a populational study of giant planets around evolved stars) and further provide an overview of the asteroseimsic yield of exoplanet-host stars expected for the upcoming TESS mission.
HST Grism/WFC3 observations of XLSSC122, a mature cluster z~2.
Canning, Rebecca
We present HST grism spectroscopy of XLSSC 122 confirming its redshift of z=1.98. This redshift is in good agreement with that derived from spectral fitting of the redshifted X-ray Fe 6.7keV line. The cluster displays a clear red sequence as well as significant AGN activity and SF in the confirmed cluster members. Here we present our cycle 21 HST observations, redshift determination, emission line analysis and analysis of the F105W-F140W cluster colour magnitude diagram.
Surprises in kinematic observations of early-type galaxies
Cappellari, Michele
I will summarize the status of our knowledge on the stellar kinematics of ETGs. I will place particular emphasis on new results and question raised from the large MaNGA integral-field spectroscopy surveys that we did not already know from Atlas3D.
Cosmic Web Research: Where are the Missing Dwarf Galaxies and Inter-Galactic HI Clouds
Carignan, Claude
We know very well that the observed HI content cannot explain the Star Formation Rate (SFR) observed in galaxies. The only way galaxies can sustain that SFR is by accreting HI-rich dwarf galaxies or Inter-Galactic HI clouds. However, no observation to detect those accretion events has been very conclusive so far. Instruments having the necessary sensitivity (e.g. GBT) lack the necessary spatial resolution and those with the proper resolution (e.g. VLA) lack the sensitivity. I will show, with an example, that both are necessary to detect those illusive HI clouds._x000D_ The SKA precursor MeerKAT is starting its operation as we speak and will start the Large Survey Programs at the end of 2018. FAST has started its observations in “drift scan” mode with CRAFTS (Commensal Radio Astronomy Fast Survey) and should be able to start pointed observations in 2019. In the near future (2019-20), the best combination to study low column density HI will be to combine the sensitivity of FAST with the spatial resolution of MeerKAT. The combination of the data from those two telescopes will allow, 4-5 years before SKA1-MID, to do "cosmic web" research to levels < 5 X 1017 cm−2, close to 1016 cm−2, densities that would normally only be accessible to the full SKA around 2030. It is at those densities that we expect the galaxies to connect with the surrounding cosmic web that could feed the observed SFR in galaxies.
Large Radio Facilities (SKA, FAST, MeerKAT) in the era of ELTs.
Carignan, Claude
The 64 antennae SKA precursor MeerKAT is starting its operation as we speak and will start its Large Survey Programs at the end of 2018. FAST, the largest single-dish telescope (500m) has started its observations in “drift scan” mode with CRAFTS (Commensal Radio Astronomy Fast Survey) and should be able to start pointed observations in 2019. During this talk I will try to update you on those two new facilities and on their synergies. In the near future (2019-20), the best combination to study low column density HI will be to combine the sensitivity of FAST with the spatial resolution of MeerKAT. The combination of the data from those two telescopes will allow, 4-5 years before SKA1-MID, to do "cosmic web" research to levels < 5 X 1017 cm-2, close to 1016 cm-2, densities that would normally only be accessible to the full SKA around 2030. It is at those densities that we expect the galaxies to connect with the surrounding cosmic web. Finally, I will briefly address the synergies between those large radio instruments and the optical ELTs.
Phase connected X-ray light curve and He II radial velocity measurements of NGC 300 X-1
Carpano, Stefania
NGC 300 X-1 and IC 10 X-1 are currently the only two robust extragalactic candidates for being Wolf-Rayet/black hole X-ray binaries, the Galactic analogue being Cyg X-3. These systems are believed to be a late product of high-mass X-ray binary evolution and direct progenitor of black hole mergers. From the analysis of Swift data only, the orbital period of the NGC 300 X-1 was found to be 32.8 h. We here merge the full set of existing data of NGC 300 X-1, using XMM-Newton, Chandra and Swift observations to derive a more precise value of the orbital period of 32.794+-0.004 h above a confidence level of 99.99%. This allows us to phase connect the X-ray light curve of the source with radial velocity measurements of He II lines performed in 2010. We show that, as for IC 10 X-1 and Cyg X-3, the X-ray eclipse corresponds to maximum of the blueshift of the He II lines, instead of the expected zero velocity. This indicates that for NGC 300 X-1 as well, the wind of the WR star is completely ionised by the black hole radiation and that the emission lines come from the region of the WR star that is in the shadow. We also present a more detailed analysis of two recent very long XMM-Newton observations of the source, performed on 2016 December 17 to 20.
The ages of young asteroid families
Carruba, Valerio
Young asteroid families are families that formed in timescales of 20 Myr or less. Because of their very young age, chaotic dynamics did not had enough time to erase traces of the event that formed the family. The longitudes of node (and, in some cases, of pericenter) of the family members converge to within a very limited range when integrated backward over the estimated age of the family. The Backward Integration Method (BIM) allows to i) identify family members and ii) estimate the family age with a precision not available for other, older asteroid groups. While this behavior was studied and understood in previous works, discoveries of new asteroids over the last ten years dramatically improved the number of young asteroid families.Here we took advantage of this new larger sample to i) refine the ages of previously studied families, such as Karin, a subfamily of the Koronis asteroid family, Veritas, and Nele, and ii) to obtain preliminary estimates of the age of newly identified asteroid families. Out of 28 asteroid families to our knowledge not previously studied with BIM, we identified 4 groups for which we observe a possible convergence of the angles, and for 3 of them, those of Jones, Kazuya, and 2001 GB11, we obtain an age estimate at 1-sigma probability confidence level.
Resolving gas-phase metallicity gradients of intermediate redshift galaxies with MUSE
Carton, David
We present results from a systematic study on the metallicity properties of 84 intermediate redshift galaxies (0.1 < z < 0.8) using data from the MUSE Guaranteed Time Observing programme. With the MUSE GTO programme we are targeting galaxies across the field and group environments, observing more than 10 fields to a minimum depth of 10h each. In particular we shall present results on the gas-phase metallicity gradients of galaxies in these fields. Metallicity has proven to be an especially interesting probe of galaxy evolution because it traces the effects of gas accretion and wind-driven outflows. However, owing to the limitations of seeing, little is known to date about the resolved metallicity properties of intermediate redshift galaxies. To investigate these barely resolved objects we have developed a forward modelling technique that allows us to correct for the effects of seeing upon the observed metallicity gradient. Using this we find, contrary to other higher redshift studies, that once the star-formation rate is normalized relative to the main sequence, there is no correlation between the star-formation intensity and the metallicity gradient. In addition, we find only a few galaxies (7 out of the 84) with positive metallicity gradients (centres more metal-poor than their outskirts). We note that, while for the smallest galaxies in our sample there is a large spread in the observed metallicity gradients (both negative and positive), we find no large galaxies (rd > 3 kpc) with positive metallicity gradients. Altogether this is suggestive of a secular evolutionary scenario, with the largest (most well-evolved) galaxies been analogous to present-day galaxies, which also show a common negative metallicity gradient.
All sky photometric zero-points from stellar effective temperatures
Casagrande, Luca
I use SkyMapper DR1 to explore the quality of its uvgriz photometry, and zero-points across the sky. Physical flux transformations, and zero-points appropriate for this release are derived. I introduce a formalism to derive photometric zero-points across the sky by benchmarking against stars with well known effective temperatures, bypassing the need for absolute spectrophotometry.
The dust/gas/metallicity scaling relations in the Local Universe
Casasola, Viviana
The mass of the interstellar medium (ISM) is composed of gas for ~99% and primarily of dust for the remaining ~1%. Although the dust constitutes a small percentage of the ISM, understanding its properties is of particular importance for several reasons, including the possibility of using dust as tracer of the chemical evolution of the ISM. Dust is indeed composed by metals, and thus it allows an alternate way to measure metallicity. Metals are produced mainly by the stellar nucleosynthesis and then returned to the ISM, either as gas and as solid grains condensed during the later stages of stellar evolution; they can later be destroyed and incorporated into new generations of stars. This matter cycle (between gas, dust, metals, star formation process) is critical for the study of the formation and evolution of galaxies. I will present the main scaling relations involving molecular, atomic and total gas and dust (and their ratios) as a function of the metallicity for a sample of ~400 nearby, late-type galaxies extracted from the DustPedia sample, a database of almost all resolved nearby galaxies observed by Herschel. Since the DustPedia project is addressing many aspects of the galaxy evolution such as growth of the metal abundance, loss of metals in galactic winds, physical processes in the ISM, studies in the DustPedia context are particularly adapt to characterize metal content with dust.
Calibration Challenges for WFIRST
Casertano, Stefano
Large-scale survey programs represent a significant part of the scientific motivation for the WFIRST mission, the intended NASA successor to the Hubble and Webb observatories. The goals of the large-scale surveys include very high precision and fidelity determination of cosmological parameters, especially the parameters of the dark energy equation of state, as well as the determination of the frequency of exoplanets down to sub-Earth masses. Achieving these goals will require unprecedented precision in the calibration of both photometry and astrometry, as well as other instrumental parameters such as detector effects and the instantaneous Point Spread Function. We present a thorough, quantitative review of the calibration needs for the mission, as well as a comprehensive plan to achieve these goals with a combination of pre-launch characterization, laboratory testing, in-flight data, and external observations.
Astrometric Measurements for the Determination of H0
Casertano, Stefano
TBA
Molecular gas in two companion cluster galaxies at z = 1.2
Castignani, Gianluca
Probing the star formation (SF) history of distant cluster galaxies is essential to evaluate the effect of dense environment in shaping galaxy properties we observe today. We exploit NOEMA interferometer observations to study the molecular gas properties of two companion star-forming galaxies, with a projected angular separation of 6 kpc, and belonging to a galaxy cluster within the Irac Shallow Cluster Survey, at a redshift z=1.2, i.e., ~2 Gyr after the cosmic SF density peak. We describe the first CO detection from 1<z<1.4 star="" forming="" cluster="" galaxies="" with="" no="" reported="" evidence="" of="" agn.="" we="" exploit="" noema="" observations="" at="" ~3mm="" to="" detect="" co(2-1)="" line="" emission="" from="" the="" two="" selected="" galaxies,="" unresolved="" by="" our="" observations.="" based="" on="" spectrum="" estimate="" a="" total="" molecular="" gas="" mass="" m(h2)="2.2e+10Msun," for="" blended="" sources,="" where="" galactic="" co-to-h2="" conversion="" is="" used.="" assuming="" that="" sources="" equally="" contribute="" observe="" analysis="" yields="" sf="" rate="" ~78="" msun="" yr,="" (short)="" depletion="" time="" scale="" ~0.14="" gyr,="" and="" fraction="" ~15%,="" each="" sources.="" also="" provide="" new="" more="" precise="" measurement="" an="" unknown="" weighted="" mean="" redshifts="" z="1.163+/-0.001." results="" are="" in="" overall="" agreement="" those="" other="" distant="" model="" predictions="" main="" sequence="" field="" similar="" redshifts.="" suggest="" late="" assembly="" members,="" via="" infall="" as="" well="" scenario="" close="" their="" interaction.<="" p="">
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Revisiting the Milky Way Satellite Orbits with GAIA Data
Cautun, Marius
TBA
Finally Rapporteur
Celotti, Anna Lisa
.I will try to enlighten the content of the FM3, with emphasis on still open problems.
Fast spectral synthesis for a new generation of solar and stellar brightness variability models
Cernetic, Miha
Recently, realistic three-dimensional (3D) magnetohydrodynamic (MHD) simulations of the solar near-surface magneto-convection achieve excellent agreement with observations. Such calculations pave the way for a new generation of models of solar and stellar brightness variability, which calculate the radiative transfer for a huge set of rays through such 3D MHD cubes. If using the conventional method for the radiative transfer for such a huge amount of rays, it becomes computationally very expensive. This is due to the treatment of the spectral lines: The spectra of the Sun and Sun-like stars contain several millions of molecular and atomic lines that play an important role in the irradiance variability in the UV and visible spectral domains. To achieve faster calculations while taking spectral lines into account, we propose a solution in the form of modified opacity distribution functions (ODFs). Standard ODFs allow taking into account the effect of spectral lines by approximating their complex structure in opacity. We investigate the procedure used for ODF computations and develop a novel approach for fast calculations of a) integrated flux and its variability in passbands of interest, e.g. in Strömgren-, Kepler-, and Plato- filters; b) the total solar irradiance (TSI) and its variability. In particular, we show that it is sufficient to calculate the radiative transfer of just about a hundred frequency points to accurately reproduce the TSI and its variability. Our method and the related speed-up in radiative transfer calculations allows the current models to be taken to a new level.
Plenary Session: Reflections on 100 years of IAU
Cesarsky, Catherine
TBA
Simulations at the Dwarf Scale: From Violent Dwarfs at Cosmic Dawn and Cosmic Noon to Quiet Discs today.
Ceverino, Daniel
Dwarf galaxies with stellar masses around 10^9 Msun can be explored at high and low redshifts and they give a glimpse of the different conditions of galaxies formation at different epochs. Using a large sample of about 300 zoom-in cosmological hydrodynamical simulations of galaxy formation I will briefly describe the formation of dwarfs at this mass scale at 3 different epochs: cosmic dawn (Ceverino, Klessen & Glover 2018), cosmic noon (Ceverino et al. 2015b), and today (Ceverino et al. 2017a). I will describe the FirstLight simulations of first galaxies at redshifts 5-15. These first dwarfs have extremely high star formation efficiencies (SSFR=SFR/Ms = 10-60 Gyr^-1) due to high gas fractions and high gas accretion rates. These simulations will make predictions that will be tested for the first time with the James Webb Space Telescope (JWST). In particular, we look at gas kinematics through rest-frame visible nebular lines at redshifts higher than 6. At cosmic noon (z=2), galaxy formation is still a very violent and dynamic process and the gas kinematics at the dwarf scale is dominated by turbulence. The VELA simulations have generated a set of dispersion-dominated dwarfs that show an elongated morphology due to their prolate dark-matter halos. Between z=1 to z=0, The AGORA simulation shows the formation of a low-mass disc due to slow gas accretion. The disc is initially dynamically hot (high sigma/v) and stable against gravitational instabilities. During several Gyrs, the disc slowly settles down into a low-mass galaxy that agrees with many local scaling relations, such as the stellar-mass-halo-mass and the baryonic Tully-Fisher relation.
New insights on galactic dynamos
Chamandy, Luke
Mean-field turbulent dynamo theory is the leading theory to explain the prevalence of large-scale magnetic fields in spiral galaxies, but its systematic comparison with observations is still incomplete and fragmentary. We demonstrate that a standard $\alpha\Omega$ dynamo produces pitch angles of the large-scale fields of nearby galaxies that are remarkably consistent with available data. This work is a step toward systematic statistical tests of galactic dynamo theory. One limitation, however, is that some of the dynamo model parameters are difficult to constrain directly using observations. Hence, we present detailed estimates for the values of key parameters of supernova-driven interstellar turbulence. Expressions are formulated to relate the turbulent correlation time, outer scale, and root-mean-square turbulent speed to underlying observables or quasi-observables like gas density, supernova-rate density, sound speed, and disk scale height. On the other hand, it seems likely that important physical effects have not yet been discovered or recognized to be important. Particularly intriguing is the possible role of small-scale magnetic fluctuations in the mean-field dynamo mechanism. It is known that when such fluctations exist in the presence of rotation, a new term arises in the mean electromotive force, and we show that this leads to a partial suppression of dynamo action and a reduction of the growth rate in the kinematic regime. Moreover this effect tends to become more important as the mean-field nears saturation because small-scale fluctuations are then enhanced by turbulent tangling of the near-equipartition large-scale field. Thus, one obtains a negative feedback effect that quenches the dynamo and leads to the saturation of the large-scale field. This saturation mechanism is found to be competitive with the well-known dynamical $\alpha$-quenching mechanism for realistic parameter values.
Common envelope evolution and the role of accretion
Chamandy, Luke
Binarity is likely needed to explain the ubiquity of bipolarity observed in planetary nebulae (PNe) and pre-planetary nebulae (pPNe). The central stars of several bipolar PNe have been observed to be close binaries, with the symmetry axis of the PN perpendicular to the orbital plane. Such systems likely experienced a common envelope interaction, wherein the core of the original AGB star and its companion rapidly spiralled in toward one another, and ejected the envelope. This process remains poorly understood, largely because it is inherently 3D, involves a vast range of scales, and is computationally demanding. Simulations have yet to produce a tight binary and ejected envelope when only the binary potential energy is used to propel the envelope, suggesting additional power sources might be necessary. One such source is accretion onto the companion (e.g. a white dwarf or main sequence star). We have performed fully 3D global hydrodynamical simulations of common envelope evolution in high resolution using the AMR code AstroBEAR, and bracket the plausible range of accretion rates from the results of two such simulations---one with a subgrid accretion model based on the Bondi-Hoyle-Lyttleton formalism, and the other without any subgrid accretion. From this exploration we argue that super-Eddington accretion onto the companion may be common. This could power jets which help to unbind and shape the envelope during inspiral.
Very wide stellar binaries as probes of gravity
Chanamé, Julio
Our present standard model of gravity, General Relativity (and Newtonian gravity, in the appropriate limit), has been experimentally tested with success at various scales and regimes, from our daily life to phenomena ranging from the Solar System to double massive black holes that merge and produce gravitational waves. Yet in the limit of very low accelerations, tests have been harder to come up with. This is an unsatisfactory situation, given that the rotation curves of disk galaxies fall precisely within that regime, and application of the standard model leads inevitably to requiring thepresence of dark matter. Even though the case for dark matter is not restricted to the rotation curves of galaxies, still they are arguably one of the most important pieces of evidence for it, and thus all assumptions leading to it must be tested by all means possible. The orbital accelerations experienced by the components of very wide binaries with semimajor axes of a few thousand AUs and larger fall within this special regime of gravity. Not only that, but they do sowithout the ambiguities associated to the potential presence of any dark matter, thus offering us this important and rare opportunity. Wide binaries have been explored for these purposes in the past, but never before with the exquisite astrometric quality that current facilities offer. I will present our latest results, based on Gaia (both TGAS as well as DR2) and state-of-the-art ground-based instrumentation, on what the widest genuine binaries are telling us about the behavior of gravity at the low acceleration regime.
Transitional disk archaeology from exoplanet population synthesis
Chaparro, Germán
Increasingly better observations of resolved protoplanetary disks show a wide range of conditions in which planets can be formed. Many transitional disks show gaps in their radial density structure, which are usually interpreted as signatures of planets. It has also been suggested that observed inhomogeneities in transitional disks are indicative of dust traps which may help the process of planet formation. However, it is yet to be seen if the configuration of fully evolved exoplanetary systems can yield information about the later stages of their primordial disks. We propose to use supervised learning algorithms to probabilistically predict whether the progenitor disk of an exoplanetary system was originally density perturbed. We use synthetic exoplanet population data from Monte Carlo simulations of systems forming under different density perturbation conditions, which are based on current observations of transitional disks. The simulations use a core instability, oligarchic growth, dust trap analytical model that has been benchmarked against exoplanetary populations. We can thus infer some properties of progenitor disks, and probabilities of finding planets in the habitable zone of stars based on general properties of observed exoplanetary systems.
Helio and asteroseismic observational constraints on stellar properties accross the HRD
Chaplin, William
It is an exciting time to be involved in stellar astrophysics. A new generation of space- and ground-based telescopes are providing data of exquisite quality on unprecedented numbers of stars. In this review talk, I will provide a brief overview of how these data are opening up new possibilities for the detailed asteroseismic characterisation and study of stars across the Hertzsprung-Russell Diagram.
Ambiguity, Scope, and Significance: Difficulties in Interpreting Celestial Phenomena in Chinese Records
Chapman, Jesse
This paper examines three factors that contribute to the misinterpretation of records of astronomical and meteorological phenomena in the Chinese historiographical tradition. First, it shows that certain types of records, particularly those describing light, bows, or qi (variously translated as ether, material force, and psychophysical stuff) in fact refer to disparate types of phenomena ranging from oddly-shaped clouds, to halo effects, comets, and aurora. Position words, such as pang (“beside” or “on the side of”) and guan (“encircle” or “penetrate”), are likewise often ambiguous. Second, it describes the range of phenomena and events included in Chinese categories roughly corresponding to astrology and mathematical astronomy, tianwen (celestial patterns) and lüli (calendars and pitchpipes), as well as a third category which includes extensive records of celestial phenomena, wuxing (general omenology, lit. “five phases”). Finally, it turns to the political and religious significance of the practice of observing the sky and modeling the movements of celestial bodies in premodern Chinese records. To avoid miscategorization and misinterpretation, it is necessary to have a working understanding of the problems of ambiguity, scope, and significance.
The Third Realization of the International Celestial Reference Frame
Charlot, Patrick
This talk will review the new realization of the International Celestial Reference Frame, ICRF3, which is presented for adoption by the IAU General Assembly through a resolution. ICRF3 is aimed at replacing the second realization of the International Celestial Reference Frame, ICRF2, in use since 2010. ICRF3 has been generated by a Working Group of the IAU appointed in 2012. It is based on state-of-the-art astronomical and geophysical modeling and takes advantage of the wealth of VLBI data acquired on various observing networks (IVS, VLBA, DSN,…) since 2009 when ICRF2 was built. Compared to ICRF2, ICRF3 represents a significant improvement in terms of source characterization, position accuracy and total number of sources. About twice as many observations have entered ICRF3 compared to ICRF2. ICRF3 comprise source positions at three radio frequencies, 8.4 GHz, 22 GHz and 32 GHz. It is meant to be the reference for aligning the Gaia optical frame onto the International Celestial Reference System with the highest accuracy.
Fast Radio Bursts and Transients
Chatterjee, Shami
Our view of the dynamic radio sky has expanded greatly in recent years, driven by advances in telescope hardware, computation, and data processing techniques. Wider fields of view at higher spatial and temporal resolution have revealed a diverse zoo of transient phenomena, including as-yet enigmatic Fast Radio Bursts (FRBs), which are dispersed millisecond flashes of radio waves originating from beyond the Milky Way. The precise localization of a repeating FRB source has enabled observations over a broad spectral range, revealing intriguing new clues about the central engine, its extreme magneto-ionic environment, and the role of propagation effects. Meanwhile, the detection of gravitational waves from the merger of binary neutron stars and the identification of an electromagnetic counterpart has triggered a pan-chromatic gold rush, and radio observations of the afterglow have produced some of the strongest constraints on the nature of the merger event. Surveys like the ongoing VLA Sky Survey, as well as new telescopes and instrumentation, promise many more surprises to come.
The Dwarf Galaxy Host of a Repeating Fast Radio Burst
Chatterjee, Shami
Fast radio bursts (FRBs) are enigmatic dispersed flashes of radio waves of extragalctic origin. FRB 121102 is the first (and so far, only) source that is known to produce repeat bursts, and the first to be precisely localized to a host galaxy. The host of FRB 121102 is an irregular dwarf galaxy at a redshift z = 0.193, with low metallicity, prominent emission lines, and a star formation rate of about 0.4 solar masses per year - properties comparable to those of extreme emission line galaxies that are also known to host hydrogen-poor superluminous supernovae and long-duration gamma-ray bursts. The burst source is further localized to a bright knot of star formation within the host galaxy, and is coincident with a persistent, variable, unresolved radio source. The high and variable rotation measure of the bursts demonstrates that the burst source is embedded in an extreme magneto-ionic environment, suggestive of the Milky Way galactic center. We do not yet understand whether FRB 121102 is representative of the wider FRB population, or how the host galaxy properties influence its repeating nature and detectability.
The dark side of HMXB
Chaty, Sylvain
High Mass X-ray Binaries (HMXB) have been revealed by a wealth of multi-wavelength observations, from X-ray to optical and infrared domain. We will review here what these observations have brought to light concerning our knowledge of HMXB, and what part of HMXB still remains in the dark side.Intensive programs, including imaging, photometry, low and high resolution spectroscopy, stellar spectra modeling, spectral energy distribution (SED) fitting, timing and interferometry, have shown that properties of HMXB are mainly dictated by the nature of their massive host stars. Imaging and photometry allow us to identify various types of HMXB, low and high resolution spectroscopy, combined to stellar spectra modeling, lead us to derive accurate parameters of the companion star (interstellar absorption, metallicity, rotation, gravity, etc), SED fitting gives us information on intrinsic absorption and characteristics of circumstellar enveloppe, mid-infrared imaging allows us to explore the impact of these active stars on their environment, timing brings us orbital and spin periods, and finally interferometry opens the way to directly imaging the dust cocoon surrounding HMXB…The INTEGRAL satellite has launched the revival of HMXB studies, extending the population of supergiant HMXB (from only 5 in 1986 to 35 today), revealing previously unknown highly obscured and transient HMXB (so-called supergiant Fast X-ray Transients, SFXT). The first detections of gravitational waves has confirmed the interest of studying compact binaries hosting massive stars, the obscured HMXB being the precursors of common enveloppe systems.Many questions are still pending, related to the accretion processes, the wind properties in these massive and active stars, and the overall evolution due to transfer of mass and angular momentum between the companion star and the compact object. We will see how future observations should be able to answer to these questions, which constitute the dark side of HMXB.
Direct imaging
Chauvin, G.
TBA
Cosmic Ultraviolet Baryon Survey
Chen, Hsiao-Wen
I will summarize the scope, scientific objectives, and initial results from the COS Ultraviolet Baryon Survey (CUBS), a new HST Cycle 25 program designed to map `dark' baryonic structures in the crucial but unconstrained epoch between z=0.4 and z~2,
EXPANDING ANGULAR MOMENTUM MEASUREMENTS TO DWARF GALAXIES
Chengalur, Jayaram
We use high-resolution HI observations and broad band photometry to measure the baryonic mass (Mb) and baryonic specific angular momentum (jb) for dwarf irregular galaxies in different environments. We find that for dwarf galaxies jb scales approximately linearly with Mb. This is similar to what is observed for larger bulgeless spirals. We also find that the jb-Mb relation for dwarfs does not have a measurable dependence on the large scale environment, with dwarf galaxies in voids showing similar trends to dwarf galaxies in fields and the outskirts of small groups. However, all dwarf irregular galaxies, regardless of the large scale environment have significantly higher specific angular momentum than expected from the relation obtained for bulgeless spiral galaxies. We combine our data with data from earlier studies and find that this increase in specific angular momentum occurs for dwarf galaxies with masses lower than 109.1 Interestingly, the mass threshold that we find, viz, 109.1 Msun is very similar to the mass threshold below which galaxy discs start to become systematically thicker. The approximately linear trend between jb and Mb that we find in the dwarf galaxies is qualitatively consistent with models in the bulk of the baryonic matter in the disk is in the form of a gas disk which is marginally stable as per the Toomre criteria. In such models feedback from centrally concentrated star formation could preferentially remove the low angular momentum gas from the central parts of dwarfs (and so increase the specific angular momentum of the remaining material) and also inject mechanical energy, leading to thicker discs. We find however, that the observed amount of star formation in our sample galaxies is insufficient to produce the measured increase in the specific angular momentum. It hence appears that some other, as of yet not identified mechanism, plays a role in producing the observed enhancement in specific angular momentum.
CAPjournal Working Group
Cheung, Sze-leung
This talk will report on the work carried out by the Communicating Astronomy with the Public Journal Working Group under Commsion C.C1
Updates from IAU Office for Astronomy Outreach
Cheung, Sze-leung
The IAU Office for Astronomy Outreach (OAO) is a joint venture by the International Astronomical Union (IAU) and the National Astronomical Observatory of Japan (NAOJ). This talk will provide an update to the office work. Recent highlights including the coordination of the network of the IAU National Outreach Contacts (NOCs), publication of CAP Journal, IAU communications, and projects like Astronomy Translation Network.
The asteroseismic revolution on Galactic scales
Chiappini, Cristina
In this review talk I will summarise how can asteroseismology of red giants contribute to the challenging task faced by Galactic Archeology of deciphering the assembly history of the Milky Way. Since the discovery of solar oscillation in red giants made by CoRoT in 2009, the field has evolved fast, and the pathway of how to produce high-resolution chrono-chemo-kinematical maps of the Galaxy seems now clear.It is now accepted that solar-like oscillating giants are excellent evolutionary clocks thanks to the availability of seismic constraints on their mass and to the tight age–initial mass relation they adhere to. Their larger luminosities (in comparison with sub-giants) together with their large age-baseline make of them perfect galactic mappers to larger distances than what will be possible with Gaia plus spectroscopy only.The first steps taken in this direction by combining spectroscopic surveys such as APOGEE, RAVE , and Gaia-ESO with seismic information from Kepler, K2 and CoRoT will be briefly summarised, as well as the current main caveats and difficulties. Key outstanding and still open questions in Galactic Archaeology will be summarised with the purpose to illustrate the need for precise ages for large samples of stars covering large portions of the Galaxy.I will conclude by showing that when these questions are turned into asteroseismic requirements we can show these to be within the capabilities of the current PLATO instrument design, provided the observations are sufficiently long to produce data of sufficient quality to allow for age estimates of distant targets to a 10% precision level. We therefore strongly endorse PLATO’s current design and proposed observational strategy, and conclude that PLATO can be turn into a legacy mission for Galactic archaeology.
Age dating the stars in the Milky Way using astrometry and asteroseismology: messages from the oldest stars
Chiappini, Cristina
Because most stars carry in their outer envelopes the chemical composition inhered at birth, it should be possible to map the star formation history in different parts of the Milky Way by measuring, for stars of different ages, a large array of chemical elements covering different nucleosynthetic sites. This goal seems to be still reachable even in the presence of radial stellar mixing, i.e., the fact that stars can move away from their birth places, loosing most of their kinematical memory. We will illustrate how the combination of detailed multi-dimensional chemical analysis and precise ages can have an great impact on our current understanding of the formation of the MW, and especially of its oldest populations, such as halo, thick disk and bulge.
The Stagger-grid: synthetic spectra and broad-band photometry with 3D model stellar atmospheres across the Hertzsprung-Russell diagram
Chiavassa, Andrea
Stars are not smooth. Their photosphere is covered by a granulation patterns associated with heat transport by convection. These structures have different size, depth, and temporal variations across stars in the Hertzsprung-Russell diagram. Crucially, convection shapes the atmospheric structure and the emergent flux we observe. Our 3D radiative hydrodynamical simulations of stellar convection with the STAGGER code are now able to model these complex phenomena across most of the Hertzsprung-Russell diagram. We present a library of high-resolution stellar synthetic fluxes obtained from these 3D simulations (Chiavassa et al. 2018). Our spectra show small but significant differences with respect to the emergent flux predicted by 1D hydrostatic models: we discuss these effects in terms of synthetic colors, the implication of convective shifts for precise radial velocity measurements, and the broader implication of our models for calibration works.
Las Campanas Stellar Library
Chilingarian, Igor
Stellar libraries are fundamental tools required to understand stellar populations in star clusters and galaxies as well as properties of individual stars. Comprehensive libraries exist in the optical domain, but the near-infrared (NIR) domain stays a couple of decades behind. Here we present the Las Campanas Stellar Library project which is the largest collection of signal-to-noise intermediate-resolution (R=6500) NIR spectra (0.83
Applying astronomy tools in the field of development economics
Chingozha, Tawanda
Astronomy has largely relied on imagery as a source of data. Scientists in this field have deployed a number of big data techniques, for example machine learning, in order to make sense of ‘big’ night sky and radio data sets (among others). This has advanced the understanding of the universe. Ball et all., (2010) for instance, discusses how data mining has enabled the examination of different astronomical problems. This is at a time when astronomers and researchers in other disciplines are seized with the question how astronomy can translate to development. While the general answer is not always straightforward, borrowing astronomy skills and approaches addresses research questions in other disciplines and answers real world questions. Economics is one such discipline. Different space programs have installed earth observation (EO) sensors on satellites, thus enabling economists to rely on EO date to make inferences on economic questions. For example, Sala-i-Martin (2009), Henderson et al., (2012) have used image analysis techniques on Night Lights Data (NLD) to investigate poverty and economic activity respectively. In this paper we illustrate the use of machine learning to create agricultural production data sets from Landsat imagery; with the end goal to estimate the effects of agrarian reform on welfare in developing countries. Astronomy has also relied on citizen science in the identification of new galaxies (a case in point is the Galaxy Zoo project). This paper also discusses the use of citizen science in the examination of changes in urban informality patterns in developing countries.
Disassembling the Square Kilometre Array: Astronomy and Development in South Africa
Chinigo', Davide
The article poses questions about astronomy and its local, national, and global developmental impacts, drawing on ongoing research around the internationally networked Square Kilometre Array (SKA) radio telescope in South Africa. The relationship between progress in global science and technology and societal change has traditionally been framed through western-centric notions of progress imbued with universalism; the field of astronomy exemplifies this approach, with its assumptions of an inherently positive correlation between its science and loosely defined notions of ‘development’. We problematise this assumption through an analysis of the multiple notions of development at different scales of analysis in the SKA. We argue that large astronomy projects such as the SKA are best understood as dense assemblages of science, infrastructure, human agency and politics, in which historically rooted local concerns are marginalized in the name of the national or global public interest.
The signature of AGN feedback on CGM properties
Choi, Ena
Recently, theoretical work has begun to compare the simulated circumgalactic medium (CGM) to column densities and equivalent width measurements as a function of impact parameter from the center of the galaxy. The majority of the simulations underproduce the amount of metal-enriched gas at large impact parameters compared to observations and fail to match the large amount and high covering fraction of OVI measurements tracing the hottest gas phase, as well as less ionized cooler lines such as MgII, CIII and SiIV. However, none of these studies include mechanical AGN feedback, which may play an important role in driving winds and enriching CGM at large distance. To elucidate how the physical conditions and dynamical state of the CGM gas change by AGN feedback, we run a suite of hydrodynamical simulations incorporating a new treatment of AGN feedback which is implemented in a fully self-consistent way, launching high-velocity mass outflow. We post-process these sets of simulations with a synthetic spectrum generation code and compare covering fractions, equivalent widths, ion ratios, and kinematics to observations as a function of impact parameter and specific star formation rate. We show that the AGN feedback effectively enrich CGM ‘inside-out’ by spreading centrally enriched metals to the outskirts of galaxies along the AGN-driven outflow, as well as ‘outside-in’, where winds propagate further from galaxies at earlier epochs of high AGN activity and then ejected metals recollect into the CGM at later times.
Spin evolution of Horizon-AGN early-type galaxies
Choi, Hoseung
The differential rotational properties of early-type galaxies (ETGs) revealed by integral field spectroscopy surveys is arguably one of the most exciting findings in the galaxy evolution study during the past decade. Numerical studies have shown that galaxy mergers under various configurations can reproduce the observed distribution of ETG spin. However, we suggest an alternative scenario for the spin evolution of a large fraction of ETGs. Using the Horizon-AGN simulation, we follow the spin evolution of 10,037 color-selected ETGs more massive than 1010 solar mass that are divided into four groups: cluster centrals (3%), cluster satellites (33%), group centrals(5%), and field ETGs (59%). We find a strong mass dependence of the slow rotator fraction, fSR, and the mean spin of massive ETGs. Although the environmental dependence is not clear in the fSR, it is visible in the mean value of the spin parameter. The environmental dependence is driven by the satellite ETGs whose spin gradually decreases as their environment becomes denser. Galaxy mergers appear to be the main cause of total spin changes in 94% of central ETGs of halos with Mvir > 1012.5 solar mass, but only 22% of satellite and field ETGs. We find that non-merger induced tidal perturbations better correlate with the galaxy spin-down in satellite ETGs than mergers. Given that the majority of ETGs are not central in dense environments, we conclude that non-merger tidal perturbation effects played a key role in the spin evolution of ETGs observed in the local (z < 1) universe.
Metallicity gradients in absorption-selected intermediate-redshift galaxies
Christensen, Lise
Strong absorption lines in quasar spectra arise when the lines of sight to distant quasars intersect intervening galaxies. Associated metal absorption lines from the strongest hydrogen absorption lines, the damped Lyman alpha absorbers (DLAs), allow us to trace accurate metallicities of galaxies back to redshifts z>5. This has revealedmetallicities typically around 0.1-100% solar values with a gradual increase in metallicity with increasing cosmic time as expected when DLAs get enriched from star-formation processes. DLAs have metallicity distributions roughly similar to that of Milky Way halo stars, but with a large spread in the range of metallicities.In order to understand the connection between the DLAs and the host galaxies and how the metallicities vary with radial distances, we first need to detect the host galaxy in emission. This search has evolved rapidly in past decade, and we now have a sufficiently large sample of more than a dozen absorber-galaxy pairs out to redshifts z>2, where we can compare metallicities in emission and absorption.I will present resent results and explain how we have determined metallicity gradients in circumgalactic environment of the galaxies out to ~40 kpc at intermediate to high redshifts. In addition to deriving gradients, these values allow us to reproduce observed galaxy scaling relations, such as the mass-metallicity relation, observed in conventional luminosity-selected galaxy samples. This suggests that the origin of metallicity gradients seen in local disk galaxies arise at higher redshifts, and can be probed by absorption line spectroscopy.
Can We Recovering Our Sensitivity to Earth-Like Planets Around Sun-Like Stars? Extending the Kepler Baseline with PLATO
Christiansen, Jessie
Although the Kepler mission was designed to measure the occurrence rate of Earth-twins, a confluence of factors resulted in a data set that fell just short of the required sensitivity. There are several dozen habitable-zone, Earth-size candidates that are just above the significance threshold, and more which are just below. Here we investigate the possibility of improving our detections of these candidates with the addition of data from the ESA PLATO mission. PLATO is planning to re-observe the Kepler field during one of its two long stare surveys.
The Martian Trojans and the nearest asteroid family to the Sun
Christou, Apostolos
The Main Asteroid Belt (MB) is replete with families formed by collisions over the lifetime of the solar system. Interior to the MB and at the edge of the terrestrial planet region lie the Martian Trojans, which have likely survived there for ~4 Gyr. Among the ten known Trojans with 16<h<20 exists="" a="" tight="" orbital="" grouping="" composed="" of="" 8="" members,="" which="" the="" largest="" is="" 2-km="" asteroid,="" (5261)="" eureka="" (christou,="" icarus,="" 2013).="" this="" group="" was="" recently="" found="" to="" share="" common,="" olivine-rich="" composition="" (borisov="" et="" al,="" mnras,="" 2017)="" and="" may="" represent="" material="" excavated="" from="" martian="" mantle="" (polishook="" nat.="" astron.,="" 2017).="" “eureka="" family”="" probably="" formed="" not="" by="" collisions,="" like="" most="" asteroid="" families,="" but="" rotational="" spinup="" \&="" fission="" (christou="" 2017;="" polishook="" it="" has,="" therefore,="" more="" in="" common="" with="" so-called="" pairs="" small="" clusters="" similar="" way="" mb="" (pravec="" nature,="" 2010;="" pravec="" there="" is,="" however,="" an="" important="" difference:="" family="" likely="" ~100="" times="" older="" (cuk="" 2015)="" -="" unlike="" where="" identification="" among="" background="" unrelated="" asteroids="" possible="" beyond="" ~107="" yr="" effectively="" empty="" trojan="" clouds="" allow="" identify="" gyr-old="" grouping.="" this,="" proximity="" sun="" and ="" absence="" planetary="" close="" encounters="" make="" these="" bodies="" natural="" laboratory="" for="" studying="" long-term="" consequences="" yarkovsky="" &="" yorp="" effects="" implications="" range="" topics:="" calibrating="" models,="" existence="" primordial="" earth="" trojans="" evolution="" systems="" around="" other="" stars.="" during="" presentation="" i="" will="" review="" recent="" findings="" on="" mars="" family,="" currently="" open="" problems="" what="" we="" stand="" learn="" when="" facilities="" such="" as="" large="" synoptic="" survey="" telescope="" come="" online="" near="" future.<="" p="">
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Local merger rates of double neutron star systems
Chruslinska, Martyna
The first ever detection of gravitational waves from a merging double neutron star (DNS) binarywas registered on August 17, 2017. This amazing, yet unexpected discovery challenged our understanding of evolution of its potential progenitor systems, implying a much higher rate of DNS coalescences in the local Universe than predicted on theoretical grounds.In light of this detection, we revisited the topic of DNS formation in the classical isolated binary evolution scenario. We employed population synthesis method, aiming to pinpoint the factors that affect the predicted merger rates the most. Apart from being particularly sensitive to the common envelope treatment, DNS merger rates appear rather robust against variations of several of the key factors probed in our study (e.g. conservativeness of the mass transfer, angular momentum loss, and natal kicks).Binaries that merge within the local Universe originate from progenitor systems that formed at different redshifts and in various environments. It appears that the efficiency of formation of double compact objects is highly sensitive to metallicity at which star formation proceeds. Therefore, to confront the theoretical predictions with observational limits resulting from gravitational waves observations one has to account for the formation and evolution of progenitor stars in chemically evolving Universe. In particular, this requires knowledge of the amount of star formation taking place at different metallicities and at different redshifts. This introduces another layer of uncertainties to such considerations, besides the factors relating directly to binary evolution. We combine the available observational relations connecting metallicity, star formation and stellar masses of galaxies to quantify those uncertainties.
Jorge Sahade, First Latin American IAU President
cidale, lydia
Prof. Jorge Sahade (1915-2012) was elected as the first Latin American President of the International Astronomical Union (1985-1988). From then on he had a very active participation as president, vice-president, and organizing committee member of several Commissions and Divissions of the IAU, related to stellar astrophysics and exchange of astronomers.Prof. J. Sahade was born in Argentina and was one of the first students graduated in astronomy at the National University of La Plata, Argentina. He served as director of the Astronomical Observatory of Córdoba (1953-1955) and of the Observatory of La Plata (1968-1969). He was the first dean of the Faculty of Exact Sciences of the National University of La Plata. He promoted the purchase of a 2.15 m diameter telescope, today located in the Complejo Astronómico El Leoncito. He founded the Institute of Astronomy and Physics of Space (IAFE) in Buenos Aires and was also the first director (1971-1974) of this institution. He was also director of the “Comisión de Actividades Espaciales” (Argentinian Space Agency) and promoted the inclusion of Argentina as a partnership of the Gemini Observatory. Prof. Sahade also focused on the development of the astonomy in Latin American and led to the creation of the Liga Latinoamericana de Astronomía (nowadays LIADA).His passion was astronomy. His research field was interacting binary systems and he published about 200 papers, among them is the well-known discovery of the “Struve-Sahade effect”.I knew him when he was 70 years old as a very enthusiastic astronomer, travelling everywhere to promote the astronomy in Latin American (Argentina, Perú, México, Honduras). Among his last dreams were the creation of a Latin American Institute to bring about the development and enhancement of the astrophysics in South and Central America, the revival of the UV astronomy and many more impressive works that he would have liked to end and publish.
Hydrodynamics and Thermodynamics of Embedded Planets’ First Atmospheres
Cimerman, Nicolas
Context:_x000D_ In the core accretion paradigm of planet formation, gas giants form a massive atmosphere in a run-away gas accretion phase once their progenitors exceed a threshold mass: the critical core mass. On the one hand, the majority of observed exo-planets, being smaller and rock/ice-dominated, never crossed this line. On the other hand, these exo-planets have accreted substantial amounts of gas from the circumstellar disk during their embedded formation epoch. _x000D_ Methods:_x000D_ We investigate the hydrodynamical and thermodynamical properties of proto-planetary atmospheres by direct numerical modeling of their formation epoch. Our studies cover one-dimensional (1D) spherically symmetric, two-dimensional (2D) axially symmetric, and three-dimensional (3D) hydrodynamical simulations with and without radiation transport. We check the feasibility of different numerical grid geometries (Cartesian vs. spherical), perform convergence studies, and scan the physical parameter space with respect to planet mass and optical depth of the surrounding._x000D_ Results:_x000D_ In terms of hydrodynamic evolution, no clear boundary demarcates bound atmospheric gas from disk material in a 3D scenario in contrast to 1D and 2D computations. The atmospheres denote open systems where gas enters and leaves the Bondi sphere in both directions._x000D_ In terms of thermodynamics, we compare the gravitational contraction of the forming atmospheres with its radiative cooling and advection of thermal energy, as well as the interplay of these processes. The coaction of radiative cooling of atmospheric gas and advection of atmospheric-disk gas prevents the proto-planets to undergo run-away gas accretion. Hence, this scenario provides a natural explanation for the preponderance of super-Earth like planets.
Progress status of ELT
Cirasuolo, M.
TBA
Herschel-Planck Clusters - Protoclusters in the far-IR
Clements, David
Cross identification of Planck compact sources with Herschel data from the HerMES and H-ATLAS large area surveys has identified a class of objects that appear to be z~2 clusters or protoclusters of galaxies, many of whose members are rapidly forming stars in what appear to be near-simultaneous starbursts. We describe the selection of these sources, discuss their properties as revealed by Herschel and followup observations, compare them to other high redshift cluster/protocluster selections and to theoretical models. These clusters/protoclusters can solve a number of outstanding questions regarding galaxy cluster evolution, but raise other questions about the origin of these objects in the context of currently favoured models of galaxy formation and cosmology. Prospects for further advancing our understanding of these systems are also discussed.
“Coordination of Synoptic Observations of the Sun” WG Chairs’ Report
Clette, Frederic
Business Meeting of Div.E and its Commissions, WGs
Revisiting the historical sunspot number back to 1610: latest progresses
Clette, Frédéric
Due to its unique 400-year duration, the sunspot number is a central reference for understanding the long-term evolution of solar activity and its influence on the Earth environment and climate. Following a 4-year effort, a first end-to-end re-calibrated series of the sunspot number (SN) series was released in 2015. It reduced the main inconsistencies between the SN series and its closest counterpart, the sunspot group number (GN). As it also showed that further improvements are possible, this revision led to the publication of several new alternate reconstructions of either the SN and GN series, leading to some confusion among scientific users. We will first review the main results, which rest either on new improved databases of historical sunspot observations, or on alternate statistical approaches like the active-day method, non-parametric cross-matrices between pairs of observers, expectation minimization, etc. _x000D_ Over recent months, coordinated investigations in the framework of ISSI Team Meetings allowed to identify some flaws or limitations in the applicability of those recent methods and to envision the combined application of multiple approaches. This coordinated work also aims at a better determination of uncertainties in the reconstructed series by each method, where error bars were totally absent in the orignal sunspot numbers. We report on those ongoing progresses. The current international synergy for the preparation of SN version 3, can actually become the fundation of a continuous quality assurance and of a community-wide sanctioning of future updates. We propose such a permanent version-development and supervision scheme under the official IAU framework. With its origins rooted in the 17th century, the sunspot number is thus called upon to become a modern astronomical standard for the 21st century.
S-CUBE & RXTE X-ray surveys of the Small Magellanic Cloud
Coe, Malcolm
The Small Magellanic Cloud hosts the highest density known of Be/X-ray binary systems – over 100 objects. Long term studies of the SMC with RXTE for over a decade, now superseded by the weekly Swift/XRT monitoring (the S-CUBE project), present us with an opportunity to take an overview of these systems and explore some basic parameters. In particular we can gain an excellent insight into the duty cycles of these systems, the long-term pulse period changes, and the range of X-ray luminosities exhibited. From these observations we can infer some basic astrophysical parameters of the systems such as the limits to accretion and the magnetic field distribution of the neutron star components. This talk will review what we are learning about this class of objects from this long-term perspective.
Local Group Dwarf Galaxies
Cole, Andrew
Local Group dwarf galaxies are a unique astrophysical laboratory because they are the only objects in which we can reliably and precisely characterize the star formation histories of low-mass galaxies going back to the epoch of reionization. There are of order 100 known galaxies less massive than the Small Magellanic Cloud within ~1 Megaparsec of the Milky Way, with a vide variety of star formation history, gas content, and mass to light ratios. In this overview the current understanding of the formation and evolution of low-mass galaxies across cosmic time will be presented, and the possibility of drawing links between the properties of individual systems and the broader Local Group and cosmological context will be discussed. Local Group dwarfs will remain a uniquely powerful testbed to constrain the properties of dark matter and to evaluate the performance of simulations for the foreseeable future.
Emerging angular momentum physics from kinematic surveys
Colless, Matthew
I will review the insights emerging from recent kinematic surveys of galaxies, with particular reference to the SAMI survey on the Anglo-Australian Telescope. These new observations provide a more comprehensive picture of the angular momentum properties of galaxies over wide ranges in mass, morphology and environment. I will focus on the distribution of angular momentum within galaxies of various types and the relationship between mass, morphology and specific angular momentum. I will discuss the implications of the new results for models of galaxy assembly.
Key early science programs with MANIFEST on GMT
Colless, Matthew
The MANIFEST fibre system provides a highly versatile feed for the GMACS and G-CLEF first-light spectrographs on the Giant Magellan Telescope (GMT). Combining these low- and high-resolution optical spectrographs with the wide field of view (up to 20 arcmin), high multiplex, and integral field capabilities provided by MANIFEST enables science programs that are not achievable with other extremely large telescopes. For galactic archaeology and near-field cosmology studies of Local Group galaxies, MANIFEST and G-CLEF can obtain up to 40 simultaneous high-resolution optical spectra over a wide field, and so produce detailed kinematic and chemical maps of the stellar populations out to large radius in galaxies covering a broad range of masses and morphologies. For galaxy evolution studies, MANIFEST and GMACS can combine a survey of galaxies at the epoch of peak star formation with a study of the flows of gas between galaxies and the circumgalactic medium, mapping both the emission from hot gas using integral field spectroscopy and the absorption from cold gas with multi-object spectroscopy of background sources. These programs will feature strongly in the early science goals for GMT.
Nitrogen isotopic ratio across the Galaxy
Colzi, Laura
The abundance ratio 14N/15N is considered a good indicator of stellar nucleosynthesis since the two elemental isotopes are not originated in the same way. Both isotopes have indeed an important secondary production in the CNO cycles. There is the cold CNO cycle that takes place in main-sequence stars and in the H-burning shells of red giants: 14N is created from 13C or 17O and brought in stellar surfaces through dredge-up on the red giant branch. Furthermore, there is the hot CNO cycle, that occurs instead in novae outbursts and is the main way to produce 15N. However, there is also a strong primary component of 14N created in the so-called Hot Bottom Burning (HBB) of asymptotic giant branch (AGB) stars (e.g. Schmitt & Ness 2002), and an (over-)production of 15N with respect to 14N in the relative role played by massive stars and novae (Romano et al. 2003, 2017). Therefore, 15N is principally a secondary element. These different origins lead to an increase of 14N/15N ratio with the Galactocentric distance, up to 8 kpc, as predicted by models of Galactic chemical evolution (GCE, e.g. Romano et al. 2017). However, the relative importance of these processes is still unclear. The only way to test these theoretical predictions is to provide more observational constraints. We report the measurements of the 14N/15N ratio derived in a sample of 87 dense cores that span Galactocentric distances in the range 2–12 kpc, and we present a new Galactocentric behavior of 14N/15N. This is the first time that such a statistically robust sample has been used to study the Nitrogen isotopic ratio across the Galaxy. We are also able to compare this trend with GCE models, and we found some correlations between observations and models (Colzi et al., MNRAS submitted). Moreover, we have also found a new local 14N/15N interstellar medium (ISM) value of about 400, i.e. closer to the PSN (Proto-Solar Nebula) value (about 441, Marty et al. 2010) with respect to past derived value.
Semi-Analytic Model Predictions of the Galaxy Population in Proto-clusters
Contini, Emanuele
We investigate the galaxy population in simulated proto-cluster regions using a semi-analytic model of galaxy formation, coupled to merger trees extracted from N-body simulations. We select the most massive clusters at redshift z=0 from our set of simulations, and follow their main progenitors back in time. The analysis shows that proto-cluster regions are dominated by central galaxies and their number decreases with time as many become satellites, clustering around the central object. In agreement with observations, we find an increasing velocity dispersion with cosmic time, the increase being faster for satellites. The analysis shows that proto-clusters are very extended regions, >20 Mpc at z>1. The fraction of galaxies in proto-cluster regions that are not progenitor of cluster galaxies varies with redshift, stellar mass and area considered. It is about 20-30 per cent for galaxies with stellar mass ~ 10^9 M_sun, while negligible for the most massive galaxies considered. Nevertheless, these objects have properties similar to those of progenitors. We investigate the building-up of the passive-sequence in clusters, and find that their progenitors are on average always active at any redshift of interest of proto-clusters. The main mechanism which quenches their star formation is the removal of the hot gas reservoir at the time of accretion. The later galaxies are accreted (become satellite), and the more the cold gas available, the longer the time spent as active. Central galaxies are active over all redshift range considered, although a non-negligible fraction of them become passive at redshift z<1, due to strong feedback from Active Galactic Nuclei.
Radio Astronomy for Development: Big Data
Cooper, Sally
With the advent of the SKA, radio astronomy has become a key driver for the development of big data analytics, data handling and the provision of large-scale compute facilities as part of the wider scientific computing ecosystem. Furthermore, it has become viewed as a key training ground for the provision of highly skilled data scientists to industry. In this presentation I will describe two closely linked programs, DARA (Development in Africa through Radio Astronomy) Big Data & RADA (Radio Astronomy for Development in the Americas) Big Data, which are currently running in Southern Africa and Colombia. These programs use radio astronomy as a driver for the development of expertise in big data tools, applications and systems, as well as the translation of this expertise to other data intensive fields: food security / sustainable agriculture and health care, which are of particular importance in developing countries. I will discuss the programs themselves, as well as the economic drivers for governments to support the networks and the anticipated outcomes. Both programs are currently part of the UK Newton Fund which uses science and innovation partnerships to promote economic development and social welfare in partner countries.
Physical properties of ub-mm galaxy proto-clusters at peak epoch of galaxy and cluster formation
Cooray, Asantha
During this talk for the mini-symposium "Build of galaxy clusters" I will present my group's work on sub-mm galaxy proto-clusters, including spectroscopic and imaging observations with Keck, Spitzer, and Hubble. These include measurements of stellar masses, halo masses, gas content, AGN activity, and other properties of proto-clusters identified with Herschel maps, including lensed Herschel sources, at z=2-4.
The Spectral Classification of Stars over the last 200, 100, 75 years, and in the future
Corbally, Christopher
This year 2018 has great historical and current significance for stellar spectral classification. Two hundred years ago in Reggio Emilia, Italy, was born Angelo Secchi, a pioneer of observing and classifying the spectra of stars. At the beginning of the IAU, almost a hundred years ago, one of its original Commissions was titled, the Spectral Classification of Stars, from which was generated Commission 45, Spectral Classification and Multi-band Colour Indices. And seventy-five years ago, was published the “system-changing” MKK, An Atlas of Stellar Spectra. Through this historical view we shall recall how spectral classification, supported internationally by the IAU, continually updated its techniques, while remaining anchored to standards. This has ensured that the MK classification process stays very relevant to the initial characterizing of stars in the 21st century era of large spectral surveys.
The interstellar medium of M33
Corbelli, Edvige
Recent high resolution surveys of the gas cantent of M33 and of its star forming regions, allow a detailed view and analysis of the interstellar gas distribution across the whole disk of the nearest blue spiral galaxy. I will show some results of analysis of the interplay between gravity and turbulence on the processes that locally lead to or are triggered by the formation of stars, starting from the atomic phase down to the molecular gas prior to cloud dispersal.The disk of M33 is not uniform, as will be briefly outlined, and its interstellar medium reflects the variety of dynamical, chemical and thermal processes that may contribute to its evolution. The timescales of local star formation episodes and the duration of the giant molecular cloud lifecycle, however, do not vary much and they are well established thanks to infrared selected Young Stellar Cluster surveys in this galaxy.On larger scales, gas and stellar gravity affect the formation of gaseous arms and filaments in flocculent galaxies. Recent numerical simulations of the M33 disk underline this and the role of gas dissipation and turbulence on the growth of low density interarm holes and on the fragmentation of dense filaments. Hence, the ISM has a fundamenthal role in linking the disk dynamics of isolated young galaxies to individual star forming sites. If gas replenishment from the intergalactic medium is taking place, as is likely for M33, then this might affects the efficiency of the gas to star conversion down to very small scales, although the details of how this happens are not clear yet.
Long-term Properties of Superorbital Periodic Modulation in Wind-Accretion High-Mass X-ray Binaries
Corbet, Robin
Superorbital modulation of X-ray flux has been detected in several high-mass X-ray binaries where accretion takes place from the primary star's wind. Unlike those HMXBs where accretion is driven by Roche-lobe overflow such as LMC X-4, the driving mechanism for superorbital modulation in wind-accretion systems remains elusive, although several models have been proposed. Here, we systematically investigate the long-term properties of superorbital modulation in 2S 0114+650, IGR J16418-4532, IGR J16479-4514, IGR J16493-4348, and 4U 1909+07 using over thirteen years of data from the Swift Burst Alert Telescope. We examine long-term period stability and changes in modulation profile and phasing, and compare these with predictions of the various proposedmodels.
Dynamics of multi-planet systems and the importance of astrometric measurements
Correia, Alexandre
Dynamical studies are very important to fully understand and characterise multi-planetary systems. However, the complete architecture of these systems can only be obtained through astrometric measurements. In particular, the classification of the orbital types and the determination of the habitable zones rely on an accurate determination of the mutual inclinations. In this talk, we will revisit the main limitations of traditional detection techniques, and illustrate the importance of astrometry with some real examples.
Galileo's account of Kepler's supernova (SN1604): a Copernican assessment
Cosci, Matteo
The supernova that appeared in the constellation of Ophiuchus on the 9th of October 1604 is known today as "Kepler's supernova" because of the long and detailed study that the German astronomer devoted to the understanding of the exceptional event (De Stella Nova, Prague 1606). However, at that time Kepler was not the only astronomer whose eyes were turned to the scientific study of that unexpected astronomical event. A few years before than the telescope was invented, also Galileo Galilei was involved in the debate regarding the nature, appearance, position, distance, and overall meaning of the "anomalous" phenomenon. Although he did not publish anything specific on the subject, it is possible to reconstruct his take on the supernova from scattered sources, whose temporal extension start from the first weeks after the stellar outburst and last up to the final years of life of the Pisan astronomer. Therefore it can be affirmed that actually Galileo never stopped his survey on the stella nova. In fact, he lectured on it, took fragmentary notes, drew some diagrams, kept a scientific correspondence, inserted dedicated sections within his major works, commented on the margins of the pages of his copies of his competitors' books and replied under pseudonyms to many of his critics. The present contribution aims at solving the puzzle of Galileo's account on Kepler's supernova, arranging all the extant pieces of evidence in their right chronological order. Galileo's sources will be set in context and the network of his informers will be tracked in order to frame in a comprehensive way one of the most original and influential understanding of the SN1604 of that time. In conclusion it will be evident how Galileo intended to use his set of data for an early, albeit unsuccessful, confirmation of the Copernican model of the solar system (cf. J.L Heilbron, Galileo, Oxford 2010, pp.119-126), almost managing to make the star known as the "Galileo's Supernova".
Asteroid Fragmentation as revealed by Families
Cotto-Figueroa, Desiree
Determining the strengths of asteroidal materials and understanding how those strengths will scale with size is important for constraining the internal structure of the parent bodies of asteroid families. Modeling studies of asteroid disruption and fragmentation use strength and fracture properties derived from experiments using analog materials such as basalt, even though these are unlikely to be representative of asteroid materials. Meteorites, which derive from asteroids, provide a unique opportunity to study the fundamental physical and mechanical properties of asteroidal materials. But to date, few direct studies of physical properties have been conducted on these materials. Given the paucity of relevant strength data, the scale-varying strength properties of meteoritic and asteroidal materials are poorly constrained. Here, we present the first scale-dependent measurements of meteorite strength. Our goal is to span the spatial scale of the mechanical and physical properties of meteorites, and to amass a comprehensive dataset that enables realistic simulations of asteroid fragmentation.
Failed Supernovae and Fallback Accretion
Coughlin, Eric
A failed supernova, which occurs when the core of a massive star collapses but does not produce a successful supernova, still radiates a prodigious amount of neutrinos during the de-leptonization of the iron core. These neutrinos carry with them a few tenths of a Solar mass of mass-energy, and this mass loss produces a weak shock in the outer layers of the star. I will discuss the formation and evolution of this shock, and I will demonstrate that its passage through the stellar material generates a mild explosion with a range of binding energies. I will describe a model for the dynamical evolution of the low-binding energy ejecta, and I will show that its fallback onto the black hole can power super-Eddington accretion for months to years following the initial failure of the supernova. The implications of this long-lived phase of hyperaccretion will be discussed in the context of ultra-long gamma-ray bursts and jetted tidal disruption events.
LSST's Prototype Collimated Beam Projector
Coughlin, Michael
One of the main components of the LSST's calibration hardware system is a ``collimated beam projector,'' which is designed to measure a telescope's instrumental response function versus wavelength. This response function, along with atmospheric transmission, are the key components of photometric calibration. The collimated beam projector projects monochromatic light, monitored with a NIST-calibrated photodiode, through a mask and a collimating optic onto the telescope. In this presentation, we describe results from this prototype system at the CTIO 0.9 meter telescope. We discuss the measurement of the telescope's instrumental response function, including the optical system and camera, to 5% precision. As a cross-check of our system's accuracy, we compare the measurements of the filters to nominal values from the vendor.
Exploration of icy moons as habitats
Coustenis, Athena
When looking for habitable conditions in the solar system, recent studies focus on the natural satellites of gas giants. Indeed, liquid water may be present underneath the surfaces of the natural satellites around Jupiter and Saturn [1]. And several of these satellites show in addition evidence for harboring organic chemistry in their atmospheres or exospheres, as well as energy sources. Measurements from the ground but also by the Voyager, Galileo and the Cassini spacecraft revealed the potential of these satellites in this context, and our understanding of habitability in the solar system and beyond can be greatly enhanced by investigating several of these bodies.Indeed, several of the moons show promising conditions for habitability and the development and/or maintenance of life. Europa, Callisto and Ganymede are hiding, under their icy crust, undersurface liquid water oceans which, in the case of Europa, may be in direct contact with a silicate mantle floor and kept warm by tidally generated heat.Titan and Enceladus, Saturn’s satellites, were found by the Cassini-Huygens mission to possess active organic chemistry with seasonal variations, unique geological features and possibly internal liquid water oceans. As revealed by Cassini, the liquid hydrocarbon lakes currently distributed mainly at polar latitudes on Titan are ideal isolated environments to look for biomarkers.The simultaneous presence of water, geodynamic interactions, chemical energy sources and a diversity of key chemical elements on some of these satellites as on Earth, may fulfil the basic conditions for habitability. These would be investigated with future space missions.Such potential habitats can only be investigated with appropriate designed space missions, like ESA’s L1 JUICE and NASA’s Europa Clipper mission.[1] Coustenis and Encrenaz, 2013, In “Life Beyond Earth”, CUP
Using MHD simulations of the solar atmosphere to reproduce irradiance variations: challenges and recent progresses
Criscuoli, Serena
Several irradiance reconstruction techniques rely on the use of static, one-dimensional, semi-empirical atmosphere models. These models do not capture the high dynamical and fine spatial structuring of the solar atmosphere. Moreover, they are derived from measurements of the solar spectrum that they aim to reproduce. Magneto Hydrodynamic (MHD) simulations of the solar atmosphere are known to better reproduce observed properties of the Sun, so that their use in modeling irradiance variations seems a natural evolution of the current techniques. Nevertheless, the development of such new techniques have been for long hampered by several factors. In this contribution I will review the main problems related to the use of MHD simulations in reproducing irradiance variations, and the recent efforts undertaken by the scientific community to overcome them. I will in particular describe recent development in simulating the higher layers of the solar atmosphere (where most of the observed irradiance variability originates) and the challenges imposed by numerical radiative transfer, in both LTE and NLTE treatment.
The Composition of Barium stars and the s-Process in AGB Stars
Cseh, Borbála
Barium stars belong to a binary system where the companion star has evolved through the AGB phase and transferred elements heavier than Fe produced by the slow neutron-capture process onto the secondary star, which is now observed. A new large set of homogeneous high resolution spectra of Barium stars makes it now possible to meaningfully compare the observational data with different AGB models. We performed a new detailed error analysis of these observations and demonstrate for the first time that the data shows a clear increase of the hs-type/ls-type element ratio (for example, Ce/Y) with decreasing the metallicity, as predicted by non-rotating AGB models where 13C is the main neutron source. We conclude that rotational mixing is a minor effect. Rotating cores on the AGB slower than expected if the angular momentum is conserved may derive from coupling between the core and the envelope. The existence of such coupling has also been invoked to explain the low rotational velocities of the cores of red giant stars and of white dwarfs (the ancestors and the progeny of AGB stars, respectively) inferred via asteroseismology from Kepler observations.
DAEPO WG Report for C1 Business Meeting
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
HUBS: Hot Universe Baryon Surveyor
Cui, Wei
HUBS is being conceptualized in China as a major X-ray mission for the next decade. It is designed to be highly focused scientifically, with the primary driver being to look for "missing baryons", the bulk of which are hypothesized to exist in the low-density, hot gas that lies in intergalactic and circumgalactic space. The gas is thus expected to produce weak emission in soft X-rays, which is technically difficult to detect. On the other hand, the spectrum of the emission would be rich in spectral lines, so it may be quite effective to detect the gas in selected emission or absorption lines. An instrument combining a high spectral resolution, large effective area and large field of view would be required for such a purpose. HUBS will couple a TES-based X-ray imaging spectrometer to a focusing X-ray optical system to satisfy these requirements. Various observational strategies will be employed to significantly enhance its scientific output. A preliminary design of HUBS will be presented.
The role of automated methods for filament finding in understanding the complex relationship between filaments, magnetic fields and star formtion
Cunningham, Maria
The discovery of the ubiquity of filaments in the interstellar medium in the last two decades has begged the question: "What role do filaments play in star formation?"Here we describe how our automated filament finding algorithms are combined with both magnetic field measurements, and high-resolution observations of dense cores in these filaments to provide a statistically large sample to investigate the effect of filaments on star formation.We find that filaments are likely actively accreting mass from the interstellar medium, explaining why some 60% of stars, and all massive stars form "on-filament".
The Klever Survey: spatially resolved metallicity maps and gradients in high redshift galaxies
Curti, Mirko
We will present the first results from KLEVER, an ESO Large Programme aimed at investigating dynamics, gas excitation properties and chemical abundances in high redshift galaxies, by means of near-IR spatially resolved spectroscopy. Exploiting KMOS multi-IFU observations in the J,H and K bands we aim to map multiple optical rest-frame nebular diagnostics (from [O II]3727 to [S III]9530) in a sample of ~150 galaxies between 1.2 < z < 2.5, allowing a full, detailed characterisation of the properties and excitation mechanism of the ISM in these objects on a spatially resolved basis. Here we discuss the results of the analysis of the first available observations, mostly targeting lensed galaxies in CLASH and Frontier Fields clusters.Thanks to the broad set of emission lines provided by the survey, we infer the chemical abundances in our sample exploiting a variety of different diagnostics and compare the predictions from different calibrations. We derive spatially resolved, source-plane metallicity maps and extract radial gradients to assess shape, correlation with different galaxy properties and evolution with cosmic time.The bulk of the galaxies analysed so far are characterized by azimuthally averaged radial metallicity gradients fully consistent with being flat; this may support a scenario in which efficient mixing processes, that redistribute a significant amount of gas over large scales, are in place at these epochs.However, the presence of irregular and asymmetric patterns, as seen in many of the full 2D metallicity maps, warns against the use of radial gradients as the only observable to constrain galaxy evolution models and simulations. A new, physically and statistically meaningful approach to extract information from the metallicity maps beyond the radial averages is explored, tested on KLEVER data and discussed also in light of forthcoming facilities (e.g. JWST).
What Young Massive Clusters in the Magellanic Clouds teach us about Old Galactic Globular Clusters?
D'Antona, Francesca
Recent work on the Young Massive Clusters (YMC) of the Magellanic Clouds (MCs) has shown that rapid rotation, together with its slow down due to the evolution, plays an important role in shaping the color magnitude diagram features, and in particular the presence of an extended turnoff region and of a "split" main sequence, whose bluer side is populated by slowly rotating stars, and the redder side is populated by initially rapidly rotating stars. Thus the phenomenon of multiple populations in these young (age < 400Myr) clusters seems to be unrelated to the features of multiple populations in old Galactic Globular Clusters. In this talk, we remind that the Asymptotic Giant Branch (AGB) scenario explains these latter multiple populations by different episodes of star formation occurring from gas contaminated by the ejecta of massive AGBs and super-AGBs of a first stellar population. These AGBs are then stars as massive as 4-8Msun, those which today populate the MCs YMC. Consequently, we must pose the question whether the evolution of such massive AGBs has been influenced by rotation, how much this affects the yields, and whether the resulting abundances are compatible with the chemical patterns observed and with color magnitude properties such as the morphology of the horizontal branch. We show the first promising results of this analysis.
AO assisted NIR spectroscopy: from old AGB stars to young sub-stellar objects
D’Orazi, V.
TBA
Revealing magnetic fields towards massive protostars: a multi-scale approach using masers and dust
Dall'Olio, Daria
Magnetic fields play a significant role during star formation processes, hindering the fragmentation and the collapse of the parental cloud, and affecting the accretion mechanisms and feedback phenomena. However, several questions still need to be addressed to clarify the importance of magnetic fields at the onset of high-mass star formation, such as at what evolutionary stage their action becomes relevant, how strong they are, and at what spatial scales they act._x000D_ Furthermore, the magnetic field parameters are still poorly constrained especially at small scales, i.e. few astronomical units from the central object, where the accretion disc and the base of the outflow are located. Thus we need to probe magnetic fields at different scales, at different evolutionary steps and possibly with different tracers._x000D_ I will show that the magnetic field morphology around high-mass protostars can be successfully traced at different scales by observing maser and dust polarised emission. A confirmation that they are effective tools is indeed provided by our recent results from 6.7 GHz MERLIN observations of the massive protostar IRAS 18089-1732, where we found that the small-scale magnetic field probed by methanol masers is consistent with the large-scale magnetic field probed by dust._x000D_ Moreover I will present results obtained from our ALMA Band 7 polarisation observations of G9.62+0.20, which is a massive star-forming region with a sequence of cores at different evolutionary stages. We resolve several protostellar cores embedded in a bright and dusty filamentary structure. I will then discuss the magnetic field morphology and strength in different cores and how it can be interpreted within the evolutionary sequence of the star formation process which is occurring across the filament.
Origin and evolution of the X-ray luminous circumgalactic medium
Davies, Jonathan
Observations reveal that the baryon fraction of dark matter haloes is a strong function of their mass. This likely follows from a mass-dependent balance between gravitational accretion on one hand and, on the other, consumption by star formation and heating from the feedback that accompanies star formation and black hole growth. Authoritatively predicting the origin of the hot circumgalactic medium (CGM) and the fate of the missing baryons thus requires simulations that reproduce the observed properties of galaxies and their gaseous environments.The EAGLE simulations reproduce a range of galaxy properties, and by coupling them to plasma emission tables we show they also reproduce properties of the hot CGM, such as X-ray surface brightness profiles and the Lx-M* and Lx-M_500 scaling relations. Scatter in the scaling relations is driven by the state of the gas: more luminous haloes at fixed mass have a hot CGM whose centre is denser and more metal-rich, and we predict they also host bluer galaxies. Reproduction of these diagnostics requires efficient feedback, particularly at z ~ 1-3 when halo accretion rates peaked, to eject and/or redistribute gas from halo centres. We trace the fate of these missing baryons, and we find them in a diversity of present-day environments: the majority reside in the halo outskirts, but some cool onto neighbouring galaxies.EAGLE indicates that the hot CGM was mostly heated by gravitational accretion shocks. However, because feedback acts on the densest and most enriched gas in the CGM, X-ray emission can be dominated by feedback-heated gas. For Milky Way-like galaxies, we find that feedback-heated gas dominates the luminosity of the hot CGM until z~0.5, when the contribution from gravitationally-heated gas becomes similar. However, since the highest surface brightness gas in halo centres is mainly heated by feedback, we caution that X-ray observations can provide a highly unrepresentative view of the physical state of the hot CGM.
Propagation of Cosmic-Rays and Gamma-Rays in the turbulent Intergalactic Medium
de Gouveia Dal Pino, Elisabete
The propagation of cosmic-rays and high-energy gamma-rays may induce electromagnetic cascades in the intergalactic medium (IGM), generating electron-positron pairs, whose opening angle is sensitive to the strength of intervening magnetic ?elds. This effect has been used to constrain the strength and coherence length of the turbulent intergalactic magnetic fields (IGMFs) which supposedly permeate the cosmic web up to the scales of the voids. Nevertheless, plasma instabilities arising due to interactions of the ionised component of the intergalactic medium with the electron-positron pairs may a?ect the development of electromagnetic cascades, potentially rendering this method ineffective.Here we present results of cosmic- and gamma-ray propagation in the IGM aiming at improving current constraints on properties of the IGMF. To this end, we have performed three-dimensional magnetohydrodynamical simulations of the turbulent IGM and studied the development of electromagnetic cascades in this background, exploring the interaction of test particles with the environment and computing the associated fluxes of cosmic- and gamma-rays.
Not-so-simple stellar populations in nearby, resolved massive star clusters
de Grijs, Richard
Around the turn of the last century, star clusters of all kinds were considered "simple" stellar populations. Over the past decade, this situation has changed dramatically. At the same time, star clusters are among the brightest stellar population components and, as such, they are visible out to much greater distances than individual stars, even the brightest, so that understanding the intricacies of star cluster composition and their evolution is imperative for understanding stellar populations and the evolution of galaxies as a whole. In this review of where the field has moved to in recent years, we place particular emphasis on the properties and importance of binary systems, the effects of rapid stellar rotation, and the presence of multiple populations in Magellanic Cloud star clusters across the full age range. Our most recent results imply a reverse paradigm shift, back to the old simple stellar population picture for at least some intermediate-age (~1--3 Gyr-old) star clusters, opening up exciting avenues for future research efforts.
PRIMitive Asteroids Spectroscopic Survey - PRIMASS: Current Status
de Leon, Julia
Primitive asteroids are considered transitional objects between rocky and icy bodies. They are characterized by their low albedo in the visible and their abundance in carbon and organic compounds. They are also expected to be volatile-rich, with a certain amount of hydrated minerals on their surfaces. The study of these bodies is crucial to understand the nature of volatile and organic materials in the early Solar System.At present, two primitive near-Earth asteroids (NEAs) are targets of sample-return missions: (101955) Bennu, target of NASA OSIRIS-REx and (162173) Ryugu, target of JAXA Hayabusa2. Characterizing the populations from which these NEAs might originate in the main belt will enhance the scientific return of the missions.In 2010, we started a spectroscopic survey in the visible and near-infrared to characterize primitive asteroids. Our PRIMitive Asteroids Spectroscopic Survey (PRIMASS) uses a variety of ground-based facilities. Most of the visible spectra have been obtained using unique capabilities of the 10.4m Gran Telescopio Canarias (GTC), while near-infrared spectra are obtained with the 3.6m Telescopio Nazionale Galileo (TNG), both located at the El Roque de los Muchachos Observatory (La Palma, Spain). We also use the 3.0m NASA Infrared Telescope Facility (IRTF) on Mauna Kea (Hawaii, USA) and the Southern Astrophysical Research Telescope (SOAR) at Cerro Pachon (Chile).Up to now, PRIMASS contains more than 500 spectra. Results on the Polana-Eulalia complex and the Erigone, Sulamitis and Clarissa inner belt families have been already published, and spectra have been obtained from members of the Klio, Chaldaea, Svea, and Chimaera families. In the outer main belt, we have obtained spectra of asteroids in five different but related groups of primitive bodies: the Hygea, Themis, and Veritas families, and also the Cybeles and Hildas dynamical groups. We present here the current status of our on-going survey.
Star formation in the Local Group with NIRSpec and NIRCam
De Marchi, Guido
I will present a NIRSpec GTO programme showcasing the multi-object spectroscopy capabilities of NIRSpec for stellar studies. We will obtain medium- and high-resolution spectra of hundreds of known pre-main sequence (PMS) stars with different ages hosted in massive starburst clusters in the Galaxy and Magellanic Clouds. These PMS stars were identified from HST photometry as objects with strong Hα excess emission (EW > 10Å). Each cluster contains about 500–1000 such PMS stars in a typical 3’x3’ field, thereby guaranteeing optimal filling of the NIRSpec Micro-Shutter Array. The ultimate scientific goal is to understand the very nature of the mass accretion process, and how the corresponding infall of gas from the circumstellar disc onto the star depends on the mass, age, and metallicity of the PMS object. This study is unique, since spectroscopic studies of PMS objects so far are limited to the solar neighbourhood and no information exists for massive starburst clusters and for non-solar metallicity. In particular, our observations will sample multiple hydrogen recombination lines (Paα, Brβ, Brγ), and from their intensities and profiles we will extract quantitative information on the nature, excitation, and kinematics of the infalling gas. I will also show how the parallel observations with the NIRCam instruments will allow us to discover new PMS stars and to measure their mass accretion parameters through narrow-band NIR photometry, which will be in turn directly calibrated by the NIRSpec spectroscopy. This study is bound to have important implications and set firm foundations for our understanding of the star formation process in both the local and the early Universe.
AGBs in binaries: Common envelope evolution
De Marco, Orsola
The common envelope binary interaction takes place when an expanding star transfers mass to a companion in an unstable manner leading to the companion entering the envelope of the giant. It leads to the ejection of the giant envelope and the emergence of a compact binary or to a merger. It also acts to interrupt the giant life, ejecting whatever its envelope contains into interstellar space, and producing an object (binary or single star) that would not exist in the absence of the interaction - like helium white dwarfs, CVs or type Ia supernovae, to mention a few. Both low mass companions and planets merging with AGB stars via a common envelope may alter profoundly the AGB star, including promoting nucleosynthesis and dredge up. Ultimately most of what we want to know about the common envelope interaction is in the hand of hydrodynamic models, which are themselves at the moment very limited in their ability to predict the various interesting effects we would like to know about. I will give an account of the latest advances in our knowledge of the common envelope interaction from theoretical and observational standpoints, as well as the impact of this phase in the life of galaxies.
FUV Spectrophotometry with the Cosmic Origins Spectrograph
De Rosa, Gisella
The Cosmic Origins Spectrograph (COS) was installed on the Hubble Space Telescope (HST) in May 2009. COS is designed to perform high-sensitivity spectroscopy in the far-ultraviolet (FUV) and near-ultraviolet (NUV) regimes with low-/medium resolution gratings. The COS FUV detector consists of two microchannel plates (MCPs). The spectrophotometric calibration of the FUV channel is complicated by several factors. First of all, the MCP’s efficiency at converting incoming photons into detectable events decreases with usage. This depletion of the detector’s gain (i.e. gain sag) results in unusable regions of the COS/FUV detector. The main culprit of gain sag is Lya geocoronal emission, even if all observations lead to gain sag. In order to mitigate the gain sag, a number of strategies have been employed over the instrument life time, which range from moving to different positions on the detectors, to managing the high voltage to extract a smaller amount of charge, to re-distributing the cenwave usage, to limiting the exposure of the affected detector to the geocoronal Lya. Moreover, the sensitivity of the COS FUV detector declines with time, with fluctuating rates that seem to correlate with the solar activity. Even taking all of this into account, the COS FUV sensitivity is still excellent, and with appropriate calibrations a local spectrophotometric precision of ~1.5% can be consistently reached over the whole wavelength range, as shown by an AGN reverberation mapping program performed in 2014 during Cycle 21 (PID 13330, De Rosa et al. 2015).
Modern statistical and machine learning methodologies applied to astrometric data
de Souza, Rafael
Astrometry and statistics have a long entangled history, and Astrostatistics is at the same time one of the oldest disciplines and one of the youngest. Of particular note was Hipparchus (190–120 BCE) who, following on the earlier work of Aristarchus of Samos (310–230 BCE and Eratosthenes (276–147 BCE), is widely regarded as the first to clearly apply statistical principles to the analysis of astronomical events. In 1801 Hungarian Franz von Zach applied the new least squares regression algorithm developed by Carl Gauss for predicting the position of Ceres as it came into view from its orbit behind the Sun.Nowadays, given the sheer volume and quality of astrometric data, modern methodologies are imperative to enable an optimal knowledge extraction from such data. Many different approaches, frequentist and Bayesian alike, are adopted by the astronomical community to exploit astrometric data, and to extract information from regression, clustering and classification solutions. These results have a broad impact in astronomy and astrophysics: from dynamical studies of open clusters, dwarf galaxies, and stellar streams, to stellar and galaxy astrophysics studies leading to near-field cosmology, and to more distant cosmological inferences from multiple calibrations of the distance ladder. In this talk, I will present an overview of some methods that are being adopted to probe astrometric data, and in particular, the ones currently used to explore the Gaia Data Release 2.
The IAU and French women astronomers
DÉBARBAT, Suzanne
Very soon after the creation, in 1919, of the IAU, in Bruxelles, following -by a few days only- the birth of the Conseil international des recherches (International Research Council) under the presidency of Benjamin Baillaud (1848-1932), the first Assemblée générale was held in Roma in 1922. More than two hundred members were there and two ladies were mentionned, Henrietta Swan Leavitt (1868-1921) and Fiammeta (1864-1920) Wilson (born Worthigton), as dead. This means that, even not so much in the IAU, female were already among the participants (members and guests). Two other ladies were present : miss Annie Jump Cannon (1863-1941) from Harvard College (US) and Dorothea Klumpke (1861-1942) widow of Isaac Roberts (1829-1904) as a French representative with her address in Thomery near Paris. Three years later, in 1925, three women appeared among members and guest and, in 1928, they are five, etc. Their increasing number followed the augmentation of total members of the IAU being almost 10 500 in 2017, that is to say about 17% of the total. In 1989, the author was asked to publish a paper on Astronomy, Geophysics and Women presented at the meeting Advances in Geosciences. Several other communications were later published. Others followed, developping aspects, related to women, corresponding mostly to astronomical activities. As an exemple, statistical studies about percentage of female astronomers for all adhering countries to IAU in 1991, later for France and Italy, etc. After recalling the corresponding evolution for adhering countries, a new examination of the situation, after about a new quarter of a century, will be developped.
The Evolution of Baryonic Angular Momentum in Simulated Disk Galaxies
DeFelippis, Daniel
The angular momentum of a galaxy encapsulates its complicated evolution. A relationship between the angular momentum of the dark matter and stellar components of galaxies has been found, as well as a clear differentiation between low-angular momentum ellipticals and high-angular momentum disks. Simulations have shown that feedback ejects gas from disk galaxies and boosts its angular momentum while in the circumgalactic medium (CGM), but the details of how and extent to which the CGM affects the angular momentum of galaxies is not well understood. I will present an analysis of the baryonic angular momentum of galaxies in the Illustris simulation done by following gas as it accretes onto Milky-Way mass halos, becomes part of the galactic wind, and eventually forms stars. The winds change the angular momentum of the gas in several ways: from preventing angular momentum loss to increasing angular momentum through “fountains.” I will discuss these and other effects of similar magnitude, from which I conclude there is a complex origin of the similarity between the specific angular momenta of galactic disks and halos. I will also present subsequent analysis of the angular momentum distribution of the CGM for a large population of IllustrisTNG disk galaxies over many masses and redshifts. By distinguishing between dynamically distinct components of the gas based on its temperature, density, and radial motion, I will draw connections between the angular momentum of the CGM and the effect of baryonic feedback on the gas as it travels through the CGM. Although these results are not directly comparable to current observations, they will provide a strong foundation for future observational work studying the dynamics of the CGM.
Detection of the WHIM: prospects for Athena
den Herder, Jan-Willem
TBA
Science from Space & ground-based Solar Instrumentation in China
Deng, Yuanyong
TBA
The origin of meteorites and near-Earth asteroids
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.
The common origin of family and non-family asteroids
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.
A fresh look on magnetic fields in halos of spiral galaxies
Dettmar, Ralf-Juergen
Recent numerical models of the multiphase ISM underline the importance of cosmic rays and magnetic fields for the physics of the ISM in disc galaxies. Observations of properties of the ISM in galactic halos constrain models of the expected exchange of matter between the star-forming disc and the environment (circumgalactic medium, CGM). We will present new observational evidence from radio-continuum polarization studies of edge-on galaxies on magnetic field strength and structure as well as cosmic ray propagation in galactic halos. The new findings result from the CHANG-ES (Continuum HAlos in Nearby Galaxies - an EVLA Survey; PI J. Irwin) project which has observed 35 edge-on galaxies with the Karl G. Jansky Very Large Array (JVLA) in two frequency bands (L- and C-band) and in three array configurations (D, C, B). This survey benefits significantly from the new multi-channel capability of the upgraded facility. From the total power maps, a "mean" radio-continuum halo has been derived and the polarization information provides information on the magnetic field structure in the halos. The findings will be discussed in the context of the disk-halo interaction of the interstellar medium. In addition, we will also briefly demonstrate how recent LOFAR observations of edge-on galaxies further constrain the extent of magnetic fields in galactic halos.
Astronomy Education: an astronomer's view
Deustua, Susana
Astronomy education encompasses a range of activity: scholarly research, professional development, capacity building, and teaching. The settings include classrooms, science centers, and parks, among others, and the audiences are equally varied. From an astronomer's viewpoint, I will briefly describe the changes in the perception of astronomy education and some of the highlights in its practice.
Astronomy Education: an astronomer's view
Deustua, Susana
Astronomy education encompasses a range of activity: scholarly research, professional development, capacity building, and teaching. The settings include classrooms, science centers, and parks, among others, and the audiences are equally varied. From an astronomer's viewpoint, I will briefly describe the changes in the perception of astronomy education and some of the highlights in its practice.
Absolute Spectral Calibration of Vega and Sirius
Deustua, Susana
Absolute flux calibration of standard stars, traceable to the International System of Units (SI) standards, is essential for 21st century astrophysics. Dark energy investigations that rely on observations of Type Ia supernovae and precise photometric redshifts of weakly lensed galaxies require a minimum accuracy of 0.5 % in the absolute color calibration. Research that address fundamental stellar astrophysics also benefit. In the era of new, sensitive telescopes designed for deep, sky surveys, e.g. WFIRST, well-characterized, SI-traceable standard stars that are available over the whole sky AND over a broad wavelength range (e.g. from the UV to the IR), and that do not saturate are needed. Prior work to obtain absolute flux measurements of fundamental standards: Vega, Sirius and others, achieved total uncertainties of ~1% to 3%, depending on wavelength. I will describe early results from a plogram to determine the top-of-the-atmosphere absolute spectral irradiance of bright stars wherein we have developed a novel, fully SI-traceable laboratory calibration strategy that will enable achieving the demanding 0.5% requirement. This strategy has two key components: 1) An SI-traceable calibration of the entire instrument system, and 2) repeated spectroscopic measurements of the target star throughout the night.
"George Ellery Hale's Internationalism"
DeVorkin, David
Here we outline the steps George Ellery Hale took to establish the new “astrophysics” as an international discipline, first through the creation of the Astrophysical Journal, and the need to establish a common language and then through the first decades of the 20th Century when he established international collaborations to coordinate solar and then stellar research. The latter effort, which began in 1904, by 1910 had expanded to encompass stellar astronomy, when the Solar Union deliberated over spectroscopic classification systems, a standard wavelength system and stellar magnitude systems. This work continued through the fifth meeting of the Union in Bonn in 1913, which turned out to be the last due to the First World War. During the war, Hale became Chair of the National Research Council of the American National Academy of Sciences, applying scientific talent to the winning of the war. He was also the Academy's Foreign Secretary, so after the war Hale became deeply involved in the creation of a means to re-establish international scientific relations. That means, designed in conjunction with Arthur Schuster and Emile Picard, became the International Research Council in 1919, which formed the framework within which the worlds of science reorganized themselves, and the International Astronomical Union was born. It was not an easy birth in a world still filled with tension and anger, and formative conferences in London and Brussels reflected the extremes. But born it was and its first General Assembly was held in Rome in 1922. It would be years before it became truly international, "in the complete sense of the word" (Ellis Strömgren), but many of the proposals made during the years of the Solar Union concerning disciplinary standardization were ratified. Here we will concentrate on this latter fact, remembering Hale for his devotion to internationalism.
Extended dust emission from nearby Asymptotic Giant Branch stars
Dharmawardena, Thavisha
Asymptotic Giant Branch (AGB) stars in the Milky Way are often overlooked due to difficulties in obtaining distances. Understanding their dust emission properties and mass-loss histories leads to better comprehension of the ISM evolution in the Milky Way, in particular its dust reservoir. Most studies have determined the stellar dust mass using mid-IR emission, but a historic cold dust reservoir from a previous mass-loss phase may remain undetected in the mid-IR, requiring observations at longer wavelengths.We present results of a search for extended dust emission from a diverse sample of AGB stars within 1 kpc. This project is part of the Nearby Evolved Star Survey (NESS), which aims to determine gas and dust return from a volume limited sample of galactic evolved stars.Observations at 450µm and 850µm were carried out using the SCUBA-2 instrument on the JCMT and combined with Herschel PACS observations at 70µm and 160µm from the MESS survey (Groenewegen et al., 2011; Cox et al., 2012). Using azimuthally-averaged surface brightness profiles we determined extension and percentage flux of the extended component for each source at the four wavelengths. We derived extensions at the 3s levels greater than ~40'' for majority of the sources at SCUBA-2 850µm. The fraction of the flux emitted from the extended region is ~40% at 850µm and ~50% at PACS wavelengths.By fitting a modified black body to four-point SEDs at each radial point we derive the dust temperature, spectral index of emissivity, and column density to probe dust mass-loss history and detect changes in physical properties of dust as a function radius (hence, time). The resulting dust-to-gas ratios are consistent with canonical values. The surface density profiles suggest deviation from constant mass loss in a majority of the sources.Here, we report a clear detection of the detached shell of U Ant in both 450µm and 850µm. This is the first time this detached shell has been detected in the sub-mm continuum.
Poster overview session
Di Cintio, Arianna
Poster overview session
The Square Kilometre Array (SKA): a physics machine for the 21st Century
Diamond, Phil
The Square Kilometre Array (SKA) is the next-generation radio-telescope and will be a true mega-science facility. SKA is being designed and built by a global partnership of 10 nations. The SKA Observatory will have sites in Australia and South Africa and a headquarters in the United Kingdom; it will build on the precursor telescopes, such as MWA, ASKAP, HERA and MeerKAT, which have been constructed on the sites. The SKA is being designed as a physics machine for the 21st Century and will address a huge range of scientific questions such as the nature of gravity, the origins of the Universe and the origins of life.The SKA is approaching the final stages of the detailed design phase. Funding of approximately €200M has been committed by the partner nations to deliver that design. The design will be complete at the end of 2018 and, assuming construction funding is secured, construction activities will begin in 2019. In this talk, I will briefly describe the science that SKA will do; and will provide an update on the status of the project, including the technical challenges associated with the design and delivery of a true ‘big data’ facility.
On the circumstellar envelopes of semi-regular long-period variables
DIAZ-LUIS, JOSE JAIRO
The mass loss process along the AGB phase is crucial for the formation of circumstellar envelopes (CSEs), which in the post-AGB phase will evolve into planetary nebulae (PNe). This transformation is relatively well known since many years, however, there are still important issues that would need to be further explored; in particular, the formation of axially symmetric PNe from spherical CSEs. Recent studies show that semi-regular variables (SRs) appear to have axi-symmetric envelopes, what implies that they lose mass in a different way than other evolved stars (e.g., Mira variables). In order to address the problem, we have conducted high S/N IRAM 30m observations of 12CO (J=2-1, 1-0) and 13CO (J=1-0), as well as Yebes 40m SiO (J=1-0) observations, in a volume limited sample of SRs. The CO molecule is the best tracer for total gas and provides a good description of the envelope structure, while SiO is expected to arise from the innermost regions of the envelopes. The results suggest a large prevalence of non-standard envelopes in these sources. We have characterized the main properties of the CSEs, such as expansion velocity, mass loss rate, wind density, etc. We have also explored possible relationships between these properties and the main stellar properties (e.g., effective temperature, pulsation, etc.). Interestingly, we report a very strong correlation between mass loss rates and the 12CO(1-0)-to-12CO(2-1) intensity ratio of the sample, introducing a new method for determining mass loss rates of SRs with short analyses time. We also find that for several stars the SiO profiles are very similar to those of the CO profiles, a totally unexpected result. This is not viable unless these are non-standard envelopes.
The event horizon telescope and beyond
Doeleman, Sheperd
The Event Horizon Telescope (EHT) is a Very Long Baseline Interferometry (VLBI) array operating at the shortest possible wavelengths, which can resolve the event horizons of the nearest supermassive black holes. Initial observations with the EHT have revealed Schwarzschild radius scale structure in SgrA*, the 4 million solar mass black hole at the Galactic Center, and in the much more luminous and massive black hole at the center of the giant elliptical galaxy M87. Over the coming years, this international project will add new sites, increase observing bandwidth and continue observations to focus on astrophysics at the black hole boundary. The EHT will have an unprecedented combination of sensitivity and resolution with excellent prospects for imaging strong GR signatures near the horizon, detecting magnetic field structures through full polarization observations, time-resolving black hole orbits, testing GR, and modeling black hole accretion, outflow and jet production. This talk will review progress and status of the project and describe future enhancements, including potential addition of space-based dishes to the array.
Hiding in plain sight? The search for the elusive super-AGB stars
Doherty, Carolyn
Super-AGB stars reside in the mass range ~ 6-12 Msun and bridge the divide between low/intermediate-mass and massive stars. They are characterised by off-centre carbon ignition prior to a thermally pulsing phase which can consist of many 10-1000s of thermal pulses. With their high luminosities and very large, cool, red stellar envelopes, these stars may appear seemingly identical to their slightly more massive red supergiant (RSG) counterparts and may act as massive star imposters in RSG surveys. However, as yet there has been no observationally confirmed super-AGB stars.Super-AGB stars undergo a variety of nucleosynthetic processes including proton-capture reactions at the base of the convective envelope and heavy element (s-process) production during the thermal pulses. The most massive super-AGB stars can also undergo a dredge-out event, where, a convective helium burning region merges with an inward moving convective envelope. When these zones meet, hydrogen is mixed down to very high temperature regions where a 13C rich region forms, leading to subsequent neutron release and heavy element (i-process) production. Also important for super-AGB stars is rotation, and in particular its impact to the surface composition relative to the process of second dredge up. The chemical surface enrichment from all of these processes has not yet been explored and may result in a clear nucleosynthetic signature to differentiate between super-AGB stars and (massive star) RSGs. The refining of this mass boundary has important implications for the energetics and chemical enrichment of galaxies.Here we present grids of rotating and non-rotating super-AGB star models along the entire TP phase and for (low mass) massive stars until the point of core collapse. These calculations span a broad range of metallicities from Z=0 to 0.04 an include both the first detailed heavy element nucleosynthesis for dredge-out events and super-AGB star nucleosynthesis including the impact of rotation.
Magnetic fields of T Tauri stars and their inner accretion discs
Donati, Jean-Francois
Magnetic fields are known to play a key role in the early life of stars and their planets, as they form from collapsing dense pre-stellar cores that progressively flatten into large-scale accretion discs and eventually settle as young suns orbited by planetary systems. Pre-main-sequence (PMS) phases, in which central protostars feed from surrounding planet-forming accretion discs, are especially crucial for understanding how worlds like our Solar System are born. In my talk I will review the latest results on magnetic fields of PMS stars and their inner accretion discs from optical spectroscopic and spectropolarimetric surveys, focussing on low-mass T Tauri stars (TTSs) either still surrounded by their accretion discs (classical TTSs) or in the process of exhausting it (transition and weak-line TTSs). I will also outline future prospects in this field using forthcoming near infrared spectropolarimetric facilities like SPIRou at CFHT.
Formation of families of small asteroids in light of latest research on the active asteroid P/2012 F5
Drahus, Michal
Since their discovery by Hirayama (1918, AJ 31, 185), asteroid families have been traditionally considered the products of collisions between asteroids. However, this long-standing view proves to be highly incomplete in light of the latest research conducted by our team. Using the Keck II telescope on Mauna Kea (Hawaii, USA), we have discovered several ultra-young fragments of the active asteroid P/2012 F5 and determined its rotation rate (Drahus et al. 2015, ApJL 802, L8). Thus, P/2012 F5 has become the first object in the Solar System with both of the properties robustly measured. Our research shows that the rotation rate of P/2012 F5 is the highest known among active asteroids (P = 3.24 hr) and high enough to explain the fragmentation of the object through rotational instability. Subsequent observations made with the Hubble Space Telescope show that P/2012 F5 has just formed a new asteroid family, and that it is likely the first identified asteroid family to originate from rotational fragmentation, rather than a collision with another body (Drahus & Waniak 2016, 48th DPS meeting, 522.03). The obtained results allow asteroid families to be divided into two separate categories: the century-old class of collisional families, and the new class of rotational families. The latter category generalizes the recently identified class of asteroid pairs – also formed by rotational break-up (Pravec et al. 2010, Nature 466, 1085), which we recognize as rotational families with two known components. Strengthless asteroids that are, at the same time, small enough to be susceptible to YORP spin-up, may undergo rotational fragmentation on a massive scale, thus constituting a significant source of families of small asteroids. The number of such families is likely to rise with an increase in the sensitivity of large-scale sky surveys.
Spatially resolved spectroscopy across stellar surfaces
Dravins, Dainis
Center-to-limb changes of spectral line profiles could in the past be studied only on the spatially resolved Sun but are now becoming accessible for also other stars. During exoplanet transits, successive stellar surface portions become hidden and differential spectroscopy between various transit phases provide spectra of small surface segments temporarily hidden behind the planet [1]. Such retrievals of spatially resolved high-resolution photospheric line profiles have now been achieved along the exoplanet transit chords across HD209458 (G0 V) and HD189733A (K1 V), using data from the ESO UVES and HARPS spectrometers [2,3]._x000D_ Not being subject to rotational broadening, spatially resolved profiles are narrower and deeper than those of integrated starlight while their gradual shifts in wavelength reflect stellar rotation at the latitude of exoplanet transit. Synthetic spectral lines from 3-D hydrodynamic models predict various center-to-limb signatures that differ among stars of different temperature, such as a gradually increasing linewidth toward the stellar limb, caused by horizontal velocities in stellar granulation being greater than vertical ones._x000D_ Since even giant planets cover only a tiny fraction of any solar-type star, the directly observable signal is small and extremely precise observations are required. To reach adequate signal-to-noise ratios, requires averaging over numerous lines with similar parameters. The method will likely be applicable to several more stars in the near future, as new targets are being found by ongoing searches for bright host stars with transiting large planets._x000D_ [1] Dravins, D., Ludwig, H.-G., Dahlén, E., & Pazira, H. 2017a, Astron. Astrophys., 605, A90_x000D_ [2] Dravins, D., Ludwig, H.-G., Dahlén, E., & Pazira, H. 2017b, Astron. Astrophys., 605, A91_x000D_ [3] Dravins, D., Gustavsson, M. & Ludwig, H.-G. 2018, Astron. Astrophys., to be submitted
The merger debris of dwarf galaxies in the local stellar halo
Du, Cuihua
In the standard hierarchical model of galaxy formation, the halos of galaxies like the Milky Way, are thought to form hierarchically via the accumulation of stars from dwarf galaxies and this merging process left behind many stellar streams and substructures in the Galactic halo. A number of distinctive characteristics of halo stars provide information about dwarf galaxies. Although the accumulated debris from old accretion events rapidly disperses in space, a significant amount of recognizable substructure should be visible both spatially and in phase-space distribution. Based on the first Gaia data release and spectroscopy from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 5, we are able to obtain the required full phase-space information of stars. The halo stars are identified by kinematics and metallicity. We fit a three-component Gaussian Mixture Model to the Cartesian velocities of the stars and use different metallicity to pick out halo stars. Then we perform a comprehensive analysis of the halo sample stars in the space of energy and angular momentum (E Vs. L_z) to determine the significant structures. The watershed algorithm is used to estimate extent of possible substructures and determine their constituent stars. Finally, we find 10 statistically significant substructures and these substructures are not reported by previous works. The retrograde stars with less bound energy may be all correlative to the progenitor galaxy of ω Cen. These structures may be the debris of dwarf galaxies accretion event and their dynamical and chemical informations can help to understand the history of the Milky Way.
The Virtual Atomic and Molecular Data Centre (VAMDC) - A ressource for Atomic and Molecular Data
Dubernet, Marie Lise
The "Virtual Atomic and Molecular Data Centre Consortium" (VAMDC Consortium, www.vamdc.eu) is a worldwide consortium which federates Atomic and Molecular databases through an e-science infrastructure and an organisation to support this activity (http://www.vamdc.org/structure/how-to-join-us/). About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for the modeling in media of many fields of astrophysics. The VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from different countries. The current VAMDC e-infrastructure interconnects about 36 atomic and molecular databases that cover atomic and molecular spectroscopy and processes. Table I provides a list both of the currently connected databases and of the databases that are currently being connected. VAMDC offers a common entry point to all encorporated databases through the VAMDC portal (http://portal.vamdc.eu) and VAMDC develops also standalone tools in order to retrieve and handle the data. VAMDC provides software and support in order to include new databases within the VAMDC e-infrastructure. One current feature of VAMDC e-infrastructure is the constrained environment for the description of data, in particular the XSAMS schema and other standardized protocols (http://www.vamdc.eu/standards) that ensure a higher quality for the distribution of data. The talk will present the VAMDC Consortium, the VAMDC e-infrastructure with the current status of its underlying technology, its services, current work being carried out in order to improve the infrastructure as well as discussions towards evolution of VAMDC within the astrophysics community. VAMDC is opened to new collaborations in order to support creation of tools for the users community.
GRAL: Search for Gravitational Lenses in GAIA DR2
Ducourant, Christine
The 'Gaia Gravitational Lenses' group (GraL) has dedicated efforts to systematically identify and characterize in current and future data releases of the ESA/Gaia satellite multiply imaged quasars by gravitational lensing. Owing to its exceptional angular resolution and very accurate photometry, Gaia is expected to observe about 3000 gravitational lenses among which 250 should have three or more lensed images. For the first time a survey of such phenomena over the entire sky is possible, thanks to Gaia, allowing to derive relevant constraints and invaluable dataset particularly well-suited for extragalactic and cosmological studies.Here we present the activities of the GraL working group, we describe the instrumental and observational characteristics that turn Gaia into a powerful tool for detecting these rare extragalactic phenomena. We detail the method we employed for identifying them and present the most promising candidates we extracted based on the second data release of Gaia. Finally, we see how the uncertainties on the parameters of the lens models can be dramatically reduced by comparing the modeling of already known lenses using Gaia observations, on one hand, and observations from other ground-based and space observatory on the other hand.
Solar Irradiance: from multiple observations to a single composite dataset
Dudok de Wit, Thierry
The solar electromagnetic spectrum and its evolution in time are paramount for understanding solar variability and for quantifying its impact on the Earth’s atmosphere. Even when physics-based irradiance models are continuously growing in maturity, solar irradiance observations remain indispensable.Several instruments have been monitoring the spectrally-resolved (and also the total solar irradiance) since the late 1980’s, mainly in the UV, but also in the visible. Despite being fragmented in time and in wavelength, these observations have deeply impacted our perception of how the Sun varies in time. Today, with the growing demand for understanding how the Sun varies on multi-decadal time scales, and a recent deep solar minimum, there is a clear need for investigating the presence of trends in these observations. Unfortunately, making radiometrically-stable observations is a real challenge; simultaneous observations from different instruments often disagree, which can lead to potentially very different long-term evolutions.Recently, several international teams have tackled this problem by merging individual observations into one single homogeneous composite dataset that would ease their scientific analysis and in particular offer the possibility to explore longer time scales. Here we address these different steps going from individual observations, their inter-calibration, to their fusion into one single composite, with its uncertainties and the critical issues.
Progress status of TMT
Dumas, C.
TBA
Spin-axis distribution of members of asteroid families
Durech, Josef
The spin state of members of asteroid collisional families is an important physical property that is affected by the initial conditions (presumably isotropic distribution of spin vectors) and by the secular evolution mainly due to the YORP effect. The rotation period, the direction of the rotation axis, and the global shape model can be derived for individual asteroids from their disc-integrated photometry by the lightcurve inversion method. This way, models of about 1650 asteroids have been derived, out of which ~600 belong to families. For other ~340 family members we have at least information about the ecliptic latitude of their spin axis, which allows us to distinguish between prograde and retrograde rotation. We will present our analysis of the distribution of spin axis of members of the largest asteroid families and discuss the results. In general, the observed distributions are in agreement with the theoretical expectation that the V-shape in the semimajor axis a vs. size D parameter space is caused by the Yarkovsky effect, which is dependent on the spin axis orientation. Therefore, asteroids that have larger semimajor axis than the center of the family are preferentially prograde, while those with smaller a are retrograde. In principle, the information about the spin axis distribution and its dependence on size is another constraint that can be used for family age estimation.
Beyond the Milky Way: galaxies in the Ophiuchus cluster
Durret, Florence
Ophiuchus is the second brightest cluster in X-rays in the nearbyuniverse, but due to its low Galactic latitude its optical propertiesremain poorly known. Based on a deep image of the Ophiuchus clusterin the r' band obtained at the CFHT with MegaCam, we have applied aniterative process to subtract the contribution of the numerous starsthat pollute the image, and obtained a photometric catalogue of 2818galaxies fully complete at r'=20.5 mag. We use this catalogue toderive the cluster Galaxy Luminosity Function (GLF) in several zones(defined with density maps), and for a region covering exactly thesame physical size as that in which the GLF of the Coma cluster wasstudied. The GLF fits are much better fit when a Gaussian is added tothe usual Schechter function, to account for the excess of very brightgalaxies. Compared to Coma, Ophiuchus shows a strong excess of brightgalaxies. The properties of the two nearby very massive clustersOphiuchus and Coma are quite comparable, though they seem embedded invery different large scale environments. Our interpretation is thatOphiuchus has built up long ago, as confirmed by its relaxed state,while Coma is still in the process of forming. Therefore, comparingcluster properties, even at low redshift, can give informations oncluster formation.
Triggered Star Formation inside the Shell of a Wolf–Rayet Bubble as the Origin of the Solar System
Dwarkadas, Vikram
A critical constraint on solar system formation is the high 26Al/27Al abundance ratio of 5 x 10-5 at the time of formation, which was about 17 times higher than the average Galactic ratio, while the 60Fe/56Fe value was about 2 x 10-8, lower than the Galactic value of 3 x 10-7. This challenges the assumption that a nearby supernova was responsible for the injection of these short-lived radionuclides into the early solar system. We show that this conundrum can be resolved if the Solar System was formed by triggered star formation at the edge of a Wolf-Rayet (W-R) bubble. Aluminium-26 is produced during the evolution of the massive star, released in the wind during the W-R phase, and condenses into dust grains (that have been observed around W-R stars in IR observations). The dust grains survive passage through the reverse shock and the low density shocked wind, reach the dense shell swept-up by the bubble, detach from the decelerated wind and are injected into the shell. The dust grains will be destroyed by grain evaporation or non-thermal sputtering, releasing the 26Al into the shell. Some portions of this shell subsequently collapses to form the dense cores that give rise to solar-type systems. The star will either collapse directly to a black hole, as in some models, or give rise to a supernova explosion. Even if the latter, the aspherical supernova does not inject appreciable amounts of 60Fe into the proto-solar-system, thus accounting for the observed low abundance of 60Fe. We discuss the details of various processes within the model using numerical simulations, as well as nucleosynthesis modelling, and analytic and semi-analytic calculations. We conclude that it is a viable model that can explain the initial abundances of 26Al and 60Fe. We estimate that 1%–16% of all Sun-like stars could have formed in such a setting of triggered star formation in the shell of a W–R bubble.
Discussion of C.C1 Newsletter
Eastwood, Kathy
During this short segment of the C.C1 Business Meeting we will discuss the newsletter. In particular we invite comments on the format and frequency of the newsletter. The most recent newsletters are available at the C.C1 website, iaucc1.frm.utn.edu.ar. If you are not able to make comments at the Business Meeting, please email them to kathy.eastwood@nau.edu.
The Solar-Stellar Dynamo-Irradiance Connection: What Stellar Lightcurves Tell Us About How the Dynamo Works
Egeland, Ricky
The Sun is the best observed object in all of astronomy. Itsproximity allows us to see the patterns of its well-ordered magneticcycle in great detail, at least on the surface. The problem, ofcourse, is that the magnetic dynamo producing the large-scale magneticfield operates beneath the surface, hiding the dynamo processes fromview and allowing models a great deal of flexibility. Solar andstellar astronomers have long believed that observing the long-termvariability of Sun-like stars might allow us to better constrain thephysics of the dynamo by relating observational effects of large-scalemagnetism to fundamental properties of the star. Among these effectsare small variations of flux in medium and wide-band visiblephotometry typically obtained in stellar astronomy. Such variabilityis correlated to more effective proxies of stellar magnetism ininteresting ways that can provide discerning tests for physical modelsof irradiance. In this talk I will review the current observationalconstraints stellar observations impose on dynamo theory and ourunderstanding of stellar photometric variability from long-termprograms such as the Fairborn Observatory Automated PhotometricTelescopes and the shorter-term Kepler observations. Finally, we willdiscuss the potential for new and upcoming programs like TESS, PLATO,and LSST to enable much larger statistical studies on the relationshipbetween irradiance variability and fundamental stellar properties.
Long-Term Asteroid Orbit Deflection Optimization
Eggl, Siegfried
Current technology would in principle allow humankind to avert catastrophic collisions between asteroids and our planet. Asteroids that could impact near a population center may be diverted using so-called kinetic impactor spacecraft. The latter would transfer momentum to the asteroid through a high-velocity collision. Differences in asteroid shape and composition, however, cause the magnitude and direction of the delivered momentum to be uncertain. Without accurate information on where an asteroid is “parked” after a deflection attempt, the same object may become a concern for planetary defense at a later date. In the worst case, the target asteroid enters a so-called “gravitational keyhole,” retaining a high probability to collide with our planet. In this contribution we demonstrate how to best target an asteroid during a kinetic deflection maneuver so as to minimize the chances of an Earth impact in the foreseeable future.
The Prague GA, Pluto and changes to the statutes,
Ekers, Ron
At the Sydney IAU GA the statutes were modified to remove the votes by individual members. Few noticed this at the time but the subsequent reaction by disenfranchised members led us to revise this position in Prague. The need to have a members vote on the status of Pluto was complicated by these changes and the drama behind the scene at the Prague GA where the planet definition was resolved is not well known despite the huge public impact of this GA. I will describe some of the activities of the executive and its working groups during this very exciting GA. The IAU structures served us well during this process but of course there were also many lessons learned.
Massive stars as drivers for the chemical enrichment of dwarf galaxies
Ekström, Sylvia
After reviewing the main physical process governing the evolution of massive stars, we will consider the way the low-metallicity environment found in dwarf galaxies modifies these processes. The impact on their nucleosynthesis and thus on the expected chemical enrichment driven by massive stars is reviewed.
Clumpy wind accretion in Supergiant X-ray Binaries
EL MELLAH, Ileyk
Supergiant X-ray Binaries host a compact object, generally a neutron star, orbiting an evolved O/B star. Mass transfer proceeds through the intense radiatively-driven wind of the stellar donor, a fraction of which is captured by the gravitational field of the neutron star. The subsequent accretion process onto the neutron star is responsible for the abundant X-ray emission from those systems. They also display variations in time of the X-ray flux by a factor of a few 10, along with changes in the hardness ratios believed to be due to varying absorption along the line-of-sight. We used the most recent results on the inhomogeneities (aka clumps) in the non-stationary wind of massive hot stars to evaluate their impact on the time-variable accretion process. We ran three-dimensional simulations of the wind in the vicinity of the accretor to witness the formation of the bow shock and follow the inhomogeneous flow over several spatial orders of magnitude, down to the neutron star magnetosphere. In particular, we show that the impact of the clumps on the time-variability of the intrinsic mass accretion rate is severely damped by the crossing of the shock, compared to the purely ballistic Bondi-Hoyle-Lyttleton estimation. We also account for the variable absorption due to clumps passing by the line-of-sight and estimate the final effective variability of the mass accretion rate for different orbital separations. These results are confronted to recent analysis of Vela X-1 observations with Chandra by Grinberg et al (2017). It shows that clumps account well for time-variability at low luminosity but can not generate, per se, the high luminosity activity observed.
Stars re-shaping galaxies
El-Badry, Kareem
TBA
IAU Strategic Plan: the Office of Astronomy for Education
Elmegreen, Debra
The IAU Strategic Plan for 2020-2030 has just been completed. Among other activities, it details the 3 main offices of the IAU: the Office of Astronomy for Development (OAD), the Office for Astronomy Outreach (OAO), and the Office for Young Astronomers (OYA). One of the highlights of the new plan is a proposal to create a new office, the Office of Astronomy for Education (OAE). This office will provide training and resources for teachers, using astronomy as a tool for stimulating STEM studies. It will establish a network of National Astronomy Education Coordinators, build a database of IAU volunteers, and organize an International School for Astronomy Education. The details of how this office will complement and synergize with the other offices are to be determined.
IAU’s interaction with young astronomers
Engvold, Oddbjorn
The International Astronomical Union supports several educational programs for young astronomers and events aimed to strengthen interaction between younger and more senior astronomers. The latter is represented by the Young Astronomers Luncheons that have become a tradition in recent IAU General Assemblies. The more far-reaching educational programs are the International Schools for Young Astronomers (ISYAs) for a 3-week school in developing countries and Commission 46 Astronomy Education Development (TAD) programs of shorter duration, where both initiated in 1967. The ISYAs aim to strengthen existing astronomical education in host countries while the objectives of the TAD programs are to enhance and improve the astronomy and science education in countries where that may be wanted. The objective of this brief presentation is to focus on mutually beneficial aspects of the strengthened contacts and interactions between the students, their host institution and the involved international milieus in astronomy.The IAU Educational Programs are described in two articles written by Michele Gerbaldi and by Michele Gerbaldi, Jean-Pierre DeGreve and Edward Guinan that are available from the IAU ISYA web site.
The primordial magnetic field in our cosmic backyard
Enßlin, Torsten
We present a reconstruction of the actual 3D structure of magnetic fields, which were seeded by density perturbations during the radiation dominated epoch of the Univerese and later on were evolved by structure formation. To achieve this goal, we rely on three dimensional initial density fields inferred from the 2M++ galaxy compilation via the Bayesian BORG algorithm. Using those, we estimate the magnetogenesis by the so called Harrison mechanism. This effect produces magnetic fields exploiting the different photon drag on electrons and ions in vortical motions, which are exited due to second order perturbation effects in the Early Universe. Subsequently we study the evolution of these seed fields through the non-linear cosmic structure formation by virtue of a MHD simulation to obtain a 3D estimate for the structure of this primordial magnetic field component today. At recombination we obtain a reliable lower limit on the large scale magnetic field strength around 10?²³ G, with a power spectrum peaking at about 2 Mpc?¹ h in comoving scales. At present we expect this evolved primordial field to have strengthts above ˜ 10?²7 G and ˜ 10?²? G in clusters of galaxies and voids, respectively. We also calculate the corresponding Faraday rotation measure map and show the magnetic field morphology and strength for specific objects of the Local Universe.
Galactic tomography via information field theory
Enßlin, Torsten
Charting the 3D structure of the Milky Way from astrometric and astrophysical measurements is an information theoretical problem. The finite data provided by instruments is never able to constraint the infinite degrees of freedom of the 3D fields of the various physical quantities, like gravitational potential, gas, dust, dark matter densities, and others. Additional information like physical laws and empirical correlations has to be folded into the field inference. Information field theory (IFT) is a generic Bayesian framework for field reconstruction that enables the consistent fusion of measurement data and theoretical concepts. I will review the progress on IFT-based methods to reconstruct the 3D structure of the Milky Way in various quantities and discuss requirements for instrument descriptions that permit such analysis. Finally, I will present the concept of an Universal Bayesian Imaging toolKit (UBIK) to fascilate multi-dimensional field reconstructions.
Science Communication Research in Astronomy: IAU CC Working Group
Entradas, Marta
The ‘Science Communication Research in Astronomy Working Group (WG) (CC2)’ was created in 2016 under Commission C2, Communicating Astronomy with the Public (CAP). The WG emerged from the need to bring closer together theory and practice in science communication. One of the biggest challenges facing science communication is the polarization between practice and research. Empirical evidence in astronomy communication is scarce, yet necessary to improve public engagement with science. This WG emerged in this context with a mission to create a space for reflection and discussion about the needs in astronomy public communication, to produce empirical evidence on astronomy communication, and to serve as a platform to strengthen the boundaries between the fields of science communication research and practice. The deliverable proposed by the WG for its first couple of years was a global study of the outreach practices of the IAU membership, which has been fully accomplished. In the IAU 2018, the WG will present the main activities of the WG between 2016-2018.
A 3D Universe? Students’ and professors’ perception of multidimensionality
Eriksson, Urban
Recently in the astronomy education research literature, the competency to be able to extrapolate three-dimensionality in ones’ mind from 1D and 2D representations has been identified as an important factor for success in learning astronomy and understanding the Universe. However, only little research has been done in investigating this competency (Eriksson 2014; Heyer et al. 2013), while at the same time there is a growing interest for what and how 3D representations can contribute to learning astronomy. This paper discusses this competency and reports on the preliminary findings from an investigation concerning students’ and professors’ perception of three-dimensionality when looking at 2D representations (images and movies) of a sample of nebulae. The preliminary results indicate that the competency to extrapolate three-dimensionality vary significantly between the participants and in particular many students struggle to see nebulae as 3D objects, which confirms earlier studies (see, for example, Eriksson et al 2014). An awareness of these findings by astronomy educators may have great importance for how teaching and learning astronomy are viewed and also how curricula development could be enhanced for optimizing teaching and learning astronomy at university level. Implications related to these findings will be discussed.ReferencesEriksson, U., et al., Who needs 3D when the Universe is flat? Science Education, 2014. 98(3): p. 31.Heyer, I., S. Slater, and T. Slater, Establishing the empirical relationship between non-science majoring undergraduate learners' spatial thinking skills and their conceptual astronomy knowledge. Revista Latino-Americana de Educação em Astronomia - RELEA, 2013(16): p. 45-61.
Atmosphere models from inversion of high-resolution spectropolarimetric observations for solar irradiance reconstructions
Ermolli, Ilaria
In semi-empirical models of solar irradiance variability, the radiative output of the Sun is reconstructed by combining the information about the spatial distribution of solar surface magnetism in resolved full-disc observations with the intensity contrast of solar surface features calculated by the solution to the radiative transfer equation in atmosphere models representative of the various features observed on the solar disc. Up till recently these atmospheres were 1D semi-empirical models presented in the literature, while now they can also be 3D atmospheres from magneto-convection simulations. We aimed to further extend the current semi-empirical models of solar irradiance variability to incorporate atmosphere models from state-of-the-art high-resolution solar observations. We analyzed spectropolarimetric data of the Fe I 630 nm line pair and of the Ca II 854.2 nm line obtained in regions that are representative of the granular quiet-Sun pattern and of small- and large-scale magnetic features, both bright and dark with respect to the quiet-Sun. We derived atmosphere models of the observed regions from data inversion and discussed the obtained atmospheres with respect to several atmosphere models presented in the literature. We herewith present the accuracy of our spectral synthesis computations on our observation-based atmospheres for application in solar irradiance estimates.
Gaia Photometric Catalogue: the calibration of the DR2 photometry
Evans, Dafydd
Gaia DR2 was released in April 2018 and contained a photometric catalogue of more than 1 billion sources. This release contains colour information in the form of integrated BP and RP photometry in addition to the latest G-band photometry. The level of accuracy can be as low as 2 mmag with some residual systematics at the 10 mmag level. This addition of colour information greatly enhances the value of the photometric data for the scientific community. A high level overview of the photometric processing, with a focus on the improvements with respect to Gaia DR1, will be given. The definition of the Gaia photometric system, a crucial part of the calibration of the photometry, will also be explained. Finally, some of the photometric improvements expected for the DR3 data release will be described.
Spectroscopy of extragalactic massive stars with the ELT
Evans, Chris
With the 8-10m class observatories we have observed the most luminous supergiant stars in galaxies out to distances of several Mpc. This has provided direct abundance estimates of their host systems for comparisons with nebular diagnostics. However, to improve our understanding of the evolution of massive stars, there is a longstanding desire to also observe main-sequence OB-type stars in systems beyond 1 Mpc. This will give us, for example, the chance to explore the properties of massive stars in very metal-poor galaxies and the broad range of environments in the galaxies of the Sculptor group, and beyond. I will introduce simulations of visible spectroscopy of O-type stars undertaken to investigate the capability of the ELT-MOSAIC concept, but that will also be relevant to future thinking for TMT-WFOS and GMT-GMACS. An even more exciting prospect is if we were also then able to obtain UV spectroscopy of the same indvidual stars beyond 1 Mpc - I will highlight strong synergies of the ELTs in this context with the LUVOIR and HabEx missions being studied by NASA as part of the US Decadal Survey.
AGN Feedback in Clusters of Galaxies
Fabian, Andrew
Accreting black holes in Brightest Cluster Galaxies power jets whichblow bubbles in the surrounding intracluster medium. Such AGN Feedbackis commonly observed as radio-emission-filled cavities in ChandraX-ray images of cool core clusters. Good agreement is obtained betweenthe feedback power determined from the bubbles and the rate ofradiative energy loss from the hot gas in the core. Catastrophiccooling of the intracluster gas is thereby prevented. I discuss howthe energy can be transported and dissipated throughout the clustercore. Feedback operating in this way appears to be ubiquitous inearly-type galaxies, groups and cool core clusters over a wide rangeof mass and redshift.
The Jet-Disk Model for the Galactic Center and other AGN
Falcke, Heino
The Galactic center host a well-known flat-spectrum radio source, Sgr A*, that is akin to the nuclei of quasars and radio galaxies. There is still some discussion on where the persistent and flaring emission of that source originates from. Does it come from an accretion flow or is it produced in a relativistic jet-like outflow? Answering this question is not only important for understanding the plethora of multi-wavelength data available for Sgr A*, it is also crucial for interpreting upcoming VLBI images of the shadow of the event horizon. Using advanced three-dimensional general relativistic magnetohydrodynamics simulations coupled to general relativistic ray tracing simulations, we can now model the dynamics and emission of the plasma around starving black holes in great detail out to several thousand Schwarzschild radii. Jets appear almost naturally in theses simulations. A crucial parameter is the heating of radiating electrons and we argue that electron-proton coupling is low in the accretion flow and high in the magnetized region of the jets, making the jet an important ingredient for the overall appearance of the source. This comprehensive model is able to predict the radio size and appearance, the spectral energy distribution from radio to X-rays, the polarization properties, the variability, and the time lags of Sgr A* surprisingly well. Most interestingly, the same model can be easily generalized to other jet sources like M87 and other radio galaxies.
Interstellar turbulence
Falgarone, Edith
Fifteen years after the one-hundred-page review of Elmegreen and Scalo on interstellar turbulence, do we understand better what it is? Their review was ending by:“Our current embrace of turbulence as an explanation for interstellar matter structures and motions may be partly based on an over-simplification of available models and a limitation of observational techniques. This state of the field guarantees more surprises in the coming decades.”Surprises have been delivered indeed, thanks to the prodigious improvement of observational capabilities and the 100-fold increase of computer power. I will focus on a few of them, in the perspective of an upcoming decade of further discoveries.
NEW PERSPECTIVES ON GALACTIC ANGULAR MOMENTUM, GALAXY FORMATION, AND THE HUBBLE SEQUENCE
Fall, Michael
Galaxies of different Hubble type and bulge-to-total ratio (B/T) follow nearly parallel sequences in a plot of specific angular momentum (j = J/M) against mass M. This j-M diagram is a powerful tool for describing galaxies and for understanding in physical terms how they formed and evolved. Several years ago, Aaron Romanowsky and I made a major study of the galactic j-M diagram, based on extensive photometric and kinematic data for ~100 galaxies of all Hubble types spanning a wide range of masses (published in 2012 and 2013). This talk is based on an extension of our earlier work, highlighting results we have obtained in the past year (and not yet published). In particular, we now determine explicitly whether the angular momenta of bulges and disks are correlated with or independent of each other. This result places important constraints on formation mechanisms of galactic bulges, especially satellite capture versus disk instability. We also determine whether classical bulges and pseudo bulges follow similar or different relations in the j-M diagram (an issue raised by Obreschkow & Glazebrook 2014). This again has implications for how bulges formed. The results presented here also have a bearing on recent studies of the j-M diagram and the relation between the sizes of galaxies and the sizes of their dark halos at high redshifts. In particular, the z = 0 forms of these relations provide important anchors for their high-redshift counterparts.
Observing the Warm and Hot Baryons at Low Redshift
Fang, Taotao
Theory suggests that a significant amount of the "missing baryons" at low redshift are distributed outside or at the vicinity of galaxies in the form of low-density, warm-hot gas. However, observing of this warm-hot gas, especially in the X-ray band, remains elusive, largely due to the faintness of the expected signals. In this talk, I will review recent progress in this field. I will also discuss the baryons in the vicinity of galaxies, the so-called "circum-galactic medium", and their implication of solving the "missing baryons" problem.
Astronomy from Pure to Social Science
Farmanyan, Sona
The present study is proposed helping people to learn about the Universe in a new way. The involvement of culture in Astronomy teaching and outreach will make this natural science social one. We will prove that informal representation of Astronomy is a spontaneous process, which helps people to learn about the Universe in a new way. Informal teaching of Astronomy is often used to describe the learning activities of everyday life. For achieving productivity in the informal astronomy, we suggest usage of culture as a main tool. Our examples will be focused on Cultural Astronomy, which includes ancient observatories, petroglyphs, calendars, astronomical charts, as well as space themes in mythology, folklore, art, poetry and painting. A link between science and public will be drawn and by this informal education will be promoted. We will point out a number of examples to help the public examine their daily relationship with the Universe. We will conclude by identifying ancient nation’s pantheistic and cosmological perceptions, world view, notions and beliefs related to the Universe. It is believed that knowledge of ancient Astronomy we will awaken the public desire to learn more about the modern Astronomy achievements.
On the tidal stripping of Local Group dwarf galaxies and the origin of their stellar mass-velocity dispersion relation
Fattahi, Azadeh
I use APOSTLE high-resolution hydrodynamical simulations of Local Groups combined with tidal stripping models to discuss the origin and shape of the stellar mass-velocity dispersion (Mstar-sigma) relation observed for Local Group dwarfs. I show that the tidal stripping of dwarfs embedded in cuspy dark matter halos, combined with the steep stellar mass-halo mass relation in Lambda-CDM can naturally explain the observed Mstar-sigma relation. On the other hand, tidal stripping of dwarfs embedded in cored dark matter halos would face challenges to explain the shape of the Mstar-sigma relation.Based on our prediction, the existence of low surface brightness, low mass satellites of the Milky Way and Andromeda (an extreme example is the recently discovered Crater 2 Milky Way satellite) can only be reconciled with LCDM models if they are the remnants of once massive objects heavily affected by tidal stripping. I infer their progenitor masses, radii, and velocity dispersions, and find them in remarkable agreement with those of isolated dwarfs. I predict that the extreme cases (including Crater 2) should have lost more than 99 percent of their original stellar mass, and should have left some imprints in the stellar halo of the Milky Way as tidal features.
Report of the Working Group on Spectroscopic and Radiative Data for Molecules
Federman, Steven
We provide a summary of our Working Group report that covers the period since the last General Assembly. The report discusses recent experimental and theoretical results for rotational, vibrational, and electronic transitions in molecules of relevance to astronomical studies. Related efforts on transition probabilities, lifetimes, oscillator strengths, and radiative cross sections are also described.
Star formation in cloud cores – simulations and observations of dense molecular cores and the formation of solar mass stars
Federrath, Christoph
I will present an invited review on star formation in molecular cloud cores. The focus will be on the roles of gravity, turbulence, magnetic fields and feedback (jets and radiation) for the star formation rate and the initial mass function of stars.
Episodic accretion in focus: revealing the circumstellar environment of FU Orionis-type stars with millimeter interferometry
Fehér, Orsolya
The earliest phases of star formation are characterised by intense mass accretion from the circumstellar disk to the central star. FU Orionis-type stars (FUors) also exhibit accretion rate peaks accompanied by bright eruptions. These recurring outbursts might represent an important evolutionary period that may solve the luminosity problem of young stellar objects (YSOs), play a key role in accumulating the final star mass, and can have a significant effect on the parameters of the envelope and the disk, and consequently the processes of planet formation. In the framework of the Structured Accretion Disks ERC project at Konkoly Observatory we are conducting a systematic investigation of FUors to examine whether these outbursting objects represent normal embedded young stars in exceptional times (implying that all low-mass young stars undergo eruptive phases) or they are unusual objects.Using IRAM and PdBI/NOEMA millimeter wavelength single-dish and interferometric measurements we mapped the 12CO, 13CO, C18O and 2.7 mm continuum emission towards 12 northern FUors, reaching spatial resolutions of 2-4” (~1000 AU). We also surveyed the 108-116 GHz frequency range, searching for molecular transitions characteristic to young stellar systems. We revealed a diverse sample of circumstellar morphologies and identified internally heated, circular envelopes, outflows, envelope rotation, neighbouring sources and large-scale shock fronts. The detection of several molecular species (e.g. C17O, HC3N, SO, CN) can be used for chemical modeling of the circumstellar environments. Comparison of the envelope parameters among the FUors and to the parameters of quiescent YSOs show that some FUors are similar to embedded Class I stars, while others have only small envelopes, resembling Class II sources. This reinforces the theory that FUors are in a special evolutionary phase between the two classes and their infall-driven episodic eruptions are the main driving force of the transition.
Revisiting the Oort cloud in the age of large sky surveys
Fernández, Julio A.
Our knowledge about the Oort cloud rests on the so-called new comets, namely comets whose original orbital energies are very close to zero (i.e. near-parabolic orbits), suggesting that they are coming to the inner planetary region for the first time. We have analyzed the sample of observed new comets that reached the planetary region in the last 20 years (1998-2017), which corresponds to the period when large sky surveys have come into operation with the consequence of a dramatic increase in the discovery rate of minor bodies. From the analysis of the sample of new comets and using a debias technique based on the ``excess magnitude'' (Everhart 1967, Astron. J. 72, 716), we find that the influx rate of comets with original energies in the range 0 < x < 30 (in units of 10-6 au-1) has remained more or less constant in time and uniform in perihelion distances at a rate of 0.4 comets yr-1 au-1 brighter than absolute total magnitude H=9. These are essentially comets coming from the outer Oort cloud (semimajor axes a > ~3.3 x 104 au) where perturbations by external perturbers (galactic tides and passing stars) are able to inject comets with perihelion distances outside the planetary region (q > 30 au) in the inner planetary region in a single revolution. By constrast, the influx rate of comets coming from the inner portions of the Oort cloud (energies 30 < x < 100) is found to increase with the perihelion distance. This suggests a dynamical process of kreeping into the inner planetary region after several passages by the outer planetary region, and where some comets can finally leak through the Jupiter-Saturn barrier into the cis-Jovian region. These results are of fundamental importance to set more stringent constraints on the population and space distribution of comets in the Oort cloud, and from this on mass transport processes and scattering of bodies in the early solar system.
Outreach Professionalisation & Accreditation
Fienberg, Rick
The Outreach Professionalisation & Accreditation Working Group (WG) was formed in 2012 under Commission C2’s predecessor, Commission 55, also called Communicating Astronomy with the Public (CAP). Its mission was “to bring a sense of professionalism and professional respect to the field of astronomy communication, to advocate for our needs as professional communicators, and to serve as a means for information sharing and networking.” Its deliverable was “a procedure to handle requests for IAU associate membership (presumably including several levels of accreditation) and methods/standards/requirements for achieving accreditation.” Here we report on the WG’s activities during the 2015-2018 triennium and look ahead to the 2018-2021 triennium.
Message by New IAU Commission C2 President
Fienberg, Rick
IAU Commission C2, Communicating Astronomy with the Public (CAP), is one of the largest and most active commissions within the IAU. It also has one fo the most diverse memberships, including not only professional astronomers but also professional science communicators such as press officers and journalists, planetarium producers and presenters, researchers into the science of science communication, and both formal and informal science educators. In addition to regular IAU members, C2 has many Associates, perhaps more than any other IAU scientific body. The work of the Commission is done primarily through its Working Groups (WGs). In the last triennium, we had five WGs. Two — WG CAP Journal and WG CAP Conference — were very active; three others were less active. A major question for the 2018-2021 triennium is which WGs to keep, which to discard, which to change, and what new ones are needed. In this interactive session, we’ll present some ideas about what C2 might focus on during the coming triennium and provide an opportunity for attendees to offer their own suggestions and to ask questions of the C2 leadership.
INPOP planetary ephemerides: updates about P9 localization
fienga, agnes
In this talk proposed for the planets days workshop, we will present recent progress in the INPOP planetary ephemerides. We will describe how in using Cassini and Juno radio science data, new constraints about P9 localization have been found, compatible with dynamical studies such as (Mulholland and Laughlin 2017) or (Batygin and Brown 2016). We will also discuss the role of other possible perturbations in our constraints on P9 localization.
Historical Telescopes and Astronomy Outreach
Figueiró Spinelli, Patrícia
The Night-Sky Observation Program (POC, acronym in Portuguese for Programa de Observação do Céu) is the most traditional education activity run by the Museum of Astronomy and Related Sciences (MAST) in Rio de Janeiro, with an annual participation of 2,400 people. It starts with a brief talk and is followed by the observation with MAST's telescopes, one of them being over a century old. Data collected from POC’s evaluation research in 2015 pointed that its participants perceive the historical value of the old refractor and declare that the activity brought them feelings of wonderment. These declarations have motivated us to conduct a study to identify and exchange experiences with worldwide institutions that also use historically valuable telescopes in their night-sky observation activities with the public. With the goal of gathering information from these places and making it into a guide, an online questionnaire with open and close-ended questions was launched in late 2017. We define what the respondents understand as a “historically valuable instrument” by using the Likert scale. We have received 80 responses of institutions from all continents. The information collected is vast and rich and not only tells about the passion of those mediating such activities, but also the history of astronomy itself. The majority of the respondents has described that the participants of the activities experience similar feelings towards the instrument as those found in POC's research. In addition, we have found that only half of the instruments has been classified or considered as an object of cultural heritage, which is a source of concern. In this contribution, I will present the main results of our survey and introduce our guide.
Infrared Weak-Lensing Analysis of the Emerging Galaxy Cluster SPARCSJ1049+56 at z=1.7
Finner, Kyle
The hierarchical formation model of structure in the universe suggests that galaxy clusters are assembled through a series of mergers. In turn, it is expected that galaxy clusters in the early universe are actively forming and dynamically young. Located at a high redshift of 1.7, SpARCSJ1049+56 offers a unique look into the galaxy cluster formation process. This cluster has been shown to be rich in cluster galaxies and have intense star formation in the brightest cluster galaxy. At such high redshift, the cluster pushes a weak-lensing analysis beyond the regime of the optical spectrum into that of the infrared. Equipped with deep Hubble Space Telescope WFC3 UVIS and IR observations, we present a weak-lensing characterization of SpARCSJ1049+56. As few IR weak-lensing studies have been performed, we discuss the details of point spread function modeling and galaxy shape measurement for an IR weak-lensing procedure and the systematics that come with the territory. Through a careful analysis, the mass distribution of this young galaxy cluster is mapped and compared to the galaxy distribution. The mass of the cluster is quantified by a mass-concentration relation and compared to the mass derived from galaxy velocity dispersion. Further tests are performed to ponder the accuracy of using a mass-concentration relation for galaxy clusters in an early state of formation.
Stellar population in Local Group and Local Volume galaxies.
Fiorentino, Giuliana
The era of science driven telescopes is starting. The Extremely Large Telescope is a big technological challenge and, in order to exploit its potential, it will be assisted by sophisticated Adaptive Optics systems (e.g. MAORY). I will review some science cases that will become possible using the power of extreme high resolution imaging offered by a 39-meter telescope working at its diffraction limit, as the search for intermediate mass black hole in dense environments within the Local Group (young compact or globular clusters); the study of the stellar populations of very compact objects as the poorly known Elliptical galaxies in the Local Volume and out to the Virgo cluster. On the basis of updated simulations, I will show that resolved stellar populations in the Local Volume (~10M pc) will experience a new era; we expect to reach details Today only possible in the Local Group.
The Formation of Dense Gas within Magnetized Molecular Clouds: A BLASTPol Study of the Vela C Giant Molecular Cloud
Fissel, Laura
I will show comparisons between the magnetic field morphology of the young giant molecular cloud Vela C, as traced by the BLASTPol balloon-borne sub-mm polarimeter, and the orientation of elongated molecular gas structures, as traced by molecular line maps from the Mopra telescope. We find that low-density tracers 12CO and 13CO are statistically more likely to align parallel to the magnetic field, while intermediate or high density tracers show either no preferential alignment or a tendency for alignment perpendicular to the magnetic field. The transition from parallel to perpendicular orientation occurs at a molecular hydrogen number density of approximately 103 cm-3, though there are indications that this transition density may be much lower for the “Centre-Ridge” cloud sub-region, which harbours the highest column density filaments in Vela C and has already formed several high mass stars. Our results suggest that the magnetic field in Vela C is strong enough to have influenced the formation of cloud sub-structures, and further imply that the orientation of the magnetic field with respect to the convergent flows that created Vela C may have affected the efficiency with which dense gravitationally unstable molecular gas was formed in the cloud sub-regions.
International Studies of Astronomy Education Research Database (iSTAR). Reaching Critical Mass.
Fitzgerald, Michael
The international Studies of Astronomy education Research (iSTAR) online abstract database and repository is the result of a concerted effort by an international community to collect and categorize existing research from conference proceedings, books, journal articles, theses and the grey literature. Over the last five years, over 1750 items have been catalogued in the online database, istardb.org.Over the course of 2016 to 2018, an extensive trawl of the literature has taken place. Of most significance since the first light dissertation study (Slater et al. 2016) and a review of the planetarium literature (Slater & Tatge 2017), all science education journals classified in Scopus have been searched thoroughly to identify astronomy education articles littered throughout. There have been frequent significant additions of articles and books from numerous locations over the period as well.It would be extremely difficult to place an estimate on what fraction of the total literature iSTAR now covers if books, theses and grey literature are included. However, we can be cautiously confident that the majority of the mainstream traditional peer reviewed articles in science education and astronomy research journals are now included in the database. In this presentation, we outline the broad statistics, categories and highlights of the astronomy education literature as captured by iSTAR, how iSTAR has provided a significant resource and impact to the astronomy education community as well as present our plans for the future of this database.
Commission C.E2 President's report
Fletcher, Lyndsay
Business Meeting of Div.E and its Commissions, WGs
Magnetized disk models of young circumstellar disks
Flock, Mario
In this talk I will present our recent magnetized models of young protoplanetary disks (based on our recent work Flock et al. 2017a and Flock et al. 2015). The simulation results allow us to search for observational constraints which can be directly compared with our recent simulations. For this talk I will focus on two aspects: first we post-process our models to search for the polarization signature by magnetically aligned dust grains. Our results show a clear radial polarization pattern for face-on observed disk systems due to the dominant toroidal magnetic field, shown in the mm continuum emission by the dust.The second one is caused by the activity of the magnetic dynamo caused by the magneto rotational instability. This causes a clear variability pattern emitted at the dust inner rim surface which could be observed with near infrared light curve observations.
3D radiation MHD simulations of gas and dust in protoplanetary disks
Flock, Mario
I will present recent results from 3D global radiation MHD simulations of gas and dust in protoplanetary disks. From our recent simulation results (Flock et al. 2015 and Flock et al. 2017) we are able to compare for the first time detailed observational constraints from high-resolution observations by ALMA with the gas and dust dynamics obtain in 3D state-of-art simulations of protoplanetary disks. For this talk I will focus on measurements of the dust scale height obtain from the disk around the young system HL Tau. We compared best fit Monte Carlo radiation transfer models of the dusty disk to our results of the dust scale height in 3D radiation MHD and HD simulations. Our findings are that magnetized models fit perfectly the observational constraints, both showing a strongly settled disk, while hydrodynamical turbulence leads to a dust uplifting which is much stronger than expected.This works opens a new window to compare future multi-wavelength observations to simulations.
Metallicity gradients in M31, M33, NGC 300, and Milky Way using Argon abundances.
Flores Duran, Sheila Nathanya
It has recently been shown that oxygen in Planetary Nebulae (PNe) may be enriched in low-metallicity environments (Peña et al. 2007; Flores-Durán et al. 2017) and also in Galactic planetary nebulae with carbon-rich dust (Delgado-Inglada et al. 2015). Therefore metallicity gradients derived from oxygen abundances in PNe could be modified by stellar nucleosynthesis and then this gradient is not adequated to analyse the chemical evolution of galaxies. Apparently neon abundances are also modified by stellar nucleosynthesis (Karakas 2010) but argon abundandances in PNe are not modified in such processes during the PNe progenitor lifetime. Hence we propose to use argon to trace the metallicity gradients in the galaxies of the local universe M31, M33, NGC 300, and the Milky Way. We will show the PNe argon gradients in comparison with H II regions.ReferencesDelgado-Inglada, G., Rodríguez, M., Peimbert, M., Stasinska, G. & Morisset, C.2015, MNRAS, 449, 1797Flores-Durán, S. N., Peña, & Ruiz, M. 2017, A&A, 601, 147Karakas, A. I. 2010, MNRAS, 403, 1413Peña, M., Stasinska, G., & Richer, M. G. 2007, A&A, 476, 745
Is the redshift evolution of HMXBs driven by metallicity?
Fornasini, Francesca
In nearby galaxies, it is observed that the integrated X-ray luminosity (LX) of HMXB populations is correlated with the host galaxy’s star formation rate (SFR) due to the fact that HMXBs form shortly (~10 Myr) after an episode of star formation. Recent X-ray studies of high-redshift galaxies indicate a positive evolution of this correlation with redshift. The higher LX/SFR of HMXBs at high redshift has been attributed to the formation of more luminous HMXB populations in lower metallicity (Z) environments, a trend predicted by population synthesis models. While there is observational evidence that HMXB populations in nearby low-Z dwarf galaxies have enhanced LX/SFR, the correlation between LX, SFR, and Z is still poorly constrained and it remains to be proven that the redshift evolution of LX/SFR is driven by the Z-dependence of HMXBs. Better constraints on the variations of HMXB luminosity with Z and redshift will improve our understanding of the likelihood that HMXBs in low-Z environments are progenitors of the heavy BH binaries discovered by GW observatories and of the contribution of HMXBs to the X-ray heating of intergalactic gas during the Epoch of Reionization. We present the results of an X-ray stacking study of 120,000 star-forming galaxies between 0.1<z<5.0 in="" the="" chandra="" cosmos="" legacy="" survey. comparing="" stacks="" to="" previous="" relations,="" we="" find="" that="" redshift="" evolution="" of="" lx="" sfr="" hmxbs="" is="" weaker. we="" also="" present="" preliminary="" results="" about="" z-dependence="" at="" different="" redshifts="" based="" on="" x-ray="" stacking="" archival="" data="" and="" oxygen="" abundance="" measurements="" from="" sdss="" z~0.3,="" zcosmos="" z~0.7,="" mosdef="" survey="" z~2. these="" studies="" will="" provide="" first="" direct="" tests="" connection="" between="" hmxbs.<="" p="">
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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._x000D_ 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.
Experiences and lessons learnt from the "Columba-Hypatia: Astronomy for Peace" project
Fragkoudi, Francesca
“Columba-Hypatia: Astronomy for Peace” is a joint astronomy outreach project by GalileoMobile and the Association for Historical Dialogue and Research (AHDR) which took place on the divided island of Cyprus over the course of 2017. The project aims to inspire young people, through astronomy, to be curious about the world we live in, about science and the cosmos, while also using astronomy as a tool for promoting meaningful communication and a Culture of Peace and Non-violence. The goal of the project has been to bring together the various communities of Cyprus “under the same sky” to look beyond borders and inspire a sense of global citizenship by promoting cultural exchange. To this aim, we conducted "bi-communal" educational astronomy activities in schools, as well as astronomy nights and events for the general public. We will share our experiences of what we learnt from using astronomy as a tool for promoting peace and co-existence in a conflict region, as well as some of the difficulties and challenges we faced.
What the Milky Way bulge reveals about the initial metallicity gradients in the disc
Fragkoudi, Francesca
We explore the origin of metallicity gradients in the Milky Way (MW) bulge with two N-body models of disc galaxies which form a bar and a boxy/peanut (b/p) bulge, and compare their predictions to APOGEE data. The first model is a composite disc, made up of thin and thick disc stellar populations, where the metal-poor and alpha-enhanced thick disc populations contribute significantly to the inner disc stellar mass budget. The second model is a single disc with an initial steep radial metallicity gradient. While the latter model reproduces the vertical metallicity gradient seen in the MW bulge, it does not reproduce other observed trends in metallicity, as seen with APOGEE data. On the other hand, the composite disc model naturally reproduces all the observed trends. We therefore see that it is possible to reconcile a (primarily) disc origin of the MW bulge with the observed trends in metallicity of the inner MW. These findings also point to an almost flat radial metallicity gradient in the inner disc of the MW, before bar and b/p bulge formation.
Common evolutionary threads between low-mass X-ray binaries and merging binary compact objects
Fragos, Tassos
The recent detection of gravitational waves from coalescing binary black holes by LIGO allowed for the first time the direct observation of stellar-mass black holes, while the simultaneous gravitational wave and electromagnetic signal from the merger of two neutron stars provided the first direct evidence for origin of short gamma-ray bursts. These gravitational wave events, complemented by a half-a-century-long history of indirect observations of accreting compact objects in X-ray binaries, can give us now a more complete picture of the formation and evolution of binary stellar systems containing compact objects. Low-mass X-ray binaries, despite having companion stars with masses too low to form a second compact object, have formation pathways that present many similarities with at least some of the proposed formation channels for merging double compact object, i.e. the isolated, common-envelope formation channel. In fact, the main uncertainties in the formation pathways for both types of systems are the same, namely the occurrence of natal kicks during the core-collapse phase leading to compact-object formation, the angular momentum content of the formed compact object and the phase of dynamically unstable mass-transfer also known as common envelope. In this talk, after briefly reviewing our current understanding of the evolutionary channels leading to the two types of compact object binaries, I will discuss what we can learn from studying these uncertain physical processes in the formation of low-mass X-ray binaries, especially the ones with a black hole accretor, and how we can transfer this knowledge to better understand the formation of double compact objects. Finally, I will present an outlook of how we can improve, in the near future, our understanding in all these fronts.
Accretion physics and scaling laws of angular momentum in galaxies
Fraternali, Filippo
Star-forming galaxies must grow via continuous gas accretion from the surrounding environment. A key property of the accreting gas is its specific angular momentum, which plays a key role in determining the size of the final stellar disc. In this talk, I will present simple models of disc galaxy evolution, including chemical evolution, that help constraining the properties of the accreting gas. The comparison of these models with observations shows that: 1) disc galaxies grow in size today at a rate that is one third of their mass growth rate, 2) the accreting gas must rotate with a deficit of few tens of percent with respect to the disc rotation, 3) a nearly-isothermal hot corona can provide the accretion needed for the inside-out growth of galaxy discs. A relation that captures the properties of the accreting gas in connection with star formation and feedback is the stellar specific-angular-momentum vs mass relation. I will present a new determination of this relation extending to very low stellar masses and discuss its implications for disc evolution models.
3D-modelling of AGB stars
Freytag, Bernd
Local three-dimensional radiation-hydrodynamics simulations of patches of the surfaces of solar-type stars, that are governed by small-scale granular convection, have helped analyzing and interpreting observations for decades. These models contributed a lot to the understanding of the atmospheres and indirectly also of the interiors and the active layers above the surface of these stars. Of great help was of course the availability of a close-by prototype of these stars -- the sun. In the case of an AGB star, the convective cells have sizes comparable to the radius of the giant. Therefore, the extensions of the solar-type-star simulations to AGB stars have to be global and cover the entire object, including a large part of the convection zone, the molecule-formation layers in the inner atmosphere,_x000D_ and the dust-formation region in the outer atmosphere. I will present a new generation of CO5BOLD simulations and show how the interplay of large and small convection cells, waves, pulsations, and shocks, but also molecular and dust opacities of AGB stars create conditions very different from those in the solar atmosphere.
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.
Dwarf Galaxies and the Most Energetic Stellar Explosions
Fruchter, Andrew
Long-duration gamma-ray bursts (LGRBs) and hydrogen poor superluminous supernovae (SLSNe) are found preferentially in dwarf galaxies. However, that preference is even more extreme than it at first seems. We find that LGRBs and SLSNe form about thirty times more frequently per unit of star formation below a metallicity of 1/3 solar than above, with the relative rate increasing to about a factor of one hundred between 1/3 solar and solar metallicity. At the same time GRBs and even more strongly SLSNe are found in hosts with very high emission line equivalent widths. Indeed, the only sample of galaxies known to resemble the emission line properties of nearby SLSNe hosts is an artificial sample of galaxies formed by selecting galaxies with [OIII] equivalent widths above 100 A. Interestingly, the only known fast radio burst host is a dwarf galaxy with a spectrum identical to that of a SLSN host. These results, along with further observations that will be discussed in the talk, imply that an extreme subset of star-forming galaxies are particularly efficient at forming compact stellar remnants with high angular momentum, and indeed dominate the production of these objects in the universe.
Orbital period and pulsed spectrum of the super-Eddington neutron star NGC 7793 P13
Fuerst, Felix
Ultra-luminous X-ray pulsars (ULPs) are a recently discovered class of neutron stars accreting orders of magnitude above their Eddington limit. Currently only about 5 of these systems have been identified, either through the discovery of pulsations or cyclotron resonant scattering features. Their distance, large extinction, and source confusion makes detailed observations challenging. An exception is NGC 7793 P13 which shows a high X-ray flux and a clearly identified optical companion, a B9I supergiant. Furthermore, the pulsations with a period around 415ms have been detected in all X-ray observations so far, allowing us to study the long-term spin evolution. I will also present timing and spectral analysis of a recent XMM and NuSTAR campaign. Through X-ray timing, we can unambiguously measure the orbital period to be ~64d based. This period is consistent with the optical photometric period, but significantly shorter than the periodicity of the X-ray flux (P_X ~ 66.5d). I will discuss possible explanations for this difference, like a very long super-orbital period. The spectral analysis reveals two components, the harder of which we identify with the emission from the accretion column. I will compare the timing and spectral properties of P13 with Galactic HMXBs and discuss what properties of the compact object are necessary to form an ultra-luminous pulsar.
Short-lived radioisotopes in meteorites from Galactic-scale correlated star formation
Fujimoto, Yusuke
Meteoritic evidence shows that the Solar system at birth contained significant quantities of short-lived radioisotopes (SLRs) such as 60Fe (with a half-life of 2.6 Myr) and 26Al (with a half-life of 0.7 Myr) produced in supernova explosions and in the Wolf-Rayet winds that precede them. Proposed explanations for the high SLR abundance include formation of the Sun in a supernova-triggered collapse or in a giant molecular cloud (GMC) that was massive enough to survive multiple supernovae (SNe) and confine their ejecta. However, the former scenario is possible only if the Sun is a rare outlier among massive stars, while the latter appears to be inconsistent with the observation that 26Al is distributed with a scale height significantly larger than GMCs. We present a high-resolution chemo-hydrodynamical simulation of the entire Milky Way Galaxy, including stochastic star formation, HII regions, SNe, and element injection, that allows us to measure for the distribution of 60Fe/56Fe and 26Al/27Al ratios over all stars in the Galaxy. We show that the Solar System's abundance ratios are well within the normal range, but that SLRs originate neither from triggering nor from confinement in long-lived clouds as previously conjectured. Instead, we find that SLRs are abundant in newborn stars because star formation is correlated on galactic scales, so that ejecta preferentially enrich atomic gas that will subsequently be accreted onto existing GMCs or will form new ones. Thus new generations of stars preferentially form in patches of the Galaxy contaminated by previous generations of stellar winds and supernovae.
Discovery of stars with the perfect black body spectrum and their use for calibrations
Fukugita, Masataka
We discovered 17 stars that exhibit the spectrum ofnearly perfect black-body radiation to the accuracy of 1\% level.We found that these stars are DB white dwarfswith temperature 7000K to 12000K, too low to develophelium absorption features, as confirmed withexplicitly constructing atmospheremodels with predominantly helium. These stars can beused to examine the accuracy of the AB magnitudesystem across various wavelength passbands. We foundthat the SDSS magnitude system provides an accuratephotometric standard from the u to the z band, whenthe original zero points are adopted without adding anyoffset constants, which would in turn make the systemtilted.
Numerical integration of gravitational field for general three-dimensional objects and its application to gravitational study of grand design spiral arm structure
Fukushima, Toshio
In order to construct a realistic rotation curve of Milky Way theoretically, we present a novel method to integrate the gravitational field for general three-dimensional objects (Fukushima 2016, MNRAS, 463:1500). By adopting the spherical polar coordinates centered at the evaluation point as the integration variables, we numerically compute the volume integral representation of the gravitational potential and of the acceleration vector. The variable transformation completely removes the algebraic singularities of the original integrals. The comparison with exact solutions reveals around 15 digits accuracy of the new method. Meanwhile, the 6 digit accuracy of the integrated gravitational field is realized by around 10^6 evaluations of the integrand per evaluation point, which costs at most a few seconds at a PC with Intel Core i7-4600U CPU running at 2.10 GHz clock. By using the new method, we show the gravitational field of a grand design spiral arm structure as an example. The computed gravitational field shows not only spiral shaped details but also a global feature composed of a thick oblate spheroid and a thin disc. The developed method is directly applicable to the electromagnetic field computation by means of Coulomb's law, the Biot-Savart law, and their retarded extensions.
First Results from Wide Field Extragalactic Polarisation Surveys
Gaensler, Bryan
Over the last decade, we have extracted substantial amount of information on extragalactic magnetic fields from the NVSS and other archival Faraday rotation data. However, these data sets are inhomogeneous, measured over narrow bandwidths, and do not have well-characterised uncertainties. To move past these limitations, the community has been working toward a suite of new wide-field polarisation surveys, based around high sensitivity, high angular resolution and broad bandwidths. These surveys, which aim to provide more than a million polarisation measurements over the sky, are now finally underway. In this presentation, I will present early polarisation results from POSSUM, VLASS and other wide-field surveys, which showcase the transformational potential of these new programs.
Interstellar dust
Galametz, Maud
TBA
The role of magnetic fields in the early stages of star formation - confronting observations with theoretical expectations
Galametz, Maud
Magnetic fields are believed to redistribute angular momentum efficiently: they could explain the order-of-magnitude difference observed between the large angular momentum of the protostellar envelope and that of a main sequence star. The Class 0 phase is the main accretion phase. If the role of the magnetic fields during that stage is still unclear, they might have a key impact on the evolution of the young star and its surrounding protoplanetary disk._x000D_ In order to study the structure of B from 50 to 2000 AU scales, we have acquired polarization observations of low-mass protostars with the SMA and for one of them, B335, with ALMA. Polarization is detected in all objects. We will present results on the orientation of B with respect to the outflow direction and show that a relation might exist between the misalignment and the rotational energy at the envelope scale. On the small scales traced with ALMA, we detect a large-scale poloidal magnetic field in the outflow direction and a strongly pinched B in the equatorial direction. Our results suggest that the magnetized collapse shows a high level of organization from the 2000 AU down to 50 AU scales._x000D_ MHD simulations can help interpreting the results since we can test different assumptions of the dust alignment mechanisms, projection and instrumental effects. We will present simulations of a gravitational collapse of a magnetized core generated using the RAMSES code. The POLARIS code is used to produce maps of the Stokes parameters for different assumptions on the dust alignment. We will present synthetic observations including instrumental effects directly comparable to our observations._x000D_ Our approach, confronting the most state-of-the-art observations of B to the theoretical expectations of a magnetized star formation scenario ultimately allows us to directly address the phenomenon of magnetic braking during protostar formation and will give key clues on the pristine properties of B fields in star-forming material.
Studying the WHIM through X-ray emission
Galeazzi, Massimiliano
TBA
Living with an Adolescent: The Quasar Phase
Gallagher, Sarah
The centre of every massive galaxy hosts a supermassive black hole that likely grew through accretion as a luminous quasar when the universe was a quarter to a half of its current age. Quasar activity is thus a phase in the evolution of every massive galaxy much like adolescence: transformative (perhaps violently so) though relatively brief. This epoch also coincides roughly with the build-up of stellar mass as a consequence of active star formation. Though these two transformational activities occur close in time and are likely related, their relationship has not been rigourously explored because to date, studying quasar host galaxies at z~2 has proven extremely difficult. The light from the quasar point source swamps the much fainter stellar emission from the host, and the samples of quasar hosts amenable to adaptive optics on 8-m class telescopes are small. Extremely Large Telescopes will break open this field with high resolution imaging and high signal-to-noise spectroscopy of much larger samples of quasar hosts than have been accessible to date. I'll review the overall science cases for the ELTs related to quasars, and offer my subjective view of the most exciting opportunities for major advances in understanding the quasar phase in galaxy evolution.
Connecting the Dots: Stacking the Cosmic Web in Ly a emission with MUSE and EAGLE
Gallego, Sofia
Cosmological simulations suggest that most of the matter in the Universe is distributed along filaments connecting galaxies. Illuminated by the cosmic UV background (UVB), these structures are expected to glow in fluorescent Ly a emission with a surface brightness (SB) that is well below current limits for individual detections.We perform a stacking analysis of the deepest MUSE/VLT data using three-dimensional regions (subcubes) with orientations determined by the position of neighbouring Ly a galaxies at 3 < z < 4. Our method increase the probability of detecting filamentary Ly a emission, provided that these structures are Lyman-limit systems (LLSs). By stacking 390 oriented subcubes we reach a 2s sensitivity level of SB ˜ 0.44 × 10 -20 erg s -1 cm -2 arcsec -2 in an aperture of 1 arcsec 2 × 6.25 Å, three times below the expected fluorescent Ly a signal from the Haardt & Madau (HM) UVB at z ~ 3.5. No detectable emission is found on intergalactic scales, implying that at least two thirds of our subcubes do not contain oriented LLSs. On the other hand, significant emission is detected in the circumgalactic medium (CGM) in the direction of the neighbours. The signal is stronger for galaxies with a larger number of neighbours and appears to be independent of any other galaxy properties. We estimate that preferentially oriented satellite galaxies cannot contribute significantly to this signal, suggesting instead that gas densities in the CGM are typically larger in the direction of neighbouring galaxies on cosmological scales.In addition, we extend our stacking search for IGM filaments with constraints from the EAGLE simulation.
Great historical events of space weather from Spanish documents: a review
Gallego, María Cruz
Northern lights observed from Spain are generally related to great space weather events due to its location in southern Europe. In this contribution, we review the auroras observed from the Iberian Peninsula in the last millennium. Great events of space climate (such as Maunder minimum) are well-characterized in this set of auroral observations. The maximum number of auroral observations occurred in the 18th century when the geomagnetic latitude of the Iberian Peninsula was higher. In fact, we analyze in detail the evolution of the geomagnetic latitude of the Iberian Peninsula during the last centuries. Some cases of interest are analyzed in detail such as the Carrington storm or the 1903 geomagnetic storm (that was the first geomagnetic storm that significantly affected the telegraph in Spain). We also briefly discuss other historical cases of auroras or geomagnetic storms observed in Spanish colonies.
Low-metallicity massive stars: Breaking out of the SMC
Garcia, Miriam
Low-metallicity massive stars hold the key to interpret gravitational waves, high-redshift SNe and long-GRBs, and star-formation through Cosmic history. The massive stars community is working to supersede the SMC as reference for metal-poor massive stars, with new observations and analysis of increasingly metal-poorer Local Group dwarf irregular galaxies. However, these objects are at least 1Mpc away and we are meeting the sensitivity and resolution limits of current facilities. I will present my team's recent results on the topic, how far the immediate-future instrumentation can reach (GTC-MEGARA), and discuss the crucial contribution the E-ELT may make to the field.
Contribution of the Pierre Auger Observatory to the new era in multi-messenger and time-domain astronomy
García, Beatriz
Cosmic rays are atomic nuclei arriving from outer space that reach the highest energies observed in nature. Clues to their origin come from studying the distribution of their arrival directions. To study these “messengers” the Pierre Auger Observatory (PAO) is the largest facility on the Globe, with an extension of 3000 km², 1660 Surface Detectors and 27 Fluorescence Telescopes.During the last year the International Collaboration at PAO produced a series of high impact results in this field of research:1. The Observation of a Large-scale anisotropy in the arrival directions of Cosmic Rays using 3 × 10^4 events with energies above 8 × 10^18 eV from a total exposure of 76,800 km^2 sr year. The anisotropy can be well represented by a dipole with an amplitude of 6.5 (+13/-9) % in the direction of right ascension = 100° ± 10° and declination = –24 (+12/-13) °. The magnitude and direction of the anisotropy support the hypothesis of an extragalactic origin for the highest-energy cosmic rays,rather than sources within the galaxy.2. The multi-messenger observations of a binary neutron star merger, and in particular the search for ultra-high-energy neutrinos above ~ 10^17 eV using PAO Surface Detector.3. The indication of anisotropy in the arrival directions of ultra-highenergy cosmic rays through comparison to the flux pattern of extragalactic gamma-ray sources.In this contribution we will present an overview of these works, which mark a new era in multi-messenger, time-domain astronomy and demonstrate the importance of collaborative gravitational-wave, electromagnetic and neutrino observations.
Development of Astronomy on the Globe: New metrics for impact studies
García, Beatriz
We present a detailed study of the impact of NASE after 8 uninterrupted years of activity in 23 countries, the analysis of the influence of the course not only on the 5000 middle level teachers who have been trained, but also on the members of the IAU involved in the workshops and we give examples of specific activities developed in the classroom, inspired by the NASE proposal.For this study, special metrics were adopted to analyze the effectiveness of the program in a globalized world. The application of these new metrics for the study of proposals, the analysis of expectations and the achievement of results, have allowed us to analyze the activity as a "social business" and quantify its high level of acceptance. In this way, and only as one of the examples to be shown in the framework of the lean metrics, it is possible to design the "traction curves", related to the recurrent or loyal users, which in turn draw on the new ones, allowing the uninterrupted growth of NASE. On the other hand, the implementation of the program of "NASE ambassadors" has allowed the mobility of trainers, both members of the IAU and others promoted and trained by professional astronomers, but from the world of education. This mobility of trainers has been able to establish the links and create the network that, since its inception, pursued the NASE proposal
An overview on radial metallicity gradients with Galactic nebular tracers
García-Rojas, Jorge
I will present a review on the last determinations of radial abundance gradients obtained from the analysis of HII regions and planetary nebulae deep spectrophotometric data in our Galaxy. Comparison between planetary nebulae and HII regions gradients have been usually done as a check of the time evolution of the metallicity gradient. However, I will put the eye on some problems that should be carefully addressed. Additionally, I will not focus only on metallicity indicators (as Oxygen) but also in other interesting elements as Nitrogen, Carbon, and alpha-elements trying to emphasize the importance of precise determinations of the gradients of these elements on the understanding of the nucleosynthetic origin of the elements and on the chemical evolution of our Galaxy.
The Status and Expected Performance of the James Webb Space Telescope
Gardner, Jonathan
The James Webb Space Telescope currently consists of two parts. The Instruments have been integrated onto the telescope, and have successfully undergone a full end-to-end optical cryogenic vacuum test. The spacecraft and sunshield have been integrated together; by the time of the conference they will be completing a suite of acoustic, vibration and vacuum testing. The telescope will be integrated onto the spacecraft and will undergo final observatory-level testing in preparation for launch. I will review the expected performance of the observatory. By the time of the conference, the full Cycle 1 program, including the Early Release Science, Guaranteed Time Observations and General Observer programs are expected to be announced. I will show recent progress and the current status of the observatory and show how you can keep up with progress as the project proceeds to launch, commissioning and scientific operations.
Education and Training in Astrobiology
Gargaud, Muriel
Education and Training in AstrobiologyMuriel Gargaud, Laboratoire d’Astrophysique de Bordeaux,UMR 5804 CNRS-Université de Bordeaux, FranceThe WG “Education and Training in Astrobiology” is an inter-commissions one (C1-F2-F3-H2), created just after the IAU General Assembly in 2015.Its role is to coordinate training, education and outreach activities in astrobiology at the international level by:creating an international network for education and providing training material for basic, secondary and higher education,providing a comprehensive multidisciplinary astrobiology curriculum for undergraduate and graduate students, as well as early career scientists,initiating, coordinating and carrying out initiatives in outreach for the general publictraining the university lecturers (and the high school teachers) in astrobiology (e.g how to teach biology to astronomers or astronomy to biologists, how to evaluate multidisciplinary courses, etc.)During my talk I'll report on the 5 goals we have worked on since 2015 :to collect all lectures and conferences in astrobiology which have been recorded during the last 10 years (whatever the language is), to categorize them according to their field and to make them available for free: astrobiovideo.com/en/to produce handbooks and Massive Open Online Courses (MOOCs) for university studentsto develop outreach for the general public and high school teachersto create an annual international astrobiology training school (TS) on basics in astrobiology : www.exobiologie.fr/red/index.php/en/red16-astrobiology-course/ and to organize several mini-TS, each time this is possible, just before one international conference: ninlil.elte.hu/boa/to organize a regular international workshop on education in astrobiology in order to discuss (especially with C.C1 and C.F3) how to carry out multidisciplinary training in astrobiology and how to share all training materials developed by each country : https://ise2a.uu.nl/
Using High-Mass X-ray Binaries to Probe Massive Binary Evolution
Garofali, Kristen
High-mass X-ray binaries (HMXBs) provide an exciting window into the underlying processes of both binary as well as massive star evolution. Because HMXBs are systems containing a compact object accreting from a high-mass star at close orbital separations they are also likely progenitors of gamma-ray bursts and gravitational wave sources. I will present work on the classification and age measurements of HMXBs in M33 using a combination of deep Chandra X-ray imaging, and archival Hubble Space Telescope data. I am able to constrain the ages of the HMXB candidates by fitting the color-magnitude diagrams of the surrounding stars, which yield the star formation histories of the surrounding region. Unlike the age distributions measured for HMXB populations in the Magellenic Clouds, the age distribution for the HMXB population in M33 contains a number of extremely young (< 5 Myr) sources, including M33 X-7, an eclipsing binary composed of a ~15 Msun black hole accreting from a 70 Msun O star companion. I will discuss these results for M33 in the context of the effect of host galaxy properties on the observed HMXB population.
The Jodrell Bank Telescopes
Garrington, Simon
Since its construction in 1952-57 the Lovell Telescope at Jodrell Bank Observatory has continued to be a major international radio telescope, with important contributions ranging from the discovery of gravitational lensing to timing measurements of pulsars. During the period of the design, construction and early operation of the Lovell Telescope the group at Jodrell Bank also developed and deployed the techniques of long-baseline interferometry to make the first studies of compact radio sources (leading to the discovery of quasars). The Lovell Telescope is a key element of interferometer networks in the UK, Europe and globally. This talk will cover the development of large telescopes at Jodrell Bank as single dishes and in interferometers and the challenges of ensuring that they remain at the forefront of international capabilities individually and in interferometric networks.
Access to astronomy for the visually impaired: responding to the inclusion imperative.
Gastrow, Michael
According to the United Nations ‘Enable’ report, the global proportion of people with disabilities and impairments in the workplace, including in the field of science, is low. The vision now being set forth by the United Nations for the global community is to ‘leave no one behind’. Constraints on the mobility of disabled people into science careers are sub-optimal both for the disabled and for the institutions of science. We therefore propose a research agenda that aims to provide insights into how we can increase interest in science among people with disabilities, as well as increase access, retention, participation, and performance with respect to science learning and science careers. Our proposed case study focus is on visually impaired learners in Cape Town, South Africa. Our objectives are to determine the dynamics of enablers and constraints with regards to access to science faced by people with disabilities. These include, but are not limited to, questions of outreach, didactic issues, preparing to perform in the research field, and possibilities of progress into scientific professions. Suggested research methods include focus groups, semi-structured interviews and empirical measures of performance. The results of this research may inform OAD policies and practices towards the inclusion of people with disabilities and impairments in local and global astronomy institutions.
First and last visibility of the lunar crescent
Gautschy, Rita
The first or last visibility of the lunar crescent is the decisive phenomenon for the start of a new month in various calendars, e.g. the Islamic, Jewish or lunar Egyptian calendar. In order to correctly convert the dates of astronomical observations documented by these cultures into Julian or Gregorian dates, it is necessary to compute the beginnings of the lunar months. Various criteria for the first visibility of the lunar crescent have been proposed based on ancient as well as on modern observational data. For my computations, I use the criterion of Yallop (Yallop 1997) adapted for topocentric calculations. This criterion makes use of the so-called "best time" of observation when the Moon is still some degrees above the horizon – hence, effects of the local horizon can be neglected as long as the horizon is not higher than about three degrees. In the calculations the slowing down of Earth’s rotation is accounted for as well as for standard values of refraction. However, a successful sighting of the lunar crescent is highly dependent on the prevailing seeing conditions: dust in the air or slight fog can easily cause delayed first sightings. Especially in cases where the visibility parameter is close to the critical threshold a lunar crescent may be missed even if the seeing is good._x000D_ I will discuss the uncertainties of the calculations for different periods of time and show how they may be dealt with._x000D_ _x000D_ References_x000D_ B. D. Yallop, A Method for Predicting the First Sighting of the New Crescent Moon, NAO Technical Note No. 69, 1997._x000D_ HMNAO’s Moon Watch web site: astro.ukho.gov.uk/moonwatch/index.html_x000D_ Islamic Crescents’ Observation Project: www.icoproject.org
Optical properties of organic analogs to cosmic dust
Gavilan, Lisseth
Recent work on the spectroscopy of laboratory analogs to cosmic carbonaceous dust found in a variety of astrophysical environments (interstellar, circumstellar and planetary) will be presented. Dust and nanoparticle synthesis methods were used to prepare carbonaceous samples covering a wide range of hydrogenation and sp2 hybridization. Hydrogenated amorphous carbons, analogs to aliphatic interstellar dust, were produced in a low-pressure inductively coupled plasma [1], while polyaromatic soots, analogs to circumstellar dust, were prepared in a combustion flame with varying C/O ratios [2]. The ensuing samples were measured in transmission from the vacuum-ultraviolet to the mid-infrared via a combination of synchrotron and tabletop spectrophotometers. The main electronic and vibrational modes were correlated and optical band gap energies derived. The p-p* band positions and widths were compared to observed interstellar and circumstellar UV extinction. The effects of N and O heteroatoms [3] and low-temperature condensation [4] on the molecular structure and optical properties of organic materials will also be discussed in light of their astrophysical implications.References:[1] Gavilan, L., Alata, I., Le, K.C., Pino, T., Giuliani, A., Dartois, E. A&A 586, A106 (2016)[2] Gavilan, L., Le, K.C., Pino, T., Alata, I., Giuliani, A., Dartois, E. A&A 607, A73 (2017)[3] Gavilan, L., Broch, L., Carrasco, N., Fleury, B., Vettier, L. ApJL 848, L5 (2017)[4] Salama, F., Sciamma-O'Brien E., Contreras C., Bejaoui S. in IAU Proceedings Series, S332 (2018), in press.
Influence of Active Region Inflows in a 3D Babcock-LEighton Solar Dynamo Model
Gebreegzabihar, Kinfe
Solar observations reveal a systematic flow that converges toward photospheric active regions. It has been proposed that this converging flow may act as a saturation mechanism for the Babcock-Leighton mechanism, and as such, may determine the strength of solar cycles. In this work we will address questions such as: Are the converging flows towards active the regions an effective mechanism In 3D Babcock-Leighton solar dynamo model to saturate the dynamo?_x000D_ The inflow towards the active regions is developed on the frame work of Surface flux Transport And Babcock-LEighton Dynamo Model (STABLE), which is a fully 3D hybrid of flux-transport dynamo and surface flux transport model. The STABLE model solves the kinematic magnetohydrodynamics (MHD) induction equation in a 3D, rotating, spherical shell. The induction equation is solved by means of the Anelastic Spherical Harmonic (ASH) code, which currently serves as the dynamical core for the STABLE model. STABLE uses the SpotMaker spot deposition algorithm (instead of α-effect) to place bipolar magnetic regions (BMRs) on the solar surface in response to the dynamo-generated magnetic field. The subsequent evolution of these BMRs due to differential rotation, meridional circulation, converging flows towards the BMRs and turbulent diffusion naturally generates a mean poloidal field as originally described by Babcock (1961) and Leighton (1964). Our STABLE simulations show that inflows converging towards the BMRS significantly affects the build-up of the polar field. To our knowledge this study is the first work that; converging flows towards active regions in 3D Solar dynamo model and results of the model shows that the inflows are a key ingredient in determining the amplitude of solar cycles by providing a nonlinear feedback and mechanism for the saturation of a Babcock-Leighton-type dynamo mechanism.
NICER: Early Operations and First Year Results
Gendreau, Keith
The Neutron Star Interior Composition Explorer (NICER) was launched in June 2017 to the International Space Station (ISS) where it is studying the transient X-ray sky. NICER consists of a collection of X-ray concentrators, silicon drift detectors, an optical bench and pointing system that provides a large collection area in the soft (0.2-12 keV) X-ray bandpass. NICER time stamps individual X-ray photons to an absolute precision of better than 100 nanoseconds while providing moderate CCD like energy resolution. Since installation, NICER has observed over 200 celestial targets including neutron stars and other celestial objects. The primary focus of NICER is to understand neutron star structure, dynamics, and energetics. We will describe the instrument, early operations, and initial results from the first year. In addition, NICER has demonstrated the use of some millisecond pulsars as navigational beacons. NICER will complete its baseline mission in January 2019. Conditional on the status of its baseline science objectives, NICER will be open to a guest observer program with first round proposals due in mid 2018 for observations beginning in 2019.
Accretion and growth of angular momentum in cosmological simulations
Genel, Shy
The role that cosmological simulations play in our pursuit to understand galaxy formation has revolutionized in the past few years with the modern generation of these simulations, and this holds in particular to studies of galaxy angular momentum acquisition and evolution. Large simulated galaxy populations that contain ballpark correct angular momentum facilitate a global description of how angular momentum flows in and out of galaxies, as well as being transported by mutual torques of various galaxy components. However, significant uncertainties persist both due to implementations of sub-grid and feedback models, as well as to the multitude, complexity, and non-linearity of the involved physical processes. In this talk I will review recent work based on cosmological hydrodynamical simulations, and discuss emerging trends regarding the dependence of galaxy angular momentum on dark matter halo properties, merger events, accretion of gas, and feedback.
International School for Young Astronomers (ISYA) since the 60's
Gerbaldi, Michele
The history of the IAU is not simply the story of astronomers working together in a multinational cooperation it is also the history of the internationalization of the astronomy teaching avoiding political interference. During the IAU GA at Hamburg (Germany), in 1964, the foundations for an International School for Young Astronomers (ISYA) were laid, a school dedicated to the students from developing countries. The first one took place in 1967. The context in which the ISYAs developed has changed drastically over the past 50 years. The ISYA started in a period of “mild” Cold War and now we are at the age of the WTO (World Trade Organisation) which shapes the national priorities in term of development in a totally different manner. Besides the ISYA, ideas were blossoming on how to provide contacts between remote places and the main astronomical institutions. Various programmes were created : the Visiting Professors Projects in the 70’s, the Visiting Lecturer Programme in the 80’s and then the Teaching for Astronomy Development (TAD) in the 90’s, all with the aim to increase the cooperation with countries in need of development._x000D_ We will present the main features upon which the ISYAs were established and how they have evolved with an emphasize on the last 10 years. Two more factors have drived its evolution: the VO (Virtual Observatory) which provides an efficient access to world-wide astronomical data and services, and the access to excellent robotic telescopes during the School providing possibilities of direct observations._x000D_ The impact of the ISYA programme will be analyzed through the focus on the ISYA participants : their wishes and their achievements._x000D_ An ISYA is much more than the planning series of lectures: it opens the door to the exchange of ideas across the nation boundaries and not only in the restricted field of astronomy.
Detection of giant planets combining astrometry and radial velocities: the GAIA potential.
Giacobbe, Paolo
The global impact of Gaia micro-arcsecond level astrometric measurements in the astrophysics of planetary systems has been addressed in the past (e.g. Sozzetti 2011). However, those studies only provided general metrics for gauging detectability thresholds. We revisit the topics of planet detection and characterization with Gaia focusing on the sample of nearby low-mass stars. The main thrust of this work is three-fold. _x000D_ First, we gauge the Gaia potential precision astrometry of exoplanets orbiting an actual sample of thousands of known dM stars. We then express Gaia sensitivity thresholds as a function of system parameters and in view of the latest mission profile. _x000D_ The analysis of the simulations results will also provide insight on the capability of high precision astrometry to reconstruct the underlying orbital element distributions and occurrence rates of the planetary companions. These results will help in evaluating the expected Gaia recovery rate of actual planet populations around late-type stars. _x000D_ Second, we investigate some elements of the synergy between the Gaia data on nearby M dwarfs and other ground-based and space-borne programs for planet detection and characterization, with a particular focus on: a) the potential for Gaia to precisely determine the orbital inclination, which might indicate the existence of transiting long period planets; b) the ability of Gaia to accurately predict the ephemerides of (transiting and non-transiting) planets around M stars, and c) its potential to help in the precise determination of the emergent flux, for direct imaging and systematic spectroscopic characterization of their atmospheres with dedicated observatories from the ground and in space. _x000D_ Third, we test a Hybrid Markov Chain Monte Carlo Dierential Evolution approach with the aim of tackling the challenge of combining astrometry and radial velocities of single planetary systems.
Summary From massive stars to HMXBs to GW events
Gies, D.
TBA
Populations of HMXBs in galaxies and links with star formation
Gilfanov, M.
TBA
Plenary Session: ELTs: past, present and future
Gilmozzi, R.
TBA
Welcome – Div.B
Giovannini, G.
Welcome words by G. Giovannini
The role of alumina in triggering stellar outflows
Gobrecht, David
An important dust component in AGB stars is aluminum oxide or alumina (stoichiometric formula Al2O3) showing a spectral emission feature around ~13 µm attributed to Al-O streching and bending modes (Posch et al. 1999, Sloan et al. 2003). Alumina presolar grains are also found in pristine meteorites with typical sizes of a few tens of nm to µms (Stroud et al. 2004). Owing to their refractory nature (thermal stability) and the large abundance of Al- and O-bearing compounds, alumina grains are thought to represent the first condensates to emerge in the atmospheres of AGB stars. In the bulk phase, alumina exists predominantly in two crystalline forms (corundum and clay). The properties of nanoparticles with sizes below ~50 nm, however, differ significantly from bulk properties. Quantum and surface effects of these small particles lead to non-crystalline structures, whose characteristics (geometry, coordination, density, energy) may differ by orders of magnitude, compared to the bulk material. A top-down approach, like classical nucleation theory, is thus not applicable.Therefore, we follow a bottom-up approach, starting with the smallest stoichiometric clusters (Al2O3, Al4O6). Then, we successively build up larger-sized clusters. We present the results of the quantum-mechanical structure calculations of (Al2O3)n clusters with n=1-10, including potential energies, rotational constants, charge distributions and structure-specific infrared spectra (vibrational frequencies and intensities). The vibrational IR spectra can be compared directly with observations and laboratory experiments on meteorites. Moreover, a vibration analysis is required to construct an appropriate partition function (including the vibrational contribution). The latter is needed to accurately compute the thermodynamic potentials (enthalpy, entropy and Gibbs free energy) in circumstellar conditions (p=10-5 - 10 Pa, T=500 - 6000 K) that differ significantly from standard conditions (p=105 Pa, T=298 K).
ON THE ONSET OF DUST FORMATION IN AGB STARS
Gobrecht, David
A promising candidate to initiate dust formation in oxygen-rich AGB stars is alumina (stoichiometric formula Al2O3) showing a spectral emission feature around ~13 µm attributed to Al-O stretching and bending modes (Posch et al. 1999, Sloan et al. 2003)._x000D_ The counterpart to alumina in carbon-rich AGB atmospheres is the highly refractory silicon carbide (SiC) showing a characteristic feature around 11.3 µm (Treffers & Cohen 1974). Both, alumina and SiC presolar grains are found in pristine meteorites with typical sizes of a few tens of nm to µms (Stroud et al. 2004). Owing to their refractory nature (thermal stability) and the large abundances of molecular gas-phase precursors (e.g. AlOH and SiC2), alumina and SiC grains are thought to represent the first condensates to emerge in the atmospheres of AGB stars._x000D_ We follow a bottom-up approach, starting with the smallest stoichiometric clusters (i.e. Al4O6 Si2C2), successively building up larger-sized clusters. We present new results of the quantum-mechanical structure calculations of (Al2O3)n and (SiC)n clusters with n=1-12, including potential energies, rotational constants, charge distributions and structure-specific infrared spectra. The resulting vibrational spectra of the clusters is compared with observations and laboratory experiments. With the help of a vibration analysis we construct an appropriate partition function. With the latter, we evaluate thermodynamic potentials (enthalpy, entropy and Gibbs free energy) of the clusters under circumstellar conditions (p=10-5-10 Pa, T=500-6000 K) that differ significantly from standard conditions in the laboratory (p=105 Pa, T=298 K) and also from bulk potentials. Finally, we compute and present kinetic reaction rates describing growth and destruction of the clusters. The rates are implemented in an extensive chemical-kinetic network that is applied to trajectories describing the pulsation-driven mass loss in AGB circumstellar envelopes.
Temporal Variations of Different Solar Activity Indices and Solar Spectral Irradiance Variability of Some Chromospheric Emission Lines Through the Solar Cycles 21-23
Göker, Ümit Deniz
In this work, a study of variations of solar spectral irradiance (SSI) in the wavelength ranges 121.5 nm-300.5 nm for the period 1981-2009 is presented. In this respect, we revealed negative correlations of intensities of UV (289.5 nm-300.5 nm) spectral lines originating in the solar chromosphere with the ISSN index during the unusually prolonged minimum between the solar activity cycles (SACs) 23 and 24. We also compared our results with the variations of total solar irradiance (TSI), magnetic activity, Ca II K-flux, faculae and plage areas through the connection with the sunspot counts and the number of sunspot groups (SGs). Our results suggest that there is a strong correlation between solar activity indices and the changes in small (A, B, C and H-modified Zurich Classification) and large (D, E and F) SGs. This somewhat unexpected finding suggests that plage regions substantially decreased in spite of the higher number of large SGs in SAC 23 while the Ca II K-flux did not decrease by a large amount nor was it comparable with SAC 22 and relates with C and DEF type SGs. In addition to this, the increase of facular areas which are influenced by large SGs, caused a small percentage decrease in TSI while the decrement of plage areas triggered a higher decrease in the magnetic field flux. From all these results, we found that negative correlations between ISSN and SSI data and the variations between them are in close connection with the classes of sunspots/SGs, faculae and plage regions. Our results thus reveal the potential of such a detailed comparison of the SG analysis with solar activity indices for better understanding and predicting future trends in the SACs.
YORP equilibria: pathways out of YORP cycles
Golubov, Oleksiy
The evolution of small asteroids is governed by the YORP effect, which can include several different varieties: normal YORP (NYORP), tangential YORP (TYORP), and binary YORP (BYORP). The conventional wisdom says that asteroids evolve according to YORP cycles: an asteroid is accelerated by the YORP effect to the disruption limit, forms a binary, then the binary decays, and the asteroid starts a new YORP cycle, with a decreased mass, an altered shape and a small angular momentum. In our talk, we will briefly review this and similar concepts of YORP cycles, describe the general framework in which YORP cycles can be classified, and discuss their generic features. The major part of the talk will be devoted to the ways, in which YORP cycles can be interrupted and YORP evolution of asteroids stopped. Four different mechanisms of such stable equilibria will be considered:1) Equilibrium in NYORP, which can vanish in certain rotation states2) Equilibrium between TYORP and NYORP, which can cancel each other at a certain rotation rate3) For a singly synchronous binary, equilibrium between TYORP, NYORP and tides acting on the primary, and between BYORP and tides acting on the secondary4) For a doubly synchronous binary, equilibrium between NYORP and BYORPFor all the four kinds of equilibrium, we describe their physics and estimate their probabilities. The total of the probabilities is of the order of 10 percent, implying that each asteroid should be caught into an equilibrium after several YORP cycles. Stable asteroids survive, while unstable ones are disrupted and recreated in YORP cycles, until they perhaps become stable, in a process similar to natural selection. The effect of these equilibria should be to slow down the disruption of asteroids in YORP cycles.Ultimately, we see that the YORP effect can deposit asteroids into such stable equilibria, stopping their net YORP evolution. Thus the YORP effect can check itself and minimize its own importance for asteroids evolution.
Road map, WG activities past and future
Gomez de Castro, Ana I.
During the 2015-2018 triennium, the WG activity has concentrated in two basic areas: identification of the basic needs and development of a road map. WG-UV members have actively participated in the identification of the key science areas requiring access to the UV range. This talk will summarize the activity of the group and the main activity areas currently under evaluation.
Confirming Herschel candidate proto-clusters from CO ALMA/VLA observations
Gómez-Guijarro, Carlos
Wide-field surveys with the Herschel Space Observatory are excellent tools for the identification of rare dusty star-forming galaxies (DSFGs), with the best examples being gravitationally lensed DSFGs and high-redshift z>4 DSFGs. Now, our team has used ALMA 870um continuum imaging to discover that wide-field Herschel surveys can also be used to uncover another class of rare galaxies: blends of multiple DSFGs with pairwise separations that are much smaller than what is found from ALMA follow-up of other single-dish surveys. Theoretical simulations overall fail to reproduce this population of multi-component and small-separation DSFGs, but they do suggest that a portion of the population may be due to line-of-sight projection effects and are not physically related. Investigation of this possibility requires spatially-resolved spectroscopic data. Using ALMA and VLA we have conducted a redshift search for a sample of 3 Herschel candidate proto-clusters successfully detecting CO(3-2) and CO(1-0) and thus being able to confirm that the multiple DSFGs are physically associated.
What do planetary nebula and H II regions reveal about the chemical evolution of nearby dwarf galaxies?
Gonçalves, Denise R.
The local Universe provides an opportunity to study the nearby examples of a wide variety of galaxy types. The nearby galaxies are of paramount importance because of the great detail with which we can resolve their stellar populations. In addition to the early- and late-type spirals, the Local Group contains a great number of dwarf irregulars, ellipticals and spheroidals, for which the spectroscopy of individual stars can be obtained. Thus, the chemical evolution of these galaxies can be traced, with the only need of finding populations spanning a large age range and for which we can accurately derive the composition. Planetary nebulae (PNe) are low- and intermediate-stellar mass remnants (so, of old- and intermediate-ages) for which chemical abundances can be obtained up to 3-4 Mpc. Coupled with H II regions, frequently brighter and much easily detected, which represent young stellar populations, they are among the best tracers of the chemical evolution of nearby galaxies, allowing to draw a chemical time line. Although representing different populations, PNe and H II regions share similar spectroscopic features and therefore can be observed and analysed in the same way. In this review I will discuss the main results for the nearby dwarf galaxies chemistry, as given by these two populations, in terms of constraints to chemical evolution models and the mass-metallicity relation of the local Universe.
From the inner Milky Way to Local Volume galaxies: resolved stellar populations with ELT-HARMONI
Gonzalez, Oscar
I will discuss the predicted performance of the HARMONI spectrograph and the ELT in the context of two specific science cases: resolved stellar populations of Local Volume galaxies and Galactic archaeology in dense environments. We have produced and analysed a set of simulated data-cubes using the HSIM software, mocking observations across the giant elliptical galaxy Centaurus A and in the nuclear bulge of the Milky Way. I will use our results to demonstrate the instrument’s capabilities to perform stellar absorption line spectroscopy in a large number of stars which will allow us to study the detailed kinematics and stellar population characteristics of these dense systems.
Small-JASMINE mission
Gouda, Naoteru
Small-JASMINE is an infrared space astrometry mission which is underway to be launched with a primary mirror aperture of 30-cm, in around 2024. Small-JASMINE will provide pallaxes accurate to ~20 micro-as for stars, brighter than Hw=12.5 mag (Hw-band: 1.1 ~ 1.7 micron) with proper motion precision of ~20 micro-as/yr. This satellite will engage in observations of a limited area around the Galactic nuclear bulge and certain specific astronomical objects. Main scientific significance of Small-JASMINE is clarification of the Galactic nuclear bulge. The Galactic nuclear bulge has a lot of interesting astronomical phenomena and objectives which have never been resolved until now, given as follows: (1) Peculiar kinematics by the inner bar or nuclear stellar disk? (2) Infall of supermassive black holes (>~0.1M solar mass) to the Galactic center? (3) Gas transformation mechanism from the outer bulge to the central region? (3)Formations of young stellar clusters? (4)Existence of higher velocity stars? (5) Amount of massive black holes (~30 solar mass), and so on. Next to this primary objectives, Small-JASMINE will have many other scientific targets selected among proposals submitted for open call program. Small-JASMINE can measure the same target every 100 minutes, so it is useful to resolve phenomena with short periods such as X-ray binaries, extrasolar planetary systems and gravitational lens effects.We have been aiming at the realization of the Small-JASMINE mission as a Medium Class mission executed by JAXA. We should have multiple steps of reviews by JAXA. We 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 in international collaboration with other missions such as Gaia, Theia, GaiaNIR, APOGEE etc.
The OAD and Commission CC1
Govender, Kevin
A significant reason for the establishment of the OAD in the first place was to consolidate and build upon many years of excellent work that was done by the then IAU Commission 46 (the predecessor of Commission C1). An important distinction however, is that the OAD's focus is on development (Sustainable Development Goals) and not on the advancement of the field of astronomy. This presentation will provide an overview of the OAD activities and will attempt to stimulate a discussion as to what we need to do moving forward.
Debiased estimates for near-Earth-object orbit and absolute-magnitude distributions
Granvik, Mikael
The debiased absolute-magnitude and orbit distributions as well as entrance routes or regions (ER) for near-Earth objects (NEOs) provide a fundamental frame of reference for studies of individual NEOs and more complex population-level questions. We present a new four-dimensional model of the NEO population that describes debiased steady-state distributions of semimajor axis, eccentricity, inclination, and absolute magnitude H in the range 17<h<25. the="" modeling="" approach="" improves="" upon="" methodology="" originally="" developed="" by="" bottke="" et="" al.="" (2000,="" science="" 288)="" in="" that="" it="" is,="" for="" example,="" based="" on="" more="" realistic="" orbit="" distributions="" and="" uses="" source-specific="" h="" allow="" a="" power-law="" slope="" varies="" with="" h.="" we="" divide="" main="" asteroid="" belt="" into="" six="" different="" ers:="" ?6,="" 3:1j,="" 5:2j="" 2:1j="" resonance="" complexes="" as="" well="" hungarias="" phocaeas.="" addition="" we="" include="" jupiter-family="" comets="" primary="" cometary="" source="" of="" neos.="" calibrate="" model="" against="" neo="" detections="" catalina="" sky="" surveys'="" stations="" 703="" g96="" during="" 2005–2012="" use="" their="" complementary="" nature="" to="" quantify="" systematic="" effects.="" find="" (fitted)="" have="" significant="" differences,="" although="" most="" them="" show="" minimum="" at="" h~20.="" consequence="" differences="" between="" er-specific="" variations="" in,="" distribution,="" average="" lifetime,="" relative="" contribution="" ers="" function="" important="" are="" ?6 and="" 3:1j="" jfcs="" contributing="" few="" percent="" neos="" average.="" from="" hungaria="" group="" leads="" notable="" changes="" compared="" predictions="" distribution="" lifetime="" predict="" there="" 962+52-56="" (802+48-42 x 103)="" h<17.75="" (h<25)="" these="" numbers="" agreement="" recent="" estimates="" found="" literature.<="" p="">
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Asteroid families formed by tidal destruction of near-Earth asteroids?
Granvik, Mikael
Numerous asteroid families have been identified among main-belt asteroids (MBAs) but none have so far been found among near-Earth asteroids (NEAs; see Schunova et al. 2012, Icarus 220, and references therein). Since a collisional origin for NEA families is unlikely, Schunova et al. (2014, Icarus 238) postulated that tidal disruption during a close planetary encounter (Richardson et al. 1998, Icarus 134) is the primary mechanism that produce NEA families. Schunova et al. (2014) also showed that the decoherence time of tidal disruptions is too short to allow identification of NEA families among the currently known NEAs. However, the increase in the rate of NEA discovery in the future can eventually make it possible to identify NEA families formed in tidal-disruption events. The problem is that we have so far only had very limited and indirect evidence of tidal disruptions actually happening. By comparing predicted distributions of NEA orbits and absolute magnitudes with observations by the CSS during 2005–2012 Figure 1 in Granvik et al. (2016, Nature 530) shows that the model underpredicts the number of NEAs with perihelion distance coinciding with the semimajor axes of Venus and the Earth. A detailed analysis of the orbital and absolute-magnitude distributions of the excess NEAs shows that their characteristics agree with the prediction for tidal disruptions and cannot be explained by selection effects or orbital dynamics (Granvik and Walsh, in preparation). We have thus found the population-level evidence for tidal disruptions that we have lacked so far. It is likely that detailed physical modeling of tidal disruption will allow us to place useful constraints on asteroid interior structure using data from, primarily, ongoing and planned NEA surveys.
Observations of UV contrasts and their impacts on the solar irradiance models
Gravet, Romaric
Understanding solar irradiance variations, in particular in the ultraviolet wavelength range, is essential for climate modelling and for space weather. Solar irradiance models are precious for reconstructing the solar spectral irradiance in the absence of observations or when the latter lack stability. However, they come with their assumptions. Here we aim at constraining these by characterising the UV contrast of solar magnetic features at different wavelengths. We consider solar images taken by the Solar Dynamics Observatory between 2010 and 2016. From these we extract the contrast, which we study as a function of position, magnetic field strength and time. As expected, the contrasts in the UV are stronger than those in the visible but we quantify this for the first time and find that the contrast variations are in agreement with the magnetic flux tube picture. The 160nm and 170nm channels show a very similar behaviour; the contrast at 160nm is higher than the one at 170nm, presumably because of the emission of the CIV line from the transition region. The study of solar structures and their segmentation shows that photometric thresholds, both in visible and UV, are necessary to properly segment solar structures because of the coexistence of both dark and bright structures for the same value of the magnetic field. Some pixels that are classified as quiet-Sun by the SATIRE-S model actually belong to faculae, but they are too few to have a significant impact on irradiance reconstructions. Our results highlight the importance of multi-wavelength observations for better constraining the identification of structures. Distinguishing network and faculae is essential for reconstructing the SSI over long time scale, and taking into account for the dependence of the network's contrast with the magnetic field while other structures have a constant contrast improves the SSI reconstruction. Finally, we find no observational evidence for solar cycle variations in the contrast.
Dwarf Galaxies in the Local Group
Grebel, Eva
The study of Local Group dwarf galaxies is a vibrant, rapidly advancing field. Recent discoveries have vastly increased the number of known Local Group dwarfs. We now know more than one hundred of these objects. Low-surface-brightness dwarf spheroidal (dSph) satellites dominate by far. Some very faint dSphs even appear to be satellites of other dwarfs. The ultra-faint dSph galaxies may be close to the lower mass limit of dark matter halos with star formation. Intriguingly, the new discoveries also include the lowest-mass star-forming dwarf irregulars known so far, probing the conditions for gas retention vs. quenching. Most of the dwarfs seem to have a preferred spatial distribution along a great plane, but recent measurements of proper motions suggest that not all of them are kinematically associated with that plane. Cosmological simulations indicate that while satellite infall along filaments is expected, the apparent association of galaxies with a plane may be in part fortuitous with planes being transitory structures. Regarding simulations, substantial progress has been made in resolving the small-scale challenges of the Lambda CDM model by accounting for baryonic effects, particularly feedback and local and cosmological reionization. Major advances have also been made in characterizing the chemistry of Local Group dwarfs based on spectroscopic studies of individual stars. These reveal enrichment by individual supernova events and help to uncover the early star formation history of low-mass halos. Even very low-mass dwarfs often show sizeable abundance spreads and extended star formation activity prior to quenching. Through comparison with the elemental abundances in Galactic halo stars, these studies impose constraints on the accretion history of our Milky Way. The least luminous, least massive dSphs tend to be also the most dark-matter-dominated objects, making them important test cases for putative carriers of dark matter.
Reports from Commission B7: Protection of Existing and Potential Observatory Sites – 1
Green, Richard
TBA – whole section 2b
The role of angular momentum in central and satellite early-type galaxies
Greene, Jenny
Integral-field units have opened the possibility to measure the degree of rotational support in large samples of early-type galaxies. While we have known for a long time that the degree of rotational support in a galaxy scales with stellar mass, it is now possible to ask whether central and satellite galaxies contain differences in their degree of rotation, relative to each other or as a function of halo mass. Thus far, studies with SAMI, MASSIVE, and MaNGA all agree that at fixed stellar mass, there is no measurable difference in the angular momentum content of galaxies as a function of large-scale environment, in agreement with current cosmological simulations. I discuss prospects to increase the fidelity of the measurements and examine redshift dependence in these relations.
Applying historical observations to study transient phenomena
Griffin, Elizabeth
Astronomy has an enviable wealth of historic observations. Some verge on the archaeological, and bear important information about rare events such as novae and supernovae; many others range up to $\sim$100 years old, and bear unique information about events that will never repeat in detail. Historic data were obtained in analogue formats, and in the present era of born-digital data they are often regarded as hailing from a culture that has historical significance only. That is a serious misrepresentation of the facts: our archives of photographic observations, in particular, are invaluable and irreplaceable resources. The technology change to electronic data was abrupt and in some ways cathartic, but it left most of today's astronomers unable to handle photographic data, let alone to comprehend the feasibility of including such "old-fashioned" technological output in the service of research. What is not widely recognized, or believed, is that any of those photographic observations has the potential to contribute unique and unrepeatable information to {\it present-day} studies of variability in the cosmos. The older the data, the more reliable the base-line against which one can measure new trends, determine orbital parameters, etc. Efforts have been discussed for some time as to how to rescue that vital information from loss as the plates age, or (in some cases) get discarded "for lack of interest". The necessary technology for scanning plates correctly is becoming available, and it is now up to us to find the necessary funding to carry through a major digitizing programme. The talk will outline plans for such a project.
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 memberinstitutions. 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.
Clumpy accretion in high mass X-ray binaries: the showcase Vela X-1
Grinberg, Victoria
The winds that the compact objects in high mass X-ray binaries accrete from are intrinsically highly structured, with colder, denser clumps embedded in tenuous hot gas. Understanding this clumpy winds and their interaction with the compact object is key to understanding the observed X-ray variability of HMXBs.Persistent, bright and eclipsing, the HMXB Vela X-1 offers the best opportunity to study accretion onto a neutron star and to disentangle the complex accretion geometry of these systems. Various lines of research have established the presence of large-scale accretion structures such as accretion and photoionization wakes that lead to highly variable absorption along the ~9-day orbit. However, at orbital phase 0.25, when our line of sight towards the source does not pass through the large-scale accretion structure, we observe strong changes in overall spectral shape on timescales of a few kiloseconds. This spectral variability is, at least in part, caused by changes in absorption and we show that such strongly variable absorption cannot be caused by unperturbed clumpy winds of O/B stars alone. In absorption-resolved high resolution X-ray spectra taken with Chandra-HETGS, we detect line features from high and low ionization species of multiple elements whose strengths and presence depend on the overall level of absorption. These features imply a co-existence of cool and hot gas phases in the system, which we interpret as a highly variable, structured accretion flow close to the compact object such as has been recently seen in simulations of wind accretion in high-mass X-ray binaries. Our results show how indispensable time- and absorption resolved X-ray high resolution spectroscopy observations with today's and future instruments are for understanding the clumpy accretion environment in HMXBs.
Observing Pop. III Stars with HARMONI and the E-ELT
Grisdale, K.
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
A Talk of Ice and Fire: Cold Gas Growth, Survival, and Entrainment in Hot Environments
Gronke, Max
A variety of astrophysical systems are multiphase, and we commonly observe the cold gas moving at high velocities, e.g., in outflows around star-forming galaxies. The usual picture is that this gas has been accelerated by ram pressure forces due to the hot gas. However, reproducing this ubiquitous observation in hydrodynamical simulations has proven to be challenging - simply because the destruction time (equal to the Kevin-Helmholtz timescale) is shorter than the time it takes to entrain the cold gas. In my talk, I will propose a solution to this puzzle, and discuss it in light of different astrophysical phenomena.
Gravitational wave astronomy
Groot, P.
TBA
Evolution of star-forming dwarf galaxies in different environments
Grossi, Marco
The ubiquity of star-forming dwarf galaxies (SFDG) in the local Universe allows us to trace their evolution in all type of environments, from voids to rich clusters. SFDGs in low-density regions are still assembling their mass, they often show peculiar gas morphology and kinematics, likely associated to external gas accretion or minor mergers, and they can experience strong bursts of star formation. The most metal-poor SFDGs are found in the field and they are unique laboratories to investigate the star formation process in the low-metallicity regime, at conditions similar to their high-redshift analogues. On the other hand, SFDGs in intermediate- and high-density environments provide a key to understand the processes that remove their interstellar medium (ISM) and suppress star formation, leading to the different types of gas-poor early-type dwarfs. We review the most recent results on the properties of SFDGs at low and high galaxy densities focusing in particular on the impact of a cluster environment on their ISM components (dust, molecular, atomic and ionised gas). We compare the population of SFDGs in the nearest rich clusters: Virgo, which is still in the process of assembly, and Fornax, which is more dynamically evolved, more compact and denser. We discuss how the different evolutionary stage of the two structures affects the properties of SFDGs.
Resolved Maps of Star Formation Rate and Efficiency for the GMC Orion A
Großschedl, Josefa Elisabeth
The giant molecular cloud OrionA is the closest massive star forming region to earth and therefore a prime location to study the laws of star formation. In our work we construct resolved maps of star formation rate (SFR) and efficiency (SFE) across the entire GMC OrionA using a Planck/Herschel dust column-density map and a sample of ~3000 YSOs. To this end, we refine previously existing YSO catalogues using a deep NIR ESO-VISTA survey that allows us to rule out false positives from previous samples (e.g. galaxies, cloud edges). Additionally we add ~200 new candidates in the surroundings to get a complete census of the spatial distribution of YSOs in this cloud as compared to the previously analysed region. We find that the spatial distribution of flat-spectrum sources shows a stronger connection to regions of high dust column-density compared to ClassIIs. This suggests that flat-spectrum sources may not be an observational artifact, as often suggested in the literature (e.g. disk inclination effects), and should be considered as a younger evolutionary phase, likely closer to the protostellar phase (Class I). From the resolved SFR and SFE maps of the cloud we find that the SFR varies by a factor of ~10 across the cloud while the instantaneous SFE is about constant (within a factor of two). The increased SFR at the head of the cloud, including the ONC region, could be explained by cloud compression due to external feedback mechanisms (e.g. SNe, local massive stars). Remarkably, the efficiency of converting dense gas into stars seems to be largely independent of external processes and might be an intrinsic property of the star forming gas.
Insight-HXMT Galactic scanning survey
Guan, Ju
The Insight-HXMT telescope launched on June 15 2017 is China's first X-ray astronomy satellite. One of its main scientific goal is to scan the Galactic Plane to find new transient sources and to monitor the known variable sources, and to observe X-ray binaries to study the dynamics and emission mechanism in strong gravitational or magnetic fields. We will detail the scanning strategy，the data processing pipeline and some interesting results in this report.
Plenary Session: Cosmic Pathways to Life: From Interstellar Molecules to the First Traces of Life (Plenary Talk)
Güdel, Manuel
Life on a planet like Earth has its roots in processes starting with the formation of interstellar clouds and first complex molecules. What follows is a sequence of events that are decisive for the success of eventual life formation: - the collapse of clouds to protostars in a cluster environment, - the onset of "chemical factories" inside protostellar disks, - the formation of a planetary system that remains dynamically stable with the right type of planet in the habitable zone, - the transport of sufficient amounts of water to such a planet, - the generation of a solid surface and an habitable atmosphere, - a clement interaction with the young host star, - the favorable formation of biomolecules on the planetary surface, - and eventually the steps to metabolism and reproduction of initial life forms.Many of these steps are still poorly understood and some of them appear unlikely, but recent research in this widely interdisciplinary field has provided surprising insights into the complex conditions for life. We present research highlights from a tale of several 100 million years of cosmic evolution from the interstellar medium to first life forms on a planet, emphasizing the sequence of critical events that must all succeed for life to emerge.
Archaeoastronomy for the Future
Gullberg, Steven
An update regarding world archaeoastronomy. Featured are its current state of development and a report on the IAU Working Group for Archaeoastronomy and Astronomy in Culture, including its direction and plans for influencing the future evolution of this expanding interdisciplinary field that is anchored astronomically.
Missing baryons and the warm-hot circumgalactic medium of a late type galaxy NGC3221
Gupta, Anjali
Late-type galaxies are missing a large fraction of their baryonic mass, some of which is expected to be in the hot gaseous halo. However, searches of emission from such circumgalactic medium (CGM) have given mixed results. Theoretical models suggest that CGM properties depend on galaxy properties such as gravitational mass, stellar mass and specific star formation rate (sSFR). X-ray observations so far have focused on galaxies with high mass and low sSFR. NGC3221 has smaller stellar mass and higher sSFR, probing an unexplored parameter space. I will present our Suzaku and Chandra observations of NGC3221 and discuss our results on the detection and characterization of its warm-hot CGM.
Detecting Galactic halo planetary nebulae and symbiotic stars in multi-band photometric surveys
Gutiérrez Soto, Luis Angel
About 3,000 planetary nebulae (PNe) and 251 symbiotic stars (SySts) are known in our galaxy. From them, only 14 PNe and around 5% of SySts are located in the Galactic halo or in high latitudes.In this contribution, we present the preliminary results of a research to identify halo PNe and SySts in the direction of halo, by using the Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS), the Javalambre-Photometric Local Universe Survey (J-PLUS) and the Southern Photometric Local Universe Survey (S-PLUS). The main advantage of these surveys is their great combination of narrow- and broad-band filters from 3,000-10,000 Å, in total 56, 12, and 12, respectively. The optical spectra of several types of sources as well as a grid of photoionization models, convolved to the photometric systems of the three surveys, are used to generate combinations of colour-colour diagrams that discriminate halo PNe and SySts from other emission line objects (star-forming galaxies, QSOs, cataclysmic variables, extragalactic H II regions, young stellar objects (YSOs), Be stars, among others). The J-PLUS science verification data of two known halo PNe (H 1-4 and PNG 135.9+55.9) are found to located close to the region of halo PNe. New halo PNe and SySts candidates, selected in the J-PLUS Early Data Release, will be discussed in this contribution.
Populations of HMXBs in the Milky Way and the Magellanic Clouds
Haberl, Frank
The study of X-ray source populations in nearby galaxies is of major importance in understanding the X-ray output of more distant galaxies as well as learning about processes that occur on interstellar scales within our own Galaxy. In comparison with the Milky Way, the Small Magellanic Cloud harbours an extraordinary large and different population of high mass X-ray binaries (HMXBs). A most recent compilation identified about 120 HMXBs with Be-type companion star, while only one supergiant system is known. Correlations with the star formation history suggest that this is caused by a star formation event about 40 My ago. The large sample allows to investigate various statistical properties and to find interesting individual cases. In this talk I'll focus on the X-ray properties of the HMXB populations in the Magellanic Clouds in comparison to the Milky Way.
ALMA observations of the Orion Integral Filament: evidence for fibers in a massive cloud
Hacar, Alvaro
We have investigated the dense gas substructure of the Integral Shape Filament (ISF) in Orion combining ALMA and single-dish observations down to resolutions of 0.009pc. Our analysis of the gas kinematics demonstrates that this massive filaments is actually a collection of 55 dense fibers forming a complex bundle with multiple hub-like associations. The ISF fibers show transonic internal motions respect their local sound speed, lengths of ~0.15 pc, and a mass distribution consistent with hydrostatic equilibrium. Within this complex network, the ISF fibers show a compact radial emission profile with a median FWHM of 0.035 pc systematically narrower than the previously proposed universal 0.1 pc filament width. Our new ALMA observations suggest strong similarities between the internal substructure of this massive filament and previously studied lower-mass objects. The fibers show identical dynamic properties in both low- and high-mass regions, and their widespread detection in nearby clouds suggests a preferred organizational mechanism of gas in which the physical fiber dimensions (width and length) are self-regulated depending on their intrinsic gas density. Combining these results with previous works in Musca, Taurus, and Perseus, we identify a systematic increase of the surface density of fibers as a function of the total mass per-unit-length in filamentary clouds. Based on this empirical correlation, during my talk I will discuss a possible unified star-formation scenario where the observed differences between low- and high-mass clouds, and the origin of clusters, emerge naturally from the initial concentration of fibers._x000D_ Referenece: Hacar et al 2018, arXiv:1801.01500v1 _x000D_ See also: ORION-4D project website
Contribution of the International Science Community to the Sustainable Development Goals
Hackmann, Heide
The international scientific community is responding on many fronts that are of importance to the Sustainable Development Goals (SDGs). Effective coordination of these efforts and facilitation of pathways to global policy frameworks and process is vital if science is to maximise its contribution Agenda 2030. ICSU plays an important role in representing the international scientific community, in mobilising its potential, initiating and supporting relevant research programmes, and in shaping coherent responses from funders. It provides direct input to international efforts to sketch the landscape of challenges, opportunities and pathways to achievement. It also plays a major role in challenging the community to collaborate across the disciplines and to engage with societal stakeholders in order to create the actionable knowledge that society needs to address global problems. An overview of the various ways in which the international scientific community is supporting the achievement of the SDGs serves also to highlight critical challenges and opportunities, and the role of the new International Science Council in addressing these.
Existence, Frequency and Detectability of Inclined and Non-Transiting Circumbinary Planets
Haghighipour, Nader
The success of the Kepler space telescope in detecting planets in circumbinary orbits strongly indicates that planet formation around binary stars is robust and planets of a variety of sizes and orbital configurations may exist in such dynamically complex environments. A survey of the currently known circumbinary planets (CBPs) indicates that the orbits of many of these objects are slightly inclined and they precess with rates that place them out of transit for the majority of time. The latter strongly suggests that inclined and non-transiting CBPs are very common and the reason that not many of them have been detected is that they did not transit during the primary mission of the Kepler telescope. This has raised several fundamental questions on the formation, orbital evolution, long-term stability, and ultimately, the detectability of inclined and non-transiting CBPs. We have addressed these questions by carrying out a comprehensive 3D study of the post-formation evolution of CBPs and a detailed analysis of the orbital dynamics of these objects for a large range of their orbital inclinations. We have determined the frequency of transiting and non-transiting CBPs for different values of the binary orbital parameters and mass-ratios as well as the orbital inclination of the planet. Results indicate that, consistent with observational results, majority of CBPs are on inclined, and even non-transiting orbits, and that these orbits are the natural consequence of the post-formation evolution of these objects. We have derived, for the first time, empirical formulae for calculating the locations of (3D) boundaries of stability for inclined CBPs, and examined the possibility of the pile up of CBPs near these (3D) stability boundaries. We have found that no such preference exists. We present results of our study and discuss their implications for the probability of detection of inclined and non-transiting CBPs in terms of their orbital inclinations.
Massive binary stars with relativistic companions: Studying donor winds with the HST
Hainich, Rainer
High-mass X-ray binaries (HMXBs) are unique massive star laboratories. These objects represent an advanced stage in the evolution of massive binary systems, after the initially more massive star has already collapsed in a supernova explosion, but its remnant, a neutron star or a black hole, remains gravitationally bound to the system. In the so-called wind-fed HMXBs, the stellar wind from the OB-type donor is partially accreted onto its compact companion, powering its high X-ray luminosity. Recently, the number of known Galactic wind-fed HMXBs was more than doubled by the unexpected discovery of a new type of objects: the supergiant fast X-ray transients with OB supergiant donors. It was suggested that the physics of these objects is governed by their donor's stellar winds. To correctly model the populations of relativistic binaries in galaxies, it is imperative to understand the reasons for the existence of different types of HMXBs with OB-type donors. But, up to now, only a few donor stars were analyzed by means of sophisticated stellar atmosphere models. Therefore, using the HST we performed a UV spectroscopic survey of donor stars, covering both the newly discovered as well as the classical HMXB systems. The UV spectra were complemented by optical and simultaneously obtained X-ray data. The analysis was performed using PoWR non-LTE stellar atmospheres. In this talk, I will present results of this survey, including an up-to-date overview of our knowledge about OB supergiant donors with relativistic companions.
The future of UNESCO and Intangible Astronomical Heritage
Hamacher, Duane
UNESCO has made significant strides in recent years to protect tangible cultural heritage. Expanding beyond this is a growing movement to protect cultural heritage that is intangible, such as "the practices, expressions, knowledge and skills that communities, groups and sometimes individuals recognised as part of their cultural heritage." This involves understanding the connections between astronomical knowledge, practices, and technologies and how they relate to oral tradition, performing arts, social practices, rituals and festive events, and traditional craftsmanship. In this paper, we explore the concept of intangible astronomical heritage, the various challenges faced when trying to identify, preserve and protect IACH, what changes need to be made to decolonise and challenge Western approaches for assessing tangible World Heritage cites, and and how to move forward in close collaboration with the relevant communities that maintain ownership or custodianship of IACH.
Transient astronomical phenomena in Australian Indigenous oral traditions: 65,000 years of oral history
Hamacher, Duane
Descriptions of transient phenomena are commonplace in the oral traditions of Indigenous cultures around the globe, particularly Australia. These traditions describe bright meteors, airbursts, haloes, eclipses, aurorae, variable stars, comets, and other related phenomena. Specifically, Aboriginal Australians have detailed oral traditions about different types of variable stars: including descriptions about the sudden appearance, and gradual fading, of bright new stars in the sky, suggesting observations of novae/supernovae. In the 1840s, Aboriginal people in western Victoria observed the Great Eruption of Eta Carinae and incorporated the event in to their traditions. Similarly, Aboriginal communities in southern Australia describe the variability of the pulsating red giants Antares, Betelgeuse, and Aldebaran. This paper will address Indigenous oral and historical records of variable star phenomena in Australia. We will explore how observations of these phenomena are described in oral tradition, including changes in brightness and periodicity, as well as testing claims of supernovae in oral and material culture. We will explore methodologies for identifying these objects and examine ethnographic and ethnohistoric research, how Western science can learn from these traditions, and how this knowledge can be shared by Indigenous elders and applied to the new era of Terra-Astronomy.
Exploring the Solar System with JWST
Hammel, Heidi
JWST’s instruments, along with the telescope’s moving target capabilities, will enable unique and powerful infrared studies of solar system objects. This presentation features highlights of the Solar System guaranteed time observations (GTO), which are also described by Milam et al. 2016 (PASP 128, 959, and references therein). The Solar System GTO program includes observations of Mars, near-Earth objects, asteroids, Jupiter, Saturn as well as its rings and small satellites, Uranus, Neptune, Titan, Europa, Enceladus, several comets, and some transneptunian objects (TNOs). With the exception of the TNO observations, these observations have zero proprietary time, and thus will be immediately available to the community. They will also be available for analysis in the archival research (AR) program in Cycle 1 (the AR program offers support to US investigators for the analysis and interpretation of the Early Release Science programs and these non-proprietary GTO programs to enhance the science return of these datasets). The Solar System GTO program was always planned to enable JWST use by the broad solar system community, so by releasing these data to the community immediately -- as well as having funding opportunities available – we hope to help our colleagues pursue a diverse and comprehensive planetary science program with JWST in future cycles.
MOSAIC at the ELT: A Gigantic Step into the Deep Universe
Hammer, Francois
Combined with the unprecedented sensitivity of the E-ELT, MOSAIC will be the most efficient MOS facility having both multiplex and multi-IFU capability. MOSAIC at E-ELT will be unique for follow-up the faintest sources detected by JWST, to probe the reionisation epoch at very high redshifts as well as to evaluate the evolution of the dwarf mass function over most of the Universe age. With its IFUs, MOSAIC will be without competitors for probing an inventory of both dark matter (from realistic rotation curves at early epochs) and cool to warm-hot gas phases in z=3.5 galactic haloes. Galactic archeology as well as evolution of first massive black holes are also targets for which the MOS will be unique._x000D_ Multi-object adaptive optics and accurate sky subtraction with fibers have been demonstrated on sky. A large consortium has been gathered to support the MOS implementation on the ELT.
Radio AGN in LOFAR surveys -- large samples at last!
Hardcastle, Martin
The LOFAR Tier-1 survey of the Northern sky (LoTSS) is the first large-area survey to simultaneously have the long baselines to detect extended emission from radio-loud AGN and the resolution to identify them with host galaxies -- we can select, image and identify objects in a single survey -- and is ten times deeper than any existing large-area survey. As such it will provide samples larger by many orders of magnitude than what we have at present. I will present results from the first data release of LoTSS, including a robustly selected AGN sample, constraints on the local jet kinetic luminosity function and studies of rare subclasses of objects such as restarting sources and giants.
The LUVOIR project. Facilities, Technologies and Data Science. A review on the technological requirements and the associated facilities.
Harris, Walt
TBA
Ultraluminous Pulsars: Extremes of Accretion
Harrison, Fiona
Ultraluminous X-ray sources (ULXs) are binary systems in nearby galaxies with luminosities between 10^39 - 10^41 erg/s, or between ten to one thousand times the Eddington luminosity for a stellar mass compact object. Long thought to harbor black hole accretors with masses between 10 - 1000 times the mass of the Sun, the discovery of three ultraluminos pulsars powered by accretion onto a neutron star presents many theoretical challengs. I will present an overview of observations of pulsating ULXs, concentrating on the characteristics that successful theories must explain. I will also summarize the range of theories proposed to explain the extreme observed luminosities.
Keynote – FM11
Hasinger, Guenther
TBA
Scaling Historical Space Weather Events: Case Studies of Events in 1859 and 1770
Hayakawa, Hisashi
This presentation aims at providing insights on scaling the historical space weather events before magnetic observations. It is well known that the Carrington event is considered one of the most extreme space weather events in the coverage of magnetic observations. However, this coverage spans no more than 2 centuries and it is not clear if this event is that “extreme” in historical time span. On the other hand, it is known that equatorward boundary of auroral oval has correlation with scale of magnetic storms. Therefore, in this presentation, we review historical records in 1859 and see its relation with magnetic observations (Hayakawa et al., 2016). Then, we apply the same approach to another historical space weather event in 1770. In this presentation, we examine the equatorward extension of auroral visibility, elevation angle of auroral display, and longevity of the low latitude aurorae, to compare this event with the extreme space weather event in 1859 (Hayakawa et al., 2017; Ebihara et al., 2017; Kataoka and Iwahashi, 2017).Ebihara, Y., et al. 2017, Space Weather, 15, 1373Hayakawa, H., et al. 2016, PASJ, 68, 99.Hayakawa, H., et al. 2017, ApJL, 850, L31 Kataoka, R., Iwahashi, K. 2017, Space Weather, 15, 1314
Molecular gas reservoirs of galaxies in a galxy cluser at z=1.46
Hayashi, Masao
We would like to present molecular gas reservoirs of eighteen galaxies associated with one of the distant X-ray galaxy clusters, XMMXCS J2215.9-1738 cluster at z=1.46. Dust continuum emission at 870 micron and CO(2-1) emission line are detected from 8 and 17 member galaxies within a cluster-centric radius of R_200 from the ALMA data. This is one of the largest sample of CO detections in such a high-z cluster. The molecular gas masses derived from the CO and/or dust continuum luminosities show that the fraction of molecular gas mass and the depletion time scale for the cluster galaxies are larger than expected from the scaling relations of molecular gas for star-forming galaxies in general fields at similar redshifts. The galaxies closer to the cluster center seem to show a larger deviation from the scaling relations. We speculate that the environment of galaxy cluster helps feed the gas through inflow to the member galaxies and also reduce the efficiency of star formation. On the other hand, there is no galaxy with CO(2-1) detected in the very center of the cluster. The stacked spectrum of 12 quiescent galaxies with M_stellar~1E+11 Msun within 0.5 R_200 shows no detection of CO emission line, giving the upper limit of molecular gas mass and molecular gas fraction to be <1E+10 Msun and <10%, respectively. The phase-space diagram indicates that the gas-rich galaxies have entered the cluster more recently than the gas-poor star-forming galaxies and passive galaxies located in the virialized region of this cluster, however, the massive galaxies in the cluster center must quench the star formation activity while consuming most of the gas reservoirs.
Look Back and Look Forward, the Growth of Astronomy in Japan
Hayashi, Saeko
“What is happening up there? What is the mechanism that governs the formation of stars and planets? I want to study astronomy,” says a girl in a country-side. “by building a large telescope,” she continues. If the first sentence was not a surprise, surely the second one was unheard of half a century ago in a country far far away in the east. Let alone building such a facility outside of the country.Astronomy in Japan has long history and has its own “light.” Proudly I could say the foresight of leaders in early 20-th century helped Japan to be a founding member of the International Astronomical Union. In this presentation, I would like to show the growth in its more recent history with particular emphasis on two important issues: large research facilities and women participation. Ground based or air-/space-born, the large facilities are nowadays outside of the land of Japan, not only in terms of physical presence but also the community they serve. Domestic membership at the same time is expanding thanks to the increased opportunities for women.How do we go further? Make connections amongst people on this planet. What works in the collaboration or inclusion? Think globally (universally) and act locally.Designation of 2009 as the International Year of Astronomy prompted the start-up or scaling-up of many good programs in astronomy outreach, especially in the life-long learnings and informal educations. In the discussion I will focus on two very successful and promising areas I encountered during this decade. Training next generation leaders was one key component for global connections. Whether going abroad or stay in the home country, astronomy researchers cannot stay away from the international collaborations. Starting small and young in their local communities was the other. In this way, the program can stay sustainable. By applying these two strategies in my home country, I hope to promote the progress of astronomy and its relevance in the community.
CB4: New Results in Radio Astronomy - The Power and Promise of 21 cm HI Line Surveys
Haynes, Martha
The 21 cm line of atomic hydrogen (HI) provides a powerful probe of the cool-to-warm interstellar gas in galaxies. Virtually all star-forming galaxies contain a cool neutral component of their interstellar medium, representing the fuel reservoir from which stars may form in the future. In this talk, I will highlight the differences between galaxy populations traced by starlight and by radio HI line surveys, explore what HI reveals about the astrophysical processes at play within galaxies, and discuss the importance of HI-selected samples in contributing to the understanding of apparent conflicts between observation and theory on the abundance of low mass dark matter halos. I will conclude with an overview of the ongoing and planned major HI line surveys that will explore the cosmic evolution of the HI population.
Plenary Session: The Future of Dwarf Galaxy Research: What Telescopes will Discover
Haynes, Martha
Dwarf galaxies make ideal laboratories to test galaxy evolution paradigms and comological models. Within the dwarf rubric, we find star-forming, star-bursting and fully quenched galaxies as well as objects only barely able to hold on to their gas and/or form stars. Detailed studies of dwarfs across the spectrum allow us to gauge the efficacy of astrophysical processes at play in the lowest mass halos such as gas accretion, feedback, turbulence and chemical enrichment. Dwarf galaxies also make excellent targets for direct detection dark matter searches. Future studies will deliver unprecedented insights on the orbits of dwarf companions around the Milky Way, on their star formation histories and on the 3-D internal motions of their stars. Over large volumes, we will assess the impact of local environment on baryon cycling and star formation laws, leading to a full picture of the evolution of dwarfs across cosmic time. In combination, future discoveries promise to trace the history of assembly within the Local Group and beyond, probe how stars form under pristine conditions, and test models of structure formation on small scales.
The Thick Disk of the Milky Way
Haywood, Misha
There is mounting evidence that the formation of the thick disk of the Milky Way was a major phase in the evolution of our Galaxy, increasing its metallicity from below -2 dex to solar, forming half its stellar mass, and setting the initial conditions for the formation of the inner thin disk. I will discuss these results and their implication for the evolution of our Galaxy.
IAU Division C: Education, outreach and heritage - a review of the division's activities 2015-18
Hearnshaw, John
Division C for astronomy education, outreach and heritage is a unique and very special division of the IAU, as we are the only division not to focus on one area of astronomical research. Within our division there is an amazing and diverse range of activities that cover astronomy education, outreach to the public, the history of astronomy, the heritage of astronomy and we collaborate with Division B in the preservation of dark skies for astronomy. Much of the Division’s work is carried out by our Working Groups, and there are 20 of these attached to our four commissions as commission WGs or inter-commission WGs. We also have two divisional (or inter-division) WGs. These cover many aspects of the impact of astronomy on society, including equity, diversity, training of teachers and students, using astronomy as a tool for development, promoting women in astronomy, promoting astronomy to the public, including astro-tourism in dark sky reserves, and protecting the tangible and intangible heritage of astronomy which has resulted from the long history of our science._x000D_ This talk will review all these activities of Division C, especially those that were important for the last triennium, as an introductory talk of the Division Days meeting at the Vienna GA. I will also review some of the routine business of the division, most notably advising the EC on the selection of symposia and focus meetings, and appointing associate IAU members of our WGs, commissions or division. I will also highlight some of the special projects undertaken by the division over the last three years.
Commission 38 (Exchange of astronomers) and Commission 46 (The teaching of astronomy): two commissions that played a unique role in the history and development of the IAU
Hearnshaw, John
I will trace the founding and development of two commissions of the IAU that played a unique role in IAU history. Commission 38 for the Exchange of astronomers was founded in 1946 with Marcel Minnaert as first president, and it expended funds (initially granted by UNESCO) for astronomers to travel on exchange visits. Commission 46 for the Teaching of astronomy was founded in 1964 with Evry Schatzmann as first president. This was a time of rapidly growing interest in the IAU for teaching astronomy and in due course for promoting astronomy in developing countries. For a while, both commissions operated under the wing of the Executive Committee. Their role was unique as they were the only IAU commissions to have their own budget, as well as aspiring to bring about social change in the astronomical community. By 2000 both commissions merged into C46 (Astronomy education and development) and by that time various programs such as the International School for Young Astronomers (ISYA), the working group World-wide development of astronomy (WWDA) and the working group Teaching astronomy for development (TAD), which grew out of the Visiting lecturers’ program (VLP), were all run by C46. When the IAU established the Office of Astronomy for Development in 2011, many of these functions were removed from the commission and in any case C46 ceased to exist in 2012 when all the old commissions were disestablished. In 2015 the Office for Young Astronomers took over the running of the ISYA.The history of C38 and C46 represents a time of active change in the way the IAU was engaging with people. It was more than just a union for scientific research, but in the world of scientific unions, it was remarkable for taking an active hands-on role in implementing social change.In the history of these two commissions, the Swiss astronomer Edith Müller played a leading dynamic role. She served as president of C46 (1967-73), of C38 (1985-88) as well as IAU General Secretary (1976-79).
astroEDU: 5 Years on and the Launch of an Astronomy Education Practitioner Journal
Heenatigala, Thilina
astroEDU was launched in 2013 to be an open-access platform for peer-reviewed astronomy education activities with initial funding from IAU Office of Astronomy for Development. It aims to address key problems in educational repositories such as variability in quality, lack of maintenance and regular updates, limited content review, and more. This is achieved through a peer-review process similar to the process scholarly articles go through. The activity submission workflow allows authors to learn how to apply inquiry-based learning into the activity, identify the process skills required, how to develop goals and objectives, and how to evaluate the activity to determine the outcome.The platform has published 80 peer-reviewed activities as by February 2018 which are pushed further towards four leading educational repositories; OER, Scientix, Guardian Teachers Network, and TES, which helps to reach thousands of teachers. The editorial team has rejected 14 activities due to various reasons such as lack of scientific content, educational implementation, and presenting in astroEDU format. This thorough screening of activities has led to publishing only the highest quality of content. Currently, 51 activities under review. As a volunteer-centered project, astroEDU has a volunteer base of 318 scientists and educators whose major task is to help with the reviewing of the activities.Building on the success of the last 5 years, at the end of 2019, we intend to launch the first issue of a professional journal for astronomy educators, called astroEDU, along with the lines of the CAPjournal for astronomy communications and outreach professionals. The journal is intended to contain a peer review research article section, best practices in astronomy education, innovation and latest trends, reports, peer-reviewed activity, and opinion columns. This presentation will outline the history of astroEDU platform and the aims and scope of the new astroEDU professional journal.
Stellar feedback in dwarf irregular galaxies traced with radio continuum observations
Heesen, Volker
Low mass dwarf irregular galaxies are subject to outflows, in which cosmic rays have since long been suspected to play an important role; they can be traced via their electron component, the cosmic ray electrons (CREs), in the radio continuum as non-thermal synchrotron emission. Thus far, spectral ageing has hampered the study of CREs far away from star formation sites. This is possibly now about to change with the advent of sensitive low-frequency observations such as with the Low-Frequency Aray (LOFAR). 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. Here, we present results from our pilot study of the nearby starburst dwarf irregular galaxy IC 10, using 140-MHz LOFAR and 1.6- and 6.2-GHz VLA observations in order to measure non-thermal radio spectral indices. We show that spectral ageing occurs at two distinct locations over a wide range of frequencies. First, in the non-thermal superbubble, close to a massive HII region with on-going star-formation. With a CRE spectral age of ~1 Myr, this is a high-frequency phenomenon; the bubble is probably the result of a few recent supernovae or one, hypothetical, hypernova. Second, at distances of >0.5 kpc away from the star-forming disc in the halo. This low-frequency radio halo is likely connected to a galactic wind, which has set in during the current starburst, as hinted by the good agreement between the advective time-scale of 30 Myr with the age of the oldest stellar cluster. We discuss the relationship of the non-thermal ingredients of the interstellar medium – magnetic fields and cosmic rays – with other components, such as the warm neutral and warm ionised medium, and place outflows in dwarf galaxies into the context of galactic winds that we also find in more massive Magellanic-type and late-type spiral galaxies.
Plenary Session: Massive Stars
Heger, Alexander
Stars more massive than about eight solar masses run through all exothermic nuclear burning phases and build up a massive iron core in their centre. This core eventually collapses to leave behind a neutron star or black hole as compact remnant. This collapse can drive explosions ranging from some of the most powerful explosions in the universe to quite weak events that are basically just a disappearance of the star. The ejected mass may lead to bright displays we observe as GRBs, hypernovae, or supernovae. Mass outside the core that is not ejected, falls back onto the compact remnant. Both the explosion and the fallback may be asymmetric, imparting angular and linear momentum onto the remnant, even for black holes. In binary star systems, large mass ejection can make the star unbound, whereas kicks may help to ‘repair’ this deficit in some cases, or aid to more and faster ejection. Hence to understand binary star populations, one needs to understand the explosion, and for that, the final state of the star at the time of explosion. This may include interactions the star has had as part of a binary system that affected its evolution and that of its binary star orbital parameters, as well as what the star just does by itself. In particular, the late evolution stages, we assume today, are affected only little by being in a binary, once the helium, or certainly the carbon core size is set. Once carbon burning is reached the remaining lifetime of the star is a thousand years or less.It would be misleading to assume stellar evolution even of single stars was a topic that is mostly set as we have been studying it since decades. In contrast, there is many aspects of massive star evolution that still remain largely elusive, including internal transport processes of composition, angular momentum and energy, mass loss, the final structure of the stars at death, and which stars die what fate. I shall provide a current view of at least a few of these aspects.
The donor stars of ultraluminous X-ray sources
Heida, Marianne
Ultraluminous X-ray sources (ULXs) are the most extreme X-ray binaries in the Universe. As the large majority of ULXs are extragalactic objects and their optical emission is in most cases dominated by the accretion disc, spectroscopic identification of ULX donors is challenging. Many ULXs are believed to have high mass donor stars as they are found in or near star forming regions. This makes them possible progenitors for the black hole mergers discovered by LIGO. To learn where they fit in the picture of massive binary star evolution, knowledge of the donor stars in these systems is crucial. Detecting stellar absorption lines is also necessary to obtain dynamical mass measurements, which is the only direct way to determine the mass of any black hole accretors in ULXs. Of the five ULX donor stars that have been identified spectroscopically, three are red supergiants discovered in our near-IR survey of nearby ULXs. The photometric part of this survey is now finished and our spectroscopic follow-up campaign, to classify the counterparts and monitor the ones that are confirmed to be stellar, is well underway. I will show the latest results of this campaign and discuss the opportunities afforded by upcoming facilities such as JWST and 30-m class telescopes.
The consistency of TRF, CRF and EOP - a VLBI perspective
Heinkelmann, Robert
Currently three realizations of the ITRS, the DTRF2014, ITRF2014, and JTRF2014, are available. Although these frames are based on identical input data, the applied mathematical models and thus some results significantly differ.ICRF3, probably the next realization of the ICRS, is very close to be presented to the IAU General Assembly by the corresponding IAU WG. In the sense of the IUGG Resolution No. 3 (2011), which advocates the consistent determination of CRF, TRF, and EOP (Earth Orientation Parameters), one of the main tasks will be to make sure that the two reference frames, TRF and CRF, and with that the EOP are utmost consistent. VLBI is the space geodetic technique that connects the TRF with the CRF. It is uniquely capable of providing the complete orientational difference, i.e. all five EOP, at once in a consistent manner.In the presentation, we will quantify the orientational differences between the CRF and the TRF through the analysis of data of the IVS archives. The obtained frames and EOP will in turn be compared to the current conventional products: ICRF2, IERS 14 C04, ITRF2014 what allows the assessment of the reference frame consistency. The second aspect of consistency addressed will be the application of observation and correction models. In this respect, we will test state-of-the-art models in VLBI analysis as well as the analysis configuration that is specified through IERS Conventions 2010 and the corresponding IERS Convention updates. The systematic effects found will be in the focus of this study, for example the choice of the mean terrestrial pole for the pole tide loading model. As a third aspect of consistency, we discuss the parameterization of the data analysis. In particular, we will look at the different approaches applied to 24 h and Intensive VLBI sessions. The science-driven quality criteria defined by IAG and its GGOS will be used to judge whether the size of the identified inconsistencies is significant or can be neglected.
Atomic data for stellar spectroscopy
Heiter, Urike
High-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics. Examples include studying the chemical evolution of the Milky Way Galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. The interpretation of these spectra is often based on synthetic stellar spectra, either calculated on the fly or taken from a spectral library. One of the most important ingredients of these spectra is a set of high-quality transition data for numerous species, in particular neutral and singly ionized atoms. We rely heavily on the continuous activities of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic data. I will give an overview of current efforts to compile, assess, and distribute the best available data in a standard way, for example in the context of the Gaia-ESO Public Spectroscopic Survey. This work is facilitated by databases and electronic infrastructures such as the NIST Atomic Spectra Database, the VALD database, or the Virtual Atomic and Molecular Data Centre.
Roles of magnetic fields during the main accretion phase : theoretical landscape
Hennebelle, Patrick
Magnetic field is believed to play a fundamental role during the main accretion phase of stars. First of all the magnetic braking is likely regulating the amount of angular momentum that is available to form the planet-forming disks second of all magnetic field is though to reduce fragmentation. Last but not least, jets and outflows are likely a consequence of the magneto-centrifugal mechanism. These three aspects, depend on how the field is getting transported and how it is coupled to the gas, which itself is a consequence of the micro-physical processes. The talk will address these issues and stress the large uncertainties that remain to be clarified.
Subaru/HSC Identifications of 42 Protocluster Candidates at z~6-7: Implications for Cosmic Reionization
Higuchi, Ryo
We report fourteen and twenty-eight protocluster candidates at z = 5.7 and 6.6 over 14 and 19 deg2areas, respectively, selected from 2,230 Lya emitters (LAEs) photometrically identified with Subaru/Hyper Suprime-Cam (HSC) deep images. Six out of the 42 protocluster candidates include 1-12 spectroscopically confirmed LAEs at redshifts up to z=6.574. By the comparisons with the cosmological Lya radiative transfer (RT) model reproducing LAEs with the reionization effects, we find that more than a half of these protocluster candidates are progenitors of the present-day clusters with a mass of > 10^14 M_sun. We also investigate the correlation between LAE overdensity and Lya rest-frame equivalent width (EW), because the cosmological Lya RT model suggests that a slope of EW-overdensity relation is steepened towards the epoch of cosmic reionization (EoR), due to the existence of the ionized bubbles around galaxy overdensities easing the escape of Lya emission from the partly neutral intergalactic medium. The available HSC data suggest that the slope of the EW-overdensity correlation does not evolve from the post-reionization epoch z = 5.7 to the EoR z = 6.6 beyond the moderately large statistical errors.
The GAIA Revolution in Pre-Main Sequence Stars and Star Clusters
Hillenbrand, Lynne
TBA
A JWST Early Release Science Program to Directly Image Extrasolar Planetary Systems
Hinkley, Sasha
In preparation of the launch of JWST a broad range of proposals have been selected under the Director’s Discretionary Early Release Science Program (DD-ERS) with the primary goal of rapidly producing representative datasets across the modes of JWST within the first few months of operation. Our accepted program, “High Contrast Imaging of Exoplanets and Exoplanetary Systems with JWST”, has been awarded ~52 hours of time and will perform: a) coronagraphic imaging of a newly discovered exoplanet companion, and a well-studied circumstellar debris disk with NIRCam & MIRI; b) spectroscopy of a wide separation planetary mass companion with NIRSPEC & MIRI; and c) deep aperture masking interferometry with NIRISS. These observations have been tailored to the specific goals of our program: 1) generate representative datasets in modes to be commonly used by the exoplanet and disk imaging communities; 2) deliver science enabling products to empower a broad user base to develop successful future investigations; and 3) carry out breakthrough science by characterising exoplanets for the first time over their full spectral range from 2-28 microns, and debris disk spectrophotometry out to 15 microns sampling the 3 micron water ice feature. We present a summary of these observations and our planned science enabling products in order to inform the community ahead of the launch of JWST.
Go beyond radial metallicity gradient: azimuthal variations of oxygen abundance viewed in 3D
Ho, I-Ting
The spatial distribution of the interstellar medium oxygen abundance is the key to understanding how efficiently metals that are synthesized in massive stars can be redistributed across a galaxy. One way to understand how efficient chemical mixing of the ISM occurs on gas orbital timescale is to probe chemical inhomogeneity in the azimuthal direction. Despite decades of studies, evidence of the presence of azimuthal variations of chemical abundances remains circumstantial, in sharp contrast to the copious observational efforts in probing radial gradients. In this talk, I will present two case studies of nearby (<20Mpc) galaxies observed with the TYPHOON Program that delivers 3D optical data with about 100 pc physical resolution and full disk areal coverage. I will show compelling evidence that the ISM oxygen abundance changes systematically in the azimuthal direction. The abundance variations spatially correlate with the spiral structures and are imprinted on negative radial gradients. I will place the observations in the framework of a simple chemical evolution model. I will demonstrate that the systematic, periodic variations are caused by the competition of two physical processes, localized, sub-kpc-scale self-enrichment and efficient, kiloparsec-scale mixing-induced dilution driven by spiral density waves. I will end the talk by discussing future prospects of using the on-going MUSE and ALMA large programs by the PHANGS collaboration to advance our understanding of chemical abundances and mixing on sub-kiloparsec scale.
GaiaNIR - Progress towards a future all-sky astrometry mission
Hobbs, David
With Gaia's second data release in April of this year Europe entered a new era of space astrometry. A weakness of Gaia is that it only operates at optical wavelengths as much of the Galactic centre and the spiral arm regions are obscured by interstellar extinction. In 2017 our proposal to ESA’s call for “New Science Ideas” was successful. Since then work began to define science requirements and a dedicated study was performed by ESA in the Autumn of 2017 to determine how best to implement the mission. A NIR mission requires new types of detectors to scan the entire sky and measure global absolute parallaxes. The spacecraft must have a constant rotation resulting in a moving image that must be compensated for by, for example, operating the detectors in Time Delayed Integration (TDI) mode. During the ESA study two approaches were considered, 1) by adding a descan optical mechanism to hold the image constant on conventional NIR detectors and 2) to develop new TDI detectors in NIR and maintain the classical Gaia like approach. The study found that the descan mechanism resulted in astrometric accuracies that were an order of magnitude worse at the faint end compared to using a TDI like approach. Clearly, such a degradation of accuracy would make a descan mechanism a difficult sell to the science community where improved accuracy at the faint end is a clear goal. Nevertheless, developing TDI in NIR detectors is a difficult and expensive challenge. If this challenge can be solved a new Gaia-like mission separated by a 20 year interval would give; 1) NIR astrometry and photometry to penetrate the obscured regions and to observe intrinsically red objects; 2) improved proper motions with 14-20 times smaller errors than from Gaia alone opening up new science cases; 3) allow the slowly degrading accuracy of the Gaia optical reference frame, which will be the basis for future astronomical measurements, to be maintained.
Ice Feature Spectroscopy in Nearby Molecular Cores with JWST NIRCAM
Hodapp, Klaus
This project will study the spatial distribution of continuum extinction and ice absorption features in three nearby molecular cores: B68, a quiescent core, L694-2, a collapsing core, and B335, a star-forming core. All these objects are situated in front of a dense field of background stars so that numerous lines of sight are available for absorption spectroscopy. We are using the slitless grism spectroscopy capabilities of JWST NIRCAM in the 3 - 5 micro-meter range to obtain spectra of all sufficiently bright background stars, and expect roughly 100 usable spectra per core. This will allow maps of the continuum extinction and ice feature absorption depth with unprecedented spatial resolution and will allow us to study the formation and early chemical processing of ice mantles in detail. This paper will also discuss our choice of instrument and observing method, and present details of the implementation of this project with the Astronomer's Proposal Tool (APT).
Dwarf Galaxy Dynamics in Standard and Modified Gravity
Hodson, Alistair
I will present ongoing research into dwarf galaxy dynamics in standardgravity with dark matter and in modified gravity. I investigatetheoretically and numerically the internal dynamics of dwarf spheroidalgalaxies, like the core-cusp problem, with the aim to determine thefeasibility of using future observational astrometric space missions to distinguish between dark matter models, including warm, self-interacting or superfluid dark matter, and models of modified gravity, where the presence of dark matter is unnecessary, as supported by the stringent upper limits on the gamma-ray fluxes from dark matter annihilation provided by the Fermi mission.
The Toothbrush Radio Relic and Magnetic Fields in the Intracluster Medium
Hoeft, Matthias
We precent recent deep observations of Toothbrush radio relic with the Karl Jansky Very Large Array (VLA). Using all four VLA configurations we obtained an unprecedented detailed view of the relic (Rajpurohit et al. 2018). The images revealed that the emission is rather filamentary. We conclude that wider filaments are caused by projection. In contrast, narrow filaments likely reflect the magnetic field distribution. The relic is significantly polarised above a few GHz and quickly depolarises towards lower frequencies. We present a detailed analysis of the polarisation and depolarisation of the Toothbrush and discuss the Rotation Measure spectra. The Toothbrush radio relic provides a unique insight into the magnetisation of the intra-cluster medium.
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.
Nano dust in stellar atmospheres and winds
Höfner, Susanne
The extended dynamical atmospheres of cool luminous giant stars are places where solid particles condense out of the gas. This stardust leaves its marks on the observable stellar spectra, and also on the structure and dynamics of the stellar atmospheres, since radiation pressure on the newly-formed grains is a key factor for driving the massive winds of evolved stars. In recent years, considerable progress has been made in understanding these processes, and in characterizing the properties of the dust particles. In particular, improvements in high-angular-resolution techniques have led to spatially resolved observations of the dust-forming atmospheric layers of close-by cool giant stars, making detailed comparisons with predictive models possible. I will give an overview of these developments, including results from both observations and numerical simulations.
Eclipses and the Earth's Rotation
Hohenkerk, Catherine
Historical records of eclipses of the Sun and Moon in the period 720 BC to AD 1600 provide vital information about the rotation of the Earth. The extant records come from the ancient civilisations of Babylonia, China, Greece, Arab Dominions, and medieval Europe. Generally, the record of an eclipse allows the place of observation to be established, and contains sufficient local calendrical information for the Julian date to be determined unequivocally. The record also contains an estimate of the local time, from which the Universal Time (UT) of the circumstance of the eclipse can be calculated. In the particular case of total solar eclipses, where the track of totality is very narrow on the Earth’s surface, the possible range of UT is defined by the sharp boundaries of the track. Given the place, date and UT, the local circumstances of the eclipse in Terrestrial Time (TT) can be calculated from the gravitational theories of the motion of the Earth and Moon. The difference, TT-UT, commonly referred to as ΔT, measures the cumulative discrepancy in UT due to fluctuations in the Earth’s rate of rotation, which is conveniently measured by changes in the length of the mean solar day (lod). We have measured the quantity ΔT in the period 720 BC to AD 1600 from observations of several hundred solar and lunar eclipses. The slope on a curve fitted to these data is a measure of the lod. The average long-term increase in the lod is found to be $+1.78$ milliseconds per century (ms/cy), which is significantly less than the increase of $+2.3\,$ms/cy expected on the basis of tidal friction. This implies an accelerative component decreasing the lod by $-0.5\,$ms/cy since 720.
IAU and re-emergence of state-of-art astronomy in Central Asia
Hojaev, Alisher S.
Celebrating the centennial of the IAU we should emphasize its constant and active influence on all aspects of the development of world astronomy, which favorably distinguishes it from professional associations in other fields of science. One could note a lot of undoubted achievements, however, the IAU’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. Recently, thanks to the great initiatives of the newly elected President of the Republic of Uzbekistan 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. Together with colleagues of National Astronomical Observatories of Chinese Academy of Sciences (NAOC) astronomers of Ulugh Beg Astronomical Institute of Uzbek Academy of Sciences have fully renovated 1 meter Zeiss telescope at Maidanak observatory (Uzbekistan) to the state-of-art and started deep all-sky survey within international collaboration with NAOC in special SAGE photometric system (developed by astronomers of NAOC). Based on aforesaid the necessary assistance from the IAU and its possible support are described and discussed along 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.
IMF By-dependent enhancement in high-latitude geomagnetic activity in local winter
Holappa, Lauri
The interaction of the solar wind and the interplanetary magnetic field (IMF) with the Earth's magnetic field produces geomagnetic activity, which is critically dependent on the orientation of the north-south (Bz) IMF component. Most solar wind coupling functions quantifying the relation between solar wind and IMF parameters and geomagnetic activity include the dependence on the sign (polarity) of Bz, within the so-called IMF clock angle. Coupling functions depend on the clock angle in a way, which is symmetric with respect to the sign of the By component. However, recent studies indicate that the sign of By is an additional independent driver of high-latitude geomagnetic activity, leading (for the same clock angle) to higher (weaker) geomagnetic activity in Northern Hemisphere winter for By > 0 (By < 0). In this paper we quantify this explicit By-effect both for Northern and Southern high-latitude geomagnetic activity. We show that the By-effect maximizes when the Earth's dipole axis points towards the night sector, i.e., when the auroral region is maximally in darkness. The By-effect affects the westward electrojet strongly but hardly at all the eastward electrojet. We find that there is a similar By-effect in the occurrence frequency and strength of substorms, largely explaining the By-effect in the westward electrojet. These results are important for predicting space weather effects at high latitudes and for understanding how the solar wind and IMF parameters produce geomagnetic activity.
Cladistics as a tool in Asteroid Taxonomy
Holt, Timothy
Cladistics is traditionally used in the biological sciences to examine the relationships between organisms, commonly referred to as the ‘tree of life’. Recent works in galactic taxonomy, stellar phylogenetics and satellite classification have expanded the technique into Astronomy, collectively called Astrocladistics. The advantage of this method over other analytical techniques is the inclusion of objects with limited information. A full data-set can then be used without truncation.Our aim is to present how cladistics may be used to study asteroid taxonomy. We start by using the Jovian Trojan asteroids as an example population. The Jovian Trojan asteroids are two swarms of captured asteroids, located at the L4 and L5 Lagrange points of Jupiter. The Jovian Trojans provide a test case, as several have well known characteristics, while the majority have limited information available, with the complete population of computationally manageable size.The cladistical method involves the use of algorithms to link possibly related objects in a parsimonious fashion. The results are presented as a dendritic tree, where related objects are closer to one another. Using the cladisical method, we classify the Jovian Trojan swarms, using the inherent characteristics of the asteroids. The resulting taxonomic system can then be compared with existing classifications and identified dynamical families.We present preliminary results from this study, with an indication of how the cladistical technique could be expanded to larger data-sets, and used in the of future asteroid taxonomy.
Calculations of the solar convection zone with the reduced speed of sound technique
Hotta, Hideyuki
We carry out high-resolution and high-density-contrast calculations with using the Reduced Speed of Sound Technique (RSST). The solar convection zone is filled with highly turbulent thermal convection that is responsible for the energy transport, the angular momentum transport, and the dynamo(s) responsible for the Sun’s small and large scale magnetic field. Modeling the convection zone as a whole is challenging due to the strong density stratification leading to a vast separation of length- and time-scales. In order to cope with this challenge, we adopt the new technique, the RSST, in which the effective speed of sound is reduced with changing the equation of continuity. Besides allowing for significantly larger timesteps, RSST also scales well on massively parallel supercomputers since only local communication is required. High-resolution calculations performed with this method reveal that small-scale magnetic field present in the convection zone has a profound influence on the dynamo action generating the large-scale magnetic field. While previous studies found that coherent large scale field is difficult to maintain at high resolution due to a large degree of small-scale turbulence, we find that small-scale magnetic field suppresses small-scale turbulence and allows for the maintenance of a coherent large-scale magnetic field.In addition, another advantage of the RSST is ability to include the photosphere in deep convection zone calculations. Since the temporal and spatial scales of convection drastically change due to the high density and temperature contrast in the convection zone, there has been no calculation covering whole convection zone. We, for the first time, carry out such a calculation from the base of the convection zone to the solar surface with including the realistic radiation transfer. Detailed influences of the surface region on the deep convection zone are investigated.
Helioseismology and the changing solar dynamo
Howe, Rachel
Helioseismology uses waves propagating inside the Sun to measure its internal structure and dynamics. This lets us monitor both the changing subsurface flows over the solar cycle -- the so-called 'torsional oscillation' pattern of migrating bands of faster and slower rotation, together with the modulation of the meridional flow in the activity belts -- and the changes to the frequencies and other properties of the acoustic modes due to magnetic activity close to the surface. We now have continuous data over nearly two solar cycles from the ground-based Global Oscillation Group and the space-borne Michelson Doppler Imager and Helioseismic and Magnetic Imager, together with unresolved-Sun observations from the Birmingham Solar Oscillations Network stretching back to the mid 1970s. This record offers intriguing hints that the behaviour of the solar dynamo may be changing. This review will examine the evidence for such changes and consider what they might mean for the future.
The Global Supernova Project
Howell, Andrew
I'll present the latest results from the Global Supernova Project, a 150+ person collaboration using Las Cumbres Observatory (LCO) to study 500 supernoave over 3 years. LCO is a robotic network of 21 0.4, 1, and 2m telescopes spread around the globe to allow instantaneous and extended access to the night sky. Recent results include the discovery of blue bump from the first hours after a Type Ia supernova, which we interpret as the shock of a supernova hitting a nondegenerate companion star. We have also used the cooling after shock breakout to measure the progenitors of core-collapse supernovae. I'll also prevent several lines of evidence indicating that circumstellar material is ubiquitous in core-collapse supernovae, even in cases where no narrow lines from interaction are seen.
Supernova-driven winds in simulated dwarf galaxies
Hu, Chia-Yu
We investigate galactic outflows/winds driven by supernova (SN) explosions in an isolated dwarf galaxy using high-resolution (1M_sol) hydrodynamical simulations that include cooling, star formation, stellar feedback and metal enrichment. We find that the system reaches a quasi-steady state in a Gyr timescale with strong temporal fluctuations.Clustered SNe lead to the formation of superbubbles which break the disk and vent out the hot gas, launching the winds. At the virial radius, the time-averaged loading factors of mass, momentum and energy are 3, 1 and 0.05, respectively. We identify two different modes for the winds to escape the halo. Hot gas acquires velocities higher than the escape velocity v_esc within the disk and escapes rapidly. In contrast, warm gas generally has velocities smaller than v_esc within the disk, but is afterwards accelerated multiple times by subsequent episodes of bursts of hot winds and slowly escape the halo. The strong interactions between different temperature phases highlight the caveat of extrapolating wind properties to large distances based on its local properties (e.g. the Bernoulli parameter). We conduct convergence study and find that wind properties converge at 5M_sol, and the winds diminish dramatically once the cooling masses of individual SNe become unresolved. We demonstrate that injecting the terminal momentum of SNe,a sub-grid recipe widely adopted in the literature, does not lead to more efficient winds compared to pure thermal energy injection. The failure of this recipe is owing to its incorrect assumption that most thermal energy has already been radiated away right after the injection even for very clustered SNe.
Galactic kinematics and dynamics from the LAMOST Galactic Spectroscopic Surveys
Huang, Yang
One of the fundamental tasks of modern astrophysics is the quest of an understanding of how galaxies formed and evolved. Generally, the quest could be pursed in two complementary approaches: statistical analyses of large samples of more distant galaxies (far-field cosmology) and detailed studies of large samples of member stars in our own and other nearby galaxies (near-field cosmology). As a milestone of ‘near-field cosmology’ to fulfill the quest for understanding galaxy formation and evolution, the LAMOST Galactic Spectroscopic Surveys have hitherto collected quality spectra of over 7.5M Galactic stars, and this number is still increasing at a rate of 1M per annum. Benefitted from this single largest spectroscopic dataset as well as data from other photometric and spectroscopic surveys (e.g. SDSS/SEGUE, SDSS-III/APOGEE, Gaia), significant progresses have been made on the studies of the kinematics and dynamics of the Milky Way, including_x000D_ 1) Accurate estimates the peculiar velocities of the Sun that define the Local Standard of Res;_x000D_ 2) A detailed investigation of the bulk motion of nearby disk stars, in 3-dimension for the first time;_x000D_ 3) Accurate determinations of the Galactic rotation curve out from 8 to 100 kpc and the escape velocity curve from 5 to 14 kpc, as well as of the mass surface density in the solar neighborhood;_x000D_ 4) Finally, by combining the LAMOST measurements and the first Gaia data release, a sample of nearly ten thousand local (within 800 pc) main-sequence turn-off stars has been selected, with very accurate 3-dimensional positions and velocities, as well as chemical composition and age information. The sample allows us to study the local disc(s) in multi-dimensional phase space, yielding pivotal information that help constraint the formation and evolution of the Galactic disc(s).
A systematic search for hypervelocity stars from the LAMOST spectroscopic surveys
Huang, Yang
We have carried out a systematic search for Hypervelocity stars (HVSs) in nearly 6.5 million qualified (SNRs > 10) stellar spectra of 4.4 unique stars collected upto June 2016 by LAMOST spectroscopic surveys, and have discovered three HVSs, including the one found earlier by Zheng et al. (2014). The two newly discovered HVSs are respectively a B2V type star of ∼ 7 solar mass with a Galactic rest- frame radial velocity of 502 km/s at a Galactocentric radius of ∼21kpc and a B7V type star of ∼ 4 solar mass with a Galactic rest-frame radial velocity of 408 km/s at a Galactocentric radius of ∼ 30 kpc. More importantly, in the era of Gaia, accurate measurements of three dimensional motions become possible for the three bright HVSs. The measurements provide constraints on the shape of the dark matter halo of the Galaxy.
Kepler Exoplanet Radius Demographics in the Gaia Era
Huber, Daniel
The Kepler space telescope has revolutionized our understanding of exoplanet demographics. However, for nearly all of Kepler's discoveries our knowledge of planet radii is limited by the uncertainties in the radii of the host stars. Additionally, large radius uncertainties for the full sample of 150,000 Kepler exoplanet program targets are still a dominant source of systematic errors for measuring occurrence rates of small planets. The release of Gaia DR2 parallaxes in April 2018 will spectacularly solve this bottleneck by allowing the determination of <~5% radii for nearly every Kepler target. In this talk I will present the latest results on Kepler exoplanet radius demographics based on combining Gaia DR2 parallaxes with the Kepler stellar properties catalog, including an investigation of the intriguing "radius gap" for close-in super-Earths shaped by photoevaporation and a revised catalog of small, habitable-zone exoplanets based on updated stellar parameters. I will also discuss the prospects of using Gaia to investigate age demographics of exoplanets discovered by Kepler/K2.
Asteroseismology versus Gaia: How Accurate are Scaling Relations for Solar-like Oscillators?
Huber, Daniel
Gaia DR2 will include high-precision parallaxes for nearly all ~15,000 Kepler targets showing solar-like oscillations, providing an unprecedented sample to test the accuracy of fundamental stellar parameters derived from asteroseismology over a wide range of evolutionary states. I will present results of comparing and calibrating asteroseismic scaling relations using Gaia DR1 (TGAS) and DR2 parallaxes, including over a dozen oscillating red giants with near model-independent radii measured by combining parallaxes with angular diameters from long-baseline interferometry using the CHARA Array. I will furthermore use APOGEE spectroscopy to investigate deviations from scaling relations as a function of metallicity and evolutionary state, and discuss the implications of such deviations for the characterization of exoplanet host stars and galactic archeology.
The Large Millimeter Telescope Alfonso Serrano
Hughes, David
The Large Millimeter Telescope (LMT) Alfonso Serrano is a bi-national (Mexico & USA) telescope facility operated by the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) and the University of Massachusetts. The LMT is a 50-m diameter single-dish millimeter-wavelength telescope, designed and optimized to conduct scientific observations at frequencies between ~70 and 270 GHz. Constructed on the summit of Volcán Sierra Negra at an altitude of 4600m in the Mexican state of Puebla, the LMT has started full scientific operations as a 50-m diameter telescope, making the LMT 50-m the world´s largest single-dish telescope operating at 1.1mm. I will describe the history and current status of the LMT project, summarise the lessons learned and emphasis the contribution the LMT will make in the study of the formation and evolution of structure in the dusty optically-obscured universe at all cosmic epochs.
Cuneiform Descriptions of Transient Phenomena
Hunger, Hermann
In sources from Ancient Mesopotamia, transient astronomical phenomena occur in two contexts: in records of observations, many of which can be dated; and in collections of omens, which use the appearance of such phenomena to find in them predictions of future events. These omens consider quite a range of phenomena, but with rare exceptions they cannot be dated in a precise way. The paper will describe how transient phenomena are handled in both kinds of texts.
Stability of hierarchical stars in globular star clusters
Hypki, Arkadiusz
We present the first results concerning the stability of hierarchical systems of stars (triples and higher) in globular clusters using a broad range of numerical simulations done with the MOCCA code (http://moccacode.net).Globular clusters (GCs) are unique laboratories for studying various types of stars or stellar systems. There are numerous papers about the role which single and binary stars play in the stellar and dynamical evolution of GCs. However, the formation and dynamical evolution of higher hierarchies are poorly covered. The interest in hierarchical systems has increased in the recent years significantly as it was realized how important they can be for the formation and evolution of exotic objects, like close binary systems.The MOCCA code is currently one of the most advanced codes which is able to follow the full stellar and dynamical evolution of the real size GCs. Recently, MOCCA received procedures which allow to form and then follow the dynamical evolution of hierarchical systems. This code is orders of magnitude faster than N-body codes which allows to perform a broad range of numerical simulations for various initial conditions. This, in turn, allows to perform statistical analysis of the stability of hierarchical systems for many different GCs.
Virtual Observatory for education
IAFRATE, GIULIA
The goal of the Virtual Observatory (VO) is to allow astronomers to make best use of the large quantity of data archived every day in professional observatories all over the world. The International Virtual Observatory Alliance (IVOA) is a world-wide organisation defining the relevant standards for data interoperability. IVOA is also interested in education (through an Education Interest Group) and dissemination (covered by a dedicated Media Group).VO for education is a project developed within the framework of the European Virtual Observatory (EuroVO) with the aim of diffusing the VO data and software to the public, in particular students, teachers and astronomy enthusiasts, thanks to the easy access to the data guaranteed by simple interfaces and to a choice of interesting use cases.VO for education offers use cases, pedagogical units, and simplified professional software that allows a taste of the emotion of scientific research even to those approaching astronomy for the first time or simply wishing to wander among stars.The educational material and software tools of VO for education have been designed specifically for teachers in support of an effective presentation of astronomy in the classroom. The main characteristics of our educational software tools are the following: they are free, multilingual, based on professional tools and they easily access VO data. The core of VO for education consists of use cases we designed and complemented with proper multilingual documentation covering both the astrophysical context and the use of the software. Use cases and software have been revised during an intense program with high school students in the framework of the EU H2020 ASTERICS project.
Fullerenes and PAHs in the Interestellar Medium
iglesias groth, susana
We will review theoretical work, astronomical observations and measurements inlaboratory of the new form of carbon known as fullerenes and their hydrogenated forms (fulleranes). These molecules can be responsible for diffuse interstellar bands, the UV "bump", main feature in the extinction curves observed in many lines of vision of our Galaxy and other galaxies and the anomalous microwave emission discovered in several regions of star formation, in molecular clouds and HII regions. Recent detections of C60 and C70 fullerenes in planetary nebulae in our Galaxy and in the Magellanic cloud reinforce the hypothesis that fullerenes and fulleranes are common in the interstellar medium and could contribute significantly to these processes. Other potential agents of anomalous microwave emission processes and interstellar extinction bands are polycyclic aromatic hydrocarbons (PAHs). We will summarize the efforts made to achieve the identification of the simplest PAHs, naphthalene and anthracene, in regions of anomalous microwave emission and the results I have obtained on the search for fullerenes in protoplanetary discs.
Reverberation mapping and the broad-line region of AGN in the ELT era
Ilic, Dragana
The broad emission lines, seen in the optical spectra of type 1 active galactic nuclei (AGN), are produced in the so-called broad-line region (BLR), i.e. the ionized gas, of sub-parsec dimensions, heated by the central continuum source. For the last several decades, the continuous optical monitoring of type 1 AGNs have shown that the change of the line flux is responding to the change of the continuum flux with the certain time-delay, which can be used to directly estimate the size of the BLR. This is the base of the techniques called "reverberation mapping", used for the study of geometry and kinematics of the BLR of the monitored AGN. This method has also revealed the empirical relation between the BLR radius and the continuum luminosity, i.e. the radius-luminosity relation, which is widely used for single-epoch observations of type 1 AGN. In this contribution, we discuss the usage of the reverberation-mapping techniques in the frame of the large telescopes, presenting some possible results and discussing possible problems and caveats.
Round table discussion and Conclusions
Impey, Chris
Main topics to discuss: Involving more young educators in the Commission. Ways to share instructional materials and best practices. How to start an international journal on astronomy education (taking into account different languages)? How to find AE researchers in many countries and join the community? How to increase the surveys of publications in many countries and languages? How to increase astronomy contents in the schools worldwide? Our participation in the LP control at a Global scale. The impact of the activities on Astronomy for equity and inclusion. The integrated education in Astronomy, taking into account not only the discipline itself (Physics, Maths), but also Biology, Chemistry, History, Philosophy and Pedagogy. The way to communicate our job to the professional astronomers, the Newsletter.
Radial metallicity gradients with Galactic stellar probes
Inno, Laura
By being the only galaxy that we can resolve star-by-star, the Milky Way (MW) is an ideal model organism to test our understanding of galaxy formation and evolution. After their birth, the MW stars change their orbit through secular evolution processes, but not their chemical abundances that encode the composition of their gaseous birth material. As a result, the spatial variation of stellar metallicity in the disk reflects the Galactic assembly history at different radii, providing a key constraint for MW evolution models. In particular, the decreasing of heavy element abundances as a function of Galactocentric radius, i.e. the negative metallicity gradient, is the observable counterpart of the “inside-out” formation of the disk. However, a large diversity of measured gradients can be found in the literature, with values ranging from -0.01 to -0.09 dex/kpc, depending on the tracers used. In order to understand if this diversity comes from Galactic evolution processes or observational biases, stellar probes uniformly distributed across the disk and with accurately known ages are needed. Such tracers have now been made available by large spectroscopic surveys (e.g. Gaia-ESO, APOGEE etc.), which have extensively targeted and characterised selected stellar probes. In this talk, I will review recent results on the metallicity gradients measured for old (Red Giants), intermediate (Open Cluster) and young (Cepheids) stellar probes, and discuss their implication for Galactic evolution. But among these tracers, only Cepheids are luminous enough to be seen even through substantive dust absorption, thus throughout the entire disk. I will present new results based on hidden Cepheids recently discovered in the extremely obscured regions of the disk, which allow us to determine the chemical content of the mixed gas at the interface between the inner Galactic components, and of pristine infalling gas in the flared disk.
Cepheids with MICADO@E-ELT: A 2-steps cosmic distance scale
Inno, Laura
The Hubble constant (H0) provides independent constraints on the spatial curvature of the Universe, its dark energy content, and neutrino physics. Thus, a measurement of H0 to 1% accuracy is crucial to improve our current knowledge of the fundamental physics. Cepheids play a prominent role in understanding the uncertainties on H0, since they contribute to the majority of the total error budget. By using the largest near-infrared (NIR) dataset to-date for almost 7,000 Cepheids in the Magellanic Clouds (MCs), we showed that Cepheids NIR Period-Luminosity (PL) relations are universal, linear and independent of the metal content. Distances based on NIR PL relations are affected by random error at less than 1% level and by systematics at 5% level, where the systematics mostly concern the zero-point calibration and will be addressed by using a new independent calibration from Gaia. By using MICADO@E-ELT, we will be able to identify and characterise Cepheids down to a limiting magnitude of ~26 mag (J band) with 1hr exposure, and, in turn, to accurately measure the distances of spiral galaxies in the Local Group and beyond (> 4Mpc), from which H0 can be directly derived. Moreover, by adopting NIR PL relation and applying light-curve templates to estimate the mean magnitude from single epoch measurements, we derived accurate individual distances to all the Cepheids in the MCs and obtained their 3D mapping. The adopted approach has proved very efficient to uncover the spatial distribution of the young stellar population in nearby galaxies. E-ELT will allow us to export this analysis to farther and more complex systems such as e.g. the closest merging galaxy, Cen A.
The role of magnetic field in the formation and evolution of filamentary molecular clouds
Inutsuka, Shu-ichiro
Recent observations have emphasized the importance of the formation and evolution of magnetized filamentary molecular clouds in the process of star formation. Theoretical and observational investigations have provided convincing evidence for the formation of molecular cloud cores by the gravitational fragmentation of filamentary molecular clouds. The size and total angular momentum of a protoplanetary disk are supposed to be related directly to the rotational property of the parental molecular cloud core where the central protostar and surrounding disk are born. In this review we summarize our current understanding of various processes that are required in describing the filamentary molecular clouds and try to understand the origin of angular momenta of molecular cloud cores and its link to the mass function of cores and the stellar initial mass function.
Formation of the Earth-Moon system
Ipatov, Sergei
Computer simulations showed [1-2] that trans-Neptunian satellite systems and embryos of the Earth and the Moon could be formed as a result of contraction of rarefied condensations. The angular momenta of condensations needed for formation of trans-Neptunian satellite systems could be acquired at collisions of condensations [3-4]. The same conclusion is true for the Earth-Moon system. The angular momentum of the present Earth-Moon system could be acquired at a collision of two rarefied condensations with a total mass not smaller than 0.1ME, where ME is the mass of the Earth. The mass of the condensation that was a parent for the embryos of the Earth and the Moon could be about 0.01ME, if we take into account the growth of the angular momentum of the embryos at the time when they accumulated solid planetesimals. In order to explain small fraction of iron in the Moon, it is needed that the mass of the Moon embryo increased by no more than 1.3 times. For such Moon growth, the mass of the Earth embryo that accumulated planetesimals would increase by no more than a factor of 3. The initial masses of embryos of the Earth and the Moon could be small if the Moon embryo accumulated mainly iron depleted bodies ejected from the Earth embryo in numerous collisions of planetesimals with the Earth embryo. The work was supported by the grant of Russian Science Foundation N 17-17-01279 (formation and growth of the embryos of the Earth and the Moon) and by the Program of Fundamental Studies of the Presidium of RAS ? 28 as a part of state program for GEOKHI N 00137-2018-0033 (studies of the angular momenta of colliding celestial objects). [1] Nesvorny D., et al. Astron. J. 2010. 140. 785-793. [2] Galimov E.M., Krivtsov A.M. Origin of the Moon. New concept / De Gruyter. Berlin, 2012, 168 p. [3] Ipatov S.I. Solar System Research, 2017. 51. 321-343. https://arxiv.org/abs/1801.05217. [4] Ipatov S.I. Solar System Research, 2017. 51. 409–416. https://arxiv.org/abs/1801.05254.
Modelling the atmosphere of habitable planets
Iro, Nicolas
The list of planets discovered in the habitable zone of its star is continuously growing. We will present a hierarchy of models (from 1D radiative transfer to 3D climate models) in order to better infer on the habitability of such systems.Particular focus will be on Proxima Centauri b (Anglada-Escudé et al. 2016, Nature, 536, 437) as well as the TRAPPIST-1 planets (Gillon et al. 2017, Nature, 542, 456). In the case of Proxima Centauri b, the two possible planetary rotation regimes (1:1 and 3:2 spin-orbit resonances, as inferred by Ribas, A&A 596, A111, 2016) will be investigated. As far as the TRAPPIST-1 system is concerned, we will focus on planets c, d and e.
Characterising ExOPlanet Satellite (CHEOPS): ESA's first s-class science mission
Isaak, Kate
Kate Isaak on behalf of the ESA CHEOPS Project Team and the CHEOPS ConsortiumCHEOPS (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. The call for proposals for the first year of observing will come out in Summer 2018.In this presentation I will give an overview of CHEOPS mission, the science, the mission status and the Community opportunities to observe with CHEOPS.
Large-scale transport of solar magnetic flux
Isik, Emre
Synoptic observations of the solar surface reveal the key role of bipolar magnetic regions (BMRs) in shaping the solar cycle. As magnetic structures encompassing dark spots and bright faculae, BMRs are subject to the surface flux transport (SFT) process. SFT models provide us with significant insight in our understanding of the solar cycle, in particular when constraining dynamo models. Observational constraints and recent progress in our theoretical understanding favour a Babcock-Leighton type dynamo, which is not far from critical excitation, involving relatively weak nonlinear effects. In addition, observations and models show that the solar cycle is rather sensitive to rare BMRs with extreme properties, which can potentially trigger grand minima and recover normal cycles. The emergence properties of sunspot groups can be reproduced by simulations of flux tubes rising from the convection zone. When the Sun was younger and more rapidly rotating, its surface patterns of activity were likely affected by stronger dynamo action and stronger inertial effects in flux emergence. Forward modelling the emergence and surface transport of magnetic flux is thus crucial in our quest to reverse-model the observed brightness variations of Sun-like stars.
On the astrometric bias for objects with overlapping image profiles
Ivantsov, Anatoliy
Astrometric measurements of celestial objects that lie close in the imaging plane are subject to a small systematic error due to an overlap in their image profiles. The latter causes a displacement of the maxima of measured intensities with respect to their true positions. In fact, any astrometric measurement is affected by this bias, if the position of one object is not corrected for the displacement induced by light pollution from other nearby objects.In this contribution, we present an exact analytical expression for this displacement error assuming symmetric Gaussian point-spread functions. The astrometry of fast moving objects in the Solar system is particularly negatively affected by this issue. In order to assess the significance of this bias, we have analyzed past ground-based astrometric measurements of asteroids available through the IAU Minor Planet Center that had asteroids within a distance of 3 arcsec to Gaia catalogue stars. Regions of high correlation densities were detected between the proposed corrections in both right ascension and declination and (O—C) in positions calculated using the JPL HORIZONS system. Our results suggest that the above-described bias is indeed present and can be detected in past ground-based astrometric measurements of asteroids.As past astrometric measurements prolong the observation arc they tend to have more leverage on asteroid orbit solutions than present ones although the latter may be more precise. Correcting for such biases can be, therefore, crucial for asteroid impact monitoring.To better quantify and control the here described biases during orbit fitting we suggest requesting the measured image width (FWHM) from asteroid observers when submitting observations to the IAU Minor Planet Center. We emphasize, furthermore, that this type of bias is not exclusive to ground-based observations but is affecting space-borne astrometry, such as Gaia measurements of the closely imaged objects, as well.
LSST: making movies of AGB stars
Ivezic, Zeljko
LSST (www.lsst.org) will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachon in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 sq.deg. field of view, and a 3.2 Gigapixel camera. In a continuous observing campaign, LSST will cover the entire observable sky every three nights to a depth of V~25 per visit (using 30-second exposures and ugrizy filter set), with exquisitely accurate astrometry and photometry. Close to a half of the sky will be visited about 800 times during the nominal 10-year survey. The project is in the construction phase with first light expected in 2020 and the beginning of regular survey operations by 2022. I will describe how these data will impact AGB star research and discuss how the system could be further optimized by utilizing narrow-band TiO and CN filters.
Magnetic field detections in Herbig Ae SB2 systems
Jaervinen, Silva
Studies of the presence of magnetic fields of Herbig Ae/Be stars are extremely important because they enable us to improve our insight into how the magnetic fields of these stars are generated and how they interact with their environment, including their impact on the planet formation processes and the planet-disk interaction. We report new detections of weak mean longitudinal magnetic fields in the close Herbig Ae double-lined spectroscopic binary AKSco and in the presumed spectroscopic Herbig Ae binary HD 95881 based on observations obtained with HARPSpol attached to ESO's 3.6 m telescope. Such studies are important because only very few close spectroscopic binaries with orbital periods below 20d are known among Herbig Ae stars. Our detections favour the conclusion that the previously suggested low incidence (5-10%) of magnetic Herbig Ae stars can be explained by the weakness of these fields and the limited accuracy of the published measurements. The search for magnetic fields and the determination of their geometries in close binary systems will play an important role for understanding the mechanisms that can be responsible for the magnetic field generation.
Experiments on the formation of carbonaceous dust and molecules
Jäger, Cornelia
Carbonaceous dust is present in nearly all astrophysical environments proving its existence by the interstellar extinction, IR spectra, and elemental depletion patterns. Dust grains absorb and scatter stellar light and reemit the absorbed energy at infrared and millimeter wavelengths. They affect the formation rate of H2 and organic molecules being formed on the surface or in ice layers covering grain surfaces in the interstellar medium (ISM). Asymptotic giant branch stars and supernovae (SNe) are major dust factories. However, dust grains can be efficiently processed and completely destroyed in SN shocks and have to be re-formed in the ISM. In order to understand all dust-related astrochemical processes, laboratory experiments are desperately required. Experimental studies on the nucleation and condensation of carbonaceous dust have demonstrated that carbon nanoparticle and molecules, including polycyclic aromatic hydrocarbons (PAHs) and fullerenes, condense in gas-phase condensation processes at high temperature. In addition, recent experimental studies have demonstrated that organic molecules and carbonaceous solids can also be formed at conditions prevailing in molecular clouds. Refractory fullerene-like carbon particles were formed in cryogenic ice layers at about 10 K. In the talk, I will compare experimental results on the formation pathways of carbonaceous matter at high and low temperatures and discuss the role of precursors and chemically matured molecules such as PAHs, carbon chains, and fullerenes. The formation of refractory carbonaceous grains is either governed by PAHs or by chain-like carbon molecules. However, carbon grains can also be a source for the formation of carbonaceous molecules. Reactions on the surface or at the interface between dust and ice may lead to the erosion of dust and formation of new molecular species.
Prevalence of radio jets associated with quasar outflows and feedback
Jarvis, Miranda
We have identified that radio jets are commonly associated with ``radiative mode” feedback. By performing a systematic multi-wavelegnth study of z<0.2 quasars, we have found that >~70% of `radio quiet’ type 2 quasars, that host kpc-scale ionized gas outflows, exhibit radio jet structures. I will present our results on the pilot sample of 10 objects that combine high resolution (~0.3-1 arcsec) radio imaging at 1-6GHz with optical IFU observations. Our results demonstrate that is it extremely common for jets to be spatially and kinematically linked to kpc-scale ionized gas kinematics in such quasars. Therefore, radio jets may be an important driver of outflows during `radiative mode'’ feedback, apparently blurring the lines between traditional divisions of feedback modes. Based on a recently accepted VLA proposal our sample should reach ~50 quasars during 2018. I will outline our on-going campaign to obtain multi-wavelength observations to provide a full picture of the properties, drivers and impact of galaxy wide outflows in low redshift quasars.
Mapping cluster evolution with Hubble Frontier Fields & BUFFALO observations
Jauzac, Mathilde
Massive galaxy clusters make the best, and most efficient locations to observe and trace the mass assembly processes of the Cosmic Web. Residing at the vertices of it (Bond et al. 1996), they grow by steady accretion of matter from the surroundings, as well as by discrete mergers with nearby groups and clusters. Supported by simulations, this scenario predictions regarding the total mass content and distribution of infalling substructures remain largely untested.Recently, some of the most massive and disturbed clusters have been the centre of attention thanks to the \emph{Hubble Frontier Fields} (HFF) initiative, which constitutes the largest commitment ever of \emph{Hubble Space Telescope} (HST) time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters. These clusters were chosen for their strong lens properties, and are all highly disturbed objects, showing major and minor merging on-going processes, making them ideal target to trace the Cosmic Web assembly.While combining strong and weak-lensing regimes to map the total mass with X-rays observations of the hot gas and spectroscopy of cluster galaxies to look at their direction of motion, we can thus study the dynamical scenarios in place within these massive galaxy clusters, and trace the sub-structures engaged in these processes. I will present the latest results we obtained on the HFF clusters when compared with state-of-the-art numerical simulations of the substructure infall rates, mass growth of these cosmic beasts as a function of cosmic time. I will also discuss the different caveats present on both the observing and simulation sides.Finally, I will present what comes next, with the upcoming BUFFALO large HST programme, the 'spatial extension' of the HFF scheduled to start in July 2018.
AGB populations as probes of galaxy structure and evolution
Javadi, Atefeh
The evolution of galaxies is driven by the birth and death of stars. AGB stars are at the end points of their evolution and therefore their luminosities directly reflect their birth mass; this enables us to reconstruct the star formation history. These cool stars also produce dust grains that play an important role in the temperature regulation of the ISM, chemistry, and the formation of planets. These stars can be resolved in all of the nearby galaxies. Therefore, the Local Group of galaxies offers us a superb near-field cosmology site. Here we can reconstruct the formation histories, and probe the structure and dynamics, of spiral galaxies, of the many dwarf satellite galaxies surrounding the Milky Way and Andromeda, and of isolated dwarf galaxies. It also offers a variety of environments in which to study the detailed processes of galaxy evolution through studying the mass-loss mechanism and dust production by cool evolved stars. In this talk, I will first review our recent efforts to identify mass-losing AGB stars and RSGs in Local Group galaxies and to correlate spatial distributions of the AGB stars of different mass with galactic structures. Then, I will outline our methodology to reconstruct the star formation histories using variable pulsating AGB stars and RSGs and present the results for rates of mass-loss and dust production by pulsating AGB stars and their analysis in terms of stellar evolution and galaxy evolution.
Getting to Know Sub-Saturns and Super-Earths: High-Resolution Spectroscopy of Transiting Exoplanets
Jayawardhana, Ray
Characterizing exoplanet atmospheres presents a formidable challenge, primarily due to the extreme brightness contrast between the planet and the host star. However, spectroscopy during transits, when stellar light passes through a planet’s atmosphere, offers a rare opportunity to identify the presence of atomic and molecular species and other atmospheric features. To date, for the most part, transit spectroscopy has targeted hot Jupiter planets, mainly at low spectral resolution. High-resolution spectroscopy, on the other hand, could be used to not only make robust detections but also to probe the temperature-pressure profile and dynamics (i.e., wind speeds) in the planets’ upper atmospheres. Recently we have extended such studies to exoplanets in the sub-Saturn and super-Earth mass regimes, using high-resolution spectroscopy with 8-meter-class telescopes and cross-correlation techniques, to search for alkali metal lines as well as water vapor. Here we report on our latest findings, including new detections, and discuss prospects for the near future.
Probing the Lowest-Mass Free-Floating Objects with JWST: GTO Program and Beyond
Jayawardhana, Ray
How far down in mass the stellar initial mass function (IMF) extends is a fundamental, unresolved question in astrophysics. The shape of the IMF at the lowest masses will not only establish the boundary between objects that form ‘like stars’ and those that form ‘like planets’, but also distinguish among competing theoretical models for the origin of brown dwarfs. Thanks to extensive surveys by us and others, the IMF is now reasonably well characterized in several nearby star-forming regions down to about 10 Jupiter masses, but not below. Our approved GTO program with NIRISS on the JWST aims determine whether there is a substantial population of hitherto undetected 1-5 Jupiter mass objects, possibly formed in protostellar disks and subsequently ejected. We plan to use NIRISS in the WFSS mode to survey a nearby young cluster to unprecedented depth, in order to (1) establish firmly the shape of the IMF below the Deuterium-burning limit, (2) investigate the fragmentation limit for ‘star-like’ formation, and (3) quantify the population of isolated planetary-mass objects. Our observations of NGC 1333 will not only identify and confirm objects down to 1-2 Jupiter masses, but also provide a first estimate of their temperature, and thus mass. Follow-up high- resolution spectroscopy with NIRSpec could improve temperature/mass estimates, derive C/O ratios to trace the formation mechanism, look for accretion features, and test atmosphere models. Multi-band MIRI photometry of planetary-mass objects could probe the presence and characteristics of dusty disks in their midst.
Pulsations as Probes in Hydrogen-Deficient Atmospheres
Jeffery, Simon
The extreme helium stars V652 Her and BX Cir exhibit large amplitude radial pulsations with periods of 0.1 d. High spectral and temporal resolution observations have been made at both optical and ultraviolet wavelengths to explore the surface motion, demonstrating differential motion within the visible photospheres and, in particular, the passage of a shock wave through the photosphere at minimum radius. These observations are being used to provide strong tests of non-linear pulsation theory. We will present new Hubble Space Telescope spectroscopy of V652 Her, which was obtained to probe photospheric layers over a range of optical depths not visible at optical wavelengths. We will also present recent SALT and K2 observations of related extreme helium stars and discuss the implications for opacity driven pulsations in early-type extreme helium stars.
Searching for the sources of meteorites in the asteroid belt
Jenniskens, Peter
The study of meteorites has found new purpose with the study of observed meteorite falls that have yielded a pre-atmospheric orbit from photographic or video observations of the meteor. Each meteorite originated from a unique collision event, most of which occurred somewhere in the asteroid belt, and subsequently the fragments dynamically evolved their orbit until one impacted Earth. Consortium laboratory studies of recovered meteorites are conducted to determine to what specific collision event that meteorite belonged. Many opportunities exist to take part in these studies. They include determining the cosmic ray exposure age that determines how long the meteoroid was exposed to cosmic rays in the interplanetary medium since ejection from a larger body, noble gas (K-Ar, U,Th-He) resetting ages that define the collision history of the terrain on that larger body, and Pb-Pb ages that define the formation history of the parent asteroid. The studies look into isotopes of oxygen, chromium and titanium, and petrographic properties that can help distinguish one ordinary chondrite from another. Studies can also look into the mobility of volatile organic compounds and volatile minerals. In doing so, these studies provide much new insight into the origin and evolution of their parent bodies. Recent consortium studies have yielded new results on Almahata Sitta Ureilite (the meteorites that fell from the impact of asteroid 2008 TC3), the Creston L6 fall in California, and the Saricicek Howardite fall in Turkey. Efforts are underway to expand this work in order to increase the number of approach trajectories of each meteorite type and from each collision event that is now sampled at Earth.
Review of asteroid family and meteorite type links
Jenniskens, Peter
There are now 33 meteorite falls (as of February 1, 2018) that have a documented trajectory and pre-atmospheric orbit. Although there are more different meteorite types than this, the more common types are represented in a handfull of cases each. From that, patterns are emerging that suggest that LL type chondrites originated from a source at the inner edge of the inner asteroid belt, while CM type chondrites originated from a source close to the 3:1 mean-motion resonance. H and L type chondrites originated from more than one source. Those sources are past collisions on large asteroids or members of asteroid families, which offer the highest probability for impacts, that liberated enough material to be sampled here at Earth. Following the collision, the meteoroid orbit evolved for 0.9-100 Ma, but model calculations show that they are expected to impact Earth still with an inclination similar to that of the source asteroid orbit, and a semi-major axis distribution that points to the delivery mean-motion or secular resonance responsible for changing their orbital eccentricity. We will review our current understanding of what asteroid families might be responsible for meteorite types documented so far, present preliminary results of recent falls, and discuss new approaches to increasing the number of documented meteorite falls dramatically by using high-resolution fireball tracking and A.I.-equipped drones to help find meteorites from smaller falls.
The true nature of ultra-faint stellar systems in the Milky Way halo
Jerjen, Helmut
The true nature of ultra-faint stellar systems in the Milky Way haloUltra-faint dwarf galaxies are intriguing stellar systems. Unlike large, luminous galaxies, they are completely dominated by the ubiquitous, cosmologically important non-baryonic dark matter. Stars contribute less than 1 percent to the total mass. At the same time these galaxies host some of the most pristine, least chemically evolved stars. These unique properties make dwarf galaxies the most sought-after laboratories in a number of astrophysical research areas. The latest all-sky imaging surveys have delivered a few dozen ultra-faint dwarf galaxy candidates in the Milky Way halo. As these systems are often found at the detection limits it is fundamentally important to establish their status as ultra-faint dwarf galaxies, stellar clusters, stream features or even false-positives. Incorrectly classified objects can seriously affect conclusions drawn by studies in near-field cosmology, galaxy formation, and stellar evolution, thereby hampering progress in these areas. I will present recent results from our ongoing deep follow-up observations as part of the Stromlo Milky Way Satellite Survey that has the goal to scrutinize candidates and physically/chemically characterize ultra-faint stellar systems. One immediate application is testing the validity of the size-luminosity and metallicity-luminosity relations in the ultra-faint regime. These crucial informations determine what sort of structures we are probing in the Milky Way halo.
Nano dust and the far-ultraviolet interstellar extinction
Jiang, Biwei
The continuing rise of extinction in the far-ultraviolet (shortward of about 2000 angstrom) is observed in the Milky Way, and the nearby galaxies including the Magellanic Clouds and M31. This phenomenon indicates the presence of very small (~200 angstrom) particles in the interstellar medium. Yet, the carrier(s) responsible for this far-UV rising has not been certainly identified. Some candidates are suggested, from large molecules to very small dust grains. This talk will review the far-UV extinction laws in various environments, both Galatic and extra-galactic, and the dust models to explain the laws.
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.
Magnetic Fields in the Intergalactic Medium from observations of Fast Radio Bursts
Johnston, Simon
Fast Radio Bursts (FRBs) are millisecond pulses of radio emission at cosmological distances. As the radiation from the FRB travels through the intergalactic medium, it undergoes both dispersion and faraday rotation. The dispersion measures the ionised electron content along the line of sight, and this combined with the rotation measure yields the magnetic field strength. I will report on observations of FRBs using the Parkes telescope and concentrate on the measurements of the rotation measure and the implication for the intergalactic medium magnetic field out to redshifts above z=1.
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.
Studying extra-planar, ionized gas with stacked MaNGA galaxies
Jones, Amy
Gas in the outskirts of galaxies can greatly influence the evolution of their host galaxies and additionally can help solve the missing baryons problem. Warm ionized gas is faint and diffuse and hence difficult to study. By stacking multiple similar SDSS IV MaNGA galaxies, we can clearly detect this extra-planar gas out to several kpc, between four and ten kpc depending on the sample. MaNGA is an IFU survey that covers the entire optical range, so we have detections of emission lines, including [OII], [OIII], H_beta, [OI], [NII] H_alpha, [SII], as a function of scale height. Currently there are over 4000 galaxies observed, and about 800 of those are edge-on systems that can be used in this study. This increases our previous sample by a factor of ten! We split this sample into many subsamples to see how the gas properties (e.g. temperature, density, ionization state) depend on the host galaxy properties (e.g. morphological type, star formation rate). Also, we determine the mass of metals and baryons in the outskirts for each subsample. We can compare our measurements for the extra-planar gas with what has been seen in other CGM studies with Quasars to form a complete picture of warm ionized gas in the outskirts of galaxies.
The Near Earth Asteroid associations
Jopek, Tadeusz
Clustering among the small bodies of the Solar System is a longstanding problem. Prominent peaks in histograms of the orbital parameters suggests existence of the groups of objects of potential common origin, just like in case of the meteoroid streams and the main belt asteroid families. These concepts are accepted beyond the doubts.Similarity between the NEAs orbits was discovered ~40 years ago. Drummond, among 708 NEAs found 14 associations of 4-25 members. However, he came to a conclusion that many groups might be attributed to chance alignments. Further studies made by different researchers did not bring conclusive results. Therefore, whether the NEAs associations of a common origin exist is an open question.In this study we made an extensive search for associations amongst ~17000 NEAs. We used a few D- functions and rigorous cluster analysis approach.We have found a dozen groups of 30 or more members. Statistical reliability of this finding is quite high, 95%. However, by the cluster analysis technique one can not decide about a common origin of these associations. One need additional test, e.g. a study of the dynamical past history of each group. We undertaken such study.Nevertheless, irregardless of their common origin, the existence of the NEAs associations is undisputed fact, they were found just like one detects the meteoroid streams. The origin of them is an open concern.Recognition of the NEAs associations is very important because their serious thread to the Earth. Analogously to meteoroid streams, each year the Earth is almost crossing the orbits of each association. We do not know how many members consists each group, perhaps 50, perhaps 500?.To facilitate monitoring of an association we have calculated coordinates of its theoretical radiant and a calendar date of its potential activity. Such information allows the observers better planning of the observation campaigns of these hazardous objects.
Passband reconstruction from photometry
Jordi, Carme
Based on an initial expectation from laboratory measurements or instrument simulations, photometric passbands are usually subject to refinements. These refinements use photometric observations of astronomical sources with known spectral energy distribution. This work investigates the methods for and limitations in determining passbands from photometric observations. A simple general formalism for passband determinations from photometric measurements is derived. The problem of passband determination is formulated in a basic functional analytic framework. For the solution of the resulting equations, functional principal component analysis is applied. We find that, given a set of calibration sources, the passband can be described with respect to the set of calibration sources as the sum of two functions, one which is uniquely determined by the set of calibration sources, and one which is entirely unconstrained. The results are applied to the passbands of HIPPARCOS, Tycho, and Gaia.
New insights into the complex chemistry of young stars from the ALMA PILS survey
Jorgensen, Jes Kristian
One of the most important problems of astrochemistry is to understand how, when and where complex organic and potentially prebiotic molecules are formed - and the link between the rich chemistry observed toward some star-forming regions and the emerging Solar System. From an observational point of view, ALMA is revolutionizing the field with its high sensitivity for faint lines, high spectral resolution limiting line confusion, and high angular resolution making it possible to study the structure of young protostars down to scales of their emerging protoplanetary disks.In this talk, I will present an overview of some of the results from a large ALMA survey of the low-mass protostellar binary and astrochemical template source, IRAS 16293-2422. The program, "Protostellar Interferometric Line Survey (PILS)", is more than an order of magnitude more sensitive than previous surveys of chemical complexity and provide images of the inner 25 AU of the gas around each of the young stars. The high sensitivity and spectral resolution of ALMA has allowed us to detect a wealth of previously undetected species in this object and the ISM in general - for example, molecules of importance for prebiotic chemistry such as peptide-bond containing molecules (Ligterink et al. 2017) and simple sugars (Jørgensen et al. 2012), as well as species that can be used to link protostars in the earliest stages of their evolution to our own Solar System such as measurements of methyl chloride and sulfur-molecules toward Comet 67P and IRAS 16293-2422 (Fayolle et al. 2017; Drozdovskaya et al. 2018). Also, the data show the presence of numerous rare isotopologues of complex organic molecules and other species (e.g., Coutens et al. 2016, 2018; Jørgensen et al. 2016; Persson et al. 2018): the exact measurements of the abundances of these isotopologues shed new light onto the formation of the complex molecules and provide a chemical link between the embedded protostellar stages and the early Solar System.
LSST & ELTs: Time Domain
Juric, M.
TBA
Modeling of Family-Forming Impacts
Jutzi, Martin
The observed asteroid families are composed of bodies that are thought to be a result of energetic collisions which lead to catastrophic disruptions of their larger parent bodies. Asteroid families such as the one associated with asteroid Vesta can also be created by less energetic cratering impacts.As a complement to experimental and theoretical approaches, numerical modeling has become an important component to study asteroid collisions and impact processes. The formation of asteroid families as a result of large-scale disruptions consists two distinct phases: the impact / fragmentation phase, and the gravitational reaccumulation phase. They are characterized by very different time scales and therefore require a hybrid modeling approach, coupling shock-physics code models and gravitational N-body methods.In numerous modeling studies, the effects of target properties and impact conditions on the outcome of family-forming collisions have been investigated. Monolithic, pre-shattered, micro-porous or rubble-pile targets have been studied and a range of target sizes has been explored. The comparison between simulation outcomes for various kinds of parent-body structures and the actual family properties can help to constrain the internal properties of the parent body of the considered families.We will discuss recent modeling approaches and results of studies of catastrophic disruptions and family-forming collisions. Various numerical methods and material models used in the shock-physics codes will be presented and the inherent model uncertainties will be discussed.
Star Formation in the solar neighborhood - surveys, generalities, simulations
Juvela, Mika
Star formation is a major cosmic process that started soon after the big bang and still continues, albeit at a decreasing rate. It is the formation of dense interstellar clouds, their fragmentation, andeventual collapse that gives birth to new stars. These steps are best studied using high-resolution observations of nearby regions in the Milky Way. The progress is following the improvement of infrared and radio wavelength instruments that are able to probe the inner cloud regions and thus directly the initial phases of the star-formation process. On the other hand, numerical simulations are already able to take into account most of the relevant physics and they provide another, sometimes more clear view into the general principles behind the star formation. The comparison of observations and simulations is particularly fruitful, to validate the models and to separate universal trends from the complexity of individual sources. I will review recent star-formation studies, touching on both observations and simulations and seeking connections between the two.
Magnetism in the early Universe
Kahniashivli, T.
TBA
Regional Activities of IAU and Worldwide Astronomy
Kaifu, Norio
I will present some historical analysis of Regional IAU Meetings and efforts of cooperation in East Asia, and discuss the importance of regional coordination toward "Astronomy for All", a future target wich IAU is aiming to.
Towards a Sub-Gyr Age of the Ancient Globular Cluster M92 with JWST
Kalirai, Jason
Messier 92 is the nearest system to the Sun that represents a truly ancient and metal-poor stellar population. High precision visible light photometry of the globular cluster consistently shows it to be a 13 Gyr population. In our James Webb Space Telescope Early Release Science (ERS) Program, "The Resolved Stellar Populations ERS Program", we will obtain exquisite near-infrared photometry of the cluster down to well below the newly discovered main-sequence "kink" feature, below which lower-mass and cooler M dwarfs become bluer in the infrared colors. By modeling the stellar populations on this infrared plane, we can remove degeneracies between distance, reddening, and metallicity and establish the most accurate age of the globular cluster to date. For M92, this measurement sets a new limit on when the earliest baryonic structure formation began in the Milky Way galaxy. In this presentation, we will demonstrate the power of infrared diagnostics to establish globular cluster properties based on state-of-the-art Hubble Space Telescope WFC3/IR observations, and motivate our new ERS program.
Post-AGB and Post-RGB Stars as Tracers of Binary Evolution.
Kamath, Devika
It is well established that binary interactions can alter the intrinsic properties of stars (such as: pulsation, mass-loss, photospheric chemistry, dust-formation, circumstellar envelope morphology etc.) and play a dominant role in determining its ultimate fate. While past studies have shown that binarity can end the AGB life of a star, recent studies have revealed that, in specific cases, binarity can also pre-maturely terminate the RGB evolution. A characteristic feature of these evolved binaries is the presence of a Keplerian circumbinary disk of gas and dust which plays a lead role in the evolution of the systems. In this talk I will review our advances in the research landscape of post-AGB and post-RGB binary stars, focussing on their observational properties, spectral energy distribution, photospheric chemistry, the orbital parameters, the characterisation and evolution of their stable circumbinary discs, and the evolutionary connection between the enigmatic post-AGB and post-RGB binaries, and other systems whose primary component is a White Dwarf.
Molecular dust precursors in envelopes of oxygen-rich AGB stars and red supergiants
Kaminski, Tomasz
Condensation of circumstellar dust begins with formation of molecular clusters close to the stellar photosphere. These clusters are predicted to act as condensation cores at lower temperatures, i.e. allow efficient dust formation farther away from the star. The condensation process is poorly understood, particularly in oxygen-rich stars. Recent observations of exotic metal oxides, such as AlO, AlOH, TiO, and TiO2, whose emission can be traced at high angular resolutions with ALMA, have allowed first observational studies of the condensation process in oxygen-rich stars. We are now in the era when depletion of gas-phase species into dust can be observed directly. I am going to present the most recent observations that allow us to identify the species that initiate the formation of inorganic dust close to photospheres of AGB stars and red supergiants. I am also going to discuss challenges one has to face in interpreting the observations, especially these related to non-equilibrium chemistry, non-LTE gas excitation, and high complexity of stellar atmospheres in the dust-formation zone. Finally, I am going to propose future observations and laboratory measurements that will help us overcome some of the difficulties.
Physical and Chemical Properties of Planet Forming Disks
Kamp, Inga
VLT instruments and ALMA have revolutionized in the past five years our view and understanding of how disks turn into planetary systems. They provide exquisite insights into non-axisymmetric structures likely closely related to ongoing planet formation processes. This talk will review our current understanding of the physical properties (e.g. solid and gas mass content, snow and ice lines) and chemical composition of planet forming disks at ages of 1-few Myr, especially in the context of the planetary systems that are forming inside them. It will highlight recent advances achieved by means of consistent multi-wavelength studies of gas AND dust in protoplanetary disks.
Acceleration of Cosmic Ray Electrons at Shocks in Merging Galaxy Clusters
Kang, Hyesung
Weak shocks with typical Mach number, M<3, are expected to form due to supersonic flows in merging galaxy clusters. The presence of such shocks has been indicated by X-ray and radio observations of many merging clusters. In particular, diffuse radio sources known as radio relics could be explained by synchrotron-emitting electrons accelerated via diffusive shock acceleration (Fermi I) at collisionless shocks in high-beta intracluster medium. It has been also suggested that nonthermal electrons can be further accelerated via stochastic acceleration (Fermi II) by MHD/plasma turbulence downstream of such shock. In this contribution, we explore a reaccelration model in which a shock of M=2-4 sweeps through a preshock cloud containing low-energy fossil electrons, supplemented by Fermi II acceleration due to transit time damping resonance off compressive MHD turbulence in the postshock region. We find that turbulent acceleration with tac ~108 yr is required in order to match the observed broad profiles of the radio flux density of a few radio relics.
Astronomy from Europe to the East:A passage through India in the early 17th century
Kapoor, Ramesh
This paper is about the observations of two great comets of November 1618 made from Goa by Father Venceslaus Kirwitzer, astronomer and part of a group of missionaries led by Nicolas Trigault that was deputed in 1618 to China to spread faith as also the new European science. Father Kirwitzer (1620) presented a detailed description of his observations in a monograph in Latin, entitled Observationes Cometarvm Anni 1618. In India Orientali Factæ A Societatis Iesv Mathematicis in Sinense Regnum Nauigantibus ex itinere eo delatis. The treatise remained untraceable till digitized in 2014 by the Austrian National Library. It is of great importance, for, the work reports first ever modern cometary observations outside Europe as also the first ever use in India of an optical device for astronomical purpose soon after the introduction of telescope to astronomy. Modern astronomy took over a century to be systematically pursued in India. We have on hand only three documented instances of astronomical usage of the telescope in the seventeenth century India. The other instances are of Jeramiah Shakerley’s in 1651 for the transit of Mercury and the bright comet of 1652 in Surat, and by the French Jesuit Fr. Jean Richaud in 1689 to find Alpha Centauri as being a double and a sungrazer C/1689 X1 with a 12 ft telescope. These instances were no trend setters but scored many firsts and preceded several instances of telescopic use for celestial events and for the geographical surveys in the 18th Century India.
Planary Session: Nucleosynthesis in AGB stars
Karakas, Amanda
The chemical evolution of the Universe is governed by the nucleosynthesis contribution from stars, which in turn is determined primarily by the initial stellar mass. I will review the status of theoretical stellar nucleosynthesis models and yields of single stars up to about 10 solar mass. Stars in this mass range evolve to become cool red giants after the main sequence, with the richest nucleosynthesis occurring during the AGB phase. It is during the giant branches that these stars experience mixing events that change the surface composition, with significant enrichments in carbon and heavy elements synthesized by the slow neutron capture process (the s-process). While the qualitative picture of the s-process is well known, there are major uncertainties that affect stellar yields and our understanding of the chemical evolution of galaxies. I will discuss some of these uncertainties and also highlight areas where progress has been made.
The Influence of Metallicity on Stellar Differential Rotation and Magnetic Activity
Karoff, Christoffer
Over an 11-year cycle the Sun changes its brightness by less than 0.1%, it is however, an open question how strong the Sun's photometric variability was in the distant past. One way to answer this question is to study other Sun-like stars and compare their photometric variability with that of the Sun. Ground-based spectroscopic observations of a 7.4-year cycle in the solar analog HD 173701 complemented with observations from the NASA Kepler space telescope constitute one of the most complete set of observations of a stellar cycle ever obtained for any Sun-like star. These observations thus provide an important inseight in how dynamos work in other Sun-like stars.
The Assembly of Disk Galaxies: From Keck to JWST
Kassin, Susan
One of the most important open issues in astronomy is the assembly of galactic disks. Over the last decade this has been addressed with large surveys of internal galaxy kinematics spanning the last ~10 billion years of the universe. I will discuss recent results from my group that show the progressive (and mass-dependent) kinematic assembly of disk galaxies since a redshift of 2.5. We find that galactic angular momentum increases with time and is a strong function of the stellar mass of galaxies, even at high redshift. Our results strongly challenge traditional analytic models of galaxy formation and provide an important benchmark for simulations.Furthermore, I will discuss our plans for using the IFU and multi-object spectrograph on JWST/NIRSpec to enrich our understanding of galaxy kinematics to a redshift of 5, and to extend measurements to the much earlier universe. From mock JWST observations of simulations of galaxies, we are finding that interpreting these observations is not necessarily straightforward.
X-ray transients observed by MAXI
Kawai, Nobuyuki
Monitor of All-sky X-ray Image (MAXI) on the ISS scans most of the sky every 92 minutes in the 2-30 keV band since August 2009. In the last one year since September 2017, three X-ray transients discovered by MAXI have been confirmed by follow-up observations by Neil Gehrels Swift Observatory and ground-based telescopes, including two black hole candidates MAXI J1535-571 and MAXI J1813-095. We searched for X-ray counterparts of gravitational wave sources including the neutron star merger GW170817 for which we provided the earliest X-ray upper limit. MAXI also provided long-term X-ray light curves for numerous X-ray sources. For some bright sources, the variation of energy spectra associated with state transitions can be studied. We present the results from the long-term monitoring of GRS 1915+105, and compare with past pointed observations.
Recent Results in Family Identification
Kazantsev, Anatolii
To select the asteroid families more clearly the D(a) distribution of asteroid sizes by their semimajor axes and the N(p) distribution of the number of steroids by their albedo values for individual families were used. The families identified by others scientists using the Hierarchical Clustering Method were analyzed with the use of these distributions, and correctly and incorrectly isolated families were found. A reduction in the mean albedo with increasing semimajor axis is observed for almost all correctly identified families that are not truncated by resonances. This reduction is statistically significant for the majority of these families. Not a single family exhibits a statistically significant increase in albedo. This points on an action of a specific nongravitational effect (NGE) in the asteroid belt results in the spatial separation of asteroids with different albedos. Besides, another convincing argument for reality of the NGE is found. There were calculated differences (da) of semimajor axes of asteroid orbits for 10 years, which are not caused by the gravitational influence of the planets. It was obtained a significant dependence of the da values on the asteroid albedos. Confirmation of the NGE reality also serves as confirmation of decreasing in the mean albedo with increasing semimajor axis for separate families.
The Largest Fully Steerable Telescope
Kellermann, Kenneth
From the very earliest, planning for NRAO was based on the construction of a very large fully steerable radio telescope with a diameter up to 1000 feet. Recognizing that it might take a long time to design and construct a very large antenna, NRAO decided to first build a modest size 140-foot telescope which was thought to be available essentially off-the-shelf. Following long debates about whether it should be equatorial or alt-az mounted, an equatorial mount was foolishly selected, but the construction was fraught with technical difficulties, a factor of 7 cost overrun, and a delay from an anticipated 2-year construction period to more than 7 years._x000D_ After the construction of the 300-foot transit telescope with its limited capabilities, NRAO initiated the LFST program to design and potentially construct the Largest Feasible Steerable Telescope. The LFST team produced a series of designs for a large fully steerable telescope, but none of these were ever built. Although every review of the needs of radio astronomy supported the construction of a large fully steerable radio telescope, there was always a higher priority – the VLA, the VLBA, and more recently ALMA. In 1988, an NSF review committee recommended that the 27 year-old NRAO 300-foot transit telescope be closed in order to provide funds for operating other new astronomical facilities. But, when the 300-foot telescope unexpectedly collapsed in November, 1988, it was reported in the media as a national disaster for U.S. astronomy. West Virginia’s Senator Byrd demanded that the telescope be replaced. Although the NSF had other plans, Byrd included $75M in the 1989 Congressional Emergency Supplemental Appropriations Bill. The new 100-meter Green Bank telescope would not be completed until the year 2000, and only after contentious litigation as to who was responsible for the delays and nearly factor of two increase in cost.
The OAD from an Indian Perspective
Kembhavi, Ajit
In my talk I will first summarise some key points which emerge from the FM15 presentations and discussions. Then I will consider the OAD from an Indian perspective. India has a highly developed astronomical base. Indian astronomers are engaged in a wide range of astronomical and astrophysical research, including theory, observations, data analysis and instrumentation. India has telescopes on the ground and in space, and is a partner in important international projects. The professional astronomy has percolated to the levels of college and high school students as well as the general public. India therefore has a vigorous amateur astronomical movement which often translates into developmental activity. India is also a major and successful participant in the International Olympiads, including the astronomical Olympiads, which again helps in meeting developmental goals. Many of these activities are supported by the Astronomical Society of India, which has its own range of high intensity events. The nature and level of the activities and developmental goals in India closely mirror those of the OAD and the ROADs, and yet India has so far not been working closely with the OAD. Integrating the Indian efforts with those of the OAD could bring great mutual benefit and provide opportunities to various countries to participate in the Indian activities through collaborations and visits. I will provide examples of what is possible.
Studying the evolving interstellar medium of galaxies with JWST
Kemper, Ciska
In this talk, I will review outstanding questions on the properties andthe evolution of the interstellar medium of galaxies, including ourown Milky Way, that can and will be addressed with the JWST in the comingyears. I will build on what we have learnt from previous facilities,in particular the Spitzer Space Telescope; in particular, results from theSurveying the Agents of Galaxy Evolution (SAGE) survey of the MagellanicClouds will be used to define key questions for the evolution of theinterstellar medium of galaxies.
Emission-line diagnostics for metallicity gradients in galaxies
Kewley, Lisa
I will present an overview of the application of emission-line diagnostics for diagnosing the metallicity gradients in galaxies. I will summarize the current state-of-the art in metallicity diagnostics, including empirical, theoretical, and Bayesian statistical methods for calculating metallicities across galaxies. I will describe what we have learned and what still can be learned from metallicity gradients in isolated and merging galaxies using integral field spectroscopic surveys, including chemical evolution, the impact of gas inflows, galactic-scale outflows, metallicity gradients in AGN, and tidal effects on metallicity gradients during galaxy mergers. I will conclude with a simulation of how metallicity gradients can be measured in the future on the ELTs.
Galaxy Evolution in 3D
Kewley, Lisa
Tracing matter and chemical elements in the Universe is critical for understanding the formation of the first galaxies, the formation and growth of supermassive black holes, and ultimately the evolution of galaxies like our Milky Way. Throughout the history of the universe, large-scale gas flows have moulded the arms of spiral galaxies, formed the bulges of the most massive galaxies in the universe, fed supermassive black holes in the centers of galaxies, fueled generation upon generation of new stars, and enriched the intergalactic medium with metals. The physics and impact of these processes can now be traced through new efficient, wide-field 3D integral field spectrographs. With multi-object integral field spectroscopy, we can now probe these transformative galaxy processes statistically for thousands of galaxies. I will describe how our understanding of galaxy evolution has been changed through these surveys to help us understand the relationship between gas inflows, galactic-scale outflows, star-formation, chemical enrichment, and active galactic nuclei in galaxies. I will link these studies with new insights into the early universe traced through gravitational lensing and infrared adaptive optics. I will finish by discussing how this field will be transformed in the JWST and ELT era.
ISM conditions in distant galaxies
Kewley, Lisa
The conditions in the ISM are critical for star formation, the evolution of HII regions, for the fuelling of supermassive black holes, and the propagation of galactic outflows throughout galaxies. I will present an overview of the ISM conditions in distant galaxies. I will describe the latest methods for measuring ISM conditions in the high redshift universe, utilizing stellar evolutionary synthesis and photoionisation and shock models. I will discuss new self-consistent UV - optical - IR diagnostics for measuring the ISM conditions in galaxies across cosmic time. I will finish by presenting a summary of how this field will be dramatically opened in the ELT era.
High-resolution observations of AGB stars with ALMA and SPHERE: imaging the stars, the gas, and the dust
Khouri, Theo
The mass-loss mechanism of asymptotic giant branch stars has long been thought to rely on two processes: stellar pulsations and dust formation. The details of the mass-loss mechanism have remained elusive, however, because of the overall complexity of the dust formation process in the very dynamical pulsation-enhanced atmosphere. Recently, our understanding of AGB stars and the associated mass loss has evolved significantly, thanks both to new instruments which allow sensitive and high-angular-resolution observations and the development of models for the convective AGB envelopes and the dust formation process. ALMA and SPHERE/ZIMPOL on the VLT have been very important instruments in driving this advance in the last few years by providing high-angular resolution images in the sub-mm and visible wavelengths, respectively. I will present observations obtained using these instruments in the same epoch (2.5 weeks apart) of two AGB stars, Mira and R Doradus, that resolve even the stellar disks. Moreover, ALMA reveals the distribution and dynamics of the gas around the star, while the polarised light imaged using SPHERE shows the distribution of the dust grains expected to drive the outflows. The inner circumstellar environments of the two stars differ significantly. On the one hand, the observations of Mira show a central source surrounded by asymmetric distributions of gas and dust, with complementary structures seen in the two components. The observations of R Doradus, on the other hand, reveal a much more symmetric inner envelope in which dust condenses efficiently very close to the star. The well-resolved stellar disk of R Dor is asymmetric, however, and appears different in the visible and the sub-mm. By fitting radiative transfer models to high-excitation molecular lines and light scattered by dust, the gas and dust density distributions are constrained to provide important constraints to wind-driving models.
Probing the Magnetized Disk-Halo Interaction in M51 via Wideband Polarimetry
Kierdorf, Maja
An excellent laboratory for studying well ordered magnetic fields is the grand design face-on spiral galaxy M51. Due to wavelength-dependent Faraday depolarization, polarized emission at different radio frequencies gives a picture of the galaxy at different depths: previous observations at L-band (1-2GHz) probes the halo region while at C-band (4-8GHz) the polarized emission comes from the disk region of M51. In this talk, I will present new observations of M51 with the Very Large Array at S-band (2-4GHz), where currently no polarization data exists, to shed new light on the interaction region between disk and halo. The wide frequency coverage and high spatial resolution of about 7 arcsec allow us to probe the disk-halo interaction region to get detailed information on the magnetic field structure in the plane of the sky and on the vertical magnetic field component in this unknown layer.Previous models applied to the polarized emission shows a change from an axisymmetric (m=0, in the disk) to a bisymmetric (m=1, in the halo) magnetic field configuration. I will show our observational results of the transition layer, which is critical for our understanding on the origin of large-scale halo fields and how they are connected to the underlying galactic disk.
Coronal Mass Ejections in Interplanetary Space and Their Geospace Response
Kilpua, Emilia
Interplanetary coronal mass ejections (ICMEs) and their sheath regions are key large-scale heliospheric transients that drive strong space weather disturbances at the Earth. Although intrinsically connected, ICMEs and sheaths have distinctly different origin and solar wind conditions, and consequently, they cause different responses in the near-Earth space environment. In this presentation I will discuss key differences in space weather relevant parameters in these structures, how they control the solar wind – magnetospheric coupling efficiency and specific challenges in predicting their geoeffectivity. I will in particular highlight differences in geospace response (ring current, auroral region, radiation belts) to two typical solar wind forcing “modes”: 1) smooth, low Alfvén Mach number and low dynamic pressure type solar wind driving typical to flux ropes embedded in ICMEs, and 2) turbulent, high Alfvén Mach number and high dynamic pressure solar wind driving typical to sheaths.
KEEP-North: Photometric observations of the Baptistina asteroid family
Kim, Myung-Jin
Study of rotational properties of an asteroid family based on time-series photometric observations offer a unique opportunity to have an insight into collisional process and into the dynamical evolution of the family members. There are a number of observational studies on the rotational properties of old-type asteroid families. Slivan (2002) and Slivan et al. (2003) discovered the spin vector alignment in the Koronis family. Kim et al. (2013) showed that the distribution of rotational periods in the Maria asteroid family is non-Maxwellian. At the same time, a number of young asteroid families have been studied: Yoshida et al. (2016) analyzed photometric data of the Karin family, which is considered to have undergone less collisional and orbital evolution, however they concluded that more lightcurve data are needed to confirm the results.The Baptistina family is one of the typical young asteroid families with an estimated age of about 140-320 Myrs (Masiero et al. 2012); considered to do not have enough time to experience significant collisional and dynamical evolution since it formed. Therefore, it may offer a unique insight into spin rate distribution of relatively fresh fragments and physical mechanism of a family break-up event. Photometric observations of the Baptistina family asteroids were conducted using 0.5 m- to 2 m- class optical telescopes at 6 observatories as part of KEEP-North (Kirkwood Excitation and Exile Patrol of the Northern sky) project. We were awarded a total of 130 full nights every year at BOAO, LOAO, and SOAO for five years beginning in 2016. For this study, we used the SOAO 0.6 m telescope, the BOAO 1.8 m telescope in Korea, the LOAO 1.0 m telescope, the McDonald Observatory 2.1 m Otto Struve Telescope in the United States, the TUG 1.0 m telescope in Turkey, and the NARIT 2.4 m telescope in Thailand. Here, we present our preliminary results from lightcurve analyses of Baptistina family members.
Low-temperature formation of silicate and oxide nano-dust
Kimura, Yuki
Fundamental physical and chemical properties of dust are essential to understand whole processes of material evolution in a history of the universe. Especially, surface free energy and sticking probability have large uncertainty despite critical parameters to establish dust formation model based on nucleation theories. Nucleation from vapor to solid has a large hindrance because of disadvantage for creation of a new surface. To overcome the large barrier for phase transition, larger supersaturation is required. Especially, in a gas outflow of late-type stars, dust is only able to form at very low-temperature compared with thermal equilibrium because of rareness of solid materials for heterogeneous nucleation. Recent years, we have tackled to know how dust forms in such extreme condition; how large supersaturation is required, how different physical properties they have in an environment far from thermal equilibrium, and whether dust formation follows classical nucleation theory or multistep nucleation. Our microgravity experiments using sounding rockets gave us following results. The sticking probability of Fe to be solid from supersaturated gas is as low as 0.002% against 1 as conservatively thought [1]. Formation of alumina dust around oxygen-rich late-type stars and its 13 µm feature was successfully duplicated by a specially designed experimental system. Our laboratory experiments using an in-situ IR measurement system of dust analogues during nucleation and growth succeeded reproduction of the spectrum of astronomical silicate with Mg-bearing silicate particles and found two step crystallization process that a liquid droplet form from a supersaturated gas at first and, then, forsterite nucleates and grows from the supercooled droplet [2]. These findings provide a solid basis for elaborating models of condensation of dust in the universe.[1] Kimura, et al., Science Advances, 3 (2017) e1601992.[2] shizuka, Kimura, Sakon, ApJ, 803 (2015) 88.
Radio diagnostics of the Sun with old and new instruments
Klein, Karl-Ludwig
Radio astronomy offers a broad variety of tools to probe thermal and non thermal processes in the solar atmosphere. Radio mapping provides density and temperature diagnostics through the well-understood bremsstrahlung process of quiet emission. Radio diagnostics are uniquely sensitive to non-thermal electrons in quiescent and eruptive active regions, and give otherwise unavailable insight into the acceleration and propagation of electrons in solar flares and eruptive events. While solar-dedicated instruments are and remain essential for a maximum common coverage with space observatories, general purpose telescopes like the VLA, LOFAR and MWA have a great discovery potential due to their high spatial and spectral resolution, and ALMA offers unprecedented possibilities to extend radio diagnostics to the chromosphere. The talk will illustrate some recent results, give an overview of the new instruments, and emphasise the support that radio observations provide to the key space missions of heliophysics in the coming years, Parker Solar Probe and Solar Orbiter.
High-mass X-ray binaries as progenitors of gravitational wave sources
Klencki, Jakub
The recent discovery of the first double neutron star (NS-NS) merger, if representative for the underlying population, indicates rates of such events as high as 320-4700 Gpc-3 yr-1.This challenges our understanding of the binary evolution, as models that predict high enough rates of NS-NS mergers overpredict those of double black holes (BH-BH).One of the major open questions in the formation scenario of compact binary mergers from isolated binaries is what are the stability criteria for the mass transfer during a high-mass X-ray binary (HMXB) phase. Recent simulations suggest that, in the case of black hole accretors, the mass transfer from massive donors may remain stable in a wider range of parameters than previously thought, thus avoiding a common envelope evolution, and giving rise to a population of Roche-lobe overflowing (RLOF) HMXBs with supercritical mass transfer rates. Those of such HMXBs that fall within the optimal range of periods will eventually become close BH-BH binaries that are going to spiral in and merge.We present a method for reconstructing the evolution of massive binaries based on the information obtained from the gravitational wave detections. In particular, we infer about the population of HMXBs that form BH-BH mergers through a phase of stable mass transfer. We also discuss the connection between the mass transfer stability criteria and the high-luminosity end of the observed X-ray luminosity function.
A survey of moclecular gas in HI-Absorption-Selected Systems
Klitsch, Anne
Studying the multiphase circum-galactic medium and its connection to the baryons in the host galaxies is an important step towards a better understanding of the evolution of galaxies over time. Large steps forward have been made in detecting the multiphase circum-galactic medium through absorption line studies. Today it is possible to connect the cold neutral gas in the halo to its host galaxy by combining absorption and emission selected samples. However, the link to the molecular gas phase from which the stars form is still missing. We have exploited ALMA calibrator observations to perform a novel (sub)mm survey, ALMACAL. We are searching for CO emission lines from the host galaxies of known Lyman alpha absorbers. The parent sample of 57 absorbers towards 26 quasars probes a redshift range of 0.05 < z < 3.0. We have detected CO emission more than a dozen galaxies coincident with the absorber redshift at 0.15 < z < 2.5 with impact parameters between 10 and 130 kpc. We derive molecular gas masses of around 10^10 M_sun and relate the molecular gas masses with the impact parameter or the quasar sight line. Furthermore, we can infer the conditions for star formation in those galaxies from the CO spectral line energy distribution and get first constraints of the temperature and density of the ISM. Preliminary modelling of the CO spectral line energy distribution suggests that some of these galaxies do not show Milky Way like star formation conditions.
The History of Asteroid Family Identification
Kneževic, Zoran
Asteroid families are discovered a century ago by Kyotsugu Hirayama (1918). In this paper a review of the history of this discovery and of the asteroid family identification in general is presented. Starting from Hirayama’s work and his ingenious interpretation of these findings, we briefly mention several important subsequent developments which brought us to the present day’s understanding of families as key evidence of the solar system collisional evolution.I describe here the two intertwined threads: the development of theories of asteroid motion and the computation of their proper orbital elements that serve as parameters for classification into families, and of the methods of family identification themselves. In the period following Hirayama’s pioneering work and lasting to the mid-fifties of the 20th century, the efforts were mostly devoted to identification of families by using an ever increasing catalog of known asteroids, but also to attempts towards understanding of origins and properties of families; the next few decades were characterized by a gradual increase of interest in the families and by a growing understanding of their role in the big picture of the solar system’s evolution; this eventually resulted in an explosion of work and results in the subsequent period, a contemporary era, that lasts until nowadays.
Elemental Abundances at Cosmic Time
Kobayashi, Chiaki
Not only metallicity but also elemental abundances can give strong constraints on the formation and evolutionary history of galaxies. Using our cosmological, chemodynamical simulations, we will predict how gas-phase CNO abundances evolve in late-type galaxies and [alpha/Fe] ratios of stellar population in early-type galaxies, both of which will be accessible with JWST. For the former, using the latest yields of asymptotic giant branch stars, we show how the typical star formation history of disc galaxies can be constrained from the time evolution of CNO abundances. For the latter, using our SNIa model that can match a number of observations in the Local Universe, I will discuss when and how star formation should be quenched.
The role of AGB stars in Galactic and cosmic chemical enrichment
Kobayashi, Chiaki
Elemental abundances and isotopic ratios of stars in the Galaxy have provided stringent constraints on the formation and evolutionary history of the Milky Way Galaxy. It is now possible to apply this Galactic archaeology approach for other galaxies where elemental abundances of stellar populations are measured within galaxies with IFU surveys. Using my galactic chemical evolution models and chemodynamical simulations, I will show AGB stars are important for the production of C, N, and s-process elements, while super-AGB stars are not because of the mass range. Electron capture supernovae can provide Sr, Zr, and Y, but are not the main source of r-process elements such as Eu. The production of C and N by AGB stars is important for constraining the star formation histories of disk galaxies and JWST will deliver such observations at high-redshift galaxies.
Meghnad Saha: Work, life and times
Kochhar, Rajesh
It is no coincidence that IAU and Saha’s ionization formula are about the same age. Both events are related to World War 1 and connected with Germany though in entirely different ways._x000D_ Once sufficiently large number of stellar spectra had been obtained and empirically classified according to the Harvard scheme it was inevitable that theoretical explanation would be forthcoming. The only surprise was that the breakthrough came from the far-off Calcutta which was nowhere on the world research map._x000D_ History chose the hour; the hour produced an unlikely hero: Meghnad Saha. Calcutta University had just become a research centre under Indian auspices. By a fortuitous combination of circumstances immediately after the war, latest German language physics publications arrived in Calcutta as a personal library. While Europe needed time to resume scientific exchanges and activity, India seized the opportunity and produced two outstanding pieces of theoretical work: Saha’s ionization formula (1920), and Bose statistics (1926). It is to the credit of The Royal Society that it elected Saha as a member (1927) in spite of the government’s objections arising from Saha’s anti-British stance. Saha however was unable to carry out further observational and experimental work suggested by the theory._x000D_ Saha was a multi-faceted personality with strong views on political ideology, role of science in a new nation, and other topics. India’s charismatic Prime Minister Jawaharlal Nehru during 1947-1964 had a soft corner for sophisticated, suave, upper-crust people. Impatient and angry, confrontational rather than persuasive, Saha did not qualify. _x000D_ Saha is justly regarded as one of the founders of theoretical astrophysics. Examination of his life and work is a rewarding exercise from various points of view: development of modern astronomy; Western science and the non-West; and political and social activism of a leading scientist and educator.
Formation and evolution of galaxies in clusters revealed with ELTs
Kodama, Tadayuki
I will review what we can learn on the formation and evolution of galaxy clusters and galaxies therein with ELTs.
AAS Nova and Astrobites as Bridges Between Astronomy Communities
Kohler, Susanna
Education and outreach in astronomy often focuses on communicating broad astronomical concepts. But how can educators and outreach practitioners also share current astronomical research results with students and the public, conveying both the process of science and the excitement of new discoveries? AAS Nova and Astrobites are two resources freely available to the astronomy community and the general public, intended to help readers learn about the most recent research published across the field of astronomy. Both supported by the American Astronomical Society, these two daily astrophysical literature blogs provide accessible summaries of recent publications in AAS journals and on the arXiv. As both AAS Nova and Astrobites directly distill original studies, these resources constitute a critical bridge between astronomy researchers and educators, outreach practitioners, and the broader astronomy community. The material on these two websites — which includes a total archive of more than 2,500 research study summaries — is written accessibly while still providing access to the original sources and outcomes. As a result, AAS Nova and Astrobites can be used by educators and outreach practitioners to easily introduce the latest in astronomical research studies into classrooms and outreach events.
Formation of Terrestrial Planets
Kokubo, Eiichiro
In the standard formation scenario of planetary systems, planets form from a protoplanetary disk that consists of gas and dust. The scenario can be divided into three stages: (1) formation of planetesimals from dust, (2) formation of protoplanets from planetesimals, and (3) formation of planets from protoplanets. In stage (1), planetesimals form from dust through some instability of a dust layer or coagulation of dust grains. Planetesimals are small building blocks of solid planets. Planetesimals grow by mutual collisions to protoplanets or planetary embryos through runaway and oligarchic growth in stage (2). The final stage (3) depends on a type of planets. The final stage of terrestrial planet formation is giant impacts among protoplanets while sweeping residual planetesimals. In the present talk, I review the elementary processes of terrestrial planet formation and also discuss the origin of the diversity of terrestrial planets.
International Geophysical Projects and significance of Space and Earth Science to the World
Kolomiyets, Svitlana
The IAU's main objectives are to ensure progress in science and to unite efforts of scientists from different countries in this direction. From the very beginning, astronomy supplied a necessary celestial information for society regarding orientation in the space and time, as well as the structure of the Universe. Both in the history of development of science, and in the IAU centenary history we find gold pages of achievements connected with global interdisciplinary projects covering astronomy, geophysics and space science. Two of them are the International Geophysical Year 1957 (IGY) and the International Heliophysical Year 2007 (IHY). The IAU actively participated in the organization and realization of these projects. There was a specific influence of the IGY project to further development of science. This history page refers to the opening of the space age by launching the first artificial Earth satellite in accordance with the IGY program. The IGY was devoted to solar-terrestrial connections, the study of the solar activity and the Earth's ionosphere. The first scientific results were summed up at the 1958 IAU GA in Moscow. There is the United Nations Report for the IHY 2007 (Thompson et al. 2009). Here we give the information taken from it. The IHY had expanded our concept of “geophysics” into “heliophysics” to embrace other planets, interplanetary space, and the Sun itself. The IHY focused on the cross-disciplinary study of Universal Processes in the Solar system, observed in a variety of settings, providing global measurements of ionospheric and heliospheric phenomena. The efforts of the past half-century after IGY have brought us significant scientific advances, global scientific communication, and an extensive suite of spacecraft and observatories, which some call our “Great Observatory". The IHY program of Education and Public Outreach “Demonstrate the beauty, relevance and significance of Space and Earth Science to the World” was fully implemented.
Dwarf Galaxies at Low and High Redshift
Kong, Xu
The overwhelming majority of galaxies in the Universe are dwarf galaxies. But although they are important components in understanding galaxy evolution, these systems are typically too faint to be observed at high redshifts. However, we are able to obtain an unobscured view of early star formation and chemical enrichment in these galaxies at low redshift. In this talk, I will review some progress about high redshift dwarf galaxies, and then I will introduce some work based on local analog of high redshift dwarf galaxies. At the end, I will talk about the spectroscopic survey for compact galaxies using the LAMOST.
The Epoch of Reionization and the Cosmic Dawn
Koopmans, Leon
I will review recent progress in the study of the Epoch of Reionization and the Cosmic Dawn, specifically focusing on experiments trying to detect (or having claimed to have detected) the 21-cm signal of neutral hydrogen. I will discuss current experiments, their limits and challenges, as well as future instruments and objectives, in particular focussing on the SKA and HERA.
“Solar Irradiance” WG Chairs’ Report
Kopp, Greg
Business Meeting of Div.E and its Commissions, WGs
Magnetic field and accretion in the young eruptive star EX Lupi
Kospal, Agnes
While the Sun is a quiet and well-balanced star nowadays, during its first few million years it possessed a strong magnetic field and accreted actively. Theoretical models predict that under certain circumstances the interaction of a strongly magnetic star and its circumstellar disk may lead to short busts of increased accretion onto the star (d'Angelo & Spruit 2012). The observable examples of this phenomenon may be a group of young stars called EXors, named after the prototype EX Lupi, which show irregular brightenings due to elevated accretion. EX Lupi had its historically largest outburst in 2008. Spectroscopic evidence from the quiescent and outburst periods suggests that the mass accretion proceeds through the same magnetospheric accretion channels in both periods but with different mass flux (Sicilia-Aguilar et al. 2012). However, no information on the magnetic field of EX Lup can be found in the literature. Here, we explore the magnetic field structure of EX Lup using spectropolarimetric monitoring with the CFHT/ESPaDOnS. We detected strong and largely poloidal topology with a prominent cool polar cap and an accretion spot above it. We compare our results with numerical simulations, in order to check the applicability of the d'Angelo & Spruit model as an explanation of EX Lupi's accretion outbursts. If EX Lup is a good proxy for the proto-Sun, similar magnetic field-disk interactions and the resulting outbursts might have happened during the early evolution of the Solar System as well.
Discovering Circumbinary Planets with TESS
Kostov, Veselin
One of Kepler's most exciting breakthroughs was the discovery of circumbinary planets. Only about a dozen were found, however, leaving a vast gap in our understanding — similar to the state of exoplanet science when only hot Jupiters were known. TESS, and only TESS, will allow us to detect an order of magnitude more circumbinary planets using a new technique we have developed and tested: "the 1-2 punch". In addition to enchanting individual-case discoveries and their intriguing dynamics, our sample will enable statistical studies of occurrence rates, formation, and habitability (an astonishing ~30% of Kepler circumbinary planets are in the habitable zone).
The IRAM 30m telescope
Kramer, Carsten
The IRAM 30m telescope is operated in the 70 to 375 GHz range. Together with NOEMA, it provides a powerful means to study the millimeter universe at resolutions between 35" and less than 1". We will briefly describe the evolution of the 30m telescope over the past 30 years, to then highlight a couple of current science topics showing the strengths and potential of this observatory. On the way, we will discuss the current suite of instruments and data processing software. We will go from deep line surveys of nearby evolved stars to maps of high density tracingmolecules in nearby galaxies, to redshift searches in distant galaxies. And, we will go from recent mapping projects of the thermal dust emission of Galactic molecular clouds to high resolution maps of the Sunyaev Zel'dovich effect in galaxy clusters, and to VLBI observations at 1mm wavelength. We will continue with an outlook on large-scale maps with multi-beam heterodyne receivers and possible upgrades of the telescope.
The Transient Radio Universe
Kramer, Michael
Exploring the transient Universe at radio wavelengths offers a number of exciting possibilities. In contrast to most other wavelength bands, we detect a large number of photons that we can also easily digitize and manipulate. That allows us to obtain very high time resolution (nanoseconds), large fractional bandwidth (around 50% or more), and polarisation information. All of this helps in characterising the signals, or – even more exciting – discover signals of previous unknown origin, such as pulsars or recently Fast Radio Bursts. Even though the photons are of low energy, the are often produced in highly energetic processes and by compact objects. This allows us to utilize them for applications in fundamental physics, whether it is the study of gravity or super-dense matter, or cosmological applications. This talk will highlight some of the recent developments in the field, both addressing the observational aspects as well as recent discoveries and unsolved problems.
The Effelsberg 100-m radio telescope - the first homologous radio telescope
Kraus, Alex
The 100-m antenna of the Max-Planck-Institut für Radioastronomie in Bad Münstereifel-Effelsberg has been built between 1968 and 1971. It was the first radio telescope which was constructed following the principle of "homologous deformation", meaning that the telescope structure deforms under gravitational influence in a controlled way, i.e. leading from one parabolic shape to another (nearly) without degrading in performance.In this talk, I will present some of the design details of the Effelsberg telescope. The specifics of the telescope structure will be shown and I will demonstrate that the homologous design works very well.In 2006, the 100-m telescope was upgraded by a new subreflector with an active surface to overcome remaining deformations. The success of this project will be shown as well.
How to model the variations of the Ly-a spectral irradiance ?
Kretzschmar, Matthieu
We analyse the 43 spectrally resolved SOHO/SUMER observations of the H Ly-a (121.567nm) irradiance over Solar Cycle 23 and discuss how to extrapolate them in order to provide the community with Ly-a spectral irradiance profile at other times. We end up with a simple but performant model that computes the irradiance spectral profile from 1947 to present. Such a model is relevant for the study of many astronomical environments, from planetary atmospheres to interplanetary medium. This empirical model, which uses the Ly-a disk-integrated irradiance composite, reproduces the temporal variability of the observed profile and matches the independent SORCE/SOLSTICE spectral observations from 2003 to 2007 with an accuracy better than 10%.
Novel approaches to exoplanet life detection: Disequilibrium biosignatures and their detectability with the James Webb Space Telescope
Krissansen-Totton, Joshua
Upcoming ground- and space-based telescopes will characterize habitable exoplanets and look for atmospheric gases produced by life. Oxygen is a promising biosignature gas, but several hypothetical scenarios have been proposed for producing abiotic oxygen or its surrogate, ozone. Furthermore, even if these scenarios can be ruled out by other observations, there is no guarantee that oxygenic photosynthesis is a common metabolism. Oxygen biosignatures may be rare. Atmospheric chemical disequilibrium is potentially a more general biosignature. We have developed a quantitative metric for atmospheric disequilibrium and applied it to the Solar System planets. The biogenic disequilibrium in the modern Earth's atmosphere, which is mostly attributable to the coexistence of O2, N2, and liquid water, far exceeds the photochemically-produced disequilibria of the other Solar System atmospheres. We also applied our disequilibrium metric to the Earth through time, and found that on the anoxic Archean Earth (4-2.5 billion years ago), life maintained a predominant disequilibrium between CO2, CH4, N2, and liquid water. Such a combination of gases would not persist without significant replenishment of CH4 from the surface, which we have shown to be difficult to explain without life. This leads us to propose that the coexistence of CO2 and CH4 in the atmosphere of an ostensibly habitable exoplanet as a potential biosignature. The inference to life would be strengthened by the absence of atmospheric CO, which would be present if abiotic CH4 were outgassed and if no life were consuming CO. Finally, we evaluate the detectability of this new biosignature with the James Webb Space Telescope for nearby transiting planets such as the TRAPPIST-1 system.
Wind inhibition in HMXBs: the effect of clumping and implications for X-ray luminosity
Kritcka, J.
TBA
Commission C.E1 President's report
Krivova, Natalie
Business Meeting of Div.E and its Commissions, WGs
The implications of clustered star formation for (proto)planetary systems and habitability
Kruijssen, Diederik
Star formation is spatially clustered, such that radiative or dynamical interactions with neighbouring stars may disrupt (proto)planetary systems, leaving a lasting impact on their potential habitability. For decades, the commonly-adopted picture has been that all stars and planetary systems form in compact clusters that subsequently disperse, with important implications for the early evolution of (proto)planetary systems. I will present our group's recent theoretical and observational work showing that the classical picture is inaccurate. Our work reveals a broad range of formation environments, from dense stellar clusters to associations spanning tens of pc that formed in-situ. In the solar neighbourhood, we find that the vast majority of stars form in unbound associations, in which the interaction of (proto)planetary systems with neighbouring stars is extremely limited. However, the fraction of star formation occurring in compact clusters was considerably higher in the past, peaking at >50% in the young Milky Way. Focusing on those (proto)planetary systems that do form in clusters, I will proceed to show how their stability and potential habitability are affected by the host cluster. Both observations and theory show that the protoplanetary disc mass function is largely unchanged, but the disc radii are strongly truncated. This is driven by the single closest encounter with a neighbouring star, rather than the combined effect of many distant encounters. Together, these results demonstrate that the large-scale star formation environment is critical in determining the occupation probability of the habitable zone.
Quantitative Spectroscopy of the Young Stellar population of Star Forming Galaxies
Kudritzki, Rolf
The determination of the chemical composition of galaxies is crucial for investigating the formation and evolution of star forming galaxies and provides a powerful tool to constrain the effects of galactic winds and accretion from the cosmic web. In this regard stellar absorption line studies provide an attractive alternative to the standard techniques using the strong emission lines of HII regions. I will introduce a number of newly developed methods_x000D_ - multi-object spectroscopy of individual blue and red supergiant stars, the brightest stars in the universe at visual and NIR wavelengths,_x000D_ - NIR spectroscopy of super star clusters,_x000D_ - optical spectroscopy of the integrated light of stellar populations in the disks of star forming galaxies,_x000D_ and present results accumulated in the last two years. I will then discuss the scientific perspectives and potential of these methods for the use of ELTs.
Accounting for the protosolar environment
Küffmeier, Michael
Stars like the Sun predominantly occur clustered among other stars embedded in Giant Molecular Clouds. Contrary to models of individual stars forming due to the collapse of one isolated core, we account for the molecular cloud environment during the epoch of star and protoplanetary disk formation. Using state-of-the art zoom-simulations with the magnetohydrodynamical codes ramses, we investigate the accretion process of young stars that are embedded in such different environments during their first ~100 kyr after formation. Starting initially from a turbulent (40 pc)^3 Giant Molecular Cloud, efficient use of the Adaptive Mesh Refinement technique allows us to resolve the processes inside of protoplanetary disks with a resolution down to 0.06 AU, thus covering a range of spatial scales of more than eight orders of magnitude. We find that the accretionprocess of stars is heterogeneous in space, time and among different protostars with a tendency of more violent accretion for deeply embedded objects. As a follow-up, we evolve the embedded star-disk systems further in time with the new code framework dispatch to constrain the effect of infalling material before and during the onset of planet formation. Infalling material can trigger accretion bursts that are likely to be responsible for the large spread in luminosities observed for young stars. If the Sun underwent such violent accretion bursts in the past, the star might have heated the inner parts of the disk significantly during that time -- potentially leaving some trace in the meteoritic record. Finally, recent observations show stars hosting an inner and an outer disk misaligned with respect to each other. We study whether infall with different angular momentum can be responsible for the misalignment, and by analyzing the stability of misaligned systems in independent models, we speculate whether the Protosun could have hosted two misaligned disks at some point in its past.
Exploration of the binary asteroid 65803 Didymos by the payload of the Asteroid Impact Deflection Assessment (AIDA) mission
Küppers, Michael
The AIDA mission consists of three components: 1) NASA's Double Asteroid Redirection Test (DART) kinetic impactor that will hit the minor component of the double asteroid 65803 Didymos (Didymoon), to demonstrate the technology of asteroid deflection 2) A cubesat provided by ASI that will separate from DART hours before impact and take images of the Didymos system. It is based on the Argomoon cubesat that will be carried to the moon by NASA's exploration mission 1.3) ESA's Hera rendezvous mission that will investigate the Didymos system over several months, calibrating the impact experiment by an accurate characterization of Didymoon.We will present the investigations foreseen by the different payload elements: The DRACO imager on DART, based on the LORRI camera from the New Horizons mission, will take images of Didymoon just before impact, providing local context of the impact. The imager on the 6U ASI cubesat will capture Didymoon after the impact, potentially observing the impact crater. Hera will monitor the binary asteroid for several months, accurately measuring its dynamical state and completely mapping the surface with the Asteroid Framing Cameras (the flight spares of the Framing Cameras of the Dawn mission) and the European Lidar payload. Those instruments will also measure the mass of Didymoon, from the "wobble" motion of Didymos due to the gravity of Didymoon. Hera will additionally carry a cubesat, with the ASPECT visible and near-IR imaging spectrometer as the baseline payload. It will allow the spectral characterisation of the targets, testing hypotheses of the origin of the binary. Observations of fresh, unweathered material in the DART impact crater will uniquely determine the meteorite analogue of Didymos.Technological advances in recent years make planetary defence possible. The AIDA mission provides, for the first time, the opportunity to demonstrate our capability to deflect a hazardous asteroid.
Angular momentum of dwarf galaxies
Kurapati, Sushma
We use high-resolution HI observations and broad band photometry to measure the baryonic mass (M) and baryonic specific angular momentum (j) for 11 dwarf galaxies that lie in the Lynx-Cancer void. We find that the locus of void dwarf galaxies in the j-M plane is the same as that of dwarf galaxies in average density environments. However, all dwarf galaxies (i.e. regardless of environment) have significantly higher specific angular momentum than expected from the relation obtained for larger spiral galaxies. We find that this elevation in specific angular momentum occurs for dwarf galaxies with masses lower than 10$^{9.1}$ M$_{\odot}$. As the mass of the galaxy increases beyond 10$^{9.1}$ M$_{\odot}$, the baryonic specific angular momentum decreases and they tend to follow the relation obtained for the massive galaxies with zero bulge fraction. Interestingly, the mass threshold that we find, viz, 10$^{9.1} M$_{\odot}$ is very similar to the mass threshold below which galaxy discs start to become systematically thicker. We examine the possibility that both these effects, viz. the thickening of disks and the increase in specific angular momentum are results of feedback from star formation. Such feedback would preferentially remove the low angular momentum gas from the central parts of dwarfs (thus increasing the specific angular momentum of the system) and also inject mechanical energy into the system, leading to thicker discs. We find however, that the observed amount of observed star formation in our sample galaxies is insufficient to produce the observed increase in the specific angular momentum. It hence appears that other, as of yet not identified mechanisms, play a role in producing the observed enhancement in specific angular momentum. We speculate that cold accretion may be one possible mechanism.
Variations of the Chromospheric Ca K Intensity from Kodaikanal Archival Data
Kuttickat, Raju
The Calcium II K spectroheliograms from Kodaikanal Solar Observatory cover a period of over 100 years from 1907 to 2008. The Ca line is a good indicator of solar activity and surface flows. It is a proxy to the UV irradiance which is important in the Earth's climate_x000D_ variations. We report the temporal and latitudinal variations of the Chromospheric Ca II K line 3934 A intensity for over a century. A latitudinal drift towards the solar equator has been observed in the plots of intensity versus time. Possible reasons could be meridional_x000D_ flows, torsional oscillations, and equatorial migration of bright points. The results are expected to have implications on the flux transfer over the solar surface and irradiance modelling.
Dynamical evolution of asteroid pairs on close orbits
Kuznetsov, Eduard
We apply natural metrics (Kholshevnikov metrics) defined in the space of Keplerian orbits to search for asteroids in close orbits. First, we use as a metric the distance between two orbits in the five-dimensional space of Keplerian orbits. Then, we apply the distance in three-dimensional factor-space of positional orbital elements. We have identified new asteroid pairs with a possible common origin. Once the asteroid pairs candidates are identified, we analyze their dynamical evolution. We consider orbital evolution of two the tightest pairs: (63440) 2001 MD30 and (331933) 2004 TV14, and (355258) 2007 LY4 and (404118) 2013 AF40. To carry out high accuracy numerical simulation is necessary to take the Yarkovsky effect into account. We numerically integrated the orbits of pairs with backward in time (a time span of 20 kyr) with the code known as Orbit9. The numerical integrations were made taking the nominal orbits given by AstDyS database as initial conditions. Showed that the Yarkovsky effect is required to take into account accurately to carry out precise simulation of dynamical evolution of the asteroid pairs. Determination of physical and rotational parameters of asteroids is needed to solve this problem. This research is part of the Kourovka Asteroid Pairs Research (KASPAR) project that started in Kourovka Astronomical Observatory of the Ural Federal University in September 2017. The KASPAR project includes not only the observational side, involving astrometric and photometric observations of asteroid pairs on close orbits, but also its theoretical and computational counterpart involving numerical simulations of the dynamical evolution of such candidate pairs that take the Yarkovsky effect into account to calculate their proper orbital elements. The reported study was funded by RFBR according to the research project no. 18-02-00015.
Relationship between stellar and solar system organics
Kwok, Sun
From laboratory measurements, insoluble organic matter (IOM) in carbonaceous chondrites is known to consist of islands of aromatic rings linked by aliphatic chains. Similar structures are also seen in interplanetary dust particles and cometary dust. Stellar organics synthesized during the late stages of stellar evolution show strong emission bands and broad emission plateaus but the exact chemical structure of the carrier is not known. We report results of quantum chemical calculations of different classes of organic compounds and compare their theoretical spectra with astronomical spectra. We suggest that the chemical structure of circumstellar synthesized organics show similarities with solar system organics. The possibility of stellar origin of solar system organics will be discussed.
Mixed Aromatic Aliphatic organic nanoparticles (MAON) as carriers of unidentified infrared emission bands
Kwok, Sun
The unidentified infrared emission (UIE) phenomenon consists of a family of emission bands, broad emission plateaus, all superimposed on an underlying continuum. While the emission bands are almost certainly due to the stretching and bending modes of aromatic and aliphatic groups, the exact vibrational modes of these bands and the chemical structure of the carrier are not known. We report results of quantum chemistry calculations of large (>100 carbon atoms) molecules with mixed aromatic/aliphatic structures with the goal of identifying the origin of the UIE bands and explore various possibilities of the chemical nature of the UIE carrier.
Magnetic field structures in star-forming regions revealed by imaging polarimetry at multi-wavelengths
Kwon, Jungmi
Magnetic fields are ubiquitous in various scales of astronomical objects, and it is considered as playing significant roles from star to galaxy formations. However, the role of the magnetic fields in star forming regions is less well understood because conventional optical polarimetry is hampered by heavy extinction by dust. We have been conducting extensive near-infrared polarization survey of various star-forming regions from low- and intermediate-mass to high-mass star-forming regions, using IRSF/SIRPOL in South Africa. Not only linear but also circular polarizations have been measured for more than a dozen of regions. Both linear and circular polarimetric observations at near-infrared wavelengths are useful tools to study the magnetic fields in star forming regions, although infrared circular polarimetry has been less explored so far. In this presentation, we summarize our results of the near-infrared polarization survey of star forming regions and its comparison with recent submillimeter polarimetry results. Such multi-wavelength approaches can be extended to the polarimetry using ALMA, SPICA in future, and others. We also present our recent results of the first near-infrared imaging polarimetry of young stellar objects in the Circinus molecular cloud, which has been less studied but a very intriguing cluster containing numerous signs of active low-mass star formation.
Circumstellar dust, interferometry and resolved circumstellar envelopes"
Lagadec, Eric
With adaptive optics and optical/IR interferometry, we can now map circumstellar envelopes down to the dust formation radius, and even map the surface of the closest AGB stars. This can give us clues on the mass-loss mechanism for these stars, by detecting convective cells, shocks and dust formation. The morphology of the resolved envelopes can also give us indirect evidence for the presence of a companion that will affect the shaping of the envelope.In this review I will present the latest results obtained with instruments such as SPHERE/VLT, Gravity and AMBER at the VLTI.I will also show how MATISSE, the latest addition to the VLTI, should revolutionize our view of dust formation around these stars. With a resolution down to 3 mas in the mid-infrared L band and observations in the N band, we will map MOLSPHERE and the dust formation zone with the best accuracy ever achieved.
Exoplanet Atmosphere Characterization in the framework of the MIRI European Consortium Guaranteed time observations
Lagage, Pierre-Olivier
Thanks to its large collective area and its suite of instruments covering a wide range of wavelengths (0.6-28 microns), the James Webb Space Telescope (JWST) will revolutionize our knowledge about exoplanet atmospheres. The interest in observing exoplanet atmospheres goes well beyond the study of atmospheres very different from those found in the Solar system. Indeed, the molecular composition of giant exoplanet atmospheres can trace the planet's formation and evolution; the atmosphere of rocky exoplanets can host bio-signature gases, …In the talk, I will detail the program of characterization of exoplanet atmospheres to be conducted in the framework of the MIRI European Consortium (EC) Guaranteed Time Observations (GTO). MIRI is the mid InfraRed Instrument of the JWST; it covers the 5-28microns range. One hundred and ten hours, (about ¼ of the MIRI EC GTO used in cycle 1), will be devoted to the characterization of exoplanet atmospheres. All the MIRI observing modes will be used for the program. Imaging observations of five eclipses of the Trappist1 b exoplanet will be combined to detect, for the first time, the emission from an Earth sized exoplanet. The slitless Low Resolution Spectroscopic (LRS) mode will be used to determine the molecular composition of the atmosphere of two transiting exoplanets: WASP107 b, and HAT-P12 b. The good angular resolution of the JWST will make possible the characterization of exoplanets detected by direct imaging. The high contrast imaging mode of MIRI, making use of four quadrant phase mask coronagraphs, will be used to observe the giant planets orbiting HR8799, HD95086 and GJ504. For the exoplanets with not too high a star to planet contrast or with a relatively high angular separation from the host star, such as GU Psc b, observations will be performed in the slit LRS mode or, if bright enough, such as Ross 458 AB b, in the Medium Resolution Spectroscopic (MRS) mode.
Angular momentum evolution of galaxies: the perspective of hydrodynamical simulations
Lagos, Claudia
Until a decade ago, galaxy formation simulations were unable to reproduce the high angular momentum that is typical of galaxy disks. Improvements in the interstellar medium and stellar feedback modelling, together with advances in computational capabilities, have allowed the current generation of cosmological galaxy formation simulations to reproduce the diversity of angular momentum and morphology that is observed in local galaxies. In this review I will discuss where we currently stand in this area from the perspective of hydrodynamical simulations, specifically how galaxies gain their angular momentum, and the effect galaxy mergers and gas accretion have on this process. I will show simulation results which suggest that a revision of the classical theory of disk formation is needed, and will finish by discussing what the challenges for simulations are.
“The sky seems heavy with clouds.” Eddington, the president in WW2.
LAGUENS, Florian
Arthur S. Eddington (1882-1944) certainly was one of the world’s most famous astronomers during the interwar period. For thirty years he was the director of the Cambridge Observatory and taught astrophysics at Trinity College. When the International Astronomical Union was created in 1919, Eddington was chosen to preside over the first commission, devoted to Relativity. During the Cambridge General Assembly (1932) he delivered a series of lectures later published under the title The Expanding Universe. From 1925 to 1928 he was Vice-President of the Union. He was finally elected President at the concluding session of Stockholm General Assembly (1938), but his presidency was suddenly interrupted by his death in November 1944. Obviously, these years were dominated by the Second World War. In his first message as President, Eddington prophesised: “Here we have formed and renewed bands of friendship which will resist the forces of disruption.” Some unpublished letters also reveal what this sentence suggests: Eddington’s major concern for international co-operation.
How do external giant planets influence the evolution of compact multi-planet systems?
Lai, Dong
The Kepler mission has detected hundreds of compact multi-planet systems containing super-Earths and mini-Neptunes with orbital periods shorter than 200 days. These ``Systems of Tightly Packed Inner Planets'' (STIPs) bear little resemblance to our Solar System. Many STIPs have recently been found to have external giant planet or binary star companions. How are the architectures of the inner multi-planet systems influenced by the outer companions? What happens to the inner system when surrounded by an unstable system of outer giant planet companions? How common are misaligned (with respect to the spins of host stars) STIPs (like Kepler 56) produced? We will discuss our recent works in these areas, including both semi-analytic theory and numerical simulations. We will present relevant semi-analytic expressions or scaling relations that can be applied to a wide variety of systems, and we will confront theoretical/numerical results to observations to constrain the evolutionary history of compact multi-planet systems.
Observations of magnetic fields during the main accretion phase
Lai, Shih-Ping
It is widely believed that magnetic fields play an important role in the early stages of star formation (McKee \& Ostriker 2007, Crutcher 2012). Particularly, magnetic braking can remove angular momentum efficiently and has been widely considered in theoretical models of disk formation (Li et al. 2014, PPIV, and the reference therein). Early models assume that the magnetic field is aligned parallel to the rotation axis at the beginning of the disk formation simulations (e.g., Allen et al. 2003, ApJ, 599, 363). However, recent CARMA observations have shown that magnetic fields around protostars tend to be misaligned with the rotation axis, as traced by the outflow axis (Hull et al. 2013, 2014), although other (single-dish) observations found contrary results, especially on larger scales (Davidson et al. 2011, Chapman et al. 2013). In this talk, I will review recent observations of magnetic fields toward Class 0 sources that have shed some light on this important question.
Magnetic fields in spiral galaxies and radio galaxies
Laing, R.
TBA
Patterns to Scientific Internationalism: What Can a Comparative History of the IAU and the IUPAP Teach Us?
Lalli, Roberto
The IAU was founded on 28 July 1919 as one of the first institutional bodies in the highly politicized context of the post-WWI re-configuration of international scientific cooperation under the umbrella of newly established International Research Council. In many relevant aspects - - including its legal status, its administrative and organizational structure as well as its delicate relation to the political context - - the IAU could provide a model for the International Unions on different disciplines that will be created in the subsequent few years. On the other hand, each scientific discipline had its own traditional ways to conceive of, and implement, cooperation across national boundaries, which were deeply connected to its specific scientific needs. In spite of the common historical background, a bird-eye view at the parallel historical developments of the IAU and the IUPAP shows that they followed diverging trajectories in many respects.In the present paper, I will discuss a conceptual framework for a comparative history of these two international organizations. I will argue that this analysis will allow us address a number of crucial aspects that shaped the activities of these kinds of international scientific institutions through the 20th century. Among these, I will focus especially on the following points: the balance between political contexts and scientific needs; the transformative power of individual actions; the role played by international ideals, and more specifically which kind of internationalism was implicitly or explicitly embodied by the different institutions in different hsitorical contexts; the different relationships with the International Research Council and, later, ICSU; the different ways to address and solve problems connceted to the national and individual memberships; and finally, the different roles of the commissions in shaping the respective fields of enquiry.
Constraining the early evolution of terrestrial planets by reproducing elemental ratios
Lammer, Helmut
Compositional variations between the solar nebula, chondrites and the chemical abundances of the terrestrial planets provide evidence that some sort of elemental and isotopic fractionation should have taken place early in the history of the solar system. During the disk-embedded phase, early in the evolutionary history of the solar system, protoplanetary cores are believed to accumulate hydrogen gas and to form thin planetary H2-envelopes. According to the “Grant-Tack” scenario, those protoplanetary cores (proto-Earth and proto-Venus) should have accumulated a size of 0.5-0.75 Earth- and Venus-masses, respectively, until the solar nebular evaporated. Afterwards, EUV-driven hydrodynamic escape started to slowly erode the accumulated hydrogen-envelopes of the proto-planets. In addition, constant bombardment of impacting material, delivered further material to growing proto-Earth and -Venus. Lighter elements, such as potassium (K) compared to uranium (U), as well as isotopes, as for example 36Ar compared to 38Ar, or 20Ne compared to 22Ne can escape easier from proto-Earth and proto-Venus due to H-drag from a nebula-captures hydrogen-envelope compared to a magma ocean related outgassed steam atmosphere, whereas heavier elements and isotopes cannot be dragged away that easily. Simulations of the hydrodynamic escape of the accumulated hydrogen envelope around proto-Earth and proto-Venus show that this effect can explain initial compositional variations between the terrestrial planets and the solar nebula. It is also shown that in the case of the Earth delivery of chondritic material is necessary to reproduce the observed fractionations. These model results are also supporting the Grant-Tack scenario, and are in agreement with 182Hf-182W chronometric fast accretion scenarios of the Earth with a late Moon-forming giant impact.
O-rich LPVs in the X-shooter Spectral Library
Lancon, Ariane
The X-shooter Spectral Library contains, among others, the spectra of a few hundred luminous red stars, of which many are LPVs. The VLT/X-shooter spectra extend from the blue end of the stars' energy distributions to 2.5 micrometers in the near-infrared, and have a spectral resolving power of about 104. We will present a summary of the properties of these spectra, compare their statistical properties with those of previous collections, confront them with available models, and discuss their relevance for stellar population studies.
The Milky Way Galactic Center: Highlights from the Core of our Galaxy
Lang, Cornelia
In addition to harboring a supermassive black hole at its very core, the Galactic Center is one of the most physically extreme environments in the Galaxy. Dense and massive molecular clouds are abundant in this region, yet star formation is not as active as one might expect. In addition, radio observations have revealed a population of synchrotron-emitting filaments that provide insight on the magnetic field strength and configuration in this unique region of the Galaxy. Physical interactions may be occurring at the interfaces of dense molecular clouds and the interstellar magnetic filaments. I will review recent observational results over the full electromagnetic spectrum -- from radio wavelength measurements through high energy observations -- that reveal the detailed and complex astrophysics in the nearest galactic nuclei.
Magnetizing the Intergalactic Medium during Reionization
Langer, Mathieu
Increasing evidence suggests that cosmological sheets, filaments and voids may be substantially magnetised. The origin of magnetic fields in the the Intergalactic Medium is currently uncertain. It seems now well known that non-standard extensions to the physics of the Standard Model are capable of providing mechanisms susceptible of magnetising the Universe at large. Much less well known is the fact that standard, classical physics of matter-radiation interactions possesses actually the same potential. I will discuss a magnetogenesis mechanism based on the exchange of momentum between hard photons and electrons in an inhomogeneous Intergalactic Medium. Operating in the neighbourhood of ionising sources during the Epoch of Reionization, this mechanism is capable of generating magnetic seeds of relevant strengths on scales comparable to the distance between ionising sources. In addition, summing up the contributions of all ionising sources and taking into account the distribution of gas inhomogeneities, I will show that this mechanism leaves the IGM, at the end of Reionization, with a level of magnetization that might account for the current magnetic fields strengths in the cosmic web.
Structure and Evolution of AGB stars: Remaining Challenges
Lattanzio, John
The basics of the structure and evolution of AGB stars have been known for some time. Yet a reliable quantitative understanding remains elusive. There are two main reasons for this. 1) the AGB phase is the last nuclear phase of low and intermediate mass stars, and hence uncertainties in the earlier evolution produce uncertainties in the structure of AGB models; 2) the complex physics occurring in AGB stars provides its own limitations on the models. In this presentation I will outline the main physics responsible for our lack of reliable models, and also discuss possible ways beyond the current impasse.
American Astronomers in Belgium, 1919: A Photo Collection
Lattis, James
The U.S. delegation to the July 1919 International Research Council meeting in Brussels included Joel Stebbins, then professor of astronomy and observatory director at the University of Illinois. He attended as a member of the executive committee appointed by the National Research Council. Stebbins, an avid photographer, documented the travels of their party as the American astronomers attended the meeting and later toured devastated towns, scarred countryside, and battlefields only recently abandoned. Published reports of the meeting afterward attest to the impression left on the American visitors, and the photographs by Stebbins give us a glimpse through their own eyes. These photographs, recently discovered in the University of Wisconsin Archives and never before publicly seen, will be presented along with some commentary on their significance for the International Astronomical Union, which began to take shape at that 1919 meeting.
Star Formation and Molecular Gas in Extremely Metal-poor Galaxies: Insights from the Thermal Balance in the Neutral Gas
Lebouteiller, Vianney
The lack of detection of cold molecular gas in blue compact dwarf (BCD) galaxies is at variance with their intense star-formation episode. In particular, CO, often used a tracer of H2 through a conversion function, is selectively photodissociated in dust-poor environments. On the other hand, a potentially large fraction of H2 is expected to reside in the so-called CO-free gas, where it could be traced by neutral gas infrared cooling lines [CI], [CII], or [OI]. Although the fraction of CO-free gas to total molecular gas is expected to be relatively large in metal-poor galaxies, a definite evidence is still lacking because of the difficulty in associating cooling lines with any given heating mechanism. The main issue at stake is to understand the role of molecular gas in the star formation process.I will first show that the heating mechanism in the neutral gas cannot be dominated by the photoelectric effect on dust grains below a threshold metallicity due to a low abundance of dust and polycyclic aromatic hydrocarbons. I will then present results from a study on the dwarf galaxy IZw18 (~2% solar metallicity) recently published in Lebouteiller et al. (2017). Optical and infrared lines are used to constrain the physical conditions in the HII region + HI region within a consistent photoionization and photodissociation model. We show that the HI region is entirely heated by a single ultraluminous X-ray source with important consequences on the applicability of [CII] to trace the star-formation rate and to trace the CO-free gas. We derive stringent upper limits on the size of H2 clumps that may be detected in the future with JWST and IRAM/NOEMA. We also show how the nature of X-ray sources can be constrained through their signatures in the interstellar medium and through the use of state-of-the-art models. I will conclude by proposing that star formation may be quenched in extremely metal-poor dwarf galaxies due to X-ray photoionization.
Dust dynamics in adaptative-mesh-refinement codes : application to protostellar collapses.
Lebreuilly, Ugo
The interstellar medium is essentially composed of gas and a small amount of dust, with an average dust-to-gas ratio of 1% and a grain size distribution well approximated by power laws (Mathis et al, 1977). In dense regions, such as the molecular clouds or the prestellar cores, these properties are not well constrained because dust dynamics is particularly affected by pressure and density gradients. Most of current studies do not consider a possible variation of dust-to-gas in these objects, supposing that dust is frozen in the gas. I will present an implementation of dust and gas mixture dynamics in the adaptive-mesh-refinement code RAMSES (Lebreuilly & Commerçon, In. prep.). The method use the monofluid formalism in the diffusion approximation. I will show the validation tests of our implementation, i.e., the dustyshock, dustywave or dusty-diffusion tests (Laibe & Price, 2011). Finally I will present a first application to protostellar collapse and disk formation.
AGB stars in Gaia Data Release 2
Lebzelter, Thomas
Gaia Data Release 2 (DR2; April 25, 2018) provides astrometric, photometric, and spectroscopic data for more than a billion stars - among them many AGB stars. As part of DR2 the light curves of several hundreds of thousand variable stars, including many Long Period Variable (LPV) candidates, are made available. The publication of the light curves and LPV-specific attributes in addition to the standard DR2 products offers a unique opportunity to study AGB stars.In this contribution, we present the first results for AGB stars based on the analysis of the Gaia data performed after their release. The analysis focuses on the AGB properties in connection to stellar distances, sky distribution and variability behaviour.
Cold gas in protoclusters : star formation efficiency and gas kinematics of star forming galaxies in z=2.5 protocluster
Lee, Minju
We report on cold gas observations toward star-forming galaxies associated with one of the protoclusters found at z=2.5, of two CO lines (CO(3–2) and CO(4–3)), and dust continuum at 1.1 mm using ALMA, aiming for understanding galaxy evolution during the early epoch of cluster formation. From the CO(3-2) line and dust continuum detection, we measure the global cold gas content of seven massive (>4x1010 Msun) star-forming galaxies. The measured cold gas mass is on average similar to that of star forming galaxies in general fields, with the gas mass fraction fgas ~ 0.5, but a positive correlation between stellar mass and star formation efficiency is found within the stellar mass range of log Mstar=[10.64, 11.30], suggesting a potential role for environment at z=2.5. Higher angular resolution images in CO(4-3) are obtained at 0.4 arcsec, toward the subsamples of the CO(3-2)-detected galaxies for further investigation. This allows us to model the gas kinematics on two disk-like galaxies with S/N>~8, located in a high local density region. The best-fit models on CO(4-3) data cubes suggest that the overall kinematic parameters (e.g., rotation velocity, velocity dispersion) are similar to those found in the comparable field disk-like galaxies, so are the (baryonic) Tully-Fisher relation and the specific angular momentum, though there is a tension in the model. Potential mergers are also found in the protocluster. We discuss the physical interpretation of the discovery of both disk-like galaxies and mergers in the protocluster, from the theoretical standpoint. In conclusion, we find no significant difference in cold gas properties between protocluster and field galaxies at z~2.5 on average, though there are tentative trends that need to be confirmed with a finer beam. This is one of the first studies ever made toward protoclusters using cold gas, which still lacks statistical significance, and thus, future observations are necessary to investigate more galaxies.
AI-generated magnetogram of the Carrington event in 1859 and the estimation of its Dst value
Lee, Harim
We apply an image-to-image translation model, which is a popular deep learning method based on conditional Generative Adversarial Networks (cGANs), to the generation from sunspot drawings to the corresponding magnetograms. For this, we train the model using pairs of sunspot drawing from Mount Wilson Observatory (MWO) and their corresponding SDO/HMI line-of-sight magnetogram from 2012 to 2013. We test the model by comparing pairs of actual SDO/HMI magnetogram and the corresponding AI-generated one in 2014. Our results show that bipolar structures of the AI-generated magnetograms are consistent with those of the original ones and their unsigned magnetic fluxes are well correlated with those of the original ones with a good correlation coefficient of 0.78. Using this model with the Carrington sunspot drawing, we successfully produce AI-generated magnetogram and estimate unsigned magnetic fluxes. Using several empirical relationships (magnetic flux vs. CME speed, CME speed vs. ICME speed, and ICME speed vs. Dst) in 23 and 24th solar cycle, we conjecture the Dst value of the Carrington event, about -1,100 nT, which is between two estimations of Bombai magnetometer.
The Role of the IAU Gleaned from Oral Histories of Individuals Involved in Astronomy in South Africa
Leeuw, Lerothodi
In light of the IAU Centenary Symposium, we will use selected data from our on-going project on oral histories of individuals involved in astronomy in South Africa to probe the role of the IAU in careers of the participants of the project and also in astronomy in South Africa in general. The project is to conduct, archive and showcase the recording of histories of individuals involved in astronomy in South Africa; and, in it we will include specific questions that help us learn about the role of the IAU in careers of the participants of the projects and also in astronomy in South Africa in general. The work provides an opportunity to elucidate not only the role of the IAU itself but also other professional bodies in scientific careers, innovation and development of individuals and their broader scientific and civic communities.
Empirical Constraints on the Evolution of X-ray Binaries from Chandra Deep Fields and Local Galaxies
Lehmer, Bret
Recently, we have found, in the Chandra Deep Field-South, that the emission from X-ray binary (XRB) populations in galaxies evolves significantly with cosmic time, most likely due to changes in the physical properties of galaxies like star-formation rate, stellar mass, stellar age, and metallicity. These observations have shown that the X-ray emissivity from HMXBs likely outpowered active galactic nuclei in the z > 6-8 Universe, implicating HMXBs as an important source of heating to the IGM at z ~ 10-20. Furthermore, these observations provide an important benchmark for self-consistently modeling the processes leading to the gravity-wave emitting populations now detected by aLIGO and VIRGO. I will review results from the Chandra Deep Fields and provide new results based on Chandra and multiwavelength observations of local spiral galaxies that allow us to extract XRB X-ray luminosity function histories. I will conclude by discussing next steps in developing a comprehensive empirical model for how XRB populations evolve with age, depending on the physical properties of their host stellar populations.
Fundamental physics constraints from testing the stability of the fine-structure constant with the ELTs
Leite, Ana Catarina
The increased collecting area of the ELTs will bring fainter high-z targets within the reach of high-resolution ultra-stable spectrographs, thus enabling a new generation of precision consistency tests, including tests of the stability of nature's fundamental couplings. For example, the stability of the fine-structure constant can be tested by looking into metal absorption lines produced by the intervening clouds along the line of sight of distant quasars.I will discuss the performance that can be expected from the ELTs in testing the stability of the fine-structure constant, based on the early ESPRESSO observations, and present some comparative forecasts of the impact of these measurements for representative models of fundamental physics and cosmology.
The CHEWIE survey of exoplanet transmission spectra
Lendl, Monika
During planetary transit, stellar light is filtered through an exoplanet's atmosphere, revealing the planet's atmospheric properties as wavelength-dependent absorption features. Transmission spectra obtained though spectroscopic observations of transits are today providing key information on the composition and structure of planetary atmospheres. Further, as observations become more numerous, they allow us to investigate the diversity of exoplanetary atmospheres.While transmission spectra have long been dominated by space-based observations, recent improvements in instrumentation and analysis techniques have placed ground-based observatories at the forefront of exoplanet characterization.I will present CHEWIE (Clouds, Hazes and Elements vieWed on gIant Exoplanets), a survey of exoplanet transmission spectra with 8m-class ground-based telescopes. I will give an overview on the survey and present recent results. The latter include the first transmission spectrum of WASP-103b, one of the most massive (1.5 M_J) and hottest (2500 K) planets characterized so far using transmission spectroscopy, and the transmission spectra of several planets in the Neptune to Saturn mass range.
Simulating imagery of the near and distant universe with MICADO at the ELT
Leschinski, Kieran
K. Leschinski, O. Czoske, G. Verdoes Kleijn, W. Zeilinger, J. Alves, W. Kausch, R. Köhler, M. Mach, N. PrzybillaSimCADO is the data simulation package for the MICADO near-infrared camera for ESO's Extremely Large Telescope. SimCADO allows the user to "observe" their chosen on-sky target as it would be seen through the MICADO/ELT optical train. The python package has been developed as part of the current instrument design effort for MICADO. It is open source and free to use.SimCADO simulates effects along the full photon path - from the source, through the atmosphere, telescope and instrument, on to the detector - for both of the MICADO imaging modes. The functionality to model MICADO's spectrographic mode will be added in the near future. We have validated the accuracy of the simulated images against archive data from HAWK-I. Images produced by SimCADO will be used internally by the Data Flow team to develop the MICADO data flow architecture, and by the Science team to consolidate the key science drivers for the MICADO project.Here I will present an overview of the SimCADO package as well as a series of examples of how the software can be used to study the feasibility of future observation campaigns with MICADO and the ELT with regards to several of the big open questions in astronomy. Examples include: resolving the structure of the IMF outside the Milky Way, directly observing the proper motions of stars in the cores of globular clusters which may contain intermediate mass black holes; imaging gravitational lensing systems; observing time delays of sub arcsecond multiply imaged quasars, and resolving the structure of high-redshift galaxies.
A Commensal Radio Astronomy FAST Survey (CRAFTS)
Li, Di
Having achieved ‘first-light’ right before the opening ceremony on September 25, 2016, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is now kept busy with commissions. We have devised a survey plan, namely, the commensal radio astronomy FAST survey (CRAFTS) to utilized the full sensitivity of FAST, while minimizing the complexities in operating the system. The 19-beam L band focal plan array will be rotated to specific angles and taking continuous data streams while the surface shape and the focal cabin stay fixed. CRAFTS will cover the northern sky in about 220 full days. In testing CRAFTS, we have already started to discover new radio counterparts to Fermi sources. Our aim is to obtain data for pulsar search, HI (neutral hydrogen) galaxies, HI imaging, and radio transients, simultaneously, through multiple backends. These data sets could be a significant contribution to all related fields and remain relevant for decades.
A Commensal Radio Astronomy FAST Survey (CRAFTS)
Li, Di
Having achieved ‘first-light’ right before the opening ceremony on September 25, 2016, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is now kept busy with commissions. We have devised a survey plan, namely, the commensal radio astronomy FAST survey (CRAFTS) to utilized the full sensitivity of FAST, while minimizing the complexities in operating the system. The 19-beam L band focal plan array will be rotated to specific angles and taking continuous data streams while the surface shape and the focal cabin stay fixed. CRAFTS will cover the northern sky in about 220 full days. In testing CRAFTS, we have already started to discover new radio counterparts to Fermi sources. Our aim is to obtain data for pulsar search, HI (neutral hydrogen) galaxies, HI imaging, and radio transients, simultaneously, through multiple backends. These data sets could be a significant contribution to all related fields and remain relevant for decades.
Secular Dynamics on TNOs and Planet Nine Interactions
Li, Gongjie
The existence of Planet Nine has been suggested to explain the pericenter alignment of extreme trans-Neptunian objects. However, the underlying dynamics involving Planet Nine, test particles and Neptune is rich, including secular interactions, mean motion resonances and close encounters between the objects and Neptune/Planet Nine. It remains unclear which dynamical processes dominate the alignment of orbits, and the detailed dependence of the alignment on the orbital parameters of the outer planet is poorly characterized. We investigate the secular interactions between an eccentric outer perturber and objects starting in a near-coplanar configuration. We find that secular dynamics leads to clustering in the longitude of pericenter relative to planet Nine ($\Delta \varpi \sim 0^\circ$ and $180^\circ$) for large semi-major axis, small pericenter distance objects ($a\gtrsim 250$ AU, $30<r_p<80$ au).="" for="" the="" low="" inclination="" particles,="" initial="" orbital="" orientations="" of="" anti-aligned="" ($\delta\varpi\sim="" 180^\circ$)="" population="" is="" primarily="" also="" ($\delta\varpi_0="" \sim="" with="" respect="" to="" planet="" nine's="" orbit.="" on="" other="" hand,="" $\delta="" \varpi="" 0^\circ$="" more="" likely="" be="" ejected="" through="" non-secular="" processes="" (close="" encounters="" and="" chaos="" due="" overlap="" mean="" motion="" resonances).="" high="" objects="" ($60^\circ<i<120^\circ$),="" secular="" interactions="" leads="" clustering="" in="" \varpi$="" around="" $90^\circ$="" $270^\circ$,="" as="" well="" longitude="" ascending="" node="" argument="" pericenter="" ($\delta\omega="" 90^\circ~\&~270^\circ$="" $\delta\omega="" 0^\circ~\&~180^\circ$).="" contrast,="" we="" see="" no="" $\omega$="" population:="" this="" inconsistent="" current="" observations="" tnos,="" therefore="" excluding="" possibility="" a="" massive="" nine="" ($\sim="" 10{\rm="" m_{\oplus}}$,="" $\sim="" 500$="" au="" eccentricity="" 0.6$)="" close="" plane="" ecliptic.<="" p="">
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Carbon Nano Dust in the Interstellar Medium: Nanodiamonds, Graphene, and Carbon Nanotubes
Li, Aigen
Carbon is exclusively formed in the hot interiors of stars through the fusion reactions of three alpha particles (i.e., helium nuclei) and expelled into the interstellar medium (ISM) through stellar outflows and/or supernova explosions in the late stages of stellar evolution. As the fourth most abundant element in the universe and due to its unique property to form three different types of chemical bonds through sp1, sp2, and sp3 hybridizations, carbon can be stabilized in various multi-atomic structures with different molecular configurations (i.e., allotropes), including amorphous carbon, graphite, diamond, polycyclic aromatic hydrocarbon (PAH), fullerenes, graphene, and carbon nanotubes (CNTs).In this presentation I will focus on nanodiamonds, graphene, and CNTs. I will present (1) our DFT calculations of the electronic and vibrational transitions of graphene and CNTs as a function of carbon atoms (NC), (2) the infrared (IR) emission spectra of nanodiamonds, graphene and CNTs which are stochastically excited by single photons in the ISM, and (3) the possible contribution of nanodiamonds, graphene and CNTs to the UV interstellar extinction. The model-calculated UV extinction and IR emission spectra of nanodiamonds, graphene and CNTs will then be compared with the astronomical observations, allowing us to constrain the abundances of these nano species in the ISM. The possible connection of graphene and CNTs with the mysterious diffuse interstellar bands (DIBs) will also be examined.
How Supernovae-driven Hot Outflows Regulate Circumgalactic Medium
Li, Miao
The circumgalactic medium (CGM), where cosmic inflows interact with feedback-driven outflows, provides critical clues for galaxy formation. The physics of feedback remains a bottleneck to theoretical modeling. In this talk I will introduce our numerical simulations of CGM impacted by supernovae (SNe)-driven hot outflows. Using outflow models that are directly obtained from our small-box high-resolution simulations, we study the large-scale evolution of the outflows in the CGM. The volume-filling hot outflows carry the majority of the energy and metals produced by SNe, and can travel to > 100 kpc from Milky Way-like galaxies. I will talk about how galaxy potentials, existing halo gas, and SF activity affects the impact of outflows. I will also discuss how the model can be compared against future X-ray observations and signals of the Sunyaev-Zel’dovich effect.
The Hot Baryons Contained in the Circum-Galactic Medium Around Massive Isolated Spiral Galaxies
Li, Jiang-Tao
The baryon content around local galaxies is observed to be much less than is needed in Big Bang nucleosynthesis. Simulations indicate that a significant fraction of these “missing baryons” may be stored in a hot tenuous circum-galactic medium (CGM) around massive galaxies extending to or even beyond the virial radius of their dark matter halos. Previous observations in X-ray and Sunyaev-Zel'dovich (SZ) signal claimed that ~(1-50)% of the expected baryons are stored in a hot CGM within the virial radius. The large scatter is mainly caused by the very uncertain extrapolation of the hot gas density profile based on the detection in a small radial range (typically within (10-20)% of the virial radius). In this talk I will report results from stacking XMM-Newton observations of six local isolated massive spiral galaxies from the CGM-MASS sample. We find that the mean density profile can be characterized by a single power law out to a galactocentric radius of ~200kpc (or ~130kpc above the 1-σ background uncertainty), about half the virial radius of the dark matter halo. We can now estimate that the hot CGM within the virial radius accounts for (8+-4)% of the baryonic mass expected for the halos. Including the stars, the baryon fraction is (27+-16)%, or (39+-20)% by assuming a flattened density profile at r>130kpc. We conclude that the hot baryons within the virial radius of massive galaxy halos are insufficient to explain the “missing baryons”.
All Hands On Deck: Understanding Astrophysical Jets from Supermassive Black Holes via Observation, Theory, Simulation and Laboratory Experiment
Li, Hui
We present 3D relativistic and non-relativistic MHD simulations of AGN jets in galaxy cluster environments to study the morphology, energetics and polarization signatures of such jets and lobes. In particular, we investigate the following issues: 1. On the global jet/lobe scales, what magnetic field configurations are constrained by observations in radio and X-rays in order to explain the morphology and polarization properties? 2. On the global jet/lobe scales, what kind of jets (hydromagnetic or magnetic tower) can survive the “weather” of the background ICM? 3. On the pc-kpc scales, will the current-driven kink instability destroy the jets? What are the likely processes that impact the energy conversion from magnetic fields to kinetic flow and/or relativistic particles? 4. How laboratory magnetized plasma jet experiments are helping us to understand the jet stability and energy conversion? We present observational and numerical modeling results that argue for a relatively small amount of energy dissipation along the jets until most of the jet energy is deposited in lobes and their interaction with the background ICM. Future prospects of progress in simulations will be discussed as well.
Haumea and its icy family
Licandro, Javier
The dynamical identification and physical characterization of numerous collisional families in the asteroid main belt (MB) has had a remarkable impact on the understanding of the formation and evolution of asteroids. It proved the importance that collisions had in the region. Collisions have also had a fundamental role in the evolution of the trans-neptunian objects (TNOs), but the dynamical identification of a collisional family in the trans-neptunian belt (TNb) is considerably more difficult than in the MB.Up to now, only one collisional family has been identified in the TNb, the Haumea family. Haumea is not only one of the fourth largest TNOs, is the largest member of a group of TNOs that present very similar dynamical and spectroscopical properties that appears to be fragments of the ejected ice mantle of Haumea.In this work I will summarize the very unique know properties of Haumea including: a surface covered almost by water ice; a high albedo; a very elongated shape; a rapid rotation; two known moons; and a ring. I will also summarize the properties of its icy family members. I will finally discuss the implications of this asteroid family, the feasibility of identifying new families in the TNb, and the perspective of future studies using Earth-based thirty meter class telescopes (like the ELT and TMT), and the James Webb Space Telescope.
Lumpy stars and bumpy winds
Liljegren, Sofie
The wind-driving process of AGB stars are thought to be a two-step process: first matter is levitated by shock waves, and then accelerated outwards by radiation pressure on newly condensed dust grains._x000D_ When modelling such a wind, spherical symmetry is usually assumed. This is in stark contrast with recent observations, which shows significant non-spherical structures. Giant convection cells cover the surface of the star, and matter is being ejected into the atmosphere where it condenses into lumpy dust clouds._x000D_ We try to quantify the differences between what is simulated in the 3D star-in-a-box models (CO5BOLD code) and the 1D dynamical atmosphere and wind models (DARWIN code). The impact of having a non-spherical star on the wind properties is also investigated._x000D_ We find that the inherent non-spherical behaviour of the AGB stars might induce a dust-driven weak wind already early on the AGB, and including that the star is anisotropic when simulating the wind leads to large time variation of the density of the outflow. Such variations could possibly be observable as small-scale structures in the circumstellar envelope.
A Tough Egg to Crack
lim, jeremy
A Tough Egg to CrackThe sculpting of the Egg proto-planetary nebula has so far defied a coherent explanation. This nebula exhibits prominent bipolar lobes, multiple equatorial outflows, and quasi-circular arcs imprinted on an approximately spherically-symmetric wind from the progenitor AGB-star. Here, we use observations at high angular resolutions to study gas and dust at wavelengths ranging from centimeter (VLA), millimetre (ALMA), to near-IR and optical (HST) wavelengths so as to determine the position of the previously mass-losing AGB star and present post-AGB star that illuminates the nebula. We find that: (i) dust close to the centre comprises elongated blobs aligned with the wall of the northern lobe, none of which coincide with the central illuminating star; (ii) gas near the systemic velocity traces an expanding, hollow, spherical shell - a last burp from the AGB star - disrupted by the bipolar outflows; (iii) the position of the post-AGB star as previously determined from polarized scattered light coincides closely with the centre of the hollow shell, the position of the previously mass-losing AGB star. We argue that the sculpting of the Egg proto-planetary nebula requires two stellar companions to the post-AGB star, and present a working model for how all the intricate structure of this nebula may be produced.
First results on the cluster galaxy population from the Subaru Hyper Suprime-Cam survey: Brightest cluster galaxies, stellar mass distribution, and active galaxies
Lin, Yen-Ting
The unprecedented depth and area surveyed by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled us to construct and publish the largest distant cluster sample out to z~1 to date. In this study of cluster galaxy evolution from z=1 to z=0.3, we investigate the stellar mass assembly history of brightest cluster galaxies (BCGs), evolution of stellar mass and luminosity distributions, stellar mass surface density profile, as well as the population of radio galaxies. Our analysis is the first high redshift application of the top N richest cluster selection, which is shown to allow us to trace the cluster galaxy evolution faithfully. Over the 230 deg2 area of the HSC-SSP footprint in 2017, selecting the top 100 clusters in each of the 4 redshift bins allows us to observe the buildup of galaxy population in descendants of clusters whose z~1 mass is about 2x1014Msun. Our stellar mass is derived from a machine-learning algorithm, which is found to be unbiased and accurate with respect to the COSMOS data. We find very mild stellar mass growth in BCGs (about 35% between z=1 and 0.3), and no evidence for evolution in both the total stellar mass--cluster mass correlation and the shape of the stellar mass surface density profile. We also present the first measurement of the radio luminosity distribution in clusters out to z~1, and show hints of changes in the dominant accretion mode powering the cluster radio galaxies at z~0.8.
Public Outreach & Information Management
Lindberg Christensen, Lars
TBA
Gaia DR2 astrometry
Lindegren, Lennart
The main astrometric properties of Gaia DR2 will be described: random errors, systematic errors (to the extent that they are known), spatial correlations.
Mixing of Condensible Constituents with H/He During Formation of Giant Planets
Lissauer, Jack
We present the results of simulations of the early stages of growth of giant planets that incorporate the mixing of light gases with denser material that enters the planet as solids. We find that silicates and gas begin to intimately mix when the planet becomes roughly as massive as Earth because incoming silicates can then fully vaporize if they arrive in the form of planetesimals or smaller. Most of the rocky material accreted by a giant planet becomes part of its extensive envelope, although the vast majority of silicates remain within the lower portions of the envelope that contains < 1% H/He by mass when the growing planet is several times as massive as Earth. The inner zone of primarily supercritical fluid silicates and the outer layers dominated by H/He are separated by a narrow region with a steep composition gradient that inhibits convection. Nonetheless, this lower envelope substantially affects the planet's growth and structure because it retains accretion energy as heat and thus is far larger than a cold, solid core of the same mass. The simulations are ongoing and more extensive and detailed results will be presented in Vienna.
The China Crisis
Liu, Xiaowei
The so-called China crisis, well documented in History of the IAU by A. Blaauw and in Under the Same Starry Sky History of the IAU by C.-Q. Fu and S.-H. Ye refers to the withdrawal in 1961 of the People’s Republic of China (PRC) from the Union. The crisis stemmed from the admission by IAU, amidst strong protest from PRC and some other member states, Republic of China (ROC) to the Union, creating the so-called “Two Chinas” or “One China, one Taiwan” problem. The crisis directly led to the absence of China mainland astronomers from the stage of international astronomical collaboration and exchange, and was only solved two decades later. The solution, accepted by all the parties involved, is that China is to have two adhering organizations, with China mainland astronomers represented by the Chinese Astronomical Society located in Nanjing (China Nanjing) and China Taiwan astronomers represented by the Academia Sinica located in Taipei (China Taipei). The denominations, “China Nanjing” and “China Taipei” represent the IAU official resolution and should be used in all IAU events. The crisis was a painful lesson in the 100-year history of growth and development of the Union. Yet, with its eventual solution, the Union emerged stronger, upholding its spirit of promoting astronomical development through international collaboration of astronomers from all regions and countries, regardless of the political systems, religions, ethnics, genders or astronomical development levels. The resolution of the crisis, combined with the continuing improvement of relation across the Taiwan Straight, has benefited astronomers on both sides of the Straight, stimulated and facilitated collaborations amongst them as well as with the international community at large. Four decades after the crisis, Chinese astronomy research and education, on both sides of the Straight, are posed to make major contributions to the world astronomy development and to the whole humanity.
New Planets from K2
Livingston, John
The NASA K2 mission has continued to yield large numbers of new planet discoveries in its second year. We have carried out a systematic program of transit detection and ground-based follow-up, resulting in a sample of well-vetted planet candidates. The K2 photometry along with constraints from follow-up spectroscopy and high resolution imaging have enabled us to statistically validate a large fraction of these systems. Of particular interest are a number of planets with bright host stars which are amenable to detailed characterization via radial velocity mass measurement and transmission spectroscopy, multiplanet systems, and small planets receiving Earth-like insolation. By conducting follow-up transit photometry with Spitzer, we have also refined the ephemerides of many interesting systems, which helps to ensure the feasibility of future atmospheric studies (i.e. with JWST).
Magnetized Protoplanetary Disks
Lizano, Susana
Protoplanetary disks are expected to form as a result of the gravitational collapse of magnetized rotating dense cores. I will discuss the structure and emission of models of magnetized accretion disks irradiated by the central star expected to form in this process. The mass-to-flux ratio is a critical parameter for their structure. This ratio will be determined observationally in the near future with radio interferometers like ALMA and VLA. I will also discuss the modeling of millimeter observations of the disk around the young star HL Tau.
Magnetized Protoplanetary Disks
Lizano, Susana
Protoplanetary disks are expected to form as a result of the gravitational collapse of magnetized rotating dense cores. I will discuss the structure and emission of models of magnetized accretion disks irradiated by the central star expected to form in this process. The mass-to-flux ratio is a critical parameter for their structure. This ratio will be determined observationally in the near future with radio interferometers like ALMA and VLA. I will also discuss the modeling of millimeter observations of the disk around the young star HL Tau.
Insights into the Fermi Bubbles from 21cm HI Observations
Lockman, Felix
The Fermi Bubbles are regions of hot gas extending many kpc above and below the Galactic center that were formed through energetic events associated with the Galactic nucleus (1). The Bubbles are traced by very faint emission across the electromagnetic spectrum implying that they contain non-thermal particles as well as hot, ~107 K thermal gas. The origin of the bubbles, as well as their energetics and lifetime, is uncertain. There are also uncertainties in the size and structure of the bubbles near the Galactic plane, where confusion with foregrounds is severe.Spectroscopic studies offer the advantage of a kinematic removal of foregrounds and the ability to trace material in the bubbles directly. In 21cm HI observations the Bubbles appear as voids in the extended HI layer (2, 3). And within these voids is a population of HI clouds apparently entrained in the outflowing nuclear wind (4). These clouds allow the Bubbles to be studied close to their source and establish limits on energetics. The Green Bank Telescope was recently used to survey the inner Galaxy for neutral clouds entrained in the nuclear wind, and has detected more than 100 such objects (5). Together with information from UV absorption lines on directions that pierce the Fermi Bubbles (e.g., 6, 7), a picture emerges which implies an outflow luminosity > 3 x 1040 ergs/sec over the last 10 Myr, and a cold-gas mass flow into the Bubbles of ~0.1 M?/yr. REFERENCES: 1. Su, M. et al. 2010, ApJ, 724, 10442. Lockman, F.J. 1984, ApJ, 283, 903. Lockman, F.J. & McClure-Griffiths, N.M. 2016, ApJ, 826, 2154. McClure-Griffiths, N.M. et al. 2013, ApJL, 770, L45. Di Teodoro, E.M. et al. 2018, ApJ (in press)6. Fox, A.J. et al. 2015, ApJ, 799, L77. Savage, B.D. et al. 2017, ApJS, 232, 25
Simulations of the polarized sky of the SKA
Loi, Francesca
The advent of the Square Kilometre Array (SKA) will have an unprecedented impact on the study of the cosmic magnetism. An all-sky survey at 1.4 GHz will be proposed for the SKA with the aim to produce an accurate map of the Rotation Measure (RM) based on a enormous number of radio sources spread over cosmological distances. The spatial density of these radio sources will be such that we will obtain a RM grid with several hundreds of sources per squared degree. In order to be prepared to use this RM grid, we need to understand if and how we will be able to invert the information encoded in the grid to reconstruct the strength and the structure of large scale magnetic fields. In this talk, I will present an original numerical approach that is able to produce full-Stokes realistic images of the radio sky that we would observe with the SKA. Among the several uses of this tool, I will show the results concerning the study of magnetic fields in galaxy clusters based on the application of the Faraday RM Synthesis on simulated data.
Modelling the Formation of Extrasolar Comet Clouds
Loibnegger, Birgit
In the last years observations of absorption lines varying on short time scales in spectra of stars accumulate. Scientists refer to these findings as features caused by objects evaporating material on their orbit when they come close to the star and thus call them comets in exoplanetary systems -- exocomets. This theory is based on the knowledge about the Solar System._x000D_ The aim of our dynamical investigation is to find a statistical model for the scattering of small bodies which shows the most probable whereabouts of these objects after the gravitational interaction with the planets._x000D_ _x000D_ The setup includes a star, a Jupiter-like planet and a disk of planetesimals (testparticles). As a consequence of the migration of the gas giant planetesimals are scattered either inward or outward. The outward scattered objects will form analogues to the Kuiper belt respectively the Oort Cloud in our Solar System. The created reservoirs are different depending on the initial conditions of the planetesimal disk and the migration of the Jupiter-like planet. Semi-major axis, eccentricity, perihel, aphel, inclination and orbital period after 4byr of integration of each testparticle are measured and statistics are made by comparing the outcomes of the computations with different acting forces applied -- as there are gravitational influence of the galactic tide and passing stars. Additionally the influence of the migration of the gas giant on the outcome of the scattering process is examined._x000D_ In order to apply the described method to extrasolar planetary systems we start with different masses of the central star and different initial conditions for the planet (mass, orbit...) as given from observations._x000D_ The gained knowledge can be used to generate a general model for the formation of cometary reservoirs in extrasolar systems with respect to the system architecture which can be used to predict the location of cometary reservoirs in extrasolar systems.
Plenary Session: 100 years of Astronomy, Astrophysics and Cosmology
Longair, Malcolm
Astronomy, astrophysics and cosmology have changed out of all recognition over the last 100 years. The IAU has provided an essential means of fostering international collaboration including times of international tension. Developments will be highlighted which have profoundly changed our understanding and insight into the workings of our Universe.
Titan’s Global Geology from Cassini
Lopes, Rosaly
We investigate the geologic history of Titan through mapping and analyzing the distribution of observed geomorphologic features using a combination of Cassini data collected by RADAR,VIMS (Visual and Infrared Mapping Spectrometer), and ISS (Imaging Science Subsystem). Determining the spatial and superposition relations between geomorphologic units on Titan leads to an understanding of the likely time evolution of the landscape and gives insight into the process interactions that drove its geologic history. We have used all available datasets to extend the mapping initially done by Lopes et al. (2010, Icarus, 205) and Birch et al. (2017, Icarus, 282) to a global map at 1:800,000 scale in all areas covered by the RADAR Synthetic Aperture Radar (SAR). We show how we are extending the map to regions not covered by SAR, to produce a 1:1,500,000 scale map compatible with USGS standards. We use the map to infer the stratigraphic relations among Titan’s different terrain types, which in turn allows us to establish the sequence of geologic processes that have shaped the satellite’s surface.
Report of the "Astronomical heritage in danger" working group
López, Alejandro Martín
In this presentation we will talk about the elaboration of the list of astronomical heritage sites in danger that sustains this working group. We will also discuss the progress made since the previous general assembly. The difficulties and problems encountered and the future prospects will be analyzed.
Cultural astronomy perspectives on "development"
López, Alejandro Martín
This presentation seeks to contribute to the essential synergies with social sciences, which are necessary in order to carry out any consistent attempt of “astronomy for development”. Based on the perspective of cultural astronomy and ethnographic experience, we will focus on the implications of the concept of development for local communities and indigenous people.The category of “development” and its implications has been the subject of intense debate in the social sciences. The various conceptions about it that have been generally put into play in concrete projects have had serious problems in actually dialoguing with local interests and socio-cultural diversity. In the case of astronomy, its links with “development” are strongly related to education, economy and heritage. In the present work we will explore some of the implications and challenges that arise in these three fronts.In the field of astronomical education we face the challenge of thinking about the relationship between the “western academic astronomy” and other astronomical traditions. We discuss the relevance of cultural astronomy in building real dialogues.In terms of economy processes we need to attend to local alternatives to the western ideas of “development”, and to the political implications of these concepts. In particular, we need to pay attention to the impact of big astronomical international projects in the local dynamics.Finally, in the past decades, heritage has been transformed into a new language in which conflicts of the most varied nature are expressed and became a way of legitimizing and giving visibility to the claims of different subaltern groups. Knowledge and astronomical practices are involved in this dynamic, especially after the joint initiative of UNESCO and IAU in 2009 to promote “astronomical heritage”.In this way we hope to contribute in the making of cultural astronomy a positive tool for the respect of diversity and the attention to the demands of subaltern groups.
Resolving the dusty torus of active galactic nuclei with ELTs
Lopez Rodriguez, Enrique
The obscuring material surrounding the central engine of active galaxies is the cornerstone of the unified model. Until now, interferometric observations have been the sole technique to resolve the dusty ‘torus’ of the nearest AGN. These observations have provided crucial information about the size (< 10 pc) and the emission and distribution of dust at infrared and (sub-)mm wavelengths. The achievable milli-arcsecons (< 1pc) resolution observations in the 2-13 µm wavelength range by the ELTs will for the first time produce single-dish resolved images of the dust emission in the torus of AGN. We present HyperCube of AGN Torus models (HyperCAT), and tools to simulate images of the torus emission as they will be observed by the next generation of ELTs. Our model images are based on the CLUMPY torus models. HyperCAT produces 2D images of torus emission in the range of 1-1000 µm for a given set of telescope and instrument configurations and AGN properties. It takes into account the telescope’s PSF, detector pixelisation, and desired noise characteristics. We will present the tool and our analysis of the resolvability and dust emission morphologies of nearby AGN Tori with ELTs.
Plenary Session: Galaxy evolution with the new giant telescopes
Lotz, J.
TBA
Galactic Nuclei Studies with JWST
Luetzgendorf, Nora
Following its launch in 2019, the James Webb Space Telescope (JWST) will be the only facility that is sensitive over the entire near- and mid-infrared spectral range (1 - 28 µm). This wavelength range is extremely rich in spectral diagnostics, both for stellar populations and all components of the interstellar medium (dust as well as neutral, atomic, and ionised gas). Given the diffraction-limited 6.5m aperture of JWST, all of these components can be studied on scales on scales of a few pc in nearby galaxies. In particular, studies with the integral-field spectroscopy modes of the MIRI and NIRSpec instruments promise a wealth of new insights into a number of important issues related to the formation and growth of super-massive black holes, and their effect on the host galaxy. In this talk, I will summarize a number of open issues, and highlight the JWST capabilities that can be used to address them.
Stellar activity and winds shaping the atmospheres of Earth-like planets
Lüftinger, Theresa
Planets orbiting young, active stars are embedded in an environment that is far from being as calm as the present solar neighbourhood. They experience the extreme environments of their host stars, which cannot have been without consequences for young stellar systems and the evolution of Earth-like planets to habitable worlds. Stellar magnetism and the related stellar activity are crucial drivers of ionization, photodissociation, and chemistry. Stellar winds can compress planetary magnetospheres and even strip away the outer layers of their atmospheres, thus having an enormous impact on the atmospheres and the magnetospheres of surrounding exoplanets. Modelling of stellar magnetic fields and their winds is extremely challenging, both from the observational and the theoretical points of view, and only ground breaking advances in observational instrumentation and a deeper theoretical understanding of magnetohydrodynamic processes in stars enable us to model stellar magnetic fields and their winds – and the resulting influence on the atmospheres of surrounding exoplanets – in more and more detail. We have initiated a national and international research network (NFN): 'Pathways to Habitability - From Disks to Active Stars, Planets to Life', to address questions on the formation and habitability of environments in young, active stellar/planetary systems. In this presentation, we will discuss the work we are carrying out within this project and focus on how stellar evolutionary aspects in relation to activity, magnetic fields and winds influence the erosion of planetary atmospheres in the habitable zone. We will present recent results of our theoretical and observational studies based on Zeeman Doppler Imaging (ZDI), field extrapolation methods, wind simulations, and the modeling of planetary upper atmospheres.
Detection of missing baryons with thermal and kinetic Sunyaev-Zeldovich effect
Ma, Yin-Zhe
Previous studies of galaxy formation have shown that only 10 per cent of the cosmic baryons are in stars and galaxies, while 90 per cent of them are missing. In this talk, I will present three observational studies that coherently find significant evidences of the missing baryons. The first is the cross-correlation between the kinetic Sunyaev-Zeldovich maps from Planck with the linear reconstructed velocity field. We find significance (4.6 sigma) detection of the peculiar motion of gas on Mpc scales, for which we can reconstruct the baryon fraction. The second study is the cross-correlation between the thermal Sunyaev- Zeldovich effect with gravitational lensing map and we detect the cross-correlation for 13 sigma with RCSLenS and Planck data. The third study is to stack the pairs of luminous red galaxies and subtract the halo contribution, which leads to the detection of gas within filaments. These studies directly show the evidence of missing baryons outside the virial radius of galaxy clusters.
From NVSS RM Catalogue to Future Polarisation Surveys
Ma, Yik Ki
With RM measured towards 37,543 polarised sources, the NVSS RM Catalogue (Taylor et al. 2009) is widely exploited in studies of the foreground magneto-ionised media. However, due to limitations imposed by observations in survey mode in the narrowband era, the results are inevitably affected by various systematic effects. With new JVLA broadband spectro-polarimetric observations at L-band, we set off to observationally test the robustness of the NVSS RM Catalogue, in anticipation of current and future polarisation surveys such as VLASS, POSSUM, and the eventual SKA. Our pointed observations, in conjunction with simulations, allow us to estimate the impact of off-axis polarisation leakage on the measured RM values. We show that off-axis leakage terms must be properly calibrated in future all-sky polarisation surveys, in order to obtain high fidelity polarisation information from sources down to low fractional polarisation. In addition, we explore the time domain of the polarised sky by utilising broadband data obtained at two epochs (separated by three years) to investigate time variabilities in polarisation, including that in Faraday depths.
Modeling the Interactive Lives of Stars
MacLeod, Morgan
During this talk, I will describe how stellar dynamics intertwines with stellar evolution and hydrodynamics to determine the properties of interactions between stars and black holes in galactic centers. In galactic centers, stars trace dangerously wandering orbits dictated by the combined gravitational force of a central, supermassive black hole and all of the surrounding stars. These interactions can partially or completely disrupt stars through tidal forces, and they can fuel accretion-driven flares of the black hole. Disruptions of stars across the evolutionary spectrum give rise to transients with different characteristic timescales, luminosities, and wavelengths. I will focus on how the properties of these transients can reveal the demographics of black holes and the stellar populations that surround them.
Overview of the ISM properties of Dwarf galaxies: consequences of the low metallicity and star formation activity
Madden, Suzanne
Recent space missions together with the wealth of optical, radio and millimetre observations of dwarf galaxies are allowing us to construct a picture of their InterStellar Medium (ISM). Their low mass, often prominent star formation activity, and metal-poor ISM have a striking impact on the physical processes that take place to shape the structure of their ISM. The properties of the gas and dust associated with molecular clouds, photodissociation regions and ionised phases of dwarf galaxies bring a very different picture of the ISM, compared to their more metal rich counterparts. In spite of the fact that molecular gas is infamously difficult to detect in dwarf galaxies, star formation persists.I will review what we know to date of the properties and structure of the molecular clouds, photodissociation regions, ionised gas phases and star formation activities that are gleaned from various surveys at various size scales in dwarf galaxies, and how they compare/contrast to more massive, dusty galaxies, thus setting the stage for our session on ISM and star formation in dwarf galaxies.
Establishing Extreme Dynamic Range with JWST: Decoding Smoke Signals in the Glare of a Wolf-Rayet Binary
Madura, Tom
Dust is a key ingredient in the formation of stars and planets. However, the dominant channels of dust production throughout cosmic time are still unclear. With its unprecedented sensitivity and spatial resolution in the mid-IR, the James Webb Space Telescope (JWST) is the ideal platform to address this issue by investigating the dust abundance, composition, and production rates of various dusty sources. In particular, colliding-wind Wolf-Rayet (WR) binaries are efficient dust producers in the local Universe, and likely existed in the earliest galaxies. Our planned JWST observations of the archetypal colliding-wind binary WR 140 will study the dust composition, abundance, and formation mechanisms. We will utilize two key JWST observing modes with the medium-resolution spectrometer (MRS) on the Mid-Infrared Instrument (MIRI) and the Aperture Masking Interferometry (AMI) mode with the Near Infrared Imager and Slitless Spectrograph (NIRISS)._x000D_ Our planned observations will investigate the dust forming properties WR binaries and establish a benchmark for key observing modes for imaging bright sources with faint extended emission. This will be valuable in various astrophysical contexts including mass-loss from evolved stars, dusty tori around active galactic nuclei, and protoplanetary disks. We are committed to designing and delivering science-enabling products for the JWST community that address technical issues such as bright source artifacts in addition to testing optimal image reconstruction algorithms for observing extended structures with NIRISS/AMI.
Statistical properties of starspots on solar-type stars and their correlation with flare activity
Maehara, Hiroyuki
Recent high-precision photometry by Kepler mission found thousands of “superflares” on solar-type stars. Most of superflare stars show quasi-periodic brightness modulations caused by the rotation of the star with starspots. We analyzed the statistical properties of starspots on solar-type stars and their correlation with the flare activity by using the data from the Kepler mission. The analysis shows that the fraction of stars showing large-amplitude rotational variations, which are thought to be the signature of the large starspots, decreases as the rotation period increases. Assuming simple relations between temperatures of spot and photosphere and between spot area and lifetime, we compared the size distribution of large starspot groups on slowly-rotating solar-type stars with that of sunspot groups observed during recent 140 years. The size distribution of starspots shows the power-law distribution and the size distribution of relatively large sunspots lies on this power-law line. This result implies that the large starspots with the area of >2-3x104 MHS (micro solar hemispheres; 1 MSH=3x1016 cm2) could appear once in a few hundred years on the slowly-rotating solar-type stars like our Sun. We also found that the frequency-energy distributions for flares originating from spots with different sizes are the same for solar-type stars with superflares and the Sun and the frequency of flare with a given energy is roughly proportional to the spot area. These results suggest that the magnetic activity on solar-type stars with superflares and that on the Sun are caused by the same physical processes.
Supernovae
Maguire, Kate
Extremely Large Telescopes (ELTs) will provide the ability to study supernovae at higher redshifts than currently possible. These observations will be crucial for precision cosmological measurements using Type Ia supernovae, as well as for dramatically increasing our understanding of massive star formation in the early Universe through the study of stellar explosions. In this talk, I will discuss the latest predictions for studies of both thermonuclear and core-collapse supernovae at high redshifts with ELTs. I will also highlight how future observations will target the explosions of the first generation of stars, and provide key constraints on star formation at high redshift.
Jet-driven outflows of cold gas in radio galaxies: the case of 3C293
Mahony, Elizabeth
While it is generally accepted that the evolution of galaxies and their central SMBH are strongly linked, the feedback mechanisms responsible for this are less clear. Outflows are often thought to be driven by quasar winds or massive starbursts, but an increasing number of studies have shown that radio jets could also be responsible. In this talk I will present recent results on jet-driven outflows of gas in the nearby radio galaxy 3C293. Using spectral line observations from the JVLA we detect fast outflows of neutral hydrogen of up to ~1200 km/s being driven by the radio jet at a distance of 0.5 kpc from the central core of the AGN. Follow-up IFU observations tracing the ionised gas revealed broader linewidths up to 12 kpc from the nucleus, indicating that the disturbed kinematics extend beyond the high surface brightness radio structures of the jets. These results highlight the need for deep optical and radio observations at high resolution to properly characterise the interaction between radio jets and the surrounding gas. The upcoming SKA-pathfinders will allow us to map the interaction between radio jets and the cold gas in galaxies out to further distances than ever before, shedding light on how jets impact their environment at a crucial point in the lifecycle of radio galaxies.
Spectroscopic observations of the kilonova associated with GW170817
Malesani, Daniele
The rapid localization of the optical counterpart of the merging neutron star event allowed a plethora of spectroscopic observations of the highest quality, leading to the first secure identification of a kilonova. These spectra contain novel information on the explosion physics and on the composition of the ejecta, including the likely identification of r-process elements. I will review the existing studies and present the results while waiting for the forthcoming start of the LIGO/Virgo O3 observing run in late 2018.
On the eve of 100-year anniversary of the IAU Commission 19 "Rotation of the Earth"
Malkin, Zinovy
IAU Commission 19 began in 1919 with the birth of the IAU at the Brussels Conference, where Standing Committee 19 on Latitude Variations was established as one of 32 standing committees. At the first IAU General Assembly in 1922, the Standing Committee became Commission 19 "Variation of Latitude." In the beginning, the main topic of the Commission was investigation of polar motion. Later, its activities included observations and theory of Earth rotation and connections between Earth orientation variations and geophysical phenomena. As a result, in 1964 at the XIIth IAU General Assembly the Commission was renamed "Rotation of the Earth." The investigation of the Earth rotation is primarily based on observations of natural and artificial celestial objects. Therefore, maintenance of the international terrestrial and celestial reference frames, as well as the coordinate transformation between the frames including improvement of the model of precession/nutation have always been among the primary Commission topics. In 1987, the IAU through Commissions 19 and 31 "Time" established, jointly with the International Union of Geodesy and Geophysics, what is now known as the International Earth Rotation and Reference System Service (IERS). Commission 19 continues to work developing methods to improve the accuracy and understanding of Earth orientation variations and related reference systems and frames, as well as theoretical studies of Earth rotation. In 2015, Commission 19 was renewed as Commission A2 "Rotation of the Earth" continuing Commission 19's functions and linking the astronomical community to other scientific organizations such as the International Association of Geodesy, International VLBI Service for Geodesy and Astrometry (IVS), International GNSS Service (IGS), International Laser Ranging Service (ILRS), and International DORIS Service (IDS).
India's Participation in IAU over the Years
Mallik, Dipankar
India was a British colony when the International Astronomical Union was born in 1919. Official matters were channelled through The Royal Society, London, the adhering organization of the United Kingdom to the Union. The total membership from the country was less than 10 until after WW II. In 1946, India formally joined IAU and the National Institute of Sciences of India (NISI) was given the status of the adhering organization. Till the nineteen sixties, the membership grew rather tardily but soon the situation changed what with the exciting new discoveries in astronomy, and its rapid growth in the country. In 1967, M K Vainu Bappu, the then Director of the Kodaikanal Observatory, was elected a Vice-President of the Union. During 1976 -1979, Vainu Bappu was the President of Commission 12. In 1979, he was elected the President of IAU for the triennium 1979-1982 and V Radhakrishnan and Govind Swarup were Presidents during the same period of the Commision 34 (Interstellar Matter and Planetary Nebulae) and Commission 40 (Radio Astronomy) respectively. The membership had shot up to 100. Since then more and more Indian astronomers participated in the activities of the Union and assumed important official roles. In 1985, the General Assembly of the Union was held in New Delhi. The Assembly was dedicated to the memory of Vainu Bappu who had initiated the process of inviting the Union to hold its GA in India.Vainu Bappu had passed away in 1982, on the eve of the General assembly at Patras that he was to preside over. In 1985 too, the first IAU Symposium and IAU Colloquium were held in India. A few years later the Sixth Asia-Pacific Regional IAU Meeting was held in Pune. During the last two decades, the engagement of the Indian astronomers with IAU has grown more and more. Today the membership stands at well over more 200. _x000D_
Working Group on Star Names (WGSN)
Mamajek, Eric
The IAU has organized working groups over the past century which havesuccessfully standardized nomenclature for various categories ofcelestial objects under scientific study, and formulated guidelinesfor assigning alphanumeric designations for objects outside the solarsystem (including stars). However, the recent IAU initiative to adoptproper names for exoplanets and their host stars (NameExoWorlds)exposed a surprising gap in IAU oversight: the IAU had no catalogue ofofficial, unique proper names for stars, nor any mechanism forofficially proposing and adopting such names. Common star names like"Fomalhaut" had no official status with the IAU, and the bright starsoften had numerous cultural aliases and spelling variations. The IAUDivision C Working Group on Star Names (WGSN) was organized andapproved by the IAU EC in May 2016. WGSN has been working tocatalogue historical and cultural proper names for stars, developguidelines for, and adopting, unique names for stars of scientific andhistorical value for the IAU (seehttps://www.iau.org/science/scientific_bodies/working_groups/280/).The WGSN serves the IAU by helping preserve the astronomical past(intangible cultural heritage in the form of celestial nomenclature),and serving the present and future (cataloguing unique, standardizedproper names for stars in anticipation of future IAU naming ofexoplanetary systems). The WGSN has adopted over 300 names over thepast two years, compiled into an IAU Catalogue of Star Names(https://www.iau.org/public/themes/naming_stars/#table). Beyondstandardizing the names of many of the Latinized Arabic star names incommon use, the WGSN recently included many names from otherastronomical traditions (e.g. Chinese, Hindu, Aboriginal, Polynesian,etc.) into this catalogue. We discuss the progress of the WGSN overits first two years and its plans for the next triennium.
Probing the nature of dark matter with Theia: a mission concept for ultra precise differential astrometry
MAMON, Gary
Space-astrometry is a widely transversal discipline, touching most areas of Astronomy. Theia is a space-astrometry mission concept dedicated to differential astrometric measurements in targeted fields reaching 60 times the accuracy of Gaia: from hundreds of nano-arcseconds to 10 micro-arcseconds, in targets from magnitudes 5 to 20. Such astrometric precision is due to a highly stable, continuously monitored, payload concept that relies on state-of-the-art materials and mechanical design, a stable optical design, multiple robust metrology systems and an overall optimized mission architecture. I will describe how, with proper motions and parallaxes achieved with such ultra-sharp astrometry, Theia should achieve breakthroughs on the nature of Dark Matter, the equation of state of neutron stars and possible quark stars, and a complete sample of habitable-zone Earth-like planets in the nearest stars, with a focus on the cusp/core dark matter debate in dwarf spheroidal galaxies.
Spatial distribution of the fullerene C60 in the planetary nebula IC418
Manchado, Arturo
We have studied the spatial distribution of the fullereneC60 in the planetary nebula IC 418, and compare with the dust and PAH emission structure.A ring-like extended structure (at a distance of 6300 AU) is seen at all IR wavelengths.However, after continuum subtraction the dust continuumemission at 9.8 micron , peaks close to the central star while the broad 9-13 micron emissiontogether with the PAH emission show a clear ring-like extended emission.On the contrary the C60 17.4 micron, emission is mainly located at the northeast,extending from the central star to the outer regions of the nebula.This 17.4 micron fullerene emission may be a photo-product of the 9-13 micron carrier or containperhaps contribution from other fullerene-based species like hydrogenated fullerenes.
Plenary Session: Gravitational wave astronomy
Mandel, I.
TBA
Commission C.E3 President's report
Mann, Ingrid
Business Meeting of Div.E and its Commissions, WGs
Formation and interaction of nano dust in planetary debris discs
Mann, Ingrid
The circum-stellar planetary debris discs are produced from planetesimals in a similar way as asteroids and comets produce the interplanetary dust. The debris disc dust is typically observed by thermal emission in mid-infrared and located at large distance from the star, comparable to the solar system’s Kuiper belt. Similar to the solar system, it is produced by dust-dust collisions, but with higher rates and the dust clouds are denser. Most of the small dust particles are pushed away from the vicinity of the star by radiation pressure. Some stars show, however thermal emission spectra that suggest the existence of nm-sized dust relatively close to the star (i.e. hot debris discs). This presentation addresses the formation of this dust in the collisional fragmentation process, the dynamics including electromagnetic forces and the thermal emission brightness. The findings are compared to the dust in the solar system, especially in the vicinity of the Sun, the region that will be explored with the space missions Solar Orbiter and Parker Solar Probe.
Formation and interaction of nano dust in planetary debris discs
Mann, Ingrid
The circum-stellar planetary debris discs are produced from planetesimals in a similar way as asteroids and comets produce the interplanetary dust. The debris disc dust is typically observed by thermal emission in mid-infrared and located at large distance from the star, comparable to the solar system’s Kuiper belt. Similar to the solar system, it is produced by dust-dust collisions, but with higher rates and the dust clouds are denser. Most of the small dust particles are pushed away from the vicinity of the star by radiation pressure. Some stars show, however thermal emission spectra that suggest the existence of nm-sized dust relatively close to the star (i.e. hot debris discs). This presentation addresses the formation of this dust in the collisional fragmentation process, the dynamics including electromagnetic forces and the thermal emission brightness. The findings are compared to the dust in the solar system, especially in the vicinity of the Sun, the region that will be explored with the space missions Solar Orbiter and Parker Solar Probe.
Magnetism in the SKA Era
Mao, Sui Ann
The unprecedented sensitivity, angular resolution and broadband coverage of Square Kilometre Array polarimetric observations will allow us to address many long-standing mysteries in cosmic magnetism science. In this talk, I will present new and ambitious science topics that SKA polarization data will enable in the next decade. Several new concepts and their required observations in areas of Galactic, extragalactic astrophysics, as well as cosmology will be highlighted.
The formation channels of gravitational wave source progenitors
Mapelli, Michela
What are the formation channels of merging black holes and neutron stars? The first two observing runs of Advanced LIGO and Virgo give us invaluable insights to address this question, but a new approach to theoretical models is required, in order to match the challenges posed by the new data. In my talk, I present a new model to study the progenitor stars of merging systems, by considering both dynamical and isolated binary evolution within a cosmological framework. I discuss the impact of stellar winds, core-collapse and pair instability supernovae on the formation of compact remnants in both isolated and dynamically formed binaries. Finally, I show that dynamical processes, such as the runaway collision scenario and the Kozai-Lidov mechanism, leave a clear imprint on the demography of merging systems.
Rings around B[e] Supergiants
Maravelias, Grigoris
Massive stars affect strongly the insterstellar medium through their intense stellar winds and their rich chemically processed material as they evolve. In specific short-lived transition phases (e.g. B[e] Supergiants, Luminous Blue Variables, Yellow Hypergiants) the mass-loss becomes more enhanced and usually eruptive. This leads to the formation of a complex circumstellar environment, which is not always well understood. To improve our knowledge on these phases we examined the structures found around the B[e] supergiants for a sample of Galactic and Magellanic Cloud sources. Using high-resolution optical and near-infrared spectra, we examine a set of key emission features ([OI], [CaII], CO bandheads) to trace their physical conditions and kinematics in their formation regions. Assuming Keplerian rotation of the circumstellar material we find that each B[e] Supergiant is surrounded by a unique distribution of single and/or multiple equatorial rings. Moroever, we find that these structures seem to be more stable and long-lived around single stars rather than binaries that show significant spectroscopic and photometric variability.
A new approach to binary population synthesis
Marchant, Pablo
In the last decade binary evolution has been recognized as a fundamental aspect in the evolution of massive stars, with more than half of them expected to undergo interaction with a companion. Current developments in the observations of transient events, X-ray binaries and gravitational wave detections require efficient and accurate methods to model stellar populations in order to understand their origin. Previous approaches to population synthesis have mostly relied on calculations of single star evolution and simple algorithms to account for binary interaction. Despite their flexibility and computational efficiency, these 'rapid' methods cannot precisely model important phases of evolution, such as thermal timescale mass-transfer, delayed dynamical instability, and partial stripping of stellar envelopes. In this talk I will present a new population synthesis code that relies on full calculations of binary evolution and interaction using the MESA stellar evolution code, together with a new implementation of common envelope evolution. This tool significantly enhances the accuracy of population synthesis models, while remaining computationally efficient to explore uncertainties such as birth kicks on compact objects. I will discuss the applications of this new tool to model different types of supernovae, X-ray binaries and merging compact objects.
"Hemelliggaam or The attempt to be here now": an art-meet science project inspired by the history of Astronomy in South Africa
Marchetti, Lucia
The Hemelligaam project (or “Heavenly Body” in the Afrikaans language) aims to portray in a novel way the historical deep connection that exists between the South African people, the Land and the Sky.In this particular age, astronomy is a powerful transformation driver for South Africa, both for its people and the landscape, and it often embodies aspirations for socio-economic enfranchisement and societal development at different levels. With this project we aim to record and show these transformations by exploiting the eyes, ears and stories of the communities living in the areas that are most directly and profoundly touched by this astronomy-driven transformation of the country.In 2017 the South African National Research Foundation (NRF) has established the “Roadmap for the History of Astronomy in South Africa” aimed to identify ways to preserve the historical astronomical traditions and astronomical scientific practices of South Africa in this era of fast changes. “Hemelligaam” has been selected to be part of the roadmap and has been awarded a three year grant to produce a traveling exhibition based on photographic and video material.The Hemelligaam project will not only portray the present of the rural communities living in key areas of historical/astronomical interest and of the people involved in astronomy research in South Africa, but will also record stories and map the sites of ancient indigenous communities that lived or traveled in these areas and that first started to wonder about the Southern Sky. This project will then also create a perfect platform for astronomy outreach and public engagement around the country.In my talk I will briefly present the aims and key projects of the Roadmap for the History of Astronomy in South Africa and will describe the development of the Hemelligaam project and its early results based on its first public exhibition currently underway.
25 years of adaptive optics in planetary astronomy, from the direct imaging of asteroids to Earth-Like exoplanets
Marchis, Franck
Adaptive Optics (AO), a technology that compensates in real time for the atmospheric turbulences on ground-based telescopes has been used in planetary astronomy for 25 years. Saint-Pe et al (1993) is the first article reporteing the direct imaging of the asteroid Ceres. Since then AO has flourished and has been installed on 4m-class and in 2000+ on 8m class telescopes allowing astronomers to conduct studies in our solar system, such as the monitoring the volcanic activity of Io (Marchis al., 2000), study Titan's atmosphere of haze and clouds (de Pater et al. 2006), identification of new storms on Neptune (Max et al., 2003), and the measure of the density of asteroids from newly discovered moons (Marchis et al., 2005).Over the last decade, adaptive optics technology has matured and has been used for studies outside our solar system. Thank to a high contrast achieved with coronagraph the close environment of stars can be directly imaged. Using the Gemini Planet Imager, Macintosh et al (2015) discovered a young self-luminous exo-Jupiter planet orbiting the star 51 Eridani. Structures like gaps in young circumstellar disks (e.g. HD97048, Ginski et al. 2016) have been reported and interpreted as the presence of nascent exoplanets. Instruments that can reach the diffraction limit of 8m-class telescopes in visible light (e.g. Zimpol) provide images sufficient to study craters on the surface of main belt asteroid (Vernazza et al. 2017).The future of AO systems in planetary science is bright. AO systems are key to image Earth-like exoplanets around nearby stars and are part of future telescopes like ELTs, LUVOIR & HABEX. Several near-term privately funded projects are competing to image Earth-like exoplanets in the Alpha Centauri system. The 30-cm space telescope Project Blue (Morse et al., 2018) or the TIKI AO-equipped mid-infrared camera (Blain et al. 2018) could one day give us the image of another pale blue dot around one of these stars.
The theoretical scenario to interpret Gaia results for Cepheids and RR Lyrae
Marconi, Marcella
An updated theoretical scenario fro both Classical Cepheids and RR Lyrae has been developed on the basis of nonlinear convective pulsation models as a function of chemical composition. The predicted bolometric light curves have been transformed in a variety of photometric filters including the Gaia ones. The direct comparison between observed and predicted light curves is a powerful technique to constrain the intrinsic stellar parameters of the investigated pulsating stars. The application to a number of Gaia Cepheids and RR Lyrae is discussed. The theoretical Period-Luminosity and Period-Luminosity-Color relations in the Gaia filters are also presented and compared with the observations.
The theoretical scenario to interpret Gaia results for Cepheids and RR Lyrae
Marconi, Marcella
An updated theoretical scenario fro both Classical Cepheids and RR Lyrae has been developed on the basis of nonlinear convective pulsation models as a function of chemical composition. The predicted bolometric light curves have been transformed in a variety of photometric filters including the Gaia ones. The direct comparison between observed and predicted light curves is a powerful technique to constrain the intrinsic stellar parameters of the investigated pulsating stars. The application to a number of Gaia Cepheids and RR Lyrae is discussed. The theoretical Period-Luminosity and Period-Luminosity-Color relations in the Gaia filters are also presented and compared with the observations.
AGB stellar populations in resolved galaxies with JWST
Marigo, Paola
Thanks to its spatial resolution and infrared filters, JWST is expected to greatly expand the volume accessible for studies of resolved AGB star populations, hence potentially impacting on the calibration of theoretical models for this critical evolutionary phase. In this talk, we will present the predicted appearance of evolved stars in nearby galaxies using the JWST NIRCam and MIRI filters, investigating, in particular, which filter combinations allow for a better separation of the different types (M and C) of AGB stars, and their expected numbers in SMC-like galaxies located at 4 Mpc.Finally, we will discuss the expectations from The Resolved Stellar Populations Early Release Science Program (ID 1334, PI Dan Weisz), which includes the nearby star-forming dwarf WLM.
C.C4.WG3 HERITAGE OF SPACE EXPLORATION: Progress Report
Marov, Mikhail
The main goal of the WG activity in the past triennia was to advance the “Odyssey of human creative genius” project, which focuses on technological heritage connected with space exploration and is closely related to the respective UNESCO Astronomy and World Heritage Initiative. During the last triennia quite elaborative efforts were continuously undertaken towards recognition of space technologies that ensured the great breakthroughs in astronomy but not yet widely accepted and recognized by astronomical community. The relevant segments of space technologies heritage intrinsically related to astronomy and involving both tangible and intangible objects was thoroughly studied. Discussion of thematic and organizing issues relevant to the elaboration of studies and researches on technological heritage connected with space exploration were made within the framework of Associated Event on the UNESCO Thematic Initiative “Astronomy and World Heritage” during the 40th Scientific Assembly of COSPAR in Moscow on August 6, 2014. A part of the Baykonur Space Centre infrastructure facilities were addressed as priority objects of space technology heritage and elaborative comments in support of this idea were brought. Regarding Baikonur cosmodrome as a provisional object of the tangible Space World Heritage, there has been significant progress since the meeting in March 2015 aiming to clarify many problems involved with participation of the IAU, ICOMOS and Russian and Kazakh authorities. The Initiative was preliminary accepted by ROSCOSMOS. Meeting of stakeholders involving the nominated focal points and all other interested parties to advance the UNESCO Initiative regarding to Space Technology Heritage is planned in the UNESCO HQ in 2018 with ROSCOSMOS provisional sponsorship aiming to clarify the main thematic/organizing/cooperative issues concerning the respective WG of the UNESCO WH Center with the involvement of the IAU WG3 C.C4 and other international bodies.
Water inventory from beyond the Jupiter orbit to the terrestrial planets and the Moon
Marov, Mikhail
?omputer simulations of migration of planetesimals from beyond the Jupiter’s orbit to the forming terrestrial planets are discussed. Probabilities of collisions of planetesimals with planets, the Moon, and their embryos based on orbital elements of planets and planetesimals during their dynamical lifetimes were evaluated. The results of modeling argue that provided the total mass of planetesimals amounted to ~ 200 Earth’s masses, the mass of water delivered to Earth from beyond the Jupiter orbit could be about the mass of terrestrial oceans. The water received by the Earth’s embryo of a half of its present mass from the same regions was estimated ~ 30% of the total water mass delivery. We assume that both exogenic and endogenic sources were responsible for the Earth water resources. While bodies similar to C-asteroids appeared to deliver a considerable fraction of water, endogenic water exiled from the Earth interior could balance the high D/H ratio pertinent to comets. The water inventory to the terrestrial planets from beyond the Jupiter orbit was assessed when normalizing water mass to that of a planet. For Venus and Mercury it turned out nearly the same as for Earth while for Mars it was by the factor of about 2-3 more implying that absolute value of water was 3 to 5 times smaller. The mass of water delivered from beyond the Jupiter orbit to the Moon per unit its mass was estimated to be about 20 times smaller than for Earth or in absolute values up to 3·1023 kg. The work was supported by the grant of Russian Science Foundation N 17-17-01279 (planetesimals migration to the Moon) and by the Program of Fundamental Studies of the Presidium of RAS ? 17 as a part of Russian state program for GEOKHI N 00137-2018-0030 (migration of planetesimals to the terrestrial planets and influence of initial orbits of the giant planets on migration of planetesimals and planets).
Solar Cycle 24: Accurate, Long-Term Solar Spectral Irradiance Measurements from Aura OMI
Martchenko, Serguei
As part of its mission to provide global atmospheric trace-gas measurements since 2004, the Earth-observing Ozone Monitoring Instrument (OMI, on board the Aura spacecraft) acquires daily, moderate-resolution (~0.5 nm) solar irradiance data in the 264-504 nm spectral range. Comprehensive performance evaluations invariably attest to a remarkable OMI stability over the mission lifetime: gradual throughput loss of only ~4%-10%, and small wavelength registration drifts (in general much less than 0.02 nm). The slow, regular instrument changes can be characterized very thoroughly, leading to a solar spectral irradiance (SSI) record of exceptional accuracy, with long-term (solar cycle) uncertainties reduced to ~0.1% in the mid-UV and to ~0.05% in the visible region. We compare OMI observations with various missions, composite data sets, and semi-empirical solar models that are available during solar cycle 24. Wavelength-binned daily OMI measurements demonstrate coherent SSI changes down to the ~0.05% accuracy level. We examine short- and long-term variability in various absorption features (e.g., Mg II, Ca II, Fe I and II blends, Hß) as seen in OMI data. We also demonstrate the gradual transition from the faculae- to sunspot-dominated SSI variability.
A new window to the Sun: The Daniel K Inouye Solar Telescope.
Martinez Pillet, Valentin
The National Solar Observatory (NSO) is building the Daniel K Inouye Solar Telescope (DKIST) on the island of Maui (Hawai'i) under the sponsorship of the National Science Foundation. DKIST is a transformational facility for Solar Physics due to its resolving power, light gathering capabilities, and off-axis design. The science enabled by DKIST encompasses from the nature of the turbulently driven local dynamo to high sensitivity off-limb measurements of the magnetic field in the solar corona. The telescope is also particularly well suited to study the highly dynamic and weakly magnetized solar chromosphere. DKIST will come on-line by mid-2020 at a time when the Parker Solar Probe and the Solar Orbiter missions will start their scientific operations. The combination of these three experiments and their measurements of particles, fields, and photons represents a new multi-messenger era for Solar and Heliospheric physics. In this talk, I will give an update on the status of the DKIST construction and the planning for the facility early science through the Critical Science Plan.
Our current picture of the physics of wind-fed massive X-ray binary systems
Martínez-Núñez, Silvia
S. Martínez-Núñez (IFCA), P. Kretschmar (ESAC) on behalf of a large collaboration.A large number of massive X-ray binaries consist of a neutron star accreting matter from the strong stellar wind of a massive companion and producing a powerful X-ray source. These wind-fed systems can play an important and complementary role to characterize the stellar wind properties of massive stars. During a collaborative effort of astronomers from the stellar wind and the X-ray communities, we have found that to advance the current knowledge we have to combine the physics of stellar winds in massive stars in general, accretion theory for compact objects and the physics of X-ray emission from accreting neutron stars and to confront the results with detailed, multi-wavelength observations.In this talk, we will review our current state of knowledge on wind-fed massive X-ray binaries, including recent results and indicate some avenues for future progress.
Theoretical physics and cosmology with ELTs
Martins, Carlos
The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete (or possibly incorrect) and that new physics is out there, waiting to be discovered. A crucial task for the next generation of astrophysical facilities is to search for, identify and ultimately characterize this new physics. I will outline the theoretical arguments pointing to this new physics, and then discuss some unique contributions of the ELTs towards this endeavour, including tests of the stability of nature’s fundamental couplings, tests of the behaviour of gravity in the strong-field regime, and mapping the expansion history of the universe in the deep matter era, by both direct and indirect means. I will also briefly highlight how the ELTs can optimally complement other planned ground and space facilities.
Asteroid families and the next generation surveys
Masiero, Joseph
In the century since the first realization of the existence of asteroid families, our understanding of them has grown through surveys of their astrometric, photometric, spectroscopic, polarimetric, and radiometric properties. In particular, the last twenty years have seen a rapid expansion of our knowledge as surveys for near-Earth objects such as the Catalina Sky Survey and Pan-STARRS have boosted our catalogs of known objects, and astrophysical surveys such as SDSS and WISE have incidentally measured properties of large fractions of the known asteroid population. Thus, we should expect that future large-scale surveys will similarly advance the scientific understanding of asteroid families. I will discuss some of the upcoming surveys that will be particularly beneficial for family studies, as well as longer-term possibilities that may come to pass in the next century of asteroid family science.
Engineering Miracles for Scientific Discoveries with the James Webb Space Telescope
Mather, John
In 1995, scientists asked NASA for an infrared telescope to go far beyond what Hubble can show us, looking at everything from the first stars, galaxies, and black holes, to objects like planets and dust clouds that are too cool to emit visible light, to exoplanets, to planets, comets, asteroids, and satellites throughout our solar system. NASA responded with the James Webb Space Telescope, far larger and more powerful than any space telescope before, operating 1.5 million km from Earth, cooled to 50 Kelvin, and planned for launch 2019. I will outline how we conceived the design, why we’re building it this way, and how we’re testing it to make sure it will work. I will describe the scientific objectives and speculate on what we might discover. Considering that the telescope could detect the light and heat of a bumblebee hovering at the distance of the moon, we can expect to be amazed.
Missing metals and baryons in galaxies: Clues from our Milky Way
Mathur, Smita
It is well-known that most galaxies are missing most of their metals and their baryonic mass. I will present Chandra observations probing our Milky Way halo in absorption. Together with XMM and Suzaku data on emission, our results show that the Milky Way halo contains a huge reservoir of warm-hot gas that may account for a large fraction of missing baryons and metals. I'll review current status of this field, discuss implications of our results to models of galaxy formation and evolution and outline paths for future progress.
ELTs for complex populations of evolved stars around the Galactic center, a few parsecs to a few kilo-parsecs
Matsunaga, Noriyuki
The Galactic center is comprised of complex systems of stars and interstellar matter (gas and dust), and possibly dark matter, which are distributed on different scales. With the super-massive black hole and the highest density of stars/inter stellar matter, this region is important for galaxy-scale evolution and stellar populations therein have such imprints. The severe foreground extinction, however, requires observations in the infrared (rather than in the optical), and current observations are limited to bright tracers such as massive stars, bright pulsating stars, and bright red giants in relatively low extinction fields. An obvious advantage of ELTs is the deeper limiting magnitudes which will allow us to observe tracers with lower luminosity and/or higher foreground extinction. There are other merits of ELTs' larger collecting areas: One can, for example, obtain spectra with higher spectral resolution and/or higher signal-to-noise ratio. The purpose of my talk is to give some perspectives of future observations for various information like stellar kinematics and chemical abundances which can be explored with ELTs in the future and to discuss their impacts on our understanding of populations traced mainly by evolved stars in this region.
Small-scale clustering of nano-dust grains in turbulence
Mattsson, Lars
We investigate the clustering and dynamics of nano-sized particles (nano-dust) in high-resolution (1024^3) simulations of homogeneous isothermal hydrodynamic turbulence. It is well established that large grains will decouple from a turbulent gas flow, while small grains will tend to trace the motion of the gas. However, small grains may still cluster in a turbulent flow (small-scale clustering), which increases the rate of grain-grain interaction. In combination with the fact that nano-dust grains may be abundant, and the increased interaction rate due to turbulent motions, aggregation of nano-dust in, e.g., interstellar clouds, may be quite efficient. We conclude by a brief discussion of charged nano-dust grains how they are different to the passive-scalar type dust in the present simulations.
Characterizing the youngest protostellar disks with the IRAM-PdBI and ALMA: large Class 0 disks are rare
Maury, Anaëlle
While large circumstellar disks are observed around young stars, only a handful of large (r>100 au) candidate protostellar disks have been detected around the youngest (Class 0) protostars so far. However, the pristine properties of circumstellar disks during the main accretion phase could be key in understanding their later evolution, and the way they ultimately form planets. Only the recent advent of powerful interferometric facilities probing km baselines at (sub-)mm wavelengths has allowed the inner envelopes of Class 0 protostars to be explored at resolutions and sensitivities sufficient to disentangle envelope from resolved disk emission at relevant scales (20--200 au).We will present our results with the IRAM-PdBI CALYPSO survey, establishing the paucity of young large disks: in this sample >75% of the 16 Class 0 protostars have no resolved disks at radii r>60 au. We will also present new follow-up observations obtained with the ALMA interferometer. We will discuss how these observations challenge the classical paradigm of disk formation as a natural result of angular momentum conservation, and argue in favor of magnetized protostellar collapse scenario.Finally, we will present our analysis of both the chemical complexity and multi-frequency dust continuum emission at scales ~100 au, suggesting that significant grain growth, maybe precursor to the formation of planetesimals, has already occured at these scales during the Class 0 stage.
Report Office of Astronomy for Development, OAD
McBride, Vanessa
TBA
OAD Representative
McBride, Vanessa
Business Meeting of Div.E and its Commissions, WGs
Summary of FM15
McBride, Vanessa
I will summarise the discussion and outcomes of FM15 on astronomy for development.
What we don’t know about hot gas in the Galaxy, and how X-ray observations might help
McCammon, Dan
TBA
Progress status of GMT
McCarthy, P.
TBA
The Magellanic Stream
McClure-Griffiths, Naomi
Galaxies do not evolve in isolation. Most evidence suggests that galaxies’ evolutionary paths are influenced by their merger histories. Interactions between galaxies, and the gas they provide, can determine whether a galaxy will become a starburst or fade away. Fortunately, the Universe has provided us a front-row seat for observing the interaction of two dwarf galaxies, the Magellanic Clouds, with our own Milky Way. Much of this interaction history is traced through the Magellanic Stream, which is one of the most impressive features in the atomic hydrogen (H I) sky, extending over 200 degrees from the Magellanic Clouds. This tail of neutral and ionized gas extends from the Magellanic Clouds in at least two dominant twisted strands. Based on gas metallicity measurements, it seems that one strand may originate in the Large Magellanic Cloud (LMC) and the other in the Small Magellanic Cloud (SMC). In this talk I will review current knowledge of the Magellanic Stream and lay out some questions that we hope will be addressed with future studies.
JWST Commissioning from Launch to Science Observations
McElwain, Michael
The James Webb Space Telescope (JWST) is a large, 6.5 m segmented aperture telescope equipped with near- and mid-infrared instruments that will observe over a wavelength range of 0.6-28.4 microns. The near-infrared instruments are passively cooled to ~40 K by a 5-layer sunshield while the mid-infrared instrument is actively cooled to 7 K. The goal of JWST commissioning is to provide a timely preparation of the Observatory for science programs, which drives the entire commissioning plan. The JWST is stowed for launch and must carry out orbital insertion maneuvers to its final orbit at L2. While en route to L2, the JWST will maintain communications via NASA's Deep Space Network and make Observatory deployments to enable the passive cooling of the telescope and the science instruments. When cold, the segmented telescope will be aligned by identifying segments, providing wavefront control at the segment-level, co-phasing segments, and correcting the image quality over the large focal plane feeding the science instruments. Finally, the science instruments will execute a series of activities aimed at confirming functionality and calibrating for science. The entire commissioning phase is scheduled to take less than 6 months. Commissioning will be completed by the JWST mission operations team, which is comprised of the international partners from NASA, ESA, and CSA, the aerospace industry partners such as Observatory contractor Northrop Grumman Aerospace Systems, and the science and mission operations center at the Space Telescope Science Institute.
CONSTRAINTS ON EXTRAGALACTIC MAGNETIC FIELDS USING DIFFUSE GALACTIC POLARIZATION
Mckinven, Ryan
The intergalactic medium (IGM) is expected to be permeated with an intergalactic magnetic field (IGMF). We apply Faraday Rotation Measure Synthesis (FRMS) for the first time to real radio-polarimetric data taken from the GALFA Continuum Transit Survey (GALFACTS) and explore various considerations that must be made when selecting sources for extracting the IGMF. The ratio of the intrinsic to observed rotation measure (RM) of the foreground emission is probed using extragalactic sources. This parameter ($X_{RM}$) is estimated over different regions of the sky and is used to rescale the foreground RM contribution experienced by extragalactic source emission. This allows for an extragalactic RM contribution to be isolated for each source. The spread in distribution of this extragalactic RM contribution provides an upper bound constraint on the RM contribution of the IGMF. More broadly, this research illustrates FRMS’s utility in constraining the IGMF. The considerations explored here should prove useful for future researchers devising similar experiments with larger bandwidths of next generation telescopes (SKA) and their precursor/pathfinders (e.g. LOFAR, ASKAP).
Nova Sagittarius V5668 - the first three years
McLoughlin, Dominic
Nova Sagittarius V5668 is a nova that detonated in March 2015 on which we have a densely time-sampled set of observations, from before it reached maximum light until the present day. These spectra are from the Global Jet Watch observatories and span over 1000 days, capturing in detail the very distinct phases of a nova eruption. Our investigations include a prominent dust dip which commenced in the first 100 days, and analysis of many significant changes in the line profiles arising from geometry of the obfuscating dust and the inner binary. Rapid and dramatic changes are observed in outflows of oxygen especially. I will discuss heavy elements detected shortly after detonation and the implications for the history of the progenitor stars. I will present the different dynamical components revealed by the evolving H-alpha complex.
The value of practical classes in Astronomy Education
McNally, Derek
TBA
Life as IAU General Secretary
McNally, Derek
TBA
The Circumgalactic Medium of the Milky Way and M31
Meiksin, Avery
A summary will be provided of recent results on the gas content and flows around the Milky Way and M31 based on UV, optical and radio measurements. Possible consequences of these flows on star formation in the Milky Way and M31 will be discussed.
Kinematics of OB-associations in the 3-kpc solar neighborhood
Melnik, Anna
We use Gaia stellar proper motions to study the kinematics of OB-associations. The average one-dimensional velocity dispersion inside 18 OB-associations with more than 10 Gaia stars is sigmav=3.9 km s-1. The median virial and stellar masses of OB-associations equal 7.1 105 and 9.0 103 solar masses, respectively. Thus OB-associations must be unbound objects provided they do not include a lot of dense gas. The median star-formation efficiency is epsilon=2.1%. Nearly one third of stars of OB-associations must lie outside their tidal radius. We found that the Per OB1 and Car OB1 associations are expanding with the expansion started in a small region of 11--27 pc 7--10 Myr ago. The average expansion velocity is 6.3 km s-1. The location of the Sun near the OLR of the bar creates conditions which stimulate formation of giant molecular clouds.
Tracing Protoclusters with Submillimeter Galaxies
Menéndez-Delmestre, Karín
Radio galaxies have been used quite successfully as protocluster tracers. However, because they are only visible for a short period in the evolution of a massive galaxy, a significant fraction of forming clusters remains unexplored. Clustering analysis indicate that submm-selected galaxies (SMGs) reside in very massive halos, suggesting that they trace high-density environments. Conversely, SMGs have been identified as tracers of structures with more modest masses caught in highly active periods. This suggests that SMGs may be tracers of a wider range of environments beyond the progenitors of today’s rich clusters, opening a window for a more complete exploration of protoclusters. With narrow-band Ly-alpha imaging and multi-object spectroscopy using Palomar/Keck/Magellan/Gemini telescopes we probe for galaxy overdensities in SMG environments at z~1-5. With >100 spectroscopically-confirmed Ly-alpha emitters, we quantify the overdensities in these regions. We are also studying galaxy properties according to the maturity of SMG-traced protoclusters to explore the way galaxy and local environment relate to each other within the broader picture of a cosmologically-evolving large scale structure
Mass Distribution in Stellar Structures of Local Dwarfs
Menéndez-Delmestre, Karín
Galaxies in the local universe are a fossil record of events in the distant universe and present critical constraints for examining models of formation and evolution of galaxies. Based on the Spitzer Survey of Stellar Structure in Galaxies (S4G) database, we study the stellar light that is typically associated with different stellar structures (such as bulge, disk, bar). S4G entails deep mid-IR imaging of nearby galaxies with IRAC at 3.6/4.5 um. With a surface brightness limit at 3.6 um of 27 mag/arcsec^2, this survey is unique in its capability of probing stellar surface densities down to << 1 M_Sun/pc^2, which is of particular interest when studying faint extended objects. The choice of mid-IR is particularly important because the emission of low mass stars, that dominate stellar mass in galaxies, dominates the flux in these bands. The S4G collaboration makes the reduced images publicly available, as well as the 2D decomposition for each galaxy. Based on the mid-IR morphological classification of Buta et al. (2015), we now focus our stellar mass distribution study on ~40 S4G dwarf galaxies. The 2D decomposition suggests that dwarfs are mostly well-fit by disk profiles with either an additional bulge component in ~1/3 of the systems (typically contributing ~25% of the total light), a bar, a nucleus and/or even second-disk component. Bars are present in ~20% of the sample and, although their typical contribution to the 3.6 um light is ~9%, they show a variation in prominence. The 2D decomposition identifies compact nuclei in ~1/4 of the sample with a wide range of contributions to the mid-IR light (1-20%), suggesting compact regions of dust likely heated by young stellar clusters. We are extending this analysis to the full S4G sample in an effort to draw comparisons with the wider galaxy sample and use the diversity of stellar structures within the local universe to establish a local reference for stellar structure formation studies.
The subterahertz sun: equatorial and polar radii from SST and ALMA
Menezes, Fabian
The nominal solar radius is RoN = 6.957(1) × 108 m. It is equivalent to a angular radius of 959.63" from 1 AU and corresponds to the solar photospheric radius. However, this value changes with observations at other wavelengths because the altitude of the dominant electromagnetic radiation is produced at different heights in the solar atmosphere. Therefore the solar radius is a very important parameter for the calibration of solar atmospheric models enabling a better understanding of the atmospheric structure. In Menezes and Valio (2017), the average solar radii measured with extensive data from the Solar Submillimeter-wavw Telescope (SST) were 966.5" ± 2.8" for 0.2 THz and 966.5" ± 2.7" for 0.4 THz and also the radius temporal variation was observed to be anti-correlated with the solar activity at both frequencies. Here we report the measurements of the solar radius at equatorial and polar latitudes for the same frequencies. The slight differences obtained int these radii may be related to solar limb brightening variations over the solar cycle. As a validation, we compared the SST measurements with the solar radius at 0.239 THz observed by ALMA.
AGN demography with JWST - broad-band imaging to the rescue
Messias, Hugo
With available X-ray surveys getting to extreme deep levels with Chandra (~1e-17erg/s/cm2) and probing harder energies with NuSTAR (8-24keV), one may wonder how JWST will contribute to obscured-AGN demography when online. Although deep spectroscopy will be enabled with spectroscopic instrumentation on board JWST (especially with MIRI), such modes will be mostly used for candidate follow-up. This presentation – based on Messias et al. 2012 and 2014, and recent literature developments – aims at showing how deep high-spatial resolution NIRCam and MIRI broad-band imaging can excell in what obscured-AGN demography is concerned with respect to what is currently achieved by X-ray surveys. In the process, some misconceptions undermining the use of this technique will also be addressed. I will show one way to pursue a telescope-time-efficient survey aiming to select AGN up to redshift 2 (and potentially to redshift 6), and what other current science questions such project could address in addition "for free" (i.e., stellar assembly in galaxies or high-redshift source selection).
The Asteroid Impact & Deflection Assessment (AIDA) mission: current status of both the US and European components of the first asteroid deflection test
Michel, Patrick
The main objectives of the joint ESA-NASA Asteroid Impact & Deflection Assessment (AIDA) mission are twofold: (1) to perform an asteroid deflection test by means of a kinetic impactor under detailed study at NASA called DART; and (2) to investigate the changes in geophysical and dynamical properties of the target after the DART impact with the European (ESA) component of the mission, called Hera, has been redesigned from the original version called AIM. The baseline target is the binary near-Earth asteroid (NEA) (65803) Didymos. In particular, its secondary component, called hereafter Didymoon (163 ± 18 m diameter), is the target of the DART mission and will be fully investigated by Hera, providing precious data for science, mining and planetary defense purposes on the smallest investigated asteroid._x000D_ _x000D_ This joint mission will allow extrapolating the results of the kinetic impact to other asteroids and therefore fully validate such asteroid deflection techniques. As such, AIDA will be the first documented deflection experiment and binary asteroid investigation. In particular, it will be the first mission to investigate a binary asteroid, and return new scientific knowledge with important implications for our understanding of asteroid formation and solar system history. Finally, a mission like AIDA will certainly fire the imagination of young people and adults, as the science is accessible and understandable to those audiences and is associated with fascinating challenges and goals of planetary defense. The status of the study and payloads of both mission components will be presented.
Collisions, reaccumulations and asteroid families: tracking shapes and spins
Michel, Patrick
Asteroids that suffer a catastrophic impact can produce a huge array of fragments that may re-accumulate into a family of smaller asteroids owing to their self-gravity. Numerical models of this process can match many properties of observed asteroid families. The shape and spin of the re-accumulated fragments has not typically been modeled, as most previous efforts depend on techniques that merges particles to save computational cost. Here we describe two new modeling techniques that allow for the inclusion of shape and spin during the re-accumulation process and for comparing with actual family members' properties. Simulations of asteroid collisions are typically done in two stages - a hydrodynamics code is used to model the fragmentation of a target asteroid, and a gravitational N-body code is used to model the gravitational re-accumulation of the fragments. The challenges for the N-body side include managing the hand-over from the hydrodynamic code to the N-body code, resolution and time-step issues that arise because of some very high particle velocities. We used multiple techniques to account for shapes and spins, including a resolution reduction routine and bonded-aggregates that freeze shapes together. These efforts, and a handful of very expensive soft-sphere discrete element models, have opened new doors in modeling asteroid re-accumulation and asteroid family formation.The science questions addressed with these new capabilities relate to the full size spectrum of asteroid family members. Results show that more readily elongated objects form especially when disruptions are near but below the catastrophic threshold, but a greater diversity of both small and large bodies is produced during more energetic events. Constraints and tests for these models can be obtained from near-Earth asteroid shapes, lightcurves of small main belt asteroids and the shape and spin of large main belt asteroids with satellites, which typically have rapid spin and elongated shapes.
Discovery of new white dwarfs using Gaia accurate astrometry
Mickaelian, Areg
The discovery of new White Dwarfs (WDs) is extremely important for understanding the kinematics and dynamics of the local stellar population. They are evolutionary signatures of the Milky Way, as most of stars pass through this evolutionary stage. Gaia’s astrometric accuracy allows more detailed studies of WDs and many other stars. Gaia DR1 contains astrometric results for > 1 billion stars with < 20.7. Our method of combined calculation of proper motions (PM) and estimation of stellar distances (Mickaelian & Sinamyan 2010, MNRAS 407, 681) resulted in accuracy of 3.9 mas/yr for PM in each coordinate and revelation of 640 First Byurakan Survey UV-excess stars with PM >10 mas/yr. Adopting 50 km/s upper limit for tangential velocities, we calculated maximum distances and absolute magnitudes and estimated luminosity types for these objects, revealing 185 probable (M > 8), 69 possible WDs (6 < M < 8) and 42 candidate subdwarfs/WDs. The Digitized First Byurakan Survey (DFBS) is more efficient for discovery of new WDs by spectral energy distribution. Using Gaia data for accurate PM in combination with DFBS low-dispersion spectra and additional multiwavelength data, during the pilot survey we have revealed thousands of new WDs and candidate subdwarf/WDs. Many of them are subject for studies on binarity and variability. Gaia DR2 will provide huge amount of data to confirm these WDs and reveal many more such objects. Our method is useful for statistical studies; however, it may be also used for individual studies with an accuracy of 70% when adopting 50 km/s as upper limit for tangential velocities and with an accuracy of 90% when adopting 100 km/s as such.
The history of IAU Symposia
Mickaelian, Areg
The history of the International Astronomical Union (IAU) meetings goes back to 1922 when the IAU General Assembly (GA) I was held in Rome (Italy), following the IAU creation in 1919. However, until 1953, no individual symposia were organized and GA was the only official gathering for astronomers. Altogether, 8 IAU GA were held during 1922-1952. The IAU Symposium 1 on “Co-ordination of Galactic Research” was held on June 17-22, 1953 in Groningen (Netherlands). Starting with 1955, regularly several IAU symposia were held in different places, as well as since 1959 IAU began to also organize colloquia to discuss relatively smaller topics. 20 IAU colloquia numbered as I-XX were held in 1959-1971, and another series of IAU colloquia was organized in 1968-2005, numbered as Nos. 1-200. At present IAU symposia are the only official scientific meetings, 9 of them organized every year. IAU S349 “Under One Sky: the IAU Centenary Symposium” to be held in Vienna during the IAU GA XXX will be the last one by number in 2018. Thus, IAU has a 65-year history of symposia and altogether 349 such meetings have been held, in average 5-6 ones annually. At present most of the IAU symposia during the years of GA are being organized in frame of the GA, typically 6 symposia during each GA. Altogether, 31 IAU GA have been organized during 1922-2018, including 30 regular ones and 1 Extraordinary (1973 in Warsaw, Poland), typically once per 3 years. Since 1974, IAU also organizes regional meetings in Europe, Asia and Pacific (APRIM), Latin America (LARIM), and Middle East and Africa (MEARIM). The European ones were discontinued in 1990 after the creation of the European Astronomical Union (EAS) and organization of the yearly JENAM/ EWASS. The 349 IAU symposia have been organized in 43 countries. We give the statistics of all IAU symposia by years of organization, by various topics of astronomy and astrophysics, and by host countries and cities.
The Gaia Celestial Reference Frame: Properties and relations to ICRF3
Mignard, Francois
The second release of the Gaia data includes a materialisation of a Celestial Reference Frame (called the Gaia-CRF2) agreeing with the ICRS prescriptions. It is based on a set of 556,869 extragalactic distant sources regularly distributed on the sky and ranging from magnitude 16 to 21 in the G-band. The median position accuracy is 0.12 mas for G<18 and 0.5 mas at G = 20. Large-scale systematics are believed to be in the range 20 to 30 muas. New versions with improved astrometry will appear with the next Gaia releases. I will report on the overall properties of this frame and show a comparison to ICRF3 based on the 2820 sources in common. Then I will take on the issues raised by the simultaneous availability of several realisations of the ICRS at different wavelengths and how this should be handled at the IAU level in terms of terminology, alignement, comparison procedures and communication to the astronomical community.
Using Byurakan Plate Archive records for revelation of transient objects
Mikayelyan, Gor
We use Byurakan Plate Archive records for revelation of transient phenomena. The Byurakan Astrophysical Observatory (BAO) Plate Archive Project (https://www.aras.am/PlateArchive/) is aimed at digitization of all 37,500 plates obtained during 1947-1991, their astrometric solution, creation of extraction and analysis software, electronic database, webpage and interactive sky map. The famous Markarian Survey (or the First Byurakan Survey, FBS) 2000 plates were digitized in 2002-2007 and the Digitized FBS (DFBS, www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on this low-dispersion spectroscopic material. Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) database will accommodate all new data. ArVO will provide all standards and tools for efficient usage of the scientific output and its integration in international databases. One of the most interesting science projects that is possible based on BAO Plate Archive data, is the search for transients by comparison of the same fields from different epochs, including both comparison of BAO plates between each other and BAO and POSS 1/2 (DSS 1/2) records. BAO observations are significant contribution for the years gap between POSS1 and POSS2 and may reveal numerous new transients and variables, such as Novae and Supernovae, as well as comets and asteroids. One of our small projects in collaboration with IMCCE (France) was already applied for search and study of asteroids using the VO software SkyBoT and 700 known asteroids were revealed at previously not detected positions, which helped to correct their ephemeris and develop low-dispersion model spectra for search for new asteroids. 7 extremely high amplitude variables (7m-8m and larger differences between two epochs) were discovered by comparison with DSS fields. We will give examples of transients found by means of Byurakan archival observations.
Laboratory Astrophysics in the era of JWST
Milam, Stefanie
Next generation space-based telescopes and instrumentation will offer unprecedented sensitivity and spatial resolution at wavelengths that are inaccessible from the ground due to the Earth’s atmosphere. These spectral regions host a number of molecular lines and spectral features including: CO2, H2, NH3, PAHs, etc. Such facilities work in concert with large ground-based facilities to address key questions of chemical complexity, origin of life or biomolecules, and molecular inheritance throughout star and planet formation, among many others. The James Webb Space Telescope (JWST) is an infrared-optimized observatory with a 6.5m-diameter segmented primary mirror and instrumentation that provides wavelength coverage of 0.6-28.5 microns, offering unprecedented sensitivity greater than previous or current facilities, and high angular resolution (0.07 arcsec at 2 microns) and low-moderate spectral resolution (R~100-3000) (Gardner et al. 2006, SpSciRev 123, 485; Milam et al. 2016, PASP, 128, 959). It offers multiple capabilities through 4 science instruments including: imaging, spectroscopy (slit, IFU, grism/prism), coronography, and aperture mask interferometry. JWST spectral range covers numerous molecular species in both the gas and solid phase, including the vibrational modes of ices, spectral bands of simple organics relevant to warm/hot exoplanets, and isotopologues. Laboratory studies of such species, various physical and chemical processing that may occur, and even extreme physical conditions relevant to different regions or objects are often time consuming and challenging. Efforts are needed for the analysis and interpretation of the vast datasets that are anticipated from JWST. The Webb telescope is currently on schedule to launch in 2020 and will operate 5+ years after commissioning. This presentation will provide an overview of JWST as well as highlight the unique capabilities and some laboratory needs on the horizon for data analysis.
Cratering families: identification and collsional models
Milani comparetti, Andrea
Given the synthetic proper elements catalogs now available for 540,000 asteroids, we are maintaining a periodically updated family classification currently with 118 families and more than 130,000 members. This classification uses only the proper element: by using the absolute magnitude and the available albedo data it has been possible to estimate more than 50 family ages. Because the new families contain many more smaller asteroids, many of the families are found to be of the cratering type, that is with a substantial parent body and many small fragments. For cratering families we propose a quantitative definition. There are many cratering families with two separate ages, thus resulting from two collisional events; this is not a surprise. We list several new cases of cratering families, previously ignored, and include results on cratering families obtained by using resonant proper elements, such as the Astraea family. Our methods for both computation of proper elements and dynamical family classification are rigorous. However, given all the available data, our classification results do provide a reliable history of the collisional evolution of the asteroid main belt? Apart from the only two cases (Vesta, Ceres) for which spacecraft data can be used, the only check about the reliability of our proposed collisional history _x000D_ is to derive a realistic model of the original dispersion of velocities. Such a model for cratering families requires that the original velocity field is not isotropic and that the ejection velocities are not large with respect to the escape velocity from the parent body. Moreover,_x000D_ correlations between the velocities and the spin states of the fragments must be taken into account. We show that an initial velocity field can be reasonably well reconstructed in many cases, by accounting for the post-formation dynamical evolution of family members.
Astrochemistry in Molecular Clouds and in the Laboratory
Millar, Tom
In this talk I will review the development of astrochemistry since the General Assembly in 2015. I will briefly describe recent observations of molecules in interstellar clouds and the successes of models in explaining these. Such observations also present challenges to theory and have led to new computational and laboratory studies on fundamental processes, particularly ice mantle physics and chemistry and state-to-state chemical kinetics.
Evolutionary timescales from AGB to PNe
Miller Bertolami, Marcelo
The transition from the asymptotic giant branch (AGB) to the formation of a planetary nebula (PN) is arguably one of the least understood phases of the evolution of low- and intermediate-mass stars. Recently we have computed a new set of post-AGB stellar evolution sequences based on a detailed callibration of previous evolutionary phases and an updated treatment of the microphysics. Interestingly, the new post-AGB models evolve three to ten times faster than predicted by the stellar evolution models that have been widely in use for more than two decades ---i.e. Vassiliadis & Wood (1994) and Bloecker (1995). This result holds for the whole mass and metallicity range. The new models are also ~0.1-0.3 dex brighter than the previous models with similar remnant masses. In this talk we will discuss the_x000D_ main differences with the older grids and try to shed some light on the reasons behind these differences. Finally, we will discuss some consequences of the new models for our current understanding of the formation of PNe, focusing on our current understanding of the planetary nebula luminosity function and the formation of planetary nebulae around low-mass central stars.
Galactic archaeology: understanding the metallicity gradients with chemo-dynamical models
Minchev, Ivan
Metallicity gradients seen today in the interstellar medium (ISM) and stellar component of disk galaxies are the result of the entire chemo-dynamical evolution since the beginning of disk formation. In a pioneering paper, Matteucci & Francois (1989) have established that the observed negative Milky Way disk metallicity gradient results from an inside-out disk formation. That the Milky Way has formed inside-out is now evident from the more centrally concentrated older stellar populations, also seen in external galaxies. Knowledge of the ISM metallicity gradient evolution with cosmic time is very important, as it can be related to the SFR and gas properties throughout the galaxy lifetime. I will discuss the abundance gradient evolution of groups of stars with similar age (or mono-age populations) in galaxy formation simulations. It will be shown that gradient inversion with distance from the disk midplane seen in both Milky Way data and simulations results from the mixture of stars with different ages, disk flaring, and inside-out disk formation. Finally, I will present a novel technique for constraining the evolution of the Galactic ISM metallicity with radius and time directly from the observations, while at the same time recovering the birth radii of any stellar sample with good metallicity and age measurements.
HMXBs in the early Universe
Mirabel, Felix
Theoretical models and recent observations show the dependence of HMXB formation on decreasing metallicity and increasing redshift. These results support the idea that HMXBs were prolifically produced at cosmic dawn, and that feedback from HMXBs was an important source of heating and partial reionization of the Intergalactic medium far away from star forming galaxies. It will be shown that HMXBs have impact on cosmology because determine the early thermal history of the universe, impact on galaxy formation because determine the properties of the faintest galaxies at high redshifts and the smallest dwarf galaxies in the local universe, and HMXBs also have impact on the incipient gravitational wave astrophysics, because they are one of the possible channels for the formation of binary systems of stellar black holes and neutron stars. Theoretical models and recent observations show the dependence of HMXB formation on decreasing metallicity and increasing redshift. These results support the idea that HMXBs were prolifically produced at cosmic dawn, and that feedback from HMXBs was an important source of heating and partial reionization of the Intergalactic medium far away from star forming galaxies. It will be shown that HMXBs have impact on cosmology because determine the early thermal history of the universe, impact on galaxy formation because determine the properties of the faintest galaxies at high redshifts and the smallest dwarf galaxies in the local universe, and HMXBs also have impact on the incipient gravitational wave astrophysics, because they are one of the possible channels for the formation of binary systems of stellar black holes and neutron stars.
The audacity of vision
Mokhele, Khotso
The principle of using astronomy and other sciences in order to stimulate the development of society was in place within the South African science landscape long before the OAD was hosted in that country. South Africa has thus always been a natural home for the OAD and continues to be a driving force in the global science-for-development conversation. This talk will reflect on the international achievements of the OAD since its establishment, and what has made this initiative stand out among other sciences. It will also reflect on the future and the OAD's potential to make an even more significant contribution to global development.
The effects of non-equilibrium chemistry on atmospheric spectra of exoplanets
Molaverdikhani, Karan
The number of detected exoplanets has increased drastically in the recent years and has revealed a surprising diversity. Current instruments are being pushed to their limits to study their atmospheres and upcoming instruments, such as the James Webb Space Telescope, will only provide the community with very limited resources; demanding wide yet in-detail simulations of these planets to select the most promising candidates.Planetary atmospheres have been studied mostly by assuming thermochemical equilibrium. However, many recent studies suggest this assumption is most likely to be not valid at all-pressures. In particular, it breaks down at mid/low-pressure levels where diffusion and photochemistry dominate. These pressures are also where we have access to the atmosphere (aka planetary photosphere) through emission and transmission spectroscopy, and hence our interpretation of observations is susceptible to the effect of non-equilibrium chemistry on atmospheric spectra of exoplanets.We developed a fast 1D chemical kinetic model to study these effects over a wide range of planets. We employed our in-house radiative self-consistent model (petitCODE) to calculate temperature structure of these planets and we used our kinetic model to investigate how effective temperature [400k to 2500k], surface gravity [logg: 2.0 to 5.0], metallicity [Fe/H: -1.0 to 2.0], C/O [0.25 to 1.25], stellar type [M to F] and eddy diffusion coefficient [kzz: 106 to 1012 cm2/s] affect species abundances. We then calculated how transmission and emission spectra of exoplanets are affected by diffusion. Altogether we studied spectra of more than 100,000 models.We highlight the spectral regions where signatures of non-equilibrium chemistry are more prominent. We present sensitivity of the spectra to the diffusion strength, what planets are the best candidates for the JWST to observe the spectral signatures due to the non-equilibrium chemistry, and where its effect is negligible.
Closing the Photometric Loop: Estimating top-of-atmosphere fluxes from ground based telescopes
Mondrik, Nicholas
For a ground based observatory, the observed flux of an astrophysical source is the product of its spectral energy distribution, the Earth's atmospheric transmission, and the instrumental response. Comparing space-based spectrophotometric observations and ground-based photometry of the same stars, one should be able to reconstruct the observed brightness of the source in a given band pass if the atmospheric and instrument transmission functions are measured. We describe some results of our work to 'close the photometric loop' for HST CALSPEC stars using data obtained with the CTIO 0.9 m telescope. The instrumental response is measured in situ with the Collimated Beam Projector, and spectroscopy of telluric standards provides an estimate of the atmospheric behavior.
Star formation histories from color-magnitude diagrams reaching the oldest main sequence turnoffs: from ultra-faint dwarfs to the Magellanic Clouds.
monelli, matteo
Color-Magnitude Diagrams reaching the oldest main sequence turnoffs are essential for a reliable and accurate determination of the star formation history (SFH) of a stellar system from its formation to the present time. Our team has used the HST and wide field ground based imagers (such as VIMOS@VLT orDECam) to obtain the necessary data to determine the SFH of Local Group galaxies, from ultra-faint dwarfs such as EriII and LeoT, Isolated dwarfs (LCID project) and M31 satellites, to the Magellanic Clouds (SMASH project). This has allowed us to show that even these ultra-faint dwarfs have complex SFHs (Gallart et al. 2018, Monelli et al. 2018, in preparation), provided insight on the origin of the dwarf galaxy types (Gallart et al. 2015), informed about the origin of the LMC stellar bar (Monteagudo et al. 2018) and the LMC outside-in formation scenario (Meschin et al. 2014). In this talk I will concentrate on the most recent and exciting results selected among the above, considering other contributions to the conference for balance (I could provide an updated abstract closer to the conference).
Crowded field photometry with MCAO systems
monelli, matteo
I will present the photometric analysis of crowded fields in globular clusters based on MCAO data collected with 8-10 m class telescopes (LBT/PISCES, Gemini/GEMS). I will discuss the performance of these instruments, and the improvements with respect to the classical approach. The photometry, reaching Ms~21, allowed us to reach the lower main sequence. In this regime, a well defined bend (main sequence knee) appears in NIR colour-magnitude diagrams. The magnitude difference with respect to the turn-off is a solid absolute age indicator, which provides error bars on average a factor of two smaller than other methods. I will summarize the results of our project, and discuss the impact of the incoming ELTs in this field.
Spatially resolved studies of Diffuse Interstellar Bands in Galaxies outside of the Local Group
Monreal Ibero, Ana
Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of different astronomical objects when they are viewed through one or several clouds of Interstellar Medium. Galaxies other than ours offer the opportunity of study the behavior of DIBs under physical (e.g. radiation field) and chemical (e.g. metallicity and relative abundances) different to those typically found in the Milky Way. This can in turn, put further constrains on the nature of the agents creating these features. Because of their weakness, studies targeting extragalactic DIBs are relatively scarce. This is a research that will certainly blossom at the E-ELT era. However, we can already start paving the way.In this talk, we will illustrate how MUSE can help us in this quest. We will use as examples some results on two highly reddened systems. In the first one, AM 1353-272, we established a gradient of DIB strength in a galaxy at more than 150 Mpc (Monreal-Ibero et al. 2015, A&A, 576, 3). In the second one, The Antennae Galaxy, we measured the strength of the l5780 and l5797 DIBs in more than 100 independent line of sights, thus mapping these DIBs for the first time in a system outside the Local Group (Monreal-Ibero et al. 2017, A&A, in press). The distribution of DIB strength was compared with that of atomic hydrogen, molecular gas, and PAHs as traced by the emission in the mid-infrared. In both cases, DIB stregth correlates well with extinction, similar to results for the Milky Way.
Simulation of QSO observations with HARMONI
Monreal Ibero, A.
This work analyses simulations of observations with HARMONI, the first light integral field spectrograph for the European Extremely Large Telescope, for two different scientific approaches to understand the co-evolution of galaxies and their central massive black holes.On the one hand, we study the performances of QSOs hosts observations with HARMONI to determine black holes masses and their host galaxies properties (morphology and kinematics) at redshift around 1.5. On the other hand, we explore the capabilities of HARMONI observations to obtain astrometric measurements of kinematically selected regions of broad line regions (BLRs) of QSOs.
Structuring the IAU: From Commissions to Divisions to Commissions
Montgomery, Thierry
While the IAU was created in the wake of the Versailles Treaty in 1919, its organization and structure had been prepared long before that. "Standing Committees" -the future "Commissions"- gave the IAU its scientific and organizational backbone, and evolved with time. In the early 1990's, Divisions were created, with the main purpose to "amalgamate" the numerous Commissions according to various criteria. Twenty years later, however, it was felt necessary to adapt this Divisions/Commissions structure to the enormous progress of astronomy made in the mean time, and completely reform first the Divisions, then re-create Commissions (and Working Groups) almost from scratch. I will recall and/or explain the reasons for this reform, which took six years (2009-2015), and helped adapt the IAU to the 21st century.
The IAU, from the World to Exoworlds: recollections of a mandate
Montmerle, Thierry
While the IAU underwent a deep structural reform of interest to its members, it also undertook a number of initiatives towards the public. In parallel with the growth of the Office of Astronomy for Development in Cape Town, and of the Office of Astronomy Outreach in Tokyo, the decade-old International School for Young Astronomers entered a new phase with the creation of an Office for Young Astronomers in Oslo. But a broader public was openly attracted by major astronomical discoveries, in particular by "other worlds": planets and satellites of the solar system, and exoplanets -"exoworlds". The issue of "public naming" of celestial objects became a particularly sensitive one, which triggered a number of actions and reactions by the IAU. They culminated with the first "NameExoWorlds" contest, which attracted half a million votes worldwide and saw its conclusion at the Honolulu GA. A story full of events in the backstage...
Application of deep learning methods for image-to-image translation to solar and geophysical data
Moon, Yong-Jae
Multi-wavelength observations become very popular in astronomy and geophysics. Even though there are some correlations among different sensor images, it is not easy to translate from one to the other one. In this paper, we apply a deep learning method for image-to-image translation, based on conditional generative adversarial networks (cGANs), to solar and geophysical images. To examine the validity of the method for scientific data, we use several different types of pairs: (1) AI-generated magnetograms from solar SDO/AIA images, (2) AI-generated EUV images from SDO/HMI solar magnetograms, (3) AI-generated magnetograms from historical sunspot drawings such as Carrington events, and (4) AI-generated IR images from visual weather images. It is very impressive that AI-generated ones are quite consistent with actual ones. We will discuss several applications of this methodology for scientific research.
The Solar Corona viewed through the MinXSS (Miniature X-ray Solar Spectrometer) CubeSats
Moore, Christopher
Advances in technology and instrumentation open new windows for observing astrophysical objects. X-ray detector technology with high readout rates are necessary for the relatively bright Sun, particularly during large flares. The hot plasma in the solar corona generates X-rays, which yield information on the physical conditions of the plasma. This dissertation focusses on detector testing, characterization and solar science with the Miniature X-ray Solar Spectrometer (MinXSS) CubeSats. The MinXSS CubeSats employ Silicon Drift Diode (SDD) detectors called X123, which generate full sun spectrally resolved (~0.15 FWHM at 5.9 keV) measurements of the sparsely measured, 0.5 – 12 keV range. The absolute radiometric calibration of the MinXSS instrument suite was performed at the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF) and spectral resolution determined from radioactive sources. I used MinXSS along with data from the Geostationary Operational Environmental Satellites (GOES), Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Hinode X-ray Telescope (XRT), Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) and Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) to study the solar corona. This resulted in new insights on the coronal temperature distribution and elemental abundance variations for quiescence, active regions and during solar flares.
The Gaia Archive. Status and challenges for Data Release 3+
Mora, Alcione
The data produced by the ESA Gaia mission, and analysed by the DPAC consortium, are provided to the Astronomical community via the Gaia Archive located at ESAC, and its partner and affiliated data centres.The bulk of Data Release 2 is a big catalogue (gaia_source), distributed using the Virtual Observatory TAP protocol, complemented with some ad-hoc extensions. The main extra features include a private space for each registered user (persistent uploads), and the possibility to share these resources among other researchers for a collaborative data analysis. These capabilities make the Archive a key component in the pre-release validation, when the data are ingested but only accessible to the dedicated DPAC team.Additional resources are also available at the Archive. Notably, detailed information on a sample of variable stars, together with their associated light curves, and epoch data for a selection of known asteroids. A set of major survey and their pre-computed cross-matches against Gaia positions is also provided for convenience.A number of technical improvements have been introduced, like the use of arrays, which is a novelty for TAP based archives. As opposed to the first data release, the light curves are not stored as a plain table, but in a separate infrastructure specifically designed to support the massive downloads needed to cope with Data Release 3+, when e.g. epoch data (trillions of photometric and astrometric points), average and epoch spectra (billions) and astrophysical parameter distribution functions (billions) will be progressively available. The additional data products will be indexed using the DataLink Virtual Observatory protocol.Additional features have also been incorporated, such as the possibility to propagate the Gaia positions, proper motions, parallaxes and their uncertainties to any epoch for easier cross-catalogue comparisonFinally, a summary of the system behaviour and users' feedback after the release will be presented.
Color study of asteroid families within the MOVIS catalog
Morate, David
The aim of this work is to study the compositional diversity of asteroid families based on their near-infrared colors, using the data within the MOVIS catalog. As of 2017, this catalog presents data for 53436 asteroids observed in at least two near-infrared filters (Y, J, H, or Ks). Among these, we find information for 6299 asteroids belonging to collisional families with both Y-J and J-Ks colors defined. The work presented here complements the data from SDSS and NEOWISE, allowing detailed description of the overall composition of asteroid families. We derived a near-infrared parameter, the ML*, that allows us to distinguish between four generic compositions: two different primitive groups (P1 and P2), a rocky population, and basaltic asteroids. We conducted statistical tests comparing the families in the MOVIS catalog with the theoretical distributions derived from our ML*, to classify them according to the aforementioned groups. We also studied the background populations, to check how similar they are to their associated families. Finally, we used this parameter in combination with NEOWISE and SDSS to check for possible bimodalities in the data. We found 43 families with ML*err<0.071 and with at least 8 asteroids observed: 5 classified as P1, 10 classified as P2, 19 families associated to the rocky population, and 9 families that were not linked to any of the previous populations. In these cases, we compared our samples with different combinations of these theoretical distributions, to find the one that best fits the family data. We also show, using the data from MOVIS and NEOWISE, that the Bapistina family presents a two-cluster distribution in the near-infrared albedo vs. ML* parameter space, which might be related to a common differentiated parent body. Finally, we show that the backgrounds we defined seem to be linked to their associated families.
The parsec-scale structure of jet-driven HI outflows in powerful radio galaxies
Morganti, Raffaella
Massive outflows of atomic hydrogen in powerful radio galaxies are a striking signature of AGN feedback. Such outflows are considered to be largely driven by the relativistic jets launched by the AGN, pushing their way through the clumpy interstellar medium surrounding the AGN. However, information on the complex interplay on parsec-scales between gas and jets, and how this evolves with time, is extremely limited. Progress can be made by using Very Long Baseline Interferometry (VLBI) which provides the spatial resolution required._x000D_ We have conducted a study to locate and characterise the outflow of atomic gas on parsec scales in a small, but diverse sample of young and recently restarted radio galaxies comprising 4C12.50, 3C236, 4C52.37, and 3C293. In this talk, we will compare the differences and similarities of the properties of the HI outflows in our sample which provides important input for theoretical models. Our data allow to start building up a picture of the relevant physical processes of jet-driven outflows on small scales, while our in results we may see indications for different stages of evolution in jet-ISM interactions. This shows the potential of future studies on larger samples to enable a more detailed statistical analysis.
High Resolution Observations of the SZ effect
Mroczkowski, Tony
At sub-arcminute resolutions, the Sunyaev-Zeldovich effect (SZE) provides several powerful tools for probing the formation of high-redshift galaxy clusters, complementary to X-ray observations. First, the thermal SZE measures the line of sight integral of electron pressure, serving to provide calorimetry of the intra-cluster medium. Second, the kinetic SZE measures line of sight peculiar velocity with respect to our most universal reference frame, the CMB. And finally, both effects have redshift independent surface brightness, making them suitable for pushing to higher and higher redshifts. I will present recent SZE observations with MUSTANG-2, NIKA2, and ALMA, which now attain resolutions approaching those of X-ray observations, and will discuss prospects for a next generation ~40-meter-class telescope in the southern hemisphere called AtLAST, the Atacama Large Aperture Submm/mm Telescope (atlast-telescope.org).
The catalogue of failed eruptions registered by the SDO/AIA
Mrozek, Tomasz
Failed eruptions are a type of solar eruptive events which after initial increase of height are abruptly stopped. Even strongest X-class flares may be accompanied by failed eruptions. Present observations of SDO/AIA give a chance for deep statistical analysis of such events which may lead to understanding the mechanisms responsible for confinement. We developed automated algorithm which can recognize moving structures in AIA images. We searched whole 8 years of AIA database, and we found more than 20 000 dynamic events. Among them around 1500 were failed eruptions which we collected into the catalogue. The catalogue is available on-line, and contains basic information about eruption kinematics, properties of accompanying flare, decay index of magnetic field in the active region etc. The catalogue and preliminary statistical analysis of found failed eruptions will be presented and discussed.
New orbits for perihelion passages of comet 1P/Halley in AD 760 and 837
Mugrauer, Markus
Orbital elements of comets can be deduced from historical observations, where positions on sky and dates of observations are given, as was done e.g. for comet 1P/Halley back to the first centuries BC (e.g. Yeomans & Kiang 1981, MNRAS 197, 633). We critically review the Chinese records for AD 760 and 837, which were previously used to estimate the orbital elements for comet 1P/Halley. Then, we add more dated positions for the perihelion passage of AD 760 also from the Syriac Chronicle of Zuqnin (Harrak 1999, D.L. Neuhäuser et al. 2018, in prep.), whose author had observed and drawn this comet as eyewitness. For AD 837, we also added the positions from al-Kindi's observations (Yazdi 2015, JHA 45, 61) as well as dated positions from Carolingian observations, which were not used before for orbital reconstruction. Several of the dated positions do not agree with the previously published orbits. We then determined a new orbital solution for the AD 760 perihelion passage and are currently working on the AD 837 perihelion - using the method of least squares, taking into account several gravitational perturbers in the solar system. We discuss the light curve of the comet (obtained for the new orbital elements) with records for first and last sighting around conjunction with the Sun as well as the very first and last sightings. The observed comet brightness and tail length (blown by solar wind) depend on cometary and solar activity for the time of observation, the latter is known to be rather high around AD 760 and 837 (Neuhäuser & Neuhäuser 2015 AN 336, 225). Precise orbital elements of these two perihelia are important for going back into the more distant past, because comet 1P/Halley had a close encounter with a planet (Earth within 0.0335 au) in AD 837 April, which should have modified the orbit. A re-assessment of historical records should be done also for the other perihelia passages of 1P/Halley and also for other comets.
A whirling plane of satellite galaxies around Centaurus A challenges cold dark matter cosmology
Müller, Oliver
Dwarf galaxies are tracers of the fine-structure of the large-scale structure of the universe, but their predicted distribution from simulations is in serious conflict with observations in the Local Group, the best studied group of galaxies today. Recently, a plane of dwarf galaxy satellites was discovered around Centaurus A, providing a unique opportunity to test cosmological predictions beyond the Local Group. We surveyed the complete Centaurus Group with the Dark Energy Camera, doubling the census of known dwarf galaxies in the group. Furthermore, we found strong evidence that this satellite plane is corotating, posing a major challenge to the Lambda+CDM cosmology (Müller et al. 2018, Science, 359, 534). Comparison to high-resolution dark matter simulations show that this finding is highly significant, with less than 0.5% of Centaurus A analogues hosting such phase-space correlated structures in the Millennium-II and Illustris simulations.
Lensing-corrected 1.1mm number counts in the ALMA Frontier Fields Survey: A science case for JWST
Muñoz Arancibia, Alejandra
We present galaxy number counts around five strong-lensing galaxy clusters as part of the ALMA Frontier Fields Survey. This aims to characterize the population of faint, dusty star-forming galaxies at high redshift, benefiting from the magnification power of the clusters. Our study combines the analysis of deep (rms ~55-71 uJy/beam) ALMA 1.1mm continuum data over ~23 square arcmin (lens plane) from this survey, with gravitational lensing models produced by different groups. Our estimates for the lensing-corrected number counts consider source detections down to S/N=4.5. Most of these detections lack spectroscopic redshifts, and from those having NIR counterparts, the majority are quite red. Moreover, some detections lack counterparts at other wavelengths, despite the extremely deep Hubble and Spitzer data available for the Frontier Fields clusters. Our ALMA detections thus comprise an interesting population for follow-up observations with JWST, as a robust determination of the missing spectroscopic redshifts will provide better constraints on the source properties, as well as more accurate estimates for the derived number counts.
Sunspot group evolution
Murakozy, Judit
Because of the different mechanisms affecting the formation and decay of sunspot groups one needs to study the evolutionary phases of sunspot groups on a large statistical sample to check the possible roles of these theoretical mechanisms._x000D_ The high temporal resolution of the used SOHO/MDI- Debrecen Data (SDD) allows to study the sunspot group evolution in detail._x000D_ The emergence and decay of sunspot groups will be described by investigating of some features of their different polarity parts._x000D_ These properties are the following: the growth and decay rates, the distance, and the compactness asymmetry of the two polarity parts of active regions.
A new calibration of the cosmic distance ladder based on Gaia parallaxes of RR Lyrae stars
Muraveva, Tatiana
Parallaxes, proper motions, positions, and multi-band time series data for hundreds of thousands variable stars will become public as a part of the Gaia Data Release 2 (DR2) on 25 April, 2018. Precise Gaia DR2 parallaxes for a large sample of MW RR Lyrae stars will be used in order to calibrate the zero point of the RR Lyrae near-infrared period-luminosity (PL) and PL-metallicity (PLZ) relations. These relations are crucially important to set the basis of the extragalactic distance ladder with RR Lyrae stars. The new Gaia parallax-calibrated relations are used to study the distances to the Large and Small Magellanic Clouds.
Orion Bar as a window to evolution of small carbonaceous dust grains
Murga, Maria
The Orion Bar is one of the most well-known photodissociation regions (PDR). An enormous volume of observational data in various spectral ranges makes the Orion Bar a versatile tool for checking theoretical ideas. Specifically, it allows studying small carbonaceous grains, which reveal themselves through mid-infrared (IR) emission bands. Their lifecycle strongly depends on the external conditions that vary dramatically within this object. Thus it is possible to follow the evolutionary changes of dust at different conditions within a single object._x000D_ Observational variations of the mid-IR bands (at 3.3-3.4, 6.2, 7.7, 8.6, 11.3 mkm) and abundance of some small hydrocarbons (C2H, C4H,c-C3H2, l-C3H, etc.) indicate changes in dust size, ionization stage and fraction of grains with aliphatic bonds. We utilize theoretical modeling of photo-processing of carbonaceous grains to interpret these evolutionary clues. Specifically, we consider photo-destruction of hydrogenated amorphous carbon (HAC) grains that causes restructuring of aliphatic-rich material to aromatic-rich material under ultraviolet radiation, formation of species like polycyclic aromatic hydrocarbons and the smallest hydrocarbons like C2H and finally the decrease of the average grain size. The dehydrogenation of aromatic-rich grains and ionization stage of grains along with corresponding changes in IR-spectra are taken into consideration._x000D_ We construct synthetic maps of emission in the observed mid-IR bands across the Orion Bar and compare them with observed maps available in archives. We make conclusions about efficiency of photo-destruction processes in PDRs and about the abundance of HAC grains.
A next-generation Very Large Array
Murphy, Eric
Inspired by dramatic discoveries from the Jansky VLA and ALMA, a plan to pursue a large collecting area radio interferometer that will open new discovery space from proto-planetary disks to distant galaxies is being developed by NRAO and the science community. Building on the superb cm observing conditions and existing infrastructure of the VLA site in the U.S. Southwest, the current vision of the ngVLA will be an interferometric array with more than 10 times the sensitivity and spatial resolution of the current VLA and ALMA, operating at frequencies spanning ~1.2. – 116 GHz. The ngVLA will be optimized for observations at wavelengths between the exquisite performance of ALMA at submm wavelengths, and the future SKA-1 at decimeter to meter wavelengths, thus lending itself to be highly complementary with these facilities. As such, the ngVLA will open a new window on the universe through ultra-sensitive imaging of thermal line and continuum emission down to milliarcecond resolution, as well as deliver unprecedented broad band continuum polarimetric imaging of non-thermal processes. The ngVLA will be the only facility in the world that can tackle a broad range of outstanding scientific questions in modern astronomy by simultaneously delivering the capability to: unveil the formation of Solar System analogues; probe the initial conditions for planetary systems and life with astrochemistry; characterize the assembly, structure, and evolution of galaxies from the first billion years to the present; use pulsars in the Galactic center as fundamental tests of gravity; and understand the formation and evolution of stellar and supermassive blackholes in the era of multi-messenger astronomy.
Does angular momentum regulate HI gas in isolated spirals?
Murugeshan, Chandrashekar
The neutral atomic hydrogen (HI) content of spiral galaxies has been observed to vary with environment, with more HI-poor or HI-deficient spirals being observed in high density environments. This has been attributed to influences such as ram pressure stripping and tidal interactions, which remove neutral hydrogen (HI) from the galaxies. However, some isolated spirals have also been observed to have relatively low HI mass fractions. The low densities of the Intra Galactic Medium in isolated environments make ram pressure stripping and tidal interactions unlikely candidates of gas removal. What then could be making some isolated spirals HI poor? Recently, Obreschkow et al. introduced the fHI - q relation (fHI is the HI mass fraction of a galaxy and q is the global stability parameter), where they find a tight positive correlation between the two parameters among isolated disk galaxies. The q parameter is directly linked to the specific angular momentum of the galaxy. The theoretical prediction is that this should be applicable to both HI excess and HI deficient disk galaxies. If this were to be true, then the HI deficiency in galaxies that reside in loose groups and fields can be explained not necessarily due to any stripping mechanisms but due to their low specific angular momentum. In order to verify this, we obtained high resolution HI data from the ATCA for 6 HI poor isolated spirals. In my talk, I will present the main results which indicate that our sample of HI deficient galaxies consistently follow the fHI - q relation. This result brings to light the importance of angular momentum in understanding the formation history of galaxies.
Impact of the African Very Long Baseline Interferometry Network in the stimulation, growth and sustenance of radio astronomy in Zambia: challenges and opportunities
MWIINGA, Nchimunya
The African Very Long Baseline Interferometry Network (AVN) focuses on modification of existing, albeit obsolete and redundant, dishes previously utilized for satellite telecommunication into an array of radio telescopes. The 32m (in diameter) satellite telecommunication dish, at the Mwembeshi Earth Station in Zambia, has been earmarked for conversion into a radio telescope. This paper highlights opportunities and challenges that impede conversion of the satellite telecommunication dish into a radio telescope. Additionally, the role played by the AVN in increasing human capacity development in science, mathematics and technology through radio astronomy in Zambia. Possible measures relevant for sustaining public interests in radio astronomy in a least developing country such as Zambia are suggested.
What does ALMA tell us about extragalactic magnetic fields?
Nagai, Hiroshi
The Atacama Large Millimeter/submillimeter Array (ALMA) is the most sensitive mm/submm telescope in the world and opening a new window for exploring the universe from nearby to high-z. High precision polarimetry with ALMA is a key capability to studying extragalactic astorophysical phenomena in connection with magnetic fields.Although only handful results from ALMA polarimetry toward extragalactic sources have been published so far, ALMA has already revealed unique and cutting-edge sciences. ALMA observations can probe relatively young electrons of nonthermal radio sources in optically thin regime, and thus study the sites of electron acceleration in energetic events, such as the AGN jet production region (Marti-Vidal et al. 2015; Nagai et al. 2016) and hotspots/shocks (Orienti et al. 2017), and their connections with magnetic fields. ALMA also studies the properties of magnetized plasma in the close vicinity of black hole using Faraday rotation. In near future, there is a possibility of direct imaging of the black hole shadow as well as the accretion flow and jet base together with magnetic field information by VLBI observatoins including ALMA.I will review recent results from ALMA polarimetry and my ongoing work for the study of black hole accretion. I will also give a general idea that ALMA polarimetry will provide insights for extragalactic magnetic field in coming years.
Properties of a Virgo-like progenitor at z˜2
Nanayakkara, Themiya
Driven by the development of sensitive medium band imaging surveys, we have been able to obtain accurate photometric redshifts of galaxies to identify highly dense regions of galaxies at high redshift. MOSFIRE follow up of one such cluster identified by the ZFOURGE survey (Spitler et al., 2012) spectroscopically confirmed a large extended structure at z˜2 (Yuan et al., 2014), which was shown by simulations to form into a Virgo like cluster at z˜0.We used near-infra-red spectroscopy from MOSFIRE to obtain rest-frame optical emission lines to study star-formation, metallicity, ionization conditions, Initial mass function, and dynamics of this system. In my talk I will present a summary of the results we have obtained on this structure as a part of the ZFIRE survey and address the role of environment in the early universe in determining galaxy stellar population and inter-stellar-medium conditions.
Hunting for the first stars: Demystifying the mystery of He II with ELTs
Nanayakkara, Themiya
In the quest for identifying pop-III stars, the most sought-after emission line is He II, however, stellar population models are unable to accurately predict the He II features while being consistent with other emission line diagnostics. To produce He II ionizing photons, stellar populations require sources of hard ionizing radiations with energies >= 54.4 eV. Sources such as AGN, shocks, X-Ray binaries, stellar rotation and/or binary stellar evolution, and post-AGB stars may contribute to hard ionizing radiation fields. These effects complicate the classical definition of nebular/stellar origin of He II, which is purely based on the shape of the emission line. To accurately identify relative contributions from these wide variety of sources, high signal-to-noise spectra with rest-frame UV/optical coverage and advanced stellar population/photoionization are required._x000D_ I will discuss recent results obtained by the VLT/MUSE GTO program, which obtained deep ≈10-30h exposures of the Hubble legacy fields to obtain rest-UV spectra of galaxies at z≈2-6. I will perform photo-ionization modelling of our sample and compare our results with local He II studies to show why our high-redshift ‘analogues’ may fall short in exploring the full parameter space of galaxy systems in the early universe and why it is imperative to obtain spectra of high-redshift systems to perform such studies. Specifically, I will address the necessity to obtain high signal-to-noise spectra of individual galaxies to model rest UV emission and absorption systems along with auxiliary rest-NIR lines, which is very expensive even with the current largest optical/NIR facilities and the benefits of 30-m class telescopes for such studies.
“Impact of Magnetic Activity on Solar and Stellar Environments” WG Chair’s Report
Nandi, Dibyendu
Business Meeting of Div.E and its Commissions, WGs
Modeling of Century-Scale Solar Activity and a Prediction for Cycle 25
Nandi, Dibyendu
It is now believed that variations in the Sun's irradiance are primarily governed by surface magnetic flux emergence and evolution -- at least over centennial timescales. Observations show that this flux emergence is cyclic with significant variations in the amount of magnetic flux from one cycle to another. This magnetic variability is driven by a magnetohydrodynamic dynamo mechanism operating in the Sun’s interior. Based on recent advances in our understanding we utilize a solar surface flux transport model and a solar internal dynamo model to perform the first ever century-scale calibrated, data driven simulation of solar activity to predict the strength and timing of the upcoming sunspot cycle 25. Our simulation results are further interpreted to provide insights on the processes that govern long-term solar variability over centennial timescales.
Constraining dust properties in circumstellar envelopes of carbon stars in the Magellanic Clouds: optical constants and grain size of carbon dust
Nanni, Ambra
In galaxies with sub-solar metallicity, such as the Magellanic Clouds (MCs), a large fraction of the thermally pulsing asymptotic giant branch (TP-AGB) stars evolve through the carbon-rich phase (C-stars), shaping the near and mid-infrared (NIR and MIR) colours of the resolved stellar populations. Specifically, the spectra of C-stars are largely affected by the presence of carbon dust that condenses in their circumstellar envelopes (CSEs).The study of dust growth and radiative transfer in the CSEs of these stars allows us to investigate the properties of carbon dust.The main uncertainties in the input physics of such radiative transfer models are related to the choice of the grain size distribution and of the optical constants for carbon dust. The former cannot be directly derived from observations, while for the latter several sets of lab measurements, very different from each other, are available.The results obtained by using different combinations of those inputs can be tested against the observations of thousands of C-stars in the MCs, providing constraints on the carbon dust properties.To achieve this goal, we follow dust growth and the outflow acceleration, coupled with a radiative transfer code, through the CSEs of C-stars evolving along some selected TP-AGB tracks, for which we compute spectra and colours.By requiring our models to simultaneously reproduce several observed infrared colour-colour diagrams, we found the best agreement with the observations of the MCs for nano dust particles of sizes between 0.035-0.1 microns, rather than by larger grains, of 0.2-0.7 microns. The inability of large grains to reproduce NIR and MIR colours is independent of the adopted optical data set and the deviations between models and observations tend to increase for increasing grain sizes.We also identify a possible trend between the grain size or grain structure (more graphite-like or diamond like) and the mass-loss rate.
The Cosmological Formation of Dwarf Galaxies
Navarro, Julio
I will review our understanding of the formation of dwarf galaxies in the current Lambda-Cold Dark Matter (LCDM) cosmological paradigm. I will focus on the relation between the baryonic mass of a dwarf and that of its dark matter halo host as predicted by LCDM simulations; how it relates to a number of alleged problems for LCDM on small scales, such as the "missing satellites", "too-big-to-fail", and "cusp-core" problems; as well as their potential resolution. I will also touch upon the role of cosmic reionization in shaping the baryon content and star formation histories of faint dwarfs, as well as on the effect of Galactic tides on the structural parameters of satellite galaxies. I will also comment on how dwarfs contribute to the buildup of the outer stellar halos of galaxies like the Milky Way and, time permitting, on how dwarf galaxies may help to rule out some alternative theories of gravity.
The evolution of the luminosity function of cluster galaxies in the Cluster-EAGLE simulation
Negri, Andrea
The galaxy luminosity function (LF) is a fundamental tool for exploring galaxy evolution over cosmic time. In the last decade observations have been able to probe the evolution of the galaxy LF with redshift, in particular showing a variation of its low-mass end with redshift. On the numerical side, there is currently no extended study of the evolution of the LF of galaxies in clusters. We employ the data of the Cluster-EAGLE project, a set of cosmological, hydrodynamical zoom simulations of 30 galaxy clusters, to study the evolution of the galaxy LF in clusters as function of redshift. We compile a catalogue of simulated galaxies’ luminosities in the SDSS bands using the E-MILESspectra database, and taking into account dust attenuation. Stacked luminosity functions show a good agreement with observations, presenting little evolution with redshift of the faint-end slope. The environment effects are strong for intermediate-luminosity galaxies. In the clusters infall region (r > 3 r200), star-forming galaxies dominate in number the knee of the LF, whereas, inside the clusters (r < r200), the fraction of passive galaxies is larger. The relative fraction of passive and star-forming galaxies within r200 evolves with redshift, with the star-forming fraction being larger above z~0.5. On the other hand, the fraction of low-luminosity, red dwarfs dominates the faint end up to z=2.
On the nature of SFXTs
Negueruela, Ignacio
After more than a decade of investigation, it is clear that the differences between SFXTs and classical SGXBs cannot be due to any single parameter. Explanations based on orbital size, wind clumping or neutron star properties have been proposed, but none of them seems to provide the full answer. The X-ray properties of systems do not seem to show any clear divide between the two behaviours. Observation of the optical/infrared countarparts to SFXT can help us understand the source of some of these differences. I will present detailed modelling of the infrared counterpart to IGR J16479-4514, which has an orbital period of only 3.32 d, showing that it is a typical supergiant. The combination of stellar parameters and orbital size implies the need for a gating mechanism close to the neutron star.I will also present full characterisation for a number of optically visible counterparts. I will show that the existing population of counterparts, though not statistically significant, gives strong hints as to the reasons why some objects behave as SGXBs while others are SFXTs, as well as why there are intermediate objects.
Welcome – FM15
Nemaungani, Takalani
Takalani Nemaungani and Piero Benvenuti
Solar brightness variations as they would be observed by Kepler telescope
Nemec, Nina-Elisabeth
Recent planet-hunting missions, such as CoRoT and Kepler opened new perspectives for studying stellar photometric variabilities on timescales of stellar rotation and below. Understanding stellar variability on such timescales, and how it compares to that of the Sun is of particular interest. While stars are observed from arbitrary directions, solar brightness variations are measured from the equatorial plane due to the special position of the Earth-bound observer. Thus, comparison studies of stars and the Sun are not straight forward and the effect of inclination has to be taking into account. Here, we model solar brightness variations on timescales of the solar rotational period and below as they would be observed out of ecliptic. For that the distribution of the magnetic features on the solar surface is calculated with the Surface Flux Transport Model developed at MPS. Using this tool allows us to disentangle two superposed effects: Contributions from the rotation of the magnetic features and contributions from their evolution. Moreover, we study how variability is affected by metallicity, where different inclinations are taking into account. We find, that for an observer from the equatorial plane the solar variability on the rotational timescale would appear to be spot-dominated, whereas for an observer out of the ecliptic it would appear to be faculae-dominate.
What is Terra-Astronomy? An introduction
Neuhäuser, Ralph
There is a large number of historical observations of transient celestial phenomena, often considered sub-lunar, or atmospheric. In what we call Terra Astronomy, we study transient astrophysical processes which potentially affect Terra (e.g. climate, biosphere, etc.) such as solar activity and nearby supernovae - and we investigate them with terrestrial archives, both natural archives (e.g. 14C in trees and 10Be in polar ice) and historical archives (observations recorded in previous centuries to millennia). Written records from various civilizations offer high temporal and spatial resolution, e.g. aurora observations to reconstruct solar activity. Transient phenomena were often recorded in portentous connection: the question was not why and how it happened, but what it could presage. It has been proven challenging to connect or convert qualitative generic text statements to quantitative data. This still holds in the Early Modern Period until the 18th century and is relevant for a better understanding of evolution and depth of the Maunder Minimum.This presentation will discuss challenges and open questions such as: Can we predict solar activity by studying the past? How do cometary plasma tails inform us about solar wind? Given ~10 supernovae in the last two millennia, can we expect to find more? Can the problem of nova evolution be solved with historical observations? How can we go about to find and study additional textual sources, e.g. from Arabia or Korea? What are the advantages and limitations of digital search techniques in a large text corpus?Collaboration with philologists and historical critical methods are essential for a full comprehension of the texts, often in old to ancient languages using different terms, leading to a correct classification of the reported phenomena. Terra Astronomy is truly trans-disciplinary. Synergy is also possible with history of astronomy, historical climatology, and geology (earthquakes, geomagnetic field, volcanic eruptions).
Aurora catalogs revisited - with a focus on European records from the Early Modern Period
Neuhäuser, Dagmar L.
In the first half of the 18th century, catalogs were published in Europe for the first time aiming at a compilation of Aurora Borealis records (e.g. de Mairan 1733 and 1754, Frobesius 1739), they were now observed more often; the auroral phenomenon was studied by investigating locations, durations, and variations within and over the years - the connection to the variable Sun or the interpretation as geomagnetic disturbance moved into the focus of the discussion during the 19th century (e.g. Fritz 1873).From the very beginning of compiling current observations, historical sightings were added: many previous observations were found in collections of prodigies from antiquity and the Early Modern Period (e.g. Obsequens and Lycosthenes, respectively), mostly written in Latin. Thereby, two problems occurred, which made their way into publications until today: new and old collections of portents include all kinds of celestial signs, both day- and night-time, both astronomical and meteorological, and they seldom cite the original sources, so that they suffer from many shortcomings regarding text and dating. For distilling a credible aurora catalog for Europe, one needs cultural knowledge, clear criteria regarding the diverse phenomena recorded, as well as collaboration with scholars of philology and history.At the beginning of the Early Modern Period (16th and 17th centuries), an apocalyptic zeitgeist spreads throughout Europe, transient celestial signs are recorded with patience and details - in particular halo phenomena, from simple effects to elaborated displays, published and widely distributed in broad sheets, an early version of newspapers. Therefore, in particular for the period of the Maunder Minimum, one has to expect that aurora catalogs are contaminated by such signs; furthermore, in this time period, calender confusion between the Julian and Gregorian styles (reform 1582 implemented slowly) led to dating errors and duplications.
Constraints on Interacting Dark Matter ffrom Small-Scale Structures
Nguyen, Quynh Lan
TBA
The dense galactic environments of the Milky Way
Nguyen-Luong, Quang
The dense galactic environments of the Milky WayStar formation takes place in the dense gas phase, therefore a simple dense gas and star formation rate relation has been proposed. With the advent of multi-beam receivers, new observations show that the deviation from linear relations is possible. In addition, different dense gas tracers might also change significantly the measurement of dense gas mass and subsequently the relation between star formation rate and dense gas mass. In the talk, we report a multi-year and multi-tracers wide-field survey that trace the dense gas toward a suit of well-characterized massive star forming regions in the Milky Way. Using the new observations of HCO+ 1–0, HCN 1–0, CS 2–1 and C34S 2–1, we discuss the current understanding of the dense gas phase where star formation takes place.
The Missing Baryons in the Warm-Hot Intergalactic Medium
Nicastro, Fabrizio
TBA
(Magnetised) Camel in the (intra-group) eye of a needle: the genuinely regular magnetic field inside the Stephan's Quintet
Nikiel-Wroczynski, Blazej
Magnetic fields are generally regarded omnipresent in the cosmic space, from stars to clusters of galaxies (and beyond). Wherever found, they are suspected to play a profound role in shaping their environment. A few classes of celestial objects, however, have been studied more scarcely in this regard than the others, and one of them are the galaxy groups. This is due to the technical difficulties of registering the exceptionally weak, extended radio emission that carries the information about the magnetic field inside them to the observer. Even more problematic is the detection of polarised signal (thus, anisotropic magnetic fields): it is much weaker, and additional effects – like beam depolarisation in case of angularly small targets – are present. Homogenous, regular magnetic fields are the most demanding ones to be observed, and so far no efforts to detect them have ended up with a success.I would like to present the recent results from spectropolarimetric observations of the Stephan’s Quintet, the best known galaxy group, made with the WSRT interferometer. For the first time, genuinely regular magnetic field inside a galaxy group – manifesting as a peak in the Faraday dispersion function of sources inside, or behind the Quintet – have been detected. Owing to the unknown pathlength through the magnetised bubble, only the product of the regular field stregth and depth can be calculated; however, it is clear, that the detected field has a few-microgauss strength, and depth of around 10 kpc – or even more. What is the most interesting finding is its extent: at least 60 on 40 kpc. Thus, the energy of the regular magnetic field contained within this system is of the same order, as in magnetised structures found in galaxy clusters – with their host being significantly smaller. The result achieved clearly shows that the detection of magnetic fields in compact galaxy groups is possible, and they might play significant role in shaping the life of their parent systems.
Molecular composition of local dwarf galaxies: Astrochemistry in low-metallicity environments
Nishimura, Yuri
Dwarf galaxies generally have low metallicity. Especially, nitrogen is less abundant by a factor of >10 compared with solar abundance. Metallicity is an important parameter which could have significant impacts on atomic and molecular composition of molecular clouds via change in the gas-phase and grain surface chemistry. To investigate molecular composition of low-metallicity environments, we conducted spectral line survey observations in the 3 mm band (85-116 GHz) toward three dwarf galaxies, the Large Magellanic Cloud (LMC), IC 10, and NGC 6822 with Mopra 22 m, Nobeyama 45 m and IRAM 30 m, respectively. As a result, the lines of CCH, HCN, HCO+, HNC, CS, SO, 13CO, and 12CO were detected in all three galaxies (except for HNC and SO in NGC 6822 due to the insufficient sensitivity). On the other hand, N2H+, CH3OH, C18O and CN were not detected in any galaxies. We found that the spectral intensity patterns are similar to one another regardless of star formation activities. In other words, the spectra observed with a several-ten pc resolution do not reflect the effect of local star formation activities, but rather represent the molecular composition specific to low-metallicity environments. Compared with solar-metallicity environments, the molecular compositions of dwarf galaxies are characterized by as follows. (1) Nitrogen-bearing molecules are deficient as a direct consequence of the lower elemental abundance of nitrogen. The HCN/HCO+ and HNC/HCO+ ratios are lower in dwarf galaxies by factors of 2 to >10 than solar-metallicity galaxies such as our Galaxy and M51. (2) Formation of CCH is enhanced, while that of CH3OH (methanol) is suppressed. Both are interpreted as a consequence of extended photon dominated regions in cloud peripheries due to the lower abundance of dust grains. We will also present latest ALMA results of the LMC and NGC 6822 to show the spatially-resolved physical and chemical properties of the ISM in low-metallicity environments.
Exploration of the Jupiter Trojans with the Lucy Mission
Noll, Keith
The Lucy Mission is being planned for launch in 2021 and will begin a series of encounters with Trojans starting in 2027. Six Trojan objects will be explored including objects in both the L4 and L5 clouds. The targets that Lucy will fly by include members of all three spectral classes that occur in the Trojans, C-type, P-type, and D-type. Infrared albedos span the full range of variation seen in the Trojans. Lucy is equipped with a three science instruments that will obtain color and panchromatic imaging, high resolution imaging, near-infrared spectral imaging, and thermal mapping. Radio science will utilize the spacecraft telecommunications system. Knowledge of the target properties is essential for planning and ongoing observations include determinations of lightcurves, searches for satellites, and spectroscopy. Photometric observations of mutual events of the Patroclus -Menoietius binary are continuing in order to further refine knowledge of the binary mutual orbit. The goal of the Lucy mission is to understand the Trojans in the context of a bigger picture understanding of planetesimals in the outer protoplanetary disk and their redistribution by giant planet migration. Continued constraints both observational and theoretical can be expected to enhance the return from the Lucy mission.
Evolution of the CMB temperature
Noterdaeme, Pasquier
The adiabatic evolution of the cosmic microwave background temperature (TCMB) with cosmic time is a fundamental prediction of the standard Big-Bang theory. Any deviation from the predicted linear relation between TCMB and redshift (z) would have strong implications, either indicating a violation of the hypothesis of local position invariance (and thus of the equivalence principle) or that the number of photons is not conserved. Direct measurements of the CMB temperature-redshift relation provide therefore a crucial test of fundamental physics and cosmology. I will summarise the constraints obtained so far and discuss the future of the measurements with the next generation of extremely large telescopes, along with those obtainable from other facilities.
AGN Feedback and its Importance to Galaxy Evolution in the Era of the Next Generation Very Large Array
Nyland, Kristina
Energetic feedback by Active Galactic Nuclei (AGNs) plays an important evolutionary role in the regulation of star formation (SF) on galactic scales. However, the effects of this feedback as a function of redshift and galaxy properties such as mass, environment and cold gas content remain poorly understood. The broad frequency coverage (1 to 116 GHz), high collecting area (about ten times higher than the current Karl G. Jansky Very Large Array), and superb angular resolution (maximum baselines of at least a few hundred km) of the proposed next generation Very Large Array (ngVLA) are uniquely poised to revolutionize our understanding of AGNs and their role in galaxy evolution. Here, we provide an overview of the science related to AGN feedback that will be possible in the ngVLA era and discuss exciting opportunities for multi-wavelength synergy with other next-generation instruments, such as the Square Kilometer Array and the James Webb Space Telescope. We also present ngVLA imaging simulations of resolved radio jets spanning a wide range of intrinsic extents. As supported by our simulations, the unique combination of high resolution, large collecting area, and wide frequency range of the ngVLA will enable significant advancements in our understanding of the effects of jet-driven feedback on sub-galactic scales, particularly for sources with extents of a few pc to a few kpc such as young and/or lower-power radio AGNs, AGNs hosted by low-mass galaxies, radio jets that are interacting strongly with the interstellar medium of the host galaxy, and AGNs at high redshift.
Galaxy simulations after the angular momentum catastrophe
Obreja, Aura
Numerical studies of the non-linear problem of galaxy formation in a hierarchical universe have now ~30 years of history behind. However, for half of this timespan, galaxy simulations suffered from the so-called "catastrophic loss of angular momentum", resulting in too small and compact galaxies as compared to the observed Universe. This problem largely got solved by improving the numerical algorithms, increasing the resolution and taking into account baryonic feedback processes affecting the gas accretion, cooling and angular momentum transport. Nowadays cosmological simulations of galaxies are resembling the observed Universe, and therefore provide a new means to probe and study in a quantitative manner the origin and evolution of galaxy angular momentum. We use 25 simulated objects from the NIHAO sample to define and characterize a variety of stellar kinematic structures in galaxies: thin and thick discs, large scale single discs, classical and pseudo bulges, spheroids, inner discs, and stellar haloes. These structures have masses, spins, sizes, shapes and rotational support in good agreement with theoretical expectations based on observational data. Above a dark matter halo mass of 11.4 dex, all galaxies have a classical bulge and 70 per cent of them have a thin and thick discs. By tracing back in time the progenitors of all these structures it is possible to constrain their formation history. We find that all types of stellar structures lose a fraction of their maximum angular momentum, acquired at early times from the tidal torques. Surprisingly, even structures like single large scale discs or thin discs can lose an important part of their maximum spin (up to ~70 per cent), and still fulfill the redshift 0 properties of cold discs. We also find that the observed maximum rotational velocity and angular momentum of the cold stellar discs are tightly correlated with the total dynamical mass of the galaxy and the spin of the inner dark matter halo.
The Equation of State of Compact Objects and the Importance of Astrometric Measurements
Oertel, Micaela
TBA
Super DIOS mission
Ohashi, Takaya
We are studying an improved DIOS (Diffuse Intergalactic Oxygen Surveyor) program for a launch year after 2030. The aim of Super DIOS is an X-ray exploration of warm-hot intergalactic medium using emission and absorption lines, measured with TES microcalorimeters. This mission will perform wide field X-ray spectroscopy with FOV of about 30 arcmin and energy resolution of a few eV, but with much improved angular resolution, than the original DIOS, of about 10 arcseconds. Besides the WHIM science, gas dynamics, distribution of elements, and other physical properties of plasmas will be studied with very high sensitiviey for cluster outskirts, supernova remnants, normal and active galaxies, and Galactic interstellar medium. We will describe the Super DIOS mission and its expected science.
Cyclic evolution of misaligned Be disks in Be/X-ray binaries and its observational implications
Okazaki, Atsuo
About a half of high-mass X-ray binaries has a Be star as the mass donor. These Be/X-ray binaries are mostly transient X-ray sources, because the binary orbit is generally eccentric and in addition the orientation of the circumstellar disk of the Be star is not always favorable for the compact object to capture disk gas around periastron. In order to understand the complicated, long-term X-ray behavior of Be/X-ray binaries, including the origin of giant X-ray outbursts, it is thus important to study the long-term evolution of Be-star disks, under the influence of the tidal force of the compact object.In this contribution, first I propose a mechanism for cyclic evolution of misaligned Be disks in Be/X-ray binaries, on the basis of 3D hydrodynamic simulations. Each evolutionary cycle consists of the following stages: 1) As the Be disk grows with time, the initially circular disk becomes eccentric by the Kozai-Lidov mechanism. 2) At some point, the tidal torque on the disk prevails against the torque via mass ejection from the central star, due either to the increase in the former or to the decrease in the latter. Then, the disk starts precession. 3) Thanks to precession, a gap opens between the disk base and mass ejection region of the central star. This allows the formation of a new disk in the stellar equatorial plane. 4) The newly formed circumstellar disk finally replaces the precessing old disk.Then, I discuss the observational features expected from such cyclic disk evolution.
Astronomy and Indigenous Technologies in Africa
Olande, Paul
The use of astronomy in shaping indigeneous technological advances amongst select African ethnic groups is discussed with a view to unraveling the hidden science behind it.
Summary of IAU Symp. 343: Why galaxies care about AGB stars - A continuing challenge through cosmic time
Olofsson, Hans
This symposium aims to build a bridge between research on the AGB stars themselves and its application to the modelling of stellar populations and the chemical evolution of galaxies and the Universe as a whole. It is divided into nine themes:1 - Stellar structure and evolution to, on, and past the AGB2 - Nucleosynthesis, mixing, and rotation3 - Pulsation, dynamical atmospheres, and dust formation4 - Circumstellar envelopes of AGB stars and their progeny, planetary nebulae5 - Binarity, planets, and disks6 - AGB stars in the cosmic matter cycle7 - Resolved and unresolved AGB populations8 - Galaxy evolution, including the first AGB stars9 - New and future observational perspectivesI will summarize the most important advances and challenges in each theme.
Processing of nano dust particles in galaxies
Onaka, Takahsi
Dust grains control thermal balance and chemistry in the interstellar medium (ISM) and their infrared emission is often used as a useful tracer of the star-formation. Therefore, the understanding of the lifecycle of dust grains in the ISM is vital for the study of star-formation and galaxy evolution. While several theoretical studies have investigated the lifecycle of dust grains, observational studies of dust processing are scarce. Smallest grains, or nano dust particles, are thought to be most vulnerable to the environmental conditions and thus a good indicator for the dust processing. A family of emission bands in the near- to mid-infrared are attributed to nano-sized dust containing polycyclic aromatic hydrocarbons (PAHs) or PAH-like atomic groups. Thus, the lifecycle of PAHs in the ISM is particularly interesting. However, even the formation site of the band carriers (hereafter PAHs) remains unclear. Recent observations of the PAH emission in nearby galaxies, NGC1569, NGC2782, and NGC 7727, with the AKARI satellite indicate that PAHs may be formed by fragmentation of larger carbonaceous grains (Onaka et al. 2010, A&A, 514, A15; Onaka et al. 2018, ApJ, 853, 31). In addition, observations of merger galaxies show the presence of PAHs and the paucity of nano-sized dust particle larger than PAHs (very small grains, hereafter VSGs) in extended structures formed by the merger events, suggesting that PAHs may be produced by fragmentation of VSGs (Onaka et al. 2018). Comparison with the dust model further suggests that present models cannot explain the mid-infrared PAH emission and the very faint emission at 24µm properly. The emissivity of PAHs in these harsh conditions may need to be revised. In this presentation, we report the latest results of AKARI observations and discuss the properties of nano-dust particles and dust processing in harsh environments in galaxies.
Investigating orbital and chemical properties of galactic post-AGB binaries
Oomen, Glenn-Michael
Post-AGB stars are transition objects between the AGB and PN evolutionary phases. One of the most important research questions regarding the final evolution of low- and intermediate-mass stars, is the impact of binarity. Binary interaction alters the intrinsic properties of the star (such as: pulsation, mass-loss, dust-formation, circumstellar envelope morphology, etc.) and plays a dominant role in determining its ultimate fate.In this contribution we focus on post-AGB binaries that are the direct result of an interaction on the AGB. We present our results of a homogeneous analysis of decade-long long radial velocity monitoring campaign of post-AGB binaries. These were specifically selected on the basis of their infrared dust excess, which shows the presence of a circumbinary disc. We derived orbital elements for no less than 33 galactic post-AGB binaries. All orbits have periods in the range 100 – 3000 days, often with non-zero eccentricity. These orbital properties cannot be predicted by population synthesis models, since the progenitors of the post-AGB stars must have filled their Roche lobes with the current observed orbital periods. This is not only thought to have circularised the systems, but is also expected to lead to spiral-in resulting in much shorter orbits. Neither circularisation, nor severe orbital shrinkage is detected.Furthermore, we investigate the phenomenon of depletion of refractory elements in the post-AGB photosphere, which is thought to be the result of accretion of metal-poor gas from the circumbinary disc. The ultimate aim of our research is to come to a better understanding of how these binaries evolve. Given the very strong discrepancy between the observed orbital characteristics and the predictions of detailed binary evolution models, this involves a systematic study and evaluation of new binary interaction processes, which are constrained and inspired by the results of a systematic observational programme.
Molecular outflows in young radio galaxies
Oosterloo, Tom
Our view of the physical conditions of the gas in the central regions of AGN has been enriched by the discovery of fast, massive outflows of molecular gas in AGN. These outflows can be driven by radiation from the AGN, but also by the plasma jets ejected by the AGN. These outflows impact on the growth on the central supermassive black hole as well as on the star formation of the host galaxy.Much of the physics of these outflows, and their impact on the evolution of the host galaxy, is still not well understood. Better understanding these outflows, and quantifying their impact, requires tracing their location and deriving their physical conditions (density, mass, mass outflow rate and kinetic energy etc.).We will present recent ALMA observations which have allowed to study the details of the molecular outflows in two radio galaxies where young radio jets play a key role in shaping the surrounding gaseous medium. Data on multiple molecular transitions allow us to derive the physical conditions in different regions of the outflows. We will describe these results, with emphasis on the comparison with other phases of the ISM (HI and ionised gas).Based on a comparison with detailed numerical simulations, for one of the objects we obtain a complete picture of the outflow and find that outflowing molecular gas is present across the entire region co-spatial with the radio plasma, providing unambiguous evidence that the radio jets are driving the outflow. The signature of the impact of the radio jet is clearly seen in the spatial distribution of the excitation temperature and pressure of the outflowing gas, with the highest excitation and pressures found for the gas with the highest outflow velocities. The detailed information about the physical condition of the gas in this fast outflow can serve as template for the signatures of the impact of radio plasma jest on a gas-rich ISM and guide the studies of outflows in other galaxies, including higher redshift objects.
The IAU C41 Working Groups and their Contribution to International History of Astronomy Research
Orchiston, Wayne
IAU Commission 41 was established in 1948 in order to encourage research in history of astronomy. During the two decades leading up to the 2015 Hawaiian IAU GA, C41 hosted five Working Groups. The first of these to be formed was the Archives Working Group, followed by the Historical Instruments, Transits of Venus, Historic Radio Astronomy and Johannes Kepler Working Groups, in that order.In this paper I will trace the history of each of these Working Groups and review the ways in which they contributed internationally to history of astronomy research.
Hands on the Stars
Ortiz Gil, Amelia
As part of a long-term project devoted to stablish a glossary for astronomical terms in Sign language, we present in this contribution the first approach to reach a connection between hearer and deaf people: the First list of a 47 words that the experts of the IAU- Commission 1 agree are amongst the most commonly used in astronomy education and outreach, and the Encyclopedic Dictionary of Astronomy for Sign Languages, originally written in French (by Proust and collaborators) and now translated into English and Spanish, available online._x000D_ This project which involves more than a hundred collaborators, is also considering the possibility of study each sign in order to determine the similarities and differences between different languages and suggest, if possible, a common and unique sign for each word for every country. The languages involved up to now, include French, English, Spanish, German, Italian, Portuguese, Japanese and Polish, among others.
PhD Prize 2017
Ortiz Leon, Gisela
TBA
CC1 WG3 Report "Astronomy for Equity and Inclusion"
Ortiz-Gil, Amelia
The year 2017 has been quite productive for this WG. To start with, thanks to Silvina Pérez and Lina Canas we have a new website and presence in the social media (Facebook)). Group members have produced new resources and activities which have been published in the WG website. We had discussions in the WG email list about activities and new resources coming out from our members and from others, thus allowing for the exchange of information that is one of the main goals of the WG in order to build on top of previous experiences. The WG helped in the elaboration of a selection of accessible activities for Astronomers without Borders (AWB) Global Astronomical Month (GAM) 2017. Each day of that month one of the activities was featured by the communications team of AWB. Several members of the WG are helping with the OAO Astronomy Translation Network project. The group is also assisting in the creation of the interactive exhibition for the next IAU General Assembly in Vienna “Inspiring Stars” with accessible and inclusive resources. We have been making good progress with the project of the astronomy sign language dictionary. The translations into Spanish and English of the original French dictionary by Dominique Proust et al. are already available at the WG website. Work is being done on a compilation of signs from many other languages, and a first list of 47 terms has also been published, as well as announced in a IAU press release. There is also an on-going collaboration with the AAS WAGD, in particular the elaboration of a document regarding journal accessibility.
Massive stars in the X-ray light
Oskinova, Lidia
Massive stars on nearly all evolutionary stages emit X-rays. Recent advancesin observations challenge previously accepted concepts of mechanismsresponsible for this X-ray emission. A possible new paradigm is emerging,considering the X-ray radiation from massive stars as evidence forconnections between the stellar photosphere and the wind. I will brieflyreview what we can learn from the most recent and spectacular observationsof massive stars, such as X-ray pulsations in B-type stars, X-ray aurorae onmagnetic stars, and X-ray variability in O and WR stars with their strongwinds. I will discuss some outstanding questions in massive starastrophysics that could be answered by observations with future X-raytelescopes, and highlight the required synergies with the next generation ofground-based telescopes.
Testing the Stellar Rotation vs. Age Paradigm Using Wide Binaries in the Kepler K2 Fields
Oswalt, Terry
Essential to understanding the history of the Galaxy’s stellar populations, ages are among the most difficult to measure properties of stars. Accurate stellar ages would provide key leverage on problems ranging from the habitability of exoplanets to the Galaxy’s chemical evolution and age. Gyrochronology, the empirical relation between rotation and age, is believed to be among the best current methods of stellar age determination. Using several hundred wide non-interacting binaries identified in the Kepler mission “K2” extended mission fields we are testing this paradigm. Such wide pairs afford a unique opportunity to unravel and calibrate the effects of mass, rotation, activity and age because components of a given binary should have rotation and activity levels consistent with their masses and a common age. We present preliminary results for several dozen wide pairs in which both components exhibit detectable rotational modulation.
Differentiation Signatures among Asteroid Families
Oszkiewicz, Dagmara
The ”missing mantle problem” is a long standing puzzle in planetary science. From one side abundant HED (eg. Bunburra Rockhole, Ibitra, Pasamonte, PCA 91007, NWA 011, A-881394) and iron meteoritic evidence and Solar System formation theories predict that there once existed from 30 to 150 differentiated (into geologically distinct layers: iron core, silicate mantle and crust) planetesimals in the Solar System. On the other hand observationally only one large (4 Vesta and its collisional family) and a few small V-type (parts of crusts and mantles) asteroids in the mid and outer Main Belt (1459 Magnya, 21238 Panarea, 40521 1999 RL95, 10537 1991RY16) have been identified as traces of differentiated planetesimals, thus not summing up to 30-150 different differentiated parent bodies._x000D_ Several different hypothesis were put forward to explain the problem. Currently our understanding of the problem shifted from "battered to bits” hypothesis to postulates such as partial differentiation (Weiss and Elkins-Tanton 2013, Thomas et al. 2017), surface alternation (though space weathering and shock impact processes) and new formation theories (Bottke et al. 2006). In this talk I will review the current meteoritic and observational evidence of differentiation in the Solar System and the various possible explanations for the mismatch between meteoritic and observational indicators.
Unified Picture of Chemical Differentiation in Disk-Forming Regions of Low-Mass Protostellar Sources
Oya, Yoko
Young (Class 0-I) low-mass protostars are known to show significant chemical diversity in their envelopes at a few 1000 au scale: specifically, hot corino (HC) chemistry and warm carbon-chain chemistry (WCCC). HC sources are rich in saturated complex organic molecules (COMs: e.g. HCOOCH3), while WCCC sources in unsaturated carbon-chain molecules (e.g. C4H). It is of great interest how the chemical diversity is inherited to chemistry of disk-forming regions.We investigated distributions and kinematics of various molecules in the disk/envelope system for the 6 young low-mass protostar at a spatial resolution of a few 10 au with ALMA. We found that the chemical diversity at a few 1000 au scale is indeed delivered into the disk-forming regions at a 100 au scale. Moreover, the chemical composition was found to change drastically from envelopes to disks.Such chemical diversity in disk-forming regions was totally unexpected before the ALMA observations. Most interestingly, we found composite sources (L483 and B335) where both the WCCC and HC chemistry are occurring in a single source. In these sources, carbon-chains are abundant in the envelope as in the case of WCCC sources, while COMs are abundant in the disk as in the case of HC sources. This result is consistent with the chemical model of collapsing cores: HC chemistry emerges with the evaporation of COMs from dust grains in a hot (>100 K) region near the protostar, while WCCC is triggered by evaporation of CH4 in a warm (>30 K) region a bit apart from the protostar. Thus, the composite case harbors both rich COMs and rich CH4 on dust grains at the onset of star formation, and may be a common occurrence. In contrast, the HC and WCCC sources are regarded as distinct cases, where either COMs or CH4 are particularly abundant, respectively. This unified view of chemistry in disk-forming regions will be an important clue to tracing the chemical evolution from protostellar cores to protoplanetary disks.
Unveiling the whole from its parts. Or to see the forest from its parts
Pacheco, Eduardo
If DNA molecules were present in the interstellar medium, their observed spectral signatures would be rather complicated. Even the molecular array of a unique dinucleotide will generate a tangled signature. On the other hand, a part of it, e.g. bands of the simpler group of HNCO (isocianic acid) may be detected as a part from the whole, but being confused as coming from an isolated HNCO molecule. We selected 5 key transitions of parts of purines and pyrimidines that have been observed in the ISM as isolated molecules and propose to look for them in molecular clouds. If the ensemble of the 5 transitions are observed together in the same target, it may be that we are detecting the whole from its part.
The First Black Holes in the Cosmic Dark Ages
Pacucci, Fabio
The first black hole seeds formed when the Universe was younger than 500 Myr old and they played an important role in the growth of early (z=7) supermassive black holes. While much progress has been made in understanding their formation and growth, their observational signatures remain largely unexplored. As a result, we are yet to detect these sources._x000D_ We present a novel photometric method to identify black hole seed candidates in deep multi-wavelength surveys. The method relies on infrared and X-ray observations and selects the only two objects with a robust X-ray detection found in the CANDELS/GOODS-S survey with a photometric redshift z>6. Moreover, the case of the z=6.6 Lyman alpha emitter CR7 is discussed. We show how its observational features are compatible with our black hole seed model and we present the results of our variability and spectroscopic studies with the HST and Keck. To date, these objects represent the most promising black hole seed candidates, possibly formed via the direct collapse black hole scenario._x000D_ While this result is based on the best photometric observations of high-z sources available to date, additional insights are expected from deeper spectroscopic and X-ray data. For this reason, we explore the role that JWST will play in the detection of the first black holes and their host galaxies in the Universe.
Historical Observations of Novae: Guest Stars to Glass Plates (and Beyond)
Pagnotta, Ashley
Guest Star observations noted by early Asian astronomers can be identified as novae and other cataclysmic variables (accreting white dwarfs) by connecting them to modern observations, where "modern" can be broadly interpreted to include both archival glass plate and CCD images. I will discuss our recent identification of the cataclysmic variable associated with a nova that erupted in Scorpius in 1437, which we determined by combining Korean observations, Harvard Plate data, and new observations our collaboration took in 2016, as well as other historical observations of Guest Stars we believe to have been novae and their modern counterparts.
Constraining convection across the AGB with high angular resolution observations
Paladini, Claudia
Convection plays a major prole in many astrophysical processes, including energy transport, pulsation, dynamos and winds on evolved stars. Most of our knowledge about stellar convection comes from studying the Sun. On the surface of our star a couple of millions of convective cells are observed, each one with a size of about 2000 km. Following predictions dating back to the ’70, the surface of evolved stars (i.e. the AGBs) is expected to be populated by a few large convective cells several tens of thousand times the size of the solar ones. In this contribution I will present very detailed images of the photosphere of an AGB star obtained with the PIONIER instrument, mounted on the Very Large Telescope Interferometer. The images show a well defined stellar disc populated by a few convective patterns. Thanks to the high quality of our observations we are able to derive characteristic quantities such as contrast and granulation horizontal scale for the first time in a direct way. Such quantities are then compared with scaling relations between granule size, effective temperature and surface gravity that are predicted by simulations of stellar surface convection. I will conclude describing shortly what the next generation of interferometric instruments will bring to our study.
Astrobiology with the ELTs: Searching for bio-signatures in exoplanet atmospheres
Palle, Enric
The advances in high-precision instrumentation and dedicated space missions over the past two decades have produced a revolution in the field of exoplanet research, leading to the discovery of a wealth of earth-sized worlds, several of them within the habitable zone of their star. In the coming years, the efforts will concentrate in the characterization of these planets and their atmospheres, specially those transiting and orbiting around low mass stars. The final goal will be the detection of bio-signatures (clues for wide-spread life affecting the atmospheric composition of these planets). Here I will review the possibilities that the new generation of ELT's and their associated instrumentation will offer in this quest for life around our neighbor stars.
Interstellar filaments and magnetic field
Panopoulou, Gina
PhD Prize 2018 – TBA
The "Cart du Ciel" and the Latin American Observatories
Paolantonio, Santiago
The year 2017 was he 130 anniversary of the beginning of the “Carte du Ciel” project, an ambitious proposal from Paris Observatory to mapphotographically the entire sky, which required the joint effort of numerous observatories on the world to be completed. La Carte du Ciel finally became one of the immediate antecedents of the International Astronomical Union, current rector of world astronomy.The proposal to measure the star positions of all the stars up to the magnitude 11 (Astrographic Catalog) and to register each star up to the magnitude 14 (Carte du ciel), involved the record of more than 30,000 photographic plates. This enormous task, had to be distributed between about 20 observatories, each of which took charge of a delimited area in declination. The southern hemisphere was especially problematic, due to the scarcity of astronomical institutions, for this reason all southern observatories were invited. Santiago de Chile, La Plata and Rio de Janeiro accepted the proposal immediately. However, despite having acquired the necessary equipment, for different circumstances none of the three establishments could start the tasks, so these regions were still not completed at the end of the nineteenth century. In 1900, the Argentine National Observatory which initially rejected the invitation, was incorporated into the project,. After 26 uninterrupted years, it was possible to make the necessary plates,perform the tens of thousands of measurements required and the results were published. The other one of the Latin American institutions that participated in the Carte du Ciel, was the Observatory of Tacubaya, Mexico: in this case, the work was done by the middle of the 20th century. In this contribution, we present the characteristics of this fundamental work and the difficulties in carrying out the task.
AI-generated EUV images of the Sun
Park, Eunsu
In astronomy and geophysics, multi-wavelength observations become very popular. Recently, several deep learning methods, one part of Artificial Intelligence (AI), for image-to-image translations have been suggested and are successful for different types of transformation such as labels to street scene, labels to facade, black and white images to color ones, aerial to map, day to night, and sketch images to pictures. For the first time we apply an image-to-image translation model, based on conditional Generative Adversarial Networks (cGANs), to construct solar EUV images using solar magnetograms. For this, we train the model using pairs of SDO/AIA EUV image and their corresponding SDO/HMI line-of-sight magnetogram for all AIA wavelengths from 2011 to 2016. We test the model by comparing pairs of actual SDO/AIA EUV images and corresponding AI-generated ones in 2017. We find that both real and AI-generated images are quite consistent with each other in that it is difficult for one to distinguish solar EUV images from AI-generated ones. The average correlation between actual image and AI-generated one for all test samples ranges has a maximum value (0.80) for 1600 and 1700 data sets whose structures are quite consistent with those of corresponding magnetograms. Using this model, we construct solar EUV images with Kitt peak magnetograms since 1974. This methodology can be applicable to many scientific fields that use several different filter images.
X-ray Ejecta Kinematics in the Remnants of Historical Supernovae 1604 and 1572
Park, Sangwook
Based on our Chandra High-Energy Transmission Grating Spectrometer (HETGS) observations, we measure the bulk radial velocities of numerous small X-ray emission features from the shocked metal-rich ejecta gas in the remnants of historical supernovae 1604 (Kepler’s supernova remnant) and 1572 (Tycho’s supernova remnant). We measure the Doppler shifts in the K-shell electron transition lines in highly-ionized, He-like Si ions in the spectra of these overabundant ejecta “knots” to estimate their radial velocities. We present our results from a sub-sample of ejecta knots in these remnants. We estimate high radial velocities up to ~10,000 km/s for some of these ejecta knots, indicating the presence of nearly “freely-expanding” stellar debris after ~400 years of the explosions. We discuss the implications of these velocity measurements for the distances to these historical supernovae. This work has been supported in part by NASA Chandra Grants GO6-17060X, AR7-18006X, and GO7-18061X.
Report of the IAU Working Group on Solar Eclipses
Pasachoff, Jay
I report on the activities of the IAU Working Group on Solar Eclipses of Divisions C and E over the last triennium and with plans for the next triennium. Since the previous IAU General Assembly, we had total solar eclipses in Indonesia/Pacific in 2016 and in the United States 2017, the latter especially with major international participation from groups headed by members of the Working Group and from others. There were annular eclipses that crossed Africa and Indian Ocean islands such as Réunion in 2016 and that crossed Chile and Argentina, reaching Africa, in 2017. Our Working Group's Website at eclipses.info provides much information, including maps and links, suitable for professional astronomers and others. After an Antarctic and Southern Africa partial eclipse in 2017, 2018 includes partial eclipses in Argentina/Chile on February 15; Antarctica/Tasmania on July 13; and Arctic including northern Scandinavia and previous totality sites at Novosibirsk in Russia (site of 2008 totality) and at Svalbard (site of 2015 totality). We have assisted with vouching for our scientists to obtain visas and duty-free temporary import of scientific equipment. Astronomers Without Borders has pre-used gratis partial-eclipse glasses that are available for distribution at future sites where partial, annular, or total eclipses are to be visible. The following triennium has total solar eclipses in Chile/Argentina on 2 July 2019 and on 14 December 2020; and annular eclipses on 26 December 2019, 21 June 2020, and 10 June 2021. It also includes a partial eclipse visible from China, Russian Siberia, Korea, and Japan on 6 January 2019. Our Working Group includes members from Russia, Japan, India, Slovakia, China, USA, UK, France, and Canada.
Eclipses in Education
Pasachoff, Jay
When a partial or total eclipse is visible from a country, we have the citizens’ attention and can use it to educate them about astronomy in general and about the eclipse itself in particular. The IAU Working Group on Solar Eclipses, joint between Division C (Education, Development, Heritage) and Division E (Heliophysics) has a wide international membership and takes advantage of the visibility of the eclipse to work with educators and others to provide advance notice of the eclipse, information about the science related to the eclipse, and information on how to observe the eclipse safely—working hard to overcome the common misconception that solar eclipses are dangerous throughout. The efforts of a Task Force of the American Astronomical Society at the 21 August 2017 total solar eclipse with totality crossing the continental United States and partial phases extending from Canada in the north to Mexico and farther south will be cited as an example of activities to be duplicated for future eclipses. In the coming triennium, total eclipses in Chile and Argentina will be joined by partial eclipses in western Asia; an annular eclipse with a path crossing India, Sri Lanka, Malaysia, and Singapore; an annular eclipse in Canada; an annular eclipse from Africa through southern Asia; and, on 10 June 2021, an eclipse with Arctic annularity and partial phases extending through all of Europe and northern Russia.
“Solar Eclipses” WG Chair’s Report
Pasachoff, Jay M.
Business Meeting of Div.E and its Commissions, WGs
The IAU and Solar Eclipses
Pasachoff, Jay
The IAU--which, after all, grew out of George Ellery Hale's Solar Union--has long been involved in sponsoring international collaboration and cooperation for expeditions to total solar eclipses. I describe the series of eclipses and of international expeditions and their locations all over the world since the foundation of the IAU 100 years ago. I also describe the current coordination and recent international participation, and discuss changes in eclipse priorities over the century since the IAU was founded. I link the changes in eclipse-observation priorities to advances in ground-based and space-based heliophysics over the last century.
Calibrating TP-AGB stellar models and chemical yields through resolved stellar populations in the Small Magellanic Cloud
Pastorelli, Giada
Most of the physical processes driving the TP-AGB evolution – mass-loss, occurrence and efficiency of third dredge-up – are not yet fully understood and they need to be modelled with parametrized descriptions. Recent photometric and spectroscopic surveys of resolved stellar populations in the Local Group allow us to perform a reliable calibration of the uncertain parameters, thanks to the detailed identification and characterization of TP-AGB stars and to the accurate measurement of the star formation history of the host systems. We present the results of the on-going calibration of the TP-AGB phase based on a complete sample of AGB stars in the Small Magellanic Cloud observed in the near- and mid-infrared wavelengths (SAGE-SMC survey). We computed large grids of TP-AGB evolutionary tracks with several combinations of third dredge-up and mass-loss prescriptions and we included them in the population synthesis code TRILEGAL, which simulates the photometry and the stellar parameters of a stellar system given its star formation history, distance and reddening. The synthetic TP-AGB population of the SMC is modelled according to the detailed space-resolved star formation history derived with deep near-infrared photometry from the VISTA survey of the Magellanic Clouds (VMC). We put quantitative constraints on the efficiencies of the third dredge-up and mass loss by requiring the models to reproduce the star counts, the luminosity functions and the colour distributions of the observed Oxygen-rich, Carbon-rich and extreme-AGB stars in the infrared pass-bands. Finally, we discuss the impact of the best-fitting prescriptions on the resulting chemical yields. These calibrated evolutionary tracks and isochrones will help to improve the predictive power of evolutionary population synthesis models and to interpret the upcoming data from the future observing facilities.
Supergiant stars as Cosmic Abundance Probes
Patrick, Lee
Massive stars are important probes of chemical evolution in star-forming galaxies. They represent the brightest stellar components of external galaxies and have been used in recent years to examine the metal-content and -distribution in many Local Universe galaxies out to distances of ~20 Mpc. These measurements probe the youngest stellar population and provide robust, independent estimates of radial abundance gradients, important to constrain models of galactic chemical evolution and to anchor the more uncertain nebular estimates at larger distances. Blue and Red Supergiant stars are the brightest of the stellar population in the optical and near-IR, respectively. Even though these stars are evolved products, they are still remarkably young objects (<50Myr). Using intermediate resolution Multi-object spectroscopy combined with state-of-the-art stellar model atmospheres, I demonstrate how these two unique types of stars can be used to estimate stellar abundances in external galaxies. Recent results demonstrate the internal consistency between these measurements and I will present a comparison with nebular probes in the Local Universe. By compiling results from red and blue supergiants, I will present the Mass-Metallicity relation as derived from different stellar tracers and demonstrate the excellent agreement between these probes. By comparing this result with nebular measurements we determine that those empirically calibrated to direct-method studies provide the most consistent results.
Recent results on Pulsar Wind Nebulae
Pavlov, P.
Pulsars are powerful sources of relativistic winds. The interaction with the ambient medium causes these winds to abruptly slow down, leading to the formation of pulsar wind nebulae (PWNe). These nebulae are prominent non-thermal sources seen from radio to TeV gamma-rays. To date, more than one hundred PWNe have been found in X-rays, a couple dozen in TeV gamma-rays, and about a dozen in the radio. I will review the properties of PWNe focusing on recent progress that has been made in this area. Specifically, I will talk about the PWNe of supersonically-moving pulsars where very long tails, "misaligned outflows", and UV bow shocks have been discovered. I will also present spatially-resolved spectroscopy of bright PWNe and discuss the connection between the morphologies of the PWNe and pulse profiles of their parent pulsars. Finally, I will discuss the energetics and radiative efficiencies of PWNe and the implications for the particle acceleration processes.
Phase-space correlations among satellites in the Local Group
Pawlowski, Marcel
Different types of phase-space correlations have been proposed or found among the satellite systems in the Local Group. Some of these appear to be in tension with cosmological simulations, most prominently the observed planes of satellite galaxies, but also a possible overabundance of satellite galaxy pairs. Other correlations, such as candidate cases for the infall of several satellites in a common group like the Crater-Leo objects, or the lopsidedness of the satellite system around Andromeda, might be more in line with cosmological expectations. I will give an overview of these correlations and discuss how precision astrometry can help us understand their origins, study their possible interdependences, and potentially resolve the challenges they pose for cosmological models.
Video
Pecker, Jean-Claude
TBA
"The fundamental physics of AM evolution in a LCDM scenario"
Pedrosa, Susana
Galaxy formation in the current cosmological paradigm is a complex process where several physical mechanisms like inflows, outlfows, interactions and mergers take place and that shape the galaxy. These processes can redistribute the angular momentum content of baryons. Observational results suggest that discs formed conserving angular momentum while elliptical galaxies end up losing a great fraction of it. But the underlining mechanism acting during the assembly of the galaxy still needs to be understood.Using cosmological hydrodynamical simulations that include an effective, physically-motivated Supernova feedback, we perform a thorough study of the components of the galaxies, their interplay and their progenitor systems.
The gravitational origin of angular momentum – reflections on the history and present situation
Peebles, James
The gravitational theory gained favor from two developments. Numerical N-body simulations pretty convincingly showed that the analytic estimate of the spin parameter is about right. And the realization that galaxies likely are dominated by non-dissipative dark matter meant the luminous parts would have to have dissipatively settled to dominate the central parts of galaxies, in the process spinning up the rotation acquired by gravity to support discs. The alternative picture at the time was that spiral galaxies are fossil eddies from primeval turbulence. But in general relativity turbulence could not have lasted long after decoupling. This is not a criticism: healthy progress in science is capricious. But I wonder whether we are again ignoring inconvenient evidence. I shall seek opinions on whether large spirals with inconspicuous classical bulges, which are quite common nearby, challenge standard ideas about how the galaxies formed.
The Multiphase Circumgalactic Medium
Peeples, Molly
The circumgalactic medium (CGM) is a dynamic, multiphase reservoir of gas regulating the flow of gas between galaxies and intergalactic medium. I will review the current observational landscape of the multiphase CGM, with a focus on its mass, content, partitioning by phase, and coevolution with galaxies. I will also review the successes and failures of hydrodynamic simulations at reproducing these observations and giving insight to interpreting them. Finally, I will present new results from the FOGGIE (Figuring Out Gas & Galaxies In Enzo) simulation suite, wherein we achieve unprecedented circumgalactic resolution in a cosmological context. I will show that resolving the small-scale structure of the simulated CGM has important ramifications for interpreting and predicting observable circumgalactic gas.
Planetary Nebulae in the nearby Universe
Pena, Miriam
In the past years there has been a rapidly growing of observational data on planetary nebulae (PNe) in different galaxies, in particular in the nearby ones. This is due to PNe provide important clues to analyze several aspects of galaxies. Differently to HII regions, PNe can be studied in any kind of galaxies: ellipticals, spirals and irregulars. Thus they give information on the stellar evolution of post-AGB stars and the distribution and kinematics of low-intermediate mass stars in parental galaxies. They help to determine the distances of galaxies through the PN luminosity function; they allow to perform the chemical analysis of the old population through the determination of the elements not modified by the stellar nucleosynthesis, to determine the effect of nucleosynthesis of low-intermediate mass stars in the chemical evolution of galaxies, to analyze the old chemical gradient in disk galaxies, and many others.PNe are easily detected in external galaxies by using on-band off-band images, mainly in the Halpha and [OIII] ?5007 lines, which are usually the brightest lines in PNe. However a positive detection does not guarantee the discovery of a PN, as also compact HII regions can be detected with such a technique, therefore spectroscopic confirmation is usually required. For such a confirmation, it is found that 4-m telescopes are in the limit of what is achievable in a reasonable exposure time. Thus, larger telescopes are needed.In this talk I will present some results coming from the analysis of PNe the in nearby Universe. And I will emphasize the importance of analyzing these faint objects with ELTs, in order to improve our understanding of this important population.
The cable-driven dish FAST
Peng, Bo
The FAST, Five-hundred-meter Aperture Spherical radio Telescope, was constructed successfully in a sinkhole-like landform in Guizhou province late 2016, as one of the Chinese Mega-Science Projects as well as a forerunner for the SKA. The FAST can be seen as a modified Arecibo telescope using some innovative techniques, with as much as twice the collecting area and also the sky coverage. This big telescope is pointed by moving the light focus cabin with suspended cables, and simultaneously by deforming the shape of the illuminated cable-mesh back-up of the giant reflector from a sphere to a paraboloid by active controls. I will brief the long journey of 20+ years from innovative idea to the interdisciplinary and collaborative deliverables as a landmark on the earth, addressing the innovation, construction, commissioning of the largest single dish FAST in the world.
Uncovering dwarf elliptical evolution through spatially resolved spectroscopy
Penny, Samantha
Despite being the dominant galaxy population by number in the nearby Universe, the formation timescale and mechanism of dwarf galaxies, including dwarf ellipticals, remains unknown. Are quenched dwarfs the remnants of hierarchical galaxy assembly, or are they formed at later times via the morphological transformation of disk galaxies? Spatially resolved spectroscopy allows us to study the origin of dEs through their stellar kinematics and star formation histories. Using data from the SDSS-IV MaNGA IFU survey, we identify quenched dwarf galaxies in the nearby Universe fainter than Mr = -19, selected independently of morphology and environment. I will show the majority of quenched dwarfs exhibit coherent rotation in their stellar kinematics, and several host disc or spiral features. Others exhibit kinematically distinct cores which must form via gas infall and accretion, or outflows. I will discuss an origin for these dwarfs as quenched low-mass disc/spiral galaxies, supporting the hypothesis that galaxy-galaxy or galaxy-group interactions quench star formation in low mass galaxies. I will also show that a number of bright dEs with signatures of gas accretion host AGN, which are likely maintaining their quiescence.
The reionization epoch: latest results and future prospects with the ELT
Pentericci, Laura
One of the principal science goals for the E-ELT is to find the very first galaxies, that probably reionized the universe and probe their physical properties, which may well be very different from those of their lower redshift counterparts, as they are forming from pristine gas, with very low metal abundances. Current results show that the Lyalpha line coming from young, dust free stellar populations is not only a powerful redshift indicator but its demographics can also be used to constrain the neutral hydrogen fraction at the various epochs, and thus trace the reionization history. In my talk I I will review the latest results in the studies of the earliest galaxies, maily from deep spectroscopic observations and discuss out future prospects with the ELT
Asteroid classification in the Bus-DeMeo taxonomy with limited wavelength range
Penttilä, Antti
The taxonomic classification of asteroids is based on the reflectance properties of the asteroid’s surface regolith, giving information on the composition of the surface. The asteroid families are based on the orbital elements with the assumption of a common parent body. Without the exception of the differentiated parent body of the Vesta family, the family members should share the composition and therefore also the taxonomic class.Bus-DeMeo taxonomy is based on the principal component analysis (PCA) transform of the asteroid spectrum in the wavelength range of 450 (or 850) – 2450 nm. After the PCA transform there is a flowchart for the actual classification of an object. However, there are many telescopes with spectrographs capable to observe only a limited range of the required wavelengths. One example is the Gaia space telescope, which observes asteroid spectra from 330 to 1050 nm.While the Gaia mission aims to create its own taxonomic classification system using the abovementioned wavelength range, the ability to assign a Bus-DeMeo taxonomic class for objects that are observed a with limited (compared to 450–2450 nm) wavelength range would be useful. For this reason, I evaluate the possibilities of automatic Bus-DeMeo classification of observations with limited wavelengths that is based on the linear discriminant analysis transform of the spectrum and the naïve Bayes classifier. The fully automated classification algorithm can be derived on the fly for specific wavelengths. I will review the performance of this approach.
The New and Unexpected Venus from Akatsuki
Peralta, Javier
Akatsuki (originally Venus Climate Orbiter) is a mission from the Japan Aerospace Exploration Agency (JAXA) aimed to study the meteorology of the planet Venus. It was launched on 21th May, 2010 and successfully inserted into orbit on 7th December, 2015. At present, it performs an equatorial orbit towards the west of Venus, with an apoapsis and periapsis height of ~360,000 km and 1,000–8,000 km respectively, and a rotation period of 10 days. Akatsuki has an onboard ultra-stable oscillator (USO) to perform radio occultation measurements and 5 cameras to sense different levels of the atmosphere: UVI (filters 283 and 365 nm) permits to study the absorption of the sunlight at ~70 km due to SO2 and a mysterious absorber; IR1 (0.90−1.01 µm) allows to study the clouds at ~60 km, H2O and the thermal emission from the surface; IR2 (1.74−2.32 µm) enables studying CO and other aerosols, the opacity of deepest clouds and the altitude of dayside cloud tops; LIR (10 µm) retrieves the temperature at the cloud tops; finally, LAC cannot retrieve global images but is sensitive enough to detect fluorescence phenomena and lightning. The first two years of Akatsuki observations have unveiled a completely new Venus. The full set of cameras allowed to visualize an impressive variety of new cloud morphologies and atmospheric phenomena (Limaye, 2018), LIR has enabled the discovery of the biggest stationary wave in our solar system (Fukuhara, 2017; Kouyama, 2018), IR2 nightside images permitted to discover an unexpected powerful jet which periodically appears at the equatorial deep clouds (Horinouchi 2017), UVI images have provided valuable hints about the true nature of the unknown absorber (Lee, 2017) and new behaviour in cloud tops’ winds (Horinouchi, 2018), while radio occultation using USO is retrieving localtime-dependent structures at deeper levels than ever before.
IAU General Secretary 1967-1970
Perek, Luboš
TBA
CB4: New Results in Radio Astronomy - Star and Planet Formation
Perez, Laura
The vast number of known extrasolar planets suggests that planet formation is a natural outcome of the star formation process. During their formation, young pre-main sequence stars are generally surrounded by a gaseous accretion disk, which provides a large reservoir of material available for the eventual formation of planets. With the advent of sensitive observations — particularly of these circumstellar disks at radio wavelengths — and together with developments in theory, we are making rapid progress in understanding how this protoplanetary disk material is transformed into a planetary system. In this talk, I will highlight recent results in the field, focusing on observations from the sub-millimeter to the centimeter-wave regime that are providing new insights into the process of star and planet formation.
Formation and evolution of protoplanetary disks - observations and modeling of jets, disks, and disk substructures
Perez, Laura
Planet formation takes place in the gaseous and dusty disks that surround young stars, known as protoplanetary disks. With the advent of sensitive observations and together with developments in theory, our field is making rapid progress in understanding how the evolution of protoplanetary disks takes place, from its inception to the end result of a fully-formed planetary system. In this review, I will discuss how observations that trace both the dust and gas components of these systems inform us about their evolution, mass budget, and chemistry. Particularly, the process of disk evolution and planet formation will leave an imprint on the distribution of solid particles at different locations in a protoplanetary disk, and I will focus on recent observational results at high angular resolution in the sub-millimeter regime, which have revealed a variety of substructures present in these objects.
Cluster star formation probed with scaling relations
Perez Martinez, Jose Manuel
To put strong constraints on the environmental impact on galaxies we investigate quantitatively the kinematic status of galaxies in several clusters at z~1.5, z~0.9 and z~0.5 using KMOS, FORS2, VIMOS and OSIRIS-GTC data. Our high-z KMOS observations provide spatially resolved star formation and H-alpha gas kinematics of galaxies enabling us to examine their rotational support and star formation status before they become the passive population we see in clusters at later stages. At the same time, the good spatial resolution of our data at lower redshift allows a thorough analysis of subtle kinematical irregularities that trace accretion and stripping events, tidal and harassment processes, as well as mergers, and their impact on different scaling relations.We use different representations of the Tully-Fisher relation (TFR) to study galaxy evolution between the starting point of the hierarchical assembly of clusters, and the epoch when half of the cluster mass has been already accreted. While the B-band TFR is sensitive to recent episodes of star formation, the stellar mass TFR tracks the overall evolution of the underlying stellar population. The combination of these two schemes allows us to identify galaxies that might be suffering cluster-specific interactions as outliers in the B-band TFR, while these very same galaxies display no significant offsets in the stellar-mass TFR. I will discuss the connection between the kinematic status of cluster galaxies and their recent star formation history during these two important epochs.
The Star Formation History and assembly of galaxies at z=4-7 probed by CEERS and the GTO MIRI Deep Survey (MDS) and parallels
Pérez-González, Pablo
I will present a project to study the Star Formation History and assembly of high redshift galaxies using CEERS data as well as the JWST Guaranteed Time observations awarded to the MIRI European Consortium Science Team.The Cosmic Evolution Early Release Science Survey (CEERS) is an observing programme selected for execution during the Early Release Science phase of observations on the James Webb Space Telescope. The MIRI Deep Survey (MDS) will obtain ultra-deep imaging and spectroscopy not only with MIRI, but also with NIRCam and NIRISS, providing unprecedented and uniquely deep data during the first year of the JWST mission.Among the many science topics that CEERS and our GTO data can address, I will concentrate my talk on how the MIRI and NIRISS data can be used to study in detail the distinct stellar populations present in galaxies at z=4-7 and beyond, as well as their spatial distribution.
The radial galactic distribution of the ionizing field of radiation in HII regions using photoionization models
Pérez-Montero, Enrique
HII regions in galaxy disks can be used as a powerful tool to trace the radial distribution of several of their properties and shed some light on the different relevant processes on galaxy formation and evolution. Among the properties that can be extracted from the study of the ionized gas are the metallicity, the excitation and the hardness of the ionizing field of radiation. These parameters are usually estimated in un-resolved star-forming complexes from the comparison of the relative fluxes of the most prominent emission-lines with sets of very well characterized data or from photoionization models. In this contribution we will focus on the determination of both the ionization parameter and the effective temperature of the ionizing clusters in those regions with a well derived metal content it is possible to establish a direct comparison between observations and model predictions in the plane of [OII]/[OIII] vs. [SII]/[SIII] to give accurate estimations of these parameters. We will also show the implications that the use of our appropriate Chi square comparison have to the study of the radial variation of both excitation and effective temperature in some very well-studied disk galaxies of the Local Universe and their interplay with metallicity gradients in these objects.
The Universe Isn’t Silent: Electroacoustic Ensembles with Life 2.0
Perkins, Deborah Kala
The universe isn’t silent. It has a sound track…that is played on space itself, because space can wabble like a drum; …recording some of the universe’s most dramatic events as they unfold. We are adding to our glorious light understanding of the universe, a sonic composition (Jana Levin).Ground and space-based gravitational wave observatories are listening to the universe for the ringing wabble of gravitational waves in space as it squeezes and stretches from colliding black holes; researchers are sonifying the data. The use of EM waves translated into sound are being used both by research astrophysics in the quest to detect new distant planetary orbits, and atmospheric compositions with Kepler Space Telescope data, as well as at the convening of cosmos and culture. Cosmologists are in quest of possible other universes seeking gravitational distortions in radio waves at the very edges of the perceivable universe. A software program is allowing blind astronomers to study data, as well as to assist sighted astronomers to discern patterns more readily accessible to the ear than by sight. Astrophysicists and astrobiologists, working with composers have developed “Acoustic Astronomy” translating astronomical data into compositions to both inform and inspire. Astronomers are sonifying the data from the cosmic microware background and pulsars to better understand the rhythmic and harmonic principles of our universe; while ALMA radio observatory, in Chile has developed a public archived data soundbank. In that we are living in an immersion of cosmic processes, what might this imply about the nature and significance of each and every life expression on our planet, each unique bio-organism and ecosystem? What might this imply regarding Earth’s harmonics with potential life and universal dynamics in space and on other worlds? This presentation will explore possible implications of our resonant immersion in life’s symphonics, and co-creativity in concert with cosmos.
STEM for WOMEN
Perumal, Vyjayanthi Mala
Women are incredible at multi-tasking. But the number of women holding technical position is appallingly small. A magnifying lens is required to discover women in powerful technical positions in the midst of an ocean of men. This scenario has to be changed. Participation of more women is required to break this gender barrier. In order to eliminate the underrepresentation of women, several initiatives are totally centred around empowering women and giving them flexibility to think out of the box. This presentation focuses on the initiative targeting Government schools for providing STEM Education to underprivileged children especially girls through hands on learning methodologies. Education is the master key to mental, emotional and academic growth of children. Providing it with hands on learning techniques enhances the knowledge of the children rapidly. The programs relating to STEM conducted, are based on age groups and it differs between groups. It induces new thoughts for scientific development and upgrades the thought process in young brains. The kids are furnished with resources for them to have a hands-on involvement. It is our passionate desire to aid young people to have an approach to science that is driven by love of discovery, exploratory learning, and which requires children to actively engage with challenges in order to find solutions. The future generation will have a comprehensive grasp of issues, take on leadership roles in the future, think out of the box, be creative and more independent in any environment.In tune with this, we have ensured that our girls/women participate in astronomy related activities,arts & crafts, and organic farming (to bring home the message of sustainable living) in addition to STEM courses. With the additional knowledge and hands on application that we encourage in a stress free environment, we hope that it would widen the aspirations of female children and prompt them to enter STEM&Astronomy fields later on.
Spectroscopic Temperatures, Gravities, and Metallicities for Kepler Giants
Peterson, Ruth
Motivated by the need for reliable stellar parrameters in applying asteroseimic observational constraints to derive fundamental stellar parameters, we report the results of a pilot study that uses Keck HIRES spectra exclusively to determine temperatures, gravities, and metallicities for giants of solar-metallicity and higher that lie within the Kepler field. Our approach is independent of the photometry, reddening, and isochrones generally invoked in making such determinations, as these have proven somewhat problematical in asteroseismological studies (e.g. Corsaro et al. 2017, A&A, 605, A3).Our primary focus is on NGC 6791, the metal-rich old open cluster that serves as a benchmark for metal-rich systems near and far. Based on Keck spectra for about twenty stars, we determine preliminary radial velocities as a first indicator of membership. We then determine temperature (from Fe I lines over a wide range of excitation), gravity (from Fe II lines and the wings of strong lines), and metallicity (from weak Fe I and Fe II lines), by running spectral synthesis for every star, to match as much of each HIRES spectrum as is feasible.We begin with the relatively weak-lined warm stars near the cluster turnoff, and continue upwards in luminosity to reach the very strong-lined, cool stars of the giant branch. With the help of brighter analogs of these stars outside the Kepler field, and our decades-long effort to improve atomic-line gf values by intercomparing stars across a range of spectral types, we are able to significantly reduce the uncertainties of these critical determinations.
Prospects for a UV High-Resolution Theoretical Stellar Spectral Library for Old Stellar Systems
Peterson, Ruth
Many Fe I levels have unknown energies, wreaking havoc on attempts to model the UV in solar-type stars. Stellar UV spectra have alleviated this somewhat: Peterson & Kurucz 2015 (ApJS, 216, 1) and Peterson, Kurucz, & Ayres 2017 (ApJS, 229, 23) have now published identifications and line lists for 124 previously unknown Fe I levels, and gf-values good to ~0.1-0.2 dex for sufficiently strong and unblended newly-identified Fe I lines.However, our theoretical calculations still seriously underestimate the UV fluxes of early-G stars in regions where many unknown Fe I lines remain, notably blueward of 2700A (PK15, Fig. 1). This prevents the determinations of reliable elemental abundances for several atomic elements that have lines in the UV exclusively. Our work also fails to reproduce the UV flux distributions of nearby stars and distant galaxies, unless the Kurucz predicted line list is invoked, with errors of 10's of A in line positions.Here we outline steps we are taking in the ongoing HST programs GO-14161 and GO-15179 to remedy this situation. When complete, these programs will provide additional echelle UV spectra that will help to identify the strong unknown lines remaining in the UV, and will also provide observational template echelle UV spectra for stars at the turnoff of old stellar systems of solar and near-solar metallicity. Our ultimate goal is to generate from these, and from the Fe I levels discovered from them, a reliable grid of theoretical stellar UV spectra at a resolution of 30,000 or better. The anticipated grid should include stars ranging from the hot blue horizontal branch stars and blue stragglers of old, metal-poor, relatively nearby systems, to the turnoff F- and early G-type stars of systems of solar metallicity and higher in remote, red-and-dead galaxies at low to intermediate redshifts.
Milky Way structure based on thousands of Cepheids and RR Lyrae stars from the OGLE survey
Pietrukowicz, Pawel
Classical Cepheids and RR Lyrae-type variable stars are widely-used tracers of young (<300 Myr) and old (>10 Gyr) stellar populations, respectively. These stars also serve as distance indicators allowing for Galactic structure studies. Confident detection of pulsating variables requires precise and relatively frequent observations over several years. Recently, the OGLE survey has discovered nearly one thousand new genuine classical Cepheids and two thousands RR Lyrae stars along the Galactic plane in the III and IV quadrants. I will present the view of the spiral structure drawn from known Cepheids and the picture of the Milky Way old population that emerges from the set of known RR Lyrae stars.
The First 200 kyr of the Solar System
Pignatale, Francesco
Chondrites are the most puzzling objects in the Solar System as they are made of minerals that experienced different thermal histories. Carbonaceous chondrites, that are thought to have assembled in the outer cooler region of the Solar System, are, paradoxically, the richest in high refractory material that should have formed close to the Sun. The mechanisms that led to the formation and accretion of chondrites are still unconstrained.The age of their oldest components (Ca-Al-rich inclusions, CAIs) shows that their building blocks could have formed concurrently with the Sun, during the collapse of the parent cloud that formed our Solar System. Here we investigate, for the first time, the dynamical and chemical evolution of different solids from the collapsing cloud to their transport in the forming protoplanetary disk. Our 1D disk model includes several processes such as gas and dust condensation/evaporation, dust growth/fragmentation, radiative and viscous heating, dead zone and a cloud infall in the form of a source term.We find that the interplay among (1) the location in which material is injected in the disk from the cloud, (2) the physical and thermal properties of the considered material, (3) the disc dynamics and (4) several flash-heating events, naturally produces aggregates where components with different thermal histories can coexist.Moreover, the disk expansion causes an efficient advection of refractory material towards large radii. The dead zone plays a crucial role in creating and keeping an heterogeneous mixture of dust. Our results also reconciles with the CAIs production timescales and their distribution in chondrites without including any other mechanism of outward transport of material in the disk. The observed strong flash-heating events can then be responsible for CAIs re-heating and chondrule formation.
UVSat - a concept of UV/visual double-telescope photometric microsatellite
Pigulski, Andrzej
Time-series photometry from space in the ultraviolet can be presently done with only a few platforms, none of which is able to provide wide-field long-term high-cadence photometry. We present a concept of UVSat, a twin space telescope which will be capable to perform this kind of photometry, filling an observational niche. The satellite will host two telescopes, one for observations in the ultraviolet, the other for observations in the optical band. We also briefly show what science can be done with UVSat. The satellite will host two refracting telescopes with apertures of 10 cm, one with optics designed for wide-band UV observations (200 – 300 nm), the other, for observations in the visual band (500 – 600 nm). - The field of view of both telescopes will be the same: about 10×10. - The observations will be carried out in selected fields and will last one to six months. In each field, a sample of a few hundred objects will be monitored with a cadence of the order of at least a few seconds. Observing multiple fields during a single orbit is also an option. - A large dynamical range will be secured by the ability of on-board stacking or using a detector which allows for an independent red-out of each pixel (sCMOS,CID). - The assumed precision of the measurements (per orbit) would be of the order of 1 mmag for m(UV) ≈ 11 mag and m(visual) ≈ 12 mag.
Stability and Habitability of Multi-Planetary Systems hosted by Binary Stars
Pilat-Lohinger, Elke
Even though we have evidence of about 3000 planets outside the solar system, our Earth is still the only habitable planet we know so far. Therefore, the question arises whether we have to detect solar system like configurations to discover an exo-Earth. Since a large fraction of stars in the solar neighborhood form binary or multiple star systems we consider Jupiter-Saturn like configurations orbiting one stellar component in a binary star system. In this study, we address the stability of various Jupiter-Saturn configurations in tight binary stars where we vary the distance and the eccentricity of the two stars. For all stable configurations, we determine the gravitational perturbations in the HZ using either numerical simulations or a semi-analytical method which has been developed recently. We therefore, get information whether Jupiter-Saturn configurations in binary stars could provide similar conditions for habitable terrestrial planets as in the solar system.
Heterogeneous chemistry on nano dust in the terrestrial and planetary atmospheres (including Titan)
Plane, John
Cosmic dust particles are produced in the solar system from the sublimation of comets as they orbit close to the sun, and also from asteroidal collisions between Mars and Jupiter. Recent advances in interplanetary dust modelling provide much improved estimates of the fluxes of cosmic dust particles into planetary (and lunar) atmospheres throughout the solar system. Combining the dust particle size and velocity distributions with a new chemical ablation model enables the injection rates of individual elements to be predicted as a function of location and time. This information is essential for understanding a variety of atmospheric impacts, including the formation of layers of metal atoms and ions, the subsequent production of meteoric smoke particles, and the role of these particles in ice cloud nucleation and heterogeneous chemistry. Specific examples that will be discussed are: in the terrestrial atmosphere, the formation of mesospheric and stratospheric ice clouds, and polar vortex chemistry; for Venus, the oxidation of CO and removal of O2 on meteoric smoke particles in the hot troposphere; for Mars, production of an Mg+ layer which has recently been observed by the MAVEN spacecraft, and the formation of metal carbonate-rich ice particles which nucleate CO2 clouds in the Martian mesosphere; and for Titan, the production of benzene in the troposphere by the cyclo-trimerization of acetylene on dust particles.
The method of relative velocity calculation for the study of very young asteroid families and pairs
Plávalová, Eva
Asteroid families are groups of minor planets that have a common origin in a catastrophic breakup event. Very young compact asteroid clusters are a natural laboratory in which to study the impact processes and dynamics of asteroid orbits._x000D_ In our paper [1], we define the term very young asteroid families (VYFs), that is to say, younger than 1.6 Myrs, and explain why we have defined this group as being separate from young families (younger than 100 Myr), due to specific characteristics, in particularly, non-gravitational forces which have a minimal effect (which could be negligible) on their dynamics and the role of the initial conditions in VYFs as being more significant._x000D_ We present the method employed to calculate the components of relative velocity using the results of backward numerical integration as a method of studying VYFs. For the most part, the calculation of VYFs' normal component of relative velocity using backward numerical integration, exhibited a clear, deep minimum which was close to the breakup epoch._x000D_ In this presentation, we demonstrate the above method on two VYFs and prove its relevance for studying young asteroid pairs. We have exemplified that the z-component of relative velocity may prove to be a powerful and useful criterion for VYF age estimations._x000D_ _x000D_ References:_x000D_ Rosaev A., Plavalova E. (2018). On relative velocity in very young asteroid families, Icarus, accepted.
New spectra for the Eureka family's smaller members
Polishook, David
Seven asteroids form the Eureka orbital family, named after the largest member, which orbits within the fifth Martian Lagrange point. Dynamical calculations (e.g. Cuk et al. 2015) argue that these seven shared a common origin – a progenitor that disintegrated by multiple YORP-induced spin-ups. Spectral observations of the largest three objects suggest similar olivine-rich bodies (e.g. Polishook et al. 2017), supporting the shared origin theory. Since olivine-rich bodies (a.k.a. A-type asteroids) are extremely rare in the main belt (0.4%; DeMeo & Carry 2013) and since Mars' mantle consist of olivine, we suggested that Eureka and its family are impact ejecta excavated from Mars mantle, and thus may be the only known asteroids linked to a terrestrial planet origin. We will present new measurements of additional family members, scheduled to take place in the coming spring, that will support or dispute previous conclusions. In addition, Cuk et al. (2015) noticed that dynamically, asteroid 2011 SC191 is the most distant family member, and suggested it was ejected from Eureka before the other members. Olivine is highly affected by the space weathering process, which causes an increase in spectral slope (Brunetto et al. 2006). Detecting a reflectance spectrum for this asteroid with a higher spectral slope has the potential to provide constraints on the timescale of the space weathering process on olivine.
Dusty plasma interactions near the Moon and in the system of Mars
Popel, Sergey
We present results of recent self-consistent studies which consider dust and dusty plasmas at the Moon and in the system of Mars. These studies are associated with the future space missions Luna-25 and Luna-27 as well as Phobos-Grunt 2 and ExoMars 2020. The dusty plasma system over the Moon includes charged dust, photoelectrons, and electrons and ions of the solar wind and Earth's magnetosphere. The electrostatically ejected dust population can exist in the near-surface layer over the Moon while the dust appearing in the lunar exosphere owing to impacts of meteoroids present everywhere. Dusty plasmas are shown to be formed in the surface layer over the illuminated part of Mars' satellites Phobos and Deimos owing to photoelectric and electrostatic processes. In view of a weak gravitational field, dust particles rising over the surfaces of Phobos and Deimos are larger than those over the surface of the Moon. In this case, the role of adhesion, which is a significant process preventing the separation of dust particles from the lunar surface, is much smaller on Phobos and Deimos. We discuss also dusty plasmas in Martian atmosphere._x000D_ This work was supported by the Russian Foundation for Basic Research (project no. 18-02-00341).
Definition and epistemology of terra-astronomy
Posch, Thomas
Terra-astronomy is a relatively recent discipline of astronomy, a fact that calls for its precise definition (1) and for a reflection on its epistemological basis (2).(1) I shall argue that terra-astronomy is most clearly defined as the study of individual astronomical objects and phenomena (e.g. the Sun, the Earth’s rotation eclipses, aurorae, particular supernovae, particular comets etc.) based on historical records. Its focus on past events and old pieces of evidence is a feature that it shares with astronomical historiography. However, the aspiration of terra-astronomy is different from many merely historical investigations, namely to ultimately derive conclusions of relevance to contemporary astrophysical research (e.g. a deeper understanding of the solar dynamo or a refinement of the laws governing supernova explosions).(2) This leads to some basic epistemological considerations. I shall base them on Heinrich Rickert’s view according to which there are two prototypical approaches to empirical reality: the ‘historical’ approach and the natural scientific approach, the latter being most distinctly represented by theoretical physics. The first, far from being restricted to ‘data on past events’, focusses on individual phenomena and cultural values. The second, by contrast, usually does not refer to (i.e. it abstracts from) cultural values and aims at establishing universal laws of nature. As I finally try to demonstrate, both astronomy in general and terra-astronomy in particular need to rely on conceptual elements from both approaches.
The angular momentum of galaxies and their haloes as a tracer of galaxy evolution
Posti, Lorenzo
Angular momentum (AM) is one of the pivotal variables determining the differentmorphologies of galaxies. While tidal torques should supply baryons and dark matterwith comparable amounts of AM, it is still unclear what determines which fraction ofthe available AM is eventually incorporated into the galaxies that we observe today.I will show how analytic models in a LCDM framework and the observed propertiesof galaxies (including recent measurements from the SPARC sample) can be foldedtogether to unveil how much AM is present in the gas available to cool and formstars in the galaxy. If star formation proceeds inside-out, from the innermostand AM-poorer regions, we find that (Posti et al. 2017 & 2018 subm.) i) spiralsneed to accrete a significant portion of AM-rich gas from the outer regions(10-50%), while ellipticals must have lost ~40% of the AM initially in the gasdue to mergers and dynamical friction; ii) the fraction of stellar-to-halo AM isa strong, non-linear function of galaxy mass for both morphological types.Comparing our estimate of the stellar-to-halo AM relation with the stellar-to-halomass relation, we find that the efficiencies of star formation and AM retentionclosely follow each other, indicating that the AM distribution of dark matterand baryons are also very well correlated. I will speculate on the constraintson galaxy formation that this implies.
X-ray binaries with neutron stars at accreting and non-accreting stages
Postnov, Konstantin
Results of the population synthesis calculations of X-ray binaries with rotating magnetized neutron stars are presented. A modified version of the BSE population synthesis code is used, supplemented with a detailed treatment of interaction of neutron stars with matter gravitationally captured from stellar wind of the massive companion. Specifically, we discuss several observed classes, including symbiotic X-ray binaries, Be X-ray binaries with X-ray pulsars and with propelling neutron stars at quasi-spherical stage (possible gamma-Cas analogs).
CB4: New Results in Radio Astronomy - Revealing the physics and evolution of galaxies and AGN with radio continuum surveys
Prandoni, Isabella
A wealth of new data from upgraded and new radio interferometers are rapidly improving and transforming our understanding of the faint extra-galactic radio sky. Indeed the mounting statistics at sub-mJy and µJy flux levels is finally allowing us to get stringent observational constraints on the faint radio population, and on the modeling of its various components. In this talk I will provide a brief overview of the latest results, focusing on star-forming galaxies and (low power) Active Galactic Nuclei (AGN), the two populations dominating the faint extra-galactic radio sky. I will conclude by illustrating the role that the Square Kilometre Array (SKA) and its precursors can play in answering the several open questions in this research field.
Young asteroid clusters and their relation to asteroid pairs
Pravec, Petr
In our recent work (Icarus 304, 110, 2018), we studied the membership, size ratio and rotational properties of 13 asteroid clusters consisting of between 3 and 19 known members that are on similar heliocentric orbits. By backward integrations of their orbits, we confirmed their cluster membership and estimated times elapsed since separation of the secondaries (the smaller cluster members) from the primary (i.e., cluster age) that are between 105 and a few 106 years. We ran photometric observations for all the cluster primaries and a sample of secondaries and we derived the cluster size ratios and primary spin periods. We found that 11 of the 13 clusters follow the same trend of primary period vs mass ratio as asteroid pairs that was revealed by Pravec et al. (Nature 266, 1085, 2010). We generalized the model of the post-fission system for asteroid pairs by Pravec et al. (2010) to a system of N components formed by rotational fission and we found excellent agreement between the data for the 11 asteroid clusters and the prediction from the theory of their formation by rotational fission. The two exceptions are the high-mass ratio (q > 0.7) clusters of (18777) Hobson and (22280) Mandragora for which a different formation mechanism is needed. Two candidate mechanisms for formation of more than one secondary by rotational fission were published: the secondary fission process proposed by Jacobson and Scheeres (Icarus 214, 161, 2011) and a cratering collision event onto a nearly critically rotating primary proposed by Vokrouhlicky et al. (Astron. Astrophys. 598, A91, 2017). We found also certain further interesting properties and features of the asteroid clusters that place constraints on the theories of their formation, among them the most intriguing being the possibility of a cascade disruption for some of the clusters. I will compare the asteroid clusters with asteroid pairs and active asteroids, as all these asteroid kinds appear to be related to certain degree.
Astronomy as entrance in STEM capacity building: Developing the community around a new observatory
Premadi, Premana
The requirement of clean dark sky for astronomical observatory puts astronomers face to face with underdeveloped area often with a low population which is still behind in various aspect of modern civilization. Such is the challenge that we met while on our way in establishing a new observatory in Timor island, in the southeastern region of Indonesia. Here we use the universal charm of astronomical observation to raise the awareness of our connectedness to the universe and engage further interest of the local people, and use astronomy as a background, foreground, and inground context for STEM ideas. With the support of IAU Office of Astronomy for Development we managed to put together those STEM ideas into practices that assist the local community in their development while adhering to the clean environment constraint imposed by the observatory. Presently we focus on developing clean and lean method for generating electricity and water. This is strongly in line with the effort towards sustainable development. Here we report on the program strategy and teamwork that we managed to construct that includes members of relevant STEM professional institutions, local universities, schools, and public offices, and on the STEM materials we developed with the primary objective being capacity building. The materials and delivery method can be easily adopted and adjusted for a more general community development program. Indeed this preliminary work has raised the interest of other STEM professional institutions and universities in supporting our program as well as carrying out their own capacity building programs.
Women in astronomy: challenges and actions
Primas, Francesca
A diverse workforce is key to ensure balanced views, inclusive approaches and in the long run larger economical benefits worldwide. Among the different aspects that make-up diversity, the gender dimension of science and technology has become one of the most important and debated issues worldwide, impacting society at every level. Gender equality at large is one of the eight United Nations Millennium Development Goals, which clearly call for action related to science, technology and gender balance.Astronomy’s prime international organisation – the International Astronomical Union – has recognized and supported the needs and endeavours of female astronomers through the establishment of an Executive Committee Working Group, at its XXV General Assembly (Sydney, Australia – July 2003).In this presentation, I will review the main activities and achievements of the Working Group during the past years, with a look to what the future may bring.
Early life on Earth – tracing the physical/chemical process from non-living to living
Pross, Addy
The origin of life on Earth remains one of the most tantalizing scientific questions of all time. In this talk I will describe recent developments in the field that suggest that the chemical process by which inanimate matter was transformed into simplest life and Darwinian evolution are actually one single continuous process. Much of the basis for that unification comes from a new area of chemistry, termed systems chemistry. Studies in that area point to the existence of a previously unrecognized stability kind in nature, dynamic kinetic stability (DKS), applicable only to replicating systems, whether chemical or biological. Consideration of this ‘other’ stability kind allows the driving force for both chemical and biological evolution to be revealed, throwing new light on central biological questions, including what is life, how did it emerge, and how would one make it [1].Reference[1] A. Pross, What is life? How chemistry becomes biology, Oxford University Press, 2nd Ed., Oxford, 2016.
Gaia mission overview and status
Prusti, Timo
Gaia has been operating in its nominal phase since mid-2014 for four years. The operations are smooth and routine. The presentation summarises the scientific performance parameters, the status of the spacecraft and a look into the future.
The extended Planetary Nebula Spectrograph (ePN.S) early-type galaxy (ETG) survey - Kinematic diversity and angular momentum at large radii
Pulsoni, Claudia
We present two-dimensional velocity and velocity dispersion fields, specific and total angular momentum profiles for 33 ETGs into their outer halos (average 6 effective radii, Re). We use Planetary nebulae (PNe) to trace the kinematics to these very large radii where absorption line spectroscopy is no longer feasible. The ePN.S survey is the largest survey to-date of ETG kinematics with PNe, based on data from the Planetary Nebula Spectrograph (PN.S), counter-dispersed imaging, and high-resolution PN spectroscopy. We find that ETGs typically show a kinematic transition between inner regions and halo. Slow rotators have increased but still modest rotational support at large radii. Most of our fast rotators show a decrease in rotation, due to the fading of the stellar disk in the outer, more slowly rotating spheroid. 30% of these fast rotators are dominated by rotation also at large radii, 40% show kinematic twists, misalignments, or rotation along two axes, indicating a transition from oblate to triaxial in the halo. Estimated transition radii in units of effective radii are ~ 1-3 Re and anti-correlate with stellar mass. These results are consistent with cosmological simulations and support a two-phase formation scenario for ETGs.
Exoplanet host-star properties: the active environment of exoplanets
Pye, John
Seven institutes in Europe have combined their expertise in the field of exoplanetary research to develop the European Horizon-2020 ExoplANETS_A project (Grant Agreement no. 776403; started January 2018) under the coordination of CEA Saclay. In the framework of the project, novel data calibration and spectral extraction tools, as well as novel retrieval tools, based on 3D models of exoplanet atmospheres, will be developed to exploit archival data from space- and ground-based observatories, and produce a homogeneous and reliable characterization of the atmospheres of transiting exoplanets. Additionally, to model successfully the exoplanet atmosphere, it is necessary to have a sound knowledge of the host star. To this end, we will collect a coherent and uniform database of the relevant properties of host stars from online archives (e.g. XMM-Newton, GAIA) and publications. These exoplanet and host-star catalogues will be accompanied by computer models to assess the importance of star – planet interactions, for example the ‘space weather’ effects of the star on its planetary system. The knowledge gained from this project will be published through peer-reviewed scientific journals and modelling tools will be publicly released. In this paper, we present early results from the host-star investigations, including the basic observational and physical properties of the systems, and indications of future observations needed to maximize the coverage of the target list (of ~50 – 100 systems).
The black hole spin in coalescing binary black holes and high-mass X-ray binaries
QIN, Ying
Binary stellar systems are unique astrophysical laboratories for the study of black holes (BHs). Accretion of matter from a binary companion gives rise to X-ray emission, bringing them to the X-ray binary phase, and the recent gravitational wave observations enabled us to witness the last few seconds of the lives of coalescing binary BHs. In fact, some types of high-mass X-ray binaries are considered as the potential immediate progenitors of Gravitational-Wave sources. The BH spin is one of the observable quantities in both types of systems, and it carries significant information about their past evolutionary history. In the last decade, the measurement of the spin of BHs has become possible for about a dozen of X-ray binaries. The observed BH spins in Galactic field in low-mass X-ray binaries can be explained through accretion onto the BH after its formation. But for three well-known high-mass X-ray binary sources (Cyg X-1, LMC X-1 and M33 X-7), their high spins (a_* > 0.8) are believed to have a different origin. In our proposed model, such high spins can be well explained when the BH progenitor star looses its hydrogen envelope via a case-A mass-transfer, and never expands to become a giant star, while an inefficient angular momentum transport mechanism seems to also be required. For the case of coalescing binary BHs, we study the immediate progenitor of the binary BH is in a close binary system composed of a BH and a helium star. Upon core collapse, the helium star produces a BH (the second-born BH in the system) with a spin that can span the entire range from zero to maximally spinning. We find an anti-correlation between the merging timescale of the two BHs, T$_{\rm merger}$, and the effective spin $\chi_{\rm eff}$. We predict that, with future improvements to AdLIGO's sensitivity, the sample of merging binary BH systems will show an overdensity of sources with positive but small $\chi_{\rm eff}$ originating from lower mass BH mergers born at low redshift.
Radial Velocity Measurements with m/s Precision in the Visible and Near-IR
Quirrenbach, Andreas
Precise radial velocity measurements require careful attention to detail not only in the construction of the spectrograph, but also in the calibration and data reduction procedures. While laser frequency combs provide highly stable wide-band wavelength references, the combination of hollow-cathode lamps with Fabry-Pérot etalons is a cost-effective alternative. To ensure stable coupling of starlight as well as calibration light into the spectrograph, the light-scrambling properties and modal behavior of the fiber feeds must be well understood. Unexpected problems lurk in seemingly innocent active components such as steering and switching mirrors in the front end and calibration unit, as higher-order errors due to coupling between misalignments and fiber modes cannot be neglected.Detectors are never perfect, and near-infrared arrays present a set of challenges that is not encountered in CCDs, associated e.g. with cosmetic defects, electronic ghosts, and – most insidiously – memory effects. The latter place strong constraints on the calibration strategy, as exposing the detectors to bright lines of calibration sources shortly before taking science data must be avoided.Equal care is required in the data reduction, from processing of the raw data to extraction of the spectra, barycentric correction (requiring precise knowledge of the photon-weighted midpoint of the exposure), and computation of the radial velocity with a suitable cross-correlation technique. Compared to spectrographs working mostly in the blue, red-sensitive instruments are much more sensitive to subtleties in the treatment of telluric contamination, as non-optimal approaches can lead to systematic periodic effects on the several m/s level.We will discuss the end-to-end process of obtaining highly precise radial velocities over a wide wavelength range based on our experience with CARMENES, the first spectrograph that has been optimized for exoplanet searches in the red and near-infrared (0.52-1.72µm).
Families in the Outer Solar System
Ragozzine, Darin
Though Hirayama's discovery of families in the asteroid belt is 100 years old, the discovery of the first collisional family in the outer solar system was only ~10 years ago; in both cases about 1000 objects were known. Unlike asteroid families, Brown et al. 2007's discovery of a collisional family around the dwarf planet Haumea relied heavily on unique spectral features, but Ragozzine & Brown 2007 showed that the family was dynamically clustered. In fact, the family was too dynamically clustered: all objects with the unique spectral features of the Haumea family lie within dv < 150 m/s, which is an order of magnitude tighter than would be expected based on a standard collision on such a large body (escape velocity of ~900 m/s). This mystery persists to this day with several hypotheses proposed (e.g., Schlichting & Sari 2009, Leinhardt et al. 2010, Marcus et al. 2011, Ortiz et al. 2012, Campo Bagatin et al. 2016). With a new calculation of proper elements tripling the number of family members from 8 to ~25 (Maggard & Ragozzine, in prep.), we use a sophisticated model of the three-dimensional distribution of family members to rule out some of the leading hypotheses (Proudfoot & Ragozzine, in prep.). These calculations show that Haumea family members can now be identified dynamically. We also investigate the possibility of using direct backwards integration to determine the age of the Haumea family and to identify new outer solar system families that formed in the last ~GYr (Marcus et al. 2011). Such advanced modeling is possible in the Kuiper Belt because the Yarkovsky effect is unimportant, but many of our statistical techniques could be adapted to great use in studying asteroid families.
Magnetic fields in simulations of ram pressure stripped galaxies
Ramos-Martinez, Mariana
The removal of the interstellar medium (ISM) of disk galaxies through ram pressure stripping (RPS) has been extensively studied in numerous simulations. Nevertheless, the role of magnetic fields (MF) on the gas dynamics in this process has been hardly studied, although the MF influence on the large-scale disk structure is well established. With this in mind, we present 3D magnetohydrodynamic (MHD) simulations of disk galaxies subject to RPS, under the wind-tunnel approximation, with different disk inclination angles to study the evolution of the galactic MF and its impact in the gas stripping. The main effect of including a galactic MF is a flared disk. From our simulations, we observe that when the intracluster medium (ICM) wind hits a galaxy, the gas in the disk is compressed, leading to an enhancement of the MF intensity in the upstream side. Since the gas is bound by the MF, we observe that in face-on and nearly face-on (slightly inclined) disks, the gas is swept by the wind in ring-like structures and drags the field lines with it, so that they show a more symmetrical configuration, similar to the initial one. In the case of highly inclined and edge-on disks, the configuration of the field is asymmetric compared to the initial one, the field lines are compressed in the upstream side and more extended towards the downstream side. Since the magnetic field is dragged with the swept gas of the disks, the ICM is magnetized in the downstream side up to ~0.1µG, where nearly face-on disks contribute the most, given that the tail developed by the swept gas is more extended than in highly inclined models.
The mass-loss characteristics of AGB stars, an observational view
Ramstedt, Sofia
The massive outflows of gas and dust which characterize giant stars on the AGB, builds a cool circumstellar envelope readily observed at sub-millimeter wavelengths. Observations will give the amount of matter lost by the star, the wind velocity (in the case of spectral line observations), and, when the spatial resolution is sufficient, the wind evolution over time.To gain detailed insight into the mass-loss process, we study the nearby (within 1 kpc) stars. Through these investigations we aim to determine the best constrained wind properties available. By combining this with theoretical results, mass-loss estimates for more distant sources can also be significantly improved. ALMA has opened up new opportunities to study the winds of AGB stars. The DEATHSTAR project (www.astro.uu.se/deathstar) has mapped the circumstellar CO emission from ~50 nearby M- and C-type AGB stars. The data will initially be used to give a definitive mass-loss prescription for the sample sources, but the large-bandwidth observations opens for many different legacy projects. The current status and results will be presented.
Astrometric studies of exoplanets with Gaia and GaiaNIR
Ranalli, Piero
Most of the exoplanets known today have been discovered by observingradial velocity motions and/or transits. The astrometric shifts ofstars due to planetary orbits have been detected so far only in veryfew cases, despite a long history of interest and claims. However, itis estimated that ~20,000 planets will be detected at the end ofGaia's 5-year mission. The newly discovered planets will notnecessarily have the same orbital properties of those currently known,because of the different efficiency of the various detection techniques(astrometry, transits, radial velocities, ...). Gaia in particular hasa potential to detect long-period planets and to obtain solidmeasurements of the orbit inclination.We have recently reviewed Gaia's capabilities for exoplanet detectionusing an extensive set of simulations. In this talk, I will presentthe efficiency with which Gaia will be able to detect planets at theend of the 5 yr mission and after a 10 yr extension. Focusing on theperiod, eccentricity, and inclination, I will show the accuracy withwhich parameters will be recovered. I will show how long-periodplanets (periods up to ~20 yr) can be detected, and uncertainties oneccentricity greatly reduced, if the mission is extended to a total of10 yr. I will consider multiple-planet systems and show Gaia'spotential in disentangling periods, eccentricities, and inclinations.Finally, I will consider the proposed infrared astrometric missionGaiaNIR, and show it potential for detecting planets, and how its datacould be merged with Gaia's to detect planets with periods of severaldecades.
The relevance of the Gaia-ESO survey on the Galactic metallicity gradient
Randich, Sofia
TBA
Brightness Variations of Sun-Like Stars
Reiners, Ansgar
Observations of stars other than the Sun provide information that are complementary to long-term solar datasets. They show whether solar variability is typical for a star like the Sun and how the Sun might have looked like at other times. The talk provides a summary about what is known about variability from sun-like stars and how we can use this data to inform our understanding of solar and stellar physics.
Formation, Evolution, and Galaxy Population Properties of Proto-Clusters: Insights from the Hydrodynamic Cosmological Simulation Magneticum
Remus, Rhea-Silvia
Using the power of the state-of-the-art hydrodynamical cosmological simulation suit Magneticum Pathfinder, I study the formation of proto clusters at redshifts 4-5, and the evolution of such structures into present-day massive cluster systems. I will present star-formation and gas properties of the galaxy cluster members in comparison to state-of-the-art observations, as well as kinematical properties of such very early galaxies, and I will demonstrate what we can learn from the combined approach of simulations and observations about the build-up of structures and the laws of star formation in the early phases of our Universe.
Connecting angular momentum, mass and morphology: insights from the Magneticum simulations
Remus, Rhea-Silvia
Understanding the connection between the angular momentum properties of a galaxy and its formation history and thus its morphological properties is one of the most intriguing quests in extragalactic astrophysics. State-of-the-art hydrodynamical cosmological simulations of large volumes with sufficient resolution to trace galaxy properties over a large range of galaxy masses and redshifts are essential to disentangle the different processes in galaxy formation that lead to the huge variety in morphological and kinematical properties observed in present day galaxies, but only recently became available. One such simulation set are the Magneticum Pathfinder simulations. I will present insights obtained from these simulations with regard to the close connection between the angular momentum, the mass, and the morphology of galaxies, and how this is correlated to the individual formation pathways of galaxies. Furthermore, I will highlight the importance of observational measurements of the angular momentum of galaxies even though they are difficult to obtain. Finally, I will demonstrate how the kinematical properties measured with modern IFUs connect to the angular momentum evolution, and how this is correlated to galaxy properties at different redshifts.
Astronomical Education and outreach activities for astronomy in Mongolia
Renchin, Tsolmon
It is necessary to develop advanced research for astronomy in Mongolian universities using modern techniques. We do not have a graduate education and curriculum for astronomy in Mongolian universities. There is a lack of astronomical professors and training opportunities for students in universities and colleges. We desperately need more advanced research opportunities and education in astronomy in Mongolia. In order to develop higher education for astronomy it is important to cooperate with international communities and universities. International activities for astronomy began when Mongolia joined the IAU at the General Assembly held in Prague in August 2006, because space scientists, astronomers and researchers in Mongolia are coming to understand that astronomy can help Mongolian science development. For instance, astronomy can increase general interest and encourage public engagement in the sciences.Meantime outreach astronomy only is developing in Mongolia. There are educational activities for school children and school teachers in urban and rural areas. Specially outreach activities are going in heritage areas. Astronomy heritage activities also will be shared in this talk. To experience from international networks at the IAU meeting is great opportunity not only for university professors but also for the researchers in the Mongolian observatory in Ulaanbaatar. We hope the IAU meeting allow us to discuss future collaboration and cooperation with different universities in order to develop graduate degree study in Mongolian universities and possible exchange activities and experience educational curriculum and teaching materials. Advanced research for astronomy is needed in Mongolia.
MWC 656: the first HMXB containing a BH orbiting a Be star
Ribó, Marc
High Mass X-ray Binaries (HMXBs) have been found in a veriety of configurations depending on the donor and the accretor properties, as well as on the binary orbit parameters and mass transfer channel. Indeed, a significant fraction of HMXBs are composed of Be stars orbited by neutron stars (NSs). However, binary population synthesis models predicted the existence of Be stars orbited by black holes (BHs) as well, although their detection had been elusive until recently. After a possible gamma-ray flare detected by the AGILE satellite, the Be star MWC 656 was discovered to be a member of a binary system. Subsequent radial velocity studies revealed that the orbiting compact object is in fact a BH. X-ray observations showed the binary system to be in quiescence, allowing thus studies of quiescent BHs in HMXBs for the first time. Simultaneous X-ray/radio observations have allowed us to study the accretion/ejection coupling in BH HMXB for the first time. Our results show that the obtained X-ray/radio luminosities for this quiescent BH HMXB are fully compatible with those of the X-ray/radio correlations derived from quiescent BH low mass X-ray binaries. These results reveal that the accretion/ejection coupling in stellar-mass BHs is independent of the nature of the donor star and the mass transfer channel. We note that this is the first stellar-mass BH that has not been discovered by its prominent X-ray emission. Finally, studies of the formation and evolution of Be/BH systems have been conducted, revealing that evolved descendents of these systems in nearby galaxies can lead to detectable gravitational waves from NS-BH mergers. We will review all these discoveries related to the first Be/BH system MWC 656 and provide an outlook of the current observational efforts aimed at better understanding Be/BH systems.
Exploring the Origins of the Earth's Nitrogen
Rice, Thomas
It has long been a goal of astrochemistry to connect measurements of interstellar molecules to the formation of planetary systems such as our own. Observations of cometary ices and interstellar volatiles have allowed for some progress, but understanding the origins of volatiles on terrestrial planets remains a difficult task. It is the goal of this work to outline the connection of interstellar nitrogen molecules to the nitrogen content of terrestrial bodies in our Solar System. What form is nitrogen in when it gets locked into meteoritic planetesimals? While the vast majority of a disk's nitrogen is thought to be found in atomic N and N2 (Schwarz & Bergin 2014), these species do not freeze as readily into solids, and therefore cannot be the progenitor of Earth's nitrogen. Based on an analysis of Herschel spectra toward the star-forming regions Orion KL and IRAS 16293, we have investigated whether N-bearing organic molecular ices can trace the nitrogen that ultimately becomes incorporated into terrestrial worlds. We suggest that refractory dust, not molecular ices, was the bulk carrier of nitrogen to comets. But, importantly, the high 15N enrichment in both nitrogen-bearing ices and in meteoritic nitrogen, not shared by ISM dust, indicates that these 15N-enriched N-bearing ices were an important contributor to the nitrogen in planetesimals and likely to the Earth.
New Astrometric Directions in Globular Star Cluster Research
Richer, Harvey
In this talk I will cover a number of new areas of research on globular star clustersthat are being made possible with astrometric observations. Among these are the influence of Gaia, the use of ultraviolet imaging and the enormous effect thatJWST will have. I will cover issues ranging from the distances to the clusters,the search for Intermediate Mass Black Holes and cluster brown dwarfs.
Initial Results from the Transiting Exoplanet Survey Satellite (TESS)
Ricker, George
The Transiting Exoplanet Survey Satellite (TESS)--a NASA Astrophysics Explorer-- is expected to discover thousands of exoplanets in orbit around the brightest stars in the sky. The launch is to take place in March 2018 from Cape Canaveral on a SpaceX Falcon 9 rocket._x000D_ In a two-year survey, TESS will monitor ~200,000 pre-selected bright stars for planetary transits in the solar neighborhood at a 2-minute cadence. This survey will identify planets ranging from Earth-sized to gas giants, around a wide range of stellar types and orbital distances. TESS will also provide full frame images (FFI) at a cadence of 30 minutes or less. These FFI will provide precise photometric information for every object within the 2300 square degree instantaneous field of view of the TESS cameras. In total, more than 30 million stars and galaxies brighter than magnitude I=16 will be precisely photometered during the two-year prime mission. In principle, the lunar-resonant TESS orbit will provide opportunities for an extended mission lasting more than a decade, with data rates of ~100 Mbits/s._x000D_ An extended survey by TESS of regions surrounding the North and South Ecliptic Poles will provide prime exoplanet targets for characterization with the James Webb Space Telescope (JWST), as well as other large ground-based and space-based telescopes of the future. The TESS legacy will be a catalog of the nearest and brightest main-sequence stars hosting transiting exoplanets, which should endure as the most favorable targets for detailed future investigations._x000D_ Initial results from the first few months of the TESS mission will be presented.
Common Envelope Evolution of Massive Binaries
Ricker, Paul
The discovery via gravitational waves of binary black hole systems with total masses greater than 60M? has raised interesting questions for stellar evolution theory. Among the most promising formation channels for these systems is one involving a common envelope binary containing a low metallicity, core helium burning star with mass ~ 80 – 90M? and a black hole with mass ~ 30 – 40M?. For this channel to be viable, the common envelope binary must eject more than half the giant star's mass and reduce its orbital separation by as much as a factor of 80. I will discuss issues faced in numerically simulating the common envelope evolution of such systems and present a 3D AMR simulation of the dynamical inspiral of a low-metallicity red supergiant with a massive black hole companion.
The IAU and the Impact Hazard
Rickman, Hans
Almost 30 years have now passed since the risk of an asteroid impact on the Earth with global consequences became a political issue as well as a scientific one. The IAU took an interest in these issues early on, recognising its potential to act as an international advisory body. One of the first initiatives was the formation of the Working Group for Near Earth Objects at the XXIst IAU GA in Buenos Aires 1991. My terms as AGS and GS (1997-2003) coincided with the time that impact risks due to specific asteroids at upcoming encounters with the Earth were first estimated statistically using orbital solutions and integrations. Hand in hand with this came sensationalist writings in news media, and astronomers found themselves in a role as doomsday prophets that they never intended to play. I will briefly summarise my personal impressions of what the IAU was doing in this situation.
NIRCam for JWST: New Science Near and Far
Rieke, Marcia
NIRCam has been built with deep surveys as a prime design driver, and the resulting camera will be superb for such observations. These same design criteria, with the addition of other components, have led to a NIRCam that ensures stunning capabilities in many other areas such as exoplanet studies where NIRCam can observe transits spectroscopically and architectures of exoplanet systems via coronagraphy with NIRCam's complement of 3 to 5 micron filters providing diagnostics of exoplanet atmospheres. NIRCam's medium and narrow filters provide new capabilities for studying obscured star formation and ices.
Finding Embedded AGN with MIRI
Rieke, George
I will illustrate the breakthroughs enabled by the Mid-Infrared Instrument (MIRI) on JWST, through the example of identifying embedded active galactic nuclei (AGN). Multiple approaches have been used to find AGN, with significant overlap in the samples identified. However, some objects meet one criterion but not others. A critical example is that power law spectra and other clues in the infrared reveal AGN candidates not detected in the deepest X-ray surveys. Even the hard X-rays detected with NuStar fail to find some AGN where we expect them. These results and theoretical models imply that AGN are likely to be hidden during their early development in extremely dense and heavily obscuring interstellar clouds of gas and dust. MIRI can find these hidden AGN in multiple ways. First, MIRI and NIRCam multiband photometry can identify galaxies where the spectral minimum around 4.5 microns (the longest wavelength where stellar photosphere emission dominates over aromatic bands) is filled in by emission by an embedded AGN. This approach is similar to the color-color diagrams developed for Spitzer IRAC and WISE photometry, but much more powerful because the MIRI bands allow this minimum to be isolated cleanly and uniformly for 0 < z < 2.5. Second, using the MIRI IFU/MRS provides a new level of sensitivity to high-excitation fine structure lines, particularly [Ne VI] at 7.65 microns, unique because of its high ionization potential (158 eV), high critical density, and availability to MIRI out to z = 2.5. Third, even the most deeply embedded AGN such as Mkn 231 heat the surrounding dust and much of their energy emerges as a mid-infrared pseudo-blackbody. This emission can be identified through its dilution of the stellar CO fundamental absorption bands (4.5 – 4.75 microns, within the MIRI range for z > 0.03), and of the aromatic features. The latter two approaches are enhanced by imaging with the IFU, probing whether the AGN signature is confined tightly on the galaxy nucleus.
Star forming galaxies as revealed by gravitational lensing and JWST
Rigby, Jane
Gravitational lensing will uniquely enable JWST to spatially resolve the sub-kiloparsec physical processes within galaxies over most of cosmic time. HST images of lensed galaxies have revealed the ubiquity of <100 parsec star-forming clumps; JWST will dissect each clump spectroscopically, showing the inner process of galaxy assembly. For the first time in the distant universe, JWST will map where stars are forming at high spatial resolution and in an extiction-robust way, using the spectral diagnostics of H-alpha, Pa-alpha, and 3.3um PAH emission. Mid-IR images will reveal the locations of previous generations of stars, showing how star formation has progressed spatially. JWST will measure the physical conditions of nebular gas in these star formation regions -- ionization parameter, pressure,and metallicity -- and how those conditions vary from region to region. JWST will trace the outflows that are launched from these star-forming regions via broad H alpha wings and Na D absorption. The approved DDT-ERS program "TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star formation" will demonstrate these techniques on four of the brightest lensed galaxies known. I will also explore the synergies with rest-frame UV spectra from ground-based telescopes.
Variability Phenomena in the Gaia second Data Release (DR2)
Rimoldini, Lorenzo
Gaia is an all-sky multi-epoch ESA mission observing over a billion sources during its five-year nominal mission duration. Besides astrometric and spectroscopic measurements, it collects photometric time series data in three pass-bands that allow us to detect and describe variability phenomena in an unprecedented way. The Gaia second data release published in April 2018 is based on 22 months of observations and contains classified and characterised light curves for more than 500,000 variable source candidates consisting of: RR Lyrae stars, Cepheids, Long Period Variables, Delta Scuti/SX Phoenicis and BY Draconis stars. A list of various short time-scale variability phenomena is also included. We present an overview of this rich data set, the diverse properties of these variable sources, and their distribution in the colour-magnitude diagram. Though this is still a relatively small fraction of the variable stars that Gaia detects, these catalogues are already among the largest ones ever published.
The Near-Infrared Cepheid distance scale based on VMC and Gaia data: a baseline for ELT observations
Ripepi, Vincenzo
We present new accurate Period-Luminosity (PL) and Period-Wesenheit (PW) relations in the J,Ks bands, based on a sample of more than 4000 Classical Cepheids in the Large Magellanic Cloud (LMC) in the context of the VISTA Magellanic Cloud (VMC) Survey. The extreme precision of these data allows us to study the geometry of the LMC and to establish a firm baseline for extragalactic Cepheid distance scale studies. The zero points of the PL and PW relations will be calibrated with great accuracy by using the parallaxes that will be released on April in the context of the Gaia Data Release 2.These relationships will be of fundamental importance in the ELT Era. Indeed, we plan to useE-ELT+MAORY+MICADO to extend the extragalactic distance scale of Classical Cepheids, with crucial impacts on the calibration of secondary distance indicators and on our knowledge of Ho. To this aim, we discuss the prospects to observe bright Classical Cepheids in a sample of galaxies with distances ranging from Virgo to Coma, possibly containing SNIa or other secondary distance indicators. These data would allow us not only to constrain, for the first time in one step, the Hubble constant, but also to provide an independent test of the accuracy of various types of secondary distance indicators.
Classical Cepheids Near-Infrared periodo-luminosity relations based on Vista Magellanic Cloud (VMC) survey data and Gaia parallaxes
Ripepi, Vincenzo
We present new accurate Period-Luminosity (PL) and Period-Wesenheit (PW) relations in the J,Ks bands, based on a sample of more than 4000 Classical Cepheids in the Large Magellanic Cloud (LMC) in the context of the VISTA Magellanic Cloud (VMC) Survey. The extreme precision of these data allows us to study the geometry of the LMC and to establish a firm baseline for extragalactic Cepheid distance scale studies. The zero points of the PL and PW relations will be calibrated with great accuracy by using the parallaxes that will be released on April in the context of the Gaia Data Release 2. These relationships will be of fundamental importance in the next future, when JWST and ELT will progressively enter in operation.
IAU100: Uniting our World to Explore the Universe
Rivero Gonzalez, Jorge
In 2019, the International Astronomical Union (IAU) will celebrate its 100th anniversary (IAU100). To commemorate this milestone, the IAU will organise a year-long celebration to increase awareness of a century of astronomical discoveries as well as to support and improve the use of astronomy as a tool for education, development and diplomacy under the central theme "Uniting our World to Explore the Universe."Following the success and the lessons learnt of the International Year of Astronomy 2009 (IYA2009), the IAU100 celebration will stimulate worldwide interest in astronomy and science by reaching out to the global astronomical community, national science organisations and societies, policy-makers, students and families and the general public.The IAU is preparing a comprehensive programme of Flagship initiatives to reach out the targeted audiences worldwide through the IAU National Outreach Contacts network, other partner global/regional networks, and local astronomical societies. The IAU100 activities will take place at global and regional levels, and especially at the national and local levels.In this talk, we will present an overview of the initiative, including goals, governance structure, target audiences, Flagship Programmes, dissemination actions and progress on the implementation. In addition, we will discuss opportunities for the organization of grass-root activities under the framework of the initiative.
The Be stars in the Be X-ray binaries
Rivinius, Thomas
Rapidly rotating B-type stars with gaseous mass-loss disks in Keplerian rotation are common central objects in X-Ray binaries. After briefly introducing these Be stars and their physics in general, I will review their disk properties. The disks are well understood in a viscous framework, and their typical parameters have been established for a large number of (supposedly, this statistics will be discussed as well) single Be stars in the recent years. According to the current observational evidence, the Be stars and disks found in BeXRBs are well within the boundaries known from single Be stars, which provides important limits for modeling. New results have also been obtained on the orbital disk truncation and other tidal and radiative effects of the companion objects on the disk.In turn, BeXRBs also provide constraints for understanding single Be star disks, as they make the outer regions of the disk observable, which are not usually accessible to observation except in the radio regime.
S0 galaxies are faded spirals: clues from their angular momentum content
Rizzo, Francesca
The distribution of galaxies in the stellar specific angular momentum versus stellar mass plane (j*-M*) provides key insights into their formation mechanisms. In this talk I will show how I determined the location in this plane of a sample of ten field/group unbarred lenticular (S0) galaxies from the CALIFA survey. I performed a bulge-disc decomposition both photometrically and kinematically to study the stellar specific angular momentum of the disc components alone and understand the evolutionary links between S0s and other Hubble types. I found that eight of the S0 discs have a distribution in the j*-M* plane that is fully compatible with that of spiral discs, while only two have values of j* lower than the spirals. These two outliers show signs of recent merging. These results suggest that merger and interaction processes are not the dominant mechanisms in S0 formation in low-density environments. Instead, S0s appear to be the result of secular processes and the fading of spiral galaxies after the shutdown of star formation.
2024+: Characterizing Exoplanets in the Era of ESO's 39m ELT
Rodler, Florian
In the next decade, the three extremely large telescopes with diameters from 24m to 39m will dramatically extend our knowledge about the composition, dynamics and the structure of exoplanet atmospheres. The unprecedented size of these telescope will permit high-contrast direct imaging of mature planets around stars in the solar neighborhood at orbital separations closer than 1 AU, and high-dispersion spectrographs will open a window to a detailed study of exoplanet atmospheres including weather patterns and cloud properties therein. The combination of high-contrast direct imaging with high-dispersion spectroscopy, to be realized in the first-generation instrument METIS at ESO's 39m ELT, will allow us to measure thermal emission of terrestrial planets in the habitable zone around nearby M-dwarfs. Being capable of inspecting the atmospheres of rocky worlds, the extremely large telescopes will bring us close to the answer of one of the most fundamental questions: does life exist beyond Earth?In my contribution, I will review the capabilities of the instruments suitable for exoplanet characterization at ESO's 39m ELT, METIS, HARMONI, EPICS and HIRES, and will discuss their huge impact on the research field of exoplanet atmospheres.
Quantifying the suppression of the (un)-obscured star formation in galaxy cluster cores at 0.2 < z < 0.9
Rodriguez-Munoz, Lucia
We present the quantification of the star formation (SF) in the inner cores (R=0.3R200) of 24 massive galaxy clusters at 0.2 < z < 0.9 observed by the Herschel Lensing Survey and the Cluster Lensing and Supernova survey with Hubble. The multi-wavelength photometry (rest-frame UV-to-far-IR) provided by these programmes allows us to identify and accurately characterize star-forming cluster members, as well as quantifying their SF as traced by the direct emission of young stars and the emission of dust heated by the SF processes. We apply the same methodology to consistently select and analyze comparable field samples from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. We compare the fraction (F) of color-selected star-forming galaxies (SFGs), and their average star formation rates (SFR) and average specific star formation rates (sSFR=SFR/M*, where M* is the stellar mass), in stellar mass-limited (log M*/MSun > 10) samples of cluster and field galaxies. We find that in the inner regions of intermediate-z clusters, the SF is suppressed in terms of both the fraction of SFGs and the rate at which they turn gas into stars. Clusters display F values on average a factor ~2 smaller than the field, a factor ~5 smaller if we consider only mid- or far-IR-detected galaxies. Furthermore, F appears to evolve faster with z in the clusters than in the field for both galaxy subsamples. In cluster cores SFGs present average SFR and sSFR typically ~0.3 dex smaller than in the field along the whole z range covered. Our results globally favor environmental quenching scenarios with a dominant contribution of slow physical processes in cluster galaxies (such as, e.g., strangulation), although they could also be compatible with other rapid quenching processes (such as, e.g., ram-pressure stripping) turning off infalling galaxies forming stars very actively.This work will be published in Rodriguez-Muñoz et al. 2018 (submitted to MNRAS).
WG Network for Astronomy School Education
Ros, Rosa
TBA
The system of modified proper elements for the study of very young asteroid families and pairs
Rosaev, Alexey
It is evident that proper elements are not effective in the process of studying very young asteroid families (VYFs) and pairs. Many examples of complex dynamic behavior can be observed in the Datura family [1]. Another noticeable example is the resonant behavior of the node longitude in the Emilkowalski family [2]. Additionally, for a more in-depth study of such young compact asteroid clusters and pairs, the values of orbital elements at the epoch t=0 are very important._x000D_ All facts above argue in favour of the construction of a specific system of proper elements for VYFs. We suppose the Fourier approximation of backward numeric integration will be sufficient, but with the following modifications:_x000D_ 1) The observed time interval is shorter; no larger than 1.6 Myrs, which may be optimised form case to case. 2) All resonance terms are used. This is important, because the respective periods may be longer than the cluster’s existence so averaging cannot be applied. 3) Similarly, the effect of the most massive asteroids may be expressed in an explicit form. 4) Information concerning the non-gravitation effects (Yarkovsky etc.) is necessary where it is known._x000D_ In this presentation we show the nonlinear approximation requirement for node longitude and inclination evolution for the (6070) Rheinland and (54827) 2001 NQ 8 pair and some VYFs._x000D_ We believe that the construction of an established, solid base of modified proper elements can strongly accelerate our understanding of the nature VYFs and pairs._x000D_ _x000D_ References:_x000D_ Rosaev A., Plavalova E.: (2018) On relative velocity in very young asteroid families., Icarus, accepted. _x000D_ Nesvorny, D., & Vokrouhlicky, D. (2006). New Candidates for Recent Asteroid Breakups. The Astronomical Journal , 132, 1950-1958. doi:10.1086/507989
Hypervelocity stars as powerful dynamical tracers of dark matter
Rossi, Elena Maria
In this talk, I will review theoretical and observational efforts to use a unique class of objects to trace the amount and shape of dark matter in our Galaxy: hypervelocity stars. These are observed in the halo with velocities in excess of the local escape speed and trajectories consistent with coming from the Galactic Centre. The current sample of ~20 has been found in the SDSS survey and I will show how it has been exploited to constrain the dark matter halo. I will also look into the near future and show the prospects for Gaia to increase the sample by a factor of 10 and our forecasting on how dark matter constraints can be improved using the Gaia larger and less bias sample.
The Large and Small Magellanic Clouds
Rubio, Monica
The Large and Small Magellanic clouds (LMC, SMC) are the best local templates for studying the life cycle of the ISM and star formation in low metallicity environments (LMC;Z=0.5 Zo and SMC, Z=0.2 Zo). Their proximity (LMC: D = 50 kpc; SMC: D = 60 kpc), provide a unique opportunity to resolve individual clouds, allowing us to conduct detailed studies of the different phases of the ISM in low-metallicity environments using various gas and dust tracers. We will present the latest results obtained in the study of the physical properties of the star formation regions, the molecular gas, the new generation of stars and its effect of environment in these regions. These studies provide key insights into the star formation process at low metallicities, which is crucial to interpret observations of high-z galaxies.
Isolating local from foreground Faraday contributions
Rudnick, Lawrence
In order to study the interactions of radio galaxies with their thermal environments or to use background polarized sources as probes of foreground magnetized plasmas, it is necessary to separate the contributions from those components. Little information is currently available on how the individual properties of radio galaxies, such as their size or morphology, can be used to assess contributions local to the source. In this talk, we will explore the relationship between the physical size of radio galaxies and their Faraday properties, using several different samples. We find that larger sources are more highly polarized, contrary to the expectations of depolarization from unrelated foreground screens, so that such effects will have to be controlled in any studies using background polarization probes. This work is supported, in part, by NSF grant AST17-14205 to the University of Minnesota.
The AWHI comes of age: three potential astronomical World Heritage sites for 2019
Ruggles, Clive
Since 2008, the IAU (at first through its Astronomy and World Heritage WG, then through C.C4) has been working in partnership with UNESCO to advance its Astronomy and World Heritage Initiative (AWHI), which seeks to protect and promote astronomical heritage that is significant on a global scale and to expedite the nomination of World Heritage Sites relating to astronomy._x000D_ This has involved developing — in conjunction with UNESO's advisory body ICOMOS — robust general principles for assessing the value, and potential "outstanding universal value", of different types and categories of scientific and technological heritage relating to astronomy._x000D_ This long-term process is now beginning to bear significant fruit. Three countries are in the process of nominating astronomically related properties as potential World Heritage Sites for inscription in 2019: Peru (Chankillo astronomical complex), Spain (Risco Caido and the sacred mountains of Gran Canaria Cultural Landscape) and the United Kingdom (Jodrell Bank Observatory)._x000D_ This presentation will briefly review the cases being made in support of these potential World Heritage Sites and the potential for further global recognition of key astronomical heritage in the near future.
EXOFIND: RV fitting with stellar activity and reliable Bayesian model comparison
Rukdee, Surangkhana
Upcoming cm-precision radial velocity (RV) surveys aim to detect Earth mass planets orbiting low-mass cool stars. Stellar activity can however easily corrupt the small RV signal. Additionally, most current RV fitting methods cannot reliably decide whether the data support 0,1,2 or 3 planets, as the Extremely Precise Radial Velocities (EPRV) Evidence Challenge recently uncovered. Our EXOFIND Python package aims to solve these two problems: 1) We characterize a red noise Gaussian process from stellar activity indicators and apply it to the RV shifts while propagating uncertainties. 2) For rigorous model comparison (0,1,2,3 planets), we use nested and importance sampling. With real and simulated data, we verify that our approach is practical to run and avoids false positives. EXOFIND will be released as open source software to the community.
The Solar Wind over the Last Four Sunspot Cycles
Russell, Christopher
The near-Earth solar wind has been monitored continuously now for over 4 sunspot cycles, and quite complete records are available for SC 21-24. The interplanetary magnetic field rises and falls in synchronism with the sunspot cycle, as would be expected since the sunspot cycle is a phenomenon of increasing and decreasing photospheric magnetic field. With the possible exception of corotating high-speed streams, the solar wind plasma seems less controlled by the phase of the solar cycle. However, one long-term change in solar wind density has occurred with what appears to be a relatively sudden onset at the start of cycle 23. The median solar wind density at 1 AU dropped from about 8 to about 6 cm-3. While one might suspect such a change to be an instrument/technique associated effect, it appears to be a physical effect that has now persisted through solar cycles 23 and 24. This affects the solar wind dynamic pressure and hence the size of the Earth’s magnetosphere, for example. We consider this change in light of the contemporaneous weakening of the solar activity cycle at that time. Given that the solar wind measurements reflect only what is occurring in the ecliptic plane at 1 AU, we use the combination of PFSS models of solar wind source mapping and ENLIL models of the solar wind to assess the relationship between the related changes in the coronal field structure and the solar wind structure. In particular, we compare the coronal field and solar wind models from earlier cycles with those from cycles 23 and 24 to provide insight into the effects that may be responsible for the observed changes in the solar wind.
The Dawn Mission: Latest Results
Russell, Christopher
The Dawn mission is currently in its third successful year of exploration of the dwarf planet Ceres. Very little was known about Ceres prior to Dawn’s arrival, but much has been learned in the last three years. Perhaps most importantly, Ceres is a wet body. It has ice close to the surface and shows evidence of cryovolcanism and the delivery of brines to the surface. Some ice is exposed and appears to undergo changes with time. A temporary atmosphere has been observed stimulated by energetic solar proton events and recently a “reactive” campaign to observe such an atmosphere was held using the VLT. The bright spots in the Occator crater are composed of sodium carbonate. This is estimated to be the largest deposit of sodium carbonate outside of Earth. The crater Ernutet has ample deposits of prebiotic organic material that appears to have been produced in Ceres. The lumpy surface, including the 4-mile high mountain Ahuna Mons, is indicative of active cryovolcanism. Tectonically rich terrain, such as in the region of Nar Sulcus, tells of an active planet. The rich geological and geophysical potential of Ceres and its large inventory of water suggests that Ceres will be a major focus of future planetary exploration.
The IAU Commission C2: Communicating Astronomy with the Public - the first 3 years
Russo, Pedro
IAU Commission C2 is a think/do-tank that convenes the astronomy communication community and seeds initiatives to explore new ways to communicate astronomy with the public. The commission focuses on community initiatives and new trends and less on implementing projects, as that naturally falls more to IAU Office for Astronomy Outreach and Office of Astronomy for Development. This talk will provide an overview of the first 3 years of the new commission C2.
The IAU Commission C2: Communicating Astronomy with the Public - the first 3 years
Russo, Pedro
IAU Commission C2 is a think/do-tank that convenes the astronomy communication community and seeds initiatives to explore new ways to communicate astronomy with the public. The commission focuses on community initiatives and new trends and less on implementing projects, as that naturally falls more to IAU Office for Astronomy Outreach and Office of Astronomy for Development. This talk will provide an overview of the first 3 years of the new commission C2.
Non-Equilibrium Spectrum Formation affecting Solar Irradiance
RUTTEN, Robert
The theory of solar spectrum formation matured already during the1970s and remains the part of solar physics that is furthest advancedtowards full understanding. Nevertheless, its complexities affectingthe solar irradiance spectrum represent non-trivial or even horrendousobstacles to detailed modeling. For example, modeling of opticalirradiance requires detailed modeling of the ultraviolet, and thatrequires detailed treatment of the millions of spectral linesconstituting the line haze. In the ultraviolet the mechanisms bywhich uibquitous magnetic concentrations constituting network andplage, key irradiance factors, become bright points are not wellstudied yet.I will start with a tutorial overview of spectrum formation conditions(LTE => non-LTE => non-E) affecting solar continua and lines, and thenconcentrate on the complexities and difficulties of particularimportance to irradiance modeling.
A progress report of the Working Group High-Accuracy Stellar Spectroscopy
Ryabchikova, Tatiana
We present developments in laboratory astrophysics of importance to the field of high-accuracystellar spectroscopy that have occurred over the past triennium. These developments cover different aspects of laboratory and theoretical spectroscopy: atomic structure, atomic processes, and opacity calculations, relevant for various stellar types. The needs for these data for stellar spectroscopy in the era of large astrometric and spectroscopic surveys are emphasized. A short review of atomic and molecular line databases is given.
Atomic and Molecular Data Collections for Fine Spectral Analysis and Flux Calculations.
Ryabchikova, Tatiana
Spectral lines provide a substantial contribution to the total absorption of radiation emitted by stars. Therefore improvements to the line data are crucial for realistic reproduction of stellar irradiation._x000D_ We present a review of the latest experimental and theoretical atomic and molecular data, which are used for fine analysis of stellar and solar spectra as well as for irradiation/flux calculations. In particular, we focus on atomic data for the Fe-peak elements and on transition data for CN and CH molecules that are important for opacity calculations. _x000D_ We compare recent experimental transition probabilities of Fe I lines with the theoretical calculations based on extended set of energy levels and found no significant difference in absolute scales of both sets of values over the wavelength range of 2000 -- 10000 Å. Continuing work on the energy structure of the Iron atom by Peterson et al. (2017) has resulted in measuring and classifying more than 100 high-lying energy levels that helped to identify more than 1000 previously unknown spectral features in the solar and metal-deficient stellar spectra. The average uncertainty of the theoretical data is still as large as ±0.35 dex in logarithmic scale but we see continual and quick improvement in both quality and completeness of the data. We also emphasise the importance of the collisional data in irradiation calculations for the Sun and solar-like stars._x000D_ Finally, we present a short overview of the most important atomic and molecular databases.
A Simulation Study for Turbulence and Magnetic Fields in Galaxy Clusters
Ryu, Dongsu
Magnetic fields in galaxy clusters, at least in their outskirts, are conjectured to be originated by small-scale dynamo due to turbulence in the intracluster medium. Yet, the turbulence is not well understood, mostly because it differs from those in other astrophysical environments including the interstellar and interplanetary media in a number of aspects. For instance, the turbulence is induced in highly stratified backgrounds due to the cluster gravity, and also it is driven sporadically by major mergers which are the most energetic events during the hierarchical formation of clusters. To get quantitative measures for turbulence and magnetic fields, we performed a series of simulations using a newly developed, high-accurate MHD code, which followed the development of turbulence and the follow-up amplification of magnetic fields in galaxy clusters. In this talk, we present the results, aiming to address the following issues. Can the strength of the magnetic fields observed in the cluster outskirts, ~ 1 microG, be produced by turbulence dynamo during the cosmic history? Can the large-scale coherent magnetic fields observed in some radio relics, for instance, those over ~ Mpc or a larger scale in the so-called Sausage relic, be explained by turbulence dynamo alone.
The impact of UV radiation on the circumstellar chemistry
Saberi, Maryam
Penetration of ultraviolet (UV) radiation from the interstellar medium controls the chemistry in the outer part of the circumstellar envelope (CSE) around evolved stars. However, recent GALEX observations revealed 180 asymptotic giant branch (AGB) stars (57 % of the observed sample) have detectable Far- and/or Near-UV emissions, indicating the presence of extra UV radiation inside the CSE. The internal UV radiation can originate from stellar chromospheric activity, a hot binary companion, and/or the accretion of material between two stars in the binary systems.To constrain the effects of both internal and external UV radiation in the chemical modeling of CSEs, observations of main photodissociation/photoionization products are required. Moreover, comparison of isotopologue ratios of molecular species such as 12CO/13CO and H12CN/H13CN which dissociate through different mechanism can be used to trace the UV-chemistry. I will present our approach to studying the effect of UV-chemistry in the CSEs based on the ALMA and APEX observations and chemical modeling. I will also show the first CI detection towards the Mira AB system. Finally, I will discuss how this method can be used to indirectly detect unidentified hot binary companions of AGB stars.
Radio galaxy populations and their cosmic evolution
Sadler, Elaine
Large-area radio surveys, combined with wide-field imaging and spectroscopic surveys at optical and other wavelengths, have allowed us to build up a detailed picture of the different radio-galaxy populations in the local Universe and improve our understanding of how these populations evolve with cosmic time. I plan to review recent progress in this field, with a particular focus on the results from multi-wavelength radio surveys enabled by new telescopes and capabilities.
Identifying Distant Galaxy Clusters Using Dust-obscured galaxies as Signposts at Redshift > 1.3
Saha, Ripon
Recent studies of high-redshift galaxy clusters have revealed a high concentration of star formation and AGN activity in cluster cores at z >1.4. This suggests that dusty, highly star-forming and/or active high-redshift galaxies, such as Ultra-Luminous Infrared Galaxies (ULIRGs) or Dust-obscured galaxies (DOGs), might be employed to detect high redshift galaxy clusters. In order to test this proposition, we compared the distribution of ~2600 DOGs at z~2 with a sample of 50 distant (z >1.3) galaxy clusters from the IRAC Shallow Cluster Survey (ISCS). The sky surface density of DOGs in 0.5 arcmin radius apertures around the ISCS clusters is found to be 0.46 +- 0.12 arcmin^-2. This detection is overdense by a factor of 5.3+-1.4 relative to the surface density of randomly distributed objects (0.087 arcmin^-2), corresponding to a detection significance of 3-sigma. This result indicates that DOGs preferentially reside in rich environments, often within 250 kpc of a galaxy cluster. This physical association has motivated us to employ DOGs as signposts to detect new distant clusters. We developed and tested a pipeline to isolate and rank our detections, and using it have found 360 new cluster candidates (overdensities) above a 3-sigma detection significance. This pipeline has re-discovered 80% of all the ISCS clusters lying at z >=1.3, including IDCS J1426.5+3508 at z=1.75, the most massive galaxy cluster known at z > 1.5. To characterize the sample, we calculated the two-point angular autocorrelation function of the cluster candidates in order to measure their clustering strength. The correlation length is found to be ~18 Mpc/h, which demonstrates conclusively that the sample has the mass scale of galaxy clusters. We conclude that distant, highly star-forming galaxies selected in the mid- or far-IR with Spitzer or Herschel are sensitive signposts of massive cluster and protoclusters halos at the highest redshifts.
A network of faint DA White Dwarfs as Spectrophotometric Standards
Saha, Abhijit
DA white dwarfs with aurface temperatures higher than 20,000K are believed to have pure hydrogen radiative atmospheres, which are the least complicated to model. Spectroscopic analysis of their Balmer lines can be used to derive their surface temperature and gravity, which in turn predict the spectral energy distribution (SED) of the radiation emerging from their surface. Three such realtively bright stars, near enough to have no compliactions from interstellar reddening, are currently used as absolute flux calibrators for HST. I will describe an experiment undertaken with my colleagues which combines such spectroscopic characterization from the ground of two dozen fainter (V > 17) DA white dwarfs spread across the sky with panchromatic photometry obtained using HST (avoiding effects from the terrestrial atmosphere that have plagued past standardization work) to validate these model predictions. These fainter stars, which are at larger distances, are affected by interstellar reddening: the comparison of measured colors against model predictions must allow for this (by solving for it) within the constraints placed by the interstellar reddening law. We find sub-percent agreement of photometry with model predictions for ~90% of the objects. These objects, which were selected to be within the dynamic range of extant and future large area surveys are thus established as sub-percent SED standards. We are currently extending our calibartion to the southern skies. When completed, the distribution in the sky of this network of standards will be such that at any instance, from any site on Earth at least two of them are visible at airmass < 2.
Angular momentum transport in lopsided galaxies
Saha, KANAK
More than a third of spiral galaxies in the local universe are known to host large-scale lopsidedness. Such lopsided asymmetries are observed both in stars and gas, and are, in general, prominent in the outer parts of a galaxy. The role of such asymmetry in the dynamical evolution of a galaxy has been little explored so far. Following Lynden-Bell's approach, we compute the transport of angular momentum in the combined stars and gas disk embedded in a dark matter halo. It is shown that the lopsided asymmetry can participate in flowing angular momentum outwards provided it is leading in nature. We discuss how the angular momentum transport due to lopsidedness and spiral arms can facilitate inflow of gas from outside and thereby play an useful role in galaxy evolution.
Planetary nebulae, morphology and binarity, and the relevance to AGB stars
Sahai, Raghvendra
The dramatic transformation of the spherical outflows of AGB stars into the extreme aspherical geometries seen during the planetary nebula (PN) phase is widely believed to be linked to binarity and is likely driven by the associated production of fast jets and central disks/torii. The key to understanding the engines that produce these jets and the jet-shaping mechanisms lies in the study of objects in transition between the AGB and PN phases. In this talk, I first briefly summarize results from the imaging surveys of large samples of planetary and pre-planetary nebulae with HST. Almost all objects have bipolar, multipolar and elliptical morphologies, and there is widespread presence of point-symmetric structure. I present results from studies of individual objects that highlight observational techniques being used to (a) determine the ages and momenta of the jet outflows which can be used to constrain the properties of the jet engines, and to (b) provide evidence for binarity during the AGB phase._x000D_ Acknowledgements: The author's contribution to this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.
Detecting Isolated, Stellar-Mass Black Holes through Astrometric Microlensing
Sahu, Kailash
All stars with initial masses of larger than 20 solar mass are expected to end their lives as black holes (BHs). Theoretical studies suggest that there should be about 100 million stellar-mass BHs in the Galaxy. A large fraction of these BHs are expected to be single, either primordially or due to disruption of binaries by supernova (SN) explosions. Such isolated BHs are extremely difficult to detect directly, as they accrete from the ISM at very low rates, and thus they emit essentially no radiation. In fact, no isolated BH has ever been unambiguously found within our Galaxy. The only technique available to detect such isolated BHs is astrometric microlensing---the relativistic deflection of light from background stars. I will first discuss how astrometric microlensing provides a powerful tool not only to detect isolated stellar-mass black holes but also to determine their masses, distances and velocities. I will then discuss the first results from our two HST programs specifically aimed at the first detection of solitary BHs through astrometric microlensing.
Institutionalizing an astronomical internationalism in the long run: costs and benefits
Saint-Martin, Arnaud
A century of existence: it may seem short on the time-scale of the evolution of the universe, but very consequential to that of a scientific association. The fact that the IAU may be able to celebrate such a milestone is in itself a meritorious collective achievement, for it was not obvious at the very beginning that this organization was going to last more than a decade. Drawing on the historical sociology of scientific institutions, I will discuss in this presentation the mechanisms and processes (scientific, organizational, cultural and ideological) through which the IAU – and its dated but persistent form of scientific internationalism – has stabilized and maintained its identity since its creation in 1919, under the unifying auspices of a global epistemic object to be known: under one sky.
Ground-based astrometric project VERA : Overview, Science highlights and Synergy with Gaia
Sakai, Nobuyuki
Japanese VLBI array VERA has been conducting astrometric observations toward star-forming regions and late-type stars in the Milky Way (e.g. Honma et al. 2018 in press). As of August 2017, astrometric observations of about 200 maser sources were completed, and parallaxes were derived for 97 maser sources (75 star-forming regions and 22 late-type stars). In this talk, we briefly introduce overview and future prospect of VERA project as well as recent science results on several topics, which are (i) Fundamental parameters of the Milky Way (e.g. Honma et al. 2018), (ii) Galactic (spiral) structure and dynamics (e.g. Yamauchi et al. 2016), (iii) Star formation (e.g. Sakai et al. 2017) and (iV) Period-Luminosity relation of Mira variable (e.g. Nakagawa et al. 2016). Also, we discuss synergy between VERA (radio) and Gaia (optical) astrometric projects in the Gaia era.
Commission B5 Business Meeting
Salama, Farid
TBA
Plenary Session: The Future of Dwarf Galaxy Research: What simulations will predict
Sales, Laura
Dwarf galaxies are the most numerous type of galaxies in the Universe and largely fascinating objects in their own right. Believed to be the most dark matter dominated objects within the LCDM model, dwarf galaxies pose the most significant challenges to our cosmological scenario. The large variety of shapes, rotation curves and star formation histories observed in dwarfs seem at odds with the self-similarity expected from naive interpretations of the LCDM model. Feedback, star formation and reionization are believed responsible, to large extent, of some of these variations. Numerical simulations have started to resolve the relevant scales to address the fundamental physics of the inter-stellar medium behind dwarf galaxy formation. As such, simulations can now provide realistic predictions for observables with the potential of probing or rejecting our cosmological model. Some examples include the number density of faint galaxies, the inner dark matter content of dwarfs and their relative inefficiency to form stars. Future simulations will stride to reproduce the properties of dwarf galaxies in different environments, ranging from the field, to Local Group like environments, to massive galaxy clusters; with an eye kept on evolution across redshift. This wide census of properties, once compared to observations, will shed new light on our understanding of galaxy formation as well as on the necessity --or not-- to modify the nature of the dark matter to reproduce current and upcoming dwarf galaxy observations.
Gas and stellar metallicity gradients in face-on disk galaxies
Sanchez-Blazquez, Patricia
I will present an analysis of the metallicity gradients in a sample of 200 disk galaxies from the CALIFA survey. The metallicity gradient of both the stellar and the gas-phase component will be compared as well as their correlation with other parameters, like mass, morphological type, presence of bar, type of spiral arms and gas fraction. I will also present the correlations with both, the age and [Mg/Fe] gradients for the stellar components. This analysis allow us to conclude about the evolution of the metallicity gradients with time as well as the influence of axysymmetric features in producing radial migration.
Oxygen abundance profiles with MUSE: radial gradients and widespread deviations
Sánchez-Menguiano, Laura
In a recent publication (Sánchez-Menguiano et al. 2018, A&A, 609, A119) we characterised the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE for which a total of 14345 H II regions were detected. We developed a new methodology to automatically fit the abundance radial profiles, that are derived using the calibration proposed in Marino et al. 2013 for the O3N2 indicator. We find that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10), or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence in the case of the outer flattening. We find that the inner drop appears always around 0.5 re, while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope in the sample of aO/H = -0.10 ± 0.03 dex /re. This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale ("the abundance scale length", rO/H) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop (0.5 rO/H) and the outer flattening (1.5 rO/H). Finally, we find no significant dependence of the dispersion around the negative gradient with any property of the galaxies, with values compatible with the uncertainties associated with the derivation of the abundances.
Massive star atmospheres and donor star winds in HMXBs
Sander, Andreas
Understanding the complex behavior of High Mass X-ray binaries (HMXBs) is not possible without proper information about their donor stars. While crucial, this turns out to be a challenge on multiple fronts. First, multi-wavelength spectroscopy is vital. As such systems can be highly absorbed, this is often already hard to accomplish. Secondly, even if the spectroscopic data is available, the determination of reliable stellar parameters requires sophisticated model atmospheres that accurately describe the outermost layers and the wind of the donor star.For early-type donors, the stellar wind is radiatively driven and there is a smooth transition between the outermost layers of the star and the wind. The intricate non-LTE conditions in the winds of hot stars complicate the situation even further, as proper model atmospheres need to account for a multitude of physics to accurately provide stellar and wind parameters. The latter are especially crucial for the so-called ``wind-fed'' HXMBs, where the captured wind of the supergiant donor is essentially the only source for the material accreted by the compact object.In this review I will briefly address the different approaches for treating stellar winds in the analysis of HMXBs. The fundamentals of stellar atmosphere modeling will be discussed, also addressing the limitations of modern models. Examples from recent analysis results for particular HMXBs will be presented. Furthermore, the path for the next generation of stellar atmosphere models will be outlined, where models can not only be used for measurement purposes, but also to make predictions and provide a laboratory for theoretical conclusions. Stellar atmospheres will be a key tool in understanding HMXBs, e.g. by providing insights about the accretion of stellar winds onto the compact object, or by placing the studied systems in the correct evolutionary context in order to identify potential gravitational wave (GW) progenitors.
Report on CAP Conference Working Group Progress
Sandu, Oana
The CAP Conference Working Group of the IAU Commission C2 organises one of the largest gatherings focused on astronomy communication in the world. The conferences have been organised by C2 in partnership with local organisers, roughly every two years since 2005.Starting late 2015, a series of changes have been implemented with the goal to improve the experience of conference participants by:Focusing contributions on lessons learnt, as opposed to simply work reportsIncreasing the practical knowledge acquired during the conferenceIncreasing the quality of the contributionsMaking the conference more relevant to a diverse audienceIncreasing the number of participants from backgrounds such as press, scientists, graphic designers etc.Increasing networking opportunities.Another important goal of the two new co-chairs has been to increase the quality standards and transparency of the process of selecting a host and selecting abstracts. Finally, we looked at how to define the responsibilities of the Working Group members better, how to evaluate their performance and attract new members.In this talk, we will evaluate the achievement rate for the objectives set and present the measures we implemented towards these goals. We will also introduce our objectives going forward.
Report on CAP Conference Working Group Progress
Sandu, Oana
The CAP Conference Working Group of the IAU Commission C2 organises one of the largest gatherings focused on astronomy communication in the world. The conferences have been organised by C2 in partnership with local organisers, roughly every two years since 2005.Starting late 2015, a series of changes have been implemented with the goal to improve the experience of conference participants by:Focusing contributions on lessons learnt, as opposed to simply work reportsIncreasing the practical knowledge acquired during the conferenceIncreasing the quality of the contributionsMaking the conference more relevant to a diverse audienceIncreasing the number of participants from backgrounds such as press, scientists, graphic designers etc.Increasing networking opportunities.Another important goal of the two new co-chairs has been to increase the quality standards and transparency of the process of selecting a host and selecting abstracts. Finally, we looked at how to define the responsibilities of the Working Group members better, how to evaluate their performance and attract new members.In this talk, we will evaluate the achievement rate for the objectives set and present the measures we implemented towards these goals. We will also introduce our objectives going forward.
Conclusions from the Communicating Astronomy with the Public Conference 2018
Sandu, Oana
In a world permanently connected online, our society is also facing challenges that science never imagined could rise again. We find ourselves increasingly dealing with fake news, alternative facts and mistrust in science. In this post-factual era, achieving science literacy at large scale becomes imperative. The community of astronomy communicators stands in the front line of that endeavour.The theme of the 2018 Communicating Astronomy with the Public Conference — Communicating Astronomy in Today’s World: Purpose & Methods — is an invitation to reflect on our role in and our means of facing such challenges locally, nationally and as a global community.This talk will present the main conclusions from the conference, including the challenges identified by participants and their recommendations in facing them. The authors of this presentation, in their role as conference SOC co-chairs, would like to ensure that the inputs of astronomy communicators around the world are shared with IAU members interested in science communication.Another central point for the conference is the IAU’s 100th anniversary in 2019 — an exciting opportunity for the outreach community to once again come together, celebrate and set another milestone for the future of astronomy outreach and communication.This topic will also be reported on during the talk, with the hope that the outreach activities identified during CAP 2018 for the IAU anniversary can gain new supporters from IAU members.The CAP Conference is one of the largest gatherings focused on astronomy communication in the world. The conferences are organised by Commission C2 of the International Astronomical Union in partnership with local organisers, roughly every two years since 2005. The CAP 2018 conference is organised in cooperation with the National Astronomical Observatory of Japan and Fukuoka City.
The missing mass conundrum of post-common-envelope planetary nebulae
Santander-García, Miguel
Stars of 0.7 to 8 M$_\odot$ end their lives as planetary nebulae (PNe), by exposing their inert cores and ejecting their gaseous envelopes into the interstellar medium (ISM). Most PNe show beautiful, aspherical morphologies with high degrees of symmetry, despite their progenitor stars being essentially spherical. Angular momentum provided by a close binary companion has been widely invoked as the main shaping agent that would eject the nebula along preferred axes and planes: the engulfment of the companion by the Asymptotic Giant Branch (AGB) star into a common envelope (CE) would trigger a very brief phase (1-10 years) in which the orbit would shrink substantially due to drag forces, thus providing gravitational energy and angular momentum to eject this CE into a bipolar PN. The evolution of the AGB would be thus interrupted abruptly, its (still quite) massive envelope fully ejected to form the PN. In other words, PNe ejected through this process should be substantially more massive than those coming from single AGB stars, where most of that material was deployed into the ISM long ago, and is now too diluted to be detectable.Even though models succesfully predict the equator of these PNe to coincide with the orbital plane of the binary star —as occurs in every single case analysed so far—, they mostly fail on achieving escape velocities for the ejected material with the assumed angular momentum and gravitational energy reservoirs.We present observations of a pilot sample of confirmed post-CE PNe in the molecular regime, together with estimates of their total (atomic+molecular) mass content and linear momenta, in order to better understand their nature, and constrain models of formation. We find the nebular mass of our sample to be significantly lower than expected for an AGB envelope, leading us to wonder if models actually work for the actual masses involved, and also to raise some doubts on our understanding of the formation of these intriguing beasts.
Understanding the emergence of a plane of satellites around the Milky Way
Santos-Santos, Isabel
Most of the satellites of the Milky Way and Andromeda galaxies occupy a narrow, elongated region across the sky as if located on a plane. Recent studies have suggested similar alignments in other galactic systems beyond the Local Group, like CenA. In the case of the MW -for which reliable phase-space data is available-, the plane consists of the 11 brightest satellites, it is almost perpendicular to the MW’s disk, and ~6-8 out of 11 show coherent kinematics as if their orbits were contained within the plane.Such an extremely anisotropic distribution of satellites is rare to reproduce within DM-only cosmological simulations, despite the preferential accretion of substructures onto halos through the filaments of the cosmic web. Subsequent studies using high resolution hydrodynamical simulations of MW-type galaxies have shown that the inclusion of baryonic physics plays a crucial role, however the few studies on this issue have not been able to recover planes of satellites with as high significance and kinematical coherence as the one observed around the MW.We have explored this problem with a set of high-resolution zoom-in cosmological hydro-simulations of disc galaxies, run with different codes and subgrid-physics implementations. All of them present a clear non-random distribution of their satellites, which we follow as it evolves with cosmic time. By looking at the Aitoff projection of their orbital poles and through careful statistical analyses, we identify groups of satellites with coherent kinematics to which we fit planes of small minor-to-major axis ratio. We search for the physical processes driving the appearance and disruption of planes of satellites. A clue may reside in their merger/assembly history as well as in secular instability processes.
Mergers, Shocks, Radio Relics, and the Dynamical State of Clusters of Galaxies
Sarazin, Craig
Recent XMM-Newton, Chandra, and NuSTAR observations of merging clusters of galaxies will be presented. Cluster mergers drive shocks into the intracluster gas, and these shocks can (re)accelerate relativistic electrons, producing the observed radio relics. XMM observations of the merger shock in Abell 3667, which is associated with the NW radio relic, will be presented. The complex merger in Abell 2061 will also be discussed based on Chandra and XMM-Newton X-ray observations, and comparison to the radio relics and halos will be made. The origin of the radio relic in the poor cluster Abell S743 will be probed with the recent XMM, Chandra, and NuSTAR observations. The moderate redshift cluster ACT-CL J0256.5+0006 has a very low power radio halo, and may be an early stage merger. X-ray and SZ observations of high redshift clusters, including IDCS J1426.5+3508, will be described. The results on the thermal and non thermal physics of merger shocks will be given.
Magnetic Fields in Galaxies and Clusters of Galaxies in MHD Simulations
Sarazin, Craig
MHD simulations of magnetic fields in galaxies and clusters of galaxies, and their effect on the interstellar and intracluster gas will be discussed. Simulations of galaxies falling into clusters show that magnetic fields can drape galaxies, suppressing thermal conduction and hydrodynamical instabilities. These effects, particularly the reduction of thermal evaporation, allow elliptical galaxies to retain small coronae of hot gas, in agreement with X-ray observations. Without magnetic draping, these coronae would evaporate quickly. We consider simulations with a variety of magnetic field geometries, and with magnetic fields which are connected or disjoint between galaxies and the cluster. The field geometry affects the structure of tails, particularly for spiral galaxies; the MHD results are compared to the observations of “jelly fish” galaxies. Finally, simulations of the cumulative effect of magnetic fields and stripping in entire clusters and groups will be presented. These simulations include galaxies orbiting in equilibrium clusters, and galaxies which are initially bound to a pair of merging clusters.
Probing SMBH axis perturbations with low axial ratio radio galaxies
Saripalli, Lakshmi
Extended radio emission associated with AGNs has a variety of structures determined by the direction and stability in beam powers, as well as the ambient gaseous environment of the host galaxy. Radio galaxies with significant distortions and radio emission that is off the main axis exhibit low axial ratios. A significant subset of this class of low axial ratio radio galaxies may be caused by changing beam directions, which are signposts of perturbations to the super-massive black hole spin axis (SMBH; Saripalli and Roberts, 2018). _x000D_ _x000D_ I present a systematic study of an unbiased sample of radio galaxies with low axial ratios in a program aimed at (a) an empirical classification of the types of observed off-axis distortions, and (b) relating these to the types of distortions expected in interactions of beams with asymmetric gaseous environments, as well as in a variety of SMBH spin axis perturbations expected in different stages of galaxy mergers. The analysis leads to (c) derivation of occurrence rates for mergers and hence for nanoHertz GW backgrounds._x000D_ _x000D_ The work is based on recent EVLA imaging of a large sample of low axial ratio radio sources, which has unearthed a rich haul of S-, Z- and X-shaped radio galaxies as well as a significant number that show signatures such as inner S-spines, and those that show a pair of radio sources along different axes with a common radio core._x000D_ _x000D_ Our analysis of the large sample of 100 distorted radio galaxies points to a favored mechanism for the morphologies of the intriguing X-shaped radio galaxies that require both black-hole axis flip as well as synchrotron-plasma backflows into relic channels. The study has opened a promising route to pursue searches for binary SMBHs using large samples of low axial ratio radio galaxies, and hence to examine central engine astrophysics in extreme gravity regimes.
RadioAstron imaging of nearby radio galaxies
Savolainen, Tuomas
RadioAstron Nearby AGN Key Science Program uses the ultra high angular resolution provided by the space-VLBI mission RadioAstron to study the structure of the jets in nearby radio galaxies close to their formation site. Our space-VLBI images of 3C84 and M87 well resolve both jets in transverse direction, revealing structures that are not seen in the ground-based VLBI data. In 3C84, we are able to resolve the limb-brightened jet just 30 microarcseconds from the core in our 22GHz image, which allows us to measure the jet collimation profile from ~10^2 to ~10^4 gravitational radii from the black hole. We find a very broad, almost cylindrical structure extending all the way to the core. The bright outer layer has a transverse radius of 250 gravitational radii at only 350 gravitational radii (deprojected) from the core, which raises a possibility that the jet sheath originates in the accretion disk. Our 5GHz RadioAstron image of 3C84 shows a previously unseen low-intensity emission from a cocoon-like structure around the recently restarted, one parsec long, jet. The cocoon pressure may provide a natural explanation for the cylindrical jet profile seen in the 22GHz image. In the case of M87, we have obtained a high dynamic range image at 1.6GHz, which reveals a pattern of helical filaments inside the jet. The origin of this structure will be discussed.
Search for faint high redshift radio galaxies at low frequencies
Saxena, Aayush
High-redshift radio galaxies (HzRGs) are progentors of the most massive elliptical galaxies we see today. HzRGs are often foung in overdense regions in the early universe (in the centres of clusters and protoclusters) and are seen to be forming stars intensively. Their bright radio luminosities coupled with strong emission line strengths make them a unique beacon to study the most massive galaxies across the universe. At redshifts z>6, into the epoch of reionisation, radio galaxies can be used as unique probes to study the evolution of the neutral fraction of the intergalactic medium through the redshifted 21cm absorption signals in their spectra. Detection of even a single HzRG at z>6 could have profound implications for comoslogy. In this talk, I will present results from our search for faint HzRGs at 150 MHz from the TGSS ADR survey. Our sample probes a unique parameter space in flux density and spectral index. We have shortlisted 32 promising candidates from over 600000 sources and have followed them up at optical and infrared wavelengths (Saxena et al. 2018). We have confirmed redshifts in the range 1.5 < z < 5.7, which includes the discovery of the most distant radio selected galaxy known to date, with a Lyman alpha redshift of z=5.72 (Saxena et al. in prep). This object is by far the brightest radio source close to the epoch of reionisation and helps extend studies of HzRGs to never-seen-before redshifts. For a radio galaxy to exist at this epoch, its central SMBH must have been accreting very actively in the early universe. Discovery of the most distant radio galaxy from a preliminary sample is promising news for HzRG searches to probe the epoch of reionisation in unparalleled detail with next generation telescopes such as LOFAR, which is predicted to detect hundreds of radio galaxies at z>6 (Saxena et al. 2017).
A wide angle chemical survey of the Sagittarius Dwarf Spheroidal galaxy
Sbordone, Luca
The Sagittarius Dwarf Spheroidal galaxy (Sgr dSph) is the subject of the most evident tidal disruption event taking place in the Milky Way, and is the closest among dSph, greatly facilitating the detailed study of its stellar populations. For these reasons it has been considered an ideal testbench of both tidal merging events and dSph stellar populations. However, it quickly became evident that Sgr dSph was a rather exceptional object. Associated with a high number of globular clusters (the largest of which, M54, sits in its center), with an estimated pre-disruption total mass of various 10^9 solar masses, and hosting a chemically distictive, solar- to super-solar-metallicity population in its core, Sgr dSph most likely resembled an object like the Small Magellanic Cloud, before the tidal disruption by the Milky Way began._x000D_ We have collected high resolution spectra (from UVES@VLT, FLAMES@VLT, and MIKE@Magellan) for more than 300 stars across the Sgr dSph main body, associated globular clusters, and the Sagittarius stream. Detailed abundance for ~20 elements are available for about 150 stars, while for the rest metallicity and [alpha/Fe] ratios are available._x000D_ The detailed chemical picture of Sgr appears extremely interesting: the populations extend over 3 orders of magnitude in metallicity, with distinctive low [alpha/Fe] ratio in the metal rich component, high [Y/Ba] ratio extending to about [Fe/H]=-2, and a number of other peculiarities. The study also led to the discovery of a C-rich giant in the galaxy main body with extreme r- and s-porcess enancement, the first of its kind in Sgr dSph._x000D_ IMPORTANT: Please consider this abstract submission for a talk, since I missed the talk abstract submission deadline due to an illness. If this was not possible, a poster will do as well. Thanks a lot in advance. LS
Earth's paleo-magnetosphere and its implications on the evolution of the terrestrial atmosphere
Scherf, Manuel
The present-day terrestrial atmosphere is providing a habitable environment for a diverse range of life forms. However, simulations of the terrestrial paleo-magnetosphere as well as of the solar wind induced atmospheric ion-pickup escape ~4 Gyr ago are indicating that during the Hadean eon a nitrogen dominated atmosphere would not have been able to survive, but would have been eroded within a few Myr due to the strong EUV flux and solar wind of the early Sun. In addition, these results are suggesting that the present-day nitrogen-dominated atmosphere has its origin during later stages of the geological history, whereas for the late Hadean and early Archean, CO2 can be considered as the dominating atmospheric constituent. However, the 14N/15N disequilibrium between internal and surface reservoirs at the Earth is indicating that some atmospheric escape of nitrogen should have taken place in the past.Atmospheric escape is strongly coupled to the shape of the paleo-magnetosphere and to its interplay with the varying solar activity factors. Thus, we will present simulations of the terrestrial paleo-magnetosphere during the late Hadean and Archean eons and its influence on the evolution of the nitrogen atmosphere, including an estimation of N2 lost to space. Our results support the idea that the nitrogen dominated atmosphere started to build up during the Archean and evolved from a low-pressure atmosphere via outgassing of N2 into the present-day habitable environment. Important environmental conditions for this evolution will be discussed within this presentation. This also includes a potential solution for the before mentioned 14N/15N disequilibrium.Acknowledgement. The authors acknowledge the support of the FWF NFN project Pathways to “Habitability: From Disks to Active Stars, Planets and Life”, in particular its related sub-projects S11604-N16, S11606-N16 and S11607-N16. This is supported by the Austrian Science Fund (FWF) and the 550 US NSF (EAR1015269 to JAT).
Molecular Interstellar Medium in Nearby Galaxies as seen by ALMA
Schinnerer, Eva
ALMA has opened up a new window on the study of the interstellar medium (ISM) in nearby galaxies and in particular its molecular gas phase. Thanks to the order of magnitude improvement in sensitivity and angular resolution compared to previously existing facilities, it is now possible to obtain new insights on molecular outflows, the rich chemistry of the molecular gas reservoir, the molecular ISM structure (including that of Giant Molecular Clouds) and thus the impact of star formation processes onto molecular gas disk. I will highlight selected results from ALMA and provide a short outlook onto future ALMA capabilities relevant for molecular ISM studies of nearby galaxies.
Solar Irradiance for Climate Studies
Schmidt, Hauke
There is broad scientific consensus that at least the global warming observed since the 1950s is mainly anthropogenic. However, the contribution of natural forcings (of both solar and volcanic origin) to the evolution of global climate is still poorly quantified, and the uncertainty is considerably larger for periods further back in time. Moreover, regional influences of solar variability may be considerable even on the decadal time scale.In this presentation I will review how the representation of solar irradiance variability in climate models has evolved in the recent decades. Furthermore, I will summarize the current state of knowledge on influences of solar variability on climate, distinguishing in particular the so-called bottom-up and top-down mechanisms. While the further are caused by variability of total solar irradiance (TSI) acting at the Earth’s surface, the latter are caused by changes in solar spectral irradiance (SSI) acting mostly in the Earth’s middle atmosphere but are potentially communicated downward via changes in atmospheric chemistry and dynamics. I will point out how uncertainty in SSI influences the simulated atmospheric response and discuss which role limited understanding of processes in the Earth’s climate system plays for understanding solar-terrestrial effects.
Assessing an uncertainty of the Total Solar Irradiance composite
Schmutz, Werner
The TSI instrument PREMOS on the French satellite PICARD was operational from July 27, 2010 until March 4, 2014. Recently, we have re-evaluated the PREMOS data reduction and released version 2 of its TSI time series. The presentation will present the specific problems of PREMOS in establishing its long-term stability. Different solutions for assessing the sensitivity change of the two PREMOS TSI channels give an estimate of the uncertainty of the PREMOS long-term stability. This allows to compare PREMOS to the three other space radiometers PMO6/VIRGO and DIARAD/VIRGO on SOHO, ACRIM III on ACRIM-SAT, and TIM on SORCE, Combining the four different TSI time series allows to construct empirically a TSI composite over the almost four years when four instruments have been in operation simultaneously. Comparing the individual instruments time series to the composite then allows to get an estimate for each instrument's long-term stability and to extrapolate an uncertainty for the long-term stability over the instruments operational time. This extrapolation then gives an empirical estimate for the TSI composite from 1996 to today.
Observations of magnetic fields in Herbig Ae/Be stars
Schoeller, Markus
Models of magnetically driven accretion reproduce many observational properties of T Tauri stars. For the more massive Herbig Ae/Be stars, the corresponding picture has been questioned lately, in part driven by the fact that their magnetic fields are typically one order of magnitude weaker. Indeed, the search for magnetic fields in Herbig Ae/Be stars has been quite time consuming, with a detection rate of about 10%, also limited by the current potential to detect weak magnetic fields. Over the last two decades, magnetic fields were found in about twenty objects and for only two Herbig Ae/Be stars was the magnetic field geometry constrained. Also, several studies were undertaken to investigate the time dependence of spectroscopic tracers of magnetospheric accretion (MA). Overall, it seems that while there is proof that MA is present in some Herbig Ae stars, there is less evidence for the Herbig Be stars. In this review talk I will provide an overview about the current state of the MA research in Herbig Ae/Be stars and will give an outlook on what we might expect in the future.
A Search for X-ray Beacons in the Early Universe
Schwartz, Dan
We report on a Chandra "snapshot" survey of 14 radio quasars atredshifts z>3. These are selected to have one sided, arc-sec scalestructure, either a jet or lobe, and come from a complete, objectively-definedparent sample with radio flux density > 70 mJy in the FIRST survey, and with aspectroscopic redshift from the SSDS. Our objectives are to find X-ray emitting jets,compare the X-ray and radio morphology, and detect X-ray emissionarising from inverse Compton scattering of the cosmic microwave backgroundeven for those cases where the radio emission is no longer detectable.
High-resolution X-ray observations of 100 kpc Jets
Schwartz, Dan
Quasars with flat radio spectra and one-sided arc-second scale jets are found to have similar scale X-ray jets in about 60% of such objects, even in short 5 to 10 ks Chandra observations. Jet radio emission is synchrotron radiation, as known from its polarization. The X-ray emission is explained most simply, i.e. with the fewest additional parameters, as inverse Compton (iC) scattering of cosmic microwave background (cmb) photons by the relativistic electrons in the jet. With physics based assumptions, one can estimate enthalpy fluxes upwards of 10^46 erg per second, sufficient to reverse cooling flows in clusters of galaxies, and play a significant role in the feedback process which correlates the growth of black holes and their host galaxy bulges. On a quasar-by-quasar basis, we can show that the total energy to power these jets can be supplied by the rotational energy of black holes with spin parameters as low as a=0.3. For a few bright jets at redshifts less than 1, the Fermi gamma ray observatory shows upper limits below the fluxes predicted, calling the iC/cmb mechanism into question. At large redshifts, the cmb energy density is enhanced by a factor (1+z)^4, so that iC/cmb must be the dominant mechanism for relativistic jets unless their rest frame magnetic field strength is hundreds of micro-Gauss. A new Chandra survey for jets in radio quasars at z > 3 has revealed cases of X-ray jets and lobes extending beyond the detected radio emission.
Scope for Citizen Science and Public Outreach Projects in Developing World
Sekhar, Aswin
Citizen science projects are gaining momentum at a rapid pace in the western cultures. Direct involvement of citizens, students and amateurs can lead to the discovery of new exoplanet systems, asteroids, comets, meteor showers and so on. A key reason for this is the effective mechanisms pertaining to public outreach and science education in these scientifically advanced countries.As time progresses, it is important to widen such networks in such a way that big citizen science projects get the benefit trained volunteers from the developing and under privileged countries as well. The potential from these countries are immense because of the larger population, wider participation and the greater coverage of skies. For such networks to work effectively in the Asian sub-continent, we might need to further integrate efforts of IAU, IAU-OAD and local community groups who can synchronise and monitor these efforts in the long run.An extremely interesting and useful project which can enhance the excitement and learning of astronomy in young students from the developing and under priveleged countries will be remote observations using good telescopes. The main challenge is to find trained volunteers, local patrons and a stream lined system to make this happen. Some relevant points with regard to these aspects and future plans will be presented and discussed.
Polycyclic Aromatic Hydrocarbons in Protoplanetary Disks
Seok, Ji Yeon
Protoplanetary disks (PPDs) where planet formation takes place frequently emanate unidentified infrared emission (UIE) features in their infrared (IR) spectra. Major UIE features appear at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 µm, which are commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules. PAHs play crucial roles in the evolution of PPDs physically and chemically. Exposed to ultraviolet and visible photons from the central star, PAHs re-emit the absorbed photons through their vibrational relaxation, including the C-H stretching mode at 3.3 µm, C-C stretching at 6.2 and 7.7 µm, C-H in-plane bending at 8.6 µm, and C-H out-of-plane bending at 11.3 and 12.7 µm. The relative strength of the PAH emission bands prominently vary depending on the physical properties of PAHs such as their size (NC) and charge state (fion), which sensitively reflect the physical conditions of PPDs. We present model calculations to quantitatively interpret the PAH features observed in various PPDs, taking a wide range of both stellar properties (effective temperature and luminosity) and PAH properties (size, charge state, and radial distance from a central star) into account. The range of effective temperature considered is between 3,500 K and 30,000K, and PAH sizes are 16< NC < 4000. In particular, we generate grid diagrams of the 6.2 µm to 7.7 µm band ratio versus the 11.3 µm to 7.7 µm band ratio as a diagnostic tool, which allow us to directly compare observed PAH band ratios with the model calculations and to infer the PAH size and charge state as well as the local physical conditions where PAHs reside. We discuss applications to observational data and characteristics of PAHs in PPDs.
Statistical study on the kinematic classification of coronal mass ejections from 4 to 30 solar radii
Seonggyeong, Jeon
In this study, we perform a statistical investigation on the kinematic classification of 4264 coronal mass ejections (CMEs) from 1996 to 2015 observed by \textit{SOHO}/LASCO C3. Using the constant acceleration model, we classify these CMEs into three groups; deceleration, constant velocity, and acceleration motion. For this, we devise four different classification methods by acceleration, fractional speed variation, height contribution, and visual inspection. Our major results are as follows. First, the fractions of three groups depend on the method used. Second, about half of the events belong to the groups of acceleration and deceleration. Third, the fractions of three motion groups as a function of CME speed classified by the last three methods are consistent with one another. Fourth, according to the last three methods, the fraction of acceleration motion decreases as CME speed increases, while the fractions of other motions increase with speed. In addition, the acceleration motions are dominant in low speed CMEs whereas the constant velocity motions are dominant in high speed CMEs.
Modeling the environmental dependence of radio galaxy populations
Shabala, Stas
Feedback from AGN radio jets is held responsible for regulating star formation in the most massive galaxies over the last half of Hubble time. Observations of radio galaxy populations encode important information on feedback energetics and duty cycles, yet interpreting these observations is challenging due to the highly non-linear nature of the mapping between the observable and physical properties of radio jets.I will present a recently developed dynamical model, RAiSE (Turner & Shabala 2015, Turner et al. 2018a,b). A major departure from previous radio source models is in using galaxy clustering to describe environments into which the jets expand; this approach allows jet models to be easily integrated within a semi-analytic galaxy formation framework. The mapping between observables (such as radio luminosity) and physical parameters (such as AGN jet power and age) is strongly environment-dependent, and also evolves substantially over the AGN lifetime. I will describe the framework for inferring intrinsic jet parameters from broadband radio continuum and ancillary data, and quantifying selection effects against old low-surface brightness radio lobes such as those recently discovered with LOFAR and the MWA.
Standardization in the UV with Astrosat and its issues related to star cluster studies
Shah, Priya
The Ultra-Violet Imaging Telescope (UVIT) is one of the payloads in Astrosat, the first Indian Space Observatory. The UVIT instrument has two 375 mm telescopes: one for the far-ultraviolet (FUV) channel (1300–1800 °A), and the other for the near-ultraviolet (NUV) channel (2000–3000 °A) and the visible (VIS) channel (3200–5500 °A). In this paper, I shall discuss the issues with standardization in the UV with reference to Astrosat Observations (Cycle A04) made my me and a collaborator of young stars in the halo of the Milky Way. I shall discuss the problems faced in data-analysis and how these in turn lead to serious issues dealing with the color-magnitude diagarms, membership and age of the young embedded clusters I studied.
Kinematics and Dynamics of Young Star Clusters with TMT
Shah, Priya
Star clusters are evolving n-body systems . We discuss the early dynamics of star clusters, the process of primordial mass segregation and clustering observed in certain young clusters. We discuss how the dynamics coupled with stellar evolution of a cluster define the radial profile, mass function of and disruption the cluster and compare these parameters with some known clusters. As a member of the Thirty Meter Telescope (TMTD), International Science Driven Team (ISDT), I shall use these details to help define the science case, requirements and the expected precision in answering possible questions about the Evolution of Star Clusters in terms of astrometry and high resolution spectroscopy. I shall also report on some of the resolutions made at the recent TMT-Forum held in Mysore, India
Characterizing Free Floating Planet Candidates in the K2 Campaign 9 Microlensing Survey
Shan, Yutong
Properties of the free-floating planet (FFP) population across the galaxy shed critical insights to planet formation and dynamical evolution models. The occurrence rate and mass function of FFPs may help to constrain the importance of dynamical instabilities in these systems and ejection probability of planets, as well as any environmental dependence of these processes. Gravitational microlensing represents perhaps the only way to detect small planets without hosts across the galaxy. However, in general it is difficult to fully characterize individual microlensing systems, especially FFPs, from the ground alone. As a simultaneous and continuous second line of sight from space, K2 Campaign 9 (K2C9) provides the first opportunity to probe the properties of distant and isolated low-mass field objects. Jointly modelling data from ground-based surveys and K2C9, we characterize FFP candidates by measuring their microlensing parallaxes. Such a sample is the first step to constraining the mass function of this nearly invisible planet population, which could help refine our understanding of the physical processes associated with the formation and evolution of planets and planetary systems.
Report from B3 CP: Astroinformatics & Astrostatistics
Shastri, Prajval
TBA
Multi-epoch observations of the Blazar 1ES2344+514 using ASTROSAT, GMRT, Fermi and WEBT
Shastri, Prajval
1ES2344+514 is a blazar discovered by the Einstein Observatory and first found by the Whipple Observatory to have gamma-ray emission. It is known to be highly variable at all frequencies observed so far and on multiple time-scales, consistent with the expectation for blazars. The SEDs previously derived from the available sparse data have been shown to be broadly consistent with a synchrotron self-Compton model. During 2016 we observed 1ES2344+514 with the hard X-ray (LAXPC), soft X-ray (SXT) and ultraviolet (UVIT) telescopes on ASTROSAT at four epochs, and at radio wavelengths with the GMRT at one of these epochs with a cadence of about a month. We observed a brightening of the blazar at one of the epochs. We use these data and quasi-simultaneous WEBT observations to infer the Spectral Energy Distribution for the blazar.
Review of the Diffuse Soft X-ray Background
Shelton, Robin
Buried in the observed spectra of the diffuse Soft X-ray Background (SXRB) are spectral contributions from baryons in intergalactic space, the circumgalactic medium, our Galaxy's halo, hot bubbles in our Galaxy including the Local Bubble around us, the solar system, and even distant AGNs. In principle, if the various sources' contributions could be disentangled from each other, then the resulting measurements could then be used to determine the sources' physical properties. Many people, using a variety of clever observational techniques, have worked hard to do that. Meanwhile, others have created detailed simulations of many of these regions, pushing forward our understanding of how they behave and evolve. In this talk, I will review observations of the SXRB, efforts to dissect it and model it, and what we have learned about the material that makes the SXRB.
The Milky Way Bar and Bulge
Shen, Juntai
Our Milky Way is a barred spiral galaxy. I review the recent progresses on the properties of the Galactic bar and bulge, and the major theoretical models and techniques to understand the Milky Way bulge. Despite these recent advances, a complete bulge formation model that explains the full kinematics and metallicity distribution is still not fully understood. Upcoming large surveys are expected to shed new light on the formation history of the Galactic bar and bulge.
Wolf Rayet binaries in the Magellanic Clouds as progenitors of high mass X-ray binaries
Shenar, Tomer
Wolf-Rayet stars are evolved, hydrogen depleted stars that exhibit strong mass-loss. Non-degenerate Wolf-Rayet binaries are thought be progenitors of high mass X-ray binaries hosting a black hole. Understanding the origin and interaction physics of Wolf-Rayet binaries at different metallicities is therefore crucial for constraining the properties and incidence of high mass X-ray binaries. It is generally not known whether the majority of Wolf-Rayet stars in the Magellanic Clouds originate via stripping in binary systems or via intrinsic stripping due to mass-loss. We performed a complete spectral analysis of all known Wolf-Rayet binaries in the Small and Large Magellanic Clouds (SMC, LMC), as well as additional orbital analyses, and constrained the evolutionary histories of these important stars. In my talk, I will summarize our findings regarding the origin of Wolf-Rayet stars in the Magellanic Clouds and their feedback on their environments. I will further describe our study's implications on gravitational wave progenitors, high mass X-ray binaries, and the initial mass function as a function of metallicity.
Determining the Luminosity of the Third Dredge-up via S-type stars: the promise of Gaia
Shetye, Shreeya
S stars are late-type giants whose spectra show distinctive molecular bands with as most noticeable characteristic the appearance of ZrO bands. Their abundance patterns show signature of s-process nucleosynthesis, while the C/O ratio is intermediate between that of M-type giants and carbon stars. They can be segregated in two classes by probing their Tc content. The Tc-rich S stars are intrinsic S stars on the Asymptotic Giant Branch (AGB), producing the s-process elements internally which are then transported to the stellar surface via third dredge-up. The intrinsic S stars are the first ones on the AGB to have undergone a third dredge-up. Tc-poor S stars, in turn, are all members of binary systems which were enriched in carbon and s-process elements by the former AGB companion which is now a cold dim white dwarf.Getting a reliable Hertzsprung-Russell (HR) diagram for S-type stars is difficult not only because of their unconstrained distances but also because their complex atmosphere makes the determination of their stellar parameters challenging. We devised a spectral fitting method to disentangle the stellar parameters of S stars. The method makes use of MARCS model atmospheres for S-type stars covering a vast range in effective temperature(Teff), surface gravity, metallicity, [s/Fe], and C/O and comparing them with high-resolution, high S/N HERMES spectra. The accurate parallaxes from Gaia DR2 combined with the well-constrained Teff will provide the positions of the S stars on the evolutionary tracks in the HR diagram hence further constraining their masses and surface gravities.The parameter study along with the luminosity of intrinsic S stars will help us marking the onset of the third dredge-up in the HR diagram. The ultimate goal is to gain insight in the AGB nucleosynthesis and third dredge-up episodes in function of evolutionary mass and metallicity.
Superstrong B-fields of neutron stars in Be XRBs
Shi, ChangSheng
We re-estimate the surface magnetic fields of neutron stars (NSs) in Be X-ray binaries (BeXBs) with different_x000D_ models of torque. In particular, a new torque model is applied to three models of magnetosphere radius. Unlike the previous models, the new torque model does not lead to divergent results for any fastness parameter. The inferred surface magnetic fields of these NSs for the two compressed magnetosphere models are much higher than that for the uncompressed magnetosphere model. The estimated surface magnetic fields for NSs BeXBs in the Large Magellanic Cloud, the Small Magellanic Cloud and the Milk Way are between the quantum critical field and the maximum “virial” value by the spin equilibrium condition.
Molecular gas at extremely low metallicity
Shi, Yong
Extremely metal-poor galaxies with metallicity below 10% of the solar value in the local universe are the best analogues to investigating the interstellar medium at a quasi-primitive environment in the early universe. In spite of the ongoing formation of stars in these galaxies, the presence of molecular gas (which is known to provide the material reservoir for star formation in galaxies such as our Milky Way) and its physical properties remains unclear. With IRAM 30m, we have achieved CO detection in a galaxy at 7% Solar metallicity. Combined with archived infrared data, it is shown that the molecular gas mass per CO luminosity at extremely low metallicity is much larger than the Milky Way value. Our recent ALMA observation further reveals the spatial and kinematic properties of individual CO clumps in this galaxy. These observations help to advance the understanding of molecular ISM and star formation at very low metallicity.
Astronomy Translation Network (ATN)
Shibata, Yukiko
Language barriers act as constraints to share and access information, resources, activities, and experiences in astronomy outreach and education among educators, teachers, and amateurs around the world. To address this issue, and in direct alignment with the IAU Strategic Plan for the next decade, the IAU Office for Astronomy Outreach (OAO), the National Astronomical Observatory of Japan (NAOJ) and collaborators initiated a new project: the “Astronomy Translation Network.” The project aims to share resources for astronomy education and outreach in different languages by connecting volunteer translation efforts in a global network. As any pioneer - the project being the first to try to implement a sustainable large global network for translations in astronomy communication - the challenges faced are many. Here we discuss how to maintain the quality check on translations, provide worthy astronomy content, and motivate volunteers through the initial results of the project. We present how the network is now being planned and discuss the three main phases predicted; test of the workflow; development of the web platform; and improvement of functions, contents, and distributions.
Solar Science with ALMA
Shimojo, Masumi
The solar observations with millimeter and submillimeter ranges would have capabilities of revealing the temperature structures of the chromosphere and the non-thermal electrons accelerated in a solar flare. Nevertheless, the solar observing studies using the wavelength ranges was not so active, because it is difficult to obtain solar images with the high-spatial resolution that equals to the resolution with the other spectrum ranges._x000D_ The Atacama Large Millimeter/submillimeter Array (ALMA) broke through this situation. The ALMA observatory started to offer solar observations with 100 GHz (3 mm) and 239 GHz (1.25 mm) since Cycle 4 (Observing period: Oct. 2016 – Sep. 2017), and the demonstration data for solar observing, which are called the Science Verification (SV) data, were released in January 2017. The scientific results were achieved even from the SV data, and the solar observing data obtained in Cycle 4 will be opened to the community from July in order. In this talk, I present the scientific results obtained from the SV and Cycle 4 data, and introduce the development plan of new solar-observing functions with ALMA.
Recent LIGO results on Gravitational Waves
Shoemaker, David
The ground-based gravitational-wave detector network of LIGO and Virgo discovered a neutron-star binary inspiral and coalescence on 17 August 2017. This event, and a near-coincidence with a gamma ray signal from Fermi and Integral, stimulated a rapid and robust electromagnetic followup campaign which has led to rich results for astrophysics and astronomy. The properties of gravitational-wave source are inferred by matching the data with predicted waveforms based on general relativity. The gravitational-wave signal alone allowed a determination of the masses of the objects, the distance to the coalescing binary, a revised estimate of the rate of such signals, and information on the spins and tidal deformability of the neutron stars. With the associated gamma-ray burst, strong constraints are placed on the fundamental physics of gravity. Using existing redshift measurements of the host galaxy and the gravitational-wave measured distance, an independent determination of the Hubble constant is made. The source was rapidly localized to a region of 31 deg2 and the resulting sky map was issued to observing partners, allowing the identification of an electromagnetic counterpart; the consequences will be discussed in accompanying talks.
Sun, solstice and Makar Sankranti: an astronomical significance in our cultural practice
Shrestha, Pritisha
In many cultures around the world, Sun is revered as life giving component on earth. People of the past have therefore created various celebratory festivals to mark the importance of the star. And one of such festivals is Makar Sankranti, which is celebrated in the region of Indo-Gangetic Plain. Unlike other festivals, it follows a solar calendar.Predominantly performed by Hindus, the festival marks a transition or transmigration of the sun from Sagittarius to Capricorn zodiacal constellation. To be more specific, the festival takes place when we have winter solstice and the sun moves from the Tropic of Cancer to the Tropic of Capricorn. What it predominantly indicates is that the people of the past were not only very observant of the celestial events, but also commenced festivals around such cosmic occurring. Therefore, my paper would propose that by studying such festivities at various cultural settings would arm scientific researchers further with the indigenous and cultural knowledge of astronomy. Furthermore, by bridging the gap between ancient practice and new findings, such intangible cultural heritages could additionally be given scientific back up as well as new research areas could be traced back to the past knowledge. I would be presenting the very significance of the annual festival in relation to astronomy education and how the cultural practice has been celebrated since the time immemorial. The second portion of the paper would focus on how the festival follows a solar calendar instead of lunar and what it implies.
Energy equipartition between cosmic rays and magnetic fields
Shukurov, Anvar
The interpretation of synchrotron intensity data requires knowledge of the cosmic ray number density, which is often assumed to be in energy equipartition (or otherwise tightly correlated) with the magnetic field energy density. We examine the energy equipartition assumption between cosmic rays and magnetic fields using both: test--particle simulations (important to capture the effect of magnetic field structure) and MHD simulations by considering cosmic rays as an additional diffusive fluid (important to consider the effects of gas pressure). We find no spatial correlation between the cosmic rays and magnetic field energy densities at turbulent scales. Moreover, the cosmic ray number density and magnetic field strength are statistically independent. Nevertheless, small-scale cosmic ray structures are abundant at low energies. These are particles trapped in random magnetic bottles. These conclusions can significantly change the interpretation of synchrotron observations and thus our understanding of strength and structure of magnetic fields in Milkyway and nearby spiral galaxies.
The current status of the WSO-UV project. Facilities for testing and verification
Shustov, Boris
The World Space Observatory-Ultraviolet (WSO-UV) is a space observatory that will work in the ultraviolet range (115-315 nm) with an extension to the optical range for wide field imaging. The observatory is under construction having as intended launch date late 2023. The current status of the project and the facilities and technologies being developed for the instruments development, assembly and verification will be described in this talk.
Investigating High Mass X-ray Binaries at hard X-rays with INTEGRAL
Sidoli, Lara
The INTEGRAL archive developed at INAF-IASF Milano with the available public observations from 2003 to 2016 is investigated to extract the hard X-ray properties of about 60 High Mass X-ray Binaries (HMXBs). This sample consists of both persistent and transient sources, hosting either a Be star (Be/XRBs) or an early-type supergiant companion (SgHMXBs), including the most extreme systems, the Supergiant Fast X-ray Transients. INTEGRAL X-ray light curves (18-50 keV), sampled at a bin time of about 2 ks, are used to build the cumulative distributions of their hard X-ray luminosities, their duty cycles (defined as the percentage of detections at this same bin time), the range of variability of their hard X-ray luminosities. Putting the phenomenology observed with INTEGRAL into context with other known source properties (e.g. orbital parameters, pulsar spin periods), together with observational contraints coming from softer X-rays (below 10 keV), allowed us to investigate how the different HMXB sub-classes behave (and sometimes overlap). We will present the results of this research, aimed at comparing HMXB subclasses (Be/XRBs, SgHMXBs and SFXTs) and investigating how intermediate systems that link them.
NLTE abundances of C, O, Ca, Ti, and Fe in BAF-type stars
Sitnova, Tatyana
A knowledge of accurate chemical abundances of BAF-type stars is important for understanding stellar physics and the galactic matter at modern epoch. We treat accurate methods of abundance determination based on the non-local thermodynamic equilibrium (NLTE) line formation for five chemical elements, namely carbon, oxygen, calcium, titanium, and iron. We apply comprehensive model atoms of C I-II, O I, Ca I-II, Ti I-II, and Fe I-II described in our previous studies. It is worth noting that we are the first who have performed the NLTE calculations with comprehensive model atoms for Ca I-II, Ti I-II, and Fe I-II in the Teff range from 7000 K to 13000 K. We determine the NLTE abundances of C, O, Ca, Ti, and Fe in ten BAF-type stars with well determined atmospheric parameters using high-resolution and high signal-to-noise ratio spectral observations in wide wavelength range, from UV to IR. We show that, for each chemical species in each star, NLTE leads to consistent abundances from different lines. Our NLTE methods well reproduce emission lines of C I, Ca II, and Fe II detected in the near IR spectrum of late B type subgiant star HD160762, using classical plane-parallel model atmosphere. In BAF-type stars, all the investigated elements except O are observed in lines of the two ionisation stages, providing an opportunity to determine atmospheric parameters from the ionisation equilibrium method. We perform the NLTE calculations for these elements and provide departure coefficients for atomic levels in a grid of model atmospheres with 7000 K < Teff < 13000 K, 3.2 < log g < 5.0, -0.5 < [Fe/H] < 0.5. The grid of departure coefficients was implemented in the SME code for automatic determination of atmospheric parameters and abundances.
SiO masers in thousands of AGB stars in the Galaxy
Sjouwerman, Lorant
We report on the Bulge asymmetries and Dynamic Evolution (BAaDE) survey which has observed 19,000 MSX color selected red giant stars for SiO maser emission at 43 GHz with the VLA and is in the process of observing 9,000 of these stars with ALMA at 86 GHz in the southern sky. Our setup covers the main maser transitions as well as those of isotopologues and selected carbon lines. Observations of this set of lines allows a far-reaching catalog of line-of-sight velocities in the dust-obscured regions where optical surveys cannot reach. Our preliminary detection rate is close to 70%, predicting a wealth of new information on the distribution of metal rich and carbon rich stars, their kinematics as function of location in the Galaxy, as well as the occurrence of lines and line ratios between the different transitions in combination with the spectral energy distribution from about 1 to 100 micron. Similar to the OH/IR stars, a clear kinematic signature between disk and bulge stars can be seen. Furthermore, the J=1-0 (v=3) line plays a prominent role in the derived maser properties, indicating diverse and/or variable pumping conditions. We further present a possibility to separate carbon-rich from oxygen-rich AGB stars using MSX colors.
Galaxy mergers in intermediate redshift clusters
Skelton, Rosalind
In the hierarchical model of galaxy formation, structures build up over time through the merging of smaller subunits. Mergers play an important part in the growth of galaxies and interactions between galaxies affect the level of star formation, with the potential to both enhance and reduce it. In today's massive clusters, mergers are thought to occur rarely, yet they often host massive early-types that are likely to have built up through dry mergers at earlier times. In this work we measure the close pair fraction in clusters at intermediate redshifts (z~0.5) using deep data from the Hubble Frontier Fields. We examine the distribution and properties of close pairs, and the evolution of the merger rate in clusters, considering not only the brightest cluster galaxy but the broader cluster environment.
The End: Watching the Death of Extreme Carbon Stars in the Large Magellanic Cloud
Sloan, G.C.
Extremely Red Objects (EROs) are highly evolved carbon stars embedded deeply in their own dust. Several were discovered in the Large Magellanic Cloud by the Spitzer Space Telescope. We appear to have caught them in the moment of transition off of the asymptotic giant branch. Multi-epoch observations from Spitzer and the Wide-field Infrared Survey Explorer (WISE) reveal weak variability, in contrast to the trend of increasing pulsation amplitudes with more dust as seen in most carbon stars. The photometric data also reveal excess blue emission at shorter wavelengths, which would be expected as the stellar envelope detaches from the remnant core and the dust shell moves outward and begins to deviate from spherical symmetry. In this scenario, the blue excess could arise from light scattered from regions in the extended dust shell with more direct lines of sight to the central star. These objects give us the chance to study, in detail, how a star begins evolving into a planetary nebula. We have begun a campaign to look more closely. Initial results with adaptive-optics imaging of the dustiest ERO confirm the expected asymmetry at sub-arcsecond scales.
Are large main belt asteroid families homogeneus?
Slyusarev, Ivan
Asteroid families were formed during collisional disruptions and their physical properties provide unique information about internal material of the parent bodies. We have performed an analysis of the homogeneity of physical properties of 56 large main belt asteroid families from Nesvorny database. Using data on albedo (p) and color index (a*) from WISE and SDSS databases we found out, that all points on “color (a*) - albedo (p)” plots for all families can be separated in to three subgroups: I (p<0.1; a*<-0.05); II (0.1<p<0.25; a*<0.05)="" and="" iii="" (p="">0.15; a*>0.05). The dark subgroup I and high albedo subgroup III are presented in all bimodal families with some exceptions. Only two families include all three subgroups. Analysis of possible taxonomic interpretation of these three subgroups gives a clear result only for subgroup III which is linked to the S-type asteroids. Subgroup I is a mixture of dark asteroids that belong to F, C, P, D types. Subgroup II may be consistent with the M-type asteroids. Analyzed families are divided into homogeneous: (27 families); bimodal (13 families); and trimodal families (2 families Vesta and Flora). Families Aeolia, Xizang, Aeria and 15477 have not show bimodality in color and albedo distribution, but they contain asteroids that are intermediate between low (I) and middle-albedo (II) subgroups. All these families are located very near 2.7 au. We have analysed the distribution of proper elements for subgroups and V-shape plots for each bimodal family and found that several families consists of two overlapping families as in the case of Nisa-Polyana. Our analysis have shown that the significant fraction (25%) of the considered families are inhomogeneous in terms of albedos and colours. A fraction of the dark subgroup (I) in bimodal families is not negligible (10-30%).</p<0.25;></p>
Photometric Calibration of the Dark Energy Survey
Smith, J. Allyn
The Dark Energy Survey (DES) is a 5000 sq deg grizY imaging survey of the Southern Galactic Cap being conducted with the 570-megapixel Dark Energy Camera (DECam) on the Blanco 4-m telescope at Cerro Tololo Interamerican Observatory (CTIO). In January of this year, DES publicly released its first 3 years of coadd data, and, in February, it completed its fifth and final full observing season of on-sky operations. By the end of the processing campaign for the first year data set, DES had already achieved better than 2% photometric calibrations over the survey area. By the end of the processing campaign of the first three years of data, DES had achieved sub-percent photometric calibrations over the full DES footprint, with the promise of better than 0.5% photometry for the full 5-year data set. Here, we discuss the survey strategy, the ancillary calibration hardware, and the software that allowed us to achieve this calibration performance.
New Perspectives on Classical Pulsators
Smolec, Radoslaw
In recent years, we have witnessed many discoveries related to classical pulsators, Cepheids and RR Lyrae (RRL) stars, accompanied with progress in our understanding of these invaluable astrophysical tools. These discoveries are possible not only thanks to the precise observations of space missions, but also thanks to long-lasting regular monitoring of tens of thousands of classical pulsators by ground-based surveys. I will present the recent discoveries done by Warsaw group using the data of the OGLE project. Five new groups of double-periodic RRL stars were recently discovered. These include not only radial mode pulsators, such as anomalous RRd stars, but also three groups in which non-radial pulsation is excited. For one of them, identification of additional periodicities with non-radial modes of moderate degrees will allow for asteroseismic inferences. Still, the mode content and mechanism behind multiperiodic pulsation remains puzzling in most of the new groups. Analysis of classical Cepheids photometry in search for additional modes is ongoing. I will present detailed analysis of first overtone Cepheids with moderate degree non-radial modes that form three sequences in the Petersen diagram, as well as of stars with close non-radial modes. Finally, quasi-periodic modulation of pulsation, so-called Blazhko effect, was discovered in all types of classical pulsators. Modulations are a common feature of fundamental mode RRL stars. They are also common in some of the new groups of double-periodic variables. I will focus however on a periodic modulation of pulsation in Cepheids, which is a new phenomenon. A numerous sample of modulated stars was found among fundamental mode classical Cepheids, the most useful standard candles. Modulation was also discovered for the first time in tens of type-II Cepheids. These modulations are most likely of resonant origin. No doubt classical pulsators are much more complex and puzzling stars than just a few years ago.
Calibration techniques for solar spectral irradiance (SSI) instruments
Snow, Martin
The Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado has a long history of making solar spectral irradiance (SSI) observations from space. We have flown spectrometers that measure the ultraviolet wavelength range starting with the Solar Mesosphere Explorer, launched in 1981. UV observations continued with the Solar-Stellar Irradiance Comparison Experiments on the Upper Atmosphere Research Satellite (1991-2005) and Solar Radiation and Climate Experiment (2003-present). LASP has also built the Extreme Ultraviolet and X-ray Irradiance Sensors instruments on the GOES-R series (2017-present). We began making observations in the visible and infra-red with the Solar Irradiance Monitor on SORCE (2003-present) and continue this data record with the Total and Spectral Irradiance Sensor (2017-present). CubeSat sized compact versions of both the SIM and SOLSTICE instruments have been developed and calibrated and await launches in 2018.All of these instruments undergo extensive ground calibration using SI-traceable standards. In the case of the UV instruments, we make extensive use of the Synchrotron Ultraviolet Radiation Facility at the National Institutes of Standards and Technology. For longer wavelengths, we have developed calibration facilities at LASP using NIST Spectral Irradiance and Radiance responsivity Calibration using Uniform Sources (SIRCUS) lasers and cryogenic radiometer. This talk will describe the calibration techniques that we use and the absolute uncertainties that we have achieved with each instrument and facility.
The SORCE Solar Spectral Irradiance Record: Fifteen Years of SSI
Snow, Martin
The Solar Radiation and Climate Experiment (SORCE) has measured solar spectral irradiance (SSI) from the ultraviolet through the infra-red on a daily basis for more than a solar cycle. This fifteen year record includes the decline of solar cycle 23 and the entirety of solar cycle 24. We will present the measurements from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and the Solar Irradiance Monitor (SIM) along with uncertainties in both absolute calibration and uncertainties in on-orbit degradation tracking. These observations will also be compared with irradiance models as well as observations from overlapping missions such as UARS/SUSIM, AURA/OMI and ISS/SOLSPEC. Initial results from the next generation of SSI instruments, TSIS-1/SIM and the compact SOLSTICE, will also be shown. Finally, an overview of the future of SSI measurements from space will be described.
Compact Symmetric Objects: the key to understanding the initial stages of a radio source expansion
Sobolewska, Malgosia
Relativistic outflows from AGN propagate out to hundreds of kpc distances from the origin and impact environment on many scales, and thus influence evolution of structures in the universe. Compact extragalactic radio sources provide important insights into the initial stages of a radio source evolution and probe states of black hole activity at the time of the formation of a relativistic outflow. These compact sources show radio features typically observed in large-scale radio galaxies (jets, lobes, hot spots), but contained within the central 1 kpc region of the host galaxy. Compact Symmetric Objects (CSOs, a subclass of GigaHertz Peaked spectrum radio sources) are not affected by beaming and their linear radio size can be translated into a source age if one measures the expansion velocity of the radio structures. Such ages have been measured for a small sample of CSOs. Using the Chandra X-ray Observatory, XMM-Newton and NuSTAR we observed a pilot sample of 16 CSOs in X-rays (6 for the first time). Our results show heterogeneous nature of the CSOs X-ray emission indicating a range of AGN luminosities and complex environments. In particular, we identified four X-ray sources obscured with a dense medium (equivalent column > 1023 cm-2) capable of disturbing/slowing down the jet and confining the jet to a small region. Thus, for the first time we gain the observational evidence in X-ray domain in favor of the hypothesis that in a sub-population of CSOs the radio jets may be confined by the dense X-ray obscuring medium. As a consequence, the kinematic ages of these CSOs may be underestimated. We discuss the implications of our results on the emission models of CSOs, the earliest stages of the radio source evolution, jet interactions with the ISM, diversity of the environments in which the jets expand, and jet-galaxy co-evolution.
Small-scale dynamo as a mechanizm for excitation of extragalactic magnetic fields
Sokoloff, Dmitry
There are observational confirmation for existence of substantial magnetic fields in extragalactic medium including cosmological voids. Origin of such cosmological magnetic fields is a topic of intensive discussions. A viewpoint presented in this talk is that the extragalactic magnetic fields can be excited by a dynamo mechanizm. The point is however that this mechanizm hardly can be a conventional mean-field dynamo based on a joint action of rotation and mirror-asymmetric turbulence. Indeed, extragalactic medium hardly have a substantial rotation. There is however another kind of dynamo known as small-scale or turbulent dynamo/ This mechanism do not requires any rotation or mirror-asymmetry. The only what is required for small-scale dynamo action is a moderate conductivity and turbulence. We present estimations for expected magnetic field strengthes and spatial scales of magnetic fields excited by cosmological small-scale dynamo and compare the predictions with that one for magnetic fields excited by phase transitions in the Early Universe.
Science from Solar Orbiter
Solanki, Sami
The Solar Orbiter is the next solar physics mission of the European Space Agency, ESA, in collaboration with NASA, with a launch planned in 2020. The spacecraft is designed to approach the Sun to within 0.28 AU at perihelion of a highly eccentric orbit. At a later phase in the mission, the spacecraft will leave the ecliptic and study the enigmatic poles of the Sun from a heliographic latitude of up to 34 degrees.Equipped with 6 remote-sensing and 4 in-situ instruments, Solar Orbiter will address the overarching question on how the Sun forms and influences the heliosphere. It will therefore, probe the coupling between the Sun and the inner heliosphere. The proximity to the Sun at the closest perihelia will also allow the Sun to be observed at uniformly high resolution at EUV and visible wavelengths. Such observations are central for learning more about the magnetic coupling of the solar atmosphere. Furthermore, Solar Orbiter will provide the first ever optical and EUV observations of the solar poles, including the magnetic field there, which plays an important role in the workings of the solar dynamo.
Magnetic Features as Drivers of Solar Brightness Variability
Solanki, Sami
Many sources have been proposed for the variable solar Irradiance. Over the years there have been increasing hints that the main cause of irradiance variability at solar rotation and solar cycle timescales is the magnetic features at the solar surface, while at shorter timescales other sources, such as convection are likely to become important as well. However, no final answer could be provided, given the empirical nature of the models of solar irradiance variations. Recently, the use of state-of-the-art 3D MHD simulations incorporating as much physics as possible, to reconstruct solar irradiance variations has introduced a new rigour and has finally provided unambiguous answers for these long-standing questions.
Review on Observations of magnetic fields in star-forming clouds
Soler, Juan Diego
This review examines observations of magnetic fields in molecular clouds, that is, at spatial scales ranging from tens to tenths of parsecs and densities up to hundreds of particles per cubic centimetre. I will briefly summarize the techniques for observing and mapping magnetic fields in molecular clouds. I will review important examples of observational studies using each technique and its implications for our understanding of the role of the magnetic field in the molecular cloud formation and evolution. Finally, I will briefly discuss the prospects for advances in our observational capabilities with telescopes and instruments now beginning operation or under construction.
On the relationship between galaxy and halo size and spin
somerville, rachel
There is a long-standing ansatz that the angular momentum, and therefore the radial size, of galaxies is set by the spin of the host dark matter halo, and this ansatz forms the basis of galaxy size predictions in most semi-analytic models. I will present results from “structural abundance matching”, in which we empirically constrained the average relationship between galaxy size and halo virial radius from z~0 to z~3, using observations from the GAMA and CANDELS surveys. We found that this relationship exhibits a significant mass and redshift dependence, which suggests that halo spin is not the driving factor. I will discuss follow-up studies in which we explore the correlation between galaxy size and spin and halo properties in cosmological numerical hydrodynamical simulations from several groups (NIHAO, VELA, and Illustris) in order to gain insights into the physical origin of galaxy size and spin.
An eclipsing Wolf-Rayet ULX in the Circinus galaxy
Soria, Roberto
Ultraluminous X-ray sources with a Wolf-Rayet donor star are the most likely progenitors for LIGO merger events. They are accreting at a super-Eddington rate for ~1e5 yr, likely via Roche lobe overflow; after core collapse of the donor star, the system can turn into a double black hole binary with an initial orbital period of a few hours. By contrast, HMXBs with a supergiant or main sequence donor can also produce black hole-black hole binaries, but with binary separations that are too large for inspiral and merger within a Hubble time. Only a handful of ultraluminous Wolf-Rayet HMXBs have been identified so far. We will present the X-ray spectral and timing properties of the best-known example, located in the Circinus Galaxy. Its intriguing dipping and eclipse behaviour is different from the type of orbital modulations seen in other classes of HMXBs. We argue that such lightcurves are a defining property of this class of super-Eddington HMXBs, in which both the primary and the secondary launch dense, fast outflows with similar kinetic power. We suggest that the occulting material is dense shocked gas between black hole and donor star, and in a bow shock ahead of the black hole.
Gas-rich Dwarfs as Ultra-diffuse Galaxy Progenitors: Constraining Formation Models with Deep HI Observations
Spekkens, Kristine
We constrain formation models for ultra-diffuse galaxies (UDGs) in dense environments -- red systems with stellar masses akin to dwarf galaxies but effective radii comparable to that of the Milky Way -- using deep HI observations of candidate progenitors in the field. Given their faintness in the optical, distance and dynamical mass measurements for UDGs remain scarce; nonetheless, the available data suggest that many are low surface brightness dwarfs. How are UDGs related to gas-rich field dwarfs, and what are their evolutionary histories? Numerical simulations offer two distinct possibilities: UDGs may stem from the high-spin tail of the dark matter halo distribution, or their large effective radii may arise from gas outflows during past star formation episodes. These scenarios imply different physical properties for UDG progenitors in the field, which we constrain by characterizing their HI reservoirs. We have detected HI in five blue UDGs around Hickson Compact Groups using the GBT, finding low-mass objects with high-spin halos and gas richnesses that correlate with their effective radii. In this contribution, we will confront predictions from UDG formation models with these observations to test the hypothesis that gas-rich dwarfs are UDG progenitors. We will also report on our on-going campaign to follow up dozens of field UDG candidates from DESI pre-imaging data in the Coma cluster outskirts in HI with the GBT, yielding the first measurements of their gas content as a function of environment, colour, surface brightness and dynamical mass.
Astronomy and host communities - considerations of science, culture, environment and relationships with host communities
Squires, Gordon
For modern astronomy projects, we need to think expansively about the permeable boundaries of host communities given our networked world, and refresh traditional thinking about relationships with the host communities for our projects. In this presentation, we discuss the implications and strong desires for people to be connected to a “community” and whether there are opportunities for astronomy in this regard. We also consider the implications of astronomy facilities co-existing in special locations for host communities (often mountains) and the implications when culture and sensitive environmental ecosystems intersect with astronomy. We also touch on how trust in science may be effecting our work. To frame this discussion, we draw on our experiences with the TMT International Observatory. For the past 10 years we have been developing relationships in Hawaii Island, and more recently in La Palma - possible locations for installation of the telescope. A review of some of our efforts provides insights and direction on how to merge the diverse goals.
The population of planetary nebulae in the Galaxy and in nearby galaxies
Stanghellini, Letizia
Planetary nebulae (PNe) are the gaseous remnant of AGB stars, and they carry memory of their progenitor's history. In this review we focus on the population of Galactic and extragalactic PNe as probes of galactic evolution. We will discuss (i) PN populations across galaxy types; (ii) how to date PN progenitors; (iii) clues on the Galactic structure, based on PN probes; and (iv) radial metallicity gradients from Galactic and extragalactic PNe.
A Planetary Mass Companion in an Edge-on Protoplanetary Disk System
Stapelfeldt, Karl
A small number of candidate planetary mass companions (PMCs) have been detected to young stars, at least one showing evidence of ongoing accretion. While ALMA has the sensitivity to detect circumplanetary disks around these objects, none have been detected around a bona-fide PMC. We report ALMA's detection of unresolved millimeter continuum emission from the planetary mass companion SSTc2dJ162221.0-230402 b. Discovered in HST optical images, this companion appears projected at the outer radius of an edge-on protoplanetary disk and aligned in the disk plane. Keck AO photometry shows that the companion has a comparable temperature to the brown dwarf GQ Lupi B but with 10x less luminosity - consistent with a planetary mass object. Keck AO spectroscopy detects weak 2.12 micron H2 emission from the companion. We will report on the full ALMA dataset, plus deep HST imaging and HST grism spectroscopy that are expected to be taken this spring. SSTc2dJ162221.0-230402 appears to be an accreting protoplanet and circumplanetary disk seen at 110 AU projected separation, and thus offers support to models of planet formation by gravitational instability.
About planets around the pulsars B0329+54 and B0525+21
Starovoit, Elena
At the moment, several thousands exoplanets are known and pulsar planets are one of the rarest types of exoplanets. Our study is devoted to the investigation of two prospective owners of the planetary system: these are PSR B0329+54 and PSR B0525+21._x000D_ For research of the pulsar B0329+54 we used the measurements obtained during 1968–2012 at the Pushchino Radio Astronomy Observatory (at 102 and 111 MHz), the Jet Propulsion Laboratory (2388 MHz) and the Kalyazin Radio Astronomy Observatory (610 MHz). For study of the PSR B0525+21 we used the data obtained at the Jet Propulsion Laboratory (2388 MHz) and the Jodrell Bank Observatory (408, 610, 910, 1410, 1630 MHz). The span of the pulsar's B0525+21 measurements cover 36 years._x000D_ The barycentric post-fit timing residuals of the pulsars B0329+54 and B0525+21 have harmonic variations which can be explained by the presence of planets orbiting these pulsars. The motion models and parameters of the proposed pulsar planets have been determined._x000D_ The planet of the PSR B0329+54 has orbital period P1 = 27.8 yr, orbital semi-major axis a1 = 10.26 AU, eccentricity e1 = 0.23, and mass m1sini = 2M⊕. In addition, there are short-period variations in the timing residuals of that pulsar, but the existence of the second planet of the PSR B0329+54 predicted by previous researchers with the period about 3 yrs has not been confirmed._x000D_ The planet of the pulsar B0525+21 has orbital period P2 = 20.2 yr, orbital semi-major axis a2 = 8.4 AU, eccentricity e2 = 0.96, and mass m2sini = 0.5M⊕. Additionally, the precession of the planet's line of apses has been measured, and it is dφ = -0.77 rad/period. A high eccentricity may indicate that this planet has survived a supernova explosion.
IAU - A century of science and spirituality around the world
Stavinschi, Magda
Man has always been fascinated by the sky. He tried to interpret both periodic and unexpected phenomena. They came to be linked to divinity (through religion) or with his destiny on earth (through astrology). For centuries, the contrast between reality and appearance has sparkedconflicts. The most famous involved the Catholic Church. e.g. Galileo's trial and the death of Giordano Bruno, considered a "martyr of science". Other churches, including the Orthodox, seemed less interested in the topic. However, even prominent Orthodox hierarchs weredirectly involved in astronomical research: Hrisant Notara, a colleague of Cassini I at Paris Observatory, eventually became Patriarch of Jerusalem._x000D_ The accelerated globalization of the last decades, thanks to the Internet, as well as the success of space missions, forced Astronomy to get more involved in the dialogue between science and spirituality. Hot topics such as the birth of the Universe, the interpretation of Genesis, extraterrestrial life, astrology, are now preventing Astronomy from staying passive in the debate; it has to leave the ivory castle in which researchers have been hiding for centuries and descend in the midst of society, where it belongs. The very theory of the expansion of the Universe was the idea of a priest, Georges Lemaître, a pioneer in applying Einstein's theory of general relativity to cosmology. Astronomy continues not only to play a crucial role in knowing the universe and preserving life on Earth, but especially in educating the generation that will increasingly penetrate the extraplanetary space._x000D_ In this paper we point out several die-hard contradictions between science and spirituality, and show how Astronomy, through the IAU, has started to adapt to the needs of society, in particular how it is expected to cope with the dramatic information flare-up of the Internet age, which is accessible not only to science but also to astrology and religion, and is often mistaken for knowledge.
Nicolae Donitch – a Pioneer of the International Astronomical Union
Stavinschi, Magda
Romania has joined the IAU from the very beginning. This happened largely thanks to the astronomer Nicholas Donitch (1874-1960). His tortuous destiny was somehow similar to the destiny of many Romanians from Eastern Moldova: he was born in Chisinau, the capital of Bessarabia at that time; he studied in Odessa; later, he became a member of the Academy of Sciences of St. Petersburg, who put him in charge of major astronomical missions; after the first revolution in February 1917 he left Russia and remained in Odessa until the arrival of the Bolsheviks in 1920, who would completely destroy his laboratory; he then moved to his private Observatory in Dubasarii Vechi, which he had set up in 1908, until 1940, when Bessarabia was once again torn away from Romania. He relocated to Bucharest, but soon after, when communists came to power, he would leave the country on a permanent basis. As he severed all the ties with people from the country that had fallen into the red zone of communism, we completely lost track of him. It was only recently that, after thorough research, I could eventuallycome across his work files at CNRS (France) and his death certificate, dating back from 1960. He was passionate about the Sun's physics, having extensively observed many solar eclipses and contributed substantially to the recognition of Romanian astrophysics at the international level. In the present paper, we will try to piece together the life and work of this Romanian scholar. To him I dedicated my book "Nicolae Donitch – A Pioneer of the International Astronomical Union" (in print).
Trying to Make Sense of Polarization Patterns in Circumstellar Disks
Stephens, Ian
In the era of ALMA, we can now resolve polarization within circumstellar disks at (sub)millimeter wavelengths. While we initially hoped that these observations would give us insight on magnetic fields, the observed polarization patterns indicate other possible polarization mechanisms. These mechanisms include polarization from scattering and emission from grains aligned with the radiation anisotropy. Can we make sense of all these disk polarization observations? In this presentation, I will show many polarization observations toward disks, and I will discuss the theoretical expectations for different polarization mechanisms. Hopefully, the answer to the question will be an astounding "Yes!"
MASSES: An SMA Large Project Surveying Protostars to Reveal How Stars Gain their Mass
Stephens, Ian
Low-mass stars form from the gravitational collapse of dense molecular cloud cores. While a general consensus picture of this collapse process has emerged, many details on how mass is transferred from cores to stars remain poorly understood. MASSES (Mass Assembly of Stellar Systems and their Evolution with the SMA), an SMA large project, has just finished surveying all 75 Class 0 and Class I protostars in the nearby Perseus Molecular Cloud in order to reveal the interplay between fragmentation, angular momentum, and outflows in regulating accretion and setting the final masses of stars. In this presentation I will give an overview of the survey and highlight key science results.
The role of IAU Commission 25 in the development of photometric systems
Sterken, Christiaan
From the 1930s on it was suggested that Commission 25 takes responsibility in matters of standard stars, standard filters and standard calibration methods. Commission members expressed the desire that most of the time available to the Commission at the General Assembly should be devoted to some kind of symposium dealing with the matters of standardisation. In the 1950s a concrete proposal was formulated that the IAU should undertake the task of making standard filters generally available, but that suggestion was later withdrawn._x000D_ This presentation looks back on the opinions of key players in the photometric standardisation debate, and presents some thoughts on the current situation of the standard systems.
The Transiting Exoplanet Community Early Release Science Program for JWST
Stevenson, Kevin
The James Webb Space Telescope presents the opportunity to transform our understanding of planets and the origins of life by revealing the atmospheric compositions, structures, and dynamics of transiting exoplanets in unprecedented detail. However, the high-precision, time-series observations required for such investigations have unique technical challenges, and our prior experience with HST, Spitzer, and Kepler indicates that there will be a steep learning curve when JWST becomes operational.I will discuss our recently approved ERS program that will accelerate the acquisition and diffusion of technical expertise for transiting exoplanet observations with JWST. This program will also provide a compelling set of representative datasets that will enable immediate scientific breakthroughs. The community will exercise the time-series modes of all four instruments that have been identified as the consensus highest priority, observe the full suite of transiting planet characterization geometries (transits, eclipses, and phase curves), and target planets with host stars that span an illustrative range of brightnesses. I will also discuss plans to engage the community with a two-phase data challenge that culminates with the delivery of planetary spectra, time-series instrument performance reports, and open-source data analysis toolkits.
Star formation at low rates: how a lack of massive stars may impact stellar feedback and the evolution of dwarf galaxies
Steyrleithner, Patrick
In recent years dedicated observations have uncovered star formation at extremely low rates in dwarf galaxies, tidal tails, ram-pressure stripped gas clouds, and the outskirts of galactic disks. At the same time, numerical simulations of galaxy evolution have advanced to higher spatial and mass resolutions, but have yet to account for the underfilling of the uppermost mass bins of stellar initial mass function (IMF) at low star-formation rates. In such situations, simulations may simply scale down the IMF, without realizing that this unrealistically results in fractions of massive stars, along with fractions of massive star feedback energy (e.g., radiation and SNII explosions). Not properly accounting for such parameters has consequences for the self-regulation of star formation, the energetics of galaxies, as well as for the evolution of chemical abundances.Here we present numerical simulations of dwarf galaxies with low star-formation rates allowing for two extreme cases of the IMF: a "filled" case with fractional massive stars vs. a truncated IMF, at which the IMF is built bottom-up until the gas reservoir allows the formation of a last single star at an uppermost mass. The aim of the study is to demonstrate the different effects on galaxy evolution with respect to self-regulation, feedback, and chemistry. The case of a stochastic sampled IMF is situated somewhere in between these extremes.
NuSTAR view of the central region of M 31
Stiele, Holger
With a distance of 780 kpc and moderate Galactic absorption, the Andromeda galaxy (M 31 or NGC 224), is an ideal target to study the X-ray source population of a nearby large spiral galaxy. NuSTAR observed the central region of M 31 in 2015 and allows studying the population of X-ray point sources at energies higher than 10 keV. Based on the source catalogue of the large XMM-Newton survey of M 31, we identified counterparts to the XMM-Newton sources in the NuSTAR data. The NuSTAR data only contain sources of a brightness comparable (or even brighter) than the selected sources that have been detected in XMM-Newton data. _x000D_ Here we present our investigations of hardness ratios, spectra and long-term light curves of individual sources obtained from NuSTAR data. Based on our spectral studies we suggest four sources as possible X-ray binary candidates. The long-term light curves of seven sources that have been observed more than once show low (but significant) variability.
Dwarf Galaxies: From the Deep Universe to the Present
Stierwalt, Sabrina
Dwarf galaxies are key tools for understanding structure formation and galaxy evolution across cosmic time. These low-mass systems allow us to not only gain a detailed understanding of stellar, chemical, and dynamical properties in the nearby universe, they also provide a unique window into the complex physics of the early universe. We are in an era where increasingly powerful observing facilities and simulations are inspiring new studies of the building blocks of structure at all epochs of the universe. Our timely symposium brings together the broad dwarf galaxy community, with expertise ranging from local dwarf galaxies to massive star formation in low-metallicity environments, from simulations of feedback in a cosmological context to observations of the faint-end of the luminosity function at high redshift. I will summarize the major outstanding questions in dwarf galaxy evolution addressed in our symposium and the discussions of future challenges and opportunities presented by forthcoming facilities and chemo-dynamical simulations. _x000D_ Co-Author: Kristen McQuinn (University of Texas at Austin)
Capabilities of next generation telescopes for cosmic magnetism
Stil, Jeroen
Observations of synchrotron emission at radio wavelengths and Zeeman splitting of radio spectral lines account for most of our knowledge on cosmic magnetic fields, especially extragalactic magnetic fields. Newly upgraded telescopes and new facilities significantly improve bandwidth, angular resolution and survey speed. These improvements are changing the landscape for cosmic magnetism. How precisely? Different facilities support distinct science cases depending on their operating frequency range, in particular survey science. We review the individual strengths of these surveys, and how the combination can be bigger than the sum of the parts.
Stars and exoplanets in full Stokes IQUV
Strassmeier, Klaus
The new step forward with HIRES at the ELT would be to apply high spectral resolution polarimetry to stars with planets. It is generally known, and particularly true for the Sun, that linear polarization is much more prominent in individual spectral lines than in the continuous spectrum. An exoplanet transit breaks spherical symmetry over the projected stellar disk. It blocks the inherent (stellar) limb polarization and results in a non-vanishing linear polarization that is related to the planet’s size and orbit. Spectropolarimetry is also at hand for all out-of-eclipse situations where we can expect starlight reflected off the planet in the direction of the observer. Polarized spectral line observations at orbital quadrature of both stellar and planetary atmospheric constituents may show up strong linear polarization amplitudes, e.g., in water lines due to its molecular properties. In the search for life, time resolved linear spectropolarimetry can be used to seek evidence of special features such as a strongly polarized specular reflection, dubbed the glint that would arise from the liquid surface of an extrasolar ocean. We have proposed that the European ELT will be equipped with a high-precision polarimeter in its only rotationally symmetric focus (the intermediate focus) that is capable of feeding its High Resolution Spectrograph HIRES.
Observing Programs and Opportunities for Cycle 1
Strolger, Louis-Gregory
I plan to provide an overview of the observing programs for Cycle 1 of JWST. This will include some description of the planned Guaranteed Time Observations, provided in return for contributions to the development of key components of the observatory. I will also cover the planned Director’s Discretionary Early Release Science observations, an initiative to accelerate access to data and science products and realize JWST’s full science potential. Lastly, I will discuss the opportunities and timeline for General Observer and Archival programs in the cycle.
Calibrating Next Generation Sky Surveys
Stubbs, Christopher
A complete determination of the instrumental response function, including both the atmospheric and instrumenal aspects, is an essential ingredient in the photometric calibration for next-generation surveys such as LSST and WFIRST. I will describe the approaches being pursued by these projects, and the sources of systematic uncertainty that we must overcome.
Nano dust as a possible cause of hot emission in planetary debris disks
Su, Kate
Planetary debris disks are tenuous disks consisting of dust replenished by collisions of leftover planetesimals and cometary activity, events that are driven through gravitational shepherding and stirring by planets. Their large surface area makes these disks detectable through infrared thermal emission and/or optical scattered light, providing insights into the nature of unseen minor-body populations and the underlying planetary architecture. The majority of the disks show warm and cold dust emission in a structure analogous to that of minor body belts in the solar system with asteroid- and/or Kuiper-belt components. A significant fraction of main sequence stars observed interferometrically in the near-infrared have extended excess emission that has been attributed to very small (<200 nm) hot dust in the vicinity of the stars. Various mechanisms have been proposed to explain the origins of these nanograins, particularly with regard to how they are retained in the presence of significant radiative pressure forces around early-type stars. Similar to the nanograins in the inner solar system, these nano particles are likely the products of (1) sublimation from stellar grazing planetesmials, (2) photoelectric charged by the stellar wind, and (3) magnetically trapped by the magnetic field of the star. I will review recent observational and theoretical studies of nanograins in planetary debris disks, and discuss future observational tests in these systems.
Effectively Coordinating Museums and Planetariums Worldwide
SubbaRao, Mark
Informal science educators at museums and planetariums face the challenging task of engaging a diverse public audience in contemporary science. To do this they need a solid background in the science itself, educational pedagogy, and modern practices in science communication. The task has gotten even more challenging in the era of big data. Interpreting and visualizing these datasets in planetarium shows and museum exhibits requires specialized technical skills. Furthermore, the increasing pace of discovery means that informal science educators have less time to accomplish these tasks. This presentation will summarize a variety of museum and planetarium community efforts to address these challenges through worldwide collaboration and coordination among museums and planetariums. Solutions include content sharing and distribution mechanisms as well as networking museums and planetariums together to create global worldwide events.
Origins of cosmic magnetism
Subramanian, Kandaswamy
The universe is magnetised from stars to the large-scale coherentmagnetic fields detected in galaxies and galaxy clusters, andeven perhaps the intergalactic medium in voids. The standardpicture for the origin of fields in all astrophysical systems involvesturbulent dynamo amplification of a weak seed magnetic field. In suchdynamos the kinetic energy of motions get converted to magnetic energy.We review the basic idea behind such dynamos and the main challenges theyencounter. While it is relatively easy for magnetic energy to grow,explaining the observed degree of coherence of cosmic magnetic fieldsgenerated by turbulent dynamos, remains challenging. We outline potentialresolution of these challenges, ending with a new paradigm for rapidunified growth of both large and small scale fields in galaxies.
Numerical Simulations of Catastrophic Impacts Resolving Shapes of Remnants
Sugiura, Keisuke
Asteroids in an asteroid family are considered to be fragments formed through collisional destruction of single parent body. Thus, statistical information obtained from an asteroid family such as size or rotation rate distribution may provide some insights into the physics of collisional destruction. Asteroids have another unique statistical information, that is, irregular shapes. Irregular shapes of asteroids are formed through reaccumulation of fragments after catastrophic disruption due to asteroidal impacts and can be important information to investigate the origin of that family._x000D_ In this study, we perform high resolution simulations of asteroidal collisions, and reproduce statistical information of many asteroids formed through catastrophic disruption. We use Smoothed Particle Hydrodynamics (SPH) method for elastic dynamics (Libersky and Petschek 1990) with the self-gravity, the model of fracture of brittle solid (Benz and Asphaug 1995), and the model of friction of disrupted material (Jutzi 2015). Our simulation code is parallelized using MPI and OpenMP with the aid of Framework for Developing Particle Simulator (FDPS: Iwasawa et al. 2015, 2016)._x000D_ We conduct some simulations of catastrophic impacts. An equal-mass impact of asteroids with radii 50 km and the impact velocity of 350 m/s produces the largest remnant with mass of about 0.1 of that of an initial asteroid, i.e., catastrophic disruption. Exponent of the cumulative size distribution is about -2.4. The rotation rate distribution has the peak at 10 hours, and most remnants have rotation rate between 5 and 20 hours. Most of remnants have spherical shapes, and bilobed shapes are also formed through coalescence of two spherical remnants. We find five bilobed remnants with the ratio between intermediate and major axis length less than 0.6. We also find a trend that smaller remnants have larger axis ratios, i.e., rounder shapes.
Circumstellar dust, IR spectroscopy, mineralogy
Suh, Kyung-Won
In this work, we review IR spectroscopic studies of the circumstellar dust grains around AGB stars. The expanding envelopes of AGB stars are chemically fresh because of the strong binding force of CO molecules. O-rich dust grains (silicates, Al2O3, water ice, and other oxides) form in the O-rich envelopes and C-rich dust grains (amorphous carbon and SiC) form in the C-rich envelopes. Amorphous silicate grains could be efficiently crystallized by annealing processes in various environments of AGB stars. We also discuss dust mineralogy for objects that have undergone chemical transition processes.
Perfect Blackbody Spectra for Next Generation UV-Opt-IR Standard Star Network
Suzuki, Nao
In the era of precision cosmology, we are in need of advancing photometric standard star network system. Especially, Type Ia Cosmology is now being limited by systematic errors and one of the majour sources is the photometric standard stars and their models. Also, we are in need of bridging UV-Opt system (ABmagnitude) and IR system which most of the standars are still in Vega magnitude system. We would like to propose to make use of stars with nearly perfect blackbody spectra. We identified a dozen of blackbody stars from the Sloan Digital Sky Survey and they are consistent with balckbody from UV (GALEX), Optical (SDSS and Pan Starrs) through IR (WISE). With only two parameters (Temperature and Normalization), we can describe UV-Opt-IR magnitude and its error in subpercent level and avoid propagation of errors from the detectors. These are special type of white dwarfs and GAIA satellite provide us their distances which enables us to deduce their radius. We present its potential use in this presentation.
High Redshift Supernova Survey with ELTs
Suzuki, Nao
In the era of ELTs, one of the holy grails of observational cosmology is to discover the signs of 'First Star’ and their explosions. It is very important to understand how the first generation of stars were born and ionized the universe, how massive black holes were formed and seeded the formation of the galaxies. The 'First Star' bridges many area of studies in astrophysics, and the surveys by ELTs would be critical.In 2020s, LSST would discover millions of supernovae, and cosmological parameters would be listed as a table on the back page of your text book. However, the nature of dark energy still remains as a mystery. ELTs are capable of probing high-z universe where the expansion is decelerating (z>1). Also, ELTs can investigate rare events such as gravitationally lensed Type Ia supernovae and test general relativity as well as cosmological parameters. It’s not only distant universe, but ELTs would revolutionize the view of nearby universe. As of today, we do not have a definitive answer of the progenitor system of Type Ia supernovae, but ELT should be able to reveal the identity of its companion star in the nearby universe. Cepheid variable measurements can be extended to cosmological distances, and we may be able to find inhomogeneous expansion of the local universe.Reverberation Mapping of AGNs enters new era if we can resolve the dust torus with TMT. ELTs would advance the era of “High Precision Cosmology”. New distance indicators, Fast Radio Burst (FRB) and Gravitational Wave as a standard siren could become more common in 2020s. Time domain science with ELTs has a promising future. However, it is always true that "the great ocean of truth lay all undiscovered before" us. The most exciting ELT discovery would be something we have not listed yet, but we should always be well prepared for the new discovery.
Spatially resolved observations of angular momentum as a tracer of galaxy morphology and evolutionary history
Sweet, Sarah
Specific angular momentum (j) is a fundamental parameter in the evolution of galaxies, because it traces the tidal torques experienced during their lifetimes. The total j of a galaxy disk agrees with that of its dark matter halo, but the distributions are different, in that there is a lack of both low- and high-j baryons with respect to the CDM predictions. This discrepancy could arise during disk assembly if the baryons experience additional physical processes. For instance, gravitational torques due to interactions with neighbours in a dense environment can cause tidal stripping, removing outer, high-j material, while feedback due to AGN or stellar winds can remove inner, low-j material. Galaxy specific angular momentum is also related to its morphology. The distribution of j is different for disks and classical bulges; disks are expected to be dominated by rapidly-rotating material with a well-defined analytical solution x*exp(-kx), while bulges have little or no ordered rotation, Gaussian-smeared by random motions. The distribution of specific angular momentum PDF(j) therefore has two-fold utility: (1) comparison against model PDF(j) indicates the proportion of low-j and high-j material that has been lost, and the relative importance of feedback vs. tidal stripping; (2) the two-function fit can be used as a kinematic thin-disk decomposition. I will review the literature on this emerging topic and present my own work, illustrating how PDF(j) can inform us of a galaxy's morphology and evolutionary history with a spanning set of examples from present-day, cosmic-noon (z=1.5) and cosmic-noon analogue galaxies.
The Kepler Pixel Project
Szabo, Robert
Kepler photometry is so precise that new ways can be developed to harvest the great wealth of quasi-continuous data that has never been accessible from the ground. We have initiated a new project that we dub The Kepler Pixel Project in order to explore approaches and to discover new pulsating stars and other time-variable objects.In this endevour we examine individual pixels of the original Kepler mission to find interesting objects around the main Kepler targets. Specifically we launched a project to find background, faint RR Lyrae stars that are missing from the Kepler sample. In this talk the first results of The Kepler Pixel Project are presented. We will discuss the project, the search algorithms, new findings, as well as the properties of the enlarged Kepler RR Lyrae sample.We will also show other results and examples (asteroseismology, new eclipsing binaries, transiting exoplanets, flares, outbursts) to demonstrate the potential and future avenues of the project.
The 30 micron sources in galaxies with different metallicities
Szczerba, Ryszard
I will present an analysis and comparison of the 30 micron dust features seen in the Spitzer Space Telescope spectra of 207 carbon-rich Asymptotic Giant Branch (AGB) stars, post-AGB objects, and planetary nebulae located in the Milky Way, the Magellanic Clouds or the Sagittarius Dwarf Spheroidal galaxy, which are characterised by different average metallicities. Our analysis uses the ``Manchester method'' as a basis for estimating the temperature of dust for the carbon-rich AGB stars and the planetary nebulae in our sample. For post-AGB objects we changed the wavelength ranges used for temperature estimation, because of the presence of the 21 micron feature on the short wavelength edge of the 30 micron feature. We have found that the average feature is identical for different metallicities, for AGB and post-AGB stars, while is shifted to significantly longer wavelengths in case of planetary nebulae. We have produced online catalogues of photometric data and Spitzer IRS spectra for all objects that show the 30 micron feature. These resources are available online.
Deciphering the traces of mixing processes in interiors of massive g-mode pulsators
Szewczuk, Wojciech
Our understanding of massive star physics is still deficient.This is mainly due to imperfect description of mixing processes which strongly affectthe structure and evolution. The processes like overshooting from convective regionsor rotational-induced mixing are described by free parameters which are poorly calibrated.Seismic studies of Slowly Pulsating B-type stars (SPB) gives a hope for progress in this issue.Inside these pulsators the buoyancy waves (called g modes) are excitedand they are very sensitive to the conditions prevailing in the deep interior.The traces of mixing processes are saved in particular in the period spacingwhich was identified in many B-type stars observed by Kepler.Using MESA evolutionary code and taking into account the effects of rotationin nonadiabatic pulsational computation, we try to get constraints on mixing parameters.
The Role of Magnetic Fields in Evolution of Galaxies
Tabatabaei, Fatemeh
The origin and evolution of cosmic magnetic fields as well as the influence of the magnetic fields on the evolution of galaxies are unknown. Scaling relations can provide important insight on the way the magnetic field is maintained in galaxies. I present the scaling relations between the strength of the magnetic fields and other physical properties both locally and globally from two samples of nearby galaxies and discuss possible deviations in galaxy centers. These regions are found to be controlled by the nonthermal pressure from the magnetic fields, cosmic rays, and turbulence. Our recent study in the central kpc of NGC1097- a prototypical galaxy undergoing quenching- shows that the star formation efficiency drops significantly with the magnetic field strength. Hence, a progressive built up of the magnetic field can result in high-mass stars forming inefficiently and further help the formation of the big bulges of low-mass stars seen in quenched galaxies.
Untangling galaxy components: the angular momentum of bulges and disks in the MaNGA survey
Tabor, Martha
Deciphering where and when a galaxy's constituent stellar populations formed is crucial in understanding how that galaxy has formed and evolved. Photometric bulge-disk decompositions have long been used as a first order approximation of this; separating out the light from the central and extended components of a galaxy in order to compare colours and morphologies. However, photometric decompositions do not allow the determination of the kinematics of the individual stellar populations, which can reveal a great deal about the evolution history of a galaxy. We have therefore developed a method to extract the kinematics of multiple components in galaxies using IFU data and have applied it to a sample of MaNGA early type galaxies. This allows us to explore the angular momentum of bulges and disks separately and begin to understand the role each plays in determining the global angular momentum of a galaxy.
Helical Magnetic Fields in Molecular Clouds? A New Method to Determine the Line-of-Sight Magnetic Field Structure in Molecular Clouds
Tahani, Mehrnoosh
We present a new method to find the line-of-sight strength and morphology of magnetic fields in star forming regions using Faraday rotation measurements. In this method, we use rotation measure data from the literature and adopt a simple approach, based on relative measurements, to estimate the amount of rotation measure induced by the molecular clouds versus that from the rest of the Galaxy. We then use a chemical evolution code, along with extinction maps of each cloud, to find the electron column density of the molecular cloud at the position of each rotation measure data point. Combining the rotation measures produced by the molecular clouds and the electron column density, we calculate the line-of-sight magnetic field strength and direction.We applied this method to four relatively nearby regions of Orion A, Orion B, Perseus, and California. In the California cloud and Orion A, we found clear evidence that the magnetic fields at one side of these filamentary structures were pointing towards us and were pointing away from us at the other side. This behaviour is consistent with a helical magnetic field morphology. In the vicinity of available Zeeman measurements in Orion A, Orion B, and Perseus, we found magnetic field values of -23 ± 38 µG, -129 ± 28 µG, and 32 ± 101 µG, respectively, which are in agreement with the Zeeman Measurements.
Toward understanding of the production and evolution of large solar flares
Takasao, Shinsuke
Solar flares, known as the most explosive phenomenon in the solar system, are a prototype of various kinds of explosions in the universe. Among them, large solar flares have particularly received remarkable attention because of their significant impact on the interplanetary space. During my Ph.D., I have been exploring two long standing problems associated with large flares; the formation of flare-productive regions and the energy release process of magnetic reconnection.The first problem is how active regions which produce large flares are formed. It has been known for decades that active regions with a certain photospheric magnetic configuration (so-called delta-spot regions) are responsible for the production of the most violent flares. To understand their origin, we carried out an 3D magnetohydrodynamic (MHD) simulation where a subsurface highly twisted flux tube emerges from the solar interior to the corona. This talk demonstrates that the strongly twisted tube can spontaneously form a multipolar structure with a strong magnetic shear which is flare-productive.The other problem regarding solar flares is, why flares often show quasi-periodic pulsations (QPPs) in their lightcurves. QPPs are a common phenomenon not only for solar flares but also for stellar flares, and are believed to tell us about the information of the energy release site which is almost impossible to observe directly. Although many mechanisms have been proposed, the lack of a comprehensive modeling have made it difficult to link the oscillation and its driver. We carried out a set of 2D MHD simulations of a solar flare in which magnetic reconnection, heat conduction, and chromospheric evaporation are considered. As a result, we discovered that a newly found oscillation is prominent in our simulations; the local oscillation above the flare loops that is controlled by the backflow of the reconnection outflow. We will discuss the new mechanisms and the connection with observations in this talk.
Dust formation around aluminum oxide-rich AGB stars: condensation experiments in the Al-Si-O system
Takigawa, Aki
Mid-infrared spectroscopic observations of dust shells around oxygen-rich asymptotic giant branch (AGB) stars indicated that materials emitting a broad peak at 11-12 µm abundantly coexist with amorphous silicate dust around many of these stars (Sloan et al. 2003). Amorphous aluminum oxide synthesized by a sol-gel method well reproduces that emission, but it is not obvious that amorphous aluminum oxide can condense around these stars because of its very high glass transition temperature. Possible compositions of amorphous materials reproducing a broad 11-12 µm peak other than pure aluminum oxide have not been examined. We carried out condensation experiments of Al-Si-O gases using the induction thermal plasma system (Kim et al 2017). Aluminum and silicon powders with various mixing ratios (only Al, Al/Si = 9, 3, 1, 0.08, and only Si) were used as starting materials. They were evaporated at high temperature in Ar-O2 plasma flames (~10000 K) and rapidly cooled (104~105 K/s). The condensed particles were analyzed with X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy, and observed with transmission electron microscope. The condensed nanoparticles from evaporated aluminum was d-alumina. Particles with structures similar to ?-alumina were observed in condensates from starting materials of Al/Si=9 and 3. Amorphous particles were also observed in samples with Al/Si<3 and no crystals was observed in condensates from samples with Al/Si<1. The FT-IR spectrum d-alumina shows multiple peaks on a broad feature at 11-14 µm, which is not observed in circumstellar dust emissions. Condensates from starting materials of Al/Si = 9 and 3 shows peaks at slightly longer than observed dust emission but well reproduces its spectral shape.These results indicate that the carrier of 11-12 µm broad emission is not pure aluminum oxide but amorphous materials containing 10-30% of other elements including Si.
Dust formation from vapor through multistep nucleation in the astrophysical environments
Tanaka, Kyoko K.
Cosmic dust grains are believed to form in outflows in the late stages of evolution of stars such as AGB stars and supernovae. The condensation and crystallization processes are important for understanding the origin of cosmic dusts and have seen by various observations. For instance, the silicate dusts condense in outflows with amorphous structure, as evidenced by the broad and smooth appearance of around 9.7 micron spectrum of silicate. Some observations suggest an increase in the fraction of crystalline as it cools from an intrinsic change in optical properties of the dust (Waters et al. A&A 315, L361,1996). Despite the transition from vapor to solid is a familiar process, the process is not fully understood yet. One reason is that size of nuclei is usually very small (< nm) and the properties of nuclei are poorly understood. In the study, we present molecular dynamics (MD) simulations of vapor-to-solid phase transition with a simple potential model (Lennard-Jones type) and discuss the transition process. In the simulations, the nuclei of supercooled liquid appear and growth. After the growth of nuclei, the crystallizations of supercooled nano-clusters are observed and the crystallized nano clusters have various structures of metastable phase (Tanaka et al. Phys. Rev. E 96, 022804, 2017). Our simulations indicate that the vapor-to-solid transition occurs through multistep nucleation which is vapor-to-liquid nucleation (first step nucleation) and crystallization in the supercooled liquid droplets (second step nucleation), even though the temperature is much lower than the triple temperature. Recent experimental studies support the multiple processes of nucleation for various substances including silicate materials (Ishizuka et al. ApJ, 803:88, 2015). Our results with the experiments indicate that the multistep nucleation is a common phenomenon in the first stage of condensation from vapor to solid in the astrophysical environments.
Multiple Feedback in Low-Metallicity Massive Star Formation
Tanaka, Kei
To glimpse the variation of the high-mass end of IMF throughout the cosmic history, we theoretically investigate the impact of feedback and its metallicity dependence in massive star formation from prestellar cores at all metallicity range of Z=0-1Zsun (Tanaka et al. 2017, ApJ, 835, 32; Tanaka et al., in prep.). We include the feedback by MHD disk winds, radiation pressure, and photoevaporation solving the evolution of protostars and accretion flows self-consistently. Interestingly, we find that the feedback does not set the upper-mass limit of stellar birth mass at any metallicity, which is consistent with recent observations in the Large Magellanic Cloud (Crowther et al. 2010, 2016; Schneider et al. 2018). At the solar metallicity, we show that the MHD disk wind is the dominant feedback to set the star formation efficiency (SFE) from the prestellar core similar to low-mass star formation. The radiation pressure, which had been believed to be crucial for a long time, has a minor contribution even in the formation of over-100Msun stars. On the other hand, at the low metallicity of Z<1e-2Zsun, the photoevaporation becomes significant because the absorption of ionizing photons is weaker. Due to this efficient photoevaporation, the SFE gets lower at lower metallicity environments. Considering this SFE change and prestellar-core mass-function at low metallicity (Omukai & Tsuribe 2005), we conclude that the IMF slope is steeper, i.e., massive stars are rarer especially at 1e-5 - 1e-3Zsun compared to the local environment. Our study raises a question on the common assumption of the universal IMF with 100Msun cutoff. Since the total feedback strength in the cluster/galaxy scale is sensitive to the number fraction of massive stars, the re-evaluations of IMF at various environments are necessary.
Analysis of the historic meteorite falls
Tancredi, Gonzalo
The worldwide accepted clearing-house of meteorites is the Meteoritical Society, which maintains the Meteoritical Bulletin Database (hereafter MBD), a collection of information about recovered meteorites from all over the world. Up to end 2017, there are 57108 registered meteorite names with their respective taxonomic classification.Meteorites recovered following observed passage through the atmosphere are called falls; while those which are serendipitously found or they cannot definitely be associated with a passage are called finds. In the MBD there are 1161 registered meteorites falls with official names. We combine the information of the MBD and other databases to analyze the time distribution of meteorite falls. The database includes information of falls extended for several centuries, but with a uniform coverage over the last century. We compute the frequency of falls as a function of the day of the year and the Sun's longitude. The frequency is compared with a Poisson process to look for dates with a frequency larger than expected; which it could be a signal of a meteorite stream.A subset of the falls that generate a lot of concern are those meteorites that directly impact human beings or their belongings, we call them “damaging falls”. From an analysis of the registered meteorite falls and the damaging subset in the last century, we calculate an average rate of 7.25 falls and 1.25 damaging falls over the urban land per year registered in the database. We then estimate ~5600 falls per year over the entire Earth and ~1600 over the land.
Gaia DR2: astrometry of small Solar System bodies
Tanga, Paolo
A review of the properties of Gaia observations of asteroids in DR2 and the best approach to exploit them are presented. The results from orbital fits reach the sub-mas accuracy. The combination of additional ground-based astrometry, with the difficulty to receduce zonal errors of past astrometric catalogs, is discussed. The expected progress in different domains, including the prediction of stellar occultations and the detection of Yarkovsky drift for a larger sample of objects, are now at the reach of the community.
Unbound warm/hot gas in filaments and superclusters
Tanimura, Hideki
We search for the Sunyaev-Zeldovich signal in unbound gas: in filaments and in superclusters. We focus on filaments between ~ 260,000 pairs of Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey Data Relase 12 (SDSS DR12) tracing the large scale structure of the Universe. By stacking the LRG pairs, we estimate the SZ signal in the Planck data between them as y = (1.31 ± 0.25) × 10-8 at 5.3 s significance, marginally consistent with simulations. Assuming a simple model for all the filaments, the over-density of the electron gas in the filaments is found to be d = 3.2 ± 0.6.We also search for the SZ signal from the unbound gas outside clusters in 580 superclusters from the SDSS DR7. After stacking the superclusters, we estimate the SZ signal as y = (3.0 ± 1.4) × 10-8 at 2.2 s significance. Assuming a temperature of 106.5 K and simple model for unbound gas distribution, we find the over-density of the electron gas d = 2.3 ± 1.4.
XARM ability for the distant warm hot plasmas
Tashiro, Makoto
In this paper, we demonstrate the JAXA-NASA joint mission X-ray Astronomy Recovery Mission (XARM) ability to measure the chemical evolution in the early universe utilizing the X-ray afterglows of gamma-ray bursts (GRBs) and distant blazars at redshift of z > 2 as background light sources and to constrain the physics of jetted emission from these sources. XARM carries an X-ray micro-calorimeter with an X-ray Mirror Assembly named Resolve. As shown in the ASTRO-H whitepaper (Tashiro et al. 2015), the combination of the X-ray Mirror and the X-ray micro-calorimeter has a capability to search for redshifted emission and absorption features from heavy elements in the ejecta of GRB explosions, circumstellar material in the host galaxies and perhaps from the inter-galactic medium (IGM) in the soft-X-ray spectra of GRB afterglows and distant blazars, because of its combination of high spectral resolution, broad band pass, large collecting area and low background. In addition to the purpose above, the combination of the Resolve and Xtend (X-ray CCD camera system) will measure the temporal behavior of the spectral continuum of GRB afterglows and blazars. The ability to obtain these data from GRB afterglows will depend critically on the availability of GRB triggers and the capability of XARM to respond rapidly to targets of opportunity. At the present time it seems as if Swift will still be functioning normally during the first two years of XARM operations providing the needed triggering capability.
XARM ability for the distant warm hot plasmas
Tashiro, Makoto
In this paper, we demonstrate the JAXA-NASA joint mission X-ray Astronomy Recovery Mission (XARM) ability to measure the chemical evolution in the early universe utilizing the X-ray afterglows of gamma-ray bursts (GRBs) and distant blazars at redshift of z > 2 as background light sources and to constrain the physics of jetted emission from these sources. XARM carries an X-ray micro-calorimeter with an X-ray Mirror Assembly named Resolve. As shown in the ASTRO-H whitepaper (Tashiro et al. 2015), the combination of the X-ray Mirror and the X-ray micro-calorimeter has a capability to search for redshifted emission and absorption features from heavy elements in the ejecta of GRB explosions, circumstellar material in the host galaxies and perhaps from the inter-galactic medium (IGM) in the soft-X-ray spectra of GRB afterglows and distant blazars, because of its combination of high spectral resolution, broad band pass, large collecting area and low background. In addition to the purpose above, the combination of the Resolve and Xtend (X-ray CCD camera system) will measure the temporal behavior of the spectral continuum of GRB afterglows and blazars. The ability to obtain these data from GRB afterglows will depend critically on the availability of GRB triggers and the capability of XARM to respond rapidly to targets of opportunity. At the present time it seems as if Swift will still be functioning normally during the first two years of XARM operations providing the needed triggering capability.
Simulating putative Enceladus-like conditions: The possibility of biological methane production on Saturn's icy moon
Taubner, Ruth-Sophie
Enceladus is one of the most remarkable objects in the Solar System. Besides its spectacular plume located near its south pole, it is the origin of the plume particles which makes Enceladus to one of the hot spots in Astrobiology nowadays: a subsurface liquid water ocean (e.g., Cadek et al., 2016). The molecules detected in the plume (Waite et al., 2009) including water (H2O), carbon dioxide (CO2), and methane (CH4), in combination with the possibility of hydrothermal vents at the ocean floor (Hsu et al., 2015), lead to the assumption that this icy moon might be habitable for life as we know it. The final evidence for molecular hydrogen (H2) in the plume, produced most likely by serpentinization of olivine in the chondritic core (Waite et al., 2017), made this assumption even more likely.Possible life forms on Enceladus could be chemotrophic, i.e. independent of products of photosynthesis, and would need to be anaerobic, i.e. independent of molecular oxygen. Hydrogenotrophic methanogens, i.e. archaea that metabolize H2 and CO2 to produce CH4 and H2O, are among the organisms that meet these characteristics. In this study we raise the question, if some of the CH4 detected in the plume could in principle originate from biological activity.We tested three different methanogenic archaea (Methanothermococcus okinawensis, Methanothermobacter marburgensis, and Methanococcus villosus) under putative Enceladus-like conditions, i.e. high pressure experiments including tests on the tolerance towards potential gaseous and liquid inhibitors detected in Enceladus’ plume. In particular, M. okinawensis, an isolate from a deep marine trench (Takai et al., 2002), showed tolerance towards all of the added inhibitors and continue performing methanogenese also for experimental pressure comprised between 3 and 50 bar (Taubner et al., 2018). The experiments indicate that conditions on Enceladus are not so different from some localities on Earth and could perhaps sustain methanogenic life.
A Newly Discovered Reservoir of Dwarf Galaxies in the Centaurus A Group
Taylor, Matthew
Recent years have seen an acceleration in the discovery rate of dwarf galaxies in the Local Universe. The subsequent unveiling of coherent satellite phase-space structures like groups and planes has led to a renaissance in the study of low-surface brightness dwarf galaxies, including their utility in near-field cosmological studies. In an effort to push this field further, optical u'g'r'i'z' imaging of 22 deg^2 centered on the nearby giant elliptical galaxy NGC5128, as part of the "Survey of Centaurus A's Baryonic Structures" (SCABS) campaign, has been searched for new dwarf galaxies in the Centaurus A group. We will present first results of the stellar mass and stellar population properties for several dozens of promising new candidates, including several dwarf pairs appearing within a few pc in projection that may indicate physical associations. These new dwarf galaxies extend the size-luminosity relation toward fainter total luminosities and smaller sizes for known dwarf galaxies outside the Local Group, and are broadly consistent with the properties of nearby dwarf spheroidal galaxies. Altogether, these new results show NGC5128 to be the host of a large reservoir of low-mass dwarf galaxies that is at least as rich as that of the Local Group and is ripe for detailed follow-up observations.
Disks, jets, and other black hole-powered transients
Tchekhovskoy, Alexander
Black holes are responsible for a wide variety of astrophysical phenomena. They devour stars, eject relativistic jets, affect star formation and galaxy evolution, and enrich the Universe with heavy elements. I will discuss how global general relativistic magnetized fluid dynamics numerical simulations allow us to use this activity to quantitatively probe strong-field gravity and constrain black hole physics in various astrophysical contexts.
Early CME evolution and associated phenomena in the solar atmosphere
Temmer, Manuela
Coronal mass ejections (CMEs) and flares are the most energetic activity phenomena in the solar system. Earth-directed CMEs are the main drivers of strong geomagnetic storms and therefore are an area of intense research interest. How CMEs get initiated and driven, how impulsive these events may become and in which direction they further propagate, are crucial inputs for Space Weather forecasting. Signatures in the low solar atmosphere that are associated to CMEs reflect best the characteristics of the CME early evolution. Hence, studying solar on-disk multi-wavelength data is essential for a better understanding of the physical processes that drive CMEs and their behavior in interplanetary space. Especially the CME related dynamic phenomena of solar flares, coronal waves and dimmings give a wealth of information for Earth-directed CMEs, that are usually hard to observe and characterize from traditional white-light observations. This overview talk discusses our recent understanding of the physical processes about the initiation and early propagation of CMEs that could be gained by combined multi-wavelength and multi-instrument data.
Gaia & ELTs: quantitative stellar astrophysics
Thévenin, Frédéric
Gaia is delivering the second release this year producing 1.3 billion star measurements in particular parallaxes and proper motions. This represents a great progress for astrophysical knowledges mainly for the galactic structure and the stellar physics which are tied together. At the end of the nominal mission, the release of 2022 Gaia DR4 will definitively change our understanding of the Universe and it will represent a very important basis for future stellar astrophysics understanding based on ELTs, JWST and PLATO collect of data. The present status of the satellite, of the published Gaia DR2 and of the foreseen Gaia DR3 will be discussed. Links with asteroseismology and interferometry will be presented, but the talk will focus more on the synergy with ELTs in this important phase of preparation of ELTs instruments in the context of stellar physics.
An Extended Moonwatch in the Middle East in 860 CE for Determining Empirically a Critical Value for Lunar Crescent Visibility
Thomann, Johannes
In the years from 1987 to 1990, five organised Moonwatches took place in North America. The results were used to evaluate different models for the visibility of the lunar crescent, including historical criteria from Babylonian and Arabic astronomers (Doggett/Schaefer 1994). Already in the 9th century this empirical method was in use. The ingenious astronomer ?abash al-?asib established in his Damascene Zij the most elaborate model for predicting visibility ever formulated in pre-modern times. It was praised by al-Biruni in the Masudic Canon as the best available criterion. However, despite ?abash’s fame, his Zij remains unpublished. ?abash begins by describing his model in general terms and introducing a threshold value, for which he gives no explanation. Then, he explains the model by providing an example for November 860 CE. Finally, ?abash reports that the moon was seen in Kufa, Anbar and cities in Syria, but not in Baghdad and Samarra. Obviously, his threshold value was chosen to match these data points. According to a modern estimation, the crescent could have been seen in Baghdad. Weather conditions might have not been favorable in November 860. Indeed, the historian al-?abari recorded heavy showers in Baghdad for that month. This leads to more general considerations. The Muslim calendar was regulated by sighting of the lunar crescent at the evening of the 29th of each month. Every historical record of a month of 29 days is a witness of a positive observation of the crescent, and every record of a month of 30 days is a negative one. Calendars were regulated locally and differed from city to city. Therefore, the enormous annalistic Arabic literature is a huge archive of thousands of Moonwatches undertaken in a large territory from the Atlantic to Aral sea and beyond, which could be used as proxy data for atmospheric phenomena.
Metallicity gradients and galaxy formation.
Tissera, Patricia
The chemical abundances of the gas-phase and stellar components of galaxies are key importance to undertand galaxy formation and evolution.It has been shown that an inside-out disc formation yield negative chemical profiles globally. However, a large spread in metallicity gradients has been reported by recent and more precise observations,suggesting the action of other physics processes such as gas outflows and inflows, radial migration, andmergers and interactions.Cosmological simulations including chemical models provide a tools to tackle the origin of the metallicityprofiles and the action of those processes which might affect them as a function of time.In this talk I present a summary of the current state-of-knowledge from a numerical point of view and discuss the main results from the analysis of the EAGLE simulations.
Mapping of the asteroid families
Todorovic, Natasa
In a recent study, we produced clear dynamical maps of some regions in the main belt,which enabled us to observe efficient dynamical pathways along which particles can driftaway in short times.In a similar fashion, we map the regions of two asteroid families: Themis and Hungaria.Clear dynamical maps, computed with a good choice of parameters, will enable us to reexamine the role of the neighboring resonances in the distribution of asteroids inside a family, to identify their erosion routesand to get a refined global picture on their dynamics.
Plenary Session: Resolved stellar populations: the outlook for JWST and ELT
Tolstoy, Eline
I will give an overview of the future of resolved stellar population studies of nearby galaxies as we move towards the era of JWST and ELT.I will discuss the science capabilities of two major future facilities, ELT and JWST, and how they can be utilised to make major break throughs in our understanding of important processes in galaxy evolution through the study of individual stars. They will both add extraordinary new detail to the resolved studies of nearby galaxies. As the telescopes get larger and more sensitive the local volume that can be resolved into individual stars also gets larger, and thus includes a wider range of different galaxy types. Deep resolved colour-magnitude diagrams will allow us to probe the star formation histories of systems that hither to have only been studied in integrated light, or only their bright young stellar populations have been resolved. We can hope to obtain deep and detailed observations of bulges and disks in a range of different type and mass of spiral galaxies. We can even hope to resolve individual luminous red and asymptotic giant branch stars in giant Elliptical galaxies at the distance of Virgo. We will also be able to complement the imaging of resolved stellar populations with spectroscopy of ever more distant individual stars.
Accreting magnetars: stellar winds and accretion
Torrejon, Jose Miguel
Magnetars are isolated neutron stars with extreme magnetic fields of up to 10^15 gauss. Their X-ray emission is powered by the decay of this gigantic field. There is a growing, albeit indirect, evidence on the existence of such a highly magnetised neutron stars (10^13-14 gauss) in many High Mass X-ray Binaries accreting from the powerful winds of their massive companions: the accreting magnetars. In this talk I will present X-ray observations of some candidates and explore what are their main observational properties and how do they help us to understand the stellar winds from their massive companions.
A systematic search for protoclusters at z~4 based on the >100deg^2 area
Toshikawa, Jun
We conduct a systematic search for galaxy protoclusters at z~3.8 based on the Hyper Suprime-Cam Subaru strategic program (HSC-SSP). In the Wide layer of the HSC-SSP, we investigate the large-scale projected sky distribution of g-dropout galaxies over an area of 121deg2, and identify 216 large-scale overdense regions (>4s overdensity significance) that are likely protocluster candidates. The unprecedented size of our protocluster candidate catalog allows us to perform, for the first time, an angular clustering analysis of the systematic sample of protocluster candidates. We find a correlation length of 35.0h-1Mpc. The relation between correlation length and number density of z~3.8 protocluster candidates is consistent with the prediction of the _x0003_CDM model, and the correlation length is similar to that of rich clusters in the local universe. This result suggests that our protocluster candidates are tracing similar spatial structures to those expected from the progenitors of rich clusters. Following this protocluster search, we are now performing follow-up observations to investigate the physical properties of protoclusters. Optical spectroscopy is carried out for four protocluster candidates by Keck/DEIMOS and Gemini/GMOS. The fraction of Lya emitters among g-dropout galaxies in overdense regions is found to be significantly smaller than that in field. This implies that protocluster galaxies are dustier or there is a large amount of neutral hydrogen gas in protocluster regions. In addition, five protocluster candidates are observed by the submm imaging of JCMT/SCUBA2 to search dusty star-burst galaxies. We will present the systematic search for protoclusters and the initial results of these follow-up observations. In years to come, our protocluster search will be extended to the entire HSC-SSP Wide sky coverage of ~1400deg2 to probe cluster formation over a wide redshift range of z~2-6.
From the Protosun to the First Steps of Life - a review of IAUS 345
Toth, L. Viktor
I will review the topics and summarize the results presented at the IAU Symposium 345 "Origins: From the Protosun to the First Steps of Life".
Characterisation of Long Period Variables in the Magellanic Clouds
Trabucchi, Michele
Asymptotic Giant Branch (AGB) stars often exhibit pulsation in modes of low_x000D_ radial order and periods between a few days and a few thousand days._x000D_ The observed periods and variability amplitudes of such Long-Period Variables (LVPs)_x000D_ provide an additional constraint to be matched by stellar evolution and population models,_x000D_ as well as a powerful tool to infer stellar parameters. LPVs are known to follow_x000D_ several well defined period-luminosity (PL) relations at infrared wavelengths,_x000D_ representing promising distance indicators, especially in the case of the_x000D_ bright, large-amplitude Mira variables. In order to fully exploit the potential_x000D_ of LPVs in the study of stellar evolution and stellar populations, it is necessary_x000D_ to understand and characterise their observed variability features, both in relation_x000D_ to their photometric properties and the predictions from evolutionary_x000D_ and pulsation models. Of crucial importance is the correct identification of the_x000D_ actual pulsation modes involved in the observed PL sequences, a long debated topic._x000D_ We present here a characterisation of the population of LPVs_x000D_ in the Magellanic Clouds. To do so, we make use of a large and improved_x000D_ grid of pulsation models, computed including updated opacity data for the_x000D_ specific composition of O- and C-rich stars. Pulsation models are combined with_x000D_ a population synthesis tool to simulate a population of evolved red giant variables._x000D_ Models are compared with observational data from the OGLE-III Catalogue of Variable_x000D_ Stars, allowing us to provide a consistent interpretation of the observed_x000D_ PL sequences. We discuss some of the possibilities related to the use of pulsation_x000D_ models and observed pulsation properties to assist the calibration of stellar_x000D_ evolutionary models. Some of the issues involved in the theoretical modelling_x000D_ of pulsation in evolved red giants are also discussed.
I,II,III,IV,V: Types of Historical Supernovae and what you, I, and LIGO might have seen
Trimble, Virginia
First the good news: The historical supernovae (of which there are 7-14) can tell us something about rates (small number statistics), types (no two are the same), parent populations, 3-D structures, what SNe put into the ISM, formation, initial rotation and magnetic fields, and early evolution of neutron stars, ditto for black holes, late mass loss from massive stars, nucleosynthesis, kick velocities, and whatever I've left out. Now for the bad news: CM Tau (SN 1054, NGC 1952, 3C144, Tau X-1, NP0532, etc.) has aged 5.6% since I and Jeff Scargle began looking at images of it for our Caltech PhD dissertations (with thanks to Walter Baade and Guido Munch). In the interim, its observed mass has fluctuated more than a factor two, it has added a pulsar (with rather slow initial rotation), a fairly useless jet off to one side (though everything else discovered by Sidney van den Bergh over the years has been highly useful), a gamma ray source, and many models of particle acceleration, of which at most one can be correct. And this is the historical SN about which we know most. The ensemble includes 1572 (Tycho), 1604 (Kepler), Cas A (not Flamsteed), SN 1006, the progentor of SNR 0519-76.5 (not Magellan), S And, RCW86 = SN 185, 1987A, etc. Eta Carinae was a Zwicky Type V and doesn't count. These suggest, first, that we are overdue for another Galactic event and, second, that successful clasification of events is considerably assissted by not knowing too much about them. The Crab Nebula was also the first identified remnant of an event that had been recorded when it occurred (credit Lundmark and assorted anonymous Chinese sky-watchers). The identification was, of course, then disputed, until many astronomers had written either that they had always known about it, or that it wasn't very important, or that they thought of it first."
International astronomical cooperation before the IAU
Trimble, Virginia
We could start with "Greeks" in Egypt and Turkey or "Arabs" from India to Spain, but "international" in the sciences and other fields really took off in the long 19th century, with literally hundreds of meetings in Paris, London, Brussels and elsewhere, including the establishment of the Association International des Academies in Wiesbaden in 1899 (22 members by 1914). Astronomy had seen von Zach's celestial police (1800-01); Schumacher's offer to take input for his Astron. Nach. (founded 1821) in any major European language; the Astronomische Gesellschaft (est. 1843 with board members and meeting sites from much of Europe) involving 4 American and 4 other non-German observatories in AGK (1861), setting up the Central Bureau for Astronomical Telegrams (1884) and coordinating variable star research (from 1901); Kuiper's Selected Areas (1906); and Carte du Ciel, begun in 1887 with no US participation and declared complete in 1964._x000D_ Some exchange of information continued through WWI (often through neutral Holland and Denmark), so you can find German variable star data in Nature, an obituary of Moseley in Naturwiss. and Einstein's GR papers 1915-16 reaching de Sitter and on to Eddington. In stark contrast, Transit of Venus (1874, 82) and eclipse (1860 ff) expeditions were nearly all every country for itself, often even every observatory for itself. This changed rather little in the 20th century, and the Eclipse WG of Comm. 12 had remarkably little to say in 1970. By 2003 the WG dealt primarily with education and governmental approval issues. Equipment lost when Freundlich's 1914 Crimean expedition was captured came home in 1923; and there is a Peking 1900-19 story I still want to hear the end of.
Origin and recovery from grand solar minima in a time delay dynamo model with magnetic noise as an additional poloidal source
Tripathi, Bindesh
We explore a reduced Babcock-Leighton (BL) dynamo model based on delay differential equations using numerical bifurcation analysis. This model reveals hysteresis, seen in the recent mean-field dynamo model and the direct numerical simulations of turbulent dynamos. The BL model with 'magnetic noise' as an additional weak-source of the poloidal field recovers the solar cycle every time from grand minima, which BL source alone cannot do. The noise-incorporated model exhibits a bimodal distribution of toroidal field energy confirming two modes of solar activity. It also shows intermittency and reproduces phase space collapse, an experimental signature of the Maunder Minimum. The occurrence statistics of grand minima in our model agree reasonably well with the observed statistics in the reconstructed sunspot number. Finally, we demonstrate that the level of magnetic noise controls the duration of grand minima and even has a handle over its waiting period, suggesting a triggering effect of grand minima by the noise and thus shutting down the global dynamo. Therefore, we conclude that the 'magnetic noise' due to small-scale turbulent dynamo action (or other sources) plays a vital role even in Babcock-Leighton dynamo models. Thus a serious concern should be given to understand the small-scale turbulent dynamo action, which can help us in predicting the Maunder minimum-like episodes and especially in determining such episodes' duration, along with having an understanding of the associated changes in the solar irradiance.
The impact of non-ideal effects on the circumstellar disk evolution and their observational signitures
Tsukamoto, Yusuke
In this talk, we discuss the impact of non-ideal effects on the ciucumstellar disk formation, and the observational signatures created by them.It has been recognized that non-ideal MHD effects (Ohmic diffusion, Hall effect, ambipolar diffusion) play crucial roles for the circumstellar disk formation and evolution. the Hall effect notably changes the magnetic torques in the envelope around the disk, and strengthens or weakens the magnetic braking depending on the relative orientation of magnetic field and angular momentum (Tsukamoto+15b, Tsukamoto+17). This suggests that the bimodal evolution of the disk size occurs in the early disk evolutionary phase, which is suggested by the recent disk observation of Class 0 YSOs (e.g., Yen+17). Ohmic and ambipolar diffusion decouple the gas and the magnetic field, and significantly reduces the magnetic torque in the disk, which enables the formation of the circumstellar disk. They set an upper limit to the magnetic field strength of ~ 0.1 G around the disk.Hall effect and ambipolar diffusion imprint the observable characteristic velocity structures in the envelope of Class 0/I YSOs. Hall effect forms a counter-rotating envelope around the disk. Our simulations show that counter rotating envelope has the size of 100-1000 AU and several recent ALMA observations actually infers such structures. Ambipolar diffusion causes the significant ion-neutral drift in the envelopes. Our simulations show that the drift velocity of ion could become 100-1000 m/s and it would be observable by ALMA.
The Habitability of Exomoons
Tylor, Christopher
In recent years, astrobiologists have begun to seriously consider the possibility that suitable conditions for life to develop might be found on planetary satellites, as well as on planets themselves. For this reason, the moons of planets around other stars (exomoons) provide a fascinating route by which astrobiological studies can move beyond the search for habitable-zone planets. Habitability fundamentally depends on the reliability of the energy supply (astrophysical, geophysical or geochemical) for life, and the local environment. The icy moons of the outer Solar System already provide targets for the search for subsurface oceanic life. Given that such satellites rely on tidal heating to provide a stable environment for life, a key factor in Exo-Moon habitability would be the long-term orbital stability of a given moon around the host exoplanet. In this project, the long-term orbital stability of the Jovian moons is explored using numerical modelling with the REBOUND N-body integrator code to assess the potential for significant orbital changes on timescales of tens to hundreds of millions of years. The results to date indicate that the Jovian satellite system is characterised by an extremely stable orbital configuration, and hence provides a thermally stable environment to within one part in 100,000 in energy input into any subsurface oceans present over timescales of at least tens of millions of years. As a result, those moons could provide a stable environment for life to develop and survive. These results can be used to speculate that a range of stable Exo-Moon orbital configuration and environments could exist that expand the potential number of habitable worlds well beyond the estimates made on the basis of classical habitable-zone exoplanets alone.
Welcome – Div.B
Ubertini, Pietro
Welcome words by Pietro Ubertini
Report from Division President-VP
Ubertini, Pietro
Report from Division President-VP: Pietro Ubertini and Michael Burton
ALMA deep survey in a z=3.1 proto-cluster field
Umehata, Hideki
Galaxies and nuclei in the dense environment at high redshift provide a good laboratory to investigate the accelerated, most extreme evolution of galaxies at a given epoch. A 50 Mpc-scale filamentary three-dimensional structure (or large-scale ‘cosmic web’) traced by Lyman-alpha emitters (LAEs) has been found in the SSA22 field at z=3.1, which is one of the best target in this regard. We mapped a contiguous 7 arcmin^2 and 20 arcmin^2 regions at the node in ALMA band 3 and band 6, respectively, to uncover molecular gas reservoirs and dusty starburst cores at the proto-cluster core. We obtained 35 robustly detected 1.1mm sources (here after submillimeter galaxies, SMGs) with a signal-to-noise ratio (SNR) >5. More than half of the SMGs have been spectroscopically confirmed to be a genuine proto-cluster member. IR and CO luminosity functions are 2-3 orders of magnitudes higher than blank fields. Six SMGs at the core also host a X-ray luminous active galactic nuclei (AGN). Our results suggest that the vigorous star formation activity and the growth of super massive black holes (SMBHs) occurred simultaneously in the densest regions at z~3 supported by abundant gas fueling, which is likely to correspond to the most active historical phase of the massive galaxy population found in the core of the clusters in the present universe.
Star-forming dwarf field galaxies found in the MUSE-Wide survey
Urrutia, Tanya
The exquisite depth of the HST deep fields allow us, in principle, to find dwarf field galaxies to study their evolution through cosmic time. However, a severe bottleneck is the inefficiency of spectroscopic surveys to identify and classify these usually faint systems. Here we present the MUSE-Wide survey, a full 3d spectroscopic survey covering 100 arcmin2 fields over the CANDELS-DEEP/GOODS-S and CANDELS-COSMOS regions. Through their emission lines we were able to find very low stellar mass, star-forming galaxies both at high and low redshift. Approximately 60 systems at z < 1 with log(M*) < 7.5 log(Msun) and another 60 at z > 2.8 with log(M*) < 8.0 log(Msun) found through their Lyman Alpha emission. For the systems at low redshift we will present the Mass-Star-Formation and Mass-Metallicity relations and their deviations from cluster, low star formation dwarf galaxies. In particular, we will present extreme O32-emitters, thought to be responsible for strong Lyman continuum leakage. At high redshift we will present the Lyman-Alpha luminosity function and cases of extreme equivalent width emission, both of which are important for pinning down the numbers and strength of dwarf galaxies contributing to the reionization of the Universe.
Techniques and algorithmic advances in the SKA era
Vacca, Valentina
One of the key science goals of the new generation of radio telescopes is to shed light on the origin and evolution of cosmological magnetic fields. Magnetic fields presently observed in the Universe are thought to be the result of a pre-existing seed magnetic field amplified during processes of structure formation. According to the proposed scenarios, the seed magnetic field either has a primordial origin or is generated later, in stars and/or pro-galaxies, and then injected in the surrounding medium by galactic winds and/or outflow. The overall picture is not yet clear since our knowledge of magnetic fields in the large scale structure of the Universe is poor. Magnetic fields have been observed up to galaxy clusters scales, where a detailed investigation is limited only to a few systems. Magneto-hydro-dynamical simulations indicate their presence even beyond galaxy cluster, but a firm observational evidence is still missing._x000D_ A better understanding of magnetic fields in galaxy clusters and their discovery and investigation on larger scales, i.e., along the filaments and the voids of the cosmic web, would permit to put valuable constraints on the magnetic field origin and to investigate mechanism of amplification to the strengths presently observed. Magnetic fields in galaxy clusters and in the large-scale structure of the Universe can be studied in high detail by means of radio observations in total intensity and polarization of diffuse and extended synchrotron sources and of the Faraday effect on background radio galaxies. Because of their weakness, the study of these magnetic fields is extremely challenging and requires high quality observations and advanced techniques of analysis. During this talk, I will give an overview on the innovative approaches developed in the last years to investigate magnetic fields in the large-scale structure of the Universe.
Galactic Bulge
Valenti, E.
TBA
Revisiting young alpha-enhanced stars in CoRoT center and anti-center fields
Valentini, Marica
In 2015 two studies pointed out for the first time the existence of a young stellar population enriched in alpha-elements (Chiappini et al. 2015 and Martig et al 2015). By combining asteroseismology and spectroscopy, it was possible to derive masses, and hence ages, of a big sample of red giants observed by Kepler and CoRoT satellites and belonging to the APOGEE spectroscopic survey. Among this sample, a group of stars standed out, being massive, and hence young, but possessing an alpha-enrichment tipical of older populations. Two scenarios have been proposed for explaining this objects: a. they are blue-stragglers, stars that rejuvenated via mass accretion from a companion; b. these objects formed close to the end of the Galactic bar, near corotation, a region where gas might have been kept inert for longer times than in other regions.In this work we consider stars belonging to CoRoT fields LRc01 and LRa01, the former pointing at the inner part of the Galaxy and the latter pointing at the opposite region. The sample is located in the Galactic disc and spans distances from 4 Kpc to 12 Kpc from the Galactic centre. Stars were observed by APOGEE and Gaia-ESO surveys, and have precise atmospheric parameters and chemical abundances.We derived masses and ages of the stars using an updated version of the Bayesian code used in Chiappini et al. 2015. We also investigated the impact in the age and mass determination of temperature/metallicity shifts, different mass-loss approaches, alpha-enrichment and corrections on the seismic scaling relations. Even with this new approach, and using data coming from two different surveys, we identified a population of young alpha-enhanced stars.
The biological impact of superflares on a planet in the Habitable Zone
Valio, Adriana
Kepler-96 is a very active star, with many superflares seen on its lightcurve. This star harbours a Super-Earth planet orbiting very close to the star. With an age of 2.4 Gyr, this star is at the same stage of the Sun when the first multicelular organisms appeared on Earth. Here we analyse the four years of continuous short cadence observation of the star by the Kepler telescope. The model used simulates a planetary transit in front of a star with a disk flare of different size, amplitude, and position. By fitting the observational data with this model, it is possible to infer the physical properties of the flares, such as duration (few minutes) and energy released by each flare. The biggest flare observed was found to have an energy of 1.8 10^{35} ergs, that corresponds to the energy range of the superflares found in literature. In addition, we analyze the biological impact of these superflares on a hypothetical Earth with various atmospheres scenarios: an Archean atmosphere and Present-day atmospheres with and without oxygen. The presence of an ocean was also included in our study. We estimated the UV flux produced by the superflare and concluded that life would only survive on the surface of Kepler-96b if there were already an ozone layer present on the planet atmosphere, or in an ocean of a few meters deep.
Gaia Second Data Release Early Science
Vallenari, Antonella
In this presentation we review the main scientific results based on Gaia Second Data Release
The MESSIER project, unveiling galaxy formation.
Valls-Galbaud,
The MESSIER surveyor is a small mission designed at exploring the very low surface brightness universe. The satellite will drift-scan the entire sky in 6 filters covering the 200-1000 nm range, reaching unprecedented surface brightness levels of 34 and 37 mag arcsec-2 in the optical and UV, respectively. These levels are required to achieve the two main science goals of the mission: to critically test the ΛCDM paradigm of structure formation through (1) the detection and characterisation of ultra-faint dwarf galaxies, which are predicted to be extremely abundant around normal galaxies, but which remain elusive; and (2) tracing the cosmic web, which feeds dark matter and baryons into galactic haloes, and which may contain the reservoir of missing baryons at low redshifts. A large number of science cases, ranging from stellar mass loss episodes to intracluster light through fluctuations in the cosmological UV-optical background radiation are free by-products of the full-sky maps produced.
Plenary Session: High-Mass X-ray Binaries
van den Heuvel, Edward
A brief historical overview is given of the discovery of the different classes of High-Mass X-ray Binaries (HMXBs), and of the models for their evolutionary origins and fate. Already in the early 1970s it was expected that HMXBs will terminate their evolution as very close systems or will merge. This picture was confirmed by the 1974 discovery of the first close double neutron star system, showing that HMXBs which do not merge will terminate as close systems consisting of two compact objects.HMXBs are crucial astrophysical objects in many respects:As key probes of accretion processes, by stellar wind and Roche-lobe overflow or a combination of these.As probes of the winds of massive stars and of transient mass ejections of B-emission stars.As probes of interactions between matter flows and the magnetospheres of neutron stars, causing spin-down and spin-up.As probes of black-hole accretion and the formation of relativistic jets.As probes of the evolution of massive binary systems, leading to the formation of double neutron stars and black holes, and neutron star-black hole binaries.The present state of our knowledge and ignorance in these subjects is reviewed.
The IAU and Hazardous Near-Earth Objects - a clear and present danger
van der Hucht, Karel A.
The IAU Minor Planet Center was established in 1947 and has been active ever since. Since 1989, daily CCD surveys of Near Earth Objects at ground-based astronomical observatories are operational, notably in the USA. Presently some 18,000 Near Earth Asteroids (NEAs) and 107 Near Earth Comets (NECs) are registered and made public on the internet by the MPC, NASA-JPL and ESA-SSA-NEOCC.Concern for impacts of NEOs has been picked-up in 1999 by the United Nations Committee on the Peaceful Uses of Outer Space (UN-COPUOS), where the IAU has observer status.In support of these efforts, the IAU 28th GA in Beijing adopted on 30 August 2012 a Resolution (3B), recommending the establishment of a NEO International Early Warning System, as proposed by the IAU Division III Working Group on Near-Earth Objects.The issue received world-wide attention by the impact on 13 February 2013 over Chelyabinsk (Russia) of a NEA with an estimated size of 17 to 20 meters and an estimated mass of 11,000 tons, releasing an energy of 440 kT TNT at an altitude of ~23 km.Since then, the United Nations General Assembly adopted on 5 December 2014 a Resolution (69/85, 9-10), noting: "… the importance of information-sharing in discovering, monitoring and physically characterizing potentially hazardous near-Earth objects ... ."As of today, while the estimated number of NEAs larger than 40 meter in diameter is about 300,000, only some 14,000 (~ 5 %) have been detected to date. For NEAs with sizes between 40 and 140 meter, the detection percentage amounts to less than 2 % of the estimated number. Only space-based observatories, like the since 2011 planned NASA-JPL NEOCam mission, an infrared observatory dedicated to operate in Lagrange point L1, will be able to provide an order of magnitude increase of the detection and characterization of Near Earth Objects. We better find them before they find us.
JWST science prospects: a pre-launch taste
van Dishoeck, Ewine
JWST promises to examine every phase of cosmic history: from the epoch of re-ionization after the Big Bang to the formation of galaxies, stars, and planets, the atmospheres of exoplanets and the evolution of our own solar system. Its leap in sensitivity, angular resolution and broad wavelength coverage from optical to mid-infrared compared with other missions will ensure major steps forward in many areas. Here a brief "taste" of future JWST science will be presented, by highlighting a number of specific examples from each of the science areas. Synergies with other major facilities will be emphasized.
The IAU 2020-2030 Strategic Plan: OAD
van Dishoeck, Ewine
The mission of the IAU is to promote and safeguard astronomy in all its aspects (including research, communication, education and development) through international cooperation. Over the past year, the new strategic plan for the IAU has been put together, providing an overview of all IAU activities and formulating a number of long-term goals and actions. Input from the OAD, OAO and OYA/ISYA, along with the Executive Committee and Division Presidents, as well as from the IAU membership as a whole, has been solicited. The new plan builds on the impressive 2010-2020 plan which describes primarily the then to-be-initiated OAD.Here a brief overview of the new Strategic Plan will be presented with a focus on how the OAD has become a central element of future IAU activities.
The IAU 2020-2030 Strategic Plan: OAD
van Dishoeck, Ewine
The mission of the IAU is to promote and safeguard astronomy in all its aspects (including research, communication, education and development) through international cooperation. Over the past year, the new strategic plan for the IAU has been put together, providing an overview of all IAU activities and formulating a number of long-term goals and actions. Input from the OAD, OAO and OYA/ISYA, along with the Executive Committee and Division Presidents, as well as from the IAU membership as a whole, has been solicited. The new plan builds on the impressive 2010-2020 plan which describes primarily the then to-be-initiated OAD.Here a brief overview of the new Strategic Plan will be presented with a focus on how the OAD has become a central element of future IAU activities.
The next hundred years of the IAU
van Dishoeck, Ewine
The first hundred years of the IAU have witnessed scientific and technological progress in astronomy beyond anything imagined at the time the IAU was constituted in 1919. What will the next hundred years bring? How do we engage with other sciences, now that our field is becoming more multidisciplinary? How do we convince governments to continue funding our field, in particular the ever more powerful telescopes? And how do we inspire and involve people worldwide, from young to old, in our exciting adventure through space? The IAU 2020-2030 Strategic Plan provides a forward look for the next decade, with specific actions and goals to further the mission of the IAU, which is to promote and safeguard astronomy in all its aspects (including research, communication, education and development) through international cooperation. A brief forward look into the next decadeand beyond will be presented.
Maser stars tracing the Milky Way
van Langevelde, Huib
Astrometric studies of Galactic radio sources using VLBI provide unique measurements of the Galactic distribution of both very young and evolved stars. Because radio observations are not affected by interstellar extinction, such measurements complement the results tat are obtained by Gaia. In this presentation the synergies are explored between VLBI and Gaia to study stellar populations in the Milky Way. For example we use te new Gaia output to find optical cluster companions to high mass star forming regions that harbour methanol and water masers. But we also use Gaia to characterise the AGB star population that we defined in te infrared. Using the SiO masers emission of these stars will allow for a study of the dynamics in the inner Galaxy.
The solar observations during the Maunder minimum: recent advances
Vaquero, José Manuel
John A. Eddy named the Maunder minimum (a period of very low solar activity around the second part of the 17th century) more than forty years ago. However, the exact level of solar activity during this grand minimum of solar activity remains unclear (although several studies have confirmed a low level of solar activity proposed by Eddy). In the last years, some authors have speculated with different scenarios for the Maunder minimum. In this work, we propose to re-analyze the sunspot observations recorded during the MM, also taking into account the knowledge of historians of science and linguists. We must avoid speculations not based on contrasted facts. The sunspot observations made by Hevelius in the onset of the Maunder minimum will be revisited. Also, some sunspot drawings made during the Maunder minimum have been analyzed in detail (computing the ratio umbra-penumbra). Finally, some considerations about the measurements of the solar radius made during the Maunder Minimum will be stablished revisiting the measurements made in the Basilica of San Petronio in Bologna.
A mid-infrared interferometric survey of the planet-forming region around young Sun-like stars
Varga, Jozsef
The 0.5-10 au region of the dense circumstellar disks around the few million years old T Tauri stars is the cradle where planets similar to the Earth and her rocky planet sisters were formed. The small size of the region makes it challenging to obtain spatially resolved information about the physical, chemical and mineralogical conditions in the inner disk area. Mid-infrared interferometry is the only tool to do that, thus star formation was one of the main driving science case behind the 13-years mission of the MIDI interferometer at ESO's Paranal Observatory. When dismounted in 2015, MIDI left behind a rich archive of young stellar object observations. Motivated by the opportunity, our group recently carried out a homogeneous data processing and analysis of 82 low- and intermediate-mass young stellar objects. From a simple geometric disk modeling we typically found continuous disk geometries, but in a few objects a model with an inner gap with radii ranging from 0.5 to 10 au gave a better match. The mid-infrared size of the disks scales with the stellar luminosity, although the correlation is much weaker than in the near-infrared. This suggests that the 1-10 au disk region has more diverse structure than the inner 1 au region. Once we account for differences in stellar luminosity, the disks around Sun-like stars are generally colder and more extended, than disks around intermediate-mass stars. The interferometric measurements on the profile and amplitude of the 10 micrometer silicate spectral feature revealed that the dust in the inner disk is more processed (coagulated, crystallized). T Tauri stars typically show weaker silicate emission than Herbig Ae stars, which may indicate that the disk flaring is less pronounced. Our atlas made possible the so-far most complete spatially resolved statistical study of the terrestrial planet forming zone around young Sun-like stars, and the results will provide valuable input for future instruments like VLTI/MATISSE or JWST.
Pro-am collaboration in Occitanie, outreach and consequences
Vauclair, Sylvie
The collaboration between professional astrophysicists and amateur astronomers have always been very active in France, and particularly in the south-west region which is now called "Occitanie". Since the International Year of Astronomy in 2009, where I was in charge of the events in the whole region, new associations have been created, with specific actions towards society, economy, ecology, etc. in connection with the observations of the night sky. I will present several achievements and on-going projects, like the solar observations at Pic du Midi Observatory, done by amateurs with a professional aim, the help of amateurs for professional observations with the 2m telescope, the important labelled dark sky region "RICE" which concerns more than 250 towns and villages, all implied for a better sky visibility, etc. I will present these topics and also discuss them in the framework of the large philosophical question "Humanity facing the Universe".
K-CLASH: The field and cluster environment at the epoch of the build-up of the red sequence
Vaughan, Sam
Integral Field Spectroscopy (IFS) surveys are opening new windows on the nature of galaxies at z ~1—2 (e.g. KROSS, the KMOS Cluster Survey, and KMOS3D) and in the local Universe (e.g. MaNGA, SAMI, CALIFA, ATLAS3D), comparing the spatially-resolved, rest-frame optical properties of star forming galaxies at each epoch. They reveal a stark difference between galaxies 10 Gyr ago at the peak of cosmic star formation rate density that tend to be turbulent, highly star-forming gaseous disks, and the comparatively quiescent, ordered spirals we see in the local Universe. Further, in clusters, over the same period we witness a build-up of the “red sequence” of galaxies, with the fraction of S0 galaxies increasing. But whilst comparisons between these two extremes have revealed much about the nature and evolution of galaxies, there is an absence of equivalent studies at intermediate times. It is therefore not clear which processes are driving the changes we see between galaxies in the distant past and the present day, nor at what point these changes occurred. The K-CLASH survey is bridging this gap by using the K-band Multi-Object Spectrograph on the VLT to study the spatially resolved gas kinematics and chemistry of galaxies in 4 CLASH clusters (Postman+12) at 0.4 < z < 0.6, and in field galaxies along the same lines of sight. In combination with thousands of pre-existing IFS observations of galaxies at z ~ 1—2 and at z ~ 0, K-CLASH will allow us to determine the the role of environment in the build-up of the red sequence and the formation of fast-rotator, early-type galaxies, as well as catching the galaxy population in transition from turbulent, highly star-forming disks to the familiar late-type galaxies we observe today. I will describe the K-CLASH survey and highlight some key early science results, including measurements of their ionised gas kinematics, and finish with a discussion of what we may learn about the evolution of galaxies over time in either environment.
The role of AGB stars in the evolution of Globular Clusters
Ventura, Paolo
It is now generally accepted that Globular Clusters harbour at least two groups of stars, differing in the chemical composition, particularly in the relative distribution of the species lighter than silicon. Because these chemical differences are not detected in field stars, these results indicate a self-enrichment mechanism, active in Globular Clusters. The search for possible polluters of the intracluster medium has stimulated a lively, still in progress debate. In this contribution I will discuss the various scenarios so far proposed and focus on the possibile role of massive AGB stars in the production of the nuclearly processed gas, from which the stars with the anomalous chemical composition might have formed.
Evaluating Astronomy interventions: A Pilot Project to Evaluate the Effect of the ‘Pale Blue Dot’ Hypothesis
Venugopal, Ramasamy
Astronomy and Space topics are perceived as holding universal fascination. It is widely considered that exposure to such topics inspires people, changes their perspective and leads to an uptake in science and STEM subjects. Stargazing parties, public astronomy talks and other astronomy/space events constitute some of the most common, public, scicomm events around the world. Astronomy communicators and astronomers frequently engage with children and the general public to teach, demonstrate, and talk about Astronomy. But very rarely is the impact of such communication evaluated rigorously and scientifically. There is a need for more rigorous evaluation methods which would reveal the successes and failures of current methods and tools of astronomy communication and whether they might lead to any inadvertent harm.In this presentation, we will share our team's implementation of a pilot Randomized Controlled Trial carried out in Cape Town, South Africa to test whether exposure to an astronomy intervention affects empathy and altruism in children (that is, whether astronomy induces a perspective of 'One Global Humanity', espoused by Carl Sagan and often quoted by astronomy communicators). The pilot demonstrated that it is possible to use such methods to evaluate impact of science communication in an inexpensive manner.
On the factors determining the eruptive character of solar flares
Veronig, Astrid
We study how the magnetic field determines whether a strong flare launched from an active region (AR) will be eruptive or confined, i.e. associated with a coronal mass ejection (CME) or not. To this aim, we analyzed 44 flares of GOES class >M5.0 that occurred during 2011 to 2015 in SDO data. We used 3D potential magnetic field models to study their location within the host AR (using the flare distance from the flux-weighted AR center, d_FC) and the strength of the overlying coronal field (via decay index n). We also present a first systematic study of the orientation of the coronal magnetic field changing with height, using the orientation phi of the flare-relevant polarity inversion line as a measure. We analyzed all quantities with respect to the size of the underlying active-region dipole field, defined by the distance between the flux-weighted opposite-polarity centers, d_PC. We find that flares originating from the periphery of an AR dipole field (d_FC / d_PC > 0.5) are predominantly eruptive. Flares originating from underneath the AR dipole field (d_FC / d_PC < 0.5) tend to be eruptive when they are launched from a compact AR and confined when launched from an extended AR (d_PC > 60 Mm). In confined events, the flare-relevant field adjusts its orientation quickly to that of the underlying dipole field with height (delta phi > 40° between the surface and the apex of the active-region dipole field), in contrast to eruptive events where it changes more slowly. The critical height for torus instability discriminates best between confined (h_crit > 40 Mm) and eruptive flares (h_crit < 40 Mm). It discriminates better than delta phi, implying that the decay of the confining field plays a stronger role in the eruptive/confined character of a flare than its orientation at different heights.
Chemical Evolution of the Milky Way Disk: Insights from the TGAS-RAVE-LAMOST Dataset
Vickers, John J
We study the enrichment of 125,000 stars in a spectroscopic-photometric dataset (TGAS, LAMOST, RAVE) as a function of their dynamics and inferred ages. The dynamics can be used to estimate birth radii (if heating is the main influence, and not large-scale migration), which, when coupled with age and abundance information, can describe the enrichment rates at different radii in the disk. Using such an analysis, we find that, while the disk interior to the Sun enriched first, the outer disk is currently enriching more quickly. By considering the enrichment profile of the Milky Way ISM along with the dynamics of stars, we can select a small sample which are more metal rich than the ISM at their current orbital radii, this is indicative of these objects having migrated from interior regions of the galaxy. Adding in our age information, we find these objects to be disproportionately young, which is consistent with the idea of potential-driven migration primarily affecting dynamically cooler (younger) populations.
Revealing the Invisible Drivers of Galaxy and Structure Formation with Lynx
Vikhlinin, Alexey
The assembly, growth, and state of visible matter in cosmic structures are largely driven by violent processes that produce and disperse large amounts of energy and metals into the surrounding medium. In galaxies at least as massive as the Milky Way, the relevant baryonic component is heated and ionized to X-ray temperatures. Lynx will be capable of mapping this hot gas around galaxies and in the Cosmic Web, as well as characterizing in detail all significant modes of energy feedback. Essential observations will require high-resolution spectroscopy (R _x0002_~5000) of background AGNs, the ability to detect low surface brightness continuum emission, and R~2000 spectroscopy of extended sources on arcsecond scales — all unique to Lynx.
Radial elemental abundance gradients in galaxies from cosmological chemodynamical simulations
Vincenzo, Fiorenzo
Radial chemical abundance gradients in galaxies can retain fundamental information about the galaxy growth as a function of time, as well as about the interaction of the galaxy with its surrounding environment. Cosmological chemodynamical simulations can be very useful tools in this respect, because the effects of inside-out growth, stellar migrations, and galaxy mergers can be, in principle, disentangled. In the first part, I will present the results of our study for a sample of star forming galaxies with different star formation histories in our cosmological chemodynamical simulation. We can reproduce with our simulation the global observed mass-metallicity relation, the observed cosmic star formation rate, and the N/O versus O/H chemical abundance pattern as observed in nearby galaxies. I will show our predictions for the redshift evolution of the radial chemical abundance gradients both in the gas and in the stellar populations of our simulated galaxies. In the second part, I will show results from zoom-in chemodynamical simulations, where a target galaxy is selected at low redshift from a full cosmological simulation and then re-simulated with a larger number of resolution elements, starting from the initial conditions of the early Universe.
On the origin of N in galaxies with galaxy evolution models
Vincenzo, Fiorenzo
Nitrogen is among the most abundant chemical elements in the cosmos and AGB stars are fundamental nucleosynthetic sources of this chemical element in galaxies. In my talk, I will show how the observed N/O versus O/H abundance pattern, both in extragalactic systems and in our own Galaxy, can be used to constrain the nucleosynthetic origin of N in the cosmos. The redshift evolution of chemical abundances in the ISM of galaxies can nowadays be studied both with "classical" chemical evolution models and with cosmological chemodynamical simulations; in my talk, I will review the results of my studies with both kind of galaxy evolution models focusing on the evolution of the N abundances in galaxies, by pointing out the most important critical issues in my studies.
Constraining the progenitor evolution of GW 150914
Vink, Jorick
One of the largest surprises from the LIGO results regarding the first gravitational wave detection was the fact the black holes were "heavy", of order 30 - 40 solar masses. The most promising explanation for this obesity is that the merger occurred at low metallicity: when the iron (Fe) contents is lower, this is expected to result in weaker mass loss & more rapid stellar rotation, allowing Wolf-Rayet and black hole progenitor evolution in a chemically homogeneous manner. However, there is as yet no empirical evidence for more rapid rotation amongst Wolf-Rayet stars. Due to the intrinsic challenge of determining the rotation rates of Wolf-Rayet stars from their emission lines, the most promising way to constrain rotation rate distributions amongst the various subgroups of Wolf-Rayet stars in various metallicity regimes is through the utilisation of their emission lines in polarised light. I will thus provide an overview of spectropolarimetry observations of both single star and binary Wolf-Rayet stars in the Galaxy, as well as the Large and Small Magellanic Clouds, at 1/2 and 1/5th solar metallicity, respectively. I will use these results to argue which evolutionary routes are most promising to produce heavy black holes.
Families among the Hildas and Trojans
Vinogradova, Tamara
A search for asteroid families among the Hildas and Trojans is especially difficult because these asteroids move in resonance zones. The Hildas are in the 3:2 and Trojans in the 1:1 mean motion resonances with Jupiter. In resonance regions the calculation of proper elements by analytical methods is complicated. Modern methods calculate proper elements in these zones by means of numerical integration on a very long time scale. On the other hand, there is fundamentally different approach to this problem. We propose the empirical method of proper elements calculation. The method uses distributions of osculating orbital elements, such as the longitude of ascending node - inclination and the longitude of perihelion - eccentricity. These distributions make it possible to obtain long-period perturbations of the inclination and eccentricity. A removal of the long-period terms was done using the coordinate transformation formula. The derived proper elements are accurate enough to search for asteroid families. The empirical method may be used in both non-resonant and resonant regions. It is an advantage of this method. Moreover the procedure of computing proper elements by the empirical method is not time-consuming. All available now multi-opposition asteroids were used for calculation. Increased number of faint asteroids enables us to get new reliable results in such complicated regions as the Hildas and Trojans. As a result two robust asteroid families of (1911) Schubart and (153) Hilda were identified in the Hilda-group. And four families were found among L4-trojans: (3548) Eurybates, (2148) Epeios, (624) Hektor, and (9799) 1996RJ.
Magnetic fields of AGB and post-AGB stars
Vlemmings, Wouter
I will review the current status of magnetic field observations around AGB and post-AGB stars. I will shortly describe their possible role during these stages of evolution and will focus on our attempts to determine the origin of the magnetic field. Specifically recent efforts include ALMA observations of the near-stellar environment showing the signatures of hotspots and rotation.
AstroAccess: Enhancing Disability Inclusion in Science through 3D Printing, Theatre, and Astronomy Outreach
Voelker, Anna
From an underrepresentation of scientists and astronomers with disabilities to a deficit of educational materials available for students with specialized needs, there is a plethora of accessibility issues in the world of astronomy and STEM as a whole. Breaking down these barriers starts with education. Learn about new and innovative ways to create educational opportunities that are accessible to people with disabilities and engaging for all learners. This session will get participants thinking, developing, collaborating, and engaging in approaches to accessible learning.I will share my work on 3D printing galaxies, a project lead by Carol Christian of the Space Telescope Science Institute. In order to make astronomy more inclusive of blind learners, scientific data from the Hubble Space Telescope is converted into 3D printed galaxies, some of which I will be bringing for the audience to feel first-hand. These tactile tools are valuable for anyone who wants to learn about galaxies, regardless of their vision status. I will also discuss the use of theatre outreach for teaching science concepts to children on the autism spectrum. These inclusive acting games are designed to foster life skills that can have the potential to be more challenging for children with developmental disabilities, while simultaneously teaching science in a new and engaging way.I am extremely passionate about making astronomy accessible to all people and I believe that more efforts need to be made in order to include people with disabilities in this field. People deserve to know that there is more than just room for them in science; there is a need for them. This talk will focus on the ways in which astronomers can communicate science more effectively and more inclusively, and by doing so welcome more people into exploration of our Universe.
IAU PhD Awardee
Voisin, -
TBA
The Star Formation History of the Galaxy from Gaia Astrometry of White Dwarfs
von Hippel, Ted
What is the star-formation history of the Milky Way? How old are Galactic halo and thick disk stars? Traditional age-dating of stars relies on clusters or the white dwarf luminosity function, both of which offer only a limited view of these stellar populations. We demonstrate that white dwarf stars with precision parallaxes offer a dramatic way forward. Specifically, we show how optical and near-IR photometry, Gaia astrometry, and a Bayesian modeling approach allows us to characterize multimodal solutions in the mass-age plane and frequently determine precise ages (within 2%-5%) for individual white dwarfs. These individual white dwarf ages are then pooled hierarchically to derive population age distributions.
Immersed in the Solar Wind: The New Era of Solar Physics Space Missions
Vourlidas, Angelos
Sunlight feeds life on Earth while the solar wind buffets our magnetosphere, sometimes violently. It is no surprise that solar variability is a primary societal concern and subject of intense scientific research. For decades, however, progress on understanding the Sun-Earth connection has been hampered by the 'disconnected' nature of the observations; remote sensing of the near-Sun corona, in-situ sampling at Earth. The evolution of the solar wind and its more energetic transients in the inner heliosphere was accessible only through modeling. While the STEREO mission made great strides since 2007, the mechanisms of the generation and early evolution of the solar wind still elude us. _x000D_ _x000D_ This is about to change thanks to an unprecedented space mission, the Parker Solar Probe (PSP) to be launched in late July 2018. The mission is designed to attack the solar wind problem head-on by direct sampling of the corona from the ‘inside’ with a suite of remote sensing and in-situ instruments._x000D_ _x000D_ In this talk, I introduce the capabilities and science objectives of the PSP mission and discuss the exciting science prospects in solar physics research in the next 10 years. PSP will be the first spacecraft to enter the atmosphere of a star, reaching within 6 million km from the solar surface. The mission design will tie together in-situ sampling and high contrast imaging from ‘within’ the solar corona with high resolution observations from space and ground. A new era in solar and space physics awaits us.
Reconstructing the geomagnetic field from historical aurorae
Wagner, Daniel
For studying secular variations of solar activity over centuries fromthe satellite to the pre-telescopic era, homegeneous time series areneeded. Observations of aurorae as solar wind proxy could provide acontinuous time series overlapping with various discontinuities anderas. While aurorae were documented all over the world for the lastfew centuries, a critically checked and homogeneous dataset is notavailable. Here, we have started new initiatives to compile suchdatasets (we have obtained experience with historically observedaurorae from the pre-telescopic era). It is well-known that auroraetrace solar wind and, hence, are correlated to geomagnetic indices(e.g. aa-index measured since 1868); a full understanding of theconnection between auroral displays, observed from the ground by thenaked eye, and, e.g., the aa-index is still missing.Therefore, we investigated the size of the auroral oval as well as its offset fromthe geomagnetic pole for different magnetic activity levels describedby the Kp-index during solar maximum and minimum. We used imaging datafrom 1981 to 1991 from the Spin-Axis Auroral Imager mounted on theDynamics Explorer 1 satellite. We found a linear dependence betweenthe Kp-index and the oval radius and a nearly constant shift of theoval center towards the midnight sector of around 4.5 degrees.Currently, we derive the aurora oval size and radius from ground-basedaurora observations of the last few decades to compare them withsatellite data of the oval. Next, we plan to derive the geomagneticfield (strength and location of poles) from historical aurorae of thelast two centuries to compare with direct measurements of the magneticfield; if this would work, we can apply the same technique to previouscenturies to obtain an independent reconstruction.
The Pan-STARRS search for Near-Earth Objects
Wainscoat, Richard
Pan-STARRS consists of two 1.8-meter wide-field telescopes located near the summit of Haleakala, Maui, Hawaii. Each is equipped with a very large (1.4 Gigapixel) CCD camera that imnages an area of 7 square degrees on the sky. The first telescope, Pan-STARRS1, initially conducted a multi-pupose multi-color survey of the sky north of declination -30 degrees, and since then has been conducting a search for near-Earth objects. The second telescope, Pan-STARRS2, is presently being commissioned, and will double the survey power when it comes into regular operation during 2018. Pan-STARRS1 is the leading discovery telescope for near-Earth objects, and is also a prolific comet discovery telescope. It has recently been responsible for the discovery of approximately 50% of all new comets.In October 2017, Pan-STARRS1 discovered the first interstellar object, `Oumuamua. Interstellar objects were expected to be cometary in nature. Instead, `Oumuamua is asteroidal in appearance, and has other unusual properties. This important discovery has opened an entriely new field of research. Its discovery underscores the need to find additional similar objects so that we can study them in more detail in order to better understand their origin. In fact, large surveys may have seen multiple interstaller objects in the past, but they escaped discovery due to their fast motion.The Pan-STARRS survey for near-Earth objects will be described in detail, and compared to other surveys. Pan-STARRS is efficient at discovery of larger, more distant near-Earth objects, but is inefficient at discovery of smaller faster moving objects due to the characteristics of the CCD detectors.The inventory of even the largest near-Earth objects (diameter > 1 km) is still incomplete, and surveys such as Pan-STARRS will need to continue for many years in order for us to start to complete our inventory of large (and potentially dangerous) near-Earth objects.
Optical Interferometry of HMXBs: Resolving Wind, Disk and Jet Ouflows at Sub-milliarcsecond Scale
Waisberg, Idel
Because of their small angular size < few mas, spatial information on High-mass X-ray binaries (HMXB) has typically been inferred from photometry or spectroscopy. Optical interferometry offers the possibility to spatially resolve such systems, but has been traditionally limited to bright targets or low spectral resolution. The VLTI instrument GRAVITY, working in the near-infrared K band, achieves unprecedented precision in differential interferometric quantities at high spectral resolution, allowing to study many HMXBs through the lens of optical interferometry for the first time. Here we will present GRAVITY observations on two X-ray binaries: the microquasar SS 433 and the supergiant HMXB BP Cru. The former is the only known super-Eddington accretor in the Galaxy in a unique stage of binary evolution, with probable ties to at least part of the ULX population. With GRAVITY, we resolve its massive winds and optical baryonic jets for the first time, finding evidence for both a circumbinary disk and polar outflow and characterizing the activity of the central jet in both space and time. BP Cru harbors an X-ray pulsar accreting from the wind of its early-blue hypergiant companion Wray 977. By comparing the properties of its spatially resolved wind to those of isolated blue hypergiants zeta1 Sco and HD 169454, also observed with GRAVITY, we characterize the influence of the pulsar on the wind of Wray 977. We also compare our observations to predictions from stellar atmosphere models, highlighting the potential of optical interferometry to study winds of massive stars in general.
Asteroseismic constraints on stellar opacities
Walczak, Przemyslaw
One of the most interesting and still unresolved puzzle of the massive star interiors is the shape of the opacity profile. The opacity coefficient determines the energy transport and influences pulsational properties. Due to the latter we can use asteroseismic observables as diagnostic tools for the opacity inference.The excellent targets for such an analysis are the hybrid pulsators of ß Cep/SPB typewhich pulsate in both pressure (p) and gravity (g) modes. The simultaneous excitation of p and g modes offersprobing stellar regions sensitive to various physical processes. A lot of new members of this group were discovered thanks to space-borne observations from the projects like CoRoT, Kepler and BRITE.We show that models computed with widely-used opacity data (OPAL, OP, OPLIB) cannot explain the pulsations of these stars, in particular the instability of high-order g modes. Applying the complex seismic modelling to a few hybrid pulsators, we found that a significant modification of the mean opacity profile is indispensable to explain all pulsational properties.
Report for the Inter-Commission B7-C1 WG Achieving Sustainable Development within a Quality Lighting Framework
Walker, Constance
“Achieving sustainable development within a quality lighting framework” is a joint Working Group of the IAU C.B7 & C.C1 Commissions. An extensive plan was developed in 2016 by the WG co-chairs, Margarita Metaxa and Constance Walker, and the Commission C.C1 and C.B7 presidents, Beatriz García and Richard Green. There are 20 members. Significant progress has been made in implementing educational programs along the theme, in particular with the NASE Kit, the IYL Quality Lighting Teaching Kit and the Globe at Night citizen-science campaign. Work in progress includes establishing a national contact in as many countries as possible for the joint Working Group, as well as establishing liaisons with government, educational and environmental organizations. These and other details will be reported on August 24 at the Division C meeting during Session 3 on Reports from the Commission WGs of C.C1 and its business meeting.
Globe at Night: Citizen-Science Assessing the Darkness of our Skies
Walker, Connie
Globe at Night (GaN) encourages citizen-scientists worldwide to record the brightness of the night sky. During ten-days per month of moonless evenings, children and adults match the appearance of a constellation with star maps of progressively fainter stars found at www.globeatnight.org/webapp/. In the 12 years of the program, over 175,000 observations from 180 countries have been contributed to the campaign.The GaN (open) database is a source of research projects. With GaN, citizen-scientists measured the darkness of the daytime sky for the total solar eclipse (TSE) in the USA in 2017. (Plans are forming for the TSE in Chile in 2019.) Students conducted research to understand the lesser long-nosed bats’ avoidance of city center at night. On-the-fly mapping enables citizen-scientists to see contributed observations immediately. The 12 campaigns per year offer 4 ways of taking measurements. The online app for data submission is in 28 languages. STEM activities allow young children and problem-based learning activities for older students to experience real-life scenarios: role-playing sea turtles hatching (misdirected by lights on shore) or analyzing an ISS image of Houston to estimate the wasted energy, cost and carbon footprint. In-situ and on-line workshops have been given on using GaN in all its capacities, as well as for the activities. Our Facebook page exists to encourage dialogue and bring cutting edge news. To entice interest, we had monthly newsletters and serial podcasts starring the Dark Skies Crusader. GaN has been part of special campaigns like with the National Park Service and the National Geographic BioBlitz. Partnerships also include SciStarter (working with participants), Fieldscope (working with data analysis), and STARS4ALL (working with other light pollution initiatives). We have built a community of practitioners in various ways worldwide and plan to continue to help reduce the effects of light pollution through awareness and action.
The Quality Lighting Teaching Kit: Utilizing Problem-Based Learning in Classrooms
Walker, Constance
Poor quality lighting impedes astronomy research and our right to see a starry night sky. It creates safety issues, affects human circadian sensitivities, disrupts ecosystems, and wastes billions of dollars/year in energy consumption. It also leads to excess carbon emissions. How do you change the mindset of society that is used to turning night into day? You educate the next generation on quality lighting.As an outcome of the International Year of Light 2015, the National Optical Astronomy Observatory’s Education and Public Outreach group produced a Quality Lighting Teaching (QLT) Kit. The kits are designed around problem-based learning scenarios. The kit’s six activities allow students to address real lighting problems that relate to wildlife, sky glow, aging eyes, energy consumption, safety, and light trespass. The activities are optimized for 11-14 year olds but can be expanded to younger and older. All materials are in both English and Spanish. Most of the activities can be done within in a few minutes during class or afterschool and as stations or as stand-alones. Everything you need for the six activities is included in the kit. Tutorial videos on how to do the activities can be found at www.noao.edu/education/qltkit.php. Ninety-two out of one hundred kits have been distributed in thirty-two countries through SPIE (the International Society for Optical Engineering), CIE (the International Commission on Illuminations), OSA (the Optical Society), IDA (the International Dark Sky Association), and the IAU OAD–Office of Astronomy Development. Successful feedback has promoted the opportunity to commercialize the kit. A plan is being considered to distribute kits to observatories around the world, hence helping to work with communities near observatories to reduce the effects of light pollution through awareness and action. These items will be discussed in the presentation and ideas welcomed.
The latest TSI measurement results from the Compact Lightweight Absolute Radiometer (CLARA) onboard the NorSat-1 micro satellite
Walter, Benjamin
Continuous and precise Total Solar Irradiance (TSI) measurements are indispensable to evaluate the influence of short- and long-term solar radiative emission variations on the Earth’s energy budget. The existence of potentially long-term trends in the Sun’s activity and their effects on Earth climate is a societally-important field of research. The Compact Lightweight Absolute Radiometer (CLARA) is one of PMOD/WRC’s future contributions to the almost seamless series of space-borne TSI measurements since 1978. CLARA was end-to-end calibrated against the SI-traceable cryogenic radiometer of the TSI Radiometer Facility (TRF) in Boulder (Colorado). The absolute measurement uncertainties for the three SI-traceable TSI detectors within CLARA are 567, 576 and 912 ppm (k = 1). CLARA is one of three payloads on the Norwegian micro-satellite NorSat-1, which was launched July 14th, 2017.We present the latest TSI observations of CLARA together with the lessons learned about the instrument behavior on NorSat-1 including: i) pointing instabilities of the satellite platform and its influence on TSI results, ii) degradation of the detector sensitivity, iii) instrument sensitivity to temperature variations, iv) CLARA’s ability for measuring TSI during solar eclipses for determining the Sun’s radius, and v) comparison of the TSI results to other space radiometers. The comparison between CLARA’s most stable Channel B preliminary first light observations of 1359.84 W m-2 and VIRGO’s new scale TSI observation (1360.14 W m-2) show that they are in good agreement within the instrument uncertainties.
Bio-habitability and life on planets of M- to G-type stars
Wandel, Amri
The recent detection of Earth-sized planets in the habitable zone of Proxima Centauri, Trappist-1, and many other nearby M-type stars (which consist some 75% of the stars) has led to speculations, whether liquid water and life actually exist on these planets. Defining the bio-habitable zone, where liquid water and complex organic molecules can survive on at least part of the planetary surface, we suggest that planets orbiting M-type stars may have life-supporting conditions for a wide range of atmospheric properties (Wandel 2018, ApJ in press). We extend this analyses to locked planets of K- and G-type stars and discuss the implications for the evolution and sustaining of life, in particular, oxygenic photosynthesis, in analogy to early Earth, as well as to present Earth extreme environments.
Biosignature detection and statistics of nearby bio-habitable planets
Wandel, Amri
We argue that habitable-zone planets of M-dwarf stars may have temperatures supporting liquid water and complex organic molecules on at least part of their surface, for a wide range of atmospheric properties (Wandel 2018, ApJ, in press). We apply these results to Proxima Centauri b and to the Trappist-1 system and discuss the implications to searching oxygen and other biosignatures in transiting habitable planets of nearby M dwarfs. From the Kepler data, we estimate that within 30pc TESS may find ~10-40 transiting candidates. We suggest that by detecting a few planets with atmospheric oxygen it may be possible to estimate the abundance of photosynthesis and biotic planets.
A Chinese effort to determine the solar model in the 18th century: the case of the Lixiang kaocheng
Wang, Guangchao
Ancient Chinese mathematical astronomy in its maturity was generally described as independent with the assumptions about the real motions of the physical luminaries. It was not until seventeenth and eighteenth centuries Chinese astronomy experienced a conceptual revolution under the influence of Western astronomy. Western astronomy, which Jesuit missionaries introduced during that time, had a more pervasive and profound influence on Chinese astronomy. Chinese native astronomers adopted Western mathematical methods from their Jesuit astronomers, they shifted their original paradigm from numerical and algebraic procedures to geometric model. This change allowed them not only to predict but also to explain astronomical phenomena. The solar model which adopted in Lixiang Kaocheng provides a concrete example of the way how Chinese domestic astronomers deal with computation and observation. Different with the eccentric solar model in Xiyang Xinfa Lishu,Kaocheng used the double epicycle model considering that the computation should be in agreement with the observation. Though it was a big apparent change from eccentric model to double epicycle model, but the accuracy of the data computed from the solar model did not increase largely compared with the previous calendar. Moreover, it has been found that the observational data which was the basis for computing the parameters of the solar model were so accurate that the astronomical instruments could not reach. These data probably come from the calculation result of extant western astronomical tables.
The DRAGON simulations: globular cluster evolution with a million stars
Wang, Long
Introducing the DRAGON simulation project, we present the first direct N-body simulations of four massive globular clusters (GCs) with 10^6 stars and 5% primordial binaries at a high level of accuracy and realism. The GC evolution is computed with NBODY6++GPU and follows the dynamical and stellar evolution of individual stars and binaries, kicks of neutron stars and black holes (BHs), and the effect of a tidal field. We investigate the evolution of the luminous (stellar) and dark (faint stars and stellar remnants) GC components and create mock observations of the simulations (i.e. photometry, colour–magnitude diagrams). By connecting internal processes to observable features, we highlight the formation of a long-lived 'dark' nuclear subsystem made of BHs, which results in a two-component structure. The inner core is dominated by the BH subsystem and experiences a core-collapse phase within the first Gyr. It can be detected in the stellar (luminous) line-of-sight velocity dispersion profiles. The outer extended core – commonly observed in the (luminous) surface brightness profiles – shows no collapse features and is continuously expanding. Variations in the initial mass function can result in significantly different GC properties (e.g. density distributions) driven by varying amounts of early mass-loss and the number of forming BHs. For global observables like core and half-mass radii, the direct simulations agree well with Monte Carlo models, while the details indicates the difference of BH dynamics in the cluster core. We are continuing to improve the simulation tools to achieve faster computational performance for even larger N and more realistic models.
Precise evolution of metallicity radial gradients at cosmic noon and its constraints on galaxy evolution
Wang, Xin
The chemo-structural evolution of galaxies at the peak epoch of cosmic star formation is a key issue in galaxy evolution physics. To address this, we investigate the spatial distribution of gas-phase metallicity in emission-line galaxies in the redshift range of z~1-3, i.e., at the cosmic noon. In a series of papers, we bring forward a novel method of obtaining sub-kpc resolution metallicity maps using space-based grism spectroscopy of strongly lensed galaxies. The sufficient spatial sampling, achievable only through the synergy of diffraction-limited data and lensing magnification, is crucial to avoid spuriously flat gradient measurements. Combining the deep HST/WFC3 near infrared grism data acquired by the GLASS project and a novel Bayesian method inferring metallicity from line fluxes directly, we obtained over 80 unbiased metallicity maps at z~1.2-2.3. This improves the number of such measurements by one order of magnitude. Our maps reveal diverse galaxy morphologies, indicative of various effects such as efficient radial mixing from tidal torques, rapid accretion of low-metallicity gas, which can effectively affect the gas and metallicity distributions in individual galaxies. We found two sub-luminous galaxies at z~2 displaying greatly inverted gradients, strongly suggesting that powerful galactic winds triggered by central star bursts carry the bulk of the stellar nucleosynthesis yields to the outskirt. We also observe an intriguing correlation between stellar mass and metallicity gradient, consistent with the ``downsizing'' galaxy formation picture and inside-out disk growth. Furthermore, 10% of the gradients measured in our sample are positive (i.e. inverted), which are hard to explain by currently existing hydro-simulations and analytical models. Our techniques can also be applied to data from future space missions employing grism instruments, e.g., JWST, WFIRST, Euclid.
Astrometric Measurements for Studies of Dwarf Galaxies
Watkins, Laura
Where is the mass in galaxies? From extensive observational campaigns, we have a good understanding of the distributions of the stellar and gaseous components, but the distribution of dark matter is still uncertain, especially in the centres of galaxies. Cosmological simulations suggest that galaxies form with a cuspy central dark matter profile, but that baryonic feedback processes can flatten the profiles toward cores. So determining accurate mass profiles not only provides tests of the cosmological model on galaxy scales, but also places strong constraints on the baryonic processes that have shaped galaxies. Since we cannot measure dark matter profiles directly, we use the kinematics of the stars in the galaxies. So far kinematic studies have been limited to line-of-sight velocities, which are sparse and probe only one component of the three-dimensional motion of the stars. Proper motion studies provide the other two components of motion and thus are crucial to make progress. Aside from stars in our Milky Way, proper motions can only be measured for stars in nearby dwarf galaxies. Even then it is a challenge that demands extremely high astrometric precision, better even than the Hubble Space Telescope and Gaia. Such datasets also demand similarly high standards in the modelling machinery used for their analysis. My talk will focus on the future prospects for measuring accurate proper motions in nearby dwarf galaxies with which their internal dynamics may be fully characterised. I will also discuss some work we have been doing using Hubble and Gaia proper motions to study other stellar systems surrounding the Milky Way and the state-of-the-art dynamical models we have developed to analyse them.
Cosmology the observational side
Webb, J.
TBA
The Imaging X-ray Polarimetry Explorer (IXPE)
weisskopf, martin
It has been over 43 years since the last extra-solar X-ray polarization observation was performed. Recently NASA selected a new, exciting mission, as part of the Small Explorer Program which will, for the first time, produce image-resolved polarimetry of astronomical sources. I am the Principal Investigator of this mission. I shall review the history of astrophysical X-ray polarimetry, discussing various experimental techniques and emphasizing the successful method of tracking the photoelectron in a low-Z gas that has allowed this experiment to proceed. After a discussion of the Observatory and its components, I shall present examples of the scientific advances that can be made by adding imaging polarimetry to the X-ray astronomer’s arsenal of tools for probing diverse questions such as: Was the black hole at the center of the Milky Way galaxy one million times more active a few hundred years ago? What is the spin the black holes in microquasars? Is there direct evidence for the effects of quantum electrodynamics in the strong magnetic fields in magnetars?
Modelling the cosmic evolution and large-scale alignment of angular momentum
Welker, Charlotte
Galaxies get angular momentum by cosmic gas infall from large-scale filaments. While merger-free disc galaxies should directly inherit from this gas infall, massive elliptical galaxies, for which most of the mass is assembled through mergers, obtain angular momentum differently than from smooth gas accretion. Those two different pictures of angular momentum acquisition lead to two significantly different signals of galaxy alignments in the cosmic web for discs and elliptical galaxies. I will show results from Horizon-AGN, a high-resolution hydrodynamical cosmological simulation, on galaxy alignments and the role played by feedback from active galactic nuclei in settling i) the change of morphology in massive galaxies, and ii) the reorientation of their angular momentum.
Changes in the photospheric magnetic field produced by flares
Wheatland, Michael
Data from space-based vector magnetograms and high-resolution ground-based telescopes clearly show large-scale changes in the photospheric magnetic field produced by solar flares. A striking example is the observation of sudden rotation of a sunspot in response to a flare on 22 June 2015 (Liu et al. 2016). Here we report on analysis and modeling of the 22 June 2015 event based on the Solar Dynamics Observatory Helioseismic and Magnetic Imager data.
The MWA GLEAM 4-Jy Sample
White, Sarah
Powerful radio-galaxies feature heavily in our understanding of galaxy evolution. However, when it comes to studying their properties as a function of redshift and/or environment, the most-detailed studies tend to be limited by small-number statistics. In this talk, I will present a new sample of nearly 2,000 of the brightest radio-sources in the southern hemisphere (Dec. < 30 deg). These were observed at low radio-frequencies as part of the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, which is a continuum survey conducted using the Murchison Widefield Array (MWA). This instrument is the precursor telescope for the low-frequency component of the Square Kilometre Array, and allows us to select radio galaxies in an orientation-independent way (i.e. minimising the bias caused by Doppler boosting, inherent in high-frequency surveys). Being brighter than 4 Jy at 151 MHz, we refer to these objects as “the MWA GLEAM 4-Jy Sample”. Thanks to the location of the MWA in a protected, radio-quiet zone, we have excellent spectral coverage for these sources, with 20 radio flux-densities spanning a frequency range of 72-231 MHz. By combining these measurements with those at higher frequencies, we can better investigate the processes that give rise to spectral curvature in the radio. Furthermore, we use multi-wavelength data -- such as existing optical spectra from the 6-degree Field Galaxy Survey (6dFGS) and mid-infrared images from the Widefield Infrared Survey Explorer (WISE) -- to identify the host galaxies of the low-frequency radio emission. Those with 6dFGS spectra are then used to provide first insights into the local sources with optically-bright hosts (median z = 0.09). Finally, with 10 times as many sources as the most-prominent, low-frequency radio-source sample that is optically complete (the revised Third Cambridge Catalogue of Radio Sources; 3CRR), the MWA GLEAM 4-Jy Sample will allow models of powerful active galactic nuclei to be tested more robustly.
AGB Variables in Nearby Galaxies
Whitelock, Patricia
Certain types of large amplitude AGB variable are proving to be powerful distance indicators that will rival Cepheids in the JWST era of high precision infrared photometry. These are predominantly found in old populations and have low mass progenitors. At the other end of the AGB mass-scale, large amplitude variables, particularly those undergoing hot bottom burning, are the most luminous representatives of their population. These stars are losing mass copiously and are vital to our understanding of the integrated light of distant galaxies as well as to chemical enrichment. However, the evolution of such very luminous AGB variables is rapid and remains poorly understood. In this talk I will discuss recent infrared observations of both low- and intermediate-mass Mira variables in the Local Group and beyond.
Understanding the mechanical feedback from high- and low-accretion rate radio galaxies
Whittam, Imogen
I will discuss the properties of ~1000 radio galaxies selected from a 1.4 GHz JVLA survey of Stripe 82. This survey covers 100 deg2 and is a factor of five deeper than FIRST, allowing us to probe the fainter radio galaxy population (1.4 GHz luminosity > 1021 W/Hz). Using optical spectra we have classified the sources as high-excitation (radiative mode) or low-excitation (jet mode) radio galaxies (HERGs and LERGs). We find that the HERGs tend to have higher Eddington-scaled accretion rates than the LERGs, but that there is more overlap between the two distributions than found by previous studies at higher radio luminosities. We show that the properties of the host galaxies (e.g. stellar mass and stellar age) vary continuously with accretion rate, with the most slowly accreting sources having the oldest stellar populations, consistent with the idea that these sources lack a supply of cold gas. We find that 84 per cent of our sample release more than 10 per cent of their accretion power in their jets, showing that mechanical AGN feedback is significantly underestimated in many hydrodynamical simulations. There is a scatter of ~2 dex in the fraction of the accreted AGN power deposited back into the ISM in mechanical form, showing that the assumption in many simulations that there is a direct scaling between accretion rate and radio-mode feedback does not necessarily hold. We also find that mechanical feedback is significant for many of the HERGs in our sample as well as the LERGs.I will also discuss the influence of environment on the accretion rates and host galaxy properties of the radio sources in this sample. Finally, I will discuss plans to build on this work using the MeerKAT telescope here in South Africa.
Germany's difficulties in becoming a member of the International Astronomical Union
Wielen, Roland
When the International Astronomical Union (IAU) and its parent organization, the International Research Council (IRC), were founded in 1919, Germany, Austria, Hungary and other nations were excluded from the membership in the IAU for political reasons connected with World War I. These restrictions were abolished only with the revision of the IAU Statutes in 1931._x000D_ In Germany, the question of an IAU membership was controversially discussed for various reasons: (1) the future role of the also internationally orientated 'Astronomische Gesellschaft (AG)', (2) the equitable use of the German language at international conferences, and (3) the disregard of Germany by the IRC. In 1931, a committee was established in Germany to consider the IAU membership: the 'Ausschuß der Deutschen Astronomen (ADA)'. The ADA concluded that the IAU membership of Germany was desirable, but impossible for financial reasons for the time being. This was announced at the IAU General Assembly in 1932. For the next decade, we do not know of any attempt of Germany to become a member of the IAU. Nevertheless, since 1928, German astronomers participated in the IAU General Assemblies as invited guests and in the work of the IAU Commissions as co-opted members._x000D_ After World War II, it took a few years until Germany became finally a member of the IAU in 1951. Austria became an IAU member in 1955, Hungary already in 1947. Initially the AG was the adhering organization for Germany at the IAU. In 1962, East Germany became an additional member of the IAU. West Germany's adhering organization was not anymore the AG but had to be replaced by the 'Rat Westdeutscher Sternwarten'. Due to the reunification of Germany in 1990, East Germany disappeared as a separate member of the IAU. Germany is now represented in the IAU by the 'Rat Deutscher Sternwarten (Council of German Observatories)', which is an organ of the AG since 2012.
IAU in the 21st Century
WILLIAMS, Robert
Beginning in year 2000 the IAU undertook a number of initiatives that changed the Union from being primarily an inward focused organization whose emphasis was the world of professional astronomy to being more outward looking in engaging the public. These initiatives included proposing to the United Nations and then leading the International Year of Astronomy IYA 2009, and the formulation of a Strategic Plan that included creation of the Office of Astronomy for Development. Additional programs are being undertaken by the Union that continue to broaden IAU engagement with the public.
Science with NIRISS: The Near-Infrared Imager and Slitless Spectrograph
Willott, Chris
The NIRISS instrument on JWST provides imaging and spectroscopy from 0.6 to 5 microns. I will describe science applications of the 4 observing modes of NIRISS, from characterizing extrasolar planets that could host life to understanding the formation of galaxies prior to cosmic reionization.
Mechanisms of accretion
Wilms, J.
TBA
HMXBs in gamma-rays and EM counterparts of GW events
Wilson-Hodge, C.
TBA
OSIRIS-REX: MAPPING THE DENSITY OF PARTICLES OVER THE SURFACE OF ITS TARGET
Winter, Othon
Asteroids and comets are thought to be critical for understanding the origin and evolution of the Solar system and possibly the origin of life on Earth. Several countries and space agencies have launched missions to these small bodies. The most recent one is the OSIRIS-REX mission to Asteroid (101955) Bennu. One of its main goals is to bring back to Earth a sample of pristine carbonaceous regolith from Bennu. The analysis of such material will be important to understand the role that primitive asteroids may have played in the formation of planets and the origin of life. In the present work we study the motion of particles near the surface of Bennu. An application of the results is to give assistance for the selection of the sample site. Considering the gravitational potential given by the polyhedral model of Bennu (1348 vertices, 2692 faces), we numerically simulated many samples of 10,000 test particles initially located randomly in a cloud around the asteroid. We have investigated eccentric and inclined orbits, and we also adopted different particle sizes, from fine dust grains up to small particles. It is already know that Bennu has eight equilibrium points around it, and according to the adopted density, a couple of them might be stable. The influence of the equilibrium points is very strong on the orbital evolution of the particles. In the long term dynamics most of the particles collided with the asteroid surface. From our results we generated map diagrams indicating the amount of particles distributed over the surface of Bennu. They show the spots of very high collision rates, where are expected to be fully covered of particles, and also those where it is expected to be cleaner (sites of very low collision rates). These diagrams are made for a range of dffierent particle sizes and also, with and without taking into account the solar radiation pressure in the dynamics of the orbital evolution. In order to make the selection for the sample site.
Stars and gas in the most metal-poor galaxies: SBS 0335-052E
Wofford, Aida
Understanding the properties of stars and gas at low metallicity is of large relevance for a variety of fields in astrophysics, since it relates to multiple topical questions which range from understanding the properties of galaxies that contributed to cosmic reionization to the evolution of metal-poor massive stars that give rise to the formation of heavy binary black holes. Crucial are observational constraints for the theoretical predictions. These can be obtained from rest-frame ultraviolet and optical spectra of the most metal-poor galaxies known. Among these, SBS 0335-052E (z=0.0135, 12+log(O/H)=7.3) is one of the most well-studied. For this galaxy, we present Hubble Space Telescope}(HST) / Cosmic Origins Spectrograph (COS) detections of the C IV 1549, 1551, He II 1640, O III] 1661, 1666, and [C III] 1907 + C III] 1909 UV emission lines; and a co-spatial Very Large Telescope (VLT) / Multi Unit Spectroscopic Explorer (MUSE) spectrum covering from 4600 to 9400 Ang. Using these and archival datasets we investigate plausible sources of hard ionising photons and test: a) the latest Charlot & Bruzal spectral synthesis models with very massive (300 Msun) single non-rotating stars; b) the performance of the spectral analysis tool, BayEsian Analysis of GaLaxy sEds (BEAGLE); and c) the extent to which physical properties of the gas and dust derived independently from the UV and optical are constrained.
The SkyMapper Southern Survey and its calibration
Wolf, Christian
I will present the progress of the SkyMapper Southern Survey with a focus on photometric calibration issues, highlighting all the challenges we have confronted so far. The SkyMapper Southern Survey covers over 20,000 deg2 of Southern sky in six optical passbands. It spans a dynamic range of 13 mag by combining its Shallow Survey of shorter exposures with its deeper Main Survey, both covering the whole hemisphere. We also have standard fields with HST spectrophotometric standards in them, and cross-matched our catalogue with external catalogues such as PS1 and Gaia.
Observatories 100 years ago - Unesco vs. IAU List of Outstanding Astronomical Heritage
Wolfschmidt, Gudrun
For observatories from Renaissance to 20th century it is sometimes difficult to include them in the Unesco World Heritage list because the architecture is not an outstanding example of a type of building, architectural or technological ensemble which illustrates (a) significant stage(s) in human history.There exist observatories, where the building is damaged, distroyed or it does not fulfill the authenticity and integrity standards, the instruments no longer exist in situ, but the institution had played a significant role in the history of astronomy regarding the scientific output; they did cutting-edge research in astronomy. For these cases the idea came up to create an "IAU List of Outstanding Astronomical Heritage" (OAH).For example I would like to include observatories like the Astrophysical Observatory Potsdam where no longer astronomers are working, or even observatories like Gotha (an international center of astronomy aroud 1800), where the original building is completely destroyed but the instruments are preserved in museums and in addition a lot of archive material. Or we can add in addition Tycho's observatory in Uraniborg, Hevelius observatory in Danzig (Gdansk) or some colonial observatories from the Jesuits. In the lecture the intended database structure will be presented.
The Cartwheel galaxy as a stepping stone for binaries' formation
Wolter, Anna
Ultraluminous X-ray sources (ULXs) are end points of stellar evolution.They are mostly interpreted as binary systems with a massive donor. They are also the most probable progenitors for BH-BH, and even more, for BH-NS coalescence. This last event has not been detected yet. Many recent estimates of expected rates (e.g. Inoue et al 2016) do take into consideration the ULX properties (Luminosity Function, active time, frequency by galaxy mass or SFR). However, many of these parameters are very uncertain or not known. Especially crucial is the link with the metallicity of the environment (e.g. Mapelli et al 2010) which has been invoked frequently but not proven strongly. We have tackled this problem by using a MUSE DEEP mosaic of the Cartwheel galaxy and applying a newly developed Monte Carlo code that jointly fits spectroscopy and photometry (Fossati et al. 2018).The Carthweel is the archetypal ring galaxy and the location and formation time of new stellar populations is easier to reconstruct than in more normal galaxies. It has the largest population of ULXs ever observed in a single galaxy (16 sources have been classified as ULXs in Chandra and XMM-Newton data).The Cartwheel galaxy is therefore the ideal laboratory to study the relation between Star Formation (SF Rates and SF History) and number of ULXs and also their final fate.We will show the derived SFHs and the formation timescale for three different zones of the galaxy, tracing the impact that created the ring. We aim at measuring the ionization properties and metallicity of the emitting gas at the positions of X-ray sources by constructing spatially resolved emission line ratio maps and BPT diagnostic maps.The findings for the Cartwheel will be a testbed for further modelization of binary formation and evolution paths.
The intermediate-power population of radio galaxies: morphologies and interactions
Worrall, Diana
Radio galaxies of intermediate power dominate the radio-power injection in the Universe as a whole, due to the break in the radio luminosity function, and so are of special interest. The population spans FR I, FR II, and hybrid morphologies, resides in a full range of environmental richness, and sources of all ages are amenable to study. Structures and interactions will be described, with emphasis on sources with deep high-resolution Chandra X-ray data. As compared with low-power sources there is evidence that the physics changes, and the work done in driving shocks can exceed that in evacuating cavities. The range of morphologies and phenomena will be illustrated and summarized.
The JWST Mid Infrared Instrument (MIRI) and the science it enables
Wright, Gillian
I will provide an overview of the James Webb Space Telescope MIRI instrument and its scientific capabilities. The only mid-infrared instrument for JWST, MIRI provides diffraction limited imaging, low resolution spectroscopy, coronagraphs and moderate resolution integral field spectroscopy at wavelengths ranging from 5 to 28um. These capabilities coupled with unprecedented sensitivity and spatial resolution compared to previous missions will enable a broad range of science. I will discuss examples from the early science plans, showing how MIRI will be used to address topics from star and planet formation, to the earliest galaxies in the Universe
Mass and Age of Red Giant Branch Stars Observed with LAMOST and Kepler
wu, yaqian
Obtaining accurate and precise masses and ages for large numbers of giant stars is of great importance for unraveling the assemblage history of the Galaxy. In this paper, we estimate masses and ages of 6940 red giant branch (RGB) stars with asteroseismic parameters deduced from \emph{Kepler} photometry and stellar atmospheric parameters derived from LAMOST spectra. The typical uncertainties of mass is a few per cent, and that of age is $\sim$\,20 per cent. The sample stars reveal two separate sequences in the age -- [$\alpha$/Fe] relation -- a high--$\alpha$ sequence with stars older than $\sim$\,8\,Gyr and a low--$\alpha$ sequence composed of stars with ages ranging from younger_x000D_ than 1\,Gyr to older than 11\,Gyr. We further investigate the feasibility of deducing ages and masses directly from LAMOST spectra with a machine learning method based on kernel based principal component analysis, taking a sub-sample of these RGB stars as a training data set. We demonstrate that ages thus derived achieve an accuracy of $\sim$\,24 per cent. We also explored the feasibility of estimating ages and masses based on the spectroscopically measured carbon and nitrogen abundances. The results are quite satisfactory and significantly improved compared to the previous studies.
Solar Irradiance Reconstruction over the Last 9 Millennia with a Multi-isotope Composite
Wu, Chi-Ju
While direct measurements of the solar irradiance are available for the last four decades, reconstructions of the past solar variability are needed to understand the solar influence on Earth's climate. The longest observational record of solar activity is the sunspot number, going back to 1610 A.D. with uneven quality. To assess solar variability at earlier times, indirect proxies of solar activity, such as concentrations of cosmogenic isotopes 10Be and 14C in terrestrial archives are often used. These isotopes are produced in the terrestrial atmosphere by impinging cosmic rays, whose flux is modulated by both heliospheric magnetic field and geomagnetic field. Therefore, the isotope signals retrieved from various sites around the globe show a very high degree of similarity, reflecting changes in the solar activity. Significant short-and mid-term deviations, however, can be observed due to the different geochemical production and redistribution processes and local climatic conditions. We have taken this into account and developed a state-of-the-art consistent multi-isotope composite reconstruction of solar activity based on six regional 10Be and the global 14C data sets. This composite is then used to reconstruct the total TSI and spectral SSI solar irradiance over the last 9000 years with a semi-empirical model (SATIRE-M) developed in MPS. We also apply statistical analysis to reconstruct the pseudo-solar cycle on millennial time scale.
Starlight and World Heritage
Wuchterl, Günther
The nightsky and the universe have been largly abstracted from localities in modern astronomy. Thus they cannot be directly associated with a site on a member-state territory as required by the world heritage convention. They also escape the required comparative discussion because there is only one universe and one nightsky.However, the universe and its perspective from Earth provide the phyiscal basis for the apparent phenomena at a site, Astronomy determines how light flows through and how it interacts with atmosphere, climate, weather, landscape and artefacts to locally shape day and night.If the flow of light is perturbed by human intervention - by the introduction of artificial light - the consequences are comparable to the removal of water in irrigation systems or waterfalls and the intact flow of water through the site. Both are well embedded in the world heritage convention and list. The intact flow of light, by night originating from an intact night sky, are a necessary precondition for the authentic appearance of a site due to the nature of human vision and perception in general.I will discuss concepts to include sites in the world heritage framework where astronomical phenomena and physical conditions have to be protected to fullfill the requirements and support the goals of the world heritage convention in cases where in daylight-only argumentation no or insufficient outstanding universal value seems to be present. In particular when no archeaoastronomical evidence, no site protection requirements of telescopic astronomy and no classical observatories are at a site.The concepts of “regionalised skies”, “pretelescopic scientific epochs”, “the phyiscal intactness of light flow” and “authenticity at night” will be introduced and applied to cases of the thematic study on astronomy and world heritage - The Aoraki Mackenzie, the Eastern Alpine and Großmugl Starlight Areas.We will also present management tools to protect the OUV of such sites.
Dwarf galaxies during reionization
Wyithe, Stuart
In this talk I describe insights into the modelling and astrophysics of dwarf galaxies during reionization from the DRAGONS suite of hydrodynamic and semi-analytic simulations. Comparison of our N-body and hydrodynamic simulations shows that the hydrostatic suppression of baryonic accretion affects the growth rate of dwarf galaxy dark matter haloes at z>6, lowering the amplitude of the halo mass function by factors of ~2-4, and so dramatically reducing the number of halos available to host galaxies in the reionization era. Our hydrodynamical simulations further show that unlike the case of self-regulated low redshift galaxies, the bottleneck for growth of early dwarf galaxies is in converting infalling gas to cold star-forming gas, which uniformly occurs over a time-scale of 300 Myr. We have incorporated these properties into the MERAXES semi-analytic model, and used it to study the role of dwarf galaxies during reionization. The steep faint-end slope of Ly-break galaxies at z>6 is predicted to extend beyond absolute magnitudes of -12, implying that approximately 50% of the ionizing photons needed for reionization have been observed at z<7. I will show how the resulting reionisation structure is sensitive to the high-z dwarf galaxy population, and that its measurement with SKA-low will help discriminate between different galaxy formation scenarios.
Probing the Galactic population of black holes with OGLE and Gaia
Wyrzykowski, Lukasz
As shown by recent gravitational wave detections, galaxies harbour an unknown population of black holes at high masses. In our Galaxy such dark objects can be found and studied solely via gravitational microlensing method. We describe our search for black hole lenses in both archival OGLE data and among on-going microlensing events found by OGLE and Gaia. Combination of superb time-domain astrometry from Gaia and photometry will allow to uniquely derive masses and distances to these dark lenses and describe the demographics of the unseen component of the Milky Way.
Metallicity gradients and evolution based on the LAMOST spectroscopic surveys
Xiang, Maosheng
Stellar metallicity gradients, especially their temporal evolution, set important constrains on the galactic chemical and dynamical evolution history. The LAMOST Galactic spectroscopic surveys have collected 10 million stellar spectra, from which accurate and precise stellar atmospheric parameters, chemical abundance, radial velocity, luminosity (distance) and especially age have been delivered for millions of stars with simple selection function. This unprecedented dataset allows us to characterize the stellar metallicity distributions at different positions and for different ages in great detail, thus to obtain deep insights on the chemical (and dynamical) evolution history of our Milky Way galaxy. In this talk, I will present efforts on characterizing Galactic stellar metallicity gradients and distributions for mono-age populations with LAMOST data, and discuss their constrains on Galactic assemblage and evolution history.
Observations of Gamma-Ray Burst (GRB) and Gravitational Wave Electromagnetic counterpart (GW EM) by Insight-HXMT
Xiong, Shaolin
The High Energy X-ray telescope (HE) onboard Insight-HXMT (Hard X-ray Modulation Telescope), the first Chinese X-ray space telescope launched on June 15, 2017, is primary designed to observe the hard X-ray sky from its narrow Field of View (~6 deg) defined by the collimators. However, thanks to the innovative usage of the anticoincidence detector, HE has been extended to monitor GRBs and GW EM counterparts, making it one of the most large gamma-ray monitors in the multi-messenger gravitational wave astronomy era. HE features a very large collection area (~1000 cm2), moderate localization accuracy (~5 deg) and microsecond time resolution in 0.2-5 MeV. As of Feb. 2018, Insight-HXMT/HE has detected more than 45 GRBs, including several short hard ones which were solely detected by it. During the observation of the first binary neutron star merger (GW170817), Insight-HXMT/HE monitored the entire GW localization area throughout the trigger time. Although Insight-HXMT did not detect any significant high energy (0.2-5 MeV) radiation from GW170817, its observation helped to confirm the unexpected weak and soft nature of GRB 170817A. Meanwhile, Insight-HXMT/HE provides one of the most stringent constraints (~10-7 to 10-6 erg/cm2/s) for both GRB170817A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger.
Theory of Interstellar Turbulence
Xu, Siyao
PhD Prize 2018 – TBA
CMB weak lensing with the primordial magnetic field
Yamazaki, Dai
We illustrate that a primordial magnetic field (PMF) suppresses the cosmic microwave background (CMB) B mode from the weak lensing (WL) effect. The WL effect is dependent on the lensing potential (LP) from the matter perturbations. A distribution of the matter perturbations on the cosmological scales is given by the matter power spectrum (MPS). Therefore, the WL effect on the CMB B mode is affected by the MPS. Considering effects of an ensemble average energy density of the PMF, which we call ''the background PMF'' in this letter, on the MPS correctly, the amplitude of MPS is suppressed on the wavenumber range 0.01 h Mpc-1 < k < 0.2 h Mpc-1. Since the MPS affects the LP and the WL effect on the CMB B mode, the PMF can damp these. The previous approaches to study the WL effect on the CMB B mode with a PMF have only considered vector and tensor modes from a PMF. On the one hand effects of vector and tensor modes from a PMF boost the CMB B mode on the higher multipoles l > 1000 mainly, on the other hand the effects of the background PMF damp the CMB B mode from the WL effect on the all multipole range. The matter density in the Universe determines the WL effects. Therefore, when we constrain the PMF and the matter density parameters from cosmological observational data sets including the CMB B mode, we expect that there is a degeneracy between these parameters. The CMB B mode, also provide important information of the background gravitational wave, the inflation theory, the matter density fluctuations and the structure formations in the cosmological scale through the cosmological parameter search. If we precisely research these topics and correctly constrain the cosmological parameters from the cosmological observation including the CMB B mode, we should consider the background PMF correctly.
A Circular Ribbon Flare Event as Observed by MUSER
Yan, Yihua
A Radio burst event on Dec 17, 2014 for a M8.7 flare was recorded by MUSER in 400MHz-2GHz. MUSER (Mingantu Spectral Radioheliograph) is a solar-dedicated interferometric array with a frequency range from 400MHz to 15 GHz located in Mingantu Town, Inner Mongolia of China. The flare was with circular ribbons over multiple-scale loop structures as revealed by AIA/SDO. There were groups of small-scale low-lying arcades or loops, intermediate dome-like structure, and the large-scale loops as shown in EUV images involved in this flare process. The multi-frequency images in decimeter wave ranges of the burst process by MUSER are obtained and analyzed.
Division E President's report
Yan, Yihua
Business Meeting of Div.E and its Commissions, WGs
The PACA Project Ecology: Development Strategy for Successful Pro-Am Observing Campaigns
Yanamandra-Fisher, Padma
The interactions of amateur astronomers with professional astronomers have changed significantly in the digital era, from an occasional exchange of individual images to a sustained collaboration. Today, amateur astronomers, with sophisticated equipment and software, provide several valuable resources to the professional observers/astronomers: coordinated global networks of amateur astronomers and robotic telescopes; a vast collection of legacy and temporal data and help build bridges between the scientific and public communities. The Pro-Am Collaborative Astronomy (PACA) Project, evolved from the successful NASA observational campaign CIOC to characterize Oort-cloud comet C/2012 S1(ISON) in 2013 on its initial passage through the inner solar system. With the inclusion of amateur astronomers; adaptation of various social media platforms and components of emerging field of citizen science, four phases for a successful pro-am collaboration were identified: (1) identification of a scientific knowledge gap; (2) integration of the pro-am communities; (3) adopt emerging technology and (4) stay in the limelight with results of the campaign. Several important results that emerged from the successful campaigns are: (i) establishment of a global network of astronomers that can be galvanized into action on short notice; (ii) provide an alert-sounding mechanism to all observers; (iii) immediate outreach and dissemination of results via our media/blogger members; (iv) provide a forum for discussions between the communities to help strategize the observing campaign for maximum benefit and (v) identify potential challenges on the data archival and its crowdsourcing. I will illustrate these concepts and strategies for building successful pro-am campaigns, with examples from various successful PACA- and non-PACA campaigns, including NASA/CIOC campaigns; ESA/Rosetta mission to comet 67P; and NASA 2017 Total Solar Eclipse polarization experiment with citizen scientists.
Helioseismic Holography Using Multiple Vantage Points
Yang, Dan
Helioseismic holography is a technique to image the solar interior in three dimensions using acoustic waves observed at the solar surface. Here, we consider the theoretical problem of imaging a localised sound-speed heterogeneity using partial views of the solar surface. Using a wave solver in the frequency domain, we compute holograms for three different geometries: observations of the entire solar surface, from a single spacecraft, and from two spacecrafts with different vantage points. We compare spatial resolutions and signal-to-noise ratios.
Observing various alignment signals of galaxies
Yang, Xiaohu
In this talk, I will present some recent observational measurements of various alignments of galaxies with respect to the orientations of the brightest central galaxies (BCG), the cosmic web structures, etc. These alignments are measured for the distributions of galaxies, the orientations of the galaxy major axes, spin axes, etc. The main findings in these measurements include: (1) satellite galaxies are preferentially distributed along the major axes of the BCGs, (2) the red satellites are preferentially aligned radially with the direction to the BCGs, (3) the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, (4) the spin axes only have weak tendencies to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor, etc. These measurements are very useful in our understanding of structure and galaxy formation, and can be used to constrain the spin and shape origin of galaxies. In addition, these alignment signals are also important in our modelling of the intrinsic weak lensing signals.
A spatially-resolved study of star and planet formation in Local Group galxies
Yasui, Chikako
We are studying environmental effects of star and planet formation. Among them, we have been previously focusing on metallicity dependence. Metallicity is one of the most critical factor for star and planet formation because dust forms planet cores despite of very small mass fraction in disks (~1%) and because metal is sensitive to heating and cooling in star forming processes, and directly related to radiative transfer. For the region where metallicity is different from solar neighborhood, we are focusing on the outer Galaxy, which we defined as the region with Galactocentric distance of >~ 18kpc. It is known to have as low metallicity as ~-1dex. The environments are similar to that in nearby dwarf galaxies, damped Lyman-alpha systems, and that in the early stage of the formation of the Galactic disk. We have obtained NIR images of young clusters in the outer Galaxy, using the Subaru 8.2-m telescope, and clearly resolved cluster members with mass detection limits of ~0.1 M_solar. Based on the fitting of K-band luminosity functions (KLFs), we found that the initial mass function (IMF) in the outer Galaxy is consistent with that in the solar neighborhood in terms of the high-mass slope and IMF peak. However, we also found that the fraction of stars with a K-band excess (which originates from the inner circumstellar dust disk at radii of r <= 0.1 AU) is significantly lower than those in the solar neighborhood, suggesting a metallicity dependence of the disk lifetime. Upcoming observations with a higher spatial resolution and sensitivity, using ELT, will allow us to extend spatially-resolved studies of the IMF and protoplanetary disk evolution to Local Group galaxies. Using high spatial resolution and sensitivity (0.02 arcsec and K~27 mag with AO), stars with mass of down to ~1M_solar can be detected and can be resolved sufficiently. From this study, we will gain new insights into wider environmental effects of star and planet formation.
The Hirayama families of asteroids: Various aspects of discovery
Yoshida, Seiko
Japanese astronomy after the Meiji Restoration grew in the cradle of geodesy while joining the network of IAG. Hirayama Kiyotsugu (1874-1943) began his career as a researcher with latitude observation and then exited from this field, and pioneered a new field of dynamical research of asteroids in japan. October in 1918, his paper “Groups of asteroids probably common origin” was published in the Astronomical Journal. He tackled the challenges of celestial mechanics that attracted astronomers’ attention.We have discussed three aspects of the likely background that led him to the discovery of the asteroid families, but they were all classified as scientific activities: 1. mathematical and astronomical training through Tisserand’s book Traité de Mécanique Céleste before he went to the USA; 2. new interests motivated by E. W. Brown (1866-1938); 3. the Kirkwood gaps as a clue to the discovery.It is better for the discovery story to be told not only from those aspects but also from other aspects: 1. social situation when he was promoted to associated professor at the Tokyo Imperial University (1906); 2. Circumstances that he was to engage in computing ephemerides of the moon and others at the Tokyo Astronomical Observatory (1908). With this calendar-making, he got a chance to learn the latest lunar theory under Brown.We have pointed out that his discovery were seen by the majority of Japanese scientific community as being simply statistical. We said that such a view was influenced by his statistical analysis of the Kimura’s Z-term. Finally, we consider the meaning of "statistical" of the time and feed back to the story.S. Nakayama (1928-2014) stated Hirayama’s researches were based on statistics as well as on the known principles of celestial mechanics. Y. Kozai (1928-2018) kept emphasizing Hirayama had used the proper elements instead of the osculating elements to identify families.Ref. Highlighting the History of Astronomy in the Asia-Pacific Region (2011)
Multi-band photometry of young family asteroids at Maidanak Observatory
Yoshida, Fumi
We have conducted the multi-band photometry of young family asteroids (Karin, Veritas, Iannini) at Maidanak Observatory, Uzbekistan in 2014 - 2016. Since the members of young asteroid families have little time to undergo significant collisional/dynamical evolutions till now, they probably still preserve properties of the disruption event which they were formed. And they probably still keep the “fresh” (not weathered) surfaces, which is the surface that the space weathering process has not completely altered. With these motivation, we investigated the colors of 17 young family asteroids.
The birth environment of the solar system constrained by the relative abundances of the radionuclides
Young, Edward
The relative abundances of the radionuclides in the solar system at the time of its birth are crucial arbiters for competing hypotheses regarding the birth environment of the sun. The presence of short-lived radionuclides, as evidenced by their decay products in meteorites, has been used to suggest that particular, sometimes exotic, stellar sources were proximal to the sun's birth environment. The recent confirmation of neutron star - neutron star (NS-NS) mergers and associated kilonovae as potentially dominant sources of r-process nuclides can be tested in the case of the solar birth environment using the relative abundances of the longer-lived nuclides. Critical analysis of the 15 radionuclides and their stable partners for which abundances and production ratios are well known suggests that the sun formed in a typical massive star-forming region (SFR). The apparent overabundances of short-lived radionuclides (e.g., 26Al, 41CA, 36Cl) in the early solar system appears to be an artifact of a heretofore under-appreciation for the important influences of enrichment by Wolf-Rayet winds in SFRs. The long-lived nuclides (e.g., 238U, 244Pu, 247Cr, 129I) are consistent with an average time interval between production events of 108 years, seemingly too short to be the products of NS-NS mergers alone. The relative abundances of all of these nuclides can be explained by their mean decay lifetimes and an average residence time in the ISM of ~ 200 Myr. This residence time evidenced by the radionuclides is consistent with the average lifetime of dust in the ISM and the timescale for converting molecular cloud mass to stars.
Considering the Potential and Development Strategy of Astrotourism in Indonesia using GIS-MCDA and Quantitative Strategic Planning Matrix (QSPM)
Yuna, Dwi Yoshafetri
Indonesia is the fourth-largest country in Asia shaping an arc between Asia and Australia, consists of five large islands and more than 13.600 smaller islands. Having various enticing landscapes and attractive cultures, it’s not surprisingly that Indonesia have many tourist destinations. This research signifies that several existing natural tourist destinations potentially can adopt and build up an astrotourism attraction in the location.Terrestrial Astrotourism is a new promising sustainable tourism niche in the future (Foster, 2017). Tourism and astronomy can be a mutual symbiosis. As an Indonesia’s leading economy sector, tourism is an appropriate bridge to astronomy popularization toward the public which surely stimulates the advancement of astronomy research and education. At the same time, astronomy is a strategic tourism niche which is in line with government’s sustainable tourism principle along with Sustainable Tourism Development (STD) issue around the globe. So, this paper aims, firstly to consider the potential destination which feasibly adopt the astrotourism and finally to propose a strategic recommendation for astrotourism development in the location. The potential locations are considered utilizing Geographic Information System (GIS) combining Multi-criteria Decision Analysis (MCDA) using several astro-climatologic and tourism criteria. Whilst the recommendations for astrotourism development in potential destinations are developed using Quantitative Strategic Planning Matrix (QSPM) method involving various internal and external factor analysis.The result of the research will be beneficial for both astronomy development and government as a win-win solution responding astronomy popularization and urgency of sustainable tourism development in the country.Keywords: Astrotourism, Sustainable Tourism Development (STD), Geographic Information System (GIS)-Multi-criteria Decision Analysis (MCDA), Quantitative Strategic Planning Matrix (QSPM)
Presentation of the IAU PhD Prize Winner
Zackay, Barak
TBA
Italian Astronomers@IAU. The contribution and the role of the Italian astronomers inside IAU from the foundation to the Second World War
Zanini, Valeria
The Italian astronomers were involved in the birth of the IAU as early as 1919, but Italy joined officially at the Astronomical Union only in 1921. Astronomers from all over the world met in Brussels for the first time on July 1919 and Annibale Riccò, the Director of Catania Observatory, was appointed Vice-President of the Executive Committee on that occasion. During the conference, Riccò invited the IAU Committee to hold its first General Assembly in Rome, the native country of Galileo Galilei and Angelo Secchi, the pioneer of the Astrophysics. Unfortunately Riccò didn’t see realized his desire, because of his unexpected death; his role was entrusted to Antonio Abetti, Director of the Florence Observatory. After him Vittorio Cerulli of the Teramo Observatory, Giorgio Abetti, son of Antonio and his successor at the direction of Florence Observatory, and Emilio Bianchi, Director of Brera Observatory, were appointed at the same office until 1952 continuously. In this year the VIIIth IAU General Assembly was held in Italy, thirty years after the first one and in the same place: Rome.This presentation will analyze the contribution and the role of Italian astronomers to the development of the International Astronomical Union until the Second World War. The recent project of reordering of the Italian astronomical historical archives permits a more in-depth study of the relations between Italian astronomers and a wider international scientific context.
Studying the star formation activity in two massive proto-clusters at z>2
Zavala, Jorge
Taking census of the protocluster's star formation activity -and to compare it to a sample of mass-matched galaxies in normal environments- is crucial to understand how environment impacts the growth of galaxies. We focus on two particularly unique protoclusters: the z=2.10 and z=2.47 structures in the COSMOS field. These structures contain several starbursting dusty star-forming galaxies and extends up to half a degree in the sky, in line with expectation of massive clusters in formation. Using ALMA continuum observations, we find evidence of an accelerated evolution in the most massive galaxies, while normal, less massive sources are in agreement with those galaxies in the field.
Characterization of compact object populations in nearby galaxies
Zezas, Andreas
The demographics of compact objects is a key parameter for constraining models of massive stellar evolution and understanding the populations of gravitational wave progenitors and short gamma-ray bursts. NuSTAR has opened a new window in this field by enabling the characterization of the compact objects in X-ray binary systems in nearby galaxies. We present a diagnostic tool for the classification of X-ray binaries on the basis of their compact objects and their accretion state. We apply this tool on NuSTAR observations of a sample of nearby galaxies spanning a wide range of specific star-formation rates, and hence star-formation environments. Our analysis indicates that more actively star-forming galaxies host a larger fraction of black-hole systems. Furthermore, we see a clear preference for accreting pulsars to be associated with star-forming regions, in good agreement with similar studies in our Galaxy. Finally, we compare these results with predictions from population synthesis models for different star-formation scenarios.
Introduction to Insight-HXMT: China's first X-ray Astronomy Satellite
Zhang, Shuang-Nan
Insight-HXMT is China’s first X-ray astronomy satellite launched on June 15th, 2017. It carries three sets of collimated X-ray instruments, covering energy ranges of 1-15 keV, 5-30 keV, and 20-250 keV, respectively. In addition, it can serve as a nearly all-sky monitor for high energy sources between 0.2 to 3 MeV, such as bright pulsars and gamma-ray bursts. The performance verification (PV) and calibration program has finished in November 2017 and the regular science observation program has has been on going. In this talk, I will describe the instrumentation of Insight-HXMT, its in-orbit performance and some early results, including the Galactic plane scanning survey, black holes, pulsars, gamma-ray bursts, etc.
Magnetic fields and massive star formation
Zhang, Qizhou
Massive stars (M > 8Msun) often form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. The role of magnetic fields during the formation of massive dense cores is still not clear. The steady improvement in sensitivity of (sub)millimeter interferometers over the past decade enabled observations of dust polarization of large samples of massive star formation regions. In this talk, I will present a legacy survey carried out with the Submillimeter Array of massive star forming clumps in polarized continuum emission at a wavelength of 0.89mm. This unprecedentedly large sample of massive star forming regions observed by a submm interferometer before the ALMA era revealed compelling evidence of strong magnetic influence on the gas dynamics from 1pc to 0.1pc scales. I will present the results from the SMA legacy survey as well as our followup studies of this sample at higher angular resolutions with ALMA that probe the role of magnetic fields at scales < 0.01pc.
A systematic study on isotope ratios toward molecular clouds in our Galaxy
Zhang, Jiangshui
Isotope abundance ratios play a key role in our understanding of stellar nucleosynthesis, stellar ejecta, and the chemical evolution of the Milky Way. So far, however, there are a few works on C, O, S isotopes and especially lack data from the Galactic center region and far outer galaxy, no systematic research has been done. Thus we are performing systematic studies on the isotope ratios, including 18O/17O and 12C/13C, 32S/34S, 14N/15N etc. Here we present results on isotopic ratio of 18O/17O toward a large sample of more than 150 sources, including especially many sources with large galactocentric distance. Our observations on C18O and C17O J = 1–0 lines were performed thorough ARO 12m and IRAM30m telescopes. Our preliminary results support a radial gradient along the Galactic disk for the abundance ratio, which is consistent with the inside-out formation scenario of our Galaxy. Our coming J=2-1 line data of C18O and C17O toward our large sample will be important for constraining opacities and abundances and finally confirming the Galactic radial gradient. Our performing observations on other isotope ratio projects will also be introduced.
Multi messengers to gamma-ray XRB
Zhang, Shu
The Insight-HXMT is the China’s first astronomy X-ray satellite, which was selected in 2011 and launched on June 15th 2017 to an orbit of 550 km altitude and 43 dg inclination. It was designed to serve for at least 4 years in an energy band of 1-250 keV, for which the core science researches will be carried out in ways of: Galactic survey for transients, pointed observation on the bright XRBs, multi-wavelength campaigns and observations on burst events like GRB, GW EM and so on. I report our recent researches on the gamma-ray XRBs of e.g. LS5039, LS 61303, LS1259, with the multi-messengers of RXTE, Fermi, INTEGRAL, and Swift. The results will be addressed and discussed in the context of having the currently orbiting Insight-HXMT.
Iron dust growth in the Galactic interstellar medium: clues from element depletions
Zhukovska, Svitlana
Iron is severely depleted from the interstellar gas compared to interstellar silicon. We address a long-standing question ``Where is the missing interstellar iron?'' using a model of dust evolution inhomogeneous, multiphase interstellar medium based on hydrodynamic simulations. The model includes dependence of dust destruction in SN shocks and growth by accretion of gas-phase metals on local physical conditions. In order to reproduce the observed trend of interstellar Fe depletion with gas density, our model requires that solid iron resides in two dust components: (i) metallic iron nanoparticles with sizes in the range of 1—10 nm and (ii) small inclusions in silicate grains.
AGB stars and the cosmic dust cycle: a probe of galactic evolution
Zhukovska, Svitlana
Theoretical and observational studies of dust condensed in outflows from AGB stars have substantially advanced the understanding of the dust mixture from individual stars. This detailed information incorporated into models of the lifecycle of interstellar grains allows us to evaluate the contribution of AGB stellar populations to the galactic dust budget, their role in the dust production and how it changes with galactic evolution. I will discuss what we learn from applications of the models of the lifecycle of grains from AGB stars for galaxies near and far. I will highlight important questions of galactic evolution that can be answered by these models in combination with modern infrared observations.
ELT/MOSAIC survey of dynamical and stellar properties of galaxies at z=1
Ziegler, Bodo
I will make the case for a 3D-spectroscopy survey of galaxies at z=1 with ELT/MOSAIC to derive comprehensively the main physical properties of the stellar component. Similar to CALIFA's IFU observations of local galaxies encompassing the whole variety of Hubble types and spanning a wide range in masses that enabled many different detailed studies we need to build up a statistically significant sample of galaxies at z=1 comprising different types with a wide range in masses, star formation rates, and gas fractions. Due to the surface brightness dimming ELT/MOSAIC is mandatory to achieve the required S/N needed to derive stellar population parameters (from absorption lines in contrast to gas emission lines) and stellar kinematics across ~3 disk scale lengths. Only this will allow the determination of dynamical masses via Jeans and Schwarzschild modelling of the velocity fields out to the turn-over radius where dark matter becomes dominant.
What can say observations of comets about the solar wind at the Maunder minimum?
Zolotova, Nadezhda
We consider the question of whether observers in the 17th century left historical records on the monitoring of the plasma tails of comets, which would allow us to judge the physical parameters of the solar wind. The magnitude of the deviation angle of the comet tail from the prolonged radius-vector of a comet defines the type of the comet tail: plasma or dust. We consider Bessel's and Bredikhin's calculations of trajectories of 10 comets during the Maunder minimum (1645-1715). For these comets the value of the angle between the tail axis and the prolonged radius-vector on the average exceeds 10 degrees that is typical of dust tails. Also note that visual observations of the ion tails of comets are very difficult due to the spectral composition of their radiation. This confirms our conclusion that the comet tails observed in the 17th century are not suitable for discussion about the physical parameters of the solar wind in the past.
Oscillation mode variability in pulsating hot B subdwarfs and white dwarfs from Kepler photometry
Zong, Weikai
The Kepler satellite provides unprecedented and uninterrupted high-quality photometric data with a time baseline of about 4 yr collected on pulsating stars, which is the unique opportunity to characterize the long-term behaviours of oscillation modes. A mode modulating in amplitude and frequency can be independently inferred by its fine structure in the Fourier space, detected by the sliding Lomb-Scargle periodogram, and measured by prewhitening the entire light curves parts by parts. We apply these techniques to the evolved compact stars KIC 3527751, KIC 08626021 and KIC 10139564 and find that many rotational multiplets whose components show clear amplitude and/or frequency variations. These modulations can be periodic, irregular and stable over the Kepler observations, which are the first signatures of nonlinear interactions due to the resonant mode coupling theory. Our results suggest that oscillation modes with diverse variations should be a common phenomenon in pulsating sdB and white dwarf stars. This resonate an idea that the closed peaks need to be seriously examined for mode identification, which is a key input parameter of seismic modelling. These various modulation patterns motivate more precise stellar oscillation theory to be developed. It also raise a warning to any long-term project aiming at measuring the rate of period change of pulsations due to stellar evolution or discovering stellar (planetary) companions around pulsating targets. These phenomena can also be thoroughly examined in many types of pulsating stars over the entire HR diagram from the photometry of the upcoming TESS mission.
Changes in the Unchangeable: Simulation of Transient Astronomical Phenomena with Stellarium
Zotti, Georg
Since the 1980s, desktop planetarium programs have been a great help for visualizing the sky and computing the positions of the planets and other objects in present and past times. Advances in graphical capabilities of affordable personal computers allowed the development of ever more visually realistic simulations, and the development of the world-wide web, broadband communication and open-source movement of software development have brought forth high quality cost-free or affordable software for many application fields.One of those projects is the open-source desktop planetarium Stellarium. Its original purpose was to visualise the current skies as realistically as possible. With its high quality physics-based sky brightness and colour simulation it gained also high popularity as astronomy outreach tool during IYA2009.Although it was geared towards contemporary amateur astronomers and laypeople, some of its original features, such as its visual quality of simulation and easily exchangeable sky cultures (constellation patterns), as well as its simple usability and free availability, also made the program very attractive to researchers in the fields of historical and also ethnoastronomy. Stellarium has also become a well-known educational tool in schools, colleges, universities and planetariums around the world.A powerful aspect of Stellarium is the possibility to extend the program with plugins for special --- educational or scientific --- purposes without deep changes in the core code. Several of those, including a 3D mode to explore potentially astronomically oriented buildings in their surrounding landscape, have been developed for purposes of visualisation and research in historical astronomy and archaeoastronomy.In this paper we want to highlight several features which can be used to simulate for research, but also and especially for outreach, several transient astronomical phenomena:Solar and Lunar eclipses, Comets, and Supernovae and Novae.
Shallow Transits - Deep Learning: using deep learning to detect habitable planets
Zucker, Shay
Deep learning is currently taking the world of Artificial Intelligence by storm. Deep learning techniques already have proven success in varied fields, such as image processing, speech recognition and even drug discovery. Specifically, deep learning can provide new hope in needle-in-a-haystack problems, such as the detection of very faint signals in the presence of many kinds of noise. Detection of transiting terrestrial planets in the presence of stellar-activity red noise is one such problem. The non-linear nature of deep learning renders it completely different from traditional techniques (such as those based on the BLS). Such innovative approaches will be crucial in order to fully exploit the potential of future planet-detection space missions (TESS, PLATO). We hereby present an extremely short tutorial of what deep learning is, and how it can be applied to detect and analyze transiting terrestrial planets. We also introduce preliminary results of a feasibility study we have performed which demonstrate the immense capability of this novel and exciting approach.
A novel approach to detect periodicity in two-dimensional astrometry
Zucker, Shay
I hereby propose a novel approach to detect periodicities in two-dimensional astrometric data. Periodic astrometric signals are the telltale signs of orbital motion in binary stars and exoplanets. The conventional approach to detect such periodic signals is by first applying the one-dimensional (Generalized) Lomb-Scargle periodogram, separately to each coordinate (right ascension and declination), and then adding the two periodograms to obtain a joint periodogram. This approach has two limitations. First, it is sensitive to the inherent arbitrariness in the definition of the two coordinates: a different coordinate definition will change the obtained periodogram. Second, it is biased towards the detection of circular orbits, which induce pure sinusoidal variability on the two axes. The novel approach I present here is much more suitable and natural to two-dimensional data, and is sensitive to signals which are not necessarily circular. It is based on the newly introduced statistical concept of 'distance correlation', I have recently adapted this concept in order to construct a periodicity search technique for one-dimensional signals - the 'phase distance correlation (PDC) periodogram'. The work I present here is an adaptation of the PDC periodogram to two-dimensional data. The future planned astrometric instruments and space missions will benefit considerably from such a technique, when they address the issue of astrometrically detecting exoplanets, and specifically those with 'exotic' eccentric orbits.
Poster Papers – Div.C
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