Abstracts
| ALONSO-GARCÍA Javier | Oral |
| The VVV survey and its giga-CMD of the inner Milky Way | |
| The Vista Variables in the Vía Láctea (VVV) survey has changed our picture of the inner Galaxy in the last years. The inner regions of our Galaxy are hidden behind a curtain of gas and dust, and their observations at visible wavelengths are severely hampered by this fact. Observations in the near-infrared are better suited due to the diminished effect of extinction at these wavelengths. VVV, one of the six ESO public surveys conducted with the 4m VISTA telescope in Paranal, has observed 562 square degrees of the Galactic bulge and an adjacent region of the southern disk in the Z, Y, J, H, and Ks near-infrared filters during the last 6 years. Using PSF photometry on the VVV images, we have produced a deep and highly complete color-magnitude diagram (CMD) with nearly one billion sources that gives us an unprecedented view of the Galactic bulge and inner disc. In our contribution I will present this CMD and the first results of its analysis. I will talk especially about its implications in terms of structure of the inner Galaxy, the stellar populations residing in it, and the information that can be extracted to determine such fundamental quantities as the weight of the Galactic bulge. I will also mention the possibilities it provides to better understand the reddening law towards the inner Galaxy and to provide high-definition extinction maps. | |
| ANDERSEN Johannes | Oral |
| Non-local Chemical Enrichment in the Early Galaxy | |
| Recent results of multi-year monitoring of extremely metal-poor (EMP; [Fe/H] = ?2.5) stars reveal that stars with large excesses of carbon or r-process elements, but without signatures of s-process elements, are basically single. Their anomalous abundances must therefore be intrinsic and have been implanted in their natal ISM clouds by an external source. Most stars with C and s-process enrichments are binaries, as expected for the scenario of local transfer and dilution of processed matter from a former AGB binary companion, but ~20% appear to be genuinely single. Non-local chemical enrichment must be included in future galaxy evolution models. | |
| AOKI Misa | Poster |
| Sextans Dwarf Galaxy as a Hint to the Evolution of the Milky Way | |
| According to the hierarchical structure formation scenario, small galaxies with various star formation histories have contributed to form larger galaxies, including the Milky Way. Large dispersion in abundance of r-process elements in the metal-poor region of the halo stars is its evidence . Chemical evolution models show that the abundance ratio (e.g., [Ba/Fe]) have different feature depending on the mass of the small galaxy (e.g., Ishimaru, Wanajo, Prantzos 2015). The abundance ratio of neutron-capture elements of dwarf galaxies are expected to be simple, showing clumps instead of smooth dispersion (Bland-Hawthorn et al. 2010). We present the abundance analysis of n-capture elements (e.g., Sr, Ba) of metal-poor stars ([Fe/H]<-2.5) in Sextans dwarf galaxy observed using Subaru Telescope HDS. We discuss the chemical evolution of the dwarf galaxy and the possibility of such small structures building large galaxy by comparing our results to chemical evolution model of the Milky Way. | |
| ARIAS CALLEJAS Veronica | Oral |
| Planes of satellite galaxies: their dynamics and possible origin | |
| The anisotropic distribution of satellite galaxies in the Local Group cannot be readily explained by current galaxy formation models within the $\Lambda$CDM cosmology. In this work we further explore the formation of these observed anisotropic satellite structures in two ways. First, we use dynamical simulations to investigate the possible orbits of satellites around M31 and reinterpret the observations. We find that half of the satellites in the M31 plane could have similar orbits, suggesting a common accretion event. Second, we use halo pairs from the Illustris cosmological simulation to explore the spatial distribution of luminous satellites and dark sub-halos, both in MilkyWay-M31-like pairs and in more general pairs of galaxies. We find that the distribution of luminous satellites is flatter than that of dark matter sub-halos. We also find a discrepancy between observations and simulations on the alignment between the orientation of the main halos and the axis that unites them. | |
| ATHANASSOULA Lia | Oral |
| A disc galaxy model applied to the chemo-dynamics of the bar-bulge region | |
| I will present a disc galaxy model and compare it to observations; mainly spectroscopic observations of the bar-bulge region of the Milky Way, but also radial projected density profiles of the disc component. | |
| BENSBY Thomas | Oral |
| The chemistry of the Milky Way disk | |
| I will talk about the detailed abundance structure of the Milky Way disk. In particular the studies that indicate that the disk most likely contains two distinct disk populations, the thin and thick disks, and the methods to characterise and distinguish between the two. | |
| BERNARD Edouard | Oral |
| Constraints on the stellar mass assembly in Local Group spiral galaxies | |
| I will describe two approaches we have used to determine the nature and origin of both the smooth component and the substructures in the outskirts of the large spiral galaxies of the Local Group. The first one consists in fitting deep colour-magnitude diagrams (CMDs), and allows us to quantify the evolution of the star formation rate and of the metallicity as a function of time. I will first present the star formation history of several fields in the Andromeda (M31) galaxy obtained from deep Hubble Space Telescope CMDs, then discuss on-going work on the application of this technique to a large volume of our own Galaxy with the upcoming Gaia data. The other approach is based on the pulsational properties of RR Lyrae (RRL) variable stars. The period and amplitude distributions of RRL stars show distinctive features in different types of stellar systems, reflecting the parent stellar populations properties. I will show that High Amplitude Short Period (HASP) variables are common in the halos of the Milky Way and M31, in globular clusters with [Fe/H]>-1.5 and in massive dwarfs, but are not found in low metallicity globular clusters nor in faint dwarf galaxies, suggesting that more-massive dwarfs are the dominant building blocks of these stellar halo. | |
| BIRD Sarah | Poster |
| Halo K-Giant Stars from LAMOST: Kinematics and Galactic Mass Estimate | |
| We analyze line-of-sight velocities of over 3000 halo K-giant stars from the second data release of the spectral survey LAMOST. We find a nearly constant line-of-sight velocity dispersion profile, no large dips or peaks, in a Galactocentric radial range of 10 to 30 kpc, where such dips have been seen in other surveys. We use the stars to make estimates of the enclosed mass out to 40 kpc from the Galactic Center. Tens of thousands of such stars are expected to become available to this analysis by the end of the five year survey. | |
| BIRD Jonathan | Oral |
| Insights into the Vertical Structure of Disk Galaxies from the Milky Way | |
| Will add. | |
| BONO Giuseppe | Oral |
| The metallicity distribution of the Galactic thin disk and of the halo using classical Cepheids and RR Lyrae stars now and in the E-ELT era | |
| We present new results concerning the radial gradients (Fe, alpha, s- and r-process elements) across the Galactic thin disk. We use young (t<300 Myr, classical Cepheids) stellar tracers for which we collected high resolution spectra with UVES at VLT together with similar estimates available in the literature. The investigated elements display well defined negative gradients when moving from the innermost to the outermost regions. Moreover, we also found that the radial gradients of the neutron capture elements are positive as a function of age (pulsation period). Thus suggesting an age dependence similar to alpha elements. On the other hand, the slopes of [elements/Fe] vs Galactocentric distance are more positive than for alpha-elements. We discuss plausible working hypotheses to take account of the difference, and perform a detailed comparison with similar abundances for dwarf and giant stars available in the literature. We also discuss the abundance ratio between s- and r-process elements (La/Eu) and between heavy and light s-process elements (La/Y) and outline their impact on the chemical enrichment history of the Galactic thin disk. Finally, we present new results concerning the iron gradient of the Galactic halo using old (t>10 Gyr, RR Lyrae) stellar tracers for which we collected high-resolution spectra with UVES at VLT together with metallicity estimates based on low-resolution spectra available in the literature. We discuss the difference with the metallicity gradient and spread in metallicity of the M31 halo and the impact on their early formation and evolution. We also outline the role that the first generation of spectrographs at E-ELT is going to play on Galaxy formation and on its chemical enrichment. | |
| BONOLI Silvia | Poster |
| Massive black hole evolution and the formation of a B/P bulge in a Milky Way galaxy | |
| I will present the results of the zoom-in hydrodynamical simulation "ErisBH", a twin simulation of the Milky Way-analog "Eris", with which it shares the same initial conditions, resolution (120 pc) and physical simulated processes, but it includes also prescriptions for the growth and feedback of massive black holes. We find that the galaxy's central black hole grows mainly through mergers with other black holes and very little by gas accretion. The feedback on the host galaxy is weak, and only influences the very center of the host. Yet, this modest feedback limits the growth of the bulge. Because of its smaller bulge and larger disk, ErisBH is more prone to instabilities than Eris and, at z~0.3, an initially small bar grows to be of a few disk scale-lengths in size. The formation of the bar causes a small burst of star formation in the inner few hundred pc, provides new gas to the central black hole and causes the bulge to have a B/P morphology by z=0. | |
| BOVY Jo | Oral |
| The structure of the Milky way disk | |
| Observations of the structure and dynamics of different stellar populations in the Milky Way's disk provide a unique perspective on Galactic growth, evolution, and dynamics over cosmic time. I will review our current knowledge of the chemo-orbital structure of the disk and the major outstanding questions. I will then discuss new measurements of the kinematics and chemistry of stars over a large part of the Galactic disk from the APOGEE survey and the new insights these measurements provide about the formation and evolution of the Milky Way’s disk. | |
| BROWN Anthony | Oral |
| Gaia First Vintage | |
| At about 1000 days after the launch of Gaia the first Gaia data release, Gaia DR1, was delivered on September 14, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. | |
| BUCK Tobias | Poster |
| Clumpy discs or clumpy starformation? Results from the NIHAO simulations. | |
| I work with the NIHAO simulations suite, the largest homogeneous sample of high resolution cosmological simulations, counting more than 90 galaxies. I am specifically looking at the morphology and clumpiness of the stellar and gaseous discs from redshift two to the present day. Observations have shown evidence for large star forming clumps in the discs of high redshift galaxies as for example in the CANDLES survey, where these clumps are clearly visible in the UV part of the spectrum. Using the NIHAO similations I am studying the properties of these clumps, their origin and their life time. I will also present results based on a new set of even higher resolution galaxies. Overall, on the contrary of some previous results, our simulations seem to indicate that these clumps are short lived and possibly not self bound, suggesting that high redshift galaxies have clumpy star formation more than clumpy discs. | |
| CARBALLO-BELLO Julio A. | Poster |
| Whiting1: confirmation of its accretion by the Milky Way | |
| Globular clusters have played an important role in the study of the processes that led to the formation of our Galaxy. Moreover, the dual Galactic globular cluster system is considered a manifestation of its hierarchical formation in the context of the Lambda-CDM scenario. Wide-field imaging and spectroscopy, as the one obtained for our project, are crucial tools to unveil the remnants of their progenitor dwarf galaxies, already assimilated by the Milky Way. In this poster, we present our results for Whiting1, where MOS spectroscopy reveals the presence of a component of the Sagittarius tidal stream with a radial velocity – and distance – compatible with that of the globular cluster. We conclude that Whiting1 was formed in the interior of the Sagittarius dSph and later accreted by the Milky Way. | |
| CASETTI Dana | Oral |
| Recent Star Formation in the Leading Arm of the Magellanic Stream | |
| Kinematics and chemical abundances from high resolution spectra are presented for a set of eight young, newly-formed stars located in the Leading Arm (LA) of the Magellanic Stream, and at the edge of the Milky Way disk. We find evidence that chemical abundances are different for four stars that are the most distant and kinematically compatible with membership to the LA when compared to the remaining four. We will discuss these results in the context of the interaction of the Magellanic System withe the Milky Way disk. | |
| CHERNIN Arthur | Poster |
| Dark energy in the environment of the Milky Way | |
| Dark energy in the environment of the Milky Way Arthur D. Chernin Sternberg Astronomical Institute, Moscow University, Russia Arthur.Chernin@gmail.com The extended environment of the MW involves the Local Group of ~2 Mpc across and the Local Flow of ~5 Mpc across around it. The both are imbedded in the uniform background of omnipresent dark energy. The group is affected by the active antigravitating dark-energy mass which is near (in absolute value) the matter mass of group's galaxies. The group and the flow together are affected by the dark-energy active mass which is ~10 times (in absolute value) the matter mass of the system. These estimates imply that dark-energy local antigravity is strong enough to be an effective driver of the formation and evolution of the MW environment. The HST recent data together with our analytical and computer models suggest also that the MW, the group and the flow might have a common origin due to gravity-antigravity interplay on the space scale of a few Mpc. A similar structure observed with the HST in several other local systems of the same scale shows that this dynamical mechanism may have a universal character in the local universe. | |
| CIAMBUR Bogdan | Poster |
| The Milky Way's Bulge in the Context of Nearby (X/Peanut)-Bulge Galaxies | |
| X-shaped or peanut-shaped (X/P) bulges are observed in more than 40 per cent of (nearly) edge-on disc galaxies, as well as in the Milky Way's own bulge. Using Fourier harmonics to describe the deviation of galaxy isophotes from ellipses, I will present five quantitative diagnostics of the X/P structure, namely: its `peak' amplitude (?max); the (projected major-axis) `length' where this peak occurs (R?, max); its vertical `height' above the disc plane (z?, max); a measure of the B6 profile's integrated `strength' (S?); and the B6 peak `width' (W?). In this talk I will present these diagnostics for a sample of 11 such galaxies. Additionally, I will present the detection and measurement of the properties of multiple (nested) X/P structures in individual galaxies which additionally display the signatures of multiple bars in their surface brightness profiles, thus consolidating further the scenario in which peanuts are associated with bars. I will reveal that the peanut parameter space (`length', `strength' and `height') for real galaxies is not randomly populated, but the three metrics are inter-correlated (both in kpc and disc scalel ength h). Additionally, the X/P `length' and `strength' appear to correlate with (v_rot/s?), lending further support to the notion that peanuts `know' about the galactic disc in which they reside. Such constraints are important for numerical simulations, as they provide a direct link between peanuts and their host disc. Moreover, nested peanuts, as remnants of bar buckling events, can provide insights into the disc and bar instability history. I will finally present an analysis of the Milky Way's peanut bulge in this context. | |
| COMBES Francoise | Oral |
| Thick and thin disks | |
| This will be a contribution to animate the panel, to debate on the origin of thick and thin disks | |
| DAME Thomas | Oral |
| Mapping Spiral Structure with Trigonometry | |
| While we now know the distances of galaxies at the edge of the Universe,we have only just begun to measure distances accurately throughout theMilky Way. Using Very Long Baseline Interferometry, we have achieved parallax accuracies of 10 micro-arcseconds. I will present results of hundreds of parallaxes and 3-D motions of star forming regions from the BeSSeL Survey and the Japanese VERA project. These measurements directly trace the spiral structure of the Milky Way, leading to the first visualization of what it would look like viewed from outside the Galaxy. Modeling the 3-D motions with accurate distances tightly constrains the fundamental parameters (the distance to the Galactic Center and the rotation speed at the Sun) of the Milky Way. | |
| DE LAVERNY Patrick | Oral |
| The AMBRE Project : chemical tagging of the Galactic disc | |
| From the parametrisation of ESO archive spectra, the AMBRE Projet (de Laverny et al., 2013) has chemically characterized about 8,000 stars in lithium, iron and alpha-element abundances and, for ~5,000 of them, their abundances in Mn, Ni, Cu, Zn and some s-elements have also been derived. For most of these targets, astrometric informations from the Gaia DR1 will be also available. From this unique sample, we have derived informations about the different chemical histories of the thin and thick discs. Some comparisons with current chemical models of the Milky Way reveal strong disagreements probably caused by uncertain stellar yields and chemical histories together with different assumed IMF and/or SFR in both discs. | |
| DI MATTEO Paola | Oral |
| Finding stellar streams in the Milky Way halo : a challenge for Gaia | |
| ?CDM models predict indeed that a galaxy like the Milky Way should contain hundreds of stellar streams at the solar vicinity, relics of the merging over time of other galactic systems, with masses comparable or significantly smaller than our own Galaxy at the time of their accretion. Numerous studies in the last fifteen years have suggested that the imprints of past merger events, even if dispersed in configuration space, can still be identified in kinematics-related spaces. From the number of clumps found in those spaces for several million Gaia stars, it should be potentially possible to set a lower limit to the number of past accretion events. But is this search really feasible ? What does an over density in those spaces really mean ? Can we realistically make use of the number of substructures found to set a lower limit to the number of merger events that the Galaxy experienced in its past ? In this talk, we will address these questions, by means of high resolution N-body simulations of a Milky Way- type galaxy which accretes one or several satellites. We will show how, differently from previous findings, kinematics-related spaces become hardly decipherable when some of the most limiting assumptions which have affected previous works are removed. Detailed chemical abundances and/or ages will be definitely necessary to identify stellar streams, that should show up as distinct patterns from those described by the in-situ stellar populations. | |
| DIEHL Roland | Oral |
| Radioactivity gamma rays and the Galaxy's large scale structure | |
| Measurements of galactic diffuse radioactivity in 26Al gamma rays with INTEGRAL have shown a peculiar longitude-velocity signature. This was understood to suggest that cavities at the leading edges of spiral arms were the main locations of the sources injecting 26Al nucleosynthesis ejecta into the ISM. We discuss latest updates of these measurements and their implications. | |
| D'ONGHIA Elena | Oral |
| The imprint of radial migration on the vertical structure of galaxy disks | |
| A set of numerical simulations has been used to examine the effects of radial migration on the vertical structure of galaxy disks. The disks develop different non-axisymmetric patterns, ranging from long-lived multiple arms to strong, rapidly-evolving few-armed spirals. These fluctuations induce radial migration through secular changes in the angular momentum of disk stars, mixing the disk radially and blurring pre-existing gradients. Migration affects primarily stars with small vertical excursions, regardless of spiral pattern. This "provenance bias" largely determines the vertical structure of migrating stars: inward migrators thin down as they move in, whereas outward migrators do not thicken up but rather preserve the disk scale height at destination. Migrators of equal birth radius thus develop a strong scale-height gradient, not by flaring out as commonly assumed, but by thinning down as they spread inward. Similar gradients have been observed for low-[ /Fe] mono-abundance populations (MAPs) in the Galaxy but our results argue against interpreting them as a consequence of radial migration. I will show that the bombardment of the disk with dark satellites as predicted by cosmological simulations might be more effective in reproducing the observed gradients. | |
| DURAN Sivan | Poster |
| Searching for the Galactic Bar with Near- and Mid-Infrared | |
| The bars have an important role in the galaxy evolution and structure. It has long been known that the Milky Way has a bar. However, authors have given different values for the structural parameters such as position angle, half length. In this study, we investigate the structure of the Galactic bar using the red clump giants (RCGs) with 2MASS and WISE photometries. In order to separate the RCGs in the direction of the Galactic bar, we used the Galaxia model and calculated the extinctions and distances of the RCGs in each star field. We computed the half length and the position angle for the bar using Markov Chain Monte Carlo simulation 4.1+/-0.1 kpc and 39.4+/-0\8 degrees, respectively. | |
| DURMUS Duygu | Poster |
| A Exoplanet from out of Milkyway | |
| Our research aims to investigate exoplanets' host stars' population analysis and possible Galactic origin with the help of recent data from NASA exoplanet archive. After NASA exoplanet archive was matched to Adibekyan et al. (2012)'s online data, we obtained the database of 123 exoplanets' host stars' atmospheric model parameters, space velocities, element abundances and 163 exoplanets' orbital and structural parameters. We calculated Galactic orbital parameters of 123 host stars from our database. Our sample stars may de ne the Solar Neigbourhood because all stars' distances are less than 1 kpc. We defi ned the Solar Neigbourhood by using the following constraints: ep less than 0.1, Zmax less than 825 pc (Plevne et al. 2015) and [Fe/H] > 0.2 dex (Vande Putte et al. 2010). We concluded that one host star's origin may be extragalactic, because this star does not any constraints for thin disk, thick disk and halo. | |
| ELMEGREEN Bruce | Oral |
| Some thoughts on the evolution of thick disks and the Milky Way: where to go from here? | |
| The thick disks of the Milky Way and other galaxies appear to have formed at about the same time as the bulge or thick bar regions when galaxies were actively accreting gas, highly turbulent, and clumpy with giant star-forming and gaseous complexes. In this talk, the properties of clumpy galaxies, thick disks, and the relations between these components and bulges will be reviewed, along with theories for the origin of each component and their relation to the Milky Way. | |
| FAMAEY Benoit | Oral |
| Modelling the Galactic disc: the effect of spiral arms in action-angle coordinates | |
| Current Galactic dynamical models still often rely on the assumptions of a smooth time-independent and axisymmetric gravitational potential, while more involved ab initio simulations in a cosmological context are not very flexible. First order perturbed models are those trying to isolate the effects of one main perturber, such as the bar or the spiral arms. We provide here for the first time analytic forms of distribution functions in angle-action coordinates, representing the thin disc and rigorously taking into account the response to a spiral potential through the linearized Boltzmann equation. Various effects such as non-zero mean vertical and radial stellar motions, as well as moving groups, are unified within this framework. We show that this will be of fundamental importance for determining fundamental Galactic parameters in an unbiased way. | |
| FRAGKOUDI Francesca | Oral |
| Bars and boxy/peanut bulges in thick discs | |
| In this talk we will present the results of N-body simulations of (thin+thick) disc galaxies which evolve secularly. We will show how thin and thick discs are mapped into a boxy/peanut (b/p) shaped bulge, how the weight of the two populations changes along the b/p structure and the resulting main kinematic characteristics. Furthermore we will show how different mass thick discs affect the bar and b/p strength. We will discuss these results in light of the properties of the Milky Way bulge, and of the chemo-kinematic relations satisfied by its main stellar populations. | |
| FRANÇOIS Patrick | Poster |
| Chemical composition of a sample of stars in ultra faint dwarf galaxies | |
| We report the analysis of a sample of 11 stars belonging to 5 different ultra faint dwarf galaxies. Our results are compared to the abundances ratios found in halo stars and stars from dwarf spheroidal galaxies. Considering all the stars observed in ultra faint dwarf galaxies as representative of the same population of low mass galaxies, we found that the [alpha/Fe] ratios vs [Fe/H] decreases as the metallicity of the star increases. The main difference is that the solar [alpha/Fe] is reached at a much lower metallicity for the UfDSph than the dwarf spheroidal galaxies. We also report abundances of Ba and Sr in several stars. | |
| FRATERNALI Filippo | Oral |
| Gas accretion and its impact on the evolution of the Milky Way | |
| The evolution of the Milky Way, and its thin disc in particular, is a history of continuous accretion of fresh gas from the surrounding environment. Most of the evidence of this accretion is indirect coming from the chemical composition of gas and stars in our Galaxy. In recent years, observations have shown that the Milky Way, like any galaxy, is surrounded by a massive circum-galactic medium (CGM) containing a large amount of multiphase gas. To understand how this gas falls and accretes into the disc to feed the star formation we must understand the complex physics of the interphase between the disc and the CGM. I present theoretical work and hydrodynamical simulations aimed to address this issue. The challenge will be to derive the history of gas accretion, where it occurs and with what physical properties (for instance its angular momentum), to be build a self-consistent model of chemical and structural evolution of the Galactic gaseous and stellar discs. | |
| FREEMAN Ken | Oral |
| The Milky way and its components: overview | |
| I will discuss the main components of the Milky Way: the thin and thick disks, the bulge, and the stellar halo, hot halo and dark halo. Each component is important as part of the narrative about how disk galaxies are assembled and evolve, chemically and dynamically. Recent observations of disk galaxies at high redshift may modify some of our ideas about the early evolution of disk galaxi | |
| FRENK Carlos | Oral |
| Clues to the identity of the dark matter in the Milky Way | |
| A commonly-held belief is that the standard cold dark matter model faces four ``challenges'' on small scales referred to as the (i) core-cusp; (ii) missing satellites; (iii) too-big-to-fail; (iv) satellite planes problems. I will report on results on these four challenges from recent high resolution N-body hydrodynamics simulations of Local Group analogues which are part of the Evolution of Galaxies and their Environment (EAGLE) project. The inclusion of baryons in the simulations has important consequences for several of these topics. | |
| GARRISON-KIMMEL Shea | Oral |
| Fake it 'til you make it: Accurate Predictions for Substructure Populations with Embedded Potentials | |
| Among the most important goals in cosmology today is detecting and quantifying small (Mhalo ? 106-9M?) dark matter subhalos around the Milky Way (MW) and other galaxies. Current probes are most sensitive to substructure within ~ 20 kpc of a halo center, where the central galaxy contributes significantly to the overall potential. We explore ?CDM predictions for subhalos using cosmological zoom-in simulations of two MW-mass halos from the Latte Project. Each halo is simulated in three ways: dark matter only (DMO), full baryonic physics using Feedback in Realistic Environments (FIRE), and dark matter with an embedded, evolving disk potential for the central galaxy. Relative to baryonic simulations, DMO simulations over-predict the abundance of subhalos by ~ 2× within 100 kpc of the halo center and by 5× within 25 kpc. At z = 0, our baryonic simulations are completely devoid of subhalos down to 3 × 106 M? within 15 kpc of the central galaxy. The simple inclusion of an embedded central galaxy potential reproduces this subhalo depletion, including trends with radius, remarkably well. Thus, the central galaxy’s tidal field is the primary cause of subhalo depletion. Subhalos on radial orbits that pass close to halo center are preferentially destroyed, so the resultant orbits of surviving subhalos are tangentially biased compared with DMO. Our method of embedding a disk potential in dark matter simulations provides a fast but accurate alternative to full baryonic physics, thus enabling large suites of cosmological zoom-in simulations to provide accurate and statistical predictions for observations. | |
| GONZALEZ DELGADO Rosa | Oral |
| Stellar population properties of disc galaxies in the local universe | |
| In this talk I will present the results obtained for nearly 500 disk galaxies of the local universe observed in the CALIFA survey. We perform full spectral synthesis to get the spatial resolve stellar population properties of the galaxies. The results are discussed as a function of the Hubble type and galaxy mass. | |
| GRAND Rob | Oral |
| The formation and evolution of Milky Way sized galaxies in high-resolution cosmological zoom simulations | |
| Simulations are playing an increasingly important role in probing the formation history of the Milky Way. We present the Auriga project, a suite of 30 cosmological zoom simulations of MW sized galaxies with unprecedented resolution simulated with the state-of-the-art magneto-hydrodynamics code AREPO and a comprehensive galaxy formation model that successfully reproduces many properties of real galaxy populations. The simulations follow the full cosmic evolution of Milky Way progenitors into thin, rotationally supported discs that exhibit well-resolved bar and spiral structure. We analyse the impact of a multitude of galaxy formation processes on the build up of the disc and bulge such as gas accretion, stellar/AGN feedback, satellite interactions, mergers and secular internal processes linked to bars and spirals. In particular, we show that thickened disc components are mainly driven by a bar (if present) and interactions with satellites of masses log10 (M/ M? ) >= 10, whereas other potential heating mechanisms such as spiral arms, radial migration, and adiabatic heating from mid-plane density growth are all sub-dominant. In nearly all simulations the overall structure of the disc becomes gradually more radially extended and vertically thinner with time, in support of the inside-out, upside-down formation scenario, and without the presence of a thin/thick disc dichotomy. In addition, we comment on the mass distribution of mono-abundance populations and their relation to the bulge and disc components, which are readily comparable to observations from surveys such as APOGEE and Gaia. Finally, we comment on kinematic and metallicity signatures of large-scale, spiral-driven radial migration found in the simulations, and the potential observational predictions of spiral arm nature that they constitute. | |
| GREBEL Eva | Oral |
| Fossils of Galaxy Evolution: What the Milky Way Satellites Tell Us | |
| The Milky Way is surrounded by a large entourage of satellites covering a wide range of luminosities, masses, and star formation histories, and newly discovered ultra-faint satellites continue to be added. All of these galaxies are close enough to be resolved into stars, allowing us to conduct highly detailed "galactic archaeology" of their star formation histories, chemical evolution, and dynamical evolution. All of these satellites contain old, metal-poor stellar populations, providing unique insights in the early stages of star formation and chemical enrichment in small dark matter halos at high redshift. The current satellites are the survivors of a once much more numerous population of since accreted Galactic building blocks that contributed to the build-up particularly of the Galactic halo. Hence their characterization holds important clues on the evolutionary history of our Milky Way itself. | |
| GRILLMAIR Carl | Oral |
| Untangling the Web | |
| Dozens of stellar debris streams have now been found in the Milky Way halo. We discuss some of the most recent discoveries and how they may challenge our ideas on the formation of our Galaxy. | |
| GROSBOEL Preben | Poster |
| On the distribution of early-type stars toward the Galactic center | |
| A catalog of ~10k early-type candidate stars with a limiting magnitude of B<14.5 mag in a 100 square deg. field toward the Galactic center was produced based on objective prism spectra from the ESO Schmidt telescope at La Silla, Chile (Grosboel, 2016, A&A 585, A141). The spectra allowed to estimate individual extinctions and distances of the candidate stars indicating that the sample reaches distances of 2 kpc from the sun i.e. beyond the Sagittarius arm. The spatial distribution of the early-type candidates is discussed in the poster. | |
| HAGEN Jorrit | Poster |
| Axisymmetric orbit-based models of a mock dwarf spheroidal galaxy | |
| In this work we use the Schwarzschild’s orbital superposition method to measure the mass content, shape and internal orbital structure of a Sculptor-like Dwarf Spheroidal Galaxy. Most studies have assumed spherical symmetries, whereas we adopt a more general axisymmetric modelling. We construct a mock galaxy whose properties might resemble those of the Sculptor dwarf spheroidal galaxy. Its global potential follows a logarithmic profile for the global potential. We show that our method can reproduce the light distribution and the stellar kinematics of our mock galaxy and that we can recover the true characteristic parameters of its potential when pretending to observe 10^4 simulated stars in a known edge-on view. Finally, we change to an inclined view towards the mock galaxy and we show that we can constrain the mass, scale radius, flattening and inclination of the system by assuming an axisymmetric NFW-like potential form, though the mass is the only well constrained parameter. | |
| HAMMER Francois | Oral |
| The Magellanic Stream: two ram-pressure tails and the relics of the collision between the Magellanic Clouds | |
| We have analysed the Magellanic Stream (MS) using GASS, which is the deepest and the most resolved HI survey of the Southern Hemisphere. Along all its length, the Stream is structured into two filaments suggesting two ram-pressure tails lagging behind the Magellanic Clouds (MCs). The past motions of the Clouds appear imprinted in them, implying almost parallel initial orbits, and then a radical change after their passage near the N(HI) peak of the MS. This is consistent with a recent collision between the MCs, 200-300 Myr ago, which has stripped further their gas into small clouds, spreading them out along a gigantic bow-shock, perpendicular to the MS. The corresponding hydrodynamical modelling reproduces the MS morphological distribution, its velocity and column density. It is consistent with a Milky Way (MW) halo hot gas of $n_h$= $10^{-4}$ $cm^{-3}$ at 50-70 kpc, a value necessary for explaining the MS multiphase HVCs. The Stream filamentary structure is expected to survive KH instabilities. Impacts of this scenario to high velocity clouds and to the gas accretion by our Galaxy are discussed. | |
| HAYDEN Michael | Oral |
| Chemical Cartography of the Milky Way Disk | |
| We use the SDSS-III/APOGEE and the Gaia-ESO spectroscopic surveys to study the chemical and kinematic structure of the Milky Way and look for signatures of radial migration in the disk. Using APOGEE observations taken from DR12, we studied the stellar distribution in the [$alpha$/Fe] versus [Fe/H] plane as a function of Galactocentric radius and height above the plane. We find that the high-$alpha$ populations appear similar at all locations throughout the disk, while the low-$alpha$ populations have a large variation with location throughout the disk, with the inner disk being metal-rich while the outer disk made up of metal-poor stellar populations. In the inner disk, it is possible that the high- and low-$\alpha$ populations are linked, as the two populations appear as a single sequence in the [$\alpha$/Fe] vs. [Fe/H] plane. We use APOGEE observations to measure the metallicity distribution function (MDF) across the disk, and find that the peak and skewness of the MDF is a strong function of location in the disk. The MDF of the inner Galaxy is metal-rich with a negative skewness, while the MDF of the outer disk is metal-poor and has a positively skewed distribution. We apply a simple distribution function model to the data and find that blurring alone is unable to explain the change in skewness of the MDF with location, while the addition of radial migration to the model is able to reproduce the observed MDFs. Using observations from the Gaia-ESO survey, we attempt to quantify the relative fraction of stars that undergo migration. We determine the orbital properties of metal-rich ([Fe/H]>0.1) stars in the solar neighborhood, and find that one quarter of these stars have perigalictons Rp>7 kpc, and never approach the radii at which they were likely formed based on their metallicity. Additionally, more than half of the metal-rich stars have eccentricities less than 0.2 and are on roughly circular orbits. | |
| HAYWOOD Misha | Oral |
| Phylogeny of the inner disk and bulge stellar populations. | |
| We show that the chemical patterns of the inner disk and bulge of the Milky Way can be reproduced by the same Galactic chemical evolution modeling, suggesting that they are essentially the same population. This shared history implies that most of the old stellar mass of our Galaxy formed from massive gas accretion early in Galactic history, formally described by a closed-box model. We advocate that the solar vicinity, at the edge of the inner disk, shows obvious patterns of this closed-box type evolution, but being at the interface between the inner and outer stellar disks, is numerically dominated by stars which formed from a mixed of metal-enriched gas from the inner disk and metal-poorer gas from the outer disk. | |
| HENSLER Gerhard | Oral |
| Gas assembly of galaxies - the shape and survival of high-velocity clouds | |
| That the assembly of gas is the main driver of galaxy evolution is a generally accorded scenario. However, whether it happened dominantly by smooth accretion from their gaseous circum-galactic environment and/or by stochastic filamentary gas inflow from the cosmic web is a not yet solved question. Moreover, how the infalling cold gas can penetrate through hot halo gas in order to feed a gaseous disk and, by this, to keep star formation alive, is a widely ignored problem, although in our and other local galaxies infalling gas is observed as high-velocity clouds (HVCs). In contrary, in most numerical models HVCs are destroyed by hydrodynamical instabilities, whereas observed HVC complexes that are approaching the galactic disk must have suvived. They are not only massive enough to be stabilized by self-gravity, but also experience thermal conduction from the hot halo gas what suppresses Kelvin-Helmholtz instability (KHI). We present high-resolution 3D numerical simulations of HVCs with different masses and velocities in order to explore the action of self-gravity vs. Bernoulli effect and ram pressure, thermal conduction vs. KHI, and the shape of HVCs in comparison to observations. | |
| HIDALGO Sebastian | Oral |
| The Art of Deriving SFHs: From Dwarf Galaxies to the Milky Way. | |
| In this talk I will show how to obtain star formation histories (SFHs) from resolved stellar populations using a color-magnitude (CMD) fitting technique. The developed algorithm compares the star distribution in an observed CMD with the distribution of the stellar populations in a synthetic CMD, in which observational effects have been simulated. This procedure has been apply to a large number of dwarf galaxies of the Local Group to obtain the SFHs for all the lifetime of the galaxies. The results show that these galaxies show radial gradients, pointing to an outside-in scenario of galaxy formation. UV-background at the Epoch of Reionization may have played a role but only in the outskirts of some of the less massive dwarf galaxies. Finally, a new project to obtain the SFHs of the bulge and disk of the Milky Way using the ESO-VVV survey is presented. | |
| HILL Vanessa | Oral |
| Metal-poor stars in the Galactic Halo and beyond | |
| HIRAI Yutaka | Poster |
| Towards understanding the Milky Way formation: Insight from the enrichment of r-process elements | |
| The abundance of r-process elements of stars in the Milky Way (MW) provides clues to clarify early evolutionary history of galaxies. Astronomical high dispersion observations show that metal-poor stars in the MW halo have large star-to-star scatters of the distribution of r-process elements. Neutron star mergers (NSMs) are one of the most promising sites of r-process. However, it has been suggested that the merger time scale of NSMs is too long to reproduce the observed scatters. In this study, we performed a series of N- body/hydrodynamic simulations of the MW progenitor galaxies. We show that the scatters can be explained by NSMs due to slow chemical enrichment of such galaxies. This results suggests that stars in the MW halo formed with a star formation rate of less than 10^-3 Msun/yr. We also find that the dynamical time of haloes affects early evolutionary history of galaxies. We successfully show that early enrichment of the MW halo occurred in the framework of hierarchical structure formation. | |
| HUANG Yang | Oral |
| The Milky Way’s rotation curve out to 100 kpc and its constraint on the Galactic mass distribution | |
| The rotation curve (RC) of the Milky Way out to ~100kpc has been constructed using~ 16, 000 primary red clump giants (PRCGs) in the outer disk selected from the LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC) and the SDSS-III/APOGEE survey, combined with ~ 5700 halo K giants (HKGs) selected from the SDSS/SEGUE survey. To derive the RC, the PRCG sample of the warm disc population (with a radial velocity dispersion sR ˜ 25–35 km/s ) and the HKG sample of the halo stellar population are respectively analyzed using a kinematical model allowing for the asymmetric drift corrections and with the spherical Jeans equation. The typical uncertainties of RC, including both random and systematic errors, derived from the PRCG and HKG samples are respectively 5-7 km/s and several tens km/s. We determine a circular velocity at the solar position, Vc(R0) = 240 ± 6 km/s and anazimuthal peculiar speed of the Sun, V? = 12.1±7.6 km/s, both in good agreement with the previous determinations. The newly constructed RC has a generally flat value of 240 km/s within a Galactocentric distance r of 25 kpc and then decreases steadily to 150 km/s at r ~ 100 kpc. On top of this overall trend, the RC exhibits two prominent localized dips, one at r ~ 11 kpc and another at r ~ 19 kpc. The dips could be explained by assuming the existence of two massive (dark) matter rings in the Galactic plane. From the newly constructed RC, combined with other data, we have built a parametrized mass model for the Galaxy, yielding a virial mass of the Milky Way’s dark matter halo of (0.90±0.07) × 10^12 M?, a concentration parameter c = 18.06 and a total disc mass of (4.32±0.80) × 10^10 M?. The model yields a local dark matter density, ??,dm = 0.32±0.02 GeV/cm^3, which again agrees well with the previous determinations. | |
| IBATA Rodrigo | Oral |
| Properties of the Local Group | |
| I will present the large-scale structure and dynamics of the Local Group, and discuss the curious phase-space correlations exhibited by the members of this ensemble. Our Local Group is largely dominated by the halos of the Milky Way and Andromeda, so my review will also touch upon recent work that is trying to improve our understanding of the structure and kinematics of stellar halos, aiming to reveal the properties of the underlying dark matter. | |
| INUTSUKA Shu-ichiro | Oral |
| Phase Transition Dynamics of ISM: A Unified Picture of Galactic Star Formation | |
| We propose a unified picture of star formation in the disk galaxies. Recent high-resolution magneto-hydrodynamical simulations of phase transition dynamics with cooling/heating and thermal conduction have shown that the formation of molecular clouds requires multiple episodes of supersonic compression. This finding enables us to create a new scenario of molecular cloud formation as the interacting shells or bubbles in galactic scale, which explains many observational properties such cloud-to-cloud velocity dispersions, accelerating star formation, and very low star formation efficiencies in filamentary molecular clouds. We estimate the ensemble-averaged growth rate of individual molecular clouds, and predict the associated cloud mass function. Cloud-cloud collisions as a mechanism for forming massive stars and star clusters can be naturally accommodated in this scenario. This explains why massive stars formed in cloud-cloud collisions follows the power-law slope of the mass function of molecular cloud cores repeatedly found in low-mass star forming regions. | |
| ISHIMARU Yuhri | Oral |
| Chemical Evolution of the Galactic Halo with Neutron Star Mergers Based on the Sub-Halo Clustering Scenario | |
| Neutron star mergers (NSMs) are suggested to be major sites of r-process elements in the Galaxy by recent hydrodynamical and nucleosynthesis studies (e.g., Wanajo+ 2014), although it has been pointed out that the lifetimes of NSMs are in conflict with the presence of r-process enhanced halo stars (Argast+ 2014). We examine the role of NSMs in the early Galactic chemical evolution on the assumption that the Galactic halo was formed from merging sub-halos. We find that NSMs can well explain the observed abundance ratios [r/Fe] of the Galactic halo stars, if the star formation efficiencies are smaller for less massive sub-halos (Ishimaru, Wanajo, Prantzos 2015). In particular, we show that smaller numbers of NSMs for less massive sub-halos could cause the observed large dispersions in [r/Fe], using a stochastic chemical evolution model of sub-halos. This result is consistent with the recent observation of the ultra-faint galaxy, Reticulum 2 (Roederer+ 2016, Ji+2016). | |
| JETHWA Prashin | Oral |
| A Magellanic Origin of the DES Dwarfs | |
| We establish the connection between the Magellanic Clouds (MCs) and the dwarf galaxy candidates discovered in the Dark Energy Survey (DES) by building a dynamical model of the MC satellite populations, based on an extensive suite of numerical simulations. Our model takes into account the response of the Galaxy to the MCs, the dynamical friction experienced by the MCs, and samples over the uncertainties in the MCs' proper motions and masses. Assuming that MW dwarfs follow the distribution of subhaloes in LambdaCMD, we show that (i) of 14 observed satellites, the MW halo contributes fewer than 4 (8) of these with 68% (95%) confidence and that 7 (12) DES dwarfs have probabilities greater than 0.7 (0.5) of belonging to the LMC, (ii) the LMC has most likely undergone exactly one Galactic pericentric passage, (iii) the total number of the Magellanic satellites is ~70. We will then discuss the likelihood of a Magellanic origin for previously known Galactic satellites. | |
| JOFRE Paola | Poster |
| Stellar genetics: reconstructing the history of the solar neighbourhood with an evolutionary tree | |
| Using chemical abundances of solar twins, we construct an evolutionary tree to study the relationships of stars in the solar neighbourhood. We show that this way of visualising the data allows us to disentangle the different stellar populations without the need for additional cuts in kinematics, age or chemistry. The tree also enables us to compare chemical enrichment rates and importance of dynamical processes between stellar populations. | |
| JOHNSTON Kathryn | Oral |
| The Dark and Stellar Halos of the Milky Way - Origins and Structures | |
| This talk will discuss ongoing investigations on aspects of halo formation and structure: contributions to the halo from stars born in the Galactic disk; observable signatures of chaotic and regular orbits in halo substructure; and implications from both of these for the structure of the dark matter halo. | |
| KATZ David | Poster |
| Gaia first vintage | |
| D. Katz, C. Babusiaux, F. Arenou End of July 2016, Gaia will have completed its second year of nominal mission at L2. The first data release is planned for the end of the Summer and may almost coincide with the workshop. Gaia-DR1 will contain, subject to successful validation, positions and magnitudes for about a billion stars, photometric data for Cepheids and RR-Lyrae in the directions of the ecliptic poles and the TGAS stars, i.e. roughly 2 millions stars for which the combined Tycho2-Gaia solution will provide parallaxes and proper-motions. These first 2 millions distances carry the promise for a first significant step forward in our understanding of the Milky-Way. In this talk, we will present the status of Gaia after 2.5 years in space, the content and properties of the first data release, where and how to access the data. What to do with these data will be up to the audience... | |
| KAWATA Daisuke | Oral |
| Impacts of Radial Migration on the Galactic Thick and Thin Disks | |
| Using N-body simulations of the Galactic disks, we qualitatively study how the metallicity distributions of the thick and thin disk stars are modified by radial migration induced by the bar and spiral arms. We first discuss that radial migration is inefficient for the thick disk stars, and even the bar formation cannot change the metallicity distribution of the thick disk stars much. Therefore, we argue that the thick disk of the progenitor of the Milky Way should not have a steep metallicity gradient. We then show that radial migration drives a positive vertical metallicity gradient in the thin disk whose scale-height is constant. On the other hand, if the initial thin disk is flaring, with scale-height increasing with galactocentric radius, radial migration leads to a negative vertical metallicity gradient, which is consistent with the current observed trend. This model mimics a scenario where the star-forming thin disk was flaring in the outer region at earlier epochs. | |
| KHOPERSKOV Sergey | Poster |
| Star formation in barred galaxies: understanding the quenching phase | |
| Large surveys of galaxies over the last decade have established that most galaxies shutdown their star formation. In the Milky Way, there are evidences that a quenching phase occured between 7 and 9 Gyr ago, and could be related to the formation of the bar (Haywood et al 2016). Since optical and near-IR observations indicate that nearly 60% of disk galaxies in the local universe are barred, it is important to understand a possible relation between the bar formation and quenching in disk galaxies. To explore this issue we investigate the evolution of disk galaxies using N-body/hydrodynamical simulations, including star formation, stellar feedback and multiphase ISM. In both types of models with analytical bars and fully evolving isolated galaxies we find that the stellar bar generates turbulence in the central part of the gaseous disk. Indeed, we detect a sensible growth of the gas velocity dispersion in the galactic central regions (i.e. within the bar scale length), which reaches values up to 15-20 km/s at the end of the bar formation phase. In turn, the star formation efficiency decreases rapidly and in the majority of our models it quenches the star formation in the galaxy. We also demonstrated that gas is not exhausted at the end of the bar formation phase, being still present in the inner kpcs of the galaxy. Thus we argue that the action of the stellar bar can efficiently quench the star formation without significant gas removal from the galactic disk. | |
| KOBAYASHI Masato | Poster |
| Evolutionary Picture of Giant Molecular Cloud Mass Functions on Galactic Scales | |
| We formulate the time evolution of giant molecular cloud (GMC) mass functions on galactic disks. In our model, a network of expanding supernovae and HII regions drives the giant molecular cloud formation and evolution. Such a network provides (i) GMC formation and self-growth through multiple episodes of warm neutral medium compression, (ii) GMC self-dispersal by radiation from massive stars, and (iii) cloud-cloud collisions. We successfully reproduce the observed variation of GMC mass functions between arm and inter-arm regions (e.g., M51 by Schinnerer et al. 2013; Colombo et al. 2014a). Our results suggest that the mass function slope is determined by the ratio of giant molecular cloud formation timescale over its dispersal timescale, whereas the massive end is controlled by cloud-cloud collisions. Our results also indicate that typically a few per cent of dispersed gas is recycled to form a newer generation of GMCs. Future large radio observations may put unique constraints on the GMC formation/dispersal timescales and on the amount of dispersed gas in different environment on galactic scales. | |
| KORMENDY John | Oral |
| Secular Evolution of Galaxy Disks: Our Milky Way as a Case Study | |
| A summary of secular evolution of galaxy disks by redistribution of angular momentum driven -- in the case of our Milky Way -- mainly by the bar suggests that such evolution should be most important in the present-day Universe at just the Hubble type SBbc of our Galaxy. In this talk, I emphasize 3 themes: (1) Our Milky Way is typical of giant galaxies in field environments: like most such galaxies, its history has been very gentle, with internal structure dominated by secular processes. (2) In their parameters, the disk and "boxy bulge" of our Milky Way are normal for a galaxy of M_V ~ -21.4. (3) Physical analogs of our Milky Way which show similar structure, kinematics, and stellar populations are the SB(r)b galaxies NGC 4565 and NGC 5746. All three galaxies have boxy, almost-end-on bars with closely similar properties. All three galaxies show no sign of a classical bulge. Because NGC 4565 and NGC 5746 have prominent inner rings, it would be interesting to check whether our Milky Way has an inner, star-forming ring encircling the ends of its bar. | |
| LANFRANCHI Gustavo A. | Poster |
| The Production of Neutron-capture Elements in the Fornax Dwarf Spheroidal Galaxy | |
| The Fornax dwarf spheroidal galaxy is one of the most distant and luminous member of the Local Group of galaxies associated with the Milky Way. As all the other classical dwarf spheroidal galaxies, this galaxy is characterised by low metallicities ($[Fe/H]_{mean} \sim -1.0$), low total mass ($\sim 10^7 M_{\odot}$), and no sign of gas at the present epoch. The large amount of recently published data, especially chemical abundances, offers a great opportunity to analyse in detail the production of neutron-capture elements in this system. The present analysis was performed by means of a detailed chemical evolution model and a statistical method that compared the predictions of the model with the observed data. Different scenarios for the star formation history of Fornax were adopted in the attempt to reproduce the observed data. After fitting the stellar metallicity distribution, the age-metallicity relation and the [alpha/Fe] relations, the results of the models were compared to the observed trends of r- and s-processed elements. The classical scenario in which r-rocessed elements are produced in massive stars and s-processed elements in low and intermediate massive stars is not sufficient to explain the observations. New scenarios, which consider the production os s-elements in massive fast rotating stars and r-process in neutron star mergers are needed to fit the observed trends of such elements. | |
| LAPORTE Chervin | Oral |
| The response of the Milky Way disc to the Large Magellanic Cloud & Sagittarius | |
| The Milky Way disc is asymmetric about the midplane. The HI shows a warp and recent star count surveys show that the disc is rippled (both in z and vz). Their respective origins are still not settled. I will show results that suggest that all these features in the disc are shaped by its two most massive satellites. I will present the first self-consistent N-body models of the MW and LMC pair in a first infall scenario designed to study the response of the disc to different mass models. I will show that a massive LMC of virial mass 2.5x10^11 Msun predicts a warp with the correct phases as the observed HI warp but no ripples. By contrasting the response of the disc with a heavy Sgr model I will also show that no single interaction model (MW+LMC/MW+Sgr) can capture all the features seen in the disc and that one should consider the collective effect of both satellites. To this end, I will present self-consistent N-body models of the MW+LMC+Sgr interaction (Laporte et al. in prep). | |
| LEHNERT Matthew | Oral |
| The Milky Way as a Distant Galaxy | |
| The life cycle of the Milky Way presents all the important phases of evolution we observe directly in distant galaxies -- early growth through intense star formation, quenching of its star formation for a Gyr or so, and then growth through relatively "quiescent" star formation. As such, the MW provides an interesting test of our ideas on how galaxies evolved and how we interpret detailed observations of distant galaxies. I discuss the evolution of the MW within the context of direct observations of distant galaxies. Specifically, I discuss the characteristics the MW compared to its analogues focussing on the evolution of star formation and specific star formation rates, the role of turbulence powered by intense star formation in regulating star formation and the metal distribution, the overall growth of metals in galaxies, and how galaxies might be quenched temporarily. | |
| LEROY Adam | Oral |
| Observing nearby galaxies in dense gas at high resolution: trying to unify the MW and extragalactic views of star formation | |
| TBD | |
| LÓPEZ-CORREDOIRA Martín | Poster |
| No X-shape in the Milky Way young bulge | |
| A number of recent papers have claimed the discovery of an X-shape structure in the bulge of our Galaxy, all of them basing their conclusion in the analysis of high metallicity red clump star counts in the region |l|<10 deg., 5 deg.<|b|<10 deg., where they find a double peak in the star counts along the line of sight. One may suspect that some contamination may produce the artifact of the second peak in the density. In order to corroborate or reject this result, we pursue to analyze the stellar density of bulge stars in the same regions using a different stellar population characteristic of the young bulge (<~5 Gyr): F0-F5 main sequence stars with distances derived through photometric parallax, with VISTA-VVV data. Only a single peak in the density distribution along the line of sight is observed, so there is no X-shape structure for this population of stars, tentatively leading to the conclusion that previous analyses with the red clump stars, of equal or higher age, were not correct. | |
| MADAU Piero | Oral |
| The Light and Dark Side of Galaxy Formation: Building the Milky Way | |
| TBD | |
| MAGRINI Laura | Oral |
| Following the evolution of the Galactic disc with Open Clusters | |
| Galactic Open Clusters are among the best tracers of the composition of the Galactic thin disc, not only at present but also in differ epochs of the Galaxy life-time. They are indeed a numerous population, located from the inner regions to the outskirts of the Milky Way, and ranging in large interval of ages. I will present the results of abundance determinations of about 20 elements, belonging to different nucleosynthesis channels (from the alpha- elements to iron-peak, neutron-capture, odd-elements), in a sample of open clusters from the forth data release of the Gaia-ESO Survey. I will compare them the most recent Galactic chemical evolution models, highlighting the potentiality in constraining both the stellar yields and the assumptions of models. | |
| MARTINEZ MEDINA Luis | Poster |
| Revealing the spiral arms through radial migration and the shape of the Metallicity Distribution Function | |
| Recent observations show that the Milky Way’s metallicity distribution function (MDF) changes its shape as a function of radius. This new evidence of radial migration within the stellar disc sets additional constrains on Galactic models. By performing controlled test particle simulations in a very detailed, observationally motivated model of the Milky Way, we demonstrate that, in the inner region of the disc, the MDF is shaped by the joint action of the bar and spiral arms, while at outer radii the MDF is mainly shaped by the spiral arms. We show that the spiral arms are able to imprint their signature in the radial migration, shaping the MDF in the outskirts of the Galactic disc with a minimal participation of the bar. Finally, we seek the structural and dynamical parameters of the spiral arms that better reproduce the shape of the MDF through radial migration. | |
| MATSUNAGA Noriyuki | Poster |
| A lack of classical Cepheids in the inner part of the Galactic disk | |
| Recent large-scale infrared surveys have been revealing stellar populations in the inner Galaxy seen through strong interstellar extinction in the Galactic disk. In particular, classical Cepheids with their period-luminosity and period-age relations are useful tracers of Galactic structure and evolution. Interesting groups of Cepheids reported recently include four Cepheids in the Nuclear Stellar Disk (NSD), about 200 pc around the Galactic Centre, found by Matsunaga et al. (2011, Nature, 477, 190) and those spread across the bulge region reported based on VVV data. We here report our discovery of several classical Cepheids towards the bulge region and discuss the large impact of the reddening correction on distance estimates for these objects. Assuming that the four Cepheids in the NSD are located at the distance of the Galactic Centre, and the extinction law, i.e. wavelength dependency of the interstellar extinction, is not systematically different between the NSD and other bulge lines-of-sight, most of the other Cepheids discussed here are located signifficantly further than the Galactic Centre. This suggests a lack of Cepheids in the inner 3 kpc region of the Galactic disk except the NSD. Recent radio observations of star-forming regions show a similar distribution. | |
| MATSUNO Tadafumi | Poster |
| An observational Constraint on the early universe from lithium abundance of extremely-metal poor stars | |
| While the almost constant lithium abundance of warm metal-poor stars (-3.5<[Fe/H]<-2, Teff>5800 K) has been interpreted as a consequence of the Big Bang, most of ultra metal-poor stars (UMP stars; [Fe/H]<-4) show lower lithium abundance. In order to investigate the cause of low lithium abundance, we measure lithium abundance of 6 warm extremely metal-poor stars ([Fe/H]~-3.3) and search for correlations between lithium abundance and abundances of other elements. The result that any correlation has not been found so far indicates that the main mechanism to reduce the lithium abundance is related to the iron abundance. Although the possibility that low lithium abundance is originated from inefficient mixing of the ejecta from pop III supernovae with interstellar medium in the early universe seems to be excluded, larger sample of warm UMP stars are desired in order to clarify the cause of low lithium abundance. | |
| MEL'NIK Anna | Oral |
| Different models of the Galactic spiral structure: kinematical and morphological aspects | |
| Several models of the Galactic spiral structure and their capability to reproduce kinematics of young stars in the 3-kpc neighborhood of the Sun are considered. Model with regular spiral pattern rotating rigidly with the same angular velocity, model of a two-component outer ring R1R2 which is forming near the OLR of the bar, and model of transient spiral arms are discussed. | |
| MESSINEO Maria | Poster |
| A new sample of red supergiants in the inner Galaxy. | |
| Red supergiants (RSGs) are infrared bright massive stars easily detectable at a distance of a few megaparsecs. Their complex evolution is dominated by mass-loss and rotation that strongly affect their final fate. Even though the Milky Way is the closest laboratory of resolved stellar populations, only a thousand Galactic RSGs are currently known. This is due to our location on the Disk, dust observation, and uncertain distances. I will present results from a recent search for Galactic RSGs in the direction of the inner Galaxy (Messineo et al. 2016). A total of 94 targets selected from the 2MASS and GLIMPSE I North catalogs were spectroscopically observed at infrared wavelengths, and an extraordinary large number of new RSGs were confirmed. Their distances range from 3.6 ± 0.4 to 8.6 ± 0.7 kpc. The newly discovered RSGs are a key ingredient for our novel models of Galaxy formation and evolution. An overdensity of RSGs is located between 25 and 30 degrees of Galactic longitude, where the near-side of the Bar ends and meets the spiral arms. | |
| MIGLIO Andrea | Oral |
| Solar-Like Oscillating Stars as Standard Clocks and Rulers for Galactic Studies | |
| The CoRoT, Kepler and K2 space missions have detected oscillations in hundreds of Sun-like stars and thousands of field red-giant stars. This has opened the door to a new era of stellar population studies in the Milky Way. We report on the current status and future prospects of harvesting space-based photometric data for ensemble asteroseismology, and highlight some of the challenges that need to be faced to use these stars as accurate clocks and rulers for Galactic studies. Also, we will describe our recent efforts to use asteroseismology to infer the properties (primarily age) of key tracers of the early history of the Milky Way, including stars belonging to the globular cluster M4 , to the Galactic thick disk, and we will present the first results on the vertical structure of the disc traced by pulsating giants observed by K2. | |
| MINCHEV Ivan | Oral |
| The evolution of the Milky way disk(s) | |
| I will discuss the chemo-dynamical state of the Milky Way disk and interpret recent chemo-kinematical relations found in spectroscopic surveys (RAVE, GES, APOGEE, Gaia?) in the context of the Galactic disk formation and evolution. | |
| MINTS Alexey | Poster |
| Determining masses, ages and distances for Galactic structure studies | |
| For detailed studies of Galactic structure and evolution it is essential to obtain accurate stellar parameters and distances. We develop an efficient tool to obtain stellar masses, ages and distances from spectral parameters ([Fe\H], log g and Teff) and infrared photometry. We apply this tool to data from large spectroscopic surveys such as APOGEE, SEGUE, RAVE, GAIA-ESO and LAMOST, combined with 2MASS and AllWISE photometry. Supplemented with proper motion catalogs this provides full 6D kinematical information for about one million stars. | |
| MONTEAGUDO NARVIÓN Lara | Poster |
| The star formation history of the LMC bar and inner disk from deep VIMOS imaging. | |
| We will present star formation histories (SFHs) of twelve fields in the bar and inner disk of the Large Magellanic Cloud (LMC). They have been derived from color-magnitude diagrams reaching the oldest main sequence turnoffs obtained from observations using VIMOS at the VLT under sub-arcsecond seeing conditions. We have found stars of all ages and a quite important old SFH, as well as two epochs of enhanced star formation, one that took place 2 Gyr ago, and another one 5 Gyr ago. These events appear in all fields, with varying intensities. The current LMC star formation rate is substantially smaller than in the past. A similar pattern for the SFH of the SMC has been found by Noël et al. (2009) and Cignoni et al. (2012). We hypothesize therefore that these starbursts could be associated to the interaction of the LMC with the Small Magellanic Cloud and/or both Clouds with the Milky Way. | |
| NESS Melissa | Oral |
| Insights from the Galactic Bulge | |
| The bulge is a primary signature of the large-scale processes that have driven the formation and evolution of the Milky Way. I will present the latest observational studies of the bulge and the interpretations of these results in the context of N-body models and formation scenarios. I will showcase the morphology of the bulge, that has been now revealed in intricate detail, as well as the kinematic properties of the bulge from the APOGEE survey, which has mapped the previously unexplored mid-plane regions. I will show our very recent work, where by we have been able to explain the metallicity dependent morphology and kinematics of the bulge in terms of the initial properties of the stars in the disk from which the bulge was formed. Finally I will demonstrate that we are now able to examine the bulge in the extragalactic context, comparing and contrasting with the properties of similar bulges in other galaxies. | |
| PEREZ-VILLEGAS Angeles | Poster |
| Are the metal-poor stars in the Galactic bulge part of the inner stellar halo? | |
| We have used N-body simulations tailored for the Milky Way to investigate the kinematic properties of the metal-poor component in the inner region of the Galaxy. In particular, we will discuss how the kinematics of the Milky Way’s old stellar halo component evolves during the formation and evolution of the Galactic bar and box/peanut bulge, and whether the metal-poor stars in the bulge could be part of the inner stellar halo. | |
| PLEVNE Olcay | Poster |
| Metallicity Gradients in the Solar Neighbourhood | |
| We estimated iron and metallicity gradients in the radial and vertical directions with the F and G type dwarfs in the Solar neighbourhood taken from the RAdial Velocity Experiment (RAVE) Data Release 4 (DR4). These stars were selected according to their atmospheric model parameters and their space velocities and Galactic orbits were calculated utilizing the proper motions, distance and radial velocity components. The radial and vertical directions iron and metallicity gradients were calculated for sub-samples de ned by the contraints on ep and Zmax. We estimed a signi cant gradients for stars have, which circular orbits and small Zmax distances. Thin disc sample was de ned by the constraints ep less than 0.1 and Zmax less than 825 pc. The radial iron and metallicity gradients were calculated for the thin disc sample as d[Fe/H]/dRm = 0.081 +-0.029 and d[M/H]/dRm = 0.060+-0.012 dex/kpc, respectively. The vertical iron gradients estimated for the F and G type dwarfs on circular orbits are d[Fe/H]/dZmax = 0.??1760+-0.039 dex/kpc and d[Fe/H]/dZmax = ??0.119 +-0.036 dex/kpc for the intervals Zmax less than 825 and Zmax less than 1500 pc, respectively. Radial iron gradient (d[Fe/H]/dRm = ??0.081 +-0.029 dex/kpc) value for the thin disk is one highest gradient value in the literature. We conculude that Galactical orbit parameters very important for the gradient studies. | |
| PORTAIL Matthieu | Oral |
| Dynamics and Mass of the Galactic Bulge, Bar and Inner Disk | |
| We present the first non-parametric dynamical model of the entire Galactic Bulge and Bar region. Our model is fitted to the density of Red Clump Giants from a combination of the VVV, UKIDSS and 2MASS surveys, together with stellar kinematics from the BRAVA, OGLE and ARGOS surveys. Including the kinematics as a function of distance from the ARGOS survey we are able to recover the bar pattern speed and the mass distribution of both stars and dark matter in the inner 5 kpc of the Galaxy, hence constraining the full effective potential in the Galactic Bar region. We confirm from a dynamical perspective that the bulge and long bar are consistent with being a single bar structure that buckled to form a central Box/Peanut bulge. We find in addition dynamical evidence for an extra disky mass component in the inner few degrees of the Galaxy, needed to account for the steep rise in velocity dispersion close to the Galactic center. | |
| POSTI Lorenzo | Poster |
| Constraining the dark halo of our Galaxy with distribution functions | |
| We use sophisticated equilibrium models, which depend on the action integrals, to describe the distribution of disc and halo stars in positions and velocities, under the effect of their own gravity plus that of the dark-matter halo in a self-consistent fashion. With this formalism we pin down the distribution functions (DFs) of the discs and the halo with data of nearby stars and we define clean samples of thin & thick discs and stellar halo stars from their dynamics only. A kinematically-clean sample of halo stars is crucial to put new constraints on the shape of the stellar velocity ellipsoid and on the flattening of the dark-matter halo in the vicinity of the Sun. The models' DFs also allow a direct comparison with state-of-the-art numerical simulations. The phase-space structure of simulated galaxies is easily investigated with our analytic DFs and in particular the effect of non-equilibiurm features, such as satellites, bar and spiral arms, can be quantified and accounted for. | |
| PRANTZOS Nikos | Oral |
| On the impact of radial migration on the chemical evolution of the Milky Way disks | |
| I will present several indices suggesting that radial migration has played a role in the chemical evolution of the local disk. Similar conclusions are reached through the study of recent observations of the Li evolution. | |
| RECIO-BLANCO Alejandra | Oral |
| Chemo-kinematical constraints on accreted halo stars from the Gaia-ESO Survey | |
| The ratio of accreted versus in situ halo stars is a key constraint about the importance of mergers in the formation history of the Milky Way. Chemical abundances, combined with kinematics, are powerful tools to unveil the history of Halo's assembly. The ratio of a-elements (e.g. Mg, Si, Ca, Ti) abundance with respect to iron is of particular interest as it has been proposed to discriminate between the Halo in situ population and accreted stars from dwarf galaxies with lower star formation rates (Nissen & Schuster, 2010). I will present a chemo-kinematical analysis of the metal-poor stars included in the Gaia-ESO Survey iDR4 (Giraffe data sample), studying whenever possible their dynamical properties. The transition between the halo and the metal-poor components of the thick and the thick disc will be also addressed. The sample, twice larger than previous GES data releases, is a first window to explore the Galactic Halo outside the solar neighbourhood with high-resolution spectroscopy. | |
| REVAZ Yves | Poster |
| Chemical properties of dwarf spheroidal galaxies emerging from a LCDM Universe | |
| Over the last decade new observing facilities allowed the systematic measurement of abundances in isolated stars in the Milky Way as well as in nearby Local Group dwarf galaxies. Those observations provide strong constraints on the chemical enrichment of galactic systems that must be considered when modelling them. In this talk, I will present fully self-consistent chemo-dynamical simulations of dwarf spheroidal galaxies performed in a cosmological context. The main dynamical but also chemical properties, including the stellar populations, of Sculptor, Sextans or Carina-like galaxies will be presented. In addition, I will discuss spurious numerical effects that directly impact the chemical evolution in very high resolution simulations and directly affect the final stellar abundances. A new method avoiding any resolution limitation, which should be considered in the future, will be proposed. | |
| RICHTER Philipp | Oral |
| Tha circumgalactic gaseous environment of the Milky Way | |
| The Milky Way is surrounded by large amounts of diffuse gaseous matter that connects the stellar body of our Galaxy with its large-scale Local Group environment. To characterize the absorption properties of this circumgalactic medium (CGM) we have constructed the so-far largest survey of ultraviolet absorption features of the Milky Way CGM, based on the analysis of several hundred HST/COS spectra. In this talk I will present the main results of this survey and discuss the spatial distribution of the gas and its physical properties in the context of the evolution of the Milky Way and other Local Group members. | |
| ROBIN Annie | Oral |
| A new step in the population synthesis approach | |
| Combining asterosismology with spectroscopy leads to strong constraints on galactic archeology. We show, through new stellar evolution models combined with population synthesis, how such surveys can be exploited to test scenarios of formation of the Milky Way. | |
| SALVADORI stefania | Oral |
| First stars in the Milky Way environment | |
| Spectroscopic studies of individual stars in the Milky Way and its dwarf satellites provide us with the unique opportunity to reveal the chemical enrichment of the interstellar medium when the Universe was less than 1 Gyr old. I will present new insight on early cosmic star-formation by interpreting state-of-the art chemical abundance studies of very metal-poor stars in different environments: the stellar halo, ultra-faint dwarfs, and classical dwarf spheroidal (dSph) galaxies. I will discuss the implications that current observations have for the Initial Mass Function of the first stars, and present new results for the formation of the stellar halo from its dwarf galaxy progenitors. | |
| SCHULTHEIS Mathias | Oral |
| Chemical abundances in the inner 200 pc | |
| While more and more detailed chemical abundances in the intermediate and outer bulge (such as Baade's Window) are now available thanks to the large spectroscopic surveys ARGOS, Gaia-ESO, and APOGEE, chemical abundances of stars in the inner Galactic bulge with projected distances of $\rm R_{G} \leq 200\,pc$ from the GC remain poorly studied. This innermost region, which is called the Central Molecular Zone, contains a prodigious reservoir of molecular gas with evidence of starburst activity in the last 100,000 years. High interstellar extinction with more than 30 mag in Av require investigations of this region in the K band. Here, we discuss the most recent results of our VLT/CRIRES and Keck/NIRSPEC campaigns where we have observed M giants at high spectral resolution and derive detailed chemical abundances. | |
| SEIDEL Marja | Poster |
| Bar-driven secular evolution in nearby galaxies | |
| The Milky way is most likely a barred galaxy. And yet, studies on this barred component and its impact on the Galaxy’s evolution are limited due to our edge-on view. Therefore we investigated nearby barred galaxies in unprecedented detail with the integral field unit SAURON. Our 2-dimensional maps of the stellar and gaseous component reveal an impact of the bar on the kinematics and stellar populations. Although their effect on global galaxy parameters seems to be marginal, bars seem to have a crucial influence in certain regions (resonance points), in particular altering the bulge. We detect these resonance points in the stellar angular momentum and absorption line index profiles. In combination with Spitzer observations and N-body simulations we further develop a novel method to measure bar strength based on the noncircular motions induced by the bar. Our stellar population analysis shows a flattening of the iron (Fe5015) and magnesium (Mgb) outer gradients along the bar major axis, translating into a flattening of the metallicity gradient. These results confirm recent simulations and discern the important localized influence of bars. All these aspects are important to understand the physics of the ongoing secular evolution and provide insights into the impact of bars in galaxy evolution, such as for the Milky Way. | |
| SHARINA Margarita | Poster |
| Globular clusters with multiple stellar populations. Where they came from? | |
| We found a group of old Galactic globular clusters (GCs) with very similar medium-resolution spectra. The long-slit spectra were taken from the library of Schiavon et al (2005) and obtained with the CARELEC spectrograph of the 1.93-m telescope in the Haute Provence Observatory. We analyzed the spectra using our method of population synthesis using stellar atmospheres models (Sharina et al. 2013, 2014; Khamidullina et al. 2014). Our method allows to derive age, [Fe/H], Y and abundances of 8 chemical elements using medium-resolution integrated-light spectra of globular clusters. A mean metallicity of the group is [Fe/H]=-1.6 dex. All the sample Galactic GCs have extended blue horizontal branches. Multiple stellar population were discovered in the literature in several of them. We study whether their distribution is correlated with the position of Galactic satellites and streams. | |
| SÖKMEN Efsan | Poster |
| Star Formation History of the Milky Way using VVV survey for the Southern Galactic Plane | |
| Star formation history (SFH) is a powerful and unique tool to study the formation and evolution of galaxies. The IAC method to solve the SFH, which is a self-consistent, unique and stable method, that is based on a suite of routines, will be applied to the deep point spread function (PSF) photometry in J and Ks bands obtained by the VISTA Variables in the Via Lactea (The VVV Survey) for the southern galactic disk (-65°< l < -10° and -2°< b < +2°) where the star formation rate is high. | |
| SOKOLOWSKA Aleksandra | Oral |
| GALAXIES AS HEAT ENGINES: FORMATION OF GASEOUS GALACTIC HALOS IN SIMULATIONS OF MILKY WAY–SIZED SYSTEMS | |
| Spiral galaxies are embedded in gaseous halos which connect intergalactic medium (IGM) to the star-forming disks of galaxies. In Sokolowska et al. (2015), we used three N-body/SPH high-resolution cosmological simulations: Eris (Guedes et al. 2011), ErisLE (Bird et al. 2013) and Eris2k (Shen et al. in prep.) to show that properties of the present day gaseous halos are compatible with those of the Milky Way. As a follow-up of this study, we describe the formation of gaseous halos and their hot coronae around spiral galaxies, putting emphasis on the physical mechanisms governing the evolution of separate phases of gas. We investigate the interplay between cooling and heating, as well as the exchange of mass between galaxies and IGM. We also add new runs to the picture: Venus, to assess the impact of richer merger history on our results, as well as ErisBH (Bonoli et al. 2016), to address the role of AGN feedback on the Milky Way mass scale. We thus study the global baryon cycle in the Milky Way-like halos, as well as revisit the relation between cold cosmological accretion and building of the hot phase in these high-resolution simulations. | |
| SPINOSO Daniele | Poster |
| Formation and evolution of a stellar bar in a Milky Way galaxy | |
| I will present the analysis of the formation and evolution processes of a stellar bar in the "ErisBH" N-body SPH cosmological simulation. "ErisBH" is a twin simulation of the Milky Way-analog "Eris" with which it shares the same initial conditions, resolution and phisical processes implementations but it includes also the prescriptions for the formation and evolution of massive black holes. We find that an extended central region of the disk in "ErisBH" becomes bar-unstable after z~1.4 and a clear stellar bar starts to grow after z~0.5 both in strength and length reching a maximum extent of r~2.2 kpc at z~0.1. As the bar grows it becomes prone to buckling instability. A buckling event is clearly observable at z~0.1 and leads to the formation of a boxy-peanut structure in the galaxy bulge. The bar is able to exert strong gravitational torques on the gas up to its radial extent. This produces a gas-depleted region in which star formation is strongly suppressed. This process may be responsible for the lowering of the galaxy global star formation rate, in agreement with recent observational studies. | |
| STONKUTE Edita | Poster |
| Binaries and large spectroscopic surveys | |
| Stellar multiplicity is a key parameter for many astrophysical questions. Several interesting astronomical phenomena, such as gravitational waves and gamma-ray bursts, arise from binary stars, and the knowledge of multiplicity could provide constraints on possible channels of star formation and evolution in the Galaxy. For ongoing and coming large spectroscopic surveys, such as RAVE, APOGEE, LAMOST, Gaia-ESO, GALAH and 4MOST, it is important to identify the binaries to clean the survey products from potentially faulty results. However, little is known about the binary frequency in Milky Way field stars, particularly outside the Solar neighbourhood. I will present our models of the effect of binaries on high-resolution spectroscopic surveys, in order to determine how many binaries will be observed, whether unresolved binaries will contaminate measurements of chemical abundances, and how we can use spectroscopic surveys to better constrain the population of binaries in the Galaxy. As an application we model binary stars that mimic APOGEE red giants in the Galactic disc. | |
| SYSOLIATINA Kseniia | Poster |
| Dynamical model of the Milky Way disk | |
| To construct a self-consistent Milky Way disk model we use classical Jeans analysis. For starting point we took local model of solar cylinder (Just&Jahreiß, 2010) and extended it to middle galactocentric distances. Our disk consists of a set of isothermal subpopulations. Thin and thick disks and gas are described by exponential radial density profiles with scalelength of 2.5, 1.5 and 4.5 kpc and constant thickness of 400, 1200 and 150 pc respectively. Dark matter radial density profile is given as a power law. Changing star formation rate (SFR) and age-velocity dispersion relation (AVR) with distance, we solve Poisson's equation self-consistently and calculate total gravitational potential of the disk, stellar scaleheight and vertical matter distribution at different radii. We can predict age distributions, star counts, CMDs and discuss the dependence on the adopted SFR and AVR. The results can be directly compared to the first Gaia data release on Tycho-2 stars expected in Sept. 2016. | |
| THOMAS Guillaume | Poster |
| Constraining the Galactic potential with streams | |
| Stellar streams, generated during the accretion of satellites of the Milky Way, are the best tracers to determine the shape of the Galactic potential at large distances from the galactic plane. New and upcoming large surveys (Gaia, Luau, Weave , 4MOST,.. ) are going to improve our knowledge of them, both in terms of distances and kinematics. As a bonus, they can be used to discriminate between different paradigms such as ?CDM or MOND. The MOND paradigm, proposing a modification of the gravitationnal law in the weak acceleration regime, can reproduce very well the rotation curve of numerous disk galaxies, and thus their gravitationnal potential in the disk. It is in this context that we are trying to reproduce the observed Sagittarius stream by simulating it in the MOND and ?CMD paradigms, and that we compare the generic differences between its shape in these different paradigms. | |
| TING Yuan-Sen | Oral |
| Unraveling the history of the Milky Way disk through chemical tagging | |
| Understanding physical processes responsible for the formation and evolution of galaxies like the Milky Way is a fundamental problem in astrophysics. However, a key challenge is that the properties and orbits of the stars can only be observed at present: in order to understand what happened in the Milky Way at earlier epochs, one must explore “archeological” techniques. One idea, "chemical tagging”, aims to probe the history of the Milky Way via the unique imprint in chemical abundance space of long-disrupted star clusters. I will discuss the opportunities and challenges associated with chemical tagging, including a first constraint on the disrupted cluster mass function in the Milky Way. I will also describe a new set of tools for efficient fitting large quantities of stellar spectra and opportunities for extracting many stellar parameters from low-resolution data. | |
| TSUJIMOTO Takuji | Oral |
| r-process enrichment in the Milky Way and nearby dwarf galaxies | |
| I'll enter it later | |
| TUNÇEL GÜÇTEKIN Sabiha | Poster |
| New Calibrations for Photometric Metallicity and Parallax Estimation | |
| This study in well-known F and G type main-squence stars iron abondance and trigonometric parallaxes.In this study, Sun around the iron (Fe) abundance and trigonometric parallaxes and photometric metallicity of the main sequence stars in the well-known F and G spectral type and photometric absolute brightness calibration has been created to be a function of purple-border no longer using the UBV photometry.These calibrations are appointed by the Hipparcos distance of the main sequence stars in the middle spectral type that can not be measured by the satellite and metallicity are ready to be used for the study of galactic structure. | |
| VIVAS Kathy | Oral |
| Variable Stars in the Ultra-Faint Dwarf Satellites | |
| The recent discoveries of new low-luminosity satellites of the Milky Way are of tremendous importance to reconcile observations and LCDM predictions for the number and distribution of satellites around the Milky Way. Confirmation and full characterization of the new discoveries are needed in order to test these theoretical predictions and to understand their role in the formation of Milky Way-type galaxies. Key to such characterization is accurate distance measurements toward the new galaxies. RR Lyrae stars are excellent standard candles and thus provide an alternative method for determining the distance to galaxies. This is particularly important in these distant and low-luminosity systems lacking young populations (i.e., systems that cannot host Cepheids that could be used as distance indicators). In addition, estimation of accurate distances by isochrone fitting is hard because there may be very few stars in the upper part of the color-magnitude diagram (CMD), the contamination by field stars may be important due to the low density of stars in the system, and the main sequence turn-off may not be available in some cases due to their large distances. In this talk we describe our ongoing efforts to characterize the variable star population in several of the ultra-faint dwarf satellites recently discovered by DES and PanStarrs. | |
| WANAJO Shinya | Poster |
| Origin of r-process elements and nuclear cosmo-chronology | |
| Origin of r-process elements and their galactic evolutionary histories are poorly understood. In addition, the source of the robustness of r-process pattern found in galactic stars is still unknown. We show that our models of neutron star mergers naturally explain both the amounts of galactic r-process material and the r-pattern robustness. It will also be demonstrated that a new cosmo-chronometric combination of Pb-Bi-Th-U can serve as a powerful tool to determine ages of old stars, a key to understand early galactic histories. | |
| WEGG Chris | Poster |
| The Inner Milky Way has a Low Dark Matter Fraction and a Nearly Maximal Disk: Constraints from Galactic Microlensing Surveys | |
| Microlensing provides a unique tool to break the stellar to dark matter degeneracy in the inner Milky Way. From a range of N-body models fitted to the Galactic bulge together with exponential disks outside we find the revised MOA-II data requires that 0.88±0.07 (1s) of the circular velocity is baryonic 4-5kpc from the Galactic center. This is in agreement with the EROS-II microlensing survey of red clump giants, where we find 0.9±0.1 (1s). Low dark matter fractions are also required in dynamical models of the entire inner Galaxy, where the stellar to dark matter degeneracy is instead broken though direct star-by-star measurement of the bulge population. These levels of maximality are not necessarily inconsistent with NFW or adiabatically contracted haloes in the inner Galaxy. However reconciling them with the dynamical mass in the bulge and recent estimates of the dark matter density in the solar neighborhood drives the dark matter towards cored profiles in the central ~1kpc. | |
| WETZEL Andrew | Oral |
| The Latte Project: Cosmological Simulations of Milky Way-mass Galaxies with Realistic Satellite Populations | |
| I will present early results from the Latte Project, a new suite of cosmological zoom-in baryonic simulations that model the formation of Milky Way-mass galaxies at parsec-scale resolution, using the FIRE (Feedback in Realistic Environments) model for star formation and stellar feedback. I will discuss the roles of accretion and stellar feedback in driving the formation and structure of Milky Way-mass galaxies, including mixing and migration of distinct stellar populations. The Latte simulations also self-consistently resolve the satellite dwarf galaxies that form around each host, and I will discuss the relative impacts of (internal) stellar feedback and (external) environment on their star formation histories, stellar kinematics, and chemical enrichment histories, including progress in addressing the long-standing "missing satellites" and "too-big-to-fail" problems of LCDM cosmology. | |
| WOJNO Jennifer | Oral |
| Kinematic correlations in the solar neighborhood as seen by RAVE | |
| Using updated distances and metallicities from the RAVE survey, we explore the kinematics of chemically-separated ‘thin’ and ‘thick’ disc stars in the extended solar neighborhood. To investigate the correlation between velocity and metallicity, we separate a sample of ~20,000 stars into alpha-high and alpha-low disc components using a probabilistic method, and explore the kinematic trends as a function of metallicity. We propose that the processes used to characterize this parameter space with RAVE can be further extended to other data sets where the chemical disk components cannot be disentangled a priori. In addition, we investigate potential kinematic biases present in the RAVE survey by characterising its selection function, and use this selection function to generate a mock-RAVE catalogue. As RAVE will have significant overlap with Gaia DR1, we expect to utilize improved parallax and proper motion data in order to better explore these fundamental relationships. | |
| ZANA Tommaso | Poster |
| Bar formation in a cosmological context: a dynamical insight | |
| I will present the analysis of the Eris-BH run (Bonoli et al. 2016) , a high resolution zoom-in cosmological simulation resulting into a Milky way like barred galaxy. I will detail the physical processes behind the formation and growth of the bar, including the possible effect of the most recent minor mergers (redshift ~1). | |
| ZHU Ling | Poster |
| Dynamical bulge-disk decomposition for spiral galaxies. | |
| We construct Schwarzschild dynamical models for Milky Way like spiral galaxies as whole, including the bulge and disk components. This orbit superposition method allows us to uncover the luminous and dark matter in galaxies without (astro)physically unjustified assumptions on shape and velocity anisotropy made in common dynamical approaches. Moreover, the inferred intrinsic orbital structure enables us to dynamically decompose galaxies into different components. Subsequently, we can for each component robustly derive its mass distribution as well as internal rotation, velocity dispersion and higher-order dynamics. We apply this method to CALIFA spiral galaxies and find bulge, thin and thick disks with distinct mass distributions and kinematical properties. From early to late type spiral galaxies, the mass fraction of dynamical bulge component decreases and that of the disk components increases, while the late type Sc and Sd galaxies dramatically have heavier thick disk component than the Sa and Sb galaxies. The mass fraction of our dynamically-decomposed bulge and disk (thin + thick) components are roughly consistent with that from the photometrically decomposition, however the radially mass profiles do not exactly follow a ‘sersic’ bulge and an ‘exponential’ disk. | |
UMR7095 - Institut d'Astrophysique de Paris - 98 bis boulevard Arago - 75014 Paris