Posters
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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... | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
| 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. | |
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