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We analyse the kinematics and dynamics of a homogeneous sample of red clump stars selected from the second Gaia data release catalogue in the direction of the Galactic poles. The level of completeness of the sample at heights between 0.6 and 3.5 kpc is asserted by comparison with the 2 Micron All Sky Survey catalogue. We show that both the density distribution and velocity dispersion are significantly more perturbed in the North than in the South, in all analysed regions of our Galactic neighbourhoods. We provide a detailed assessment of these North-South asymmetries at large heights. We then proceed to evaluate how such asymmetries could affect determinations of the dynamical matter density under equilibrium assumptions. We find that a Jeans analysis delivers relatively similar vertical forces and integrated dynamical surface densities at large heights above the plane in both hemispheres. At these heights, the densities of stars and gas are very low and the surface density is largely dominated by dark matter, which allows to estimate, separately in the North and South, the local dark matter density derived under equilibrium assumptions. In the presence of vertical perturbations, such values should be considered as an upper limit. This Jeans analysis yields values of the local dark matter density above 2~kpc, $\rho_{\rm DM} \sim 0.013 \, {\rm M}_\odot/{\rm pc}^3$ ($ \sim 0.509 \, {\rm GeV/cm}^3$) in the perturbed Northern hemisphere, and $\rho_{\rm DM} \sim 0.010 \, {\rm M}_\odot/{\rm pc}^3$ ($ \sim 0.374 \, {\rm GeV/cm}^3$) in the much less perturbed South. As a comparison, we determine the local dark matter density by fitting a global phase-space distribution to the data. We end up with a value in the range of $\rho_{\rm DM} \sim 0.011 - 0.014 \, {\rm M}_\odot/{\rm pc}^3$ in global agreement with Jeans analysis., Comment: 16 pages, 14 figures, accepted in A&A

Galactic microlensing datasets now comprise in excess of $10^4$ events, and with the advent of next generation microlensing surveys that may be undertaken with facilities such as the Rubin Observatory (formerly LSST) and Roman Space Telescope (formerly WFIRST), this number will increase significantly. So too will the fraction of events with measurable higher order information such as finite source effects and lens-source relative proper motion. Analysing such data requires a more sophisticated Galactic microlens modeling approach. We present a new second-generation Manchester-Besan��on Microlensing Simulator (MaB$��$lS-2), which uses a version of the Besan��on population synthesis Galactic model that provides good agreement with stellar kinematics observed by HST towards the bulge. MaB$��$lS-2 provides high-fidelity signal-to-noise limited maps of the microlensing optical depth, rate and average timescale towards a 400 sq. degree region of the Galactic bulge in several optical to near-infrared pass-bands. The maps take full account of the unresolved stellar background as well as limb-darkened source profiles. Comparing MaB$��$lS-2 to the efficiency-corrected OGLE-IV 8,000 event sample shows a much improved agreement over the previous version of MaB$��$lS, and succeeds in matching even small-scale structural features in the OGLE-IV event rate map. However, there remains evidence for a small under-prediction in the event rate per source and over-prediction in timescale. MaB$��$lS-2 is available online () to provide on-the-fly maps for user supplied cuts in survey magnitude, event timescale and relative proper motion., 24 pages, 21 figures, Journal: MNRAS, for associated online tool, visit

Connecting star and planet properties in a single model is not straightforward. Stellar population synthesis models are key to explore combined statistical constraints from stars and planets observations. The Besan\c{c}on stellar population synthesis model (Robin et al. 2003, Lagarde et al. 2017) includes now the stellar evolutionary tracks computed with the stellar evolution code STAREVOL (Lagarde et al. 2012, Amard et al. 2016). It provides the global (M, R, Teff, etc) and chemical properties of stars for 54 chemical species. It enables to study the different galactic populations of the Milky Way (the halo, the bulge, the thin and thick disc) and a specific observational survey. Here, we couple the Besan\c{c}on model with a simple stoichiometric model (Santos et al. 2017) in order to determine the expected composition of the planet building blocks (PBB). We investigate the trends and correlations of the expected chemical abundances of PBB in the different stellar populations of the Milky Way (Cabral et al. 2018)., Comment: 4 pages, 3 figures, conference

Context. Dynamically self-consistent galactic models are necessary for analysing and interpreting star counts, stellar density distributions, and stellar kinematics in order to understand the formation and the evolution of our Galaxy. Aims. We modify and improve the dynamical self-consistency of the Besan��on Galaxy model in the case of a stationary and axisymmetric gravitational potential. Methods. Each stellar orbit is modelled by determining a Staeckel approximate integral of motion. Generalised Shu distribution functions with three integrals of motion are used to model the stellar distribution functions. Results. This new version of the Besan��on model is compared with the previous axisymmetric BGM2014 version and we find that the two versions have similar densities for each stellar component. The dynamically self-consistency is improved and can be tested by recovering the forces and the potential through the Jeans equations applied to each stellar distribution function. Forces are recovered with an accuracy better than one per cent over most of the volume of the Galaxy., 8 pages, 6 figures Accepted for publication in Astronomy and Astrophysics

Accurate characterization of thick disc properties from recent kinematic and photometric surveys provides converging evidences that this intermediate population is a sequel of the violent heating of early disc populations by a merging satellite galaxy. The thick disc population is revisited under the light of new data in a number of galactic sample fields. Various thick disc hypotheses are fitted to observational data through a maximum likelihood technique. The resulting characteristics of the thick disc are the following : a scale height of 760 $\pm$ 50 pc, with a local density of 5.6 $\pm$ 1 \% of the thin disc. The scale length is constrained to be 2.8 $\pm$ 0.8 kpc, well in agreement with the disc scale length (2.5 $\pm$ 0.3 kpc). The mean metallicity of the thick disc is found to be -0.7 $\pm$ 0.2 dex, with no {significant} metallicity gradients. These photometric constraints in combination with kinematic data give new constraints on the thick disc formation. We show that thick disc characteristics are {hardly compatible with a top-down formation scenario} but fully compatible with a violent merging event arising at the early thin disc life time as described by Quinn, Hernquist \& Fullagar (1993)., 8 pages, latex, 6 postcript figures available by ftp at ftp://ftp.obs-besancon.fr/pub/outgoing/annie/ as thd-fig*.ps

As part of a stellar population sampling program, a series of photometric probes at various field sizes and depths have been obtained in a low extinction window in the galactic anticentre direction. Very deep CCD frames probe the most external parts of the disc, providing strong evidence that the galactic density scale length for the old disc population is rather short (2.5 kpc) and drops abruptly beyond 5.5-6 kpc. Deeper frames in the I band allow to estimate photometric distances and confirm the position of the disc edge. A few stars are found at larger distances. Their number is exactly what we expect if the thick disc does not have any cutoff. We discuss the implications for the formation and evolution of the disc, for the star formation threshold, and for the origin of the thick disc population., Comment: Latex 6 pages (crckapbk style). 2 figures upon request or by anonymous ftp to ftp://ftp.obs-besancon.fr/pub/outgoing/annie/ Send all Comments, questions, requests, etc. to: annie@obs-besancon.fr

The Sloan Digital Sky Survey (SDSS) started a new phase in August 2008, with new instrumentation and new surveys focused on Galactic structure and chemical evolution, measurements of the baryon oscillation feature in the clustering of galaxies and the quasar Ly alpha forest, and a radial velocity search for planets around ~8000 stars. This paper describes the first data release of SDSS-III (and the eighth counting from the beginning of the SDSS). The release includes five-band imaging of roughly 5200 deg^2 in the Southern Galactic Cap, bringing the total footprint of the SDSS imaging to 14,555 deg^2, or over a third of the Celestial Sphere. All the imaging data have been reprocessed with an improved sky-subtraction algorithm and a final, self-consistent photometric recalibration and flat-field determination. This release also includes all data from the second phase of the Sloan Extension for Galactic Understanding and Evolution (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars at both high and low Galactic latitudes. All the more than half a million stellar spectra obtained with the SDSS spectrograph have been reprocessed through an improved stellar parameters pipeline, which has better determination of metallicity for high metallicity stars., Astrophysical Journal Supplements, in press (minor updates from submitted version)

We investigate the kinematics of the intermediate population using the photometric and astrometric sample surveys towards two opposite directions (galactic centre and anticentre) at intermediate latitude. A multivariate discriminant analysis (MDA) is used to distinguish the `Thick Disk' from other populations with the help of the Besan\c con model of population synthesis. The data constrain the asymmetric drift of the intermediate population, which is found to be 40$\pm$10 km sec$^{-1}$ and does not depend on the galactic radius., Comment: postscript file, 7 pages, 5 figures (figures available on request), poster paper presented at 22nd IAU General Assembly (Symp no. 164, Stellar Populations) in The Hauge, Netherlands, 15-19 August, 1994