The ALADIN Interactive Sky Atlas

The Aladin interactive sky atlas, developed at CDS, is a service providing simultaneous access to digitized images of the sky, astronomical catalogues, and databases. The driving motivation is to facilitate direct, visual comparison of observational data at any wavelength with images of the optical sky, and with reference catalogues. The set of available sky images consists of the STScI Digitized Sky Surveys, completed with high resolution images of crowded regions scanned at the MAMA facility in Paris. A Java WWW interface to the system is available at: http://aladin.u-strasbg.fr/Comment: 8 pages, 3 Postscript figures; to be published in A&

The thick disk of the galaxy: sequel of a merging event

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 ± 50pc, with a local density of 5.6 ± 1% of the thin disc. The scale length is constrained to be 2.8 ± 0.8kpc, well in agreement with the disc scale length (2.5 ± 0.3kpc). The mean metallicity of the thick disc is found to be -0.7 ±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)

New distances to RAVE stars

Probability density functions are determined from new stellar parameters for the distance moduli of stars for which the RAdial Velocity Experiment (RAVE) has obtained spectra with S/N>=10. Single-Gaussian fits to the pdf in distance modulus suffice for roughly half the stars, with most of the other half having satisfactory two-Gaussian representations. As expected, early-type stars rarely require more than one Gaussian. The expectation value of distance is larger than the distance implied by the expectation of distance modulus; the latter is itself larger than the distance implied by the expectation value of the parallax. Our parallaxes of Hipparcos stars agree well with the values measured by Hipparcos, so the expectation of parallax is the most reliable distance indicator. The latter are improved by taking extinction into account. The effective temperature absolute-magnitude diagram of our stars is significantly improved when these pdfs are used to make the diagram. We use the method of kinematic corrections devised by Schoenrich, Binney & Asplund to check for systematic errors for general stars and confirm that the most reliable distance indicator is the expectation of parallax. For cool dwarfs and low-gravity giants tends to be larger than the true distance by up to 30 percent. The most satisfactory distances are for dwarfs hotter than 5500 K. We compare our distances to stars in 13 open clusters with cluster distances from the literature and find excellent agreement for the dwarfs and indications that we are over-estimating distances to giants, especially in young clusters.Comment: 20 pages accepted by MNRAS. Minor changes to the submitted versio

The selection function of the RAVE survey

published_or_final_versio

The sixth data release of the Radial Velocity Experiment (RAVE). I. Survey description, spectra and radial velocities

The Radial Velocity Experiment (RAVE) is a magnitude-limited (9<I<12) spectroscopic survey of Galactic stars randomly selected in the southern hemisphere. The RAVE medium-resolution spectra (R~7500) cover the Ca-triplet region (8410-8795A). The 6th and final data release (DR6 or FDR) is based on 518387 observations of 451783 unique stars. RAVE observations were taken between 12 April 2003 and 4 April 2013. Here we present the genesis, setup and data reduction of RAVE as well as wavelength-calibrated and flux-normalized spectra and error spectra for all observations in RAVE DR6. Furthermore, we present derived spectral classification and radial velocities for the RAVE targets, complemented by cross matches with Gaia DR2 and other relevant catalogs. A comparison between internal error estimates, variances derived from stars with more than one observing epoch and a comparison with radial velocities of Gaia DR2 reveals consistently that 68% of the objects have a velocity accuracy better than 1.4 km/s, while 95% of the objects have radial velocities better than 4.0 km/s. Stellar atmospheric parameters, abundances and distances are presented in subsequent publication. The data can be accessed via the RAVE Web (http://rave-survey.org) or the Vizier database.Comment: 32 pages, 11 figures, accepted for publication to A

Les moteurs de l'evolution galactique: recherche de signatures des mecanismes d'evolution

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 20403 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Structure et dynamique des disques de la Galaxie

STRASBOURG-Sc. et Techniques (674822102) / SudocBORDEAUX1-Observatoire (331672201) / SudocSudocFranceF

Formation du disque de la Voie Lactée

Cette thèse étudie la cinématique du disque de la galaxie en vue de contraindre les modèles de sa formation. Elle se place dans le cadre du projet RAVE qui a pour but de faire des mesures spectroscopiques de vitesses radiales et de paramètres stellaires d un million d étoiles de l hémisphère céleste Sud. Pour déterminer les caractéristiques cinématiques du disque, deux méthodes ont été utilisées l inversion directe des comptages d étoiles en fonction de la distance et de la vitesse et la modélisation cinématique du disque de la galaxie. Pour l inversion, la distance photométrique des étoiles a été déterminée à partir de leur magnitude apparente, en faisant une sélection en couleur judicieuse. Les mouvements propres ont ensuite été transformés en vitesse. La méthode d inversion directe a permis d obtenir une décomposition cinématique du disque qui présente une nette séparation entre le disque mince et le disque épais. Cependant, cette méthode présente un certain nombre de biais. Le modèle cinématique combine les comptages en magnitude obtenus à partir du catalogue 2MASS avec les mesures de mouvements propres du catalogue UCAC2 et de vitesses radiales de RAVE. Ce modèle est un modèle auto-cohérent qui relie la densité d étoiles aux dispersions de vitesse via le potentiel gravitationnel. La décomposition cinématique du disque galactique obtenu grâce au modèle montre clairement trois composantes : une première composante (disque mince) avec des dispersions de vitesses verticales ơW compris entre 10 et 25 km.s 1, une deuxième (disque épais) avec des dispersions de ơW 2 [30 45] km.s 1 et une troisième (disque épais sousmétallique ou halo) avec ơW 65 km.s 1. Les deux méthodes donnent une décomposition cinématique qui montre la même séparation cinématique entre les disques mince et épais. En conséquence, les scénarios qui envisagent la possibilité d un disque mince initial qui aurait été chauffé par des nuages moléculaires ou par les bras spiraux sont exclus par ces résultats. D autres mécanismes de formation du disque épais comme l accrétion progressive d étoiles venant de galaxies satellites ou le chauffage voire la création d étoiles au moment de la rencontre entre une galaxie satellite importante et notre galaxie restent possibles.This thesis work has focused on the Galactic disk kinematics to put some constraints on the scenarios of the thin and thick disk formation. It takes part of the RAVE project which has the goal to spectrocpically measure the radial velocities and the stellar parameters of one million stars in the South celestial hemisphere. To determine the kinematical characteristic of the disk, two methods have been used, the direct inversion of the stellar counts in function of distance and velocity and the kinematical modelling of the galactic disk. For the inversion, the photometric distance of stars have been determined from the apparent magnitude in doing an appropriate colour selection. The proper motions have been after transformed in velocity. The direct inversion method has permitted to obtain a kinematical decomposition of the galactic disk which presents a clear separation between the thin and the thick disk. Nevertheless, this method shows some bias. The kinematical model combines the counts in magnitude obtained from the 2MASS catalogue with the measures of proper motions of UCAC2 catalogue and of radial velocities of RAVE. This model is a self-consistent model which joins the stellar density with the velocity dispersions via the gravitational potential. The kinematical decomposition of the disk obtained from the model shows clearly three components : a first component (thin disk) with vertical velocity dispersion ơW between 10 and 25 km.s 1, second one (thick disk) with dispersions of ơW 2 [30 45] km.s 1 and third one (metal weak thick disk or halo) with ơW 65 km.s 1. The two methods give a kinematical decomposition which shows the same kinematical separation between the thin and thick disks. In consequence, the scenarios which offer the possibility of an initial thin disk which would had been " heated " by molecular clouds or spiral arms are ruled out by these results. Other mechanisms of the formation of the thick disk like progressive accretion of stars coming from satellite galaxies or the heating or the creation of stars during the encounter of an important satellite galaxy and our Galaxy remain possible.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF