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Formation du disque de la Voie Lactée

Abstract : 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 between 10 and 25 km.s−1, second one (thick disk) with dispersions of [30 − 45] km.s−1 and third one (metal weak thick disk or halo) with dispersion of 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.
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Contributor : Lionel Veltz <>
Submitted on : Tuesday, January 29, 2008 - 12:09:23 PM
Last modification on : Monday, October 19, 2020 - 10:57:25 AM
Long-term archiving on: : Thursday, September 27, 2012 - 5:45:59 PM


  • HAL Id : tel-00222104, version 1



Lionel Veltz. Formation du disque de la Voie Lactée. Astrophysique [astro-ph]. Université Louis Pasteur - Strasbourg I, 2007. Français. ⟨tel-00222104⟩



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