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Stars with borders : Migration in the Galactic disc

Proposition de stage au niveau L3 à M2.

Proposant : Paola Di Matteo (GEPI).

Subject : Disc galaxies like our own evolve over their lifetime through a variety of processes. Some of these processes depend on the environment the galaxy is in : accretions of satellites, gas feeding from the inter-galactic medium. Some other processes are more directly related to their internal evolution : the presence of asymmetries like stellar bars and/or spiral arms can cause stars to change their initial orbits and to migrate towards the inner and outer regions of the disc, far from their initial birthplace. This process, known as “radial migration” has received much attention over the last decade, because it can have an important impact on the properties of disc galaxies that we observe today (chemical abundance gradients, age distributions, kinematics). The Milky Way offers a great opportunity to study the strength and significance of this process in Galactic evolution : from the detailed knowledge of the chemistry of its stars, we can potentially reconstruct the amount of migration it can have experienced over time. Recently (Hallé et al 2015) we have shown that stars do encounter borders in their radial migration through the disc, and that the outer resonance of the stellar bar acts as a barrier limiting migration between the inner and outer regions of the disc.

In this internship we want to test the consequence of this result on the chemistry of stars in the disc, by analyzing a set of N-body simulations of Milky Way type-galaxies evolved over a period of several Gyrs. The interested student will learn the basics of Galactic stellar populations and dynamics, and how to approach the analysis of N-body simulations, producing density and metallicity maps, estimating radial metallicity gradients, and their change with time.