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The origin of stars in the Milky Way disc as revealed by their chemical patterns and kinematics

» mardi 24 novembre 2020

Proposition de stage au niveau M2.

Proposant : Paola Di Matteo (GEPI).

Subject : For Galactic studies, these years are exceptional. Thanks to the release of the first Gaia catalogue(s), the community has access to positions and parallaxes for 1.3 billions sources, and full velocity information (proper motion and radial velocity) for more than 7 millions stars as well as transverse velocity for the full set of 1.3 billion stars. These data -complemented by spectroscopic surveys– are a gold mine to derive the essential of stellar motions, chemo-dynamical relations, and ages for hundred thousands of stars, thus giving to the astronomical community the unprecedented opportunity to identify chemical patterns in the Galaxy, relate them to ages –when possible– and orbital properties, and build a coherent picture of its star formation history, mass assembly and evolution.
The current proposal aims at taking advantage of the unprecedented dataset, coupled to dynamical models that have been developed by our group over the last years, to quantify the signatures that bar resonances imprint in chemo-kinematic spaces, and use them to reconstruct the location of the main resonances in the Milky Way (hereafter MW) disc, and thus unravel the role they have played in the evolution of the MW over time. Resonances are indeed fundamental in the evolution of the disc of barred galaxies, like the MW. It is at the resonances that the angular momentum (hereafter AM) redistribution is mostly efficient. Stars at resonances with the bar/and or spiral arms are also subject to radial migration (i.e. to a change of their birth radii), and resonances also determine the direction of gas streaming motions in a disc. Their location can change over time, because of the decrease in the bar pattern speed caused mainly by the redistribution of AM between the disc and the dark matter halo. As a consequence, an increasingly larger portion of the disc can be interested by all the phenomena cited above. Because of the role played by resonances on the AM redistribution of stars and gas, they also concur to shape the star formation history of a galaxy disc and its chemical evolution, establishing a link between dynamical processes and chemical properties of stellar populations that is still only very marginally explored. It is exactly this link between kinematics and chemistry that we want to explore in this internship, by analyzing, first, a set of test-particle models of the Milky Way disc, where different properties the bar and its pattern speed are investigated.

Other potential subjects for internships, related to Milky Way modelling, are available. Interested candidates can directly address an email to Paola Di Matteo