Neige Frankel

Neige Frankel  (France)

frankel @

Secular evolution of the Milky Way disk

What are the dominant processes driving the evolution of disk galaxies in the absence of strong external interactions? One of the possible mechanisms is radial migration: the interaction between spiral arms (and other non axisymmetric structures) and the stars in the disk, causing stars to scatter and
change orbits, to larger or smaller galactic radii, transporting their chemistry with them.
The current project's aim is to measure the efficiency of radial migration, for the Milky Way disk. Our Galaxy is a well suited laboratory to tackle this question, as it is thought to have lived a quiet life (no major merger) for the past 8 Gyr. Sitting inside its disk gives us the unique opportunity to study it star by star, and infer their individual parameters, such as metallicities, ages, and positions in the Galaxy. These three parameters have been provided for about 20 000 red clump (core helium burning) stars from the APOGEE survey for large ranges of Galactic radii and ages. Separately, chemo-dynamical simulations inspired the construction of statistical models, which predict the distribution of metallicity and stellar ages for any galactic radii. Equipped with the above data and such a model, including radial mixing (modeled as diffusion), we can, using very weak chemical tagging (that is, the assumption that the metallicity and age of a star tell us uniquely where it was born), measure how far stars get from their birth radii in function of time. This will give an estimate to the radial migration strength.

Supervisor:  Hans-Walter Rix (MPIA)

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