22) Tracing the formation history of simulated Milky Way analogues

Abstract: The kinematics of the most metal-poor stars provide a unique tool to unveil the infancy and accretion history of the MW. Using high-resolution cosmological zoom-in simulations of MW-like galaxies I investigate the structure of their stellar disks. Applying non-parametric gaussian-mixture-models to the kinematics and abundances of the stars we are able to disentangle different galactic components such as bulge, thin/thick disk or stellar halo. Tracing the origin of their constituting stars we are able to investigate the formation history of the different components. In particular we focus on the origin of low-metallicity stars ([Fe/H] < -2.5). The simulations reproduce the observational signature of a population of low-metallicity stars confined to the disk plane, as recently discovered in the MW. Independently of the accretion history of the simulations, we find that >~90 percent of the retrograde stars of this population are brought in during the initial build-up of the galaxies during the first few Gyrs after the Big Bang. The prograde, planar population on the other hand is in large parts accreted during the later assembly phase. We relate the kinematic feature of eccentric, metal-poor disk stars as seen in the MW to an accretion history of multiple massive mergers. This potentially implies that also our Galaxy might have experienced a more violent accretion history.

Bio: Tobias Buck studied Astrophysics at the University of Heidelberg and graduated in October 2018 defending his PhD thesis entitled On the formation of the MW system in cosmological context.
Since December 2018 he is a postdoc at the Leibniz Institut für Astrophysik in Potsdam working in the cosmology group of Prof. Christoph Pfrommer.