Galactic archaeology using the thick disk of the Milky Way

Student: Joaquín García de la Cruz
Supervisor: Marie Martig

Disk galaxies like the Milky Way are made of several stellar components: a disk of course (with typically a thin and a thick part), and possibly also a bulge, a bar and a stellar halo (with various shapes and mass fractions). One of the big challenges in the field of galaxy formation is to understand the mechanisms creating these various components, and the origin the diverse galaxy populations we observe. Thick disks are particularly important in this context because they can be formed via a large range of processes (from internal to external, and slow to fast processes) and those different processes potentially leave different signatures in the shape, age and kinematics of the disks.

We are now at a perfect time to study the Milky Way, with the recent second data release of the Gaia mission containing precise parallaxes and proper motions for more than a billion stars. This project proposes to combine this unprecedented dataset with numerical simulations to uncover the formation history of the Milky Way using the structure of its thick disk.

First, cosmological simulations will be used to explore the connection between the formation history of a galaxy and the structure of its thick disk (in particular, the potential existence of a radial age gradient). Then,  Gaia data combined with information from spectroscopic surveys like APOGEE-2 and WEAVE will be combined to map the age structure and kinematics of the Milky Way’s thick disk. This should lead to a new understanding of the mechanisms driving the formation of thick disks, and to a better characterisation of the Milky Way’s history.