Galaxies are complex systems governed by competing physical processes that happen on very different space, time and energy scales, such as mergers, internal secular evolution, gas flows, star formation, supernova feedback, gas cooling etc. The field of Galactic archaeology aims at disentangling these processes, eventually unfolding the detailed formation history of the Milky Way by resolving all Galactic components and substructures and studying them in greatest possible detail.
The main challenge of Galactic archaeology today is to unravel the Milky Way’s assembly and evolution history by determining ages, chemical compositions, and kinematics of millions of stars covering all parts of the Milky Way. Major observing campaigns of the last decade, and the success of the Gaia mission, have assured that this is in principle possible: precise radial velocities as well as basic chemical information for millions of stars have already been obtained by surveys such as RAVE, SEGUE, APOGEE, LAMOST, GALAH, or the Gaia-ESO survey. In the near future, even bigger projects like 4MOST, WEAVE, and MOONS will allow us to look even deeper into the stellar components of the Milky Way. Gaia, on the other hand, allows us to measure parallaxes and transverse kinematics for more than a billion stars for the first time with unprecedented precision; the second Gaia data release (DR2), published in April 2018, represented a huge leap for precision astrometry. The combination of Gaia with public spectroscopic surveys is a goldmine for stellar and Galactic astrophysicists – and the ideal testbench for present-day and next-generation Milky-Way models.
We undertake a major analysis project exploiting Gaia and complementary spectroscopic survey data to constrain Galactic models, and to simultaneously provide the community with legacy tools and datasets that will greatly facilitate such studies in the future. The project has produced several catalogues of precise stellar parameters, distances, and extinctions for more millions of Milky Way stars. All data products are made publically available.
