Abstract: Our Galaxy, the Milky Way, is the only one for which we have access to detailed 6D dynamical and chemical information of individual stars. Indeed, the Milky Way serves as a unique template to study the impact that accreted galaxies had on the evolutionary mechanisms of L★-galaxies, and the perturbations they generated. Yet, despite substantial progress in recent years, thanks in particular to the Gaia mission, our understanding of the formation history of the MW and of its progenitors is still in its infancy. The main limitation in searching for signatures of accreted galaxies stems from the substantial number of stars with spectroscopic measurements it requires. As such, current searches for past accretions are primarily conducted in the Solar vicinity, where contamination is high and where these signatures fade faster than at larger distances.
The incoming large spectroscopic surveys, such as WEAVE, 4-MOST, or DESI, are going to completely change this by providing spectroscopic measurements for hundreds of thousands of stars located at large distances, in the halo of our Galaxy, allowing us to search for signatures of smaller/older accretion, and to probe the gravitational potential until the outskirts of our Galaxy. In this talk, I will present recent works that have been conducted to better characterize our Galaxy and its history, thanks to new large-scale surveys that provide detailed dynamical and chemical information. I will also present the major improvements that the new generation of large, multi-aspect surveys will bring, to study both our Galactic history and the fundamental nature of dark matter, but also the challenges they are presenting.