Accreted debris in the Milky Way's local stellar halo
Emma Dodd (Durham University)
Tuesday 13/05/2025 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
Galaxy stellar haloes, including the Milky Way, are known to have built up through the accretion of smaller systems, with stars from a single merger being deposited onto similar orbits. Since orbits can be characterised by their integrals of motion stellar debris from past accretion events can be identified as over-densities in these spaces. With the latest data release of Gaia (DR3), we have an updated view of the substructures within the local stellar halo. However, for many of these substructures, their nature or characterisation remained rather limited. I will present some recent efforts to address this. For the larger substructures, it has become feasible through the combination of Gaia data and CMD (colour-magnitude diagram) fitting techniques, to characterise their stellar populations, including deriving age distributions. This enables us to place constraints on the star formation histories of the now-destroyed dwarf galaxies and construct a timeline for the accretion events that dominate the local stellar halo. For the smaller, newly identified substructures whose nature was previously unclear, I will highlight the results of chemical follow-up through targeted high-resolution UVES spectroscopy and the importance of high-precision and homogeneous chemical abundances in disentangling distinct accretion events. The combination of these efforts is providing us with an updated view of the Milky Way's assembly history.