The last decade of galactic archaeology has been transformed by a wealth of data from the Gaia mission and large-scale spectroscopic surveys. These have enabled the identification of past mergers, such as the Gaia Enceladus/Sausage. Because ancient accretion events are phase-mixed in position-space, approximately conserved quantities – such as energy and angular momentum – are used alongside stellar chemistry to facilitate the search for merger remnants. The centre of the Milky Way is receiving increasing attention in the search for the very oldest building blocks of our Galaxy, as most old, metal-poor stars are concentrated there. However, this region presents significant challenges due to its high-density environment. To help disentangle the competing signatures at the heart of the Galaxy, we utilise the ultra-high-resolution Auriga Superstars suite of hydrodynamical cosmological zoom-in simulations, which provide Milky Way-analogues with fully known formation histories. Our findings highlight two primary obstacles in uncovering the Galaxy’s history. Firstly, the "proto-galaxy" stage is characterised by a rapid succession of similar-mass mergers. This creates a dominant, well-mixed component at low energies where chemical enrichment across different progenitors is nearly indistinguishable. Secondly, the Galactic bar generates prominent substructures – such as ridges in energy and angular momentum space – by trapping stars in resonant orbits. While these resonant features provide clues to the Galaxy’s secular evolution, they further mask the signatures of early accretion events.
Shaken and Stirred : How Mergers and the Bar Shaped the Galaxy’s History
Mercredi 25 mars 2026
de
14:30 à
16:00
Conference room, building 17
