Monty, StephanieStephanieMontyBelokurov, VasilyVasilyBelokurovSanders, Jason LJason LSandersHansen, Terese TTerese THansenSakari, Charli MCharli MSakariMcKenzie, MadeleineMadeleineMcKenzieMyeong, GyuChulGyuChulMyeongDavies, Elliot YElliot YDaviesArdern-Arentsen, AnkeAnkeArdern-ArentsenMASSARI, DAVIDEDAVIDEMASSARI2024-12-172024-12-1720240035-8711http://hdl.handle.net/20.500.12386/35506We combine stellar orbits with the abundances of the heavy, 𝑟-process element europium and the light, 𝛼-element, silicon to separate in-situ and accreted populations in the Milky Way across all metallicities. At high orbital energy, the accretion-dominated halo shows elevated values of [Eu/Si], while at lower energies, where many of the stars were born in-situ, the levels of [Eu/Si] are lower. These systematically different levels of [Eu/Si] in the MW and the accreted halo imply that the scatter in [Eu/𝛼] within a single galaxy is smaller than previously thought. At the lowest metallicities, we find that both accreted and in-situ populations trend down in [Eu/Si], consistent with enrichment via neutron star mergers. Through compiling a large dataset of abundances for 54 globular clusters (GCs), we show that differences in [Eu/Si] extend to populations of in-situ/accreted GCs. We interpret this consistency as evidence that in 𝑟-process elements GCs trace the star formation history of their hosts, motivating their use as sub-Gyr timers of galactic evolution. Furthermore, fitting the trends in [Eu/Si] using a simple galactic chemical evolution model, we find that differences in [Eu/Si] between accreted and in-situ MW field stars cannot be explained through star formation efficiency alone. Finally, we show that the use of [Eu/Si] as a chemical tag between GCs and their host galaxies extends beyond the Local Group, to the halo of M31 - potentially offering the opportunity to do Galactic Archaeology in an external galaxy.STAMPAenArticle10.1093/mnras/stae1895https://academic.oup.com/mnras/article/533/2/2420/7730250FIS/05 - ASTRONOMIA E ASTROFISICA