Chemical characterisation is key to understanding the formation history of the Milky Way (MW) and its accretion events, yet major challenges remain at low metallicity. Neutron-capture elements show a large dispersion in very metal-poor MW stars that current chemical evolution models struggle to explain, possibly reflecting the diversity of accreted satellites. In this context, I investigate the role of the Sagittarius dwarf spheroidal galaxy (dSph) in the MW’s chemical evolution. I observed ~100 Sagittarius stars (−2 < Fe/H < −0.5) with GIRAFFE@FLAMES to derive precise abundances of the r-process element Eu and the s-process elements Y, Zr, Ba, and La. We compare these trends with those of other MW systems (Fornax, LMC, GSE, Sculptor) and with Icarus, a candidate accreted structure in the disk, for which we obtained a high-resolution follow-up sample with the high-resolution spectrograph HARPS-N. By combining multiple elemental families with the innovative technique of stellar phylogenetics, we aim to better trace the chemical signatures of past and ongoing merger events.
Sara Vitali (2026) studied this question.