Distant Echoes of the Milky Way's Last Major Merger

Understand

The majority of the Milky Way's stellar halo consists of debris from our Galaxy's last major merger, the Gaia-Sausage-Enceladus (GSE).

• In the past few years, stars from GSE have been kinematically and chemically studied in the inner $30$ kpc of our Galaxy.
• However, simulations predict that accreted debris could lie at greater distances, forming substructures in the outer halo.
• Here we derive metallicities and distances using Gaia DR3 XP spectra for an all-sky sample of luminous red giant stars, and map the outer halo with kinematics and metallicities out to $100$ kpc.