Live Fast, Die $\alpha$-Enhanced: The Mass-Metallicity-$\alpha$ Relation of the Milky Way's Disrupted Dwarf Galaxies

Understand

The Milky Way's satellite galaxies ("surviving dwarfs") have been studied for decades as unique probes of chemical evolution in the low-mass regime.

• Here we extend such studies to the "disrupted dwarfs", whose debris constitutes the stellar halo.
• We present abundances ([Fe/H], [$\alpha$/Fe]) and stellar masses for nine disrupted dwarfs with $M_{\star}\approx10^{6}-10^{9}M_{\odot}$ from the H3 Survey (Sagittarius, $Gaia$-Sausage-Enceladus, Helmi Streams, Sequoia, Wukong/LMS-1, Cetus, Thamnos, I'itoi, Orphan/Chenab).
• The surviving and disrupted dwarfs are chemically distinct: at fixed mass, the disrupted dwarfs are systematically metal-poor and $\alpha$-enhanced.