The Poor Old Heart of the Milky Way

Understand

Massive disk galaxies like our Milky Way should host an ancient, metal-poor, and centrally concentrated stellar population.

• This population reflects the star formation and enrichment in the few most massive progenitor components that coalesced at high redshift to form the proto-Galaxy.
• While metal-poor stars are known to reside in the inner few kiloparsecs of our Galaxy, current data do not yet provide a comprehensive picture of such a metal-poor "heart" of the Milky Way.
• We use information from Gaia DR3, especially the XP spectra, to construct a sample of 2 million bright (BP $<15.5$ mag) giant stars within $30^\circ$ of the Galactic Center with robust [M/H] estimates, $\delta$ [M/H] $\lesssim 0.1$.