The Poor Old Heart of the Milky Way
Hans-Walter Rix, Vedant Chandra, Ren\'e Andrae, Adrian M., Price-Whelan, David H. Weinberg, Charlie Conroy, Morgan Fouesneau, David W., Hogg, Francesca De Angeli, Rohan P. Naidu, Maosheng Xiang, Daniela, Ruz-Mieres

TL;DR
This study uncovers a significant, ancient, and metal-poor stellar population in the Milky Way's core using Gaia DR3 data, revealing insights into the galaxy's early formation and assembly history.
Contribution
It provides the first comprehensive analysis of the metal-poor stellar core of the Milky Way using Gaia XP spectra and orbit data, highlighting its extent, composition, and origin.
Findings
Identifies ~18,000 stars with -2.7 < [M/H] < -1.5 in the Galactic center.
Shows these stars are mostly confined within 2.7 kpc of the center.
Reveals different kinematic and chemical properties indicating diverse origins.
Abstract
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 mag) giant stars within of the Galactic Center with robust [M/H] estimates, [M/H] . For most sample members we can calculate orbits based on Gaia RVS velocities and astrometry. This sample reveals an extensive, ancient, and metal-poor population that includes …
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Taxonomy
TopicsAstronomy and Astrophysical Research · Stellar, planetary, and galactic studies · Astrophysics and Star Formation Studies
