The Atari Disk, a Metal-Poor Stellar Population in the Disk System of the Milky Way

Understand

We have developed a chemo-dynamical approach to assign 36,010 metal-poor SkyMapper stars to various Galactic stellar populations.

• Using two independent techniques (velocity and action space behavior), $Gaia$ EDR3 astrometry, and photometric metallicities, we selected stars with the characteristics of the "metal-weak" thick disk population by minimizing contamination by the canonical thick disk or other Galactic structures.
• This sample comprises 7,127 stars, spans a metallicity range of $-3.50<${\metal}~$<-0.8$, and has a systematic rotational velocity of $\langle V_\phi\rangle=154$\,km\,s$^{-1}$ that lags that of the thick disk.
• Orbital eccentricities have intermediate values between typical thick disk and halo values.