Two Populations of Carbon-enhanced Metal-poor Stars in the Disk System of the Milky Way

We present a chemodynamical analysis of low-resolution (R similar to 1300) spectroscopy of similar to 50,000 stars from the AAOmega Evolution of Galactic Structure survey, focusing on two key populations of (in total) 650 carbon-enhanced metal-poor (CEMP) stars within the disk system of the Milky Way: a mildly prograde population (L ( z ) < 1000 kpc km s(-1)) and a strongly prograde population (L ( z ) > 1000 kpc km s(-1)). Based on their chemical and kinematic characteristics, and on comparisons with similar populations found in the recent literature, we tentatively associate the former with an ex situ inner-halo population originating from either the Gaia Sausage or Gaia-Enceladus. The latter population is linked to the metal-weak thick disk. We discuss their implications in the context of the formation history of the Milky Way.

Automated summary

This study examines the chemodynamic characteristics of about 50,000 stars from the AAOmega Evolution of Galactic Structure survey, focusing on 650 carbon-enhanced metal-poor (CEMP) stars, and divides them into mildly prograde and strongly prograde populations, comparing them with similar populations in recent literature. The results suggest that the former may be associated with either the Gaia Sausage or Gaia-Enceladus, while the latter is linked to the metal-weak thick disk in the Milky Way.