Two Populations of Carbon-Enhanced Metal-Poor Stars in the Disk System of the Milky Way

Abstract

We present a chemo-dynamical analysis of low-resolution ($R\sim 1300$) spectroscopy of stars from the AAOmega Evolution of Galactic Structure (AEGIS) survey, focusing on two key populations of carbon-enhanced metal-poor (CEMP) stars within the disk system of the Milky Way: a mildly prograde population ($L_z<1000$kpckms${}^{-1}$) and a strongly prograde ($L_z>1000$kpckms${}^{-1}$) population. 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 (MWTD). We discuss their implications in the context of the formation history of the Milky Way.

9 pages, 2 figures