Description
The oldest, most metal-poor stars in and around the Milky Way were born in pristine environments in the early Universe. Observations of local very metal-poor stars ([Fe/H] < -2.0) show that many of these stars have exceptionally high carbon abundances. These carbon-enhanced metal-poor (CEMP) stars consist of two main classes: the CEMP-no stars are thought to have been born carbon-rich, reflecting the composition of the interstellar medium enriched by the First Stars, whereas the CEMP-s stars, which are also enhanced in s-process elements and are usually found to be in binary systems, are thought to be the result of mass-transfer from a former asymptotic giant branch star companion.
Spectroscopic surveys in recent years have uncovered large numbers of CEMP stars, allowing us to begin to study them as a population. There are hints that the properties of CEMP populations vary between different Galactic environments (inner/outer halo, bulge, dwarf galaxies, globular clusters), which could point to differences in the early formation and chemical evolution of these environments. I will present an overview of what we know about CEMP populations in different environments, with a focus on the inner Milky Way — the oldest part of our Galaxy, with early conditions potentially similar to those in high-redshift galaxies.
