Near-Field Cosmology with Extremely Metal-Poor Stars

TLDR

The oldest, most metal‑poor stars in the Galactic halo and dwarf galaxies provide a window into the earliest star‑forming environments, and near‑field cosmology uses them to constrain the formation of the first stars and galaxies. The authors review stellar and dwarf galaxy archaeology by examining chemical abundance measurements in extremely metal‑poor stars to constrain early star and galaxy formation. The study reviews stellar and dwarf galaxy archaeology through analysis of chemical abundance measurements in extremely metal‑poor stars. Analysis of carbon‑rich and carbon‑normal halo stars, together with high‑redshift gas cloud abundances, indicates that Population III progenitors drove the first metal enrichment and suggests two distinct star‑formation channels in the earliest Universe.

Abstract

The oldest, most metal-poor stars in the Galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star forming environments in the Universe. We review the fields of stellar archaeology and dwarf galaxy archaeology by examining the chemical abundance measurements of various elements in extremely metal-poor stars. Focus on the carbon-rich and carbon-normal halo star populations illustrates how these provide insight into the Population III star progenitors responsible for the first metal enrichment events. We extend the discussion to near-field cosmology, which is concerned with the formation of the first stars and galaxies and how metal-poor stars can be used to constrain these processes. Complementary abundance measurements in high-redshift gas clouds further help to establish the early chemical evolution of the Universe. The data appear consistent with the existence of two distinct channels of star formation at the earliest times.