Abstract

Contributed Talk - Splinter Galaxies   (MW-0250)

How Population III Supernovae Determined the Properties of the First Galaxies

Ke-Jung Chen
ASIAA/HITS

Massive Population III stars likely ended their lives as energetic supernovae that enriched the early Universe with the first heavy elements and shaped the formation of the first galaxies. These galaxies, with typical masses of about one billion solar masses at redshifts z ≳ 10, are thought to be the progenitors of present-day galaxies such as the Milky Way. In this talk, I present high-resolution radiation-hydrodynamical simulations of the impact of Population III supernova remnants (SNRs) on the assembly of the first galaxies, performed with the ENZO code. We explore enrichment from both Salpeter-like and top-heavy Population III initial mass functions (IMFs). We find that supernovae originating from a top-heavy Population III IMF inject substantially more metals into their host galaxies, leading to enhanced gas cooling and earlier onset of Population II star formation. As a result, the first galaxies can form from several hundred to several thousand Population II stars within their central regions. These stars typically reach metallicities of 10^-3 to 10^-2 times the solar value, significantly higher than those observed in extremely metal-poor stars in the local Universe. Their stellar mass function follows a power-law distribution, dN/dM ∝ M^−α, with α ranging from 2.66 to 5.83, and becomes steeper in galaxies enriched by a top-heavy Population III population. Our results suggest that the nature of the first supernovae strongly influences the chemical and stellar properties of the first galaxies. In particular, we find that extremely metal-poor stars were likely not representative of the stellar populations that formed in most primitive galaxies, highlighting the need for caution when using local metal-poor stars as direct probes of the first galaxies.