How Population III Supernovae Determined the Properties of the First Galaxies

Abstract

Massive Pop III stars can die as energetic supernovae that enrich the early universe with metals and determine the properties of the first galaxies. With masses of about $10^9$ Msun at $z \gtrsim 10$, these galaxies are believed to be the ancestors of the Milky Way. This paper investigates the impact of Pop III supernova remnants (SNRs) from both Salpeter-like and top-heavy initial mass functions (IMFs) on the formation of first galaxies with high-resolution radiation-hydrodynamical simulations with the ENZO code. Our findings indicate that SNRs from a top-heavy Pop III IMF produce more metals, leading to more efficient gas cooling and earlier Pop II star formation in the first galaxies. From a few hundred to a few thousand Pop II stars can form in the central regions of these galaxies. These stars have metallicities of $10^{-3}$ to $10^{-2}$, Zsun, greater than those of extremely metal-poor (EMP) stars. Their mass function follows a power-law distribution with $dN(M_*)/dM_* \propto M_*^{\alpha}$, where $M_*$ is stellar mass and $\alpha = 2.66 - 5.83$ and is steeper for a top-heavy IMF. We thus find that EMP stars were not typical of most primitive galaxies.