Revisiting The First Galaxies: The effects of Population III stars on their host galaxies

TL;DR

This study uses advanced hydrodynamic simulations to explore how Population III stars influenced early galaxy formation, revealing their short-lived dominance and limited impact on intergalactic metal enrichment.

Contribution

It introduces a new model for Population III star formation in galaxy-scale simulations based on primordial cloud collapse results.

Findings

Pop III stars' influence is short-lived, lasting less than 10^8 years.

Galaxies re-accrete baryons and transition to Pop II star formation after Pop III epoch.

Metals from Pop III supernovae mostly fall back, limiting intergalactic enrichment.

Abstract

We revisit the formation and evolution of the first galaxies using new hydrodynamic cosmological simulations with the ART code. Our simulations feature a recently developed model for H2 formation and dissociation, and a star formation recipe that is based on molecular rather than atomic gas. Here, we develop and implement a recipe for the formation of metal-free Population III stars in galaxy-scale simulations that resolve primordial clouds with sufficiently high density. We base our recipe on the results of prior zoom-in simulations that resolved the protostellar collapse in pre-galactic objects. We find the epoch during which Pop III stars dominated the energy and metal budget of the first galaxies to be short-lived. Galaxies which host Pop III stars do not retain dynamical signatures of their thermal and radiative feedback for more than 10^8 yr after the lives of the stars end in pair-instability supernovae, even when we consider the maximum reasonable efficiency of the feedback. Though metals ejected by the supernovae can travel well beyond the virial radius of the host galaxy, they typically begin to fall back quickly, and do not enrich a large fraction of the intergalactic medium. Galaxies with total mass in excess of 3 x 10^6 Msun re-accrete most of their baryons and transition to metal-enriched Pop II star formation.