Baseline metal enrichment from Population III star formation in cosmological volume simulations

We utilize the hydrodynamic and N-body code GIZMO coupled with our newly developed subgrid Population III (Pop III) Legacy model, designed specifically for cosmological volume simulations, to study the baseline metal enrichment from Pop III star formation at z > 7. In this idealized numerical experiment, we only consider Pop III star formation. We find that our model Pop III star formation rate density (SFRD), which peaks at similar to 10(-3) M-circle dot yr(-1) Mpc(-1) near z similar to 10, agrees well with previous numerical studies and is consistent with the observed estimates for Pop II SFRDs. The mean Pop III metallicity rises smoothly from z = 25 to 7, but does not reach the critical metallicity value, Z(crit) = 10(-4) Z(circle dot), required for the Pop III to Pop II transition in star formation mode until z similar or equal to 7. This suggests that, while individual haloes can suppress in situ Pop III star formation, the external enrichment is insufficient to globally terminate Pop III star formation. The maximum enrichment from Pop III star formation in star-forming dark matter haloes is Z similar to 10(-2) Z(circle dot), whereas the minimum found in externally enriched haloes is Z greater than or similar to 10(-7) Z(circle dot). Finally, mock observations of our simulated IGM enriched with Pop III metals produce equivalent widths similar to observations of an extremely metal-poor damped Lyman alpha system at z = 7.04, which is thought to be enriched by Pop III star formation only.