Explaining the high nitrogen abundances observed in high-z galaxies via population III stars of a few thousand solar masses

TL;DR

This paper demonstrates that extremely massive Population III stars, over 2000 solar masses, can explain the high nitrogen and other elemental abundances observed in early high-redshift galaxies, using advanced simulations and stellar models.

Contribution

It introduces a novel model showing that supermassive Pop III stars can account for observed chemical signatures in high-z galaxies, bridging a gap in understanding early universe enrichment.

Findings

Pop III stars of 2000-9000 Msol produce observed N/O, C/O, O/H ratios.

The model reproduces high-z galaxy elemental abundances accurately.

Ejecta mainly consist of He, H, and N, matching observations.

Abstract

The chemical enrichment of the early Universe is a crucial element in the formation and evolution of galaxies, and Population III (PopIII) stars must play a vital role in this process. In this study, we examine metal enrichment from massive stars in the early Universe's embryonic galaxies. Using radiation hydrodynamic simulations and stellar evolution modelling, we calculated the expected metal yield from these stars. Specifically, we applied accretion rates from a previous radiation-hydrodynamic simulation to inform our stellar evolution modelling, executed with the Geneva code, across 11 selected datasets, with final stellar masses between 500 and 9000 Msol. Our results demonstrate that the first generation of Pop III stars within a mass range of 2000 to 9000 Msol result in N/O, C/O and O/H ratios compatible with the values observed in very high-z galaxies GN-z11 and CEERS 1019. The ejecta of these Pop III stars are predominantly composed of He, H, and N. Our Pop III chemical enrichment model of the halo can accurately reproduce the observed N/O and C/O ratios, and, by incorporating a hundred times more zero-metallicity interstellar material with the stellar ejecta, it accurately attains the observed O/H ratio. Thus, a sub-population of extremely massive PopIII stars, with masses surpassing approximately 2000 Msol, effectively reproduces the CNO elemental abundances observed in high-z JWST galaxies to date.