Can pre-supernova winds from massive stars enrich the interstellar medium with nitrogen at high redshift?

TL;DR

This paper demonstrates that pre-supernova winds from rotating massive stars can explain the observed nitrogen enrichment and N/O ratio behavior in high-redshift galaxies, highlighting a key process in early galaxy chemical evolution.

Contribution

It introduces models showing that pre-supernova winds from rotating massive stars account for nitrogen enrichment and N/O ratios at high redshift, challenging supernova-dominated enrichment scenarios.

Findings

Models reproduce the observed N/O plateau at high redshift.

Scatter in N/O ratios is explained by varying star formation efficiency.

Dwarf galaxies likely lack supernova yields and are enriched mainly by stellar winds.

Abstract

Understanding the nucleosynthetic origin of nitrogen and the evolution of the N/O ratio in the interstellar medium is crucial for a comprehensive picture of galaxy chemical evolution at high-redshift because most observational metallicity (O/H) estimates are implicitly dependent on the N/O ratio. The observed N/O at high-redshift shows an overall constancy with O/H, albeit with a large scatter. We show that these heretofore unexplained features can be explained by the pre-supernova wind yields from rotating massive stars (M$\gtrsim 10 \, \mathrm{M}_\odot$, $v/v_{\rm{crit}} \gtrsim 0.4$). Our models naturally produce the observed N/O plateau, as well as the scatter at low O/H. We find the scatter to arise from varying star formation efficiency. However, the models that have supernovae dominated yields produce a poor fit to the observed N/O at low O/H. This peculiar abundance pattern at low O/H suggests that dwarf galaxies are most likely to be devoid of SNe yields and are primarily enriched by pre-supernova wind abundances.