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

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.