Origin of nitrogen enhancement in early galaxies

Determine the physical mechanism responsible for nitrogen enhancement in a subset of early galaxies, including whether very massive-star winds, supermassive stars, or alternative processes dominate.

Background

GN-z11 and several other high-redshift galaxies show strong nitrogen emission and enhanced N/O ratios. The paper considers enrichment by winds from very massive or Wolf–Rayet-like stars, luminous-blue-variable-like eruptions, supermassive stars, and other mechanisms. Although the observed broad N IV] component provides evidence about the relevant stellar or nuclear environments, the enrichment mechanism itself is not established.

References

The physics responsible for nitrogen-enhancements in a subset of early galaxies remains unclear.

— SPURS: Massive Stars, Dense Gas, and Ly$α$ Escape in GN-z11 at $z = 10.6$  (2608.12699 - Chen et al., 13 Aug 2026) in Section 7.2, The Origin of Broad N IV] in GN-z11

Whether the nitrogen lines are common in LRDs is not known, nor is it clear what mechanism produces the peculiar abundances in LRDs.

— SPURS: An Ultra-deep View Inside the Compact, Nitrogen-Enriched Nuclei of Little Red Dots  (2609.11094 - Tang et al., 10 Sep 2026) in Section 1, Introduction

Whether these trace winds are powered by massive stars or an AGN is not clear, but in either case the winds may be important for delivering the nitrogen-enhanced abundance pattern to the ISM, as suggested in \citet{Chen2026b}.

— SPURS: An Ultra-deep View Inside the Compact, Nitrogen-Enriched Nuclei of Little Red Dots  (2609.11094 - Tang et al., 10 Sep 2026) in Section 4.3, Characterizing Massive Star Features in LRDs

Whether the nitrogen-emitting galaxies also harbor supermassive black holes in their nuclei remains debated \citep[e.g.,][]{Larson2023,Maiolino2024a}.

— SPURS: An Ultra-deep View Inside the Compact, Nitrogen-Enriched Nuclei of Little Red Dots  (2609.11094 - Tang et al., 10 Sep 2026) in Section 4.4, Nitrogen Emission in LRDs