# N/O abundance ratios in gamma-ray burst and supernova host galaxies at z<4. Comparison with AGN, starburst and HII regions

## TL;DR

This study investigates the distribution of nitrogen-to-oxygen (N/O) abundance ratios in gamma-ray burst and supernova host galaxies at redshifts below 4, comparing them with active galactic nuclei, starburst, and HII regions to understand galaxy chemical evolution.

## Contribution

It provides detailed modeling of N/O ratios across different galaxy types and redshifts, revealing how these ratios evolve and relate to star formation histories and galaxy activity.

## Key findings

- N/O in SN hosts increases at low redshift due to secondary N production.
- N/O in LGRB hosts decreases with redshift, reaching values similar to local HII regions.
- Some LGRB hosts fit star multi-bursting models, while SN hosts at certain metallicities are not well explained by existing models.

## Abstract

The distribution of N/O abundance ratios calculated by the detailed modelling of different galaxy spectra at z<4 is investigated. Supernova (SN) and long gamma-ray-burst (LGRB) host galaxies cover different redshift domains. N/O in SN hosts increases due to secondary N production towards low z (0.01) accompanying the growing trend of active galaxies (AGN, LINER). N/O in LGRB hosts decreases rapidly between z>1 and z ~0.1 following the N/H trend and reach the characteristic N/O ratios calculated for the HII regions in local and nearby galaxies. The few short period GRB (SGRB) hosts included in the galaxy sample show N/H <0.04 solar and O/H solar. They seem to continue the low bound N/H trend of SN hosts at z<0.3. The distribution of N/O as function of metallicity for SN and LGRB hosts is compared with star chemical evolution models. The results show that several LGRB hosts can be explained by star multi-bursting models when 12+log(O/H) <8.5, while some objects follow the trend of continuous star formation models. N/O in SN hosts at log(O/H)+12 <8.5 are not well explained by stellar chemical evolution models calculated for starburst galaxies. At 12+log(O/H) >8.5 many different objects are nested close to O/H solar with N/O ranging between the maximum corresponding to starburst galaxies and AGN and the minimum corresponding to HII regions and SGRB.