New quantitative nitrogen abundance estimations in a sample of Seyfert 2 active galactic nuclei

Abstract

We obtained new quantitative determinations of the nitrogen abundance and a consistent relation between the nitrogen and oxygen abundances for a sample of Seyfert 2 galaxies located at redshift z < 0.1. We carried out this analysis using the CLOUDY code to build detailed photoionization models. We were able to reproduce observed optical narrow emission line intensities for 44 sources compiled from the literature. Our results show that Seyfert 2 nuclei have nitrogen abundances ranging from ∼0.3 to ∼7.5 times the solar value. We derived the relation log (N/H) = 1.05( ± 0.09) × [log (O/H)] − 0.35( ± 0.33). Results for N/O versus O/H abundance ratios derived for Seyfert 2 galaxies are in consonance with those recently derived for a sample of extragalactic disc H II regions with high metallicity.