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

Abstract

We obtained new quantitative determinations of the nitrogen abundance anda consistent relation between 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 re-produce 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 vs. O/H abundance ratios derived for Seyfert 2 galaxies are in consonance with those recently derived for a sample of extragalactic disk Hii regions with high metallicity.