On the metal abundance of low-activity galactic nuclei

Abstract

The characteristics of the nuclear spectrum of six Seyfert 2 and LINER nuclei with low activity and strong !ines of ionized nitrogen are investigated. From the equivalent widths of the absorption !ines, the age and metallicity of the stellar population are derived. A comparison of the observed emission-line intensities with photoionization and shock model calculations leads to the conclusion that these nuclei are photoionized by a power-law continuum, and that the only way to reproduce the large [N n]/H(X ratio for at least four of them is with an overabundance of nitrogen relative to the other heavy elements.