The stellar population and emitting gas in the inner 2-5 kpc for a sample of nine Seyfert 2 galaxies

Abstract

We analyse the stellar population and the emitting gas in the inner 2-5 kpc of a sample of nine Seyfert 2 galaxies, using 5-Å resolution spectra in the range 3600-7000 Å. The typical population is old and moderately stronglined, except in IC 5135 which presents star-forming events. The emission-line spectrum is studied after subtraction of the stellar population. Broad Hα components (FWHM = 2000 km s - 1 ) were found for five of the galaxies. The line widths correlate with the criticai densities for the forbidden lines in four of the galaxies and with the ionization potential in three of these, indicating the presence of density stratification and ionization structure. Comparison of our emission-line ratios with smaller aperture data obtained from the literature reveal important changes in the values due to contamination by surrounding gas. Using photo-ionization models we derive gas abundances between solar and two-times solar, with an overabundance of nitrogen in NGC 4939 and 6890, and of nitrogen and sulphur in NGC 1667, relative to the other heavy elements.