Spectral synthesis of the nuclear regions of Seyfert 2 and radio galaxies

We present the results of an optical spectral synthesis analysis for the nu clei of 20 Seyfert 2 and four radio galaxies, using a base of stellar popul ation templates of different ages and metallicities and a power-law continu um. Compared with the stellar population of elliptical galaxies, we find th at Seyfert 2s usually have a smaller contribution from old metal-rich stars (age 10 Gyr, Z greater than or similar to Z.), and a larger contribution f rom stars with ages of 100 Myr, We also find that the contributions from st ars with ages less than or equal to 10 Myr and from a power-law continuum a re small, rarely exceeding 5 per cent, These results show that the general assumption of elliptical galaxies as stellar population templates for these objects is incorrect, also implying that the excess blue continuum frequen tly found in their nuclear spectra is probably due to this template mismatc h. We find a considerable contribution from 100-Myr-old stars (approximate to 5 per cent), which can be interpreted from the point of view of models w here the fuelling of the AGN is carried out by interactions/mergers.