SPECTROSCOPY OF SEYFERT-2 GALAXIES, LINERS, AND H-II GALAXIES

We present here 46 optical spectra of active objects, including Seyfer t 2 galaxies (Sy 2), H II galaxies, and LINERs (Low Ionization Nuclear Emission-line Region), observed with low resolution (4 Angstrom) at L NA/CNPq in 1991 and 1994. The extraction of the stellar contribution d ue to the host galaxy is made through the subtraction of templates bui lt from a stellar population synthesis in normal nuclei of S and E/S0 galaxies (Bica 1988, A&A, 195, 76). In Sy 2 and LINERs, an old high me tallicity population is predominant, while in H II galaxies, as expect ed, a younger population predominates. The residual optical continuum of the Sy 2 and LINERs approaches a power law and may correspond to a nonthermal radiation originating in the galactic center. However, the determination of the corresponding spectral index is strongly dependen t on the stellar population subtraction. The emission-line intensities are also presented, and were obtained after the stellar population su btraction. The enhancement of H beta and [NI] lambda 5200, relative to the unprocessed spectra, is significant (20% and 40% on the average, respectively). The decrease in intensity of He I lambda 5876 (15% on t he average) is very important, since it is usually used to calculate t he helium abundance in extragalactic H II regions, from which the He p rimordial abundance is inferred. (C) 1997 American Astronomical Societ y.