The Distribution of Absorbing Column Densities among Seyfert 2 Galaxies

We use hard X-ray data for an " optimal " sample of Seyfert 2 galaxies to derive the distribution of the gaseous absorbing column densities among obscured active nuclei in the local Universe. Of all Seyfert 2 galaxies in the sample, 75% are heavily obscured (N H > 10 23 cm −2) and about half are Compton thick (N H > 10 24 cm −2). Intermediate type 1.8–1.9 Seyferts are characterized by an average N H much lower than " strict " Seyfert 2s. No correlation is found between N H and the intrinsic luminosity of the nuclear source. This N H distribution has important consequences for the synthesis of the cosmic X-ray background. Also, the large fraction of Compton thick objects implies that most of the obscuring gas is located within a radius of a few 10 pc from the nucleus.