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 der ive the distribution of the gaseous absorbing column densities among obscur ed active nuclei in the local universe. Of all Seyfert 2 galaxies in the sa mple, 75% are heavily obscured (N-H > 10(23) cm(-2)), and about half are Co mpton thick (N-H > 10(24) cm(-2)). Intermediate type 1.8-1.9 Seyfert galaxi es are characterized by an average N-H much lower than "strict" Seyfert 2 g alaxies. No correlation is found between N-H and the intrinsic luminosity o f the nuclear source. This N-H distribution has important consequences for the synthesis of the cosmic X-ray background. In addition, the large fracti on of Compton-thick objects implies that most of the obscuring gas is locat ed within a radius of a few 10 pc from the nucleus.