The Chandra and XMM-Newton view of optically defined samples of Compton-thick Seyfert 2 galaxies

M. Guainazzi

In this talk I will present the results of two programs: a) a Chandra and XMM-Newton survey of an optically defined, unbiased sample of Compton-thick Seyfert 2 galaxies; b) a XMM-Newton survey of a sample of Seyfert 2 galaxies, selected according to the properties of their nuclear dust in high-resolution HST images. The results of these programs, once compared with Monte-Carlo radiative transfer simulations, support an extension of the Seyfert unification scenario, whereby the torus affect X-ray obscuration in Compton-thick Seyfert 2s only, whereas obscuration in Compton-thin AGN is due to matter located at larger distances, possibly related to the host galaxy rather than to the nuclear environment. As a by-product of this study, I will estimate how the emission in the soft X-ray regime, largely exceeding the extrapolation of the obscured AGN emission in a significant fraction of both samples, may affect the AGN population distribution derived from deep X-ray surveys.