X-ray obscuration and obscured AGN in the local universe

We discuss the X-ray properties of 49 local (z < 0.035) Seyfert 2 galaxies with HST/WFC2 high-resolution optical coverage. It includes the results of 26 still unpublished Chandra and XMM-Newton observations, which yield 25 (22) new X-ray detections in the 0.5-2 keV (2-10 keV) energy band. Our sample covers a range in the 2-10 keV observed flux, F2-10, from 3 x 10(-11) to 6 x 10(-15) erg cm(-2) s(-1). The percentage of objects that are likely obscured by Compton-thick matter ( column density, N-H >= sigma(t)(-1) similar or equal to 1.6 x 10(24) cm(-2)) is similar or equal to 50%, and reaches similar or equal to 80% for log (F2-10) < 12.3. Hence, K-alpha fluorescent iron lines with large Equivalent Width (EW > 0.6 keV) are common in our sample ( 6 new detections at a confidence level >= 2 sigma). They are explained as due to reflection off the illuminated side of optically thick material. We confirm a correlation between the presence of a similar to 100-pc scale nuclear dust in the WFC2 images and Compton-thin obscuration. We interpret this correlation as due to the large covering fraction of gas associated with the dust lanes. The X-ray spectra of highly obscured AGN invariably present a prominent soft excess emission above the extrapolation of the hard X-ray component. This soft component can account for a very large fraction of the overall X-ray energy budget. As this component is generally unobscured - and therefore likely produced in extended gas structures - it may lead to a severe underestimation of the nuclear obscuration in z similar to 1 absorbed AGN, if standard X-ray colors are used to classify them. As a by-product of our study, we report the discovery of a soft X-ray, luminous (similar or equal to 7 x 10(40) erg s(-1)) halo embedding the interacting galaxy pair Mkn 266.