X-ray absorption in Seyfert 2 galaxies

We have studied the correlation among X-ray absorption, optical reddening a nd nuclear dust morphology in Seyfert 2 galaxies. Two main conclusions emer ge: (i) the Balmer decrement and the amount of X-ray absorption are anticor related over a wide range of column density, 10(21) less than or similar to N-H less than or similar to 10(24) cm(-2) - the correlation no longer appl ies to Compton-thick objects (N-H greater than or similar to 10(24) cm(-2)) , although they span a comparable range in Balmer decrement; (ii) Compton-t hin Seyfert 2s seem to prefer nuclear environments, which are rich in dust on scales of hundreds of parsecs. On the other hand, Compton-thick Seyferts indifferently exhibit 'dust-poor' and 'dust-rich' environments. These resu lts support an extension of the Seyfert unification scenario (as recently p roposed by Matt), where Compton-thick Seyfert 2s are observed through compa ct 'tori', whereas Compton-thin ones are obscured by dust on much larger sc ales.