Seyfert 2 Galaxies: Unification and the X-ray Background

An important but unresolved question regarding unification models of Seyfert galaxies is whether all---or just some---type 2 Seyferts are obscured Seyfert 1s. The answer is relevant not only for an improvement of our classification scheme, but also for establishing whether heavily obscured AGNs are capable of producing the majority of the cosmic X-ray background radiation. Thus, we have recently completed a joint optical spectropolarimetric and broadband X-ray survey of a distance-limited sample of 30 nearby classical type 2 Seyfert galaxies, in order to investigate the frequency of obscured broad-line regions in such objects and their collective properties in the hard X-ray band. Our results indicate that at least 11 (35%) of the objects in our sample have polarized broad emission lines, and that the majority of the galaxies are detected in the 1--10 keV range by ASCA. We combine these data with existing radio and far-infrared observations to explore differences in the radio luminosities, infrared colors, hard X-ray detection statistics, and composite X-ray spectra of Seyfert 2s with and without evidence for polarized broad emission lines. We also present an unbiased, luminosity-weighted composite X-ray spectrum for the full sample, which we compare to the spectrum of the X-ray background measured by ASCA. L.E.K. acknowledges support from NSF CAREER grant AST-9501835. E.C.M. is supported by a NASA Chandra Fellowship.