Unification Model of Seyfert Galaxies: Are All Seyfert 2 Galaxies Created Equal?

Abstract

Based on the analysis of a large spectropolarimetric survey of Seyfert 2 galaxies (S2s) from the CfA and 12-micron samples conducted mostly at Lick and Palomar Observatories, it is shown that S2s with hidden BLR (HBLRs) are intrinsically more powerful than non-HBLR S2s. The positive detection of BLR in HBLR S2s appears to be due largely to the intrinsic strength of the hidden AGN nucleus rather than the lower level of nuclear obscuration or reduced dominance of circumnuclear starburst. The HBLR S2s, on average, share many similar large-scale characteristics with Seyfert 1 galaxies (S1s), as would be expected if the unified model is correct, while the non-HBLR S2s generally do not. These results strongly suggest that not all S2s are intrinsically similar in nature, and the HBLR S2s may be the only true counterparts to normal S1s.