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Date and Time of the Query: 2019-08-20 T22:48:14 PDT
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For refcode 2003ApJ...583..632T:
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2003ApJ...583..632T The Unified Model and Evolution of Active Galaxies: Implications from a Spectropolarimetric Study Hien D. Tran Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218; tran@pha.jhu.edu Received 2002 August 14; accepted 2002 October 9 ABSTRACT We extend the analysis presented in Paper I of a spectropolarimetric survey of the CfA and 12 microns samples of Seyfert 2 galaxies (S2s). We confirm that polarized (hidden) broad-line region (HBLR) S2s tend to have hotter circumnuclear dust temperatures, show mid-IR spectra more characteristic of Seyfert 1 galaxies (S1s), and are intrinsically more luminous than non-HBLR S2s. The levels of obscuration and circumnuclear star formation, however, appear to be similar between HBLR and non-HBLR S2 galaxies, based on an examination of various observational indicators. HBLR S2s, on average, share many similar large-scale, presumably isotropic, characteristics with S1s, as would be expected if the unified model is correct, while non-HBLR S2s generally do not. The active nuclear engines of non-HBLR S2s, then, appear to be truly weaker than HBLR S2s, which in turn are fully consistent with being S1s viewed from another direction. There is also evidence that the fraction of detected HBLRs increases with the radio power of the active galactic nucleus. Thus, all S2 galaxies may not be intrinsically similar in nature, and we speculate that evolutionary processes may be at work. Subject headings: galaxies: active - galaxies: Seyfert - polarization
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