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Paper: Neutral Hydrogen in Seyfert Galaxies --- A Test for the Unification Scheme
Volume: 240, Gas and Galaxy Evolution: A Conference in Honor of the 20th Anniversary of the VLA
Page: 414
Authors: Ghosh, T.; Eder, J.; Salter, C. J.; Frierson, D. M.
Abstract: We present an unbiased survey of HI in Seyfert galaxies to test theories designed to unify the Seyfert 1 (broad-emission line) and Seyfert 2 (narrow-line) classes of active galaxies. If the Unification Scheme is strictly applicable to all Seyfert galaxies, and if the galaxy's HI disk is aligned with the accretion disk, then Sy 1 HI spectra should have the narrower velocity widths, while total derived HI masses and surface densities should be comparable for the two classes. The Arecibo telescope was used to observe a sample of 61 Seyfert galaxies with redshifts <= 0.044 which were previously unobserved or undetected at λ21 cm. HI was detected in 39 galaxies (64%), of which 20 are Sy 1 and 19 Sy 2. The distributions of HI mass and surface density were found to be similar for the two classes, consistent with orientation independence. However, the distributions of the velocity widths were not significantly different either, which could indicate random alignment of the HI and accretion disks. Further, the ratio of the continuum flux density (orientation dependent for core-jet emission) and the HI mass (orientation independent) did not display significant differences between the two classes, contrary to expectations based on the Unified Scheme.
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