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Seyfert Galaxies

Published online by Cambridge University Press:  14 August 2015

Andrew S. Wilson
Andrew S. Wilson*
Affiliation:
Astronomy Program, University of Maryland

Abstract

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Observations of sample of Markarian Seyferts with the VLA indicate that a large fraction possess linear radio structure on a scale of a few hundred parsecs to a few kiloparsecs. The radio components generally straddle the optical nucleus and several sources are simple doubles. Similar structures are seen in the classical Seyferts NGC 1068, 4151, and 5548. NGC 4151 is probably best interpreted as a jet. A few sources (e.g. Mark 315, NGC 7469) exhibit diffuse, non-aligned radio structure on a scale similar to that of the linear sources. The radio axis in linear sources is misaligned with respect to the rotation axis of the galaxy disc by a large angle. The linear sources are discussed in terms of a model of a supersonic beam or jet which is “disrupted” by interaction with interstellar gas in the inner part of the galaxy (often a spiral). Two aspects of this interaction are emphasised. Firstly, the curved shape of the radio sources in NGC 1068 and NGC 4151 is ascribed to beam bending by the ram pressure of the rotating interstellar medium. Simple models of this process are shown to be consistent with the observations. Secondly, it is suggested that the broadened forbidden lines in Seyferts originate in part from interstellar gas accelerated outwards by the beam. This picture accounts for some of the empirical correlations found between radio and optical forbidden line properties.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 97: Extragalactic Radio Sources , 1982 , pp. 179 - 188
Copyright
Copyright © Reidel 1982 

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