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Towards a Unified Model of Active Galactic Nuclei

Published online by Cambridge University Press:  25 April 2016

C.S. Coleman  and
M.A. Dopita
C.S. Coleman
Affiliation:
DSTO, Guided Weapons Division, PO Box 1500, Salisbury, SA 5108
M.A. Dopita
Affiliation:
Mount Stromlo and Siding Spring Observatories, Private Bag, Weston, ACT 2611
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Abstract

Active Galactic Nuclei (AGN) occur with widely differing characteristics of luminosity, variability and non-thermal emission. Although it is generally accepted that all such objects are powered by the accretion of matter to a super-massive black hole, no convincing model has been proposed which accounts for the diversity of observed phenomena. The model described here is based upon the hypothesis that shear flows in a misaligned accretion disc around a Kerr black hole lead to the growth of dynamical instabilities which disrupt the disc near the Bardeen-Petterson radius. Resulting clouds of disc material are fragmented by collisions and ablated by radiation from the compact core to produce a hot Parker wind which is optically thick to electron scattering. Within this wind, many fragments of disc material are entrained and photoionised to produce the broad emission lines, while some are accreted to power the system. Usually the wind impedes jet flows, in which case the object is radio quiet. When the disc and black hole are only slightly misaligned, however, the wind is equatorially biased and collimated axial jets may form. Such objects will be radio loud, and may exhibit superluminal phenomena if the jet is oriented close to the line of sight.

Type
Extragalactic
Information
Publications of the Astronomical Society of Australia , Volume 10 , Issue 2 , 1992 , pp. 107 - 109
Copyright
Copyright © Astronomical Society of Australia 1992

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