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Non-constant Superluminal Velocities in AGN

Published online by Cambridge University Press:  25 April 2016

Colin S. Coleman
Colin S. Coleman*
Affiliation:
Department of Mathematics, Monash University, Clayton, Vic 3168
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Abstract

Large apparent superluminal velocities are observed in nuclear jets in Active Galaxies, indicating the presence of relativistic velocities almost along the line of sight. If the flow is well collimated, as suggested by the large scale radio structure, the inferred alignment leads to difficulties with source statistics. Here a modification of the usual relativistic beam model is proposed, in which the jet is assumed to contain azimuthal (swirling) flow. Perturbation analysis is used to show that the jet is unstable to a Kelvin-Helmholtz helical standing wave, the wavelength of which increases without bound in the limit of vanishing swirl. This instability may cause a cylindrical jet to follow a helical path in space, thereby reducing the implied alignment of a superluminal source, and providing a natural interpretation of non-constant superluminal velocities.

Type
Extragalactic
Information
Publications of the Astronomical Society of Australia , Volume 8 , Issue 4 , 1990 , pp. 353 - 356
Copyright
Copyright © Astronomical Society of Australia 1990

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