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The Structure of Accretion Flow at the Base of Jets in AGN

Published online by Cambridge University Press:  05 March 2013

Alina-C. Donea  and
Peter L. Biermann
Alina-C. Donea*
Affiliation:
Department of Physics and Mathematical Physics, University of Adelaide, SA 5001, Australia; [email protected]
Peter L. Biermann
Affiliation:
Max Planck Institute for Radioastronomy, Auf dem Hügel 69, 53121 Bonn, Germany; [email protected]
*
*On temporary leave from the Astronomical Institute of the Romanian Academy, Cutitul de Argint, 5, RO-75212, Bucharest.
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Abstract

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This paper discusses the boundary layer and the emission spectrum from an accretion disk having a jet anchored at its inner radius, close to the black hole. We summarise our earlier work and apply it to the accretion disks of some blazars. We suggest that the ‘accretion disk with jet’ (ADJ) model could make the bridge between standard accretion disk models (suitable for quasars and FRii sources) and low-power advection dominated accretion disk models (suitable for some of the low-power BL Lacs and FRi sources).

The jet is collimated within a very narrow region close to the black hole (nozzle). In our model it is assumed that the boundary layer of the disk is the region between radius Rms — the last marginally stable circular orbit calculated for a Kerr geometry — and the radius Rjet, which gives the thickness of the ‘footring’, i.e. the base of the jet. We analyse the size of the boundary layer of the disk where the jet is fed with energy, mass, and angular momentum. As a consequence of the angular momentum extraction, the accretion disk beyond Rjet no longer has a Keplerian flow. A hot corona usually surrounds the disk, and entrainment of the corona along the flow could also be important for the energy and mass budget of the jet.

We assume that the gravitational energy available at the footring of the jet goes into the jet, and so the spectrum from the accretion disk gives a total luminosity smaller than that of a ‘standard’ accretion disk, and our ADJ model should apply for blazars with low central luminosities. Variations of the boundary layer and nozzle may account for some of the variability observed in active galactic nuclei.

Keywords

accretion, accretion disksgalaxies: jetsgalaxies: activegalaxies: nuclei
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 19 , Issue 1 , 2002 , pp. 125 - 128
Copyright
Copyright © Astronomical Society of Australia 2002

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