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A relativistic mixing-layer model for jets in low-luminosity radio galaxies

A relativistic mixing-layer model for jets in low-luminosity radio galaxies
A relativistic mixing-layer model for jets in low-luminosity radio galaxies
We present an analytical model for jets in Fanaroff & Riley Class I (FR I) radio galaxies, in which an initially laminar, relativistic flow is surrounded by a shear layer. We apply the appropriate conservation laws to constrain the jet parameters, starting the model where the radio emission is observed to brighten abruptly. We assume that the laminar flow fills the jet there and that pressure balance with the surroundings is maintained from that point outwards.

Entrainment continuously injects new material into the jet and forms a shear layer, which contains material from both the environment and the laminar core. The shear layer expands rapidly with distance until finally the core disappears, and all of the material is mixed into the shear layer. Beyond this point, the shear layer expands in a cone and decelerates smoothly. We apply our model to the well-observed FR I source 3C 31 and show that there is a self-consistent solution.

We derive the jet power, together with the variations of mass flux and entrainment rate with distance from the nucleus. The predicted variation of bulk velocity with distance in the outer parts of the jets is in good agreement with model fits to Very Large Array observations. Our prediction for the shape of the laminar core can be tested with higher-resolution imaging.
galaxies: active, galaxies: individual: 3C 31, galaxies: ISM, galaxies: jets
0035-8711
1113-1124
Wang, Y.
23c775f0-3cac-44d5-9e16-2098959c493b
Kaiser, C. R.
e1c6ce61-aaff-46f7-9ce9-662432f1e8dc
Laing, R.
f6d6712f-478d-432f-9af2-d9917298dfd3
Alexander, P.
e43546a3-01a5-46fd-9dd7-4d157f5623cd
Pavlovski, G.
6acbdaa4-3c28-4287-864d-77649b93959c
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Wang, Y.
23c775f0-3cac-44d5-9e16-2098959c493b
Kaiser, C. R.
e1c6ce61-aaff-46f7-9ce9-662432f1e8dc
Laing, R.
f6d6712f-478d-432f-9af2-d9917298dfd3
Alexander, P.
e43546a3-01a5-46fd-9dd7-4d157f5623cd
Pavlovski, G.
6acbdaa4-3c28-4287-864d-77649b93959c
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e

Wang, Y., Kaiser, C. R., Laing, R., Alexander, P., Pavlovski, G. and Knigge, C. (2009) A relativistic mixing-layer model for jets in low-luminosity radio galaxies. Monthly Notices of the Royal Astronomical Society, 397 (2), 1113-1124. (doi:10.1111/j.1365-2966.2009.15026.x).

Record type: Article

Abstract

We present an analytical model for jets in Fanaroff & Riley Class I (FR I) radio galaxies, in which an initially laminar, relativistic flow is surrounded by a shear layer. We apply the appropriate conservation laws to constrain the jet parameters, starting the model where the radio emission is observed to brighten abruptly. We assume that the laminar flow fills the jet there and that pressure balance with the surroundings is maintained from that point outwards.

Entrainment continuously injects new material into the jet and forms a shear layer, which contains material from both the environment and the laminar core. The shear layer expands rapidly with distance until finally the core disappears, and all of the material is mixed into the shear layer. Beyond this point, the shear layer expands in a cone and decelerates smoothly. We apply our model to the well-observed FR I source 3C 31 and show that there is a self-consistent solution.

We derive the jet power, together with the variations of mass flux and entrainment rate with distance from the nucleus. The predicted variation of bulk velocity with distance in the outer parts of the jets is in good agreement with model fits to Very Large Array observations. Our prediction for the shape of the laminar core can be tested with higher-resolution imaging.

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More information

Published date: 30 June 2009
Keywords: galaxies: active, galaxies: individual: 3C 31, galaxies: ISM, galaxies: jets

Identifiers

Local EPrints ID: 144169
URI: http://eprints.soton.ac.uk/id/eprint/144169
ISSN: 0035-8711
PURE UUID: 0f46d3f5-42d7-453e-bc32-50ae6634068a

Catalogue record

Date deposited: 19 Apr 2010 09:33
Last modified: 08 Nov 2021 18:10

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Contributors

Author: Y. Wang
Author: C. R. Kaiser
Author: R. Laing
Author: P. Alexander
Author: G. Pavlovski
Author: C. Knigge

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