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An XMM–Newton study of the environments, particle content and impact of low-power radio galaxies

An XMM–Newton study of the environments, particle content and impact of low-power radio galaxies
An XMM–Newton study of the environments, particle content and impact of low-power radio galaxies
We present a detailed study of the environments of a sample of nine low-power [Fanaroff–Riley type I (FR I)] radio galaxies, based on new and archival XMM–Newton observations. We report new detections of group-scale environments around three radio galaxies: 3C 296, NGC 1044 and 3C 76.1. As with previous studies, we find that FR I radio galaxies inhabit group environments ranging over nearly two orders of magnitude in bolometric X-ray luminosity; however, we find no evidence for a tight relationship between large-scale X-ray environment and radio-source properties such as size, radio luminosity and axial ratio. This leads us to conclude that radio-source evolution cannot be determined entirely by the global properties of the hot gas. We confirm earlier work showing that equipartition internal pressures are typically lower than the external pressures acting on the radio lobes, so that additional non-radiating particles must be present. We present the first direct observational evidence that entrainment may provide this missing pressure, in the form of a relationship between radio-source structure and apparent pressure imbalance. Finally, our study provides further support for the presence of an apparent temperature excess in radio-loud groups compared to the group population as a whole. For five of eight temperature excesses, the energy required to inflate the radio lobes is comparable to the energy required to produce this excess by heating of the group gas; however, in three cases the current radio source appears too weak to produce the temperature excess. It remains unclear whether the temperature excess can be directly associated with the current phase of active galactic nuclei (AGN) activity, or whether it is instead either a signature of previous AGN activity or simply an indicator of the particular set of group properties most conducive to the growth of an FR I radio galaxy.
galaxies: active, X-rays: galaxies: clusters
1365-2966
1709-1728
Croston, J.H.
b10aa3fb-620e-4ec2-93e5-8594748d4822
Hardcastle, M.J.
23b43806-5ee7-46e3-b29b-98f7442dd263
Birkinshaw, M.
f84791f0-587f-42dc-adbd-4568ec9e66c1
Worrall, D.M.
af83a5a9-e50d-4b28-ad03-92baf3726d56
Laing, R.A.
6be9adca-6031-4a04-a98d-f0b22d0ca85c
Croston, J.H.
b10aa3fb-620e-4ec2-93e5-8594748d4822
Hardcastle, M.J.
23b43806-5ee7-46e3-b29b-98f7442dd263
Birkinshaw, M.
f84791f0-587f-42dc-adbd-4568ec9e66c1
Worrall, D.M.
af83a5a9-e50d-4b28-ad03-92baf3726d56
Laing, R.A.
6be9adca-6031-4a04-a98d-f0b22d0ca85c

Croston, J.H., Hardcastle, M.J., Birkinshaw, M., Worrall, D.M. and Laing, R.A. (2008) An XMM–Newton study of the environments, particle content and impact of low-power radio galaxies. Monthly Notices of the Royal Astronomical Society, 386 (3), 1709-1728. (doi:10.1111/j.1365-2966.2008.13162.x).

Record type: Article

Abstract

We present a detailed study of the environments of a sample of nine low-power [Fanaroff–Riley type I (FR I)] radio galaxies, based on new and archival XMM–Newton observations. We report new detections of group-scale environments around three radio galaxies: 3C 296, NGC 1044 and 3C 76.1. As with previous studies, we find that FR I radio galaxies inhabit group environments ranging over nearly two orders of magnitude in bolometric X-ray luminosity; however, we find no evidence for a tight relationship between large-scale X-ray environment and radio-source properties such as size, radio luminosity and axial ratio. This leads us to conclude that radio-source evolution cannot be determined entirely by the global properties of the hot gas. We confirm earlier work showing that equipartition internal pressures are typically lower than the external pressures acting on the radio lobes, so that additional non-radiating particles must be present. We present the first direct observational evidence that entrainment may provide this missing pressure, in the form of a relationship between radio-source structure and apparent pressure imbalance. Finally, our study provides further support for the presence of an apparent temperature excess in radio-loud groups compared to the group population as a whole. For five of eight temperature excesses, the energy required to inflate the radio lobes is comparable to the energy required to produce this excess by heating of the group gas; however, in three cases the current radio source appears too weak to produce the temperature excess. It remains unclear whether the temperature excess can be directly associated with the current phase of active galactic nuclei (AGN) activity, or whether it is instead either a signature of previous AGN activity or simply an indicator of the particular set of group properties most conducive to the growth of an FR I radio galaxy.

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Published date: 3 May 2008
Keywords: galaxies: active, X-rays: galaxies: clusters

Identifiers

Local EPrints ID: 151979
URI: http://eprints.soton.ac.uk/id/eprint/151979
ISSN: 1365-2966
PURE UUID: 33c6ed52-44b6-40fb-aa90-7f7c44554e1e

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Date deposited: 20 May 2010 13:48
Last modified: 14 Mar 2024 01:21

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Contributors

Author: J.H. Croston
Author: M.J. Hardcastle
Author: M. Birkinshaw
Author: D.M. Worrall
Author: R.A. Laing

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