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

Abstract

We present a detailed study of the environments of a sample of nine low-power 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, but 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. 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 or the lobes must be magnetically dominated. 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 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.

21 pages, 13 figures. Accepted for publication in MNRAS. Version with higher resolution figures available from http://hercules.herts.ac.uk/~jcroston/xmmfris.pdf

References in corpus (6)

• Heating Hot Atmospheres with Active Galactic Nuclei
• The Representative XMM-Newton Cluster Structure Survey (REXCESS) of an X-ray Luminosity Selected Galaxy Cluster Sample
• The X-ray nuclei of intermediate-redshift radio sources
• The inner jet of radio galaxy NGC 315 as observed with Chandra and the VLA
• Multifrequency VLA observations of the FR I radio galaxy 3C 31: morphology, spectrum and magnetic field
• Using Radio Bubbles to Constrain the Matter Content of AGN Jets

Cited by in corpus (6)

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• Structures of the magnetoionic media around the FR I radio galaxies 3C 31 and Hydra A
• Markarian 6: shocking the environment of an intermediate Seyfert
• Chandra evidence for AGN feedback in the spiral galaxy NGC 6764
• Evolution of X-ray cavities
• Shock heating in the group atmosphere of the radio galaxy B2 0838+32A