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AGN jet kinetic power and the energy budget of radio galaxy lobes
journal contribution
posted on 2023-05-17, 17:13 authored by Godfrey, LEH, Stanislav ShabalaStanislav ShabalaRecent results based on the analysis of radio galaxies and their hot X-ray emitting atmospheres suggest that non-radiating particles dominate the energy budget in the lobes of FR I radio galaxies, in some cases by a factor of more than 1000, while radiating particles dominate the energy budget in FR II radio galaxy lobes. This implies a significant difference in the radiative efficiency of the two morphological classes. To test this hypothesis, we have measured the kinetic energy flux for a sample of 3C FR II radio sources using a new method based on the observed parameters of the jet terminal hotspots, and compared the resulting Qjet-Lradio relation to that obtained for FR I radio galaxies based on X-ray cavity measurements. Contrary to expectations, we find approximate agreement between the Qjet-Lradio relations determined separately for FR I and FR II radio galaxies. This result is ostensibly difficult to reconcile with the emerging scenario in which the lobes of FR I and FR II radio galaxies have vastly different energy budgets. However, a combination of lower density environment, spectral aging and strong shocks driven by powerful FR II radio galaxies may reduce the radiative efficiency of these objects relative to FR Is and counteract, to some extent, the higher radiative efficiency expected to arise due to the lower fraction of energy in non-radiating particles. An unexpected corollary is that extrapolating the Qjet-Lradio relation determined for low power FR I radio galaxies provides a reasonable approximation for high power sources, despite their apparently different lobe compositions.
History
Publication title
The Astrophysical Journal: An International Review of Astronomy and Astronomical PhysicsVolume
767Article number
12Number
12Pagination
1-9ISSN
0004-637XDepartment/School
School of Natural SciencesPublisher
IOP SciencePlace of publication
1427 E 60Th St, Chicago, USA, Il, 60637-2954Rights statement
Copyright 2013 The American Astronomical SocietyRepository Status
- Restricted