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dc.contributor.authorHarwood, Jeremy J.
dc.contributor.authorHardcastle, M.J.
dc.contributor.authorCroston, J. H.
dc.date.accessioned2016-03-16T10:14:46Z
dc.date.available2016-03-16T10:14:46Z
dc.date.issued2015-12-21
dc.identifier.citationHarwood , J J , Hardcastle , M J & Croston , J H 2015 , ' Spectral ageing in the lobes of cluster-centre FR II radio galaxies ' , Monthly Notices of the Royal Astronomical Society , vol. 454 , no. 4 , pp. 3403-3422 . https://doi.org/10.1093/mnras/stv2194
dc.identifier.issn0035-8711
dc.identifier.otherPURE: 9718271
dc.identifier.otherPURE UUID: 65df409a-5391-46c8-9a1a-a0197ff8d7bd
dc.identifier.otherScopus: 84949238971
dc.identifier.otherORCID: /0000-0003-0251-6126/work/62748359
dc.identifier.urihttp://hdl.handle.net/2299/16796
dc.description.abstractRecent investigations have shown that many parameters and assumptions made in the application of spectral-ageing models to FR II radio galaxies (e.g. injection index, uniform magnetic field, non-negligible cross-lobe age variations) may not be as reliable as previously thought. In this paper we use new Very Large Array observations, which allow spectral curvature at GHz frequencies to be determined in much greater detail than has previously been possible, to investigate two cluster-centre radio galaxies, 3C 438 and 3C 28. We find that for both sources the injection index is much steeper than the values traditionally assumed, consistent with our previous findings. We suggest that the Tribble model of spectral ageing provides the most convincing description when both goodness-of-fit and physically plausibility are considered, but show that even with greatly improved coverage at GHz frequencies, a disparity exists in cluster-centre FR IIs when spectral ages are compared to those determined from a dynamical viewpoint.We find for 3C 438 that although the observations indicate the lobes are expanding, its energetics suggest that the radiating particles and magnetic field at equipartition cannot provide the necessary pressure to support the lobes, similar to other cluster-centre source such as Cygnus A.We confirm that small-scale, cross-lobe age variations are likely to be common in FR II sources and should be properly accounted for when undertaking spectral-ageing studies. Contrary to the assumption of some previous studies, we also show that 3C 28 is an FR II (rather than FR I) source, and suggest that it is most likely a relic system with the central engine being turned off between 6 and 9 Myr ago.en
dc.format.extent20
dc.language.isoeng
dc.relation.ispartofMonthly Notices of the Royal Astronomical Society
dc.rightsOpen
dc.subjectAcceleration of particles
dc.subjectGalaxies: active
dc.subjectGalaxies: jets
dc.subjectMethods: data analysis
dc.subjectRadiation mechanisms: non-thermal
dc.subjectRadio continuum: galaxies
dc.subjectSpace and Planetary Science
dc.subjectAstronomy and Astrophysics
dc.titleSpectral ageing in the lobes of cluster-centre FR II radio galaxiesen
dc.contributor.institutionSchool of Physics, Astronomy and Mathematics
dc.contributor.institutionScience & Technology Research Institute
dc.contributor.institutionCentre for Astrophysics Research
dc.description.statusPeer reviewed
dc.relation.schoolSchool of Physics, Astronomy and Mathematics
dc.description.versiontypeFinal Accepted Version
dcterms.dateAccepted2015-12-21
rioxxterms.versionAM
rioxxterms.versionofrecordhttps://doi.org/10.1093/mnras/stv2194
rioxxterms.typeJournal Article/Review
herts.preservation.rarelyaccessedtrue
herts.rights.accesstypeOpen


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