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dc.contributor.authorSweijen, Frits
dc.contributor.authorMorabito, Leah K.
dc.contributor.authorHarwood, Jeremy
dc.contributor.authorWeeren, Reinout J. van
dc.contributor.authorRöttgering, Huub J. A.
dc.contributor.authorCallingham, Joseph R.
dc.contributor.authorJackson, Neal
dc.contributor.authorMiley, George
dc.contributor.authorMoldon, Javier
dc.date.accessioned2022-02-28T12:30:01Z
dc.date.available2022-02-28T12:30:01Z
dc.date.issued2022-02-01
dc.identifier.citationSweijen , F , Morabito , L K , Harwood , J , Weeren , R J V , Röttgering , H J A , Callingham , J R , Jackson , N , Miley , G & Moldon , J 2022 , ' High-resolution international LOFAR observations of 4C~43.15 -- Spectral ages and injection indices in a high-z radio galaxy ' , Astronomy & Astrophysics , vol. 658 , A3 . https://doi.org/10.1051/0004-6361/202039871
dc.identifier.issn0004-6361
dc.identifier.otherArXiv: http://arxiv.org/abs/2108.07290v1
dc.identifier.otherORCID: /0000-0003-0251-6126/work/109317433
dc.identifier.urihttp://hdl.handle.net/2299/25400
dc.description© ESO 2021. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1051/0004-6361/202039871
dc.description.abstractIt has long been known that radio sources with the steepest spectra are preferentially associated with the most distant galaxies, the α - z relation, but the reason for this relation is an open question. The spatial distribution of spectra in high-z radio sources can be used to study this relation, and low-frequency observations are particularly important in understanding the particle acceleration and injection mechanisms. However, the small angular sizes of high-z sources together with the inherently low resolution of low-frequency radio telescopes until now has prevented high angular resolution low-frequency observations of distant objects. Here we present subarcsecond observations of a z = 2.4 radio galaxy at frequencies between 121 and 166 MHz. We measure the spatial distribution of spectra, and discuss the implications for models of the α-z relation. We targeted 4C 43.15 with the High Band Antennas of the International LOFAR Telescope with a range of baselines up to 1300 km. At the central frequency of 143 MHz we achieve an angular resolution of ∼0.3″. By complementing our data with archival Very Large Array data we study the spectral index distribution across 4C 43.15 between 55 MHz and 8.4 GHz at resolutions of 0.4″ and 0.9″. With a magnetic field strength of B = 5.2 nT and fitted injection indices of αinjnorth = -0.8 and αinjsouth = -0.6, fitting a Tribble spectral ageing model results in a spectral age of τspec = 1.1 ± 0.1 Myr. We conclude that our data on 4C 43.15 indicates that inverse Compton losses could become comparable to or exceed synchrotron losses at higher redshifts and that inverse Compton losses could be a viable explanation for the α-z relation. Statistical studies of these objects will become possible in the future when wide-area subarcsecond surveys start.en
dc.format.extent13
dc.format.extent1889266
dc.language.isoeng
dc.relation.ispartofAstronomy & Astrophysics
dc.subjectastro-ph.GA
dc.subjectGalaxies: evolution
dc.subjectRadio continuum: galaxies
dc.subjectRadiation mechanisms: non-thermal
dc.subjectGalaxies: active
dc.subjectGalaxies: high-redshift
dc.subjectAstronomy and Astrophysics
dc.subjectSpace and Planetary Science
dc.titleHigh-resolution international LOFAR observations of 4C~43.15 -- Spectral ages and injection indices in a high-z radio galaxyen
dc.contributor.institutionCentre for Astrophysics Research
dc.contributor.institutionSchool of Physics, Engineering & Computer Science
dc.contributor.institutionDepartment of Physics, Astronomy and Mathematics
dc.description.statusPeer reviewed
dc.identifier.urlhttp://www.scopus.com/inward/record.url?scp=85124073951&partnerID=8YFLogxK
rioxxterms.versionofrecord10.1051/0004-6361/202039871
rioxxterms.typeJournal Article/Review
herts.preservation.rarelyaccessedtrue


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