J/A+A/663/A44ivo://CDS.VizieR/J/A+A/663/A44doi:10.26093/cds/vizier.36630044CDSKappes A.Burd P.R.Kadler M.Ghisellini G.Bonnassieux E.Perucho M.,Brueggen M.Cheung C.C.Ciardi B.Gallo E.Haardt F.Morabito L.K.,Sbarrato T.Drabent A.Harwood J.Jackson N.Moldon J.2022-09-06T09:53:10Z2022-07-13T14:00:14ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frquasarsradio-sourcesStudies of the most distant active galactic nuclei (AGNs) allow us to test our current understanding of the physics present in radio-jetted AGNs across a range of environments, and probe their interactions with these environments. The decrease in apparent luminosity with distance is the primary difficulty to overcome in the study of these distant AGNs, which requires highly sensitive instruments. Our goal is to employ new long wavelength radio data to better parametrise the broad-band spectral energy distribution (SED) of GB 1508+5714, a high-redshift (z=4.30) AGN. Its high redshift, high intrinsic luminosity and classification as a blazar allow us to test emission models that consider the efficient cooling of jet electrons via inverse Compton losses in interactions with the dense cosmic microwave background (CMB) photon field at high redshifts. A significant detection of this effect in GB 1508+5714 may partly explain the apparent sparsity of high-redshift radio galaxies in wide-field surveys, detections of this kind are only becoming possible with the current generation of Square Kilometre Array (SKA) precursors. We used the LOw-Frequency ARray (LOFAR) to image the long wavelength radio emission around the high-redshift blazar GB 1508+5714 on arcsecond scales at frequencies between 128MHz and 160MHz. This allowed us to compare the spatially resolved structure with higher frequency observations, and construct spectral index maps to study the spectral properties of the different components. The LOFAR image shows a compact unresolved core and two resolved emission regions around 2 arcsec to the east and to the west of the radio core. We find structure consistent with previous Very Large Array (VLA) observations, as well as a previously unreported emission region to the east. The region in the west shows a spectral index of -1.2(+0.4,-0.2) while the region in the east indicates a spectral index of <~-1.1. The radio core features a flat spectral index of 0.02+/-0.01. We interpret the arcsecond-scale radio structure of GB 1508+5714 as a FR II-like radio galaxy at a small viewing angle, and the western component as the region containing the approaching jet's terminal hot spot while the eastern diffuse component near the core can be interpreted as the counter-hot spot region. Our SED modelling shows that a scenario featuring significant quenching effects caused by interaction with the CMB provides a good description of the data, and notably explains the suppressed radio emission.2022A&A...663A..44Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/663/A44CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/663/A44https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/663/A44http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/663/A44https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/663/A44https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/663/A44http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/663/A44GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/663/A44/list (Information on fits image)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/663/A44/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/663/A44/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/663/A44/list?GETtext/xml+votable180.050000true227.5121957.045370.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/663/A446/11461https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/663/A44?format=asciiRadiodefaultJ/A+A/663/A44/listInformation on fits imagerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullableFreqObserved frequencyMHzem.freqfloatsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar