J/A+A/690/A321ivo://CDS.VizieR/J/A+A/690/A321doi:10.26093/cds/vizier.36900321CDSKrezinger M.Baldini G.Giroletti M.Sbarrato T.Ghisellini G.,Giovannini G.An T.Gabanyi K.E.Frey S.2025-02-24T20:02:09Z2024-10-18T10:15:23ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiquasarsradio-sourcesOver the past two decades, our knowledge of the high-redshift (z>5) radio quasars has expanded, thanks to dedicated high-resolution very long baseline interferometry (VLBI) observations. Distant quasars provide unique information about the formation and evolution of the first galaxies and supermassive black holes in the Universe. Powerful relativistic jets are likely to have played an essential role in these processes. However, the sample of VLBI-observed radio quasars is still too small to allow meaningful statistical conclusions. We extend the list of the VLBI observed radio quasars to investigate how the source structure and physical parameters are related to radio loudness. We assembled a sample of ten faint radio quasars located at 5<z<6 with their radio-loudness indices spanning between 0.9-76. We observed the selected targets with the European VLBI Network (EVN) at 1.7GHz. The milliarcsecond-scale resolution of VLBI at this frequency allowed us to probe the compact innermost parts of radio-emitting relativistic jets. In addition to the single-band VLBI observations, we collected single-dish and low-resolution radio interferometric data to investigate the spectral properties and variability of our sources. The detection rate of this high-redshift, low-flux-density sample is 90%, with only one target (J0306+1853) remaining undetected. The other nine sources appear core-dominated and show a single, faint and compact radio core on this angular scale. The derived radio powers are typical of Fanaroff-Riley II radio galaxies and quasars. By extending our sample with other VLBI-detected z>5 sources from the literature, we found that the core brightness temperatures and monochromatic radio powers tend to increase with radio loudness.2024A&A...690A.321Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/690/A321CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/690/A321https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/690/A321http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/690/A321https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/690/A321https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/690/A321http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/690/A321GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/690/A321/table2 (1.7-GHz VLBI image parameters and source positions)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/690/A321/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/690/A321/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/690/A321/table2?GETtext/xml+votable180.050000true94.1015743333-13.635117750.005555555555555556Cone search capability for table J/A+A/690/A321/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/690/A321/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/690/A321/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/690/A321/list?GETtext/xml+votable180.050000true94.10157-13.635120.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/690/A3216/4339 5121 6172 9855 18855 18860 20037 21271 22393https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/690/A321?format=asciiRadiodefaultJ/A+A/690/A321/table21.7-GHz VLBI image parameters and source positionsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000VLBI right ascension (J2000)pos.eq.ra;meta.maine_DEJ2000rms uncertainty on declinationarcsecstat.error;pos.eq.decfloatIPeakImage peak intensity at 1.7-GHzmJyphot.flux.density;em.radio.1500-3000MHzfloate_IPeakImage peak intensity 1.7-GHz uncertaintymJystat.errorfloatMajRestoring beam major axismasphys.angSizefloatMinRestoring beam minor axismasphys.angSize;srcfloatPARestoring beam position angle, measured from north through eastdegpos.posAng;instr.beamfloatNoise1{sigma} noise levelmJy/beaminstr.det.noisefloatNameSource name (JHHMM+DDMM)meta.id;meta.mainchare_RAJ2000rms uncertainty on right ascensionsstat.error;pos.eq.radoubleDEJ2000VLBI declination (J2000)pos.eq.dec;meta.mainJ/A+A/690/A321/listList of fits imagesrecnoRecord 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;obsnullableFreq[1.65849] Observed frequencyGHzem.freqdoublesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitscharAssocDataAssociated Data web pagemeta.ref.urlchar