J/AJ/127/3609ivo://CDS.VizieR/J/AJ/127/3609doi:10.26093/cds/vizier.51273609CDSOjha R.Fey A.L.Johnston K.J.Jauncey D.L.Reynolds J.E.,Tzioumis A.K.Quick J.F.H.Nicolson G.D.Ellingsen S.P.Dodson R.G.,Mcculloch P.M.2023-04-06T16:51:05Z2007-03-29T21:08:59ZCDS support team

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

cds-question@unistra.frradio-sourcesquasarsgalaxy-classification-systemsredshiftedWe present 8.4GHz very long baseline interferometry (VLBI) observations of 69 southern hemisphere extragalactic sources in the International Celestial Reference Frame. These are the first in a series of observations intended to image all such sources at milliarcsecond resolution in order to determine their continued suitability for reference-frame use based on intrinsic structure. We use the resultant images to calculate a core fraction, that is, the ratio of core flux density to total flux density, for all observed sources. The resulting distribution, with a mean value of 0.83, suggests that most sources are relatively compact. However, just over half the observed sources show significant extended emission in the form of multiple compact components. These sources are probably poorly suited for high-accuracy reference-frame use unless intrinsic structure and potential variability can be taken into account. Our observations represent the first large, comprehensive VLBI imaging survey in the southern hemisphere, significantly extending the existing limited VLBI surveys and, along with some well-known objects, containing many sources that have never been imaged at milliarcsecond resolution. The overlap with Very Long Baseline Array images of sources between 0{deg} and -35{deg} declination helps determine the limits to imaging with the southern hemisphere-accessible telescopes.2004AJ....127.3609Ohttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/127/3609CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/127/3609https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/127/3609http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/127/3609https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/127/3609https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/127/3609http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/127/3609GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/127/3609/objects (Objects position (from Simbad))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/127/3609/objects?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/127/3609/objects?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/127/3609/objects?GETtext/xml+votable180.050000true2.755-26.2091670.0055555555555555566/16592 16962 17414 17529 18438 20503 20657 21012 21049 24809 25256 26244 26769 28798 29016 29218 32916 32948 33010 33560 33827 33829 34013 34264 34461 34675 34931 35079 35651 35786 35801 36155 36941 37385 37480 37819 38128 38418 39672 39695 39733 40344 40479 40527 41088 41310 42060 42853 42901 43257 43366 43399 43936 44147 44247 45393 45409 45446 45763 46040 46055 46588 47014 47106-47107 47540 48123 48228 48362https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/127/3609?format=asciiOpticalRadiodefaultJ/AJ/127/3609/objectsObjects position (from Simbad)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPKSPKS source name (based on B1950 position)meta.id;meta.maincharprimaryRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Simbad declination (J2000)pos.eq.dec;meta.mainSimbadSimbad column added by the CDScharNEDSimbad column added by the CDScharJ/AJ/127/3609/table2Parameters of Naturally Weighted ImagesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPKSPKS source namemeta.id;meta.maincharObs[de] Epoch of observation (1)time.epochcharaaxisRestoring beam FWHM of the major axismasphys.angSize;instr.beamfloatbaxisRestoring beam FWHM of the minor axismasphys.angSize;instr.beamfloatPA[-90/90] Restoring beam position angle (2)degpos.posAng;instr.beamintSp8.4GHzPeak flux at 8.4GHz in units of Jy/beamJyphot.flux.density;em.radio.6-12GHzfloatRMSRoot-mean-square of final hybrid image residuals in units of mJy/beammJystat.errorfloatLevelContour levels in units of mJy/beam (3)mJystat.fit.paramJ/AJ/127/3609/table3Physical Characteristics of SourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPKSPKS source namemeta.id;meta.maincharID[QGLA] Optical identification (1)meta.codecharl_zLimit flag on zmeta.code.error;src.redshiftcharz? Redshiftsrc.redshiftfloatnullableVmag? Visual magnitudemagphot.mag;em.opt.VfloatnullableJ/AJ/127/3609/table4Gaussian ModelsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPKSPKS source namemeta.id;meta.maincharObs[bc] Epoch of observation (1)time.epochcharComp[1/3] Component numbermeta.code.multipintS8.4GHzFlux density at 8.4GHzJyphot.flux.density;em.radio.6-12GHzfloatSepComponent separation from arbitrary originmaspos.angDistancefloatPA1[-180/180]? Position angle between component and origin (2)degmeta.ref;pos.posAngintnullableaaxisFWHM of the major axismasphys.angSizefloatb/aMajor to minor axis ratiophys.angSize;arith.ratiofloatPA2[-90/90]? Major axis position angle (2)degpos.posAngintnullable