J/ApJ/873/132ivo://CDS.VizieR/J/ApJ/873/132doi:10.26093/cds/vizier.18730132CDSMakarov V.V.Berghea C.T.Frouard J.Fey A.Schmitt H.R.2021-04-27T11:41:46Z2020-09-08T10:30:07ZCDS support team

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

cds-question@unistra.frradio-sourcesastrometryphotometryvisible-astronomyredshiftedquasarsWe investigate a sample of 3413 International Celestial Reference Frame (ICRF3) extragalactic radio-loud sources with accurate positions determined by very long baseline interferometry in the S/X band, mostly active galactic nuclei and quasars, which are cross-matched with optical sources in the second Gaia data release (Gaia DR2). The main goal of this study is to determine a core sample of astrometric objects that define the mutual orientation of the two fundamental reference frames, the Gaia (optical) and the ICRF3 (radio) frames. The distribution of normalized offsets between the VLBI sources and their optical counterparts is non-Rayleigh, with a deficit around the modal value and a tail extending beyond the 3{sigma} confidence level. A few filters are applied to the sample in order to discard double cross-matches, confusion sources, and Gaia astrometric solutions of doubtful quality. Panoramic Survey Telescope and Rapid Response System and Dark Energy Survey stacked multicolor images are used to further deselect objects that are less suitable for precision astrometry, such as extended galaxies, double and multiple sources, and obvious misidentifications. After this cleaning, 2643 quasars remain, of which 20% still have normalized offset magnitudes exceeding 3, or a 99% confidence level. We publish a list of 2119 radio-loud quasars of prime astrometric quality. The observed dependence of binned median offset on redshift shows the expected decline at small redshifts, but also an unexpected rise at z~1.6, which may be attributed to the emergence of the CIV emission line in the Gaia's G band. The Gaia DR2 parallax zero-point is found to be color-dependent, suggesting an uncorrected instrumental calibration effect.2019ApJ...873..132Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/873/132CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)I/313 : LQRF: Large Quasar Reference Frame (Andrei+, 2009)I/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)I/345 : Gaia DR2 (Gaia Collaboration, 2018)J/MNRAS/263/425 : Low-z BQS Quasars (Miller+, 1993)J/A+A/506/1477 : Radio source distribution (Titov+, 2009)J/AJ/139/1713 : Celestial Reference Frame at 24 & 43GHz. II (Charlot+, 2010)J/A+A/525/A37 : Variability of QSOs in SDSS Stripe 82 (Meusinger+, 2011)J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)J/AJ/150/58 : VLBI ICRF2 (Fey+, 2015)J/ApJS/221/12 : AGNs in the MIR using AllWISE data (Secrest+, 2015)J/ApJS/224/19 : The KepVIM catalog (Makarov+, 2016)J/ApJ/835/L30 : Dislodged AGNs (Makarov+, 2017)J/MNRAS/467/L71 : Significance of VLBI/Gaia position offsets (Petrov+, 2017)J/A+A/614/A140 : Large Quasar Astrometric Catalog 4, LQAC-4 (Gattano+, 2018)http://hpiers.obspm.fr/webiers/newwww/icrf/ : IERS ICRS Center home pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/873/132https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/873/132http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/873/132https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/873/132https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/873/132http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/873/132GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/873/132/table1 (Best quality radio-optical reference frame objects)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/873/132/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/873/132/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/873/132/table1?GETtext/xml+votable180.050000true328.46232963943.3818057530.0055555555555555565/1624 6/48 49 110 124 128 139 171 175 180 195 226 247 250 376 438 459 461 465 483 514 546 548 569 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45614 45621 45648 45690 45702 45770 45795 45811 45843 45923 46055 46204 46214 46251 46265 46310 46331 46342 46354 46373 46394 46419 46439 46448 46529 46542 46546 46588 46717 46798 46810 46831 46851 46867 46868 46893 46921 46939 46948 46963 46965 46966 47014 47016 47050 47080 47095 47112 47151 47154 47255 47277 47327 47354 47408 47413 47453 47540 47649 47672 47675 47805 47912 47922 47943 47971 48048 48063 48120 48142 48187 48207 48228 48300 48306 48315 48320 48341 48345 48352 48362 48388 48398 48407 48420 48421 48434 48460 48476 48483 48491 48513 48533 48538 48542 48582 48595 48605 48648 48652 48660 48685 48708 48715 48716 48732 48757 48767 48789 48792 48797 48798 48805 48816 48846 48918 48952 48985 49014 49029 49037 49069 49071 49084 49097 491271.9867573869263685e-19 4.621782916333392e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/873/132?format=asciiOpticalRadiodefaultJ/ApJ/873/132/table1Best quality radio-optical reference frame objectsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIERSIERS designation (HHMM+DDd; B1950)meta.id;meta.maincharRAICRSICRF3 right ascensiondegpos.eq.ra;meta.mainDEICRS[-85.6/88.2] ICRF3 declinationdegpos.eq.dec;meta.mainGaiaGaia DR2 unique source identifiermeta.id.crossPlx[-7.858/4.369]? Gaia DR2 parallaxmaspos.parallaxfloatnullablee_Plx[0.019/2.617]? Uncertainty in Gaia parallaxmasstat.error;pos.parallaxfloatnullableGmag[13.26/21.2] Gaia DR2 G magnitudemagphot.mag;em.optfloatBPmag[13.59/21.8]? Gaia DR2 BP magnitudemagphot.mag;em.opt.BfloatnullableRPmag[12.6/20.9]? Gaia DR2 RP magnitudemagphot.mag;em.opt.Rfloatnullablez[0.018/4.72]? Redshift (1)src.redshiftfloatnullabled1[-32.4/19.5] Gaia-ICRF3 difference in RA (times cos(DE))maspos.eq.ra;arith.difffloatd2[-11.8/27.6] Gaia-ICRF3 difference in DECmaspos.eq.dec;arith.difffloatu[0.026/3] Normalized position difference (2)pos;arith.difffloatICRF2Display data from the ICRF2 (I/323) and VLBI ICRF2 (Fey+, 2015, J/AJ/150/58)meta.ref.urlintnullableOCARSDisplay data from Titov+, 2009, J/A+A/506/1477meta.ref.urlintnullableSimbadSimbad column added by the CDSmeta.ref.urlchar