J/ApJ/888/73ivo://CDS.VizieR/J/ApJ/888/73doi:10.26093/cds/vizier.18880073CDSHwang H.-C.Shen Y.Zakamska N.Liu X.2022-09-21T09:29:48Z2021-11-18T09:32:41ZCDS support team

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

cds-question@unistra.frquasarsproper-motionsvisible-astronomytrigonometric-parallaxspectroscopyGaia's precision astrometry allows systematic identification of optically selected subkiloparsec dual active galactic nuclei (AGNs), off-nucleus AGNs, and small-scale lensed quasars by "varstrometry"-where variability-induced astrometric jitter, i.e., temporal displacements of photocenter in unresolved sources, can be reasonably well detected or constrained. This approach extends systematic searches for small-scale (>=mas) dual and off-nucleus AGNs to the poorly explored regime between ~10pc and ~1kpc, with Gaia's full sky coverage and depth to G~21. We outline the general principles of this method and calculate the expected astrometric signals from the full time series of photocenter measurements and light curves. We demonstrate the feasibility of varstrometry by using Gaia DR2 data on a sample of variable pre-main-sequence stars with known close companions. We find that extended host galaxies have a significant impact on the accuracy of astrometric and photometric variability in Gaia DR2, a situation to be improved in future Gaia releases. Using spectroscopically confirmed Sloan Digital Sky Survey quasars, we present several examples of candidate subkiloparsec off-nucleus or dual AGNs selected from Gaia DR2. We discuss the merits and limitations of this method and a follow-up strategy for promising candidates. We highlight Gaia's potential of systematically discovering and characterizing the subkiloparsec off-nucleus and dual AGN population in the entire optical sky.2020ApJ...888...73Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/888/73CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)J/AJ/126/1720 : ugriz and H{alpha} of double-peaked AGN (Strateva+, 2003)J/AJ/129/2542 : BL Lac from SDSS (Collinge+, 2005)J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)J/ApJS/201/23 : Spectroscopy of 88 z<0.7 SDSS QSOs (Eracleous+, 2012)J/ApJ/745/119 : Close companions to young stars. I. ChaI & Tau (Nguyen+, 2012)J/ApJ/789/112 : Offset AGN Candidates (Comerford+, 2014)J/ApJ/789/140 : SDSS quasars balmer emission lines (Liu+, 2014)J/ApJ/799/72 : Binary AGNs from the VLA Stripe 82 survey (Fu+, 2015)J/MNRAS/453/1562 : CRTS close supermassive black hole binaries (Graham+, 2015)J/ApJS/221/12 : AGNs in the MIR using AllWISE data (Secrest+, 2015)J/MNRAS/446/2985 : Double-lobed radio sources catalog (van Velzen+, 2015)J/ApJS/224/19 : The KepVIM catalog (Makarov+, 2016)J/A+A/618/A56 : Gaia GraL. II. Known multiply imaged quasars (Ducourant+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/888/73https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/888/73http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/888/73https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/888/73https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/888/73http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/888/73GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/888/73/table2 (List of genuine quasars that have significant non-zero parallaxes from Gaia DR2)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/888/73/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/888/73/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/888/73/table2?GETtext/xml+votable180.050000true15.5522687648779581.6756615654189240.005555555555555556Cone search capability for table J/ApJ/888/73/table3 (List of genuine quasars that have significant non-zero proper motions from Gaia DR2)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/888/73/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/888/73/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/888/73/table3?GETtext/xml+votable180.050000true8.208901364766461-10.8993572519172820.0055555555555555566/4124 4193 4651 4773 5459 6020 6418 6513 7204 8264 8414 8658 8765 9063 9639 9786 9887 10062 10445 10799 10940 11110 11290 11494 12400 17234 17761 17775 18040 18539 18685 31450 36766https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/888/73?format=asciiOpticaldefaultJ/ApJ/888/73/table2List of genuine quasars that have significant non-zero parallaxes from Gaia DR2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS identifier (HHMMSS.ss+DDMMSS.s; J2000)meta.id;meta.maincharm_SDSS2=SDSS with two Gaia matches within 1"meta.ref.urlintnullableRA_ICRS[15.5/339] Gaia DR2 barycentric right ascension (ICRS) at Ep=2015.5degpos.eq.ra;meta.mainDE_ICRS[-9.5/60.5] Gaia DR2 barycentric declination (ICRS) at Ep=2015.5degpos.eq.dec;meta.mainplx[0.43/13.97]? Parallaxmaspos.parallax.trigdoublenullableErrplx[0.8/9.2]? Parallax divided by the errorstat.errordoublenullableGaiaDisplay the Gaia DR2 (I/345) data within 1"meta.ref.urlcharSloanDisplay the online SDSS-DR16 data for the nearest objectmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharNEDNED column added by the CDSmeta.ref.urlchar_RA.icrsRight ascension (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decnullableindexedJ/ApJ/888/73/table3List of genuine quasars that have significant non-zero proper motions from Gaia DR2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS Identifier (HHMMSS.ss+DDMMSS.s; J2000)meta.id;meta.maincharm_SDSS2=SDSS with two Gaia matches within 1"meta.ref.urlintnullableRA_ICRS[8.2/260.8] Gaia DR2 barycentric right ascension (ICRS) at Ep=2015.5degpos.eq.ra;meta.mainDE_ICRS[-10.9/52.8] Gaia DR2 barycentric declination (ICRS) at Ep=2015.5degpos.eq.dec;meta.mainpm[0.13/43.52]? Total proper motionmas/yrpos.pmdoublenullableErrpm[0.49/47.8]? Total proper motion divided by the errorstat.errordoublenullableGaiaDisplay the Gaia DR2 (I/345) data within 1"meta.ref.urlcharSloanDisplay the online SDSS-DR16 data for the nearest objectmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharNEDNED column added by the CDSmeta.ref.urlchar_RA.icrsRight ascension (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decnullableindexed