J/ApJ/728/26ivo://CDS.VizieR/J/ApJ/728/26doi:10.26093/cds/vizier.17280026CDSMacLeod C.L.Brooks K.Ivezic Z.Kochanek C.S.Gibson R.Meisner A.,Kozlowski S.Sesar B.Becker A.C.de Vries W.H.2012-10-27T16:51:53Z2012-10-16T16:02:45ZCDS support team

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

cds-question@unistra.frquasarsvisible-astronomysloan-photometryastronomical-modelsWe develop a method for separating quasars from other variable point sources using Sloan Digital Sky Survey (SDSS) Stripe 82 light-curve data for ~10000 variable objects. To statistically describe quasar variability, we use a damped random walk (DRW) model parametrized by a damping timescale, {tau}, and an asymptotic amplitude (structure function), SF_{infinite}_. With the aid of an SDSS spectroscopically confirmed quasar sample, we demonstrate that variability selection in typical extragalactic fields with low stellar density can deliver complete samples with reasonable purity (or efficiency, E). Compared to a selection method based solely on the slope of the structure function, the inclusion of the {tau} information boosts E from 60% to 75% while maintaining a highly complete sample (98%) even in the absence of color information. For a completeness of C=90%, E is boosted from 80% to 85%. Conversely, C improves from 90% to 97% while maintaining E=80% when imposing a lower limit on {tau}. With the aid of color selection, the purity can be further boosted to 96%, with C=93%. Hence, selection methods based on variability will play an important role in the selection of quasars with data provided by upcoming large sky surveys, such as Pan-STARRS and the Large Synoptic Survey Telescope (LSST). In summary, given an adequate survey cadence, photometric variability provides an even better method than color selection for separating quasars from stars.2011ApJ...728...26Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/728/26CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)J/ApJS/199/3 : The quasars MMT-BOSS pilot survey (Ross+, 2012)J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)J/A+A/525/A37 : Variability of QSOs in SDSS Stripe 82 (Meusinger+, 2011)J/AJ/137/3884 : Quasar candidates selected from the SDSS (Richards+, 2009)J/ApJS/180/67 : Photometric selection of QSOs from SDSS. II. (Richards+, 2009)J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)J/A+A/497/81 : Variability-selected AGN in CDFS (Boutsia+, 2009)J/AJ/133/1780 : GALEX/SDSS quasar catalog (Trammell+, 2007)J/AJ/131/2788 : Redshifts in the SFQS survey (Jiang+, 2006)J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)J/ApJ/633/638 : 315 SDSS variable quasar sample (Wilhite+, 2005)J/AJ/122/503 : SDSS photometry and redshift of QSOs (Anderson+, 2001)J/AJ/121/31 : High-redshift quasars in SDSS (Fan+, 2001)J/ApJS/123/377 : u*g*r*i*z* Photometry of stars, galaxies, QSOs (Newberg+ 1999)http://www.sdss.org/ : SDSS home pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/728/26https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/728/26http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/728/26https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/728/26https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/728/26http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/728/26GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/728/26/table1 (Targets for spectroscopic follow-up)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/728/26/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/728/26/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/728/26/table1?GETtext/xml+votable180.050000true340.000458060.304811110.0055555555555555565/4697 4698 4710 4756 4762 6/2 17405 17406 17407 17725 17726 17741 17742 17743 17745 17747 17749 17750 17753 17754 17757 17761 17763 17765 17766 17767 17771 17772 17773 17776 17778 17806 17812 17814 17816 17817 17818 17820 17821 17826 17832 17834 17835 17837 17838 17840 17842 17857 17997 17998 18002 18003 18006 18007 18008 18009 18011 18018 18020 18024 18025 18027 18029 18032 18062 18063 18068 18070 18075 18076 18078 18081 18083 18084 18089 18092 18094 18112 18113 18685 18747 18749 18750 18771 18772 18775 18776 18777 18782 18787 18797 18798 18800 18829 18831 18833 18834 18835 18836 18839 18844 18845 18846 18850 18851 18853 18854 18855 18856 18859 18860 18861 18862 18864 18865 18880 18882 19007 19028 19031 19033 19035 19036 19037 19038 19042 19043 19045 19046 19047 19052 19054 19056 19057 19058 19093 19095 19137 19138 19200 19202 19456 23201 23207 23212 23213 23218 23224 36861 36862 368632.381800341673347e-19 2.821731604724377e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/728/26?format=asciiOpticaldefaultJ/ApJ/728/26/table1Targets for spectroscopic follow-upSDSSSDSS-DR7 IAU name from Cat. II/294 when <0.50"meta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[46516/7912248] Target identification number (1)meta.idintRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainimag[12.87/18.99] SDSS i band magnitude (2)magphot.mag;em.opt.Ifloatu-gSDSS (u-g) color index (2)magphot.color;em.opt.U;em.opt.Bfloatg-rSDSS (g-r) color index (2)magphot.color;em.opt.B;em.opt.Rfloatr-iSDSS (r-i) color index (2)magphot.color;em.opt.R;em.opt.Ifloati-zSDSS (i-z) color index (2)magphot.color;em.opt.I;em.opt.Ifloatlogtau[2/7.5] Log of the DRW tau time scale (3)log(d)time.scaledoubleSFinf[0.01/44.05] DRW long-term structure functionmagphot.mag;meta.modelleddoubleOut[0/1] Outlier (3)meta.codeintSloanDisplay the SDSS data for this quasarmeta.ref.urlchar