J/AJ/154/269ivo://CDS.VizieR/J/AJ/154/269doi:10.26093/cds/vizier.51540269CDSYang Q.Wu X.-B.Fan X.Jiang L.McGreer I.Green R.Yang J.,Schindler J.-T.Wang F.Zuo W.Fu Y.2018-10-23T07:45:29Z2018-09-18T11:41:21ZCDS support team

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

cds-question@unistra.frquasarsinfrared-photometryvisible-astronomybroad-band-photometryredshiftedastronomical-modelsWe present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multidimensional space of relative fluxes as a function of redshift and magnitude. For 151392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z z_p_ and the spectroscopic redshift z_s_, |{Delta}_z_|=|z_s_-z_p_|/(1+z_s_) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars, and galaxies are calculated, respectively, based on (1) the quasar luminosity function, (2) the Milky Way synthetic simulation with the Besancon model, and (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5<z<4.5, and a wide magnitude range 18<r<21.5 mag. Our photo-z regression and classification method has the potential to extend to future surveys. The photo-z code will be publicly available.2017AJ....154..269Yhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/154/269CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)VII/279 : SDSS quasar catalog: twelfth data release (Paris+, 2017)J/AJ/134/973 : SDSS Stripe 82 star catalogs (Ivezic+, 2007)J/ApJ/768/105 : z~5 QSO luminosity function from SDSS Stripe 82J/MNRAS/440/476 : Low-redshift quasars in SDSS Stripe 82 (Falomo+, 2014)J/MNRAS/441/1802 : Low-redshift QSOs in SDSS Stripe 82 (Karhunen+, 2014)J/A+A/611/A97 : Photometric quasar candidates in Stripe 82https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/154/269https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/154/269http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/154/269https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/154/269https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/154/269http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/154/269GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/154/269/table4 (Photometric quasar in S82)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/154/269/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/154/269/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/154/269/table4?GETtext/xml+votable180.050000true0.00193188-0.229279380.0055555555555555564/1109 1110 1129 1130 1177 5/4351 4431 4435 4444 4451 4452 4453 4454 4456 4457 4458 4460 4464 4495 4501 4502 4503 4504 4505 4506 4508 4524 4528 4544 4687 4691 4692 4693 4694 4696 4697 4698 4713 4715 4720 6/0 2 17655 17659 17661 17662 17663 17735 17739 17784 17803 17820 17821 17822 17836 17837 17838 17844 17848 17860 17864 17995 17997 17998 17999 18001 18002 18003 18028 18029 18030 18040 18055 18059 18061 18062 18063 18100 18116 18180 18184 18743 18759 18763 18780 18781 18782 18796 18797 18798 18800 18801 18802 18804 18808 18823 18827 18829 18830 18831 18849 18850 18851 18857 18864 18865 18866 18868 18884 18888 19456 19457 19458 19464 36859 36860 36862 36863https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/154/269?format=asciiInfraredOpticaldefaultJ/AJ/154/269/table4Photometric quasar in S82recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainindexedgmag[-1/30.75] Magnitude in g filter, galactic extinction correctedmagphot.mag;em.opt.Bfloatrmag[16.62/23] Magnitude in r filter, galactic extinction correctedmagphot.mag;em.opt.Rfloatzphot[0.1/5.1] Photometric redshiftsrc.redshift.photfloatz1[0.05/5] The lower limit of z_phot_ (z_1_ in Equation 8)src.redshift.photfloatz2[0.15/5.15] The upper limit of z_phot_ (z_2_ in Equation 8)src.redshift.photfloatPprob[0.052/1] The probability that the redshift locates within (z_1_, z_2_) (P_prob_ in Equation 8)stat.fit.goodnessfloatlogPqso[-2/1.361] The logarithmic likelihood of an object to be a quasar over the whole redshift range (L_QSO_ in Equation 9)stat.likelihoodfloatlogPstar[-322.829/-3.792]? The logarithmic likelihood of an object to be a star (L_Star_ in Equation 15)stat.likelihooddoublenullablelogPgal[-322.829/-5.145]? The logarithmic likelihood of an object being a galaxy (L'_galaxy_ in Equation 20)stat.likelihooddoublenullable