J/A+A/649/A81ivo://CDS.VizieR/J/A+A/649/A81doi:10.26093/cds/vizier.36490081CDSNakoneczny S.J.Bilicki M.Pollo A.Asgari M.Dvornik A.Erben T.,Giblin B.Heymans C.Hildebrandt H.Kannawadi A.Kuijken K.,Napolitano N.R.Valentijn E.2023-10-09T11:23:02Z2023-03-27T08:51:26ZCDS support team

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

cds-question@unistra.frsurveysactive-galactic-nucleiquasarsgalaxiescatalogsphotometryredshiftedtwo-color-diagramsWe present a catalog of quasars with their corresponding redshifts derived from the photometric Kilo-Degree Survey (KiDS) Data Release 4. We achieved it by training machine learning (ML) models using optical ugri and near-infrared ZYJHKs bands, on objects known from SDSS spectroscopy. We define inference subsets from the 45 million objects of the KiDS photometric data limited to 9-band detections, based on a feature space built from magnitudes and their combinations. We show that projections of the high-dimensional feature space on two dimensions can be successfully used instead of the standard color-color plots, to investigate the photometric estimations, compare them with spectroscopic data, and efficiently support the process of building a catalog. The model selection and fine-tuning employs two subsets of objects: those randomly selected and the faintest ones, which allows us to properly fit the bias vs. variance trade-off. We test three ML models: Random Forest (RF), XGBoost (XGB) and Artificial Neural Network (ANN). We find that XGB is the most robust and straightforward model for classification, while ANN performs the best for combined classification and redshift. The ANN inference results are tested using number counts, Gaia parallaxes and other quasar catalogs external to the training set. Based on these tests, we derive the minimum classification probability for quasar candidates which provides the best purity vs. completeness trade-off: p(QSO_cand)>0.9 for r<22, and p(QSO_cand)>0.98 for 22<r<23.5. We find 158000 quasar candidates in the safe inference subset (r<22), and further 185000 in the reliable extrapolation regime (22<r<23.5). Test-data purity equals 97%, completeness is 94%, the latter dropping by 3% in the extrapolation to data fainter by one magnitude than the training set. The photometric redshifts are derived with ANN and modeled with Gaussian uncertainties. Test-data redshift error (mean and scatter) equals 0.009+/-0.12 in the safe subset, and -0.0004+/-0.19 in the extrapolation, averaged over redshift range 0.14<z<3.63 (1st and 99th percentiles). Our success of the extrapolation challenges the way that models are optimized and applied at the faint data end. The resulting catalog is ready for cosmology and Active Galactic Nucleus (AGN) studies.2021A&A...649A..81Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/649/A81CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/624/A13 : KiDS DR3 QSO catalog (Nakoneczny+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/649/A81https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/649/A81http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/649/A81https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/649/A81https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/649/A81http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/649/A81GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/649/A81/qsos (*Catalog of quasar candidates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/649/A81/qsos?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/649/A81/qsos?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/649/A81/qsos?GETtext/xml+votable180.050000true0.02686306-28.684190.005555555555555556Cone search capability for table J/A+A/649/A81/all (*Catalog of all machine learning estimates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/649/A81/all?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/649/A81/all?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/649/A81/all?GETtext/xml+votable180.050000true359.705265-28.668206110.0055555555555555564/1027-1029 1032-1034 1365 1621-1622 1625-1626 1637 1641-1642 1685-1686 1689-1690 1706 1961-1962 2207 2223 2227 2229 2232-2234 2243-2244 2246 2248-2250 2911 2931-2934 2936-2937 5/1024-1026 2048 2050 4103 4107 4120-4122 4124 4140 4144 4160 4224 5459 5468-5469 6397-6399 6461-6463 6477-6479 6481-6483 6492-6494 6497-6499 6508-6510 6512-6514 6553-6558 6561-6563 6572-6574 6576-6578 6592-6594 6717 6719 6733-6735 6737-6739 6748-6750 6754-6755 6764 6766 6768-6770 6819 6828 6830 6848-6849 6912-6914 7823 7843 7852 7856 8823 8827 8887 8891 8903 8907 8913 8921-8922 8940 8944 8967 8971 8982-8983 8988-8990 9004 9008-9009 9088 10239 11262-11263 11639 11643 11719 11723 11740 11753 11756 11758 11760 6/4108 4112 4128 8196-8198 8204 8224 16406-16407 16409-16411 16421-16423 16425-16427 16492-16494 16500-16502 16504-16505 16564-16566 16568-16570 16580 16582 16584-16585 16644-16646 16648-16650 16900-16902 16904-16906 21829-21831 21833 21835 21860-21861 21863 21880-21881 21884 25567 25583 25587 25823 25839 25843 25887 25903 25907 25921 25923 25980 26060 26064 26080 26159 26173-26175 26189-26191 26209-26211 26236 26243 26300 26316 26320 26336 26380 26384 26400 26847 26867 26873 26911 26931 26947 27004 27013-27015 27060-27062 27084 27088 27104 27221 27270-27271 27273-27275 27288 27290-27291 27316 27318-27319 27324 27401 27404 27408 27660 27664 27680 31286 31289-31291 31338-31339 31365-31367 31369-31371 31412-31414 31416-31418 31428 31430 31432-31434 34534 34537-34540 34542-34543 34554 35287 35291 35303 35307 35543 35547 35559 35563 35611 35623 35627 35648-35649 35651 35661 35663 35680 35682-35683 35692-35694 35696-35698 35700-35701 35764-35766 35768-35770 35782 35784-35786 35861-35863 35865-35867 35877-35879 35883 35920 35922-35923 35926 35964 36020-36022 36024 36026 36040-36041 36044 36048 36128 36356-36358 36360-36362 40949-40951 40953-40955 45035-45036 45038-45039 45043 45045-45047 46549-46551 46553-46555 46565-46567 46569-46571 46805-46807 46813 46869-46871 46873-46875 46885-46887 46889-46891 46964-46966 46968-46970 47009 47021 47028-47030 47036 47044-47046 47048-47050 47052 47072https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/649/A81?format=asciidefaultJ/A+A/649/A81/qsos*Catalog of quasar candidatese_zphUncertainty of photometric redshiftstat.errordoubleSubsetML inference subset (1)meta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintKiDSDR4KiDSDR4 designation, KiDSDR4 JHHMMSS.sss+DDMMSS.ssmeta.id;meta.maincharRAJ2000[0/360] Centroid sky position right ascension (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Centroid sky position declination (J2000)degpos.eq.dec;meta.mainindexedrmagr-band GAaP magnitude with optimal MIN_APER (extinction corrected)magphot.mag;em.opt.RfloatClassStarSExtractor star-galaxy classifiermeta.iddoubleMask9-band mask informationmeta.codeintPGalaxyProbability that the source is a galaxystat.fit.goodnessdoublePQSOProbability that the source is a QSOstat.fit.goodnessdoublePStarProbability that the source is a starstat.fit.goodnessdoubleClassObject class with the highest probability, GALAXY, QSO or STARsrc.classcharzphPhotometric redshiftsrc.redshiftdoubleJ/A+A/649/A81/all*Catalog of all machine learning estimatesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintKiDSDR4KiDSDR4 designation, KiDSDR4 JHHMMSS.sss+DDMMSS.ssmeta.id;meta.maincharRAJ2000[0/360] Centroid sky position right ascension (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Centroid sky position declination (J2000)degpos.eq.dec;meta.mainindexedrmagr-band GAaP magnitude with optimal MIN_APER (extinction corrected)magphot.mag;em.opt.RfloatClassStarSExtractor star-galaxy classifiermeta.iddoubleMask9-band mask informationmeta.codeintPGalaxyProbability that the source is a galaxystat.fit.goodnessdoublePQSOProbability that the source is a QSOstat.fit.goodnessdoublePStarProbability that the source is a starstat.fit.goodnessdoubleClassObject class with the highest probability, GALAXY, QSO or STARsrc.classcharzphPhotometric redshiftsrc.redshiftdoublee_zphUncertainty of photometric redshiftstat.errordoubleSubsetML inference subset (1)meta.notechar