J/A+A/624/A13ivo://CDS.VizieR/J/A+A/624/A13doi:10.26093/cds/vizier.36240013CDSNakoneczny S.Bilicki M.Soalrz A.Pollo A.Maddox N.Spiniello C.,Brescia M.Napolitano N.R.2019-04-08T13:04:27Z2019-04-01T09:51:14ZCDS support team

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

cds-question@unistra.frsurveysactive-galactic-nucleiquasarsgalaxiescatalogsphotometrytwo-color-diagramsWe present a catalog of quasars selected from broad-band photometric ugri data of the Kilo-Degree Survey Data Release 3 (KiDS DR3). The QSOs are identified by the random forest (RF) supervised machine learning model, trained on Sloan Digital Sky Survey (SDSS) DR14 spectroscopic data. We first cleaned the input KiDS data of entries with excessively noisy, missing or otherwise problematic measurements. Applying a feature importance analysis, we then tune the algorithm and identify in the KiDS multiband catalog the 17 most useful features for the classification, namely magnitudes, colors, magnitude ratios, and the stellarity index. We used the t-SNE algorithm to map the multidimensional photometric data onto 2D planes and compare the coverage of the training and inference sets. We limited the inference set to r<22 to avoid extrapolation beyond the feature space covered by training, as the SDSS spectroscopic sample is considerably shallower than KiDS. This gives 3.4 million objects in the final inference sample, from which the random forest identified 190,000 quasar candidates. Accuracy of 97% (percentage of correctly classified objects), purity of 91% (percentage of true quasars within the objects classified as such), and completeness of 87% (detection ratio of all true quasars), as derived from a test set extracted from SDSS and not used in the training, are confirmed by comparison with external spectroscopic and photometric QSO catalogs overlapping with the KiDS footprint. The robustness of our results is strengthened by number counts of the quasar candidates in the r band, as well as by their mid-infrared colors available from the Wide-field Infrared Survey Explorer (WISE). An analysis of parallaxes and proper motions of our QSO candidates found also in Gaia DR2 suggests that a probability cut of pQSO>0.8 is optimal for purity, whereas pQSO>0.7 is preferable for better completeness. Our study presents the first comprehensive quasar selection from deep high-quality KiDS data and will serve as the basis for versatile studies of the QSO population detected by this survey. We publicly release the resulting catalog at http://kids.strw.leidenuniv.nl/DR3/quasarcatalog.php, and the code at https://github.com/snakoneczny/kids-quasars2019A&A...624A..13Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/624/A13CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/347 : KiDS-ESO-DR3 multi-band source catalog (de Jong+, 2017)VII/279 : SDSS quasar catalog: twelfth data release (Paris+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/624/A13https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/624/A13http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/624/A13https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/624/A13https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/624/A13http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/624/A13GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/624/A13/kids3qso (Objects from KiDS DR3 limited at R<22, with 3-class (QSO-STAR-GALAXY) photometric classification results)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/624/A13/kids3qso?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/624/A13/kids3qso?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/624/A13/kids3qso?GETtext/xml+votable180.050000true2.111e-05-33.000313060.0055555555555555564/1032 1365 1621-1622 1642 1685 1706 2244 2248 2911 2931-2932 5/1024-1026 2048 2050 4109-4111 4132 4136 4138 5459 5468-5469 6397-6399 6477-6479 6481-6483 6492-6494 6500-6501 6503 6505 6512-6514 6561-6564 6566 6572-6574 6737-6739 6744-6745 6748-6750 6814 6819 6828 6830 6912-6914 7834 7845-7846 7856-7857 8823 8829 8831 8907 8967 8971 8973-8975 8982 8984-8986 8996-8998 10239 11262-11263 11639 11643 11719 11732-11734 11736-11738 11745-11747 11749 6/4108-4110 4112-4114 4128-4130 8198 8204 8206 8224-8226 16407 16412-16413 16415 16429-16431 16433-16435 16450 16456 16482 16532 16534 16536-16537 16548-16550 16556 21829-21831 21833 21835 21860-21861 21863 21880-21881 21884 25567 25581-25583 25585 25587 25885-25887 25901-25903 25905-25907 25922-25923 25980-25982 25988-25989 25998-25999 26009 26028-26029 26037 26039 26060-26062 26064 26066 26080-26081 26158-26159 26189-26191 26202 26213 26224 26241-26243 26260 26262 26268 26270-26271 26300-26302 26336 26338 26909 26911 26945-26947 26985-26987 26991 27004-27006 27029 27031 27033-27036 27038 27045-27047 27049-27054 27056-27058 27072-27074 27088-27089 27221-27223 27229 27245 27247 27270-27271 27273-27275 27288 27290-27291 27316 27318-27319 27324-27325 27392-27394 27660-27662 27664-27666 27680-27682 31293-31295 31330-31331 31340 31342-31343 31373 31375 31377-31379 31388-31390 31393-31395 31397-31399 31401-31404 31408-31410 31433 31436-31437 34539-34540 34542-34543 35287 35291 35313-35315 35320-35321 35323 35627 35665 35668-35669 35716 35863 35867 35879 35889-35891 35922-35923 35948 35952 36000-36002 36008 36010 36016 36032 40949-40951 40953-40955 45037-45039 45042-45043 45046 46551 46555 46567 46571 46813 46815 46837 46871 46875 46893-46895 46940 46956-46957 46960 46962 46977-46979 46992-46993 46995 47000 47002 47008-47009 47011-47014 47040-47042https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/624/A13?format=asciidefaultJ/A+A/624/A13/kids3qsoObjects from KiDS DR3 limited at R<22, with 3-class (QSO-STAR-GALAXY) photometric classification resultsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDSource identifier (KiDS JHHMMSS.ss+DDMMSS.ss)meta.id;meta.maincharindexedRAJ2000Right ascension (J2000.0)degpos.eq.ra;meta.mainindexedDEJ2000Declination (J2000.0)degpos.eq.dec;meta.mainindexedClassSource classification (GALAXY - QSO - STAR)meta.code.classcharPgalSource probability of being a galaxystat.fit.goodnessdoublePQSOSource probability of being a quasarstat.fit.goodnessdoublePstarSource probability of being a starstat.fit.goodnessdouble