J/AJ/162/72ivo://CDS.VizieR/J/AJ/162/72doi:10.26093/cds/vizier.51620072CDSWenzl L.Schindler J.-T.Fan X.Andika I.T.Banados E.Decarli R.,Jahnke K.Mazzucchelli C.Onoue M.Venemans B.P.Walter F.Yang J.2022-03-14T07:01:17Z2021-12-14T08:37:38ZCDS support team

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

cds-question@unistra.frquasarsactive-galactic-nucleiblack-holesredshiftedvisible-astronomyspectroscopyinfrared-astronomyWe present a method of selecting quasars up to redshift ~6 with random forests, a supervised machine-learning method, applied to Pan-STARRS1 and WISE data. We find that, thanks to the increasing set of known quasars, we can assemble a training set that enables supervised machine-learning algorithms to become a competitive alternative to other methods up to this redshift. We present a candidate set for the redshift range 4.8-6.3, which includes the region around z=5.5 where selecting quasars is difficult due to their photometric similarity to red and brown dwarfs. We demonstrate that, under our survey restrictions, we can reach a high completeness (66%{+/-}7% below redshift 5.6/83_-9_^+6^% above redshift 5.6) while maintaining a high selection efficiency (78_-8_^+10^%/94_-8_^+5^% ). Our selection efficiency is estimated via a novel method based on the different distributions of quasars and contaminants on the sky. The final catalog of 515 candidates includes 225 known quasars. We predict the candidate catalog to contain additional 148_-33_^+41^ new quasars below redshift 5.6 and 45_-8_^+5^ above, and we make the catalog publicly available. Spectroscopic follow-up observations of 37 candidates led us to discover 20 new high redshift quasars (18 at 4.6<~z<~5.5, 2z~5.7). These observations are consistent with our predictions on efficiency. We argue that random forests can lead to higher completeness because our candidate set contains a number of objects that would be rejected by common color cuts, including one of the newly discovered redshift 5.7 quasars.2021AJ....162...72Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/162/72CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)II/328 : AllWISE Data Release (Cutri+ 2013)II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)VII/285 : Gaia DR2 quasar and galaxy classification (Bailer-Jones+, 2019)VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)J/ApJ/768/105 : z~5 QSO luminosity function SDSS Stripe 82 (McGreer+, 2013)J/ApJ/773/14 : BOSS: quasar luminosity function (Ross+, 2013)J/ApJ/819/24 : z>4.5 QSOs with SDSS and WISE. I. Opt. spectra (Wang+, 2016)J/ApJS/227/11 : PS1 z>5.6 quasars follow-up (Banados+, 2016)J/AJ/156/18 : APOGEE DR14:Bin companions evolved stars (Price-Whelan+, 2018)J/A+A/624/A13 : KiDS DR3 QSO catalog (Nakoneczny+, 2019)J/A+A/632/A56 : KiDS-BEXGO catalog (Khramtsov+, 2019)J/ApJS/243/5 : The ELQS in the PS1 footprint (PS-ELQS) (Schindler+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/162/72https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/162/72http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/162/72https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/162/72https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/162/72http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/162/72GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/162/72/table7 (List of quasar candidates that are part of the high-z candidates selection and information about their observation status)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/162/72/table7?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/162/72/table7?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/162/72/table7?GETtext/xml+votable180.050000true73.0265845163-5.9421750362799990.005555555555555556Cone search capability for table J/AJ/162/72/table9 (List of newly discovered quasars in this work)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/162/72/table9?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/162/72/table9?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/162/72/table9?GETtext/xml+votable180.050000true1.10781106-21.181681950.0055555555555555566/20 33-34 42 689 717 956 2058 2138 2241 2276 2346 2368 2447 2584 2587 2589-2590 2626 3957 4076 4242 4251 4269 4279 4337 4386 4472 4595 4619 4626 4641 4754 4822 4843 4872 4892 4903 4909 4911-4912 4931 5016 5066 5121 5153 5166 5170 5215-5216 5249 5267 5333 5400 5404 5423 5440 5444 5473 5517 5528 5537 5566 5710 5723 5752 5828 5833 5905-5906 5923 6071-6072 6172 6388 6415 6493 6589 6646 6649 6917 6974 7020 7119 7182 7197 7230 7264 7326 7334 7423 7429 7459 7464 7478 7550 7595 7793 7823 7838 7841 7889 7896 7921 7930 7942 7961 8002 8012 8032 8035 8051 8053 8061 8068 8076 8079 8103 8146 8202 8213 8319 8323 8354 8384 8440 8477 8505 8680 8713 8722 8726 8787 8813 8819 8829 8843 8846 8875 9020 9039 9084 9097 9120 9164 9195 9275 9285 9333 9373 9615 9627 9716 9733 9754 9796 9818 9831 9906 9981 10008 10024 10027 10121 10123 10140 10193 10197 10246 10254 10270 10336 10451 10456 10466 10497 10501 10508 10646 10656 10686 10756 10759 10788 10803 10933 10948 10955 10968 11027 11116 11143 11171 11219 11382 11393 11429 11460 11473 11561 11695 11712 11715 11719 11729 11774 11787 11832 11980 12014 12161 12169 12185 12227 12567 12599 13407 13424 13438 14891 14983 14992 15048 15233 15251 15269 16015 16098 16595 16597-16598 16631 16666 16752 16769 16815 16820 16829 16996 17008 17068 17084 17158 17185 17203 17245 17252 17258 17286 17358 17362 17374 17379 17382 17504 17577 17613 17649 17654 17691 17808 17898 17915 17989 18076 18222 18242 18295 18310 18378 18430 18482 18512 18567 18605 18627 18638 18706 18810 18947 19033 19046 19067 19181 19289 19348 19477 19506 19525 19584 19653 19783 19795 20010 20037 20145 20173 20182 20191 20228 20273 20275 20321 20388 20390 20417 20422 20441 20466 20656 20676 21062 21872 21879 21989 22528 22571 22654 22686 22798 22826 22922 23085 23170 23175 24677 24750 24774 24895 24971 24988 25093 25107 25129 25165 25173 25176 25184 25228 25302 25334 25375 25399 25456 25478 25484 25576 25674 25728 25782 25857 25887 25987 26080 26091 26280 26341 26431 26451 26475 26524 26527 26542 26567 26589 26701 26722 26760 26789 26805 26816 26857 26859 26864 26866 26870 26885 26902 27041 27046 27084 27090 27112 27150 27165 27194 27198 27269 27359 27431 27440 27452 27564 27615 27692 27696 27700 27702 27706 27790 27792 27833 27876 27901 27964 27972 28023 28027 28067 28078 28080 28144 28180 28232 28256 28291 28369 28415 28467 28490 28506 28572 28639 30004 31224 31326 31493 31529 31534 31539 31550 31660 31709 32387 32410 32474 32489 32496 32646 35673 35675 35776 35785 35790 35810 35831 36015 36074 36102 36182 36300 36377 36406 36522 36530 36586 36660 36733 36792 36840 38743 38885 40168 40196 40206 40241 40246-40247 40255 40325 40327 40369 40383 40388 40403 40408 40423 40727 40754 40761 40763 40786 40788 40851 40926 40938 40959 43950 43959 44007 44199 44445 44575 44577 44595 44604 44618 44731 44747 44802 44908 44931 44941 44977 44991 44996 47003 48235 48283 48298 48313 48334 48341 48411 48504 48512 48549-48550 49083 49095https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/162/72?format=asciiOpticalInfrareddefaultJ/AJ/162/72/table7List of quasar candidates that are part of the high-z candidates selection and information about their observation statusWISEName in ALLWISE catalogmeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIndex[0/514] Sequential running indexmeta.codeintRAJ2000[0/360] Pan-STARRS Right Ascension, (J2000)degpos.eq.ra;meta.mainDEJ2000[-30/86] Pan-STARRS Declination (J2000)degpos.eq.dec;meta.mainzPSF[18.3/20.5] z stacked PSF mag in Pan-STARRSmagmeta.codedoublePz[0.4/1] Probability for high-z classmeta.code;stat.probabilitydoublePQSO[0.4/1] Summed probability for quasar classesmeta.code;stat.probabilitydoublePMstarProbability for M star classmeta.code;stat.probabilitycharzPredicted[4.8/6.2] High redshift regression resultmeta.codedoublezspec[4.7/6.3]? Redshift determined from spectrummeta.codefloatnullableKnown?Boolean whether quasar is known in literaturemeta.codeintPhoto?Boolean whether we obtained photometric follow-upmeta.code;stat.probabilityintObs?Boolean whether we took a spectrum of the objectmeta.codeintStill?Boolean whether object still has to be observedmeta.codeintJ/AJ/162/72/table9List of newly discovered quasars in this workrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintWISEName in ALLWISE catalogmeta.id;meta.maincharRAJ2000[1.1/353] Pan-STARRS mean Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[-30/30] Pan-STARRS mean Declination (J2000)degpos.eq.dec;meta.mainzMag[17.8/20.4] z stacked PSF magnitude in Pan-STARRS, extinction correctedmagphot.magdoubleM1450[-28.3/-25.7] M1450 based on PS photometrymagphot.magdoubleInstTelescope and Instrument used for observationinstr.setupcharObs[18/21] Observation yeartime.epochz[4.6/5.8] Observed Spectroscopic redshiftsrc.redshiftfloat