J/MNRAS/391/369ivo://CDS.VizieR/J/MNRAS/391/369doi:10.26093/cds/vizier.73910369CDSCarballo R.Gonzalez-Serrano J.I.Benn C.R.Jimenez-Lujan F.2024-07-07T20:17:30Z2010-02-09T11:32:46ZCDS support team

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

cds-question@unistra.frquasarsredshiftedradio-sourcesvisible-astronomysloan-photometryWe aim to obtain a complete sample of redshift z>=3.6 radio quasi-stellar objects (QSOs) from the Faint Images of the Radio Sky at Twenty cm survey (FIRST) sources (S_1.4GHz_>1mJy) having star-like counterparts in the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) photometric survey (r_AB_<=20.2). Our starting sample of 8665 FIRST-DR5 pairs includes 4250 objects with spectra in DR5, 52 of these being z>=3.6 QSOs. We found that simple supervised neural networks, trained on the sources with DR5 spectra, and using optical photometry and radio data, are very effective for identifying high-z QSOs in a sample without spectra. For the sources with DR5 spectra the technique yields a completeness (fraction of actual high-z QSOs classified as such by the neural network) of 96 per cent, and an efficiency (fraction of objects selected by the neural network as high-z QSOs that actually are high-z QSOs) of 62 per cent. Applying the trained networks to the 4415 sources without DR5 spectra we found 58 z>=3.6 QSO candidates. We obtained spectra of 27 of them, and 17 are confirmed as high-z QSOs. Spectra of 13 additional candidates from the literature and from SDSS Data Release 6 (DR6) revealed seven more z>=3.6 QSOs, giving an overall efficiency of 60 per cent (24/40).2008MNRAS.391..369Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/391/369CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/276 : The SDSS Photometric Catalog, Release 5 (Adelman-McCarthy+, 2007)J/MNRAS/348/857 : Radio-loud QSOs at z~4 (Holt+, 2004)J/MNRAS/370/1034 : FIRST-APM-SDSS survey for high-z radio QSOshttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/391/369https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/391/369http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/391/369https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/391/369https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/391/369http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/391/369GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/391/369/table2 (FIRST-DR5 sources with SDSS spectra, and classified by SDSS as z>=3.6 QSOs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/391/369/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/391/369/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/391/369/table2?GETtext/xml+votable180.050000true28.4150417-0.18472220.005555555555555556Cone search capability for table J/MNRAS/391/369/table5 (z>=3.6 QSO candidates identified by the NN in the FIRST-SDSS DR5 unlabelled sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/391/369/table5?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/391/369/table5?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/391/369/table5?GETtext/xml+votable180.050000true111.326083337.08841670.0055555555555555566/0 4168 4177 4435 4638 4641 4677 4692 4867 4875 4902 5028 5053 5184 5249 5261 5346 5448 5468 5533 5546 5563 5578 5620 5802 5890 6085 6219 6258 6386 6457 6480 6582 6616 7193 7199 7237 7301 7320 7488 8218 8262 8590 8777 8841 8988 9260 9372 9635 9964 9988 10453 10462 10549 10677 10707 10802 10885 10959 10987 11056 11108 11161 11303 11308 11368 11418 11494 11805 17302 17818 18624 18859 22484 25565 25990 26056 26098 26213 26221 26355 26396 26520 26525 26568 27063 27100 27559 27584 27588 27874 27899 27910 27931 27968 28051 28111 28173 28177 28308 28397 28482 28492 28520 28579 28615 31468 31592 32475 324832.85864675833786e-19 3.5010283109654867e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/391/369?format=asciiOpticalRadiodefaultJ/MNRAS/391/369/table2FIRST-DR5 sources with SDSS spectra, and classified by SDSS as z>=3.6 QSOsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000SDSS Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000SDSS Declination (J2000)pos.eq.dec;meta.mainrmagSDSS dereddened PSF r_AB_ magnitudemagphot.mag;em.opt.RfloatS1.4GHzFIRST total radio flux densitymJyphot.flux.density;em.radio.750-1500MHzfloatzSDSS redshiftsrc.redshiftfloatn_z[a] a = revised redshift from DR5Q, see Section 2meta.notecharNN[0.1,1] Neuronal network (NN) output (y_med_>=.01) see Section 4.2)meta.notefloatPSampIncluded in previous samples (1)meta.codecharNotesNotes (G1)meta.notecharSDSSDisplay the SDSS data for this quasarmeta.ref.urlcharJ/MNRAS/391/369/table5z>=3.6 QSO candidates identified by the NN in the FIRST-SDSS DR5 unlabelled samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000SDSS Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000SDSS Declination (J2000)pos.eq.dec;meta.mainrmagSDSS dereddened PSF r_AB_ magnitudemagphot.mag;em.opt.RfloatS1.4GHzFIRST total radio flux densitymJyphot.flux.density;em.radio.750-1500MHzfloatNN[0.1,1] Neuronal network (NN) output (y_med_>=.01) see Section 4.2)meta.notefloatzNED? Redshift from NEDsrc.redshiftfloatnullablez? Redshift from William Herschel Telescopesrc.redshiftfloatnullablezDR6? Redshift from SDSS DR6src.redshiftfloatnullableNotesNotes (G1)meta.notecharFlag[Yes] indicates sources located within the spectroscopic plates available in DR6meta.code.errorcharSDSSDisplay the SDSS data for this quasarmeta.ref.urlchar