Boost recall in QSO selection J/A+A/683/A34 ivo://CDS.VizieR/J/A+A/683/A34 doi:10.26093/cds/vizier.36830034 CDS Calderone G. Guarneri F. Porru M. Cristiani S. Grazian A. Nicastro L.,Bischetti M. Boutsia K. Cupani G. D'Odorico V. Feruglio C. Fontanot F. 2024-11-07T20:01:59Z 2024-03-04T09:27:06Z CDS support team CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France cds-question@unistra.fr surveys quasars redshifted The identification of bright quasi-stellar objects (QSOs) is of fundamental importance to probe the intergalactic medium and address open questions in cosmology. Several approaches have been adopted to find such sources in the currently available photometric surveys, including machine learning methods. However, the rarity of bright QSOs at high redshifts compared to other contaminating sources (such as stars and galaxies) makes the selection of reliable candidates a difficult task, especially when high completeness is required. We present a novel technique to boost recall (i.e., completeness within the considered sample) in the selection of QSOs from photometric datasets dominated by stars, galaxies, and low-z QSOs (imbalanced datasets). Our heuristic method operates by iteratively removing sources whose probability of belonging to a noninteresting class exceeds a user-defined threshold, until the remaining dataset contains mainly high-z QSOs. Any existing machine learning method can be used as the underlying classifier, provided it allows for a classification probability to be estimated. We applied the method to a dataset obtained by cross-matching PanSTARRS1 (DR2), Gaia (DR3), and WISE, and identified the high-z QSO candidates using both our method and its direct multi-label counterpart. We ran several tests by randomly choosing the training and test datasets, and achieved significant improvements in recall which increased from ~50% to ~85% for QSOs with z>2.5, and from ~70% to ~90% for QSOs with z>3. Also, we identified a sample of 3098 new QSO candidates on a sample of 2.6x10^6^ sources with no known classification. We obtained follow-up spectroscopy for 121 candidates, confirming 107 new QSOs with z>2.5. Finally, a comparison of our QSO candidates with those selected by an independent method based on GAIA spectroscopy shows that the two samples overlap by more than 90% and that both selection methods are potentially capable of achieving a high level of completeness. 2024A&A...683A..34C https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/683/A34 Catalog Research IsServedBy TAP VizieR generic service IsServedBy Conesearch service https://cds.unistra.fr/vizier-org/licences_vizier.html https://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/683/A34 https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/683/A34 http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/683/A34 https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/683/A34 https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/683/A34 http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/683/A34 GET text/xml+votable https://tapvizier.cds.unistra.fr/TAPVizieR/tap Cone search capability for table J/A+A/683/A34/cands (The list of QSO candidates (table B1)) https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/683/A34/cands? https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/683/A34/cands? http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/683/A34/cands? GET text/xml+votable 180.0 50000 true 0.341125 -17.0568778 0.005555555555555556 Cone search capability for table J/A+A/683/A34/newqso (The newly identified QSOs (table B1)) https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/683/A34/newqso? https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/683/A34/newqso? http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/683/A34/newqso? GET text/xml+votable 180.0 50000 true 0.341125 -17.0568806 0.005555555555555556 5/4188 4198 4273 4311 4666 5655 5688 6296 6794 9163 11256 12104 12152 6/4 14 22 25 30 34 37 39 41-42 46 50-51 54 61 68 75-76 81 87 92 98 104 112 119 123-124 127 129 131 134-136 139 142-144 150-151 153 159-161 163 165-166 170-172 174 176 178 180 184 186 190-191 194 196 198-199 202 208 224 228 232 256 259 266 272 278 280-281 288 516 525 530-531 533 536-537 552 4109 4119 4149 4156 4160 4174 4181 4195 4199 4208 4229 4263 4271 4273 4298 4302 4306 4323 4368 4373 4378 4386 4400 4615 4621 8219 8225 8234 8244 8249 8277 8287 8298-8299 8324 8329 8332 8358 8361 8385 8428 8450 8488 8713 8715 8739 8742 12289 12294 12296-12298 12302 12304 12313-12314 12319 12343 12355 12357 12360 12364-12365 12370 12380 12389 12409 12413 12415 12559 12561 12569 12572 12576 12582 16474 16477 16479 16485 16490 16492-16493 16498-16500 16503 16511 16534 16541-16542 16555-16556 16560 16562-16563 16568-16569 16578 16584 16586 16589 16592-16594 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48691-48692 48697 48702 48705-48706 48708 48713-48715 48719 48721-48722 48724-48725 48727 48732 48734 48736 48739 48748-48749 48755 48758 48760 48762-48763 48773 48832 48839 48845-48846 48848 48851-48853 48860 48884 48897-48898 48901 48915 48917-48918 48921-48923 48926 48934 48938 48949 48951-48953 48960-48962 48964 48966-48968 48971 48974 48976 48978 48985-48986 48994-48995 49001 49003 49015 49017 49019 49029 49032 49034 49036 49038 49046 49053 49056 49058 49061-49062 49073 49076 49078-49079 49082 49089 49097-49099 49103 49108-49109 49113 49116 49125-49127 49133-49135 49139-49140 49149 https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/683/A34?format=ascii default J/A+A/683/A34/cands The list of QSO candidates (table B1) recno Record number assigned by the VizieR team. Should Not be used for identification. meta.record int qid Qubrics internal ID meta.id;meta.main long RAJ2000 Right Ascension (J2000) pos.eq.ra;meta.main DEJ2000 Declination (J2000) pos.eq.dec;meta.main imag PanSTARRS i magnitude mag phot.mag;em.opt.I float
J/A+A/683/A34/newqso The newly identified QSOs (table B1) recno Record number assigned by the VizieR team. Should Not be used for identification. meta.record int qid Qubrics internal ID meta.id;meta.main long RAJ2000 Right Ascension (J2000) pos.eq.ra;meta.main DEJ2000 Declination (J2000) pos.eq.dec;meta.main imag PanSTARRS i magnitude mag phot.mag;em.opt.I float z Spectroscopic redshift src.redshift float Notes Notes meta.note char