J/A+A/699/A132ivo://CDS.VizieR/J/A+A/699/A132doi:10.26093/cds/vizier/bc-nv/lbdcCDSTiwari A.Vivek M.2026-08-03T06:55:21Z2025-07-02T08:13:03ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiquasarsgalaxiesspectroscopyultraviolet-astronomystellar-spectral-typesWe present the results of applying anomaly detection algorithms to a quasar spectroscopic sub-sample from the SDSS DR16 quasar catalog, covering the redshift range 1.88<=z<=2.47. Principal component analysis (PCA) was employed for dimensionality reduction of the quasar spectra, followed by hierarchical K-Means clustering in a 20-dimensional PCA eigenvector hyperspace. To prevent broad absorption line (BAL) quasars from being identified as the primary anomaly group, we conducted the analysis separately on BAL and Non-BAL QSOs, comparing both categories for a clearer identification of other anomalous quasar type. We identified 2066, anomalous quasars, categorized into 10 broad groups. The anomalous groups include CIV Peakers-quasars with extremely strong and narrow CIV emission lines; Excess SiIV emitters-quasars where the SiIV line is as strong as the CIV line; and SiIV deficient anomalies, which exhibit significantly weaker SiIV emission compared to typical quasars. The anomalous nature of these quasars is attributed to lower Eddington ratios for CIV Peakers, super-solar metallicity for Excess SiIV emitters, and sub-solar metallicity for Si iv deficient anomalies. Additionally, we identified four groups of BAL anomalies: Blue BALs, Flat BALs, reddened BALs, and FeLoBALs, distinguished primarily by the strength of reddening in these sources. Further, among the non-BAL quasars, we identified three types of reddened anomaly groups classified as heavily reddened, moderately reddened, and plateau-shaped spectrum quasars, each exhibiting varying degrees of reddening. The detected anomalies are presented as a value-added catalog.2025A&A...699A.132Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/699/A132CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/699/A132https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/699/A132http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/699/A132https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/699/A132https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/699/A132http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/699/A132GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/699/A132/catalog (SDSS_NAME, RA-DEC, Redshift, r band mag (from SDSS DR16Q) and Anomaly Type for the 2066 detected anomalies (table 5))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/699/A132/catalog?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/699/A132/catalog?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/699/A132/catalog?GETtext/xml+votable180.050000true3.6632734558298-4.86082365366460.0055555555555555565/2678 6/0 30-31 35 50 527 558 652 666 678 691-692 703 736 738 740 747 899 1678 2051 2064 2084 2087 2097 2109 2113 2115 2118 2136 2140 2146 2150 2158 2160-2161 2174 2178 2184 2199 2217 2220-2221 2227 2229-2230 2239 2251 2256-2257 2282 2297 2560-2561 2564 2575 2578 2595-2596 2602 4096 4106 4115 4137 4142 4147 4166 4175 4178 4183 4209 4216-4217 4227 4234 4240 4257 4267 4281 4287 4338 4354 4364 4367 4371-4372 4390 4392 4411 4415 4419 4422 4426 4468 4482 4486 4493 4507 4516 4538 4565 4567 4574 4583 4637 4643 4656-4657 4680 4682 4698-4701 4703 4712 4720-4721 4727 4731 4746-4747 4773 4775 4794-4795 4799 4817 4821 4830-4831 4833 4835 4854 4856 4865 4868 4879 4893 4906 4929 4932 4940 4946 4951 4955 4970 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27911 27936 27941 27946 27948-27949 27951 27978 27986 27989 28000 28021 28023 28037 28042 28052 28088-28089 28112 28114 28148-28149 28157 28171 28173 28185 28187-28188 28206 28229 28241 28255 28270 28272 28279 28286 28293 28298 28303 28309 28316 28325 28332 28339 28348 28356 28361 28364 28385 28388 28390-28392 28397 28399 28401 28415 28430 28436 28438 28449 28452-28453 28456 28460 28491 28495 28502 28504 28509 28528 28534 28551 28561 28564 28575 28590 28601 28603-28604 28607 28617 28621 28625 28638 28647 28654 30035 30037 30044 31377 31394 31398-31399 31403 31432 31470 31476 31550 31599 31621-31622 31637 31653-31654 31660 31664 31668 31675 31677 31692 31696 31703 31712 31714 31734 31741 32402 32426 32429 32431 32481 32485 32510 32641 32686 36734 36761 36779 36784-36785 36802 36806 36808 36814-36815 36833 36835 36838 36844 36846 45055 48990 49016 49018 49094 49106 49122-49123https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/699/A132?format=asciiUVdefaultJ/A+A/699/A132/catalogSDSS_NAME, RA-DEC, Redshift, r band mag (from SDSS DR16Q) and Anomaly Type for the 2066 detected anomalies (table 5)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS-designation (HHMMSS.ss+DDMMSS.s, J2000)meta.id;meta.maincharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainzRedshift (best estimate from DR16Q)src.redshiftdoublermagPSFMAG in r bandmagphot.mag;em.opt.RdoubleAnomalyTypeType of anomaly (Label)meta.notecharSimbadSimbad column added by the CDSmeta.ref.urlchar