J/MNRAS/307/293ivo://CDS.VizieR/J/MNRAS/307/293doi:10.26093/cds/vizier.73070293CDSRiley J.M.Rawlings S.McMahon R.G.Blundell K.M.Miller P.Lacy M.,Waldram E.M.2024-06-26T20:16:07Z2013-10-21T13:26:23ZCDS support team

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

cds-question@unistra.frquasarsradio-sourcessurveysWe describe the selection of candidate radio-loud quasars obtained by cross-matching radio source positions from the low-frequency (151-MHz) 7C survey with optical positions from five pairs of EO POSS-1 plates scanned with the Cambridge Automatic Plate-measuring Machine (APM). The sky region studied is centred at RA=10h28m, DE=+41{deg} and covers ~0.057sr. We present VLA observations of the quasar candidates, and tabulate various properties derived from the radio maps. We discuss the selection criteria of the resulting '7CQ' sample of radio-loud quasars. The 70 confirmed quasars, and some fraction of the 36 unconfirmed candidates, constitute a filtered sample with the following selection criteria: 151-MHz flux density S_151_>100mJy; POSS-I E-plate magnitude E~R<20; POSS-I colour (O-E)<1.8; the effective area of the survey drops significantly below S_151_~200mJy. We argue that the colour criterion excludes few if any quasars, but note, on the basis of recent work by Willott et al. (1998MNRAS.300..625W), that the E magnitude limit probably excludes more than 50 per cent of the radio-loud quasars.1999MNRAS.307..293Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/307/293CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+AS/110/419 : 7C: survey of radio sources (Visser+, 1995)J/MNRAS/246/110 : 7C survey of radio sources at 151 MHz (McGilchrist+ 1990)J/MNRAS/276/614 : Radio-optical 151MHz survey of the N. Ecl. Cap (Lacy+ 1995)J/MNRAS/282/779 : 7C: 151-MHz survey of region 9-16h 20-35deg (Waldram+ 1996)J/MNRAS/294/607 : 7C(G) 151MHz survey of the Galactic plane (Vessey+ 1998)J/MNRAS/298/637 : 7C: 151MHz survey of 3 regions (Pooley+, 1998)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/307/293https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/307/293http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/307/293https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/307/293https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/307/293http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/307/293GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/307/293/7CQ (Summary of the radio and optical properties of the candidate 7CQ quasars: main (table1) and subsidiary (table2) samples)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/307/293/7CQ?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/307/293/7CQ?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/307/293/7CQ?GETtext/xml+votable180.050000true149.660932343.27209390.0055555555555555565/1341 1391 1425 1430-1431 1433 1461 1475-1477 1482 6/5301 5303 5309 5315 5319 5322 5324 5326-5327 5330 5336 5339 5342 5344-5345 5348-5349 5351 5353 5355 5357 5359 5361-5363 5369-5371 5375 5513-5516 5536 5539-5541 5543 5545-5546 5550-5552 5554 5556 5561-5563 5610 5699 5707 5710-5711 5713-5714 5717-5719 5729 5731 5740-5741 5743 5746 5748-5749 5751 5753-5757 5759 5855 5889-5891 5893-5895 5897 5912 5914-5918 5920-5922 5925-5927 5932-5933 5936-5938 6017-60181.0005364593029448e-25 9.87284372295006e-25https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/307/293?format=asciiRadiodefaultJ/MNRAS/307/293/7CQSummary of the radio and optical properties of the candidate 7CQ quasars: main (table1) and subsidiary (table2) samplesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTSimbad column added by the CDSmeta.id;meta.datasetcharNote[NRST*] Note (1)meta.notecharNameName of the source (HHMM+DDd), computed from the positionmeta.id;meta.maincharRAB1950Radio source right ascension (B1950) (2)pos.eq.ra;meta.mainDEB1950Radio source declination (B1950)pos.eq.dec;meta.mainSepSeparation of the 7C radio source position and the APM optical positionarcsecpos;arith.difffloatOmag? POSS-1 O magnitude of the quasar candidatemagphot.mag;em.opt.BfloatnullableO-E? POSS-1 O-E colour index of the quasar candidatemagphot.color;em.opt.B;em.opt.RfloatnullabledRA? Difference between the radio position and that of the quasar candidate (in the sense radio minus optical)spos.eq.ra;arith.difffloatnullabledDE? Difference between the radio position and that of the quasar candidate (in the sense radio minus optical)arcsecpos.eq.dec;arith.difffloatnullableS.15? Flux density at 151 MHz, from the 7C cataloguemJyphot.flux.density;em.radio.100-200MHzintnullableS1.5? Flux density either at 1.49GHz from our own VLA observations (or 1.40GHz, see n_S1.5)mJyphot.flux.density;em.radio.750-1500MHzfloatnullablen_S1.5[)] ): S1.5 contains 1.40GHz flux density from the NVSS surveymeta.notecharf_S1.5[mc] Not in NVSS, or confusion (3)meta.codecharSI? Spectral index between 151MHz and 1.49GHz (or 1.4 if n_SI=")")GHzmJyphot.flux.density;em.radio.100-200MHzfloatnullablen_SI[)] ): SI contains spectral index between 151MHz and 1.4GHzmeta.notecharf_SI[c] Source confusion (3)meta.codecharScore? Flux density of the core at 1.49GHz (4)mJyphot.flux.density;em.radiofloatnullablel_theta[<= ] Limit flag on thetameta.code.error;pos.posAngchartheta? Angular size of the source {theta}arcsecphys.angSizefloatnullablen_theta[?)c] Note on theta (5)meta.notecharf_theta[7C ] 7C if theta from the 7C cataloguemeta.codecharTypeOptical type (6)src.classcharRflFlags associated with the radio data (7)meta.notecharRem[*] * indicated a note in notes.dat filemeta.notechar_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)pos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)pos.eq.decnullableindexedJ/MNRAS/307/293/notesIndividual notesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName (HHMM+DDm)meta.id;meta.maincharNoteText of the notemeta.notechar