Quasars from the 7C survey - I. Sample selection and radio maps

Journal article

We 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-I plates scanned with the Cambridge Automatic Plate-measuring Machine (APM). The sky region studied is centred at RA 10h 28m, Dec.+41° and covers ≈0.057 sr. 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 S151 > 100 mJy; POSS-I E-plate magnitude E ≈ R < 20; POSS-I colour (O - E) < 1.8; the effective area of the survey drops significantly below S151 ≈ 200 mJy. We argue that the colour criterion excludes few if any quasars, but note, on the basis of recent work by Willott et al., that the E magnitude limit probably excludes more than 50 per cent of the radio-loud quasars.

Authors: Riley, J; Rawlings, S; McMahon, R; Blundell, K; Miller, P

• Publication status: Published
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 307
• Issue: 2
• Pages: 293-314
• Publication date: 1999-08-01
• DOI: 10.1046/j.1365-8711.1999.02540.x
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: quasars : general; radio continuum : galaxies; galaxies : active