A FIRST-APM-SDSS survey for high-redshift radio QSOs

Abstract

We selected from VLA-FIRST a sample of 94 objects starlike in SDSSS, and with APM colour O-E>2, i.e. consistent with their being high-z QSOs. 78 candidates were classified spectroscopically from published data (mainly SDSS) or observations reported here. The fractions of QSOs (51/78) and z > 3 QSOs (23/78) are comparable to those found in other photometric searches for high-z QSOs. We confirm that O-E>2 ensures inclusion of all QSOs with 3.7 < z < 4.4. The fraction of broad absorption line (BAL) QSOs for 2 < z < 4.4 is 27+-10 per cent (7/26), and the estimated BAL fraction for radio loud (RL) QSOs is at least as high as for optically selected QSOs (about 13 per cent). The high BAL fraction and the high fraction of LoBALs in our sample are likely due to the red colour selection. The space density of RL QSOs for 3.7 < z < 4.4, MAB (1450 A) < -26.6 and P(1.4 GHz) > 10^25.7 W Hz^(-1) is 1.7+-0.6 Gpc^(-3). Adopting a RL fraction 13.4+-3 per cent, this corresponds to rho = 12.5+-5.6 Gpc^(-3), in good agreement with the SDSS QSO luminosity function in Fan et al. (2001). We note the unusual QSO FIRST 1413+4505 (z=3.11), which shows strong associated Lyalpha absorption and an extreme observed luminosity, L about 2 x 10^(15) solar luminosities.

arXiv commentAccepted for publication in MNRAS; 9 figures and 6 tables; Table 2 is in landscape format

References in corpus (27)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• The Third Data Release of the Sloan Digital Sky Survey
• Optical and Radio Properties of Extragalactic Sources Observed by the FIRST and SDSS Surveys
• High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data IV: Luminosity Function from the Fall Equatorial Stripe Sampl
• A hyperluminous galaxy at z = 2.8 found in a deep submillimetre survey
• The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later
• The Sloan Digital Sky Survey Quasar Catalog III. Third Data Release
• Properties of Radio-Selected Broad Absorption-Line Quasars from the FIRST Survey
• Continuum and Emission-Line Properties of Broad Absorption Line Quasars
• The UV Properties of the Narrow Line Quasar I Zwicky 1
• The FIRST Radio-Loud Broad Absorption Line QSO and Evidence for a Hidden Population of Quasars
• APM 08279+5255: an ultraluminous BAL quasar at a redshift z=3.87
• High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data III: A Color Selected Sample at i^*<20 in the Fall Equatorial Stripe
• A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Early Data Release
• The FIRST Bright QSO Survey
• APM z>4 QSO Survey: Spectra and Intervening Absorption Systems
• Absorption Systems in the Spectra of 66 z > 4 Quasars
• The ATESP radio survey III. Source counts
• Optical Counterparts for 70,000 Radio Sources: APM Identifications for the FIRST Radio Survey
• Unusual high-redshift radio BAL quasar 1624+3758
• Red Quasars and Quasar Evolution: the Case of BALQSO FIRST J155633.8+351758
• Decline of the space density of quasars between z=2 and z=4
• A search for distant radio-loud quasars in the CLASS survey: three new radio-selected quasars at z>4
• A Search for High-redshift Quasars Among GB/FIRST Flat-Spectrum Radio Sources
• High-redshift QSOs in the FIRST survey
• A sample of radio-loud QSOs at redshift ~ 4

Cited by in corpus (6)

• Unusual quasars from the Sloan Digital Sky Survey selected by means of Kohonen self-organising maps
• Radio-Selected Quasars in the Sloan Digital Sky Survey
• Redshifted intergalactic 3He+ 8.7 GHz hyperfine absorption
• Use of neural networks for the identification of new z>=3.6 QSOs from FIRST-SDSS DR5
• Neural-network selection of high-redshift radio quasars, and the luminosity function at z~4
• The optical luminosity function of LOFAR radio-selected quasars at $1.4\le z\le 5.0$ in the NDWFS-Boötes field