@article{10902/27626,
year = {2006},
month = {9},
url = {https://hdl.handle.net/10902/27626},
abstract = {We selected from the VLA FIRST survey a sample of 94 objects with star-like counterparts in the Sloan Digital Sky Survey (SDSS), and with APM POSS-I colour 0 - E  2, i.e. consistent with their being high-redshift quasars. 78 of the 94 candidates can be classified spectroscopically on the basis of either published data (mainly SDSS) or the observations presented here. The fractions of QSOs (51 out of 78) and redshift z > 3 QSOs (23 out of 78, 29 per cent) are comparable to those found in other photometric searches for high-redshift QSOs. We confirm that selecting colour 0 - E  2 ensures inclusion of all QSOs with 3.7 ? z ? 4.4. The fraction of 2  z ? 4.4 QSOs with broad absorption lines (BALs) is 27 ± 10 per cent (7/26) and the estimated BAL fraction for radio-loud QSOs is at least as high as for optically selected QSOs (? 13 per cent). Both the high BAL fraction and the high fraction of low-ionization BALs among BALs (four to five out of seven) in our sample, compared to previous work, are likely due to the red colour selection 0 - E ? 2. The space density of radio-loud QSOs in the range 3.7 ? z ? 4.4 (z = 4.0) with MAB(1450) ? -26.6 and P  10 25.7 WHz-1 is 1.7 ± 0.6 Gpc-3. Adopting a radio-loud fraction of 13.4 ±3 per cent, this corresponds to p = 12.5 ± 5.6 Gpc-3, in substantial agreement with the cumulative luminosity function of SDSS QSOs in Fan et al. We note the unusual flat-spectrum radio-luminous QSO FIRST 141344505 (z = 3.11), which shows strong associated Ly absorption (rest-frame equivalent width 40 Å) and an extreme observed luminosity, L  2 × 1015 L},
organization = {ACKNOWLEDGMENTS We thank the referee for rapid and helpful feedback. RC, JIG-S, CRB and MV acknowledge financial support from the Spanish Ministerio de Educaci´on y Ciencia under project AYA 2002−03326. This research is in part based on observations made with the Italian TNG operated on the island of La Palma by the Fundaci´on Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Funding for the creation and distribution of the SDSS Archive has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the US Department of Energy, the Japanese Monbukagakusho and the Max Planck Society. The SDSS Web site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium (ARC) for the Participating Institutions. The Participating Institutions are The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Korean Scientist Group, Los Alamos National Laboratory, the MaxPlanck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. This research has made use of the NED which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The 2MASS project is a collaboration between The University of Massachusetts and the Infrared Processing and Analysis Center (JPL/Caltech). Funding is provided primarily by NASA and the NSF. The University of Massachusetts constructed and maintained the observatory facilities, and operated the survey.},
publisher = {Oxford University Press},
publisher = {Monthly Notices of the Royal Astronomical Society, 2006, 370 (2), 1034 - 1045},
title = {A FIRST-APM-SDSS survey for high-redshift radio QSOs},
author = {Carballo Fidalgo, Ruth and González Serrano, José Ignacio and Montenegro-Montes, F.M. and Benn, C.R. and Mack, K.-H. and Pedani, M. and Vigotti, M.},
}