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The Cosmic Lens All-Sky Survey - II. Gravitational lens candidate selection and follow-up

Browne, I. W. A. and Wilkinson, P. N. and Jackson, N. J. F. and Myers, S. T. and Fassnacht, C. D. and Koopmans, L. V. E. and Marlow, D. R. and Norbury, M. and Rusin, D. and Sykes, C. M. and Biggs, A. D. and Blandford, R. D. and de Bruyn, A. G. and Chae, K.-H. and Helbig, P. and King, L. J. and McKean, J. P. and Pearson, T. J. and Phillips, P. M. and Readhead, A. C. S. and Xanthopoulos, E. and York, T. (2003) The Cosmic Lens All-Sky Survey - II. Gravitational lens candidate selection and follow-up. Monthly Notices of the Royal Astronomical Society, 341 (1). pp. 13-32. ISSN 0035-8711. doi:10.1046/j.1365-8711.2003.06257.x.

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We report the final results of the search for gravitationally lensed flat-spectrum radio sources found in the combination of CLASS (Cosmic Lens All-Sky Survey) and JVAS (Jodrell Bank VLA Astrometric Survey). VLA (Very Large Array) observations of 16 503 sources have been made, resulting in the largest sample of arcsec-scale lens systems available. Contained within the 16 503 sources is a complete sample of 11 685 sources which have two-point spectral indices between 1.4 and 5 GHz flatter than −0.5, and 5-GHz flux densities ⩾30 mJy. A subset of 8958 sources form a well-defined statistical sample suitable for analysis of the lens statistics. We describe the systematic process by which 149 candidate lensed sources were picked from the statistical sample on the basis of possessing multiple compact components in the 0.2-arcsec resolution VLA maps. Candidates were followed up with 0.05-arcsec resolution MERLIN and 0.003-arcsec VLBA observations at 5 GHz and rejected as lens systems if they failed well-defined surface brightness and/or morphological tests. To illustrate the candidate elimination process, we show examples of sources representative of particular morphologies that have been ruled out by the follow-up observations. 194 additional candidates, not in the well-defined sample, were also followed up. Maps for all the candidates can be found on the World Wide Web at We summarize the properties of each of the 22 gravitational lens systems in JVAS/CLASS. 12 are double-image systems, nine are four-image systems and one is a six-image system. 13 constitute a statistically well-defined sample giving a point-source lensing rate of 1:690 ± 190. The interpretation of the results in terms of the properties of the lensing galaxy population and cosmological parameters will be published elsewhere.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Fassnacht, C. D.0000-0002-4030-5461
Koopmans, L. V. E.0000-0003-1840-0312
Biggs, A. D.0000-0002-1117-9961
Blandford, R. D.0000-0002-1854-5506
Pearson, T. J.0000-0001-5213-6231
Readhead, A. C. S.0000-0001-9152-961X
Alternate Title:The Cosmic Lens All-Sky Survey:II. Gravitational lens candidate selection and follow-up
Additional Information:© 2003 RAS. Accepted 2002 November 1. Received 2002 October 23; in original form 2002 July 10. We thank Shude Mao for many insightful discussions. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Incorporated. MERLIN is operated by the University of Manchester as a National Facility of the Particle Physics & Astronomy Research Council. This work was supported by the European Commission, TMR Programme, Research Network Contract ERBFMRXCT96-0034 ‘CERES’. This research has made use of the NASA/IPAC Extragalactic Data base (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Funding AgencyGrant Number
Marie Curie FellowshipERBFMRXCT96-0034
Subject Keywords:gravitation, gravitational lensing, radio continuum: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20190523-125437758
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Official Citation:I. W. A. Browne, P. N. Wilkinson, N. J. F. Jackson, S. T. Myers, C. D. Fassnacht, L. V. E. Koopmans, D. R. Marlow, M. Norbury, D. Rusin, C. M. Sykes, A. D. Biggs, R. D. Blandford, A. G. de Bruyn, K.-H. Chae, P. Helbig, L. J. King, J. P. McKean, T. J. Pearson, P. M. Phillips, A. C. S. Readhead, E. Xanthopoulos, T. York, The Cosmic Lens All-Sky Survey - II. Gravitational lens candidate selection and follow-up, Monthly Notices of the Royal Astronomical Society, Volume 341, Issue 1, 1 May 2003, Pages 13–32,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95745
Deposited By: George Porter
Deposited On:23 May 2019 23:19
Last Modified:19 Jan 2023 00:38

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