A Caltech Library Service

The Cosmic Lens All-Sky Survey - I. Source selection and observations

Myers, S. T. and Jackson, N. J. and Browne, I. W. A. and de Bruyn, A. G. and Pearson, T. J. and Readhead, A. C. S. and Wilkinson, P. N. and Biggs, A. D. and Blandford, R. D. and Fassnacht, C. D. and Koopmans, L. V. E. and Marlow, D. R. and McKean, J. P. and Norbury, M. A. and Phillips, P. M. and Rusin, D. and Shepherd, M. C. and Sykes, C. M. (2003) The Cosmic Lens All-Sky Survey - I. Source selection and observations. Monthly Notices of the Royal Astronomical Society, 341 (1). pp. 1-12. ISSN 0035-8711.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


The Cosmic Lens All-Sky Survey (CLASS) is an international collaborative programme which has obtained high-resolution radio images of over 10 000 flat-spectrum radio sources in order to create the largest and best-studied statistical sample of radio-loud gravitationally lensed systems. With this survey, combined with detailed studies of the lenses found therein, constraints can be placed on the expansion rate, matter density and dark energy (e.g. cosmological constant, quintessence) content of the Universe that are complementary to and independent of those obtained through other methods. CLASS is aimed at identifying lenses where multiple images are formed from compact flat-spectrum radio sources, which should be easily identifiable in the radio maps. Because CLASS is radio-based, dust obscuration in lensing galaxies is not a factor, and the relative insensitivity of the instrument to environmental conditions (e.g. weather, ‘seeing’) leads to nearly uniform sensitivity and resolution over the entire survey. In four observing ‘seasons’ from 1994 to 1999, CLASS has observed 13 783 radio sources with the Very Large Array (VLA) at 8.4 GHz in its largest ‘A’-configuration (0.2-arcsec resolution). When combined with the Jodrell Bank VLA Astrometric Survey (JVAS), the CLASS sample contains over 16 000 images. A complete sample of 11 685 sources was observed, selected to have a flux density of at least 30 mJy in the Green Bank Survey (GB6) catalogue at 4.85 GHz (spanning the declination range 0° ⩽ δ ⩽ 75° and |b| ⩾ 10°, excluding the Galactic plane) and a spectral index α ⩾ −0.5 between the NRAO-VLA Sky Survey (NVSS) at 1.4 GHz and the GB6. A typical 30-s CLASS snapshot reached an rms noise level of 0.4 mJy. So far, CLASS has found 16 new gravitational lens systems, and the JVAS/CLASS survey contains a total of 22 lenses. The follow-up of a small number of candidates using the VLA, MERLIN, the Very Long Baseline Array (VLBA) and optical telescopes is still underway. In this paper, we present a summary of the CLASS observations, the JVAS/CLASS sample, and statistics on sub-samples of the survey. An accompanying paper presents the lens candidate selection, and in a third paper the implications for cosmology are discussed.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Pearson, T. J.0000-0001-5213-6231
Readhead, A. C. S.0000-0001-9152-961X
Biggs, A. D.0000-0002-1117-9961
Blandford, R. D.0000-0002-1854-5506
Fassnacht, C. D.0000-0002-4030-5461
Koopmans, L. V. E.0000-0003-1840-0312
Additional Information:© 2003 RAS. Accepted 2002 November 1. Received 2002 October 23; in original form 2002 July 10. STM was supported by a R. A. Millikan Fellowship while at Caltech from 1992 to 1995, and by an Alfred P. Sloan Fellowship at the University of Pennsylvania. The CLASS survey at Caltech was supported by NSF grant AST-9117100, and RDB acknowledges the additional support of NSF AST-9529170, AST-9900866 and NASA NAG 5-7007. This research was supported in part by the European Commission TMR Programme, Research Network Contract ERBFMRXCT96-0034 ‘CERES’. The National Radio Astronomy Observatory is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation. Finally, but not least, we thank the staff of the VLA for their assistance during our observing runs, and for providing the instruments that made this work possible.
Funding AgencyGrant Number
Robert A. Millikan FellowshipUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
NASANAG 5-7007
Marie Curie FellowshipERBFMRXCT96-0034
Subject Keywords:gravitational lensing, cosmology: observations
Issue or Number:1
Record Number:CaltechAUTHORS:20190523-125437645
Persistent URL:
Official Citation:S. T. Myers, N. J. Jackson, I. W. A. Browne, A. G. de Bruyn, T. J. Pearson, A. C. S. Readhead, P. N. Wilkinson, A. D. Biggs, R. D. Blandford, C. D. Fassnacht, L. V. E. Koopmans, D. R. Marlow, J. P. McKean, M. A. Norbury, P. M. Phillips, D. Rusin, M. C. Shepherd, C. M. Sykes, The Cosmic Lens All-Sky Survey - I. Source selection and observations, Monthly Notices of the Royal Astronomical Society, Volume 341, Issue 1, 1 May 2003, Pages 1–12,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95744
Deposited By: George Porter
Deposited On:23 May 2019 23:15
Last Modified:03 Oct 2019 21:16

Repository Staff Only: item control page