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

By I. Browne, P. Wilkinson, N. Jackson, S. Myers, C. Fassnacht, Leon V. E. Koopmans, D. R. Marlow, M. Norbury, D. Rusin, C. Sykes and 12 more. 2002

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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 http://www.jb.man.ac.uk/research/gravlens/index.html. 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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2007b1bb5ea36cd67f2fa594f5e38ddcfc5ceb71

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Citations in the corpus

CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources (2007, background): “The primary purpose of the CLASS survey was to discover gravitational lenses, and 22 were found in the 12,000 sources observed (Browne et al. 2003).”
HerMES: CANDIDATE GRAVITATIONALLY LENSED GALAXIES AND LENSING STATISTICS AT SUBMILLIMETER WAVELENGTHS (2012, background): “For example, at radio wavelengths ∼ 0.2% of the initial targets of CLASS are lensed (Browne et al. 2003), although this can be improved to ∼ 2% by including SDSS information in the initial target selection (Jackson & Browne 2007).”
THE FIRST CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE (2010, background): “The prefix “CLASS” refers to sources from the Cosmic Lens All-Sky Survey (Myers et al. 2003; Browne et al. 2003).”
Gravitationally lensed quasars and supernovae in future wide-field optical imaging surveys (2010, background): “We note that the lensing rate is lower than observed in the Cosmic Lens All-Sky Survey (CLASS), ∼10−2.8 (Browne et al. 2003), presumably because of the quite different magnification bias it involves (for instance, in the CLASS the total magnification factor is used for the magnification bias).”
The Supernova Legacy Survey: Measurement of Omega_M, Omega_Lambda,and w from the First Year Data Set (2005, background): “…proved to be rare: the occurrence of multiple images sep- arated by more than 0.3′′ and with flux ratio below 10:1 was found to be of 1 out of 690 with 1.44 secondary image on aver- age, with inefficiencies due to the separation and flux ratio cuts of 13% and 37% respectively (Browne et al. 2003).”
Astrophysical and cosmological information from large-scale submillimetre surveys of extragalactic sources (2007, methodology): “For comparison, the radio Cosmic Lens All-Sky Survey (CLASS; Browne et al. 2003; Myers et al. 2003), that has been the basis for most analyses of lens statistics, has yielded a sample of 22 gravitational lens systems.”
H0LiCOW – I. H0 Lenses in COSMOGRAIL's wellspring: program overview (2016, background): “The lens system was discovered in the Cosmic Lens All-Sky Survey (CLASS; Myers et al. 1995; Browne et al. 2003; Myers et al. 2003).”
GRAVITATIONAL LENS MODELS BASED ON SUBMILLIMETER ARRAY IMAGING OF HERSCHEL-SELECTED STRONGLY LENSED SUB-MILLIMETER GALAXIES AT z > 1.5 (2013, methodology): “The left panel of Figure 4 shows these values for the objects in the SMA subsample with robust lens models and compares them to other strong lenses found in SLACS (Bolton et al. 2008), BELLS (Brownstein et al. 2012), CASTLeS (Muñoz et al. 1998), and CLASS (Myers et al. 2003; Browne et al. 2003).”
DISSECTING THE GRAVITATIONAL LENS B1608+656. II. PRECISION MEASUREMENTS OF THE HUBBLE CONSTANT, SPATIAL CURVATURE, AND THE DARK ENERGY EQUATION OF STATE (2009, background): “The quadruple-image gravitational lens B1608+656 was discovered in the Cosmic Lens All-Sky Survey (CLASS) (Myers et al. 1995; Browne et al. 2003; Myers et al. 2003).”
Gravitational Lens Time Delays: A Statistical Assessment of Lens Model Dependences and Implications for the Global Hubble Constant (2006, methodology): “While the statistical sample has been very limited so far, containing 20 lenses even for the largest lens sample (Myers et al. 2003; Browne et al. 2003), larger lens surveys will be soon available by ongoing/ future lens surveys such as those done by the Sloan Digital Sky Survey (SDSS) (Oguri et…”