A search for edge-on galaxy lenses in the CFHT Legacy Survey*
CNRS, UMR7095, Institut d'Astrophysique de Paris, 75014 Paris, France e-mail: [sygnet;fort;gavazzi]@iap.fr
2 UPMC Univ Paris 06, UMR7095, Institut d'Astrophysique de Paris, 75014 Paris, France
3 Physics Department & Shanghai Key Lab for Astrophysics, Shanghai Normal University, Shanghai 200234, PR China e-mail: TuHong@shnu.edu.cn
Accepted: 18 April 2010
Context. The new generation of wide-field optical imaging as the Canada France Hawaii Telescope Legacy Survey (CFHTLS) enables discoveries of all types of gravitational lenses present in the sky. The Strong Lensing Legacy Survey (SL2S) project has started an inventory of clusters or groups of galaxies lenses and of Einstein rings around distant massive ellipticals.
Aims. Here we attempt to extend this inventory by finding lensing events produced by massive edge-on disk galaxies that remain a poorly documented class of lenses.
Methods. We implemented and tested an automated search procedure of edge-on galaxy lenses in the CFHTLS Wide fields with magnitude 18<i<21, inclination angle lower than , and a photometric redshift determination. This procedure estimated the lensing convergence of each galaxy from the Tully-Fisher law and selected only those few candidates that exhibit a possibly nearby arc configuration at a radius compatible with this convergence ( ≲ 2 ). The efficiency of the procedure was tested after a visual examination of the whole initial sample of 30 444 individual edge-on disks.
Results. After calculating the surface density of edge-on lenses possibly detected in a survey for a given seeing, we deduce that this theoretical number is about 10 for the CFHTLS Wide, a number in broad agreement with the 2 good candidates detected here. We show that the Tully-Fisher selection method is very efficient at finding valuable candidates, though its accuracy depends on the quality of the photometric redshift of the lenses. Finally, we argue that future surveys will detect at least a hundred of such lens candidates.
Key words: gravitational lensing: strong / dark matter / galaxies: spiral / galaxies: halos
Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.
© ESO, 2010