Strong Lensing Legacy Survey

It may not be our most impressive, but this is the first one that we discovered using fully automated software methods...

The SL2S survey is a search dedicated to strong gravitational lenses in the CFHTLS survey.  The CHFTLS has a great potential for strong gravitational lenses. This deep and accurate survey contains about 1 gravitational arc per square degree. The CHFTLS "wide"  survey will cover a surface of about 170 square degrees on the sky, this survey  in the  (u*, g', r', i', z') photometric bands, down to the magnitude i'=24.5. Please see the CFHTLS Home Page for more details.

 Ultimately, hundreds of highly distorded images of distant galaxies should be identified in the CFHTLS "wide" sky survey. In some cases the  images produced by strong lenses looks like arcs or arclets in the images, these images are of particular interest since  they can  be  identified  according to their particular shape. See this  HST image of Abell 2218 for a nice illustration.  The arcs  are produced when the source is near a caustic which is a singularity in the mapping introduced by the lens.  More information about the arcs  observed in the CFHTLS survey and the SL2S project is available in the transcript of the talk given at the CFHTLS users meeting: CFHTLS meeting presentation .  At the present time a total of about 40 arcs candidates have been found using an automated software running on  sky region 30 square degree ( see  astro-ph/0606757 for a description of the method).