Heidelberg Joint Astronomical Colloquium

Speaker Mike Gladders
Title Bright arcs around optically selected clusters: from a handful to hundreds

Gravitational lensing by galaxy clusters was predicted in the 1930s, and finally discovered in 1980s. Since these initial discoveries, several dozen significant cluster lenses have been found. Lensing clusters probe the distribution of massive haloes in the universe; the expected arc production frequency can be predicted from simulations and compared to existing data. Massive lensing clusters act as 'natural telescopes', providing highly magnified images of background sources which cannot otherwise be studied using the current generation of telescopes. The details of the observed lensing in clusters also probes the internal properties of these massive haloes. Most cluster strong lens studies to date have been limited by the small number and heterogeneous nature of the sample of known lenses (most of which are one-off discoveries). I will report on efforts to take the study of strong lensing clusters to a new statistical regime, by identifying and studying two new samples of strong lenses within large catalogs of optically selected galaxy clusters from the RCS-2 and SDSS surveys; in total we have found hundreds of new giant arcs. These efforts are now approximately three-quarters-complete; in this progress report I will describe some of the successes of these studies, and the remaining challenges.