Joint Astrophysics Colloquium

Strong Lensing by Optically-Selected Galaxy Clusters

Mike Gladders

Department of Astronomy and Astrophysics
University of Chicago

Gravitational lensing by galaxy clusters was predicted in the 1930s, and finally discovered in 1986. Since these initial discoveries, several dozen significant cluster lenses have been discovered in a variety of ways. 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 rather 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 expect to find hundreds of new giant arcs. These efforts are now approximately half-complete; in this mid-course report I will report on some of the spectacular successes of these studies, and the remaining challenges. Time permitting, I will also discuss a recently commissioned instrument at the Magellan telescopes which was designed specifically for studying these new lens samples.