1. Strong Lensing in RCS-2 Clusters Matt Bayliss University of Chicago Department of Astronomy & Astrophysics Great Lakes Cosmology Workshop 8 – June 2, 2007 Collaborators: Michael Gladders - University of Chicago Howard Yee and David Gilbank – University of Toronto and the rest of the RCS-2 team.

2. Motivations: Why Strong Lensing? Why Now? Large cluster catalogs popping up –> good time to start looking. Large cluster catalogs popping up –> good time to start looking. Strong Lensing relevant for cluster studies, cosmology and study of background universe. Strong Lensing relevant for cluster studies, cosmology and study of background universe. RCS Lensing Cluster at z = 0.77

3. So What Is It We Want to Measure? Directly Probe the Gravitational Potential. Directly Probe the Gravitational Potential. Mass Measurement + Mass Profile Mass Measurement + Mass Profile Unique window into small scale Dark Matter Distribution Unique window into small scale Dark Matter Distribution Radial distribution of arcs from cluster cores Radial distribution of arcs from cluster cores Azimuthal angle covered by giant arcs Azimuthal angle covered by giant arcs Large samples of giant arcs open the door for statistical studies of lens and source properties Large samples of giant arcs open the door for statistical studies of lens and source properties Distributions of lens properties (with redshift) Distributions of lens properties (with redshift) Statistically characterize hundreds of high-z lensed sources Statistically characterize hundreds of high-z lensed sources

4. RCS-2 Lenses – A Quick Tour:

5. RCS-2 Lensing Tour continued

16. RCS-2 Lenses – Mass-Redshift Distribution Mass calculated by assuming fitted circular radii equal to Einstein Radii for a SIS profile for all cluster lenses, and averaging over a random distribution of source redshifts. Mass calculated by assuming fitted circular radii equal to Einstein Radii for a SIS profile for all cluster lenses, and averaging over a random distribution of source redshifts.

17. RCS-2 Lenses – A Few Statistics Median azimuthal angle covered by giant arcs is 0.459 radians (or ~ 26 degrees, range is 10-60 degrees) Median azimuthal angle covered by giant arcs is 0.459 radians (or ~ 26 degrees, range is 10-60 degrees) So our “giant arcs” are, in fact, reasonably giant So our “giant arcs” are, in fact, reasonably giant Median redshift = 0.549 Median redshift = 0.549 Hennawi et al 2007 predict a median redshift of 0.49 for RCS-1 cluster lenses using simulations Hennawi et al 2007 predict a median redshift of 0.49 for RCS-1 cluster lenses using simulations Hennawi prediction is biased high for RCS-2 comparison: σ 8, deeper SB limit and filter color Hennawi prediction is biased high for RCS-2 comparison: σ 8, deeper SB limit and filter color Hilbert et al: low-z, high mass population of lenses predicted. Hilbert et al: low-z, high mass population of lenses predicted.

18. Strong Lensing Predictions Hennawi et al 2007, astro-ph/0506171 Hilbert et al 2007, astro-ph/0703803

19. RCS-2 Lenses – Mass-Redshift Distribution

20. Things That Get You Space Telescope Time Extremely high mass cluster at z = 0.700, warranting a number of followup observations: Extremely high mass cluster at z = 0.700, warranting a number of followup observations: XMM ~ 1 cnt/s Chandra (coming soon) Magellan Spectroscopy – early-type galaxy σ 1D of 1400 +/- 70 km/s SZA observation: strong source, analysis underway Weak lensing from CFHT mass estimate ~ 3e15 M ๏ Multiple arcs obvious – first spectroscopic confirmation z=3.02, theta_E=49” HST+ACS+NICMOS imaging

21. NICMOS F160W 1 2 3

22. Object of Interest - Preliminary Analysis F435 g r i K Image1 23.98 23.98 23.80 23.80 23.18 23.18 22.91 22.91 18.64 18.64 Image2 23.78 23.78 23.43 23.43 23.08 23.08 22.82 22.82 18.76 18.76 Image3 23.67 23.67 23.62 23.62 23.03 23.03 22.82 22.82 18.68 18.68 1 2 3

23. So What Is This Thing? R – K colors are ~ 4 - 4.2 for the three images R – K colors are ~ 4 - 4.2 for the three images Figure from Szokoly et al, 2004, ApJS..155..271S

24. Where Are We Going? To Las Campanas! To Las Campanas! Additional follow-up observations. Additional follow-up observations. Gemini + HST Gemini + HST Rigorous definition of RCS-2 Strong Lensing Sample Rigorous definition of RCS-2 Strong Lensing Sample Expect ~150 giant arc systems (complete) and similar numbers of galaxy-scale strong lenses (less complete) Expect ~150 giant arc systems (complete) and similar numbers of galaxy-scale strong lenses (less complete)