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Strong Lensing in RCS-2 Clusters

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

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Strong Lensing in RCS-2 Clusters

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  1. Great Lakes Cosmology Workshop 8 – June 2, 2007 Strong Lensing in RCS-2 Clusters Matt Bayliss University of Chicago Department of Astronomy & Astrophysics 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. • 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. • Mass Measurement + Mass Profile • Unique window into small scale Dark Matter Distribution • Radial distribution of arcs from cluster cores • Azimuthal angle covered by giant arcs • Large samples of giant arcs open the door for statistical studies of lens and source properties • Distributions of lens properties (with redshift) • Statistically characterize hundreds of high-z lensed sources

  4. RCS-2 Lenses – A Quick Tour:

  5. RCS-2 Lensing Tour continued

  6. 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.

  7. 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) • So our “giant arcs” are, in fact, reasonably giant • Median redshift = 0.549 • 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: σ8, deeper SB limit and filter color • Hilbert et al: low-z, high mass population of lenses predicted.

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

  9. RCS-2 Lenses – Mass-Redshift Distribution

  10. Things That Get You Space Telescope Time • 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 σ1D 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

  11. NICMOS F160W 1 2 3

  12. Object of Interest - Preliminary Analysis 1 2 3

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

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

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