1. 1 COSMOS Dark Matter Maps with COSMOS Jason Rhodes (JPL) January 11, 2005 San Diego AAS Meeting 72.05 For the COSMOS WL team : (Justin Albert, Richard Ellis, Alexie Leauthaud, Richard Massey @ Caltech; Jean-Paul Kneib, Yannick Mellier, Alexandre Refregier, Ludovic van Waerbeke in France; Satoshi Miyazaki in Hawaii/Japan)

2. 2 Weak Gravitational Lensing In the absence of large-scale structure, light beams from a galaxy follow the undistorted path. Dark matter bends space and the light follows the distorted path. COSMOS

3. 3 Cosmology with WL Cosmological parameters Ω M & σ 8 can be measured to high precision via WL Dark matter maps with sensitivity down to a few 10 13 solar mass Evolution of structure via redshift tomography Eventually a measure of dark energy (w) via evolution of structure COSMOS will: Measure dark matter density and clustering to better than 10% Produce highest resolution dark matter maps Allow for direct comparisons of mass and light Pave the way for future missions such as SNAP

4. 4 COSMOS COSMOS Number Density After cleaning 50-80 resolved galaxies per square arcminute Final number depends on cuts on size & S/N Still refining correction for PSF effects Compare to ~30 galaxies per square arcminute from ground

5. 5 COSMOS Parameter Space Unique combination of area, depth and resolution Opens door for unprecedented dark matter maps COSMOS

6. 6 COSMOS Mass Map

7. 7 COSMOS Mass Vs. Light Z=0.3-0.5

8. 8 COSMOS Time Dependent PSF The PSF pattern is time dependent

9. 9 Ongoing Work Understand sources of PSF variation (thermal) Understand effects of processing (multidrizzle) on PSF Model PSF using TinyTim Verify PSF using stellar data from COSMOS and external data sets Correct for time-varying PSF COSMOS