Jason Rhodes, JPL 207 th AAS Meeting, January 10, 2006 Nick Scoville, COSMOS PI COSMOS Lensing Team: Jean-Paul Kneib, Jason Rhodes, Justin Albert, David Bacon, Joel Berge, Richard Ellis, Cécile Faure, Catherine Heymans, Anton Koekemoer, Alexie Leauthaud, Richard Massey, Yannick Mellier, Satoshi Miyazaki, John Peacock, Alexandre Refregier, Elisabetta Semboloni, Lidia Tasca, James Taylor, Ludovic Van Waerbeke Mapping the Dark Matter with COSMOS

If there is any intervening large-scale structure, light follows the distorted path (exaggerated). Background images are magnified and sheared by ~2%, mapping a circle into an ellipse. Lensing is most effective for mass structures half way between the source and the observer. z observer =0 z galaxy ≈1 z lens ≈0.3–0.5 Weak lensing effect cannot be measured from any individual galaxy. Must be measured statistically over many galaxies Weak Gravitational Lensing

COSMOS For WL 2 square degrees Single orbit F814(I) ACS images ~80 resolved galaxies per square arcmin versus ~30 from the ground Unique combination of area, depth and resolution Opens door for unprecedented dark matter maps

The PSF Problems PSF time variability output image size CTE degradation See Rhodes et al 2006, astro-ph/

The Dark Matter Distribtuion Created with method of Kaiser and Squires (1993) Wavelet reconstruction will do better

E/B Decompsosition Conclusions- the detections are real and B modes are decreasing as we improve our PSF models

Mass and Light Contours are from 1-20x(7.5x10 3 gal per sq deg)