1. Cosmic Shear with HST Jason Rhodes, JPL Galaxies and Structures Through Cosmic Times Venice Italy March 27, 2006 with Richard Massey, Catherine Heymans & Alexie Leauthaud The COSMOS Lensing Team: Jean-Paul Kneib, Justin Albert, David Bacon, Joel Berge, Richard Ellis, Cécile Faure, Anton Koekemoer, Yannick Mellier, Satoshi Miyazaki, John Peacock, Alexandre Refregier, Nick Scoville, Elisabetta Semboloni, Lidia Tasca, James Taylor, Ludovic Van Waerbeke The ACS Parallel team: Jon Gardner & Nicholas Collins

2. 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

3. How Gravitational Lensing Works Statistical measurement on many galaxies Lensing induced ellipticities 1-2% Telescope Point Spread Function (PSF) is the primary systematic concern –it changes e! Assume galaxy shears are intrinsically uncorrelated Need to measure shear quite accurately

4. E and B modes

5. Patterns in a shear field Clusters are patterns in a shear field:

6. HST Surveys With ACS GEMS UDF GOODS COSMOS ACS Parallel Survey

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

8. The PSF Problems PSF time variability CTE degradation See Rhodes et al 2006, astro-ph/0512170

9. TinyTim- The PSF Solution

10. Parametric CTE Correction

11. Shear-shear correlation functions

12. E-B mode split

13. Redshift tomography

14. 0.4<z<0.8 0.8<z<1.1 1.1<z<1.5 z>1.5

15. Cosmological parameter constraints Courtesy Joel Berg é 88 ΩmΩm w w -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

16. Combined Errors

17. Complementary Error bars