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Cosmic Shear with HST Jason Rhodes, JPL Galaxies and Structures Through Cosmic Times Venice Italy

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

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Cosmic Shear with HST Jason Rhodes, JPL Galaxies and Structures Through Cosmic Times Venice Italy

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  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. Weak Gravitational Lensing zlens≈0.3–0.5 Weak lensing effect cannot be measured from any individual galaxy. Must be measured statistically over many galaxies zgalaxy≈1 zobserver=0 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.

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

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

  6. 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

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

  8. TinyTim- The PSF Solution

  9. Parametric CTE Correction

  10. Shear-shear correlation functions

  11. E-B mode split

  12. Redshift tomography

  13. Redshift tomography z>1.5 1.1<z<1.5 0.8<z<1.1 0.4<z<0.8

  14. Cosmological parameter constraints 8 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 w w Ωm Courtesy Joel Bergé

  15. Combined Errors

  16. Complementary Error bars

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