Weak Lensing Results from GEMS

Heymans, Catherine; Brown, Michael L.; Barden, Marco;Caldwell, John A. R.; Jahnke, Knud; Rix, Hans-Walter;Taylor, Andy N.; Beckwith, Steve; Bell, Eric;Borch, Andrea; Häußler, Boris; Jogee, Sharda;McIntosh, Daniel H.; Meisenheimer, Klaus; Peng, Chen;Sánchez, Sebastian F.; Somerville, Rachel;Wisotzki, Lutz; Wolf, Christian. Weak Lensing Results from GEMS. Gravitational Lensing Impact on Cosmology, IAU Symposium. 2005, Vol. vol. 225. Edited by Yannick Mellier and Georges Meylan, ISBN 0521851963. Cambridge, UK: Cambridge University Press, 2005., p.43-48, p. -2005.

We present our cosmic shear analysis of the Galaxy Evolution from Morphology and SEDs (GEMS) survey. Imaged with the Advanced Camera for Surveys (ACS) on HST, GEMS provides high resolution imaging spanning some 800 square arcmins in the Chandra Deep Field South (CDFS). We discuss the benefits of using space-based data for weak lensing studies and show that the ACS is a very powerful instrument in this regard. We find that we are not limited by systematic errors arising from the anisotropic ACS point spread function distortion and use our cosmic shear results to place joint constraints on the matter density parameter Ωm and the amplitude of the matter power spectrum σ8, finding σ8(Ωm/0.3)0.62=0.73 ± 0.12.