Cosmic shear from STIS pure parallels^*

II. Analysis

¹ Institut für Astrophysik und Extraterrestrische Forschung der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
² Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Str. 1, 85748 Garching, Germany
³ ST-ECF, Karl-Schwarzschild Str. 2, 85748 Garching, Germany
⁴ Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
⁵ Observatoire de Paris, DEMIRM 61, Avenue de l'Observatoire, 75014 Paris, France
⁶ Departement of Physics and Astronomy, University of Pennsylvania 209 S. 33rd Street, Philadelphia, PA 19104, USA

Corresponding author: H. Hämmerle, hanne@astro.uni-bonn.de

Received: 10 October 2001
Accepted: 31 January 2002

Abstract

We report on the marginal detection of cosmic shear on sub-arcmin scales with archive data from the STIS camera on board HST. For the measurement 121 galaxy fields with a field of view of are used to obtain an rms cosmic shear of ~4% with significance. This value is consistent with groundbased results obtained by other groups on larger scales, and with theoretical predictions for a standard ΛCDM cosmology. To show the suitability of STIS for weak shear measurements we carefully investigated the stability of the PSF. We demonstrate that small temporal changes do not affect the cosmic shear measurement by more than ~10%. We also discuss the influence of various weighting and selection schemes for the galaxy ellipticities.