EDP Sciences
Free Access
Volume 366, Number 3, February II 2001
Page(s) 717 - 735
Section Cosmology
DOI https://doi.org/10.1051/0004-6361:20010013

A&A 366, 717-735 (2001)
DOI: 10.1051/0004-6361:20010013

How accurately can we measure weak gravitational shear?

T. Erben1, L. Van Waerbeke2, E. Bertin3, 4, Y. Mellier3, 4 and P. Schneider1, 5

1  Max Planck Institut für Astrophysik, Karl-Schwarzschild-Str. 1, Postfach 1317, 85741 Garching, Germany
2  Canadian Institut for Theoretical Astrophysics, 60 St Georges Str., Toronto, M5S 3H8 Ontario, Canada
3  Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
4  Observatoire de Paris, DEMIRM, 61 avenue de l'Observatoire, 75014 Paris, France
5  Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

(Received 29 May 2000 / Accepted 10 November 2000)

With the recent detection of cosmic shear, the most challenging effect of weak gravitational lensing has been observed. The main difficulties for this detection were the need for a large amount of high quality data and the control of systematics during the gravitational shear measurement process, in particular those coming from the Point Spread Function anisotropy. In this paper we perform detailed simulations with the state-of-the-art algorithm developed by Kaiser, Squires and Broadhurst (KSB) to measure gravitational shear. We show that for realistic PSF profiles the KSB algorithm can recover any shear amplitude in the range $0.012 < \vert\gamma \vert< 0.32$ with a relative, systematic error of $10{-}15\%$. We give quantitative limits on the PSF correction method as a function of shear strength, object size, signal-to-noise and PSF anisotropy amplitude, and we provide an automatic procedure to get a reliable object catalog for shear measurements out of the raw images.

Key words: cosmology: theory, gravitational lenses

Offprint request: T. Erben, erben@mpa-garching.mpg.de

© ESO 2001