The Shear Testing Programme - I. Weak lensing analysis of simulated ground-based observations

Catherine Heymans (1) , Ludovic van Waerbeke (2) , David Bacon (3) , Joel Bergé (4) , Gary Bernstein (5) , Emmanuel Bertin (6) , Sarah Bridle (7) , Michael L. Brown (3) , Douglas I. Clowe (8) , Håkon Dahle (9) , Thomas Erben (10) , Meghan Gray (11) , Marco Hetterscheidt (10) , Henk Hoekstra (12) , Patrick Hudelot (13) , Mike Jarvis (5) , Konrad Kuijken (14) , Vera Margoniner (15) , Richard Massey (16) , Yannick Mellier (6, 17) , Reiko Nakajima (5) , Alexandre Réfrégier (4) , Jason D. Rhodes (18) , Tim Schrabback (10) , David Wittman (15)

1 MPIA - Max-Planck-Institut für Astronomie
2 University of British Columbia [Vancouver]
3 Edin. - University of Edinburgh
4 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
5 Department of Physics and Astronomy, University of Pennsylvania
6 IAP - Institut d'Astrophysique de Paris
7 UCL - University College of London [London]
8 Steward Observatory, University of Arizona
9 UiO - University of Oslo
10 IAEF - Institut für Astrophysik und Extraterrestrische Forschung, Universität Bonn
11 UON - University of Nottingham, UK
12 Department of Physics and Astronomy, University of Victoria
13 LATT - Laboratoire Astrophysique de Toulouse-Tarbes
14 Leiden Observatory
15 Department of Physics, Le Conte Hall, University of California
16 Cahill Center for Astronomy and Astrophysics
17 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
18 JPL - Jet Propulsion Laboratory

The Shear Testing Programme (STEP) is a collaborative project to improve the accuracy and reliability of all weak lensing measurements in preparation for the next generation of wide-field surveys. In this first STEP paper, we present the results of a blind analysis of simulated ground-based observations of relatively simple galaxy morphologies. The most successful methods are shown to achieve percent level accuracy. From the cosmic shear pipelines that have been used to constrain cosmology, we find weak lensing shear measured to an accuracy that is within the statistical errors of current weak lensing analyses, with shear measurements accurate to better than 7 per cent. The dominant source of measurement error is shown to arise from calibration uncertainties where the measured shear is over or underestimated by a constant multiplicative factor. This is of concern as calibration errors cannot be detected through standard diagnostic tests. The measured calibration errors appear to result from stellar contamination, false object detection, the shear measurement method itself, selection bias and/or the use of biased weights. Additive systematics (false detections of shear) resulting from residual point-spread function anisotropy are, in most cases, reduced to below an equivalent shear of 0.001, an order of magnitude below cosmic shear distortions on the scales probed by current surveys.

Domaines: Astrophysique [astro-ph]

Catherine Heymans, Ludovic van Waerbeke, David Bacon, Joel Bergé, Gary Bernstein, et al.. The Shear Testing Programme - I. Weak lensing analysis of simulated ground-based observations. Monthly Notices of the Royal Astronomical Society, 2006, 368, pp.1323-1339. ⟨10.1111/j.1365-2966.2006.10198.x⟩. ⟨hal-03786091⟩