Cosmic shear analysis with CFHTLS deep data

¹ Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France e-mail: sembolon@iap.fr
² Observatoire de Paris, LERMA, 61 avenue de l'Observatoire, 75014 Paris, France
³ University of British Columbia, Department of Physics and Astronomy, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1, Canada
⁴ Department of Physics and Astronomy, University of Victoria, Victoria, B.C. V8P 5C2, Canada
⁵ Departamento de Fisica, Universidade de Lisboa, 1749-016 Lisboa, Portugal
⁶ Department of Physics, University of Waterloo, Waterloo ON N2L 3G1, Canada
⁷ Department of Physics, University La Sapienza, Pl. A. Moro 2, 00185, Roma, Italy

Received: 5 November 2005
Accepted: 31 January 2006

Abstract

We present the first cosmic shear measurements obtained from the T0001 release of the Canada-France-Hawaii Telescope Legacy Survey. The data set covers three uncorrelated patches (D1, D3 and D4) of one square degree each, observed in u^*, g', r', i' and z' bands, to a depth of . The deep, multi-colour observations in these fields allow for several data-quality controls. The lensing signal is detected in both r' and i' bands and shows similar amplitude and slope in both filters. B-modes are found to be statistically zero at all scales. Using multi-colour information, we derived a photometric redshift for each galaxy and use this to separate the background source sample into low-z and high-z subsamples. A stronger shear signal is detected from the high-z subsample than from the low-z subsample, as expected from weak lensing tomography. While further work is needed to model the effects of errors in the photometric redshifts, this result suggests that it will be possible to obtain constraints on the growth of dark matter fluctuations with lensing wide field surveys. The combined Deep and Wide surveys give assuming the Peacock & Dodds non-linear scheme (P&D), and for the halo model and . We assumed a Cold Dark Matter model with flat geometry and have marginalized over the systematics, the Hubble constant and redshift uncertainties. Using data from the Deep survey, the upper bound for w₀, the constant equation of state parameter is .