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Issue A&A
Volume 374, Number 3, August II 2001
Page(s) 757 - 769
Section Cosmology
DOI http://dx.doi.org/10.1051/0004-6361:20010766



A&A 374, 757-769 (2001)
DOI: 10.1051/0004-6361:20010766

Cosmic shear statistics and cosmology

L. Van Waerbeke1, 2, Y. Mellier1, 3, M. Radovich4, 1, E. Bertin1, 3, M. Dantel-Fort3, H. J. McCracken5, O. Le Fèvre5, S. Foucaud5, J.-C. Cuillandre6, 7, T. Erben1, 3, 8, B. Jain9, 10, P. Schneider11, F. Bernardeau12 and B. Fort1

1  Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
2  Canadian Institut for Theoretical Astrophysics, 60 St Georges Str., Toronto, M5S 3H8 Ontario, Canada
3  Observatoire de Paris, DEMIRM, 61 avenue de l'Observatoire, 75014 Paris, France
4  Osservatorio Astronomico di Capodimonte, via Moiariello, 80131m Napoli, Italy
5  Laboratoire d'Astrophysique de Marseille, 13376 Marseille Cedex 12, France
6  Canada-France-Hawaii-Telescope, PO Box 1597, Kamuela, Hawaii 96743, USA
7  Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France
8  Max Planck Institut für Astrophysiks, Karl-Schwarzschild-Str. 1, Postfach 1523, 85740 Garching, Germany
9  Dept of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
10  Dept. of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
11  Universitaet Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
12  Service de Physique Théorique, CE de Saclay, 91191 Gif-sur-Yvette Cedex, France

(Received 2 February 2001 / Accepted 25 May 2001 )

Abstract
We report a measurement of cosmic shear correlations using an effective area of 6.5 deg2 of the VIRMOS deep imaging survey in progress at the Canada-France-Hawaii Telescope. We measured various shear correlation functions, the aperture mass statistic and the top-hat smoothed variance of the shear with a detection significance exceeding $12 \sigma$. We present results on angular scales from 3 arcsec to half a degree. The lensing origin of the signal is confirmed through tests that rely on the scalar nature of the gravitational potential. The different statistical measures give consistent results over the full range of angular scales. These important tests of the measurements demonstrate that the measured correlations could provide accurate constraints on cosmological parameters, subject to the systematic uncertainty in the source redshift distribution. The measurement over more than two decades of scale allows one to evaluate the effect of the shape of the power spectrum on cosmological parameter estimation. The degeneracy on $\sigma_8-\Omega_0$ can be broken if priors on the shape of the linear power spectrum (parameterized by $\Gamma$) are assumed. For instance, with $\Gamma=0.21$ and at the $95\%$ confidence level, we obtain $0.65< \sigma_8< 1.2$ and $0.22< \Omega_0< 0.55$ for open models, and $\sigma_8> 0.7$ and $\Omega_0< 0.4$ for flat ($\Lambda$-CDM) models. We discuss how these results would scale if the assumed source redshift distribution needed to be modified with forthcoming measurements of photometric redshifts. From the tangential/radial mode decomposition we can set an upper limit on the intrinsic shape alignment, which has recently been suggested as a possible contribution to the lensing signal. Within the error bars, there is no detection of intrinsic shape alignment for scales larger than 1'.


Key words: cosmology: theory -- dark matter -- gravitational lensing -- large-scale structure of the Universe

Offprint request: L. Van Waerbeke, waerbeke@iap.fr

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