A measurement of weak lensing by large-scale structure in red-sequence cluster survey fields

We have analyzed similar to24 deg(2) of R-C-band imaging data from the Red-Sequence Cluster Survey (RCS) and measured the excess correlations between galaxy ellipticities on scales ranging from 1' to 30'. We have used data from two different telescopes: similar to16.4 deg(2) of Canada-France-Hawaii Telescope data and similar to7.6 deg(2) of Cerro Tololo Inter-American Observatory 4 m data, distributed over 13 widely separated patches. For the first time, a direct comparison can be made of the lensing signal measured using different instruments, which provides an important test of the weak-lensing analysis itself. The measurements obtained from the two telescopes agree well. For the lensing analysis, we use galaxies down to a limiting magnitude of R-C = 24, for which the redshift distribution is known relatively well. This allows us to constrain some cosmological parameters. For the currently favored LambdaCDM model (Omega(m) = 0.3, Omega(Lambda) = 0.7, Gamma = 0.21), we obtain sigma8 = 0.81(-0.19)(+0.14) (95% condence), in agreement with the 2001 results from Van Waerbeke and coworkers, who used fainter galaxies (and consequently higher redshift galaxies). The good agreement between these two very different weak-lensing studies demonstrates that weak lensing is a useful tool in observational cosmology.