First weak lensing results from the Red-Sequence Cluster Survey

Abstract

The Red-Sequence Cluster Survey (RCS) is a 100 square degree galaxy cluster survey designed to provide a large sample of optically selected clusters of galaxies with redshifts 0.1<z<1.4. The survey data are also useful for a variety of lensing studies. Several strong lensing clusters have been discovered so far, and follow up observations are underway. In these proceedings we present some of the first results of a weak lensing analysis based on 24 deg^2 of data. We have detected the lensing signal induced by large scale structure (cosmic shear) at high significance, and find sigma_8=0.79+-0.08 (for a CDM cosmology with Omega_m=0.3,Ω_Λ=0.7, h=0.7). Another application of these data is the study of the average properties of dark matter halos surrounding galaxies. We study the lensing signal from intermediate redshift galaxies with 19.5<R_C<21 using a parameterised mass model for the galaxy mass distribution. The analysis yields a mass weighted velocity dispersion of <sigma^2>^{1/2}= 111+-5 km/s. In addition we have constrained for the first time the extent of dark matter halos, and find a robust upper limit for the truncation parameter s<470 h^{-1} kpc (99.7% confidence). A preliminary analysis also excludes a simple ``prediction&#39;&#39; of lensing according to Modified Newtonian Dynamics (MOND) at high confidence.