The Red-Sequence Cluster Survey: first lensing results

Abstract

The Red-Sequence Cluster Survey (RCS) is a 100 deg^2 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 intervening large scale structure (cosmic shear) at high significance, and find σ_8=0.81^{+0.14}_{-0.19} (95% confidence; for a LCDM cosmology. 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 parametrized mass model for the galaxy mass distribution. The analysis yields a mass weighted velocity dispersion of 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). The biasing properties of these galaxies as a function of scale are also studied. The RCS data allow us to measure the ratio of the bias parameter b and the galaxy-mass cross-correlation coefficient r. The results are consistent with a scale-independent value of b/r, for which we find b/r=1.05^{+0.12}_{-0.10}.