We use the abundance and weak lensing mass measurements of the SDSS maxBCG cluster catalog to simultaneously constrain cosmology and the richness--mass relation of the clusters. Assuming a flat \LambdaCDM cosmology, we find \sigma_8(\Omega_m/0.25)^{0.41} = 0.832\pm 0.033 after marginalization over all systematics. In common with previous studies, our error budget is dominated by systematic uncertainties, the primary two being the absolute mass scale of the weak lensing masses of the maxBCG clusters, and uncertainty in the scatter of the richness--mass relation. Our constraints are fully consistent with the WMAP five-year data, and in a joint analysis we find \sigma_8=0.807\pm 0.020 and \Omega_m=0.265\pm 0.016, an improvement of nearly a factor of two relative to WMAP5 alone. Our results are also in excellent agreement with and comparable in precision to the latest cosmological constraints from X-ray cluster abundances. The remarkable consistency among these results demonstrates that cluster abundance constraints are not only tight but also robust, and highlight the power of optically-selected cluster samples to produce precision constraints on cosmological parameters.
@article{arxiv.0902.3702,
title = {Cosmological Constraints from the SDSS maxBCG Cluster Catalog},
author = {Eduardo Rozo and Risa H. Wechsler and Eli S. Rykoff and James T. Annis and Matthew R. Becker and August E. Evrard and Joshua A. Frieman and Sarah M. Hansen and Jiangang Hao and David E. Johnston and Benjamin P. Koester and Timothy A. McKay and Erin S. Sheldon and David H. Weinberg},
journal= {arXiv preprint arXiv:0902.3702},
year = {2010}
}