Weighing the giants – IV. Cosmology and neutrino mass

Abstract

We employ robust weak gravitational lensing measurements to improve\ncosmological constraints from measurements of the galaxy cluster mass function\nand its evolution, using X-ray selected clusters detected in the ROSAT All-Sky\nSurvey. Our lensing analysis constrains the absolute mass scale of such\nclusters at the 8 per cent level, including both statistical and systematic\nuncertainties. Combining it with the survey data and X-ray follow-up\nobservations, we find a tight constraint on a combination of the mean matter\ndensity and late-time normalization of the matter power spectrum,\n$\\sigma_8(\\Omega_m/0.3)^{0.17}=0.81\\pm0.03$, with marginalized, one-dimensional\nconstraints of $\\Omega_m=0.26\\pm0.03$ and $\\sigma_8=0.83\\pm0.04$. For these two\nparameters, this represents a factor of two improvement in precision with\nrespect to previous work, primarily due to the reduced systematic uncertainty\nin the absolute mass calibration provided by the lensing analysis. Our new\nresults are in good agreement with constraints from cosmic microwave background\n(CMB) data, both WMAP and Planck (plus WMAP polarization), under the assumption\nof a flat $\\Lambda$CDM cosmology with minimal neutrino mass. Consequently, we\nfind no evidence for non-minimal neutrino mass from the combination of cluster\ndata with CMB, supernova and baryon acoustic oscillation measurements,\nregardless of which all-sky CMB data set is used (and independent of the recent\nclaimed detection of B-modes on degree scales). We also present improved\nconstraints on models of dark energy (both constant and evolving),\nmodifications of gravity, and primordial non-Gaussianity. Assuming flatness,\nthe constraints for a constant dark energy equation of state from the cluster\ndata alone are at the 15 per cent level, improving to $\\sim 6$ per cent when\nthe cluster data are combined with other leading probes.\n