SIMBAD references

We present the first measurement of the mass function of galaxy clusters based directly on cluster masses derived from observations of weak gravitational lensing. To investigate the degree of sample incompleteness resulting from the X-ray-based selection of the target clusters, we use a sample of 50 clusters with weak-lensing mass measurements to empirically determine the relation between lensing mass and X-ray luminosity and the scatter about this relation. We use a complete, volume-limited subsample of 35 X-ray-luminous clusters of galaxies at 0.15<z<0.3 to constrain the abundance of very massive (M≳10¹⁵ h^–1 M_☉) clusters. From this, we constrain σ₈(Ω_m/0.3)^0.37=0.67^+0.04_–0.05 (68% confidence limits), agreeing well with constraints from the 3 year WMAP CMB measurements and estimates of cluster abundances based on X-ray observations, but somewhat lower than constraints from ``cosmic shear'' weak-lensing measurements in random fields.