2008MNRAS.384.1567M

Using a uniform analysis procedure, we measure spatially resolved weak gravitational lensing and hydrostatic X-ray masses for a sample of 18 clusters of galaxies. We find a radial trend in the X-ray to lensing mass ratio: at r₂₅₀₀, we obtain a ratio M_X/M_L= 1.03±0.07 which decreases to M_X/M_L= 0.78±0.09 at r₅₀₀. This difference is significant at 3σ once we account for correlations between the measurements. We show that correcting the lensing mass for excess correlated structure outside the virial radius slightly reduces, but does not eliminate this trend. An X-ray mass underestimate, perhaps due to non-thermal pressure support, can explain the residual trend. The trend is not correlated with the presence or absence of a cool core. We also examine the cluster gas fraction f_gas and find no correlation with M_L, an important result for techniques that aim to determine cosmological parameters using f_gas.