LoCuSS: THE SUNYAEV–ZEL'DOVICH EFFECT AND WEAK-LENSING MASS SCALING RELATION

We present the first weak-lensing-based scaling relation between galaxy cluster mass, MWL, and integrated Compton parameter Ysph. Observations of 18 galaxy clusters at z ≃ 0.2 were obtained with the Subaru 8.2 m telescope and the Sunyaev–Zel'dovich Array. The MWL–Ysph scaling relations, measured at Δ = 500, 1000, and 2500 ρc, are consistent in slope and normalization with previous results derived under the assumption of hydrostatic equilibrium (HSE). We find an intrinsic scatter in MWL at fixed Ysph of 20%, larger than both previous measurements of MHSE–Ysph scatter as well as the scatter in true mass at fixed Ysph found in simulations. Moreover, the scatter in our lensing-based scaling relations is morphology dependent, with 30%–40% larger MWL for undisturbed compared to disturbed clusters at the same Ysph at r 500. Further examination suggests that the segregation may be explained by the inability of our spherical lens models to faithfully describe the three-dimensional structure of the clusters, in particular, the structure along the line of sight. We find that the ellipticity of the brightest cluster galaxy, a proxy for halo orientation, correlates well with the offset in mass from the mean scaling relation, which supports this picture. This provides empirical evidence that line-of-sight projection effects are an important systematic uncertainty in lensing-based scaling relations.