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

Abstract

We present the first weak-lensing-based scaling relation between galaxy\ncluster mass, M_wl, and integrated Compton parameter Y_sph. Observations of 18\ngalaxy clusters at z~0.2 were obtained with the Subaru 8.2-m telescope and the\nSunyaev-Zel'dovich Array. The M_wl-Y_sph scaling relations, measured at\nDelta=500, 1000, and 2500 rho_c, are consistent in slope and normalization with\nprevious results derived under the assumption of hydrostatic equilibrium (HSE).\nWe find an intrinsic scatter in M_wl at fixed Y_sph of 20%, larger than both\nprevious measurements of M_HSE-Y_sph scatter as well as the scatter in true\nmass at fixed Y_sph found in simulations. Moreover, the scatter in our\nlensing-based scaling relations is morphology dependent, with 30-40% larger\nM_wl for undisturbed compared to disturbed clusters at the same Y_sph at r_500.\nFurther examination suggests that the segregation may be explained by the\ninability of our spherical lens models to faithfully describe the\nthree-dimensional structure of the clusters, in particular, the structure along\nthe line-of-sight. We find that the ellipticity of the brightest cluster\ngalaxy, a proxy for halo orientation, correlates well with the offset in mass\nfrom the mean scaling relation, which supports this picture. This provides\nempirical evidence that line-of-sight projection effects are an important\nsystematic uncertainty in lensing-based scaling relations.\n