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

We present the first weak-lensing-based scaling relation between galaxy
\ncluster mass, M $_{WL$, and integrated Compton parameter Y
\n$_sph$. Observations of 18 galaxy clusters at z \\~{}= 0.2 were
\nobtained with the Subaru 8.2 m telescope and the Sunyaev-Zel'dovich
\nArray. The M $_WL$-Y $_sph$ scaling relations, measured
\nat $\\Delta$ = 500, 1000, and 2500 $\\rho$$_ c $, are consistent in
\nslope and normalization with previous results derived under the
\nassumption of hydrostatic equilibrium (HSE). We find an intrinsic
\nscatter in M $_WL$ at fixed Y $_sph$ of 20\\%, larger than
\nboth previous measurements of M $_HSE$-Y $_sph$ scatter
\nas well as the scatter in true mass at fixed Y $_sph$ found in
\nsimulations. Moreover, the scatter in our lensing-based scaling
\nrelations is morphology dependent, with 30\\%-40\\% larger M $_WL$
\nfor undisturbed compared to disturbed clusters at the same Y
\n$_sph$ at r $_ 500$. Further examination suggests that
\nthe segregation may be explained by the inability of our spherical lens
\nmodels to faithfully describe the three-dimensional structure of the
\nclusters, in particular, the structure along the line of sight. We find
\nthat the ellipticity of the brightest cluster galaxy, a proxy for halo
\norientation, correlates well with the offset in mass from the mean
\nscaling relation, which supports this picture. This provides empirical
\nevidence that line-of-sight projection effects are an important
\nsystematic uncertainty in lensing-based scaling relations.
\n}