We present the first weak-lensing-based scaling relation between galaxy cluster mass, M WL , and integrated Compton parameter Y sph . 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 M WL −Y sph scaling relations, measured at ∆ = 500, 1000, and 2500 ρ c , are consistent in slope and normalization with previous results derived under the assumption of hydrostatic equilibrium (HSE). We find an intrinsic scatter in M WL at fixed Y sph of 20%, larger than both previous measurements of M HSE − Y sph scatter as well as the scatter in true mass at fixed Y sph found in simulations. Moreover, the scatter in our lensing-based scaling relations is morphology dependent, with 30 -40% larger M WL for undisturbed compared to disturbed clusters at the same Y sph 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.

Extragalactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of millijansky source fluxes from 89 fields centered on known massive galaxy clusters and 8 noncluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5 0 of the cluster center) are a factor of 8:9 þ4:3 À2:8 times higher than counts in the outer regions of the cluster fields (radius greater than 0.5 0 ). Counts in the outer regions of the cluster fields are, in turn, a factor of 3:3 þ4:1 À1:8 greater than those in the noncluster fields. Counts in the noncluster fields are consistent with extrapolations from the results of other surveys. We compute the spectral indices of millijansky sources in the cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of ¼ 0:66 with an rms dispersion of 0.36, where flux S / À . The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.

We introduce an analytic model of the diffuse intergalactic medium in galaxy clusters based on a polytropic equation of state for the gas in hydrostatic equilibrium with the cluster gravitational potential. This model is directly applicable to the analysis of X-ray and Sunyaev-Zeldovich Effect observations from the cluster core to the virial radius, with 5 global parameters and 3 parameters describing the cluster core. We validate the model using Chandra X-ray observations of two polytropic clusters, MS 1137.5+6625 and CL J1226.9+3332, and two cool core clusters, Abell 1835 and Abell 2204. We show that the model accurately describes the spatially resolved spectroscopic and imaging data, including the cluster core region where significant cooling of the plasma is observed.

We present the Sunyaev-Zel'dovich (SZ) effect observations of a sample of 25 massive relaxed galaxy clusters observed with the Sunyaev-Zel'dovich array (SZA), an eight-element interferometer that is part of the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We performed an analysis of new SZA data and archival Chandra observations of this sample to investigate the integrated pressure-a proxy for cluster mass-determined from x-ray and SZ observations, two independent probes of the intra-cluster medium (ICM). This analysis makes use of a model for the ICM introduced by Bulbul (2010 Astrophys. J. 720 1038) which can be applied simultaneously to the SZ and x-ray data. With this model, we estimated the pressure profile for each cluster using a joint analysis of the SZ and x-ray data, and using the SZ data alone. We found that the integrated pressures measured from the x-ray and SZ data are consistent. This conclusion is in agreement with recent results obtained using WMAP and Planck data, confirming that SZ and x-ray observations of massive clusters detect the same amount of thermal pressure from the ICM. To test for possible biases introduced by our choice of model, we also fitted the SZ data using the universal pressure profile proposed by Arnaud (2010 Astron. Astrophys. 517 A92) and found consistency between the two models out to r 500 in the pressure profiles and integrated pressures.

We present the first measurement of the relationship between the Sunyaev-Zel'dovich effect (SZE) signal and the mass of galaxy clusters that uses gravitational lensing to measure cluster mass, based on 14 X-ray luminous clusters at z 0.2 from the Local Cluster Substructure Survey. We measure the integrated Compton y-parameter, Y, and total projected mass of the clusters (M GL ) within a projected clustercentric radius of 350 kpc, corresponding to mean overdensities of 4000-8000 relative to the critical density. We find self-similar scaling between M GL and Y, with a scatter in mass at fixed Y of 32%. This scatter exceeds that predicted from numerical cluster simulations, however, it is smaller than comparable measurements of the scatter in mass at fixed T X . We also find no evidence of segregation in Y between disturbed and undisturbed clusters, as had been seen with T X on the same physical scales. We compare our scaling relation to the Bonamente et al. relation based on mass measurements that assume hydrostatic equilibrium, finding no evidence for a hydrostatic mass bias in cluster cores (M GL = 0.98 ± 0.13 M HSE ), consistent with both predictions from numerical simulations and lensing/ X-ray-based measurements of mass-observable scaling relations at larger radii. Overall our results suggest that the SZE may be less sensitive than X-ray observations to the details of cluster physics in cluster cores.