We describe Sunyaev-Zel'dovich (SZ) effect measurements and analysis of the intracluster medium (ICM) pressure profiles of a set of 45 massive galaxy clusters imaged using Bolocam at the Caltech Submillimeter Observatory. We deproject the average pressure profile of our sample into 13 logarithmically spaced radial bins between 0.07R 500 and 3.5R 500 , and we find that a generalized Navarro, Frenk, and White (gNFW) profile describes our data with sufficient goodness-of-fit and best-fit parameters (C 500 , α, β, γ , P 0 = 1. 18, 0.86, 3.67, 0.67, 4.29). We use X-ray data to define cool-core and disturbed subsamples of clusters, and we constrain the average pressure profiles of each of these subsamples. We find that, given the precision of our data, the average pressure profiles of disturbed and cool-core clusters are consistent with one another at R 0.15R 500 , with cool-core systems showing indications of higher pressure at R 0.15R 500 . In addition, for the first time, we place simultaneous constraints on the mass scaling of cluster pressure profiles, their ensemble mean profile, and their radius-dependent intrinsic scatter between 0.1R 500 and 2.0R 500 . The scatter among profiles is minimized at radii between 0.2R 500 and 0.5R 500 , with a value of 20%. These results for the intrinsic scatter are largely consistent with previous analyses, most of which have relied heavily on X-ray derived pressures of clusters at significantly lower masses and redshifts compared to our sample. Therefore, our data provide further evidence that cluster pressure profiles are largely universal with scatter of 20%-40% about the universal profile over a wide range of masses and redshifts.

We present a multiwavelength analysis of a sample of four hot (T X > 8 keV) X-ray galaxy clusters (A1689, A2261, A2142, and A2390) using joint AMiBA Sunyaev-Zel'dovich effect (SZE) and Subaru weak lensing observations, combined with published X-ray temperatures, to examine the distribution of mass and the intracluster medium (ICM) in massive cluster environments. Our observations show that A2261 is very similar to A1689 in terms of lensing properties. Many tangential arcs are visible around A2261, with an effective Einstein radius ∼ 40 ′′ (at z ∼ 1.5), which when combined with our weak lensing measurements implies a mass profile well fitted by an NFW model with a high concentration c vir ∼ 10, similar to A1689 and to other massive clusters. The cluster A2142 shows complex mass substructure, and displays a shallower profile (c vir ∼ 5), consistent with detailed X-ray observations which imply recent interaction. The AMiBA map of A2142 exhibits an SZE feature associated with mass substructure lying ahead of the sharp north-west edge of the X-ray core suggesting a pressure increase in the ICM. For A2390 we obtain highly elliptical mass and ICM distributions at all radii, consistent with other X-ray and strong lensing work. Our cluster gas fraction measurements, free from the hydrostatic equilibrium assumption, are overall in good agreement with published X-ray and SZE observations, with the sample-averaged gas fraction of f gas (< r 200 ) = 0.133 ± 0.027, for our sample with M vir = (1.2 ± 0.1) × 10 15 M ⊙ h −1 . When compared to the cosmic baryon fraction f b = Ω b /Ω m constrained by the WMAP 5-year data, this indicates f gas,200 / f b = 0.78 ± 0.16, i.e., (22 ± 16)% of the baryons are missing from the hot phase of clusters.

We report our analysis of MACS J0717.5+3745 using 140 and 268 GHz Bolocam data collected at the Caltech Submillimeter Observatory. We detect extended Sunyaev-Zel'dovich (SZ) effect signal at high significance in both Bolocam bands, and we employ Herschel-SPIRE observations to subtract the signal from dusty background galaxies in the 268 GHz data. We constrain the two-band SZ surface brightness toward two of the sub-clusters of MACS J0717.5+3745: the main sub-cluster (named C), and a sub-cluster identified in spectroscopic optical data to have a line-of-sight velocity of +3200 km s −1 (named B). We determine the surface brightness in two separate ways: via fits of parametric models and via direct integration of the images. For both sub-clusters, we find consistent surface brightnesses from both analysis methods. We constrain spectral templates consisting of relativistically corrected thermal and kinetic SZ signals, using a jointly-derived electron temperature from Chandra and XMM-Newton under the assumption that each sub-cluster is isothermal. The data show no evidence for a kinetic SZ signal toward sub-cluster C, but they do indicate a significant kinetic SZ signal toward sub-cluster B. The model-derived surface brightnesses for sub-cluster B yield a best-fit line-of-sight velocity of v z = +3450 ± 900 km s −1 , with (1 − Prob[v z ≥ 0]) = 1.3 × 10 −5 (4.2σ away from 0 for a Gaussian distribution). The directly integrated sub-cluster B SZ surface brightnesses provide a best-fit v z = +2550 ± 1050 km s −1 , with (1 − Prob[v z ≥ 0]) = 2.2 × 10 −3 (2.9σ).

We present 90, 140, and 268 GHz subarcminute resolution imaging of the Sunyaev-Zel'dovich effect (SZE) in the disturbed, intermediate-redshift (z = 0.5458) galaxy cluster MACS J0717.5+3745, a triple-merger system comprising four distinct, optically detected subclusters. Our 90 GHz SZE data result in a sensitive, 34 μJy beam −1 map of the SZE at 13 effective resolution using the MUSTANG bolometer array on the Green Bank Telescope (GBT). Our 140 and 268 GHz SZE imaging, with resolutions of 58 and 31 and sensitivities of 1.8 and 3.3 mJy beam −1 , respectively, was obtained through observations from the Caltech Submillimeter Observatory using Bolocam. We compare these maps to a two-dimensional pressure map derived from Chandra X-ray observations. Our MUSTANG SZE data confirm previous indications from Chandra of a pressure enhancement due to shockheated, 20 keV gas immediately adjacent to extended radio emission seen in low-frequency radio maps of this cluster. MUSTANG also detects pressure substructure that is not well constrained by the Chandra X-ray data in the remnant core of a merging subcluster. We find that the small-scale pressure enhancements in the MUSTANG data amount to ∼2% of the total pressure measured in the 140 GHz Bolocam observations. The X-ray inferred pseudo-pressure template also fails on larger scales to accurately describe the Bolocam data, particularly at the location of the subcluster with a remnant core known to have a high line-of-sight optical velocity of ∼3200 km s −1 . Our Bolocam data are adequately described when we add an additional component-not described by a thermal SZE spectrum-to the X-ray template coincident with this subcluster. Using flux densities extracted from our model fits, and marginalizing over the X-ray spectroscopic temperature constraints for the region, we fit a thermal + kinetic SZE spectrum to our Bolocam data and find that the subcluster has a best-fit line-of-sight proper velocity v z = 3600 +3440 −2160 km s −1 , in agreement with the optical velocity estimates for the subcluster. The probability v z 0 given our measurements is 2.1%. Repeating this analysis using flux densities measured directly from our maps results in a 3.4% probability v z 0. We note that this tantalizing result for the kinetic SZE is on resolved, subcluster scales.

We present scaling relations between the integrated Sunyaev-Zel'dovich Effect (SZE) signal, Y SZ , its X-ray analogue, Y X ≡M gas T X , and total mass, M tot , for the 45 galaxy clusters in the Bolocam X-ray-SZ (BOXSZ) sample. All parameters are integrated within r 2500 . Y 2500 values are measured using SZE data collected with Bolocam, operating at 140 GHz at the Caltech Submillimeter Observatory (CSO). The temperature, T X , and mass, M gas,2500 , of the intracluster medium are determined using X-ray data collected with Chandra, and M tot is derived from M gas assuming a constant gas mass fraction. Our analysis accounts for several potential sources of bias, including: selection effects, contamination from radio point sources, and the loss of SZE signal due to noise filtering and beam-smoothing effects. We measure the Y 2500 -Y X scaling to have a power-law index of 0.84 ± 0.07, and a fractional intrinsic scatter in Y 2500 of (21 ± 7)% at fixed Y X , both of which are consistent with previous analyses. We also measure the scaling between Y 2500 and M 2500 , finding a power-law index of 1.06 ± 0.12 and a fractional intrinsic scatter in Y 2500 at fixed mass of (25 ± 9)%. While recent SZE scaling relations using X-ray mass proxies have found power-law indices consistent with the self-similar prediction of 5/3, our measurement stands apart by differing from the self-similar prediction by approximately 5σ. Given the good agreement between the measured Y 2500 -Y X scalings, much of this discrepancy appears to be caused by differences in the calibration of the X-ray mass proxies adopted for each particular analysis.