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X-ray and Sunyaev–Zeldovich effect (SZE) observations of galaxy clusters can be used to measure their distances independently of the cosmic distance ladder. We have determined the distance to 38 clusters of galaxies in the redshift range 0.14 ≤ z ≤ 0.89 using X-ray data from the Chandra X-ray Observatory and SZE data from the Owens Valley Radio Observatory and the Berkeley–Illinois–Maryland Association interferometric arrays. We measure a Hubble constant of H0 = 76.9+3.9−3.4+10.0−8.0 km s−1 Mpc−1 (statistical followed by systematic uncertainties at 68% confidence) for an ΩM=0.3, ΩΛ=0.7 cosmology. Our determination of the Hubble parameter in the distant Universe agrees with measurements from the Hubble Space Telescope Key Project that probed the nearby Universe. [ABSTRACT FROM PUBLISHER]

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 r500 in the pressure profiles and integrated pressures. [ABSTRACT FROM AUTHOR]

In contemporary Cosmic Microwave Background experiments, bolometric detectors are often background limited, and in this case the sensitivity of instruments can only be improved by increasing the number of background-limited detectors, and so contemporary TES receivers contain as many pixels as possible. Frequency-Domain Multiplexing (fMUX) is one strategy for reading out many detectors with one SQUID. For any readout system, it is important to carefully evaluate the thermal design of detector, in conjunction with the readout bandwidth, in order to ensure stable electro-thermal feedback (ElF). We demonstrate a novel technique for characterizing the thermal circuit of our detectors, using am AC-bias and the fMUX electronics. This technique is used to study the internal thermal coupling of a TES bolometer. We illustrate how the insights gathered by this technique have been instrumental in improving the stability of our multiplexed detectors for the South Pole Telescope (SPT). [ABSTRACT FROM AUTHOR]

We will discuss the design, fabrication, and testing of a 960-element TES array installed on the new 10 meter South Pole Telescope (SPT). This array is designed to survey for galaxy clusters using the Sunyaev-Zel'dovich (SZ) effect, which is the inverse-Compton scattering of Cosmic Microwave Background photons by plasma bound to clusters of galaxies. The SPT bolometer array consists of fully lithographed spider-web absorbers fabricated on adhesive-bonded silicon wafers with an embedded metal back plane. The absorbers are connected to aluminum-titanium bilayer TESs with a transition temperature of approximately 550 mK. Additional normal-metal features adjust the devices' thermal properties to suit our readout system and observational strategy. The focal plane is cooled using a commercial, closed cycle, pulsetube refrigerator and a three-stage helium sorption refrigerator with a 250 mK base temperature. [ABSTRACT FROM AUTHOR]