Multi-frequency imaging of the galaxy cluster Abell 2163 using the Sunyaev-Zel'dovich Effect

02/2009; DOI: 10.1051/0004-6361/200911746
Source: arXiv

ABSTRACT We used the APEX-SZ and LABOCA bolometer cameras on the APEX telescope to map the decrement of the Sunyaev-Zeldovich effect at 150 GHz and the increment at 345 GHz toward the galaxy cluster Abell 2163. The SZE images were used to model the radial density and temperature distribution of the ICM, and to derive the gas mass fraction in the cluster under the assumption of hydrostatic equilibrium. We used the isothermal beta model to fit the SZE decrement/increment radial profiles. We performed a simple, non-parametric de-projection of the radial density and temperature profiles, in conjunction with XMM-Newton X-ray data, under the simplifying assumption of spherical symmetry. We combined the peak SZE signals derived in this paper with published SZE measurements of this cluster to derive the cluster line-of-sight bulk velocity and the central Comptonization, using priors on the ICM temperature. We find that the best-fit isothermal model to the SZE data is consistent with the ICM properties implied by the X-ray data, particularly inside the central 1 Mpc radius. Although the assumptions of hydrostatic equilibrium and spherical symmetry may not be optimal for this complex system, the results obtained under these assumptions are consistent with X-ray and weak-lensing measurements. This shows the applicability of the simple joint SZE and X-ray de-projection technique described in this paper for clusters with a wide range of dynamical states. (Abridged) Comment: 14 pages, 9 figures. To appear in A&A. Sections 4 and 5 updated

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    ABSTRACT: The APEX-SZ instrument is a millimeter-wave cryogenic receiver designed to observe galaxy clusters via the Sunyaev-Zel'dovich effect from the 12 m APEX telescope on the Atacama plateau in Chile. The receiver contains a focal plane of 280 superconducting transition-edge sensor (TES) bolometers instrumented with a frequency-domain multiplexed readout system. The bolometers are cooled to 280 mK via a three-stage helium sorption refrigerator and a mechanical pulse-tube cooler. Three warm mirrors, two 4 K lenses, and a horn array couple the TES bolometers to the telescope. APEX-SZ observes in a single frequency band at 150 GHz with 1' angular resolution and a 22' field-of-view, all well suited for cluster mapping. The APEX-SZ receiver has played a key role in the introduction of several new technologies including TES bolometers, the frequency-domain multiplexed readout, and the use of a pulse-tube cooler with bolometers. As a result of these new technologies, the instrument has a higher instantaneous sensitivity and covers a larger field-of-view than earlier generations of Sunyaev-Zel'dovich instruments. Since its commissioning in April 2007, APEX-SZ has been used to map tens of clusters. We describe the design of the receiver and its performance when installed on the APEX telescope.
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    ABSTRACT: We present results of X-ray observations of a sample of 15 clusters selected via their imprint on the cosmic microwave background (CMB) from the thermal Sunyaev-Zel'dovich (SZ) effect. These clusters are a subset of the first SZ-selected cluster catalog, obtained from observations of 178 deg^2 of sky surveyed by the South Pole Telescope. Using X-ray observations with Chandra and XMM-Newton, we estimate the temperature, T_X, and mass, M_g, of the intracluster medium (ICM) within r_500 for each cluster. From these, we calculate Y_X=M_g T_X and estimate the total cluster mass using a M_500-Y_X scaling relation measured from previous X-ray studies. The integrated Comptonization, Y_SZ, is derived from the SZ measurements, using additional information from the X-ray measured gas density profiles and a universal temperature profile. We calculate scaling relations between the X-ray and SZ observables, and find results generally consistent with other measurements and the expectations from simple self-similar behavior. Specifically, we fit a Y_SZ-Y_X relation and find a normalization of 0.82 +- 0.07, marginally consistent with the predicted ratio of Y_SZ/Y_X=0.91+-0.01 that would be expected from the density and temperature models used in this work. Using the Y_X derived mass estimates, we fit a Y_SZ-M_500 relation and find a slope consistent with the self-similar expectation of Y_SZ ~ M^5/3 with a normalization consistent with predictions from other X-ray studies. We compare the X-ray mass estimates to previously published SZ mass estimates derived from cosmological simulations of the SPT survey. We find that the SZ mass estimates are lower by a factor of 0.89+-0.06, which is within the ~15% systematic uncertainty quoted for the simulation-based SZ masses.
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    ABSTRACT: Until recently, only about 10 % of the total intracluster gas volume had been studied with high accuracy, leaving a vast region essentially unexplored. This is now changing and a wide area of hot gas physics and chemistry awaits discovery in galaxy cluster outskirts. Also, robust large-scale total mass profiles and maps are within reach. First observational and theoretical results in this emerging field have been achieved in recent years with sometimes surprising findings. Here, we summarize and illustrate the relevant underlying physical and chemical processes and review the recent progress in X-ray, Sunyaev–Zel’dovich, and weak gravitational lensing observations of cluster outskirts, including also brief discussions of technical challenges and possible future improvements.
    Space Science Reviews 08/2013; 177(1-4). · 5.52 Impact Factor

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