SUNYAEV-ZEL'DOVICH EFFECT OBSERVATIONS OF THE BULLET CLUSTER (1E 0657-56) WITH APEX-SZ
- Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)
- Department of Physics, McGill University, Montreal H3A 2T8 (Canada)
- School of Physics and Astronomy, Cardiff University, CF24 3YB Wales (United Kingdom)
- Argelander Institute for Astronomy, Bonn University, Bonn (Germany)
- Department of Physics, University of California, Berkeley, CA 94720 (United States)
- National Institute of Standards and Technology, Boulder, CO 80305 (United States)
- Max Planck Institute for Radioastronomy, 53121 Bonn (Germany)
We present observations of the Sunyaev-Zel'dovich effect (SZE) in the Bullet cluster (1E 0657-56) using the APEX-SZ instrument at 150 GHz with a resolution of 1'. The main results are maps of the SZE in this massive, merging galaxy cluster. The cluster is detected with 23{sigma} significance within the central 1' radius of the source position. The SZE map has a broadly similar morphology to that in existing X-ray maps of this system, and we find no evidence for significant contamination of the SZE emission by radio or IR sources. In order to make simple quantitative comparisons with cluster gas models derived from X-ray observations, we fit our data to an isothermal elliptical {beta} model, despite the inadequacy of such a model for this complex merging system. With an X-ray-derived prior on the power-law index, {beta} = 1.04{sup +0.16} {sub -0.10}, we find a core radius r {sub c} = 142'' {+-} 18'', an axial ratio of 0.889 {+-} 0.072, and a central temperature decrement of -771 {+-} 71 {mu}K{sub CMB}, including a {+-}5.5% flux calibration uncertainty. Combining the APEX-SZ map with a map of projected electron surface density from Chandra X-ray observations, we determine the mass-weighted temperature of the cluster gas to be T {sub mg} = 10.8 {+-} 0.9 keV, significantly lower than some previously reported X-ray spectroscopic temperatures. Under the assumption of an isothermal cluster gas distribution in hydrostatic equilibrium, we compute the gas mass fraction for prolate and oblate spheroidal geometries and find it to be consistent with previous results from X-ray and weak-lensing observations. This work is the first result from the APEX-SZ experiment, and represents the first reported scientific result from observations with a large array of multiplexed superconducting transition-edge sensor bolometers.
- OSTI ID:
- 21313716
- Journal Information:
- Astrophysical Journal, Vol. 701, Issue 1; Other Information: DOI: 10.1088/0004-637X/701/1/42; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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