AMiBA: Cluster Sunyaev-Zel'dovich Effect Observations with the Expanded 13-Element Array

Kai-Yang Lin, Hiroaki Nishioka, Fu-Cheng Wang, Chih-Wei Locutus Huang, Yu-Wei Liao, Jiun-Huei Proty Wu, Patrick M. Koch, Keiichi Umetsu, Ming-Tang Chen, Shun-Hsiang Chan, Shu-Hao Chang, Wen-Hsuan Lucky Chang, Tai-An Cheng, Hoang Ngoc Duy, Szu-Yuan Fu, Chih-Chiang Han, Solomon Ho, Ming-Feng Ho, Paul T. P. Ho, Yau-De HuangHomin Jiang, Derek Y. Kubo, Chao-Te Li, Yu-Chiung Lin, Guo-Chin Liu, Pierre Martin-Cocher, Sandor M Molnar, Emmanuel Nunez, Peter Oshiro, Shang-Ping Pai, Philippe Raffin, Anthony Ridenour, Chia-You Shih, Sara Stoebner, Giap-Siong Teo, Jia-Long Johnny Yeh, Joshua Williams, Mark Birkinshaw

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The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is a co-planar interferometer array operating at a wavelength of 3 mm to measure the Sunyaev-Zel-dovich effect (SZE) of galaxy clusters at arcminute scales. The first phase of operation-with a compact 7-element array with 0.6 m antennas (AMiBA-7)-observed six clusters at angular scales from 5′ to 23′. Here, we describe the expansion of AMiBA to a 13-element array with 1.2 m antennas (AMiBA-13), its subsequent commissioning, and cluster SZE observing program. The most noticeable changes compared to AMiBA-7 are (1) array re-configuration with baselines ranging from 1.4 m to 4.8 m, allowing us to sample structures between 2′ and 10′, (2) 13 new lightweight carbon-fiber-reinforced plastic (CFRP) 1.2 m reflectors, and (3) additional correlators and six new receivers. Since the reflectors are co-mounted on and distributed over the entire six-meter CFRP platform, a refined hexapod pointing error model and phase error correction scheme have been developed for AMiBA-13. These effects-entirely negligible for the earlier central close-packed AMiBA-7 configuration-can lead to additional geometrical delays during observations. Our correction scheme recovers at least 80 ± 5% of the point-source fluxes. We, therefore, apply an upward correcting factor of 1.25 to our visibilities to correct for phase decoherence, and a ± 5% systematic uncertainty is added in quadrature with our statistical errors. We demonstrate the absence of further systematics with a noise level consistent with zero in stacked uv-visibilities. From the AMiBA-13 SZE observing program, we present here maps of a subset of 12 clusters with signal-to-noise ratios above five. We demonstrate combining AMiBA-7 with AMiBA-13 observations on Abell 1689, by jointly fitting their data to a generalized Navarro-Frenk-White model. Our cylindrically integrated Compton-y values for five radii are consistent with results from the Berkeley-Illinois- Maryland Array, the Owens Valley Radio Observatory, the Sunyaev-Zel-dovich Array, and the Planck Observatory. We also report the first targeted SZE detection toward the optically selected cluster RCS J1447 +0828, and we demonstrate the ability of AMiBA SZE data to serve as a proxy for the total cluster mass. Finally, we show that our AMiBA-SZE derived cluster masses are consistent with recent lensing mass measurements in the literature.

Original languageEnglish
Article number91
Number of pages21
JournalAstrophysical Journal
Issue number2
Early online date14 Oct 2016
Publication statusPublished - 20 Oct 2016


  • cosmology: cosmic background radiation
  • galaxies: clusters: general
  • instrumentation: interferometers

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