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Published February 10, 2011 | Published
Journal Article Open

Cluster Morphologies and Model-independent Y_(SZ) Estimates from Bolocam Sunyaev-Zel'dovich Images


We present initial results from our ongoing program to image the Sunyaev–Zel'dovich (SZ) effect in galaxy clusters at 143 GHz using Bolocam; five clusters and one blank field are described in this manuscript. The images have a resolution of 58 arcsec and a radius of ≃6–7 arcmin, which is approximately r500–2r500 for these clusters. We effectively high-pass filter our data in order to subtract noise sourced by atmospheric fluctuations, but we are able to obtain unbiased images of the clusters by deconvolving the effects of this filter. The beam-smoothed rms is ≃10 μKCMB in these images; with this sensitivity, we are able to detect the SZ signal to beyond r500 in binned radial profiles. We have fit our images to beta and Nagai models, fixing spherical symmetry or allowing for ellipticity in the plane of the sky, and we find that the best-fit parameter values are in general consistent with those obtained from other X-ray and SZ data. Our data show no clear preference for the Nagai model or the beta model due to the limited spatial dynamic range of our images. However, our data show a definitive preference for elliptical models over spherical models, quantified by an F ratio of ≃20 for the two models. The weighted mean ellipticity of the five clusters is ε = 0.27 ± 0.03, consistent with results from X-ray data. Additionally, we obtain model-independent estimates of Y500, the integrated SZ y-parameter over the cluster face to a radius of r500, with systematics-dominated uncertainties of ≃10%. Our Y500 values, which are free from the biases associated with model-derived Y500 values, scale with cluster mass in a way that is consistent with both self-similar predictions and expectations of a ≃10% intrinsic scatter.

Additional Information

© 2011 American Astronomical Society. Received 2010 October 8; accepted 2010 December 3; published 2011 January 18. We acknowledge the assistance of Nicole Czakon, Tom Downes, and Seth Siegel, who have provided numerous comments and suggestions about the data analysis; the Bolocam instrument team: P. A. R. Ade, J. E. Aguirre, J. J. Bock, S. F. Edgington, J. Glenn, A. Goldin, S. R. Golwala, D. Haig, A. E. Lange, G. T. Laurent, P.D. Mauskopf, H. T.Nguyen, P. Rossinot, and J. Sayers; Matt Ferry, who helped collect the data for A1835 and MS1054.4−0321; the day crew and Hilo staff of the Caltech Submillimeter Observatory, who provided invaluable assistance during commissioning and data-taking for this survey data set; Daisuke Nagai for useful discussions about cluster modeling; Tony Mroczkowski for providing the best-fit parameters from his group's analysis of A1835, useful comments about cluster modeling, and pointing out a typo in our original arXiv posting; the referee for several useful comments and suggestions; and Kathy Deniston, Barbara Wertz, and Diana Bisel, who provided effective administrative support at Caltech and in Hilo. Bolocam was constructed and commissioned using funds from NSF/AST-9618798, NSF/AST-0098737, NSF/AST-9980846, NSF/AST-0229008, and NSF/AST-0206158. J.S. was partially supported by a NASA Graduate Student Research Fellowship and a NASA Postdoctoral Program fellowship, S.A. and E.P. were partially supported by NSF grant AST-0649899, S.A. was partially supported by the USC WiSE postdoctoral fellowship and travel grants, and E.P. was partially supported by NASA grant NNXO7AH59G and JPL-Planck subcontract 1290790. Facilities: CSO

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