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Published February 20, 2013 | Published
Journal Article Open

The Contribution of Radio Galaxy Contamination to Measurements of the Sunyaev-Zel'dovich Decrement in Massive Galaxy Clusters at 140 GHz with Bolocam


We describe in detail our characterization of the compact radio source population in 140 GHz Bolocam observations of a set of 45 massive galaxy clusters. We use a combination of 1.4 and 30 GHz data to select a total of 28 probable cluster-member radio galaxies and also to predict their 140 GHz flux densities. All of these galaxies are steep-spectrum radio sources and they are found preferentially in the cool-core clusters within our sample. In particular, 11 of the 12 brightest cluster-member radio sources are associated with cool-core systems. Although none of the individual galaxies are robustly detected in the Bolocam data, the ensemble-average flux density at 140 GHz is consistent with, but slightly lower than, the extrapolation from lower frequencies assuming a constant spectral index. In addition, our data indicate an intrinsic scatter of ≃ 30% around the power-law extrapolated flux densities at 140 GHz, although our data do not tightly constrain this scatter. For our cluster sample, which is composed of high-mass and moderate-redshift systems, we find that the maximum fractional change in the Sunyaev–Zel'dovich signal integrated over any single cluster due to the presence of these radio sources is ≃ 20%, and only ≃ 1/4 of the clusters show a fractional change of more than 1%. The amount of contamination is strongly dependent on cluster morphology, and nearly all of the clusters with ⩾1% contamination are cool-core systems. This result indicates that radio contamination is not significant compared with current noise levels in 140 GHz images of massive clusters and is in good agreement with the level of radio contamination found in previous results based on lower frequency data or simulations.

Additional Information

© 2013 American Astronomical Society. Received 2012 September 21; accepted 2013 January 1; published 2013 February 1. We acknowledge the assistance of the day crew and Hilo staff of the Caltech Submillimeter Observatory, who provided invaluable assistance during data taking for this data set; Mike Zemcov, Dan Marrone, and John Carlstrom for useful discussions; Max Bonamente, John Carlstrom, Thomas Culverhouse, Christopher Greer,Marshall Joy, James Lamb, Erik Leitch, Dan Marrone, Amber Miller, Thomas Plagge, Matthew Sharp, and David Woody for providing OVRO/BIMA and/or SZA data for our analysis; Kathy Deniston, Barbara Wertz, and Diana Bisel, who provided effective administrative support at Caltech and in Hilo; Matt Hollister and Matt Ferry, who assisted in the collection of these data; and the referee for useful suggestions that significantly improved our manuscript. The Bolocam observations were supported by the Gordon and Betty Moore Foundation. J.S. was supported by a NASA Graduate Student Research Fellowship, a NASA Postdoctoral Program Fellowship, NSF/AST-0838261 and NASA/NNX11AB07G; T.M. was supported by NASA through the Einstein Fellowship Program grant PF0-110077; N.C. was partially supported by a NASA Graduate Student Research Fellowship; A.M. was partially supported by NSF/AST-0838187; S.A., E.P., and J.A.S. were partially supported by NASA/NNX07AH59G; and K.U. acknowledges support from the Academia Sinica Career Development Award. A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This research made use of the Caltech Submillimeter Observatory, which is operated by the California Institute of Technology under cooperative agreement with the National Science Foundation (NSF/AST-0838261). The operation of the SZA was supported by NSF/AST-0838187, and CARMA operations were supported by the CARMA partner universities under a cooperative agreement with the National Science Foundation.

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