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Anomalous Microwave Emission from the H II Region RCW175

Dickinson, C. and Davies, R. D. and Allison, J. R. and Bond, J. R. and Casassus, S. and Cleary, K. and Davis, R. J. and Jones, M. E. and Mason, B. S. and Myers, S. T. and Pearson, T. J. and Readhead, A. C. S. and Sievers, J. L. and Taylor, A. C. and Todorović, M. and White, G. J. and Wilkinson, P. N. (2009) Anomalous Microwave Emission from the H II Region RCW175. Astrophysical Journal, 690 (2). pp. 1585-1589. ISSN 0004-637X.

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We present evidence for anomalous microwave emission in the RCW175 H II region. Motivated by 33 GHz 13' resolution data from the Very Small Array (VSA), we observed RCW175 at 31 GHz with the Cosmic Background Imager (CBI) at a resolution of 4'. The region consists of two distinct components, G29.0-0.6 and G29.1-0.7, which are detected at high signal-to-noise ratio. The integrated flux density is 5.97 ± 0.30 Jy at 31 GHz, in good agreement with the VSA. The 31 GHz flux density is 3.28 ± 0.38 Jy (8.6σ) above the expected value from optically thin free-free emission based on lower frequency radio data and thermal dust constrained by IRAS and WMAP data. Conventional emission mechanisms such as optically thick emission from ultracompact H II regions cannot easily account for this excess. We interpret the excess as evidence for electric dipole emission from small spinning dust grains, which does provide an adequate fit to the data.

Item Type:Article
Related URLs:
URLURL TypeDescription
Dickinson, C.0000-0002-0045-442X
Bond, J. R.0000-0003-2358-9949
Jones, M. E.0000-0003-3564-6680
Pearson, T. J.0000-0001-5213-6231
Readhead, A. C. S.0000-0001-9152-961X
Additional Information:© 2009. The American Astronomical Society. Received 2008 July 24; accepted 2008 September 11; published 2008 December 22. Print publication: Issue 2 (2009 January 10). We thank the anonymous referee for useful comments. This work was supported by the Strategic Alliance for the Implementation of New Technologies (SAINT; see, and we are most grateful to the SAINT partners for their strong support. We gratefully acknowledge support from the Kavli Operating Institute and thank B. Rawn and S. Rawn, Jr. The CBI was supported by NSF grants 9802989, 0098734, and 0206416, and a Royal Society Small Research Grant. We are particularly indebted to the engineers who maintain and operate the CBI: C. Achermann, R. Bustos, C. Jara, N. Oyarace, R. Reeves, M. Shepherd, and C. Verdugo. C.D. thanks Roberta Paladini and Bill Reach for useful discussions. C.D. acknowledges support from the U.S. Planck project, which is funded by the NASA Science Mission Directorate. S.C. acknowledges support from FONDECYT grant 1030805, and from the Chilean Center for Astrophysics FONDAP 15010003. A.T. acknowledges support from Royal Society and STFC research fellowships.
Funding AgencyGrant Number
Strategic Alliance for the Implementation of New Technologies (SAINT)UNSPECIFIED
Kavli Operating InstituteUNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)UNSPECIFIED
Centro de Astrofísica (FONDAP)15010003
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:ISM: individual (RCW175); radiation mechanisms: general; radio continuum: ISM
Issue or Number:2
Record Number:CaltechAUTHORS:DICapj09
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12823
Deposited By: Archive Administrator
Deposited On:30 Dec 2008 01:04
Last Modified:30 Oct 2020 22:03

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