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New Radio Observations of Anomalous Microwave Emission in the H II Region RCW175

Battistelli, E. S. and Carretti, E. and Cruciani, A. and De Bernardis, P. and Génova-Santos, R. and Masi, S. and Naldi, A. and Paladini, R. and Piacentini, F. and Tibbs, C. T. and Verstraete, L. and Ysard, N. (2015) New Radio Observations of Anomalous Microwave Emission in the H II Region RCW175. Astrophysical Journal, 801 (2). Art. No. 111. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20150420-082751362

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Abstract

We have observed the H II region RCW175 with the 64 m Parkes telescope at 8.4 GHz and 13.5 GHz in total intensity, and at 21.5 GHz in both total intensity and polarization. High angular resolution ranging from 1 to 2.4 arcmin, high sensitivity, and polarization capability enable us to perform a detailed study of the different constituents of the H II region. For the first time, we resolve three distinct regions at microwave frequencies, two of which are part of the same annular diffuse structure. Our observations enable us to confirm the presence of anomalous microwave emission (AME) from RCW175. Fitting the integrated flux density across the entire region with the currently available spinning dust models, using physically motivated assumptions, indicates the presence of at least two spinning dust components: a warm component (T_(gas) = 5800 K) with a relatively large hydrogen number density n_H = 26.3/cm^3 and a cold component (T_(gas) = 100 K) with a hydrogen number density of n_H = 150/cm^3. The present study is an example highlighting the potential of using high angular-resolution microwave data to break model parameter degeneracies. Thanks to the spectral coverage and angular resolution of the Parkes observations, we have been able to derive one of the first AME/excess maps, at 13.5 GHz, showing clear evidence that the bulk of the anomalous emission arises in particular from one of the source components, with some additional contribution from the diffuse structure. A cross-correlation analysis with thermal dust emission has shown a high degree of correlation with one of the regions within RCW175. In the center of RCW175, we find an average polarized emission at 21.5 GHz of 2.2 ± 0.2(rand.) ± 0.3(sys.)% of the total emission, where we have included both systematic and statistical uncertainties at 68% CL. This polarized emission could be due to sub-dominant synchrotron emission from the region and is thus consistent with very faint or non-polarized emission associated with AME.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/801/2/111DOIArticle
http://iopscience.iop.org/0004-637X/801/2/111/PublisherArticle
http://arxiv.org/abs/1501.02196arXivDiscussion Paper
ORCID:
AuthorORCID
Paladini, R.0000-0002-5158-243X
Additional Information:© 2015 American Astronomical Society. Received 2014 June 11; accepted 2015 January 9; published 2015 March 12. We acknowledge the use of data from the Planck and Herschel ESA missions. Some of the results are based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. We acknowledge the use of the HEALPix package. We acknowledge the logistic support provided by Parkes operators. The Parkes radio telescope is part of the Australia Telescope National Facility, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. We thank the referee for constructive comments that improved the paper.
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Commonwealth of AustraliaUNSPECIFIED
Subject Keywords:dust, extinction; H II regions; methods: data analysis; polarization; radiation mechanisms: general; radio continuum: ISM
Issue or Number:2
Record Number:CaltechAUTHORS:20150420-082751362
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150420-082751362
Official Citation:New Radio Observations of Anomalous Microwave Emission in the H II Region RCW175 E. S. Battistelli et al. 2015 ApJ 801 111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56755
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:20 Apr 2015 19:13
Last Modified:03 Oct 2019 08:17

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