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High-resolution radio emission from RCW 49/Westerlund 2

Benaglia, P. and Koribalski, B. and Peri, C. S. and Martí, J. and Sánchez-Sutil, J. R. and Dougherty, S. M. and Noriega-Crespo, A. (2013) High-resolution radio emission from RCW 49/Westerlund 2. Astronomy and Astrophysics, 559 . Art. No. A31. ISSN 0004-6361. doi:10.1051/0004-6361/201321976.

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Aims. The HII region RCW 49 and its ionizing cluster form an extensive, complex region that has been widely studied at infrared (IR) and optical wavelengths. The Molonglo 843 MHz and Australia Telescope Compact Array data at 1.4 and 2.4 GHz showed two shells. Recent high-resolution IR imaging revealed a complex dust structure and ongoing star formation. New high-bandwidth and high-resolution data of the RCW 49 field have been obtained to survey the radio emission at arcsec scale and investigate the small-scale features and nature of the HII region. Methods. Radio observations were collected with the new 2-GHz bandwidth receivers and the CABB correlator of the Australia Telescope Compact Array [ATCA], at 5.5 and 9.0 GHz. In addition, archival observations at 1.4 and 2.4 GHz have been re-reduced and re-analyzed in conjunction with observations in the optical, IR, X-ray, and gamma-ray regimes. Results. The new 2-GHz bandwidth data result in the most detailed radio continuum images of RCW 49 to date. The radio emission closely mimics the near-IR emission observed by Spitzer, showing pillars and filaments. The brightest continuum emission comes from the region known as the bridge. The overall flattish spectral index is typically consistent with a free-free emission mechanism. However, hints of nonthermal components are also present in the bridge. An interesting jet-like structure surrounded by a bubble feature whose nature is still unclear has been discovered close to the Westerlund 2 core. Two apparent bow shocks and a number of discrete sources have been detected as well in the surroundings of RCW 49. In addition, we also report on and discuss the possible detection of a hydrogen recombination line. Conclusions. The radio results support an association between the cm continuum and molecular emission. The detection of the radio recombination line kinematically favors a RCW 49 distance of 6–7 kpc. If the negative spectral indices measured at the bridge should be confirmed to be caused by synchrotron emission, we propose a scenario where high-energy emission could be produced. Finally, the newly discovered jet-like structure appears to be an intriguing source that deserves a detailed study by itself.

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Noriega-Crespo, A.0000-0002-6296-8960
Additional Information:© 2013 ESO. Received 27 May 2013; Accepted 14 August 2013. Published online 31 October 2013. We thank the anonymous referee for the careful reading of our manuscript and useful comments. P.B. wishes to thank people at ATNF that helped in various ways, for instance, Nathan Pope, Marc Wieringa, Robin Wark, Vanessa Moss, Jill Rathborne, Jim Caswell, Shari Breen, and also G.E. Romero. We are grateful to Yael Nazé, who provided the Chandra data fits images, and to Roberta Paladini, who provided the results of RRL data of RCW 49 in advance of publication. J.M. and J.R.S.S. acknowledge support for different aspects of this work by grants AYA2010-21782-C03-03 from the Spanish Government and Consejería de Economía, Innovación y Ciencia of Junta de Andalucía as research group FQM-322, as well as FEDER funds. P.B. acknowledges support from PICT 2007, 00848 (ANPCyT). This research has made use of NASA’s Astrophysics Data System Bibliographic Services, of the SIMBAD database, operated at CDS, Strasbourg, France and of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Funding AgencyGrant Number
Spanish GovernmentAYA2010-21782-C03-03
Junta de Andalucía (Spain) Consejería de Economía, Innovación y CienciaFQM-322
Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) (Argentina)PICT 2007, 00848
Subject Keywords:stars: winds, outflows; ISM: individual objects: RCW 49; open clusters and associations: individual: Westerlund 2; radio continuum: ISM; gamma rays: stars
Record Number:CaltechAUTHORS:20140211-092131840
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Official Citation:Benaglia, P., Koribalski, B., Peri, C. S., Martí, J., Sánchez-Sutil, J. R., Dougherty, S. M., & Noriega-Crespo, A. (2013). High-resolution radio emission from RCW 49/Westerlund 2. A&A, 559, A31.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43768
Deposited On:11 Feb 2014 17:57
Last Modified:10 Nov 2021 16:42

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