High-resolution radio emission from RCW 49/Westerlund 2

  1. Get@NRC: High-resolution radio emission from RCW 49/Westerlund 2 (Opens in a new window)
DOIResolve DOI: http://doi.org/10.1051/0004-6361/201321976
AuthorSearch for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for:
Journal titleAstronomy and Astrophysics
Article numberA31
SubjectGamma rays: stars; ISM: individual objects; Open clusters and associations; Radio continuum: ISM; Stars: winds, outflows; Bandwidth; Infrared imaging; Optical waveguides; Telescopes
AbstractAims. The HII region RCW49 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 smallscale 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 RCW49 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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AffiliationNational Science Infrastructure; National Research Council Canada
Peer reviewedYes
NPARC number21270374
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Record identifierd0fef371-cace-4ef9-83b2-f17e3f0d1bbc
Record created2014-02-05
Record modified2016-05-09
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