High resolution radio emission from RCW 49/Westerlund 2
  RCW49 and its ionizing cluster form an extensive, complex region, widely
studied at IR and optical wavelengths. Molonglo 843 MHz and ATCA 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 RCW49 field were obtained to survey the radio
emission at arcsec scale and investigate the small-scale features and nature of
the HII region.- Data were collected with the new 2-GHz bandwidth receivers and
the CABB correlator of the 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, together
with optical, IR, X-ray, and gamma-ray observations.- The CABB data result in
the most detailed radio continuum images of RCW49 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 consistent with a free-free
emission mechanism. However, hints of nonthermal components are also present in
the bridge. A 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 RCW49. We also report on and discuss the possible detection of
a H RRL.- The radio results support an association between the cm continuum and
molecular emission. The detection of the RRL kinematically favors a RCW49
distance of 6--7 kpc. If the negative spectral indices measured at the bridge
are caused by synchrotron emission, we propose a scenario where high-energy
emission could be produced. Finally, the newly discovered jet-like structure
appears to deserve a detailed study by itself.
