Shells and shocks in the galactic star-forming region RCW 49

Abstract

RCW 49, also known as G284.4-0.3 (Goss & Shaver 1970), is a very bright, complex and extended HII region (~ 40´ × 50´), largely imaged at radio continuum and recombination lines. Recent studies using Spitzer data pointed to the super star cluster Westerlund 2 as RCW 49 ionizing agent and confirmed that star formation is taking place there (Churchwell et al. 2004). Using Chandra data, Tsujimoto et al. (2007) cataloged hundreds of cluster members, mostly young stellar object (YSO) candidates and early-type stars. Whiteoak & Uchida (1997) obtained radio continuum maps with the Compact Array at 1.4 and 2.4 GHz and the Molonglo Observatory Synthesis Telescope (MOST) at 843 MHz. They identified two shell-like structures, shown in Figure 1: one to the south around the bright star WR 20b (in purple), and one incomplete shell in the north surrounding Westerlund 2 (in magenta), with a possible blister toward the west.