期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 696, 期 2, 页码 L115-L119出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/696/2/L115
关键词
H II regions; ISM: clouds; ISM: individual (RCW 49); open clusters and associations: individual (Westerlund 2)
资金
- MEXT
- JSPS [17004]
We have made CO(J = 2-1) observations toward the H II region RCW 49 and its ionizing source, the rich stellar cluster Westerlund 2, with the NANTEN2 submillimeter telescope. These observations have revealed that two molecular clouds in velocity ranges of-11 to + 9 km s(-1) and 11 to 21 km s-1, respectively, show remarkably good spatial correlations with the Spitzer IRAC mid-infrared image of RCW 49, as well a velocity structures indicative of localized expansion around the bright central regions and stellar cluster. This strongly suggests that the two clouds are physically associated with RCW 49. We obtain a new kinematic distance estimate to RCW 49 and Wd2 of 5.4(-1.4)(+1.1) kpc, based on the mean velocity and velocity spread of the associated gas. We argue that the acceleration of the gas by stellar winds from Westerlund 2 is insufficient to explain the entire observed velocity dispersion of the molecular gas, and suggest a scenario in which a collision between the two clouds similar to 4 Myr ago may have triggered the formation of the stellar cluster.
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