A large-scale 13co mapping of the w 49 a molecular cloud complex

Abstract

We present 13CO (J = 1-0) and Cl8O (J = 1-0) maps of the W 49 A molecular cloud complex observed at a resolution of 17″" (HPBW). Fourteen features (MHH-1 to MHH-14) were identified in the 13CO velocity channel maps, most of them distributed within an area of 6′ (20 pc) in diameter with their total mass amounting to 1.7 x 10 6 Modot;. The features have a three-dimensional velocity dispersion of 8 km s-1, which leads to a mean free time per feature of 10 6yr. This suggests that they are interacting one another in a region of ∼20pc in diameter. The feature MHH-1, which corresponds to W 49 N, is unique in that it exhibits a large velocity width (15kms-1 FWHM) and is compact in size (2.3 pc x 3.0pc FWHM), while containing a large mass of 2.4 x 105 Modot;. This indicates that the free-fall time of MHH-1 is on the order of 105yr, an order of magnitude smaller than that of the entire complex. It has turned out that MHH-1 has a smaller spatial width at Vlsr ≲ 8 km s-1 than at ≳ 8 km s-1. This result, together with the line-profile characteristics of various optically thin lines, suggests that at least two massive clouds with different radial velocities exist toward MHH-1. The massive compact feature may have been produced by the interaction of the two different velocity clouds. © 2009. Astronomical Society of Japan.