Molecular clumps in the W51 giant molecular cloud

Parsons, H.; Thompson, M. A.; Clark, J. S. and Chrysostomou, A. (2012). Molecular clumps in the W51 giant molecular cloud. Monthly Notices of the Royal Astronomical Society, 424(3) pp. 1658–1671.



In this paper, we present a catalogue of dense molecular clumps located within the W51 giant molecular cloud (GMC). This work is based on Heterodyne Array Receiver Programme 13CO J = 3–2 observations of the W51 GMC and uses the automated CLUMPFIND algorithm to decompose the region into a total of 1575 clumps of which 1130 are associated with the W51 GMC.We clearly see the distinct structures of theW51 complex and the high-velocity stream previously reported. We find the clumps have characteristic diameters of 1.4 pc, excitation temperatures of 12 K, densities of 5.6 × 1021 cm−2, surface densities 0.02 g cm−2 and masses of 90M. We find a total mass of dense clumps within the GMC of 1.5 × 105M�, with only 1 per cent of the clumps detected by number and 4 per cent by mass found to be supercritical. We find a clump-forming efficiency of 14 ± 1 per cent for the W51 GMC and a supercritical clump-forming efficiency of 0.5+2.3 −0.5 per cent. Looking at the clump mass distribution, we find it is described by a single power law with a slope of α = 2.4+0.2 −0.1 above ~100M�. By comparing locations of supercritical clumps and young clusters, we see that any future star formation is likely to be located away from the currently active W51A region.

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