Mass Star Formation II : The Mass Function of Submillimeter Clumps in M 17

We have mapped a ∼ 5.5×5.5 pc portion of the M17 massive star-forming region in both 850 and 450 μm dust continuum emission using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). The maps reveal more than 100 dusty clumps with deconvolved linear sizes of ∼0.05–0.2 pc and masses of ∼0.8–120 M⊙, most of which are not associated with known mid-infrared point sources. Fitting the clump mass function with a double power law gives a mean power law exponent of αhigh = −2.4 ± 0.3 for the high-mass power law, consistent with the exponent of the Salpeter stellar mass function. We show that a lognormal clump mass distribution with a peak at ∼4 M⊙ produces as good a fit to the clump mass function as does a double power law. This 4 M⊙ peak mass is well above the peak masses of both the stellar initial mass function and the mass function of clumps in low-mass star-forming regions. Despite the difference in intrinsic mass scale, the shape of the M17 clump mass function appears to be consistent with the shape of the core mass function in low-mass star-forming regions. Thus, we suggest that the clump mass function in high-mass star-forming regions may be a scaled-up version of that in low-mass regions, instead of its extension to higher masses. Subject headings: stars: formation — ISM: individual (M17) — submillimeter — ISM: structure — methods: data analysis