Large Area Mapping at 850 μm. IV. Analysis of the Clump Distribution in the Orion B South Molecular Cloud

Abstract

We present results from a 2300 arcmin2 survey of the Orion A molecular cloud at 450 and 850 μm using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. The region mapped lies directly south of the OMC 1 cloud core and includes OMC 4, OMC 5, HH 1/2, HH 34, and L1641N. We identify 71 independent clumps in the 850 μm map and compute size, flux, and degree of central concentration in each. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that the clumps have internal temperatures Td ~ 22 ± 5 K and surface pressures log(k-1 P cm-3 K) = 6.0 ± 0.2. The clump masses span the range 0.3-22 M☉ assuming a dust temperature Td ~ 20 K and a dust emissivity κ850 = 0.02 cm2 g-1. The distribution of clump masses is well characterized by a power law N(M) M-α with α = 2.0 ± 0.5 for M > 3.0 M☉, indicating a clump mass function steeper than the stellar initial mass function. Significant incompleteness makes determination of the slope at lower masses difficult. A comparison of the submillimeter emission map with an H2 2.122 μm survey of the same region is performed. Several new Class 0 sources are revealed and a correlation is found between both the column density and degree of concentration of the submillimeter sources and the likelihood of coincident H2 shock emission.