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We present results from a survey of the central 700 arcmin2 region of the ρ Ophiuchi molecular cloud at 850 μm using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. Using the clump-finding procedure developed by Williams et al., we identify 55 independent objects and compute size, flux, and degree of central concentration. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that the clumps have internal temperatures of 10-30 K and surface pressures P/k = 106-7 K cm-3, consistent with the expected average pressure in the ρ Ophiuchi central region, P/k ~ 2 × 107 K cm-3. The clump masses span 0.02-6.3 M☉ assuming a dust temperature Td ~ 20 K and a dust emissivity κ850 = 0.01 cm2 g-1. The distribution of clump masses is well characterized by a broken power law, N(M) ∝ M-α, with α = 1.0-1.5 for M > 0.6 M☉ and α = 0.5 for M ≤ 0.6 M☉, although significant incompleteness may affect the slope at the lower mass end. This mass function is in general agreement with the ρ Ophiuchi clump mass function derived at 1.3 mm by Motte et al. The two-point correlation function of the clump separations is measured and reveals clustering on size scales r < 3 × 104 AU with a radial power-law exponent γ = 0.75.

We have observed the HCO+ J=3-2 line toward 17 starless cores selected from the list of Ward-Thompson et al. (1994). Six of these cores have line asymmetries indicative of collapse. The excess of blue-skewed profiles over red-skewed profiles is at least as large as that found in samples of Class 0 and early Class I sources. The observed line profiles have the same narrow linewidths and small peak temperatures predicted for young sources in evolutionary models, but the blue/red ratios, like those of older sources, are higher than models predict. The infall signature also occurs over large scales, suggesting that these cores have overall inward motions. We have divided these starless cores into two groups based on the continuum photometry of Ward-Thompson et al. and our HCO+ data. We find stronger HCO+ emission among the cores detected in the submillimeter and all the blue-skewed line profiles are in this group, supporting the suggestion of Ward-Thompson et al. that these are the pre-protostellar cores., Comment: 22 pages, 6 figures, to be published in The Astrophysical Journal