THE INTERNAL MASS-DISTRIBUTION OF A GIANT MOLECULAR CLOUD WITHOUT STAR FORMATION

High-resolution, low-noise maps have been made of Maddalena's cloud, a large, anomalous molecular cloud in which star formation is absent to a very low level. A rich internal structure is observed, despite the apparent lack of energy input. We characterize the structure in terms of clumps and find that the clump mass spectrum is well fit by a power law, dN/dM is-proportional-to M-1.0 +/- 0.16, flatter than that measured in the same way for the Rosette molecular cloud, a more typical star-forming cloud, and by extrapolation, flatter than the mass spectrum of all giant molecular clouds (GMCs) investigated to date. A Kolmogorov-Smirnov test finds only a 7% probability that the mass distribution of the two clouds sample the same parent distribution. If the clouds that we have observed are not pathological the results suggest that (a) the clumpy structure of molecular clouds is primordial, (b) the mass spectrum of the fragments in a GMC is affected by the evolution of the cloud, and (c) more evolved clouds have a higher fraction of small clumps.