1996A&A...315..591T

If a cloud is clumpy, and if individual clumps emit lines which are narrower than those emitted by their ensemble (the cloud), they must leave an imprint as velocity structure superimposed on ensemble profiles. Thus, a possible route to explore clumpiness is to observe emission lines with very high signal-to-noise ratios and very high velocity resolution, analyze the fluctuations in brightness temperature present on the line shape, and infer from them the properties of the clumps present in the beam. This technique was developed recently and applied to the case of Orion (Tauber et al. 1991ApJ...375..635T), using CO and ¹³CO lines as tracers. However, in that paper the clumps were assumed to be "black disks", and the beam area filling factor was assumed to be small. We have now generalized the technique to include clumps with an arbitrary central opacity and radial distribution, using as a framework the clumpy cloud model of Martin et al. (1984MNRAS.208...35M). We show how with this model, the smoothness of the observed profiles can be used to constrain the parameter space of the unresolved clumps. We also analyze the effect of an interclump medium on the profiles emerging from the clumpy cloud. We apply this technique to the case of two star forming regions, M17SW and Orion A, and find surprisingly different results.