Figure 3.9 The ratio of the bulk kinetic energy T to the gravitational potential energy \W\ for molecular clouds, plotted as a function of the cloud diameter L.

even more massive dark clouds exist. The Taurus-Auriga system described in Chapter 1 and the well-studied p Ophiuchi region are two prime examples. Yet another at roughly the same distance is Corona Australis in the Southern hemisphere. Though differing morphologically from each other, all have mean densities similar to the clumps, but total masses closer to 104 Me. We shall term such objects dark cloud complexes. While accounting for a significant fraction of Galactic star formation, it is noteworthy that they do not produce the OB associations that are a hallmark of the more massive systems. On the other hand, complexes such as p Ophiuchi do contain regions with peak AV-values of order 100. Such locales always harbor a multitude of embedded young stars.

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