The Shapes of Dense Cores and Bok Globules

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Abstract
The shapes of isolated Bok globules and embedded dense cores of molecular clouds are analyzed using a nonparametric kernel method, assuming the alternate hypotheses that they are randomly oriented prolate objects or that they are randomly oriented oblate objects. In all cases, the prolate hypothesis gives a better fit to the data. If Bok globules are oblate spheroids, they must be very flattened; the average axis ratio is [gamma] approximate to 0.3, and no globules can have gamma greater than or similar to 0.7. If Bok globules are prolate, their intrinsic flattening is not as great, with a mean axis ratio [gamma] approximate to 0.5. For most data samples of dense cores embedded within molecular clouds, the randomly oriented oblate hypothesis can be rejected at the 99% one-sided confidence level. If the dense cores are prolate, their mean axis ratio is in the range [gamma] = 0.4-0.5. Analysis of the data of Nozawa et al. reveals that dense cores are significantly different in shape from the clouds in which they are embedded. The shapes of dense cores are consistent with their being moderately flattened prolate spheroids; clouds have flatter apparent shapes and are statistically inconsistent with a population of axisymmetric objects viewed at random angles.
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