Dynamic structure of dark molecular clouds

Theoretical CO line profiles are calculated for dark molecular clouds in the case where the cloud is resolved. Assuming that the density and velocity structure of the cloud can be approximated by power laws, both crude analytical and detailed numerical calculations indicate that realistic profiles can be produced only under certain restricted combinations of density and velocity laws. The probable presence of density gradients implies that interpretation of CO profiles on the basis of the assumption of uniform density can lead to serious errors in the estimate of cloud masses. It is suggested that dark clouds and molecular clouds associated with H II regions may represent two consecutive evolutionary stages of stellar formation and that L134 is in the process of evolving from the former to the latter