GIANT MOLECULAR CLOUD COMPLEXES WITH OPTICAL H-II REGIONS - (CO)-C-12AND (CO)-C-13 OBSERVATIONS AND GLOBAL CLOUD PROPERTIES

Images of (CO)-C-12 and (CO)-C-13 J = 1-0 emission from the molecular clouds associated with the optical H II regions Sh 155, Sh 235, and Sh 140 are presented to better understand the interstellar gas condition s associated with regions of massive star formation. In the vicinity o f the H II regions, there is evidence for the compression of ambient m olecular material from shocks associated with the expansion of the ion ized gas component and the near complete photoionization or photodisso ciation of molecular material within the H II region. However, the ima ges also show that most of the molecular mass of the clouds resides wi thin the extended, low column density regions well removed from the lo calized sites of star formation. Each cloud is characterized by a glob al line width which is dominated by the relative motions between resol ved cloud substructures rather than motions along the line of sight in ferred from individual profile line widths. We identify a relationship of the observed profile line widths with molecular gas column density which is consistent with opacity broadening of an intrinsic line widt h nearly independent with column density. Thus any tendency for neighb oring emitting components to be at the same velocity (i.e., spatial co herence to the velocity field) must be weak or absent within GO-emitti ng regions of these clouds. In the context of a clumpy cloud medium, w e use the variations of profile line width and antenna temperature wit h column density to derive the following limits for clump properties: clump masses less than 0.01 M., clump sizes less than 4 x 10(16) cm, a nd clump volume densities greater than 1 x 10(4) cm-3.