DENSE CORES IN DARK CLOUDS .9. OBSERVATIONS OF (CO)-C-13 AND (CO)-O-18 IN VELA, CHAMELEON, MUSCA, AND THE COALSACK

One hundred one condensations with average optical size less than 7' a nd visual extinction greater than 2.5 mag have been selected from ESO J plates, extinction maps, and catalogs of southern hemisphere dark cl ouds for observation in the (CO)-C-13 and (CO)-C-18 J = 1-0 transition s. These regions are condensations in the dark molecular clouds Musca, Coalsack, Chamaeleon II, Chamaeleon III, and cometary globules in Vel a and Gum nebula. A search for IRAS point sources having colors of you ng stellar objects shows that these condensations have at most seven a ssociated young stellar objects-far fewer than in Taurus and Ophiuchus . These 101 condensations generally have lower (CO)-C-13 and (CO)-C-18 line intensity, (CO)-O-18 optical depth, and (CO)-C-13 line width tha n do 90 condensations in Taurus, Ophiuchus, and Cepheus. Similarly, 47 of these southern condensations having star-count estimates of visual extinction generally have less extinction than do the 19 condensation s in Taurus having extinction estimated by the same method. The (CO)-O -18 to (CO)-C-13 line-width ratio for the cometary globules in the Vel a region is greater than for the other clouds, indicating that the (CO )-C-13 line width observed toward dark cloud condensations is related to the more extended and less dense intercondensation gas. Radial velo cities suggest that the system of Vela globules has velocity dispersio n 4.7 km s-1, which is at least 2 times greater than the dispersion de termined from formaldehyde observations. The Musca filament has veloci ties which are slightly higher-by approximately 0.5 km s-1-in the cent er than at the ends of the filament. Chamaeleon III has a 0.2 km s-1 p c-1 velocity gradient, and Chamaeleon II has no indication of velocity gradients. The Chamaeleon clouds and the Musca filament appear close to virial equilibrium.