Molecular gas in cometary globules: CG4 and CG 6 in the GUM Nebula.

With the SEST telescope, we observed ^12^CO(10,->^13^)CO(10,->and) C^18^O(10)->emission from the cometary globules CG4 and CG6 in the Gum Nebula and also CS(21->and) HCO^+^(10->in) CG4. There are =~50M_sun_ and =~5.5M_sun_ of molecular hydrogen, respectively, in CG4 and CG6. The gas kinetic temperature is =~16K in both globules. The gas kinematics indicate the globules are strongly affected by ionization fronts on their surfaces. Red and blue line wings are found throughout CG4 and the velocity gradients suggest a divergent flow that may be responsible for the apparent disruption of the globule's head. In CG6, a head to tail velocity gradient indicates a dynamical age of 10^6^yr. We discuss a possible evolution scenario for these globules.