A Dusty ring in the Coalsack: A dense core caught in the act of formation?

We propose to obtain molecular line maps of the most opaque molecular globule in the Coalsack complex, G2. Using deep near-IR observations, we have discovered a strong central ring of dust column density within the globule. This ring represents a region of high density and pressure that is likely a transient structure. A single SEST C18O (2-1) spectrum toward the center of the ring reveals a complex line profile that most likely results from turbulence. We suggest that the dense ring is in the process of transforming into a more centrally condensed state, similar to that of typical Bok globules and dense star-forming cores. We propose to use Mopra to obtain a C18O (1-0) map across the dense ring and a 13CO (1-0) map of the surrounding lower-density envelope. The spatial variation of the C18O linewidths across the ring, will reveal whether or not the dense ring is indeed in a very early evolutionary stage of star formation.