HCN OBSERVATIONS OF THE CIRCUMNUCLEAR DISC IN THE GALACTIC-CENTER

We have studied the molecular part of the Galactic Centre circumnuclea r disc and its immediate environment using the J = 3-2 and J = 4-3 tra nsitions of HCN. In order to discuss the resemblance of the molecular material to a rotating ring of gas, we have modelled such a structure and fitted it to the observations. Our conclusions are that the north and south parts of the ring are independent, but show strong evidence for an underlying rotation structure. We found no conclusive evidence for connections from the ring to the nearby giant molecular clouds if the ring, + 50 and + 20 clouds do not all lie in the plane of the sky.