Dynamical state of molecular gas in the galaxy

Observed correlations between linewidths and the characteristic size of the radiating region of molecular clouds, as well as the extremely weak dependence of their surface density on the cloud size, are usually interpreted as evidence that the molecular clouds in the galaxy are in a virial state. In this paper it is argued that no more than 30% of the molecular gas in the galaxy can be in a virial equilibrium. Possible alternative reasons for the observed correlations are discussed. It is argued that the mass of molecular gas which is not in virial equilibrium may be greatly underestimated because of its low surface density and a reduced concentration of CO molecules.