The Dynamics of Molecular Clouds

The nature and sources of internal turbulent motions observed in molecular clouds (MCs) may control the evolution and lifetime of the clouds. Observations suggest approximate equipartition between the gravitational and kinetic energies within MCs (virial equilibrium). Numerical simulations show strong dissipation of the turbulent energy in shock waves. Here we develop an analytical model of MCs in which the observed supersonic turbulent motions are driven by gravitational instability. Shock dissipation is taken into account in an approximate way. If the dissipation is substantial, the model is consistent with the observed scaling relations between length, mass and velocity dispersion.