Note on the collapse of magnetic interstellar clouds

Virial-theorem expressions for clouds on the verge of gravitational collapse are fitted to numerical values obtained with exact equilibrium computations for magnetic interstellar isothermal clouds subject to the pressure of the intercloud medium. The minimum mass needed for gravitational collapse is 0.53 times the virial-theorem value obtained for a homogeneous magnetic sphere, while the maximum external pressure, Pm, at which equilibrium is possible is 0.60 times the virial-theorem value. Subject heading: interstellar: magnetic fields