Angular Momentum Transfer in Dynamically Collapsing Gaseous Disks

Abstract

We investigate the angular momentum transfer in dynamically collapsing gaseous disks by using self-similar solutions for self-gravitating viscous disks. As for the mechanisms of angular momentum transfer, the turbulent viscosity and the gravitational torque are considered. We solved the self-similar equations to examine the effects of the angular momentum transfer in the disks in the runaway collapse phase, when a central core is not yet formed. As a result, the angular momentum transfer makes remarkable differences in rotational velocity distributions as compared with that of the disk with no angular momentum redistribution. In contrast, the distributions of surface density and infall velocity do not vary significantly, since the effect of the centrifugal force is small in this phase. Also, we find that the angular momentum transfer by gravitational torque tends to work more effectively than that due to turbulent viscosity. This is because the magnitude of effective viscosity of gravitational torque is superior to that of turbulent viscosity if the disk is unstable against self-gravity, which is satisfied in the disks in the runaway collapse phase. Finally, we discuss the angular momentum transfer in star-forming disk. From our estimations, we conclude that only a little angular momentum of the disk is transferred in the runaway phase compared with accretion phase before the classical T Tauri star formation. Meanwhile, the first core formation is significantly affected by the angular momentum redistribution in the runaway phase.