Constraints on the Formation and Evolution of Circumstellar Disks in Rotating Magnetized Cloud Cores

Abstract

We use magnetic collapse models to place some constraints on the formation and angular momentum evolution of circumstellar disks that are embedded in magnetized cloud cores. Previous models have shown that the early evolution of a magnetized cloud core is governed by ambipolar di usion and magnetic braking, and that the core takes the form of a nonequilibrium attened envelope that ultimately collapses dynamically to form a protostar. In this paper, we focus on the inner centrifugally supported disk, which is formed only after a central protostar exists, and grows by dynamical accretion from the attened envelope. We estimate a centrifugal radius for the collapse of mass shells within a rotating, magnetized cloud core. The centrifugal radius of the inner disk is related to its mass through two important parameters characterizing the background medium : the background rotation rate and the ) b background magnetic eld strength