Centrifugally driven winds from contracting molecular disks

We suggest that bipolar outflows in dense molecular clouds associated with young stellar objects are steady, centrifugally driven, hydromagnetic winds that arise from molecular disks (on scales < or =1016 cm) in which the infrared source(s) embedded. A disk of mass approx.100 M/sub sun/ and rotational speed of approx.106 cm s-1 provides a resevoir of 1047 ergs, which could power the most energetic outflows observed. Acceleration to supersonic speeds is accomplished by the magnetic field embedded in the disk (paralllel rotational and magnetic axes) and extending outward beyond the wind region to join the galactic field. The wind carries angular momentum and energy from the disk out to large distances. Our analysis treats the problem of magnetic braking and energy transport in a partially ionized (two-fluid) wind. The basic parameter which is shown to govern the flow is the coupling parameter β = T/sub n/-i/T/sub n/, the ratio of the characteristic neutral-ion collision time to flow time. A general analysis of angular momentum and energy transport is given, and the wind equation is solved along flux tubes in the strongly coupled (β<<1) limit. The centrifugally driven wind forms when an embedded protostar begins to ionize the disk core region. A disk envelope forms at the wind base at a pressure which adjusts to the wind requirements. Envelope heating may be maintained by magnetic flux loss from the dense core (which has a field approx.10-3 gauss) that is preferentially along the rotation axis for flattened disks. The structure of the field at the disk core surface is derived. The observational implications are discussed; in particular, we emphasize that such molecular disks with double profiles should be observed