Radio and millimeter-wave studies of molecular gas around protostars are revealing the details of circumstellar disk and envelope kinematics associated with star formation. I will present the latest interferometric results with examples of disk rotation, gravitational infall, and collimated jets and outflows around protostars.

Flattened disk-like envelopes, several thousand AU in diameter, have been found around the sources of several protostellar jets. We have found evidence for rotating gas disks around very young low-mass sources (e.g. HH 212, HH 211) and also around intermediate mass systems (e.g. HH 111). We find that the rotation curves tend to indicate the evolutionary stage of the embedded protostars. The youngest sources often have rotation curves that are rigid rather than Keplerian, indicating that most of the mass in the system is not yet centrally condensed and has not yet accreted onto the central protostar. Both rotation and infall have been detected spectroscopically and differentiated, even in dense gas cores where no stellar source has yet formed.

I will compare the kinematics and distribution of infalling and rotating circumstellar gas with the dynamics of associated optical, infrared, and radio jets. In the spectacular case of the jet HH 212, recent spectroscopic results show evidence of jet rotation (Davis et al. 2000), and this rotation matches the rotational motion we find in our VLA maps of the molecular gas disk surrounding the young embedded protostellar source. Thus we are now seeing observational evidence that protostellar jets carry away angular momentum from infalling material, allowing central accretion and star formation.