INFALL AND ROTATION MOTIONS IN THE HH 111 PROTOSTELLAR SYSTEM: A FLATTENED ENVELOPE IN TRANSITION TO A DISK?

We have mapped the central region of the HH 111 protostellar system in 1.33 mm continuum, (CO)-O-18 (J = 2-1), (CO)-C-13 (J = 2-1), and SO (N-J = 5(6)-4(5)) emissions at similar to 3 '' resolution with the Submillimeter Array. There are two sources, VLA 1 (= IRAS 05491+0247) and VLA 2, with the VLA 1 source driving the HH111 jet. Thermal emission is seen in 1.33 mm continuum tracing the dust in the envelope and the putative disks around the sources. A flattened, toruslike envelope is seen in (CO)-O-18 and (CO)-C-13 around the VLA 1 source surrounding the dust lane perpendicular to the jet axis, with an inner radius of similar to 400 AU (1 ''),an outer radius of similar to 3200 AU (8 ''), and a thickness of similar to 1000 AU (2 ''.5). It seems to be infalling toward the center with the conservation of specific angular momentum rather than with a Keplerian rotation as assumed by Yang et al. An inner envelope is seen in SO, with a radius of similar to 500 AU (1 ''.3). The inner part of this inner envelope, which is spatially coincident with the dust lane, seems to have a differential rotation and thus may have formed a rotationally supported disk. The outer part of this inner envelope, however, may have a rotation velocity decreasing toward the center and thus represent a region where an infalling envelope is in transition to a rotationally supported disk. A brief comparison with a collapsing model suggests that the flattened, toruslike envelope seen in (CO)-O-18 and (CO)-C-13 could result from a collapse of a magnetized rotating toroid.