A Change of Rotation Profile in the Envelope in the HH 111 Protostellar System: A Transition to a Disk?

The HH 111 protostellar system consists of two Class I sources (VLA 1 and 2) with putative disks deeply embedded in a flattened envelope at a distance of 400 pc. Here is a follow-up study of this system in C18O (J=2-1), SO (N_J = 5_6-4_5), and 1.33 mm continuum at ~ 1" (400 AU) resolution, and it may show for the first time how a rotationally supported disk can be formed inside an infalling envelope. The 1.33 mm continuum emission is seen arisen from both sources, likely tracing the dusty putative disks around them. In particular, the emission around the VLA 1 source is elongated in the equatorial plane with a radius of ~ 300 AU. The envelope is well seen in C18O, extending to ~ 7000 AU out from the VLA 1 source, with the innermost part overlapping with the dusty disk. It has a differential rotation, with the outer part (~ 2000-7000 AU) better described by a rotation that has constant specific angular momentum and the inner part (~ 60-2000 AU) by a Keplerian rotation. The envelope seems to also have some infall motion that is smaller than the rotation motion. Thus, the material in the outer part of the envelope seems to be slowly spiraling inward with its angular momentum and the rotation can indeed become Keplerian in the inner part. A compact SO emission is seen around the VLA 1 source with a radius of ~ 400 AU and it may trace a shock such as an (inner) accretion shock around the disk.