Rotation in the Protostellar Envelopes around IRAS 04169+2702 and IRAS 04365+2535: The Size Scale for Dynamical Collapse

Abstract

We report interferometric observations of two embedded protostar candidates, IRAS 04169+2702 and IRAS 04365+2535 (TMC-1A), in the Taurus molecular cloud. The C18O J = 1-0 emission from IRAS 04169+2702 reveals a flattened envelope 2200 AU × 1100 AU in size; there is a velocity gradient along the elongation axis, which in turn is perpendicular to the outflow direction. Since the rotational velocity corrected for inclination, 0.23 km s-1 at 370 AU, gives an unacceptably small dynamical mass of 0.02 M☉ within that radius, we speculate that there is additional radial motion, possibly infall, in the flattened envelope. Around IRAS 04365+2535, a compact 13CO J = 1-0 condensation ~1400 AU in size was detected. Again, the velocity gradient is perpendicular to the associated molecular outflow, but a rotation velocity of 0.87 km s-1 at 580 AU radius is consistent with the condensation being a rotationally supported disk.