The dynamics of the envelope surrounding the protostar HH 211 mm

Abstract

We present a study of the structure and dynamics of the dense gas surrounding the HH 211 mm source, using Very Large Array (VLA) observations of the ammonia (1,1) and (2,2) inversion transitions. We find that the envelope around this Class 0 source has an elongated geometry, extending about 10 4 AU in the direction perpendicular to the well-known HH 211 jet, and exhibits a velocity distribution consistent with rotation along the major axis. Our VLA observations indicate that the envelope is mostly in virial equilibrium. However, comparing our data with results from previous studies, it appears that the gas within approximately 0.005 pc of the central protostar is undergoing dynamical collapse. The size of this collapsing radius may constrain the amount of mass that can eventually infall into the forming star. We also find that the envelope is mostly internally heated, most probably by radiation from the central protostar. In addition, we detect evidence of outflow-envelope interaction in the ammonia data. These include a velocity gradient in the dense gas along the outflow axis and significant line broadening that is spatially correlated with the jet and could be the result of outflow-induced turbulence in the envelope. © 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.