The decrease of specific angular momentum and the hot toroid formation: The massive clump G10.6-0.4

Abstract

This is the first paper of our series of high-resolution (1′′) studies of the massive star-forming region G10.6-0.4. We present the emission line observations of the hot core type tracers (O13CS, OCS, SO 2) with ~0′′.5 resolution. By comparing the results to the high-resolution NH3 absorption line observation, we confirm for the first time the rotationally flattened hot toroid in the central <0.1 pc region, which has a rotational axis perpendicular to its geometrical major axis. In addition, we present the observations of NH3, 13CS, and CH3CN with ~1′′ resolution, and follow the dynamics of the molecular accretion flow from the 0.3 pc radius to the inner 0.03 pc radius. With reference to the rotational axis of the hot toroid, we measure the rotational velocity from the molecular emission in the region. The results are consistent with an envelope with a rapid decrease of the specific angular momentum from the outer to the inner region. These new results improve the current understanding of the molecular accretion flow in an ultracompact Hii region created by the embedded O-type cluster. © 2010. The American Astronomical Society. All rights reserved.