The Molecular Accretion Flow in G10.6–0.4

We have observed the ultracompact H II region G10.6-0.4 with the VLA in the 23 GHz continuum and the NH3 (3, 3) inversion line. By analyzing the optical depth of the line as well as the kinematics, we have detected a flattened, rotating molecular accretion flow. We detect the fact that the highest column density gas is more flattened, that is, distributed more narrowly, than the lower column density gas, and that there is some inclination of the rotation axis. The rotation is sub-Keplerian, and the molecular gas is not in a rotationally supported disk. We do not find a single massive (proto-)star forming in a scaled-up version of low-mass star formation. Instead, our observations suggest a different mode of clustered massive star formation, in which the accretion flow flattens but does not form an accretion disk. Moreover, in this mode of star formation the central object can be a group of massive stars rather than a single massive star.