An Ionized Accretion Flow in the Ultracompact H ii Region G10.6−0.4

Analysis of the H66α radio recombination line velocities in the ultracompact H II region G10.6-0.4 indicates inward motion of the ionized gas within the H II region. Comparison with the velocities of molecular lines from the surrounding neutral gas suggests that a molecular accretion flow passes through the ionization boundary of the H II region and continues inward as an ionized accretion flow. Interpreted in the context of a model for star formation in hot molecular cores, these observations indicate that G10.6-0.4 is at a stage of development just after the massive star or stars at the center of the accretion flow have first formed an ionized H II region within the hot molecular core.