Velocity shifts and differential broadening of radio recombination lines are used to estimate the densities and velocities of the ionized gas in several hypercompact and ultracompact H II regions. These small H II regions are thought to be at their earliest evolutionary phase and associated with the youngest massive stars. The observations suggest that these H II regions are characterized by high densities, supersonic flows, and steep density gradients, consistent with accretion and outflows that would be associated with the formation of massive stars.
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