Internal Dynamics of the Hypercompact H II Region G28.20-0.04N
  High resolution (0.15") Very Large Array observations of 7 mm continuum and H53a line emission toward the hypercompact H II region G28.20-0.04N reveal the presence of large-scale ordered motions. We find a velocity gradient of 1000 km/s/pc along the minor axis of the continuum source. Lower resolution (1.0"-2.3") radio recombination line observations indicate a systematic increase of line width from H30alpha to H92alpha. Under the assumption that the H30alpha line does not suffer significant pressure broadening, we have deconvolved the contributions of statistical broadening (thermal, turbulent, and pressure) from large-scale motions. The pressure broadening of the H53alpha, H76alpha, and H92alpha lines implies an electron density of 6.9E+06, 8.5E+05, and 2.8E+05 cm^(-3), respectively. 
M. Sewilo (1), E. Churchwell (2), S. Kurtz (3), W. M. Goss (4), P.   Hofner (4,5) ((1) Space Telescope Science Institute, Ba...