2008ApJ...681..350S

High-resolution (0.15") Very Large Array observations of 7 mm continuum and H53α 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 10³ 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 H30α to H92α. Under the assumption that the H30α 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 H53α, H76α, and H92α lines implies an electron density of 7x10⁶, 9x10⁵, and 3x10⁵/cm3, respectively.