Internal Dynamics of the Hypercompact H II Region G28.20-0.04N

TL;DR

This study uses high-resolution radio observations to analyze the internal motions and electron density of the hypercompact H II region G28.20-0.04N, revealing ordered large-scale motions and detailed density estimates.

Contribution

It provides the first detailed analysis of large-scale ordered motions and electron densities in G28.20-0.04N using multi-frequency radio recombination lines.

Findings

Detected a velocity gradient of 1000 km/s/pc along the minor axis.

Observed increase in line width from H30alpha to H92alpha.

Estimated electron densities ranging from 2.8E+05 to 6.9E+06 cm^-3.

Abstract

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.