Radio Recombination Lines from Compact HII Regions
We compile measurements made with high angular resolution of the H76α line and radio continuum emission from over thirty compact HII regions. The aim was to investigate global trends exhibited by the observed and derived parameters and to provide explanations for the tendencies in terms of the physical conditions of the ionized gas. The line widths of compact HII regions are considerably broader than those of diffuse regions. We conclude that the large widths are due to turbulent motions produced by the progressive ionization of a magnetized and inhomogeneous medium around a newly formed star. The line to continuum ratios are spread over a much wider range than that span by extended regions. We show that the large ratios are due to line enhancement by stimulated emission, while the small ones can be attributed to line suppression in regions with large continuum opacities.
KeywordsMolecular Cloud Diffuse Region High Angular Resolution Doppler Width Peak Line
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