A theoretical study of the radio recombination line and continuum emission from compact inhomogeneous H II regions
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Abstract
We have developed a numerical code for the calculation of continuum and recombination line emission from spherically symmetric H II regions with radial variations in electron density, temperature, velocity, and turbulence, using the full non-LTE recombination line theory, including the effects of inelastic electron collisions (pressure broadening). The code is used to study the effects of radial variation of physical parameters on line profiles, to calculate the effects of a uniform brightness background on the line emission from an H II region, and to compare H and He lines in a model nebula. Analytical treatment of a uniform slab is used to find functional relations between line profiles and physical parameters in order to understand the results of the numerical calculations. Application of the code to published data on NGC 7027 leads to the determination of the density gradient in the shell of the planetary nebula.