Broad emission4ine profiles from diverse astronomical objects have been interpreted as due to rapid radial outflows of matter. Estimates of characteristic electron densities lead to the conclusion that the effect of electron scattering on the line profiles may be substantial. A Monte Carlo method is employed to treat the transfer of radiation through an expanding envelope of comoving electrons and ions. Two models are considered: one with a constant velocity of outflow, and one in which the velocity increases linearly with radius. A spectral line is formed by recombination, and the only opacity is that due to free electrons. For electron-scattering optical depths of order unity, very extensive wings to the red of line center are formed in all cases. These results are applied to models of Woif-Rayet stars and Seyfert galaxies.
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Auer et al. (1972) studied this question.