Formation of the Hydrogen Lyman α Line in Expanding Spherical Nebulae with Dust

Abstract

The radiation field in the hydrogen Ly α line is calculated for a dust filled spherical gaseous nebula. It is assumed that the nebula with a ratio of inner to outer radius of 3.3 has an optical depth at the line center of about 1000 and is either static or expands uniformly with 26km's/sup-1. For the solution of the radiative transfer equation the discrete space theory with partial redistribution is used. It is found that the dust gives only rise to small changes if it purely scatters. However, if it absorbs it is very effective in reducing the mean intensities J in the line whole nebula, e.g. for an optical depth in the dust of ґ=1 decreases J by about a factor of 7. the results also show that for dust filed nebulae the effects of velocities are of minor importance in current to dust free configurations.