We investigate the Ly \alpha line transfer in nearby and high redshift starbursting galaxies , where the effects of high optical depths and the role of dust in the scattering medium are expected to be conspicuous and should be treated in a very careful manner .
We present our first results in a dustless , static , and uniform H i media with moderate Ly \alpha line center optical depths \tau _ { 0 } = 10 ^ { 3 - 6 } .
We assume the temperatures of the media to be T = 10 ^ { 1 - 4 } { K } , and use a Monte Carlo technique .
We investigate the basic processes of the line transfer and confirm the criterion of a \tau _ { 0 } > 10 ^ { 3 } for the validity of the diffusion approximation suggested by Neufeld in 1990 , where a is the Voigt parameter .
Adopting the model for evolution of a galactic supershell suggested by Tenorio-Tagle et al. , we performed calculations on the Ly \alpha line formation for each evolutionary stage of an expanding supershell .
The emergent Ly \alpha profiles are characterized by the double peaks and the absorption trough at the line center .
We found that the absorption troughs expected in most of the evolutionary stages are not wide enough to be observed with current instruments .
However , the absorption trough in the Ly \alpha emission profile from an expanding recombining supershell can be marginally detected .