Light trapping by the dark matter

Abstract

Considering the dark matter as self-gravitating Bose-Einstein condensate in a gravito-chemical equilibrium state, we have studied the light trajectory through the halo. Found that depending on the initial direction cosine of the light ray, there are three types of trajectories: (a) the refracted light i.e. light which can refracts away from the halo to the out side, (b) the trapped light i.e. light that is trapped into the halo i.e. an observer, situated outside of the halo, can not observe it and (c) the reflected light: in this case the halo behaves as a perfect reflector to the outside light. The light trapping can introduce asymmetry in the observed spectrum and modify the apparent number of stars in a dark matter dominated galaxy.