Radiative transfer problem in dusty galaxies: effects of non-isotropic multiple scattering

Abstract

We investigate the effects of multiple anisotropic light scattering by interstellar dust particles on photometric profiles of disk galaxy models computed using an iterative ray-tracing radiative transfer modeling code. It is shown that anisotropic scattering must be fully accounted for in at least the first scattering event for all considered cases. At the same time scattering terms of the order higher than 5th can be safely approximated using the isotropic phase function. The effects of isotropic approximation are most significant in the galaxy models seen face-on with dust population extending beyond the stellar disk, therefore the applicability of isotropic approximation to a higher-order (2 to 5) scattering terms depends on the assumed galaxy model parameters, namely, the optical depth, scattering albedo and the distribution of interstellar dust with respect to stars.