Radiation Transfer Models in Galaxies
  The dust in galaxies makes radiation transport calculations in them absolutely necessary. It is not only common practice in Astrophysics, but also wisdom, to try to make as simple models as possible to simulate physical systems. For spiral galaxies, however, this turned out to be catastrophic. For years, the major question of the opacity of spiral galaxies kept the community divided, because the models were too simple. A spiral galaxy appears, to first order, to have exponential distributions of stars and dust, which cannot be approximated with uniform distributions. We will review the radiative transfer methods used in galaxies and we will comment on their pluses and minuses. We will also present some of the main results of the application of one of the methods to the observations. 
N. D. Kylafis, E. M. Xilouris