Radiation transport in dense interstellar dust clouds. I - Grain temperature

Abstract

A numerical method for solving the problem of radiation transport in dense interstellar dust clouds (DIDC) as a two-point boundary value problem is presented. By the introduction of two auxiliary functions - the anisotropy factor, describing the anisotropy of the radiation field, and the configuration function, which depends on the geometry of the problem and on the anisotropy function - the equation of radiation transport is transformed into a quasi-diffusion form valid for planar, spherical, and cylindrical geometries. The method is applied to silicon carbide, graphite, silicate, and the corresponding ice-coated core-mantle grain models. It is found in general that a very large change in the radiation field is required to produce a small change in grain temperature. It appears that radiation pressure exerted by interstellar radiation field not only helps confine DIDC but may even help in their initial collapse, provided there is mechanical coupling between the gas and dust.