2 ‐ D ust : A Dust Radiative Transfer Code for an Axisymmetric System

Abstract

We have developed a general purpose dust radiative transfer code for an axisymmetric system, 2-DUST, motivated by the recent increasing availability of high-resolution images of circumstellar dust shells at various wavelengths. This code solves the equation of radiative transfer following the principle of long characteristic in a two-dimensional polar grid while considering a three-dimensional radiation field at each grid point. A solution is sought through an iterative scheme in which self-consistency of the solution is achieved by requiring a global luminosity constancy throughout the shell. The dust opacities are calculated through Mie theory from the given size distribution and optical properties of the dust grains. The main focus of the code is to obtain insights on (1) the global energetics of dust grains in the shell and (2) the two-dimensional projected morphologies that are strongly dependent on the mixed effects of the axisymmetric dust distribution and inclination angle of the shell. Here test models are presented with discussion of the results. The code can be supplied with a user-defined density distribution function and, thus, is applicable to a variety of dusty astronomical objects possessing the axisymmetric geometry.