## 3. The radiative transfer codeFor the calculation of the continuum radiative transfer in 1D (spherical symmetry) and 2D (flared disk geometry) dust configurations, we used the code developed by Manske et al. (1997) which is based on the method given by Men'shchikov & Henning (1997). The main approximation used in this code is that even for the disk geometry, the density depends on the radial coordinate only. In addition, mean intensities and temperatures are self-consistently calculated for points in the disk's midplane and at its upper and lower conical surfaces only. The disk itself is essentially a part of a sphere with two removed polar cones (Fig. 6). A more detailed descriptions of the strategy for the solution of the radiative transfer problem can be found in our earlier papers mentioned above.
## 3.1. Implementation of quantum heatingIn the code, a ray tracing technique is used to solve the radiative
transfer equation. This means that this equation is reduced to a
1-dimensional equation (Eq. (14)), which has to be solved along rays
, with corresponding impact parameters Here where is the mean intensity,
is the Planck function and
is the temperature of the dust grains of the
chemically distinct dust component If the dust model contains small dust grains, so that the quantum heating method must be used to calculate the emission, the source function has to be modified in order to account for this effect: Here "small" means grains with radii Å and denotes the probabilities obtained by the quantum heating algorithm from Fig. 1. To illustrate the difficulties of considering quantum heated
particles in radiative transfer codes, note that it may take up to 25
seconds CPU time (on a DEC-Alpha 3000/500 workstation) to apply the
quantum heating algorithm (Fig. 1) for © European Southern Observatory (ESO) 1998 Online publication: August 6, 1998 |