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RATRAN: Radiative transfer and molecular excitation in one and two dimensions
Michiel Hogerheijde1 &
Floris van der Tak2
1Radio Astronomy Laboratory, Astronomy Department, University of California at Berkeley, USA
2Sterrewacht Leiden, The Netherlands
Abstract:
RATRAN is a computer code designed to calculate the radiative
transfer and excitation of molecular lines. Our approach is
based on the Monte Carlo method, and incorporates elements
from Accelerated Lambda Iteration. It combines the flexibility
of the former with the speed and accuracy of the latter.
Convergence problems known to plague Monte Carlo methods at
large optical depth (>100) are avoided by separating local
contributions to the radiation field from the overall transfer
problem. The random nature of the Monte Carlo method serves to
verify the independence of the solution to the angular,
spatial, and frequency sampling of the radiation field. This
allows our method to be used in a wide variety of astrophysical
problems without specific adaptations. Moreover, the code can
be applied to all atoms or molecules for which collisional rate
coefficients are available and any axially symmetric source
model. Continuum emission and absorption by dust is explicitly
taken into account but scattering is neglected. We expect this
program to be an important tool in analyzing data from present
and future infrared and (sub) millimeter telescopes.
Subject headings: ISM: molecules, line: formation,
methods: numerical, radiative transfer
Latest Version: 2000 August 15
Archived: 2000 August 15
Paper:
Hogerheijde, M. R. & van der Tak, Floris F. S., A&A, accepted
Language: Fortran 77
External Explanatory Pages:
http://astron.berkeley.edu/~michiel/ratran.html
Source Code:
ratran_public.tar.gz