Radiative transfer in molecular lines Main-Page
Toren Academiegebouw

Molecular lines are excellent probes of the physical and chemical conditions in interstellar clouds, PDRs, protostellar envelopes, circumstellar shells around AGB stars etc. However a good and self-consistent interpretation of such lines often relies heavily on the use of sophisticated line radiative transfer programs.

Radiative transfer codes are not straight-forward and are often plagued by convergence uncertainties, sampling errors and gridding problems. These errors can easily remain unnoticed because it is difficult to predict beforehand what the solution of a complicated multi-level, non-LTE molecular excitation problem is.

This page is intended to help scientists working on such programs. Pre-defined test-cases, including molecular data-files, provide an opportunity to test the codes against others.

1 Enable scientists to test and debug their codes
2 Comparison of many different programs

Discussion on various problems: (Convergence / including dust / including maser transitions)

Reveal the strong and weak points of the various methods.

The pre-defined test-cases can be found by clicking on test problems (see left frame). For each problem given, there are three options: first: the problem can be downloaded. The file is in a tar format and includes a README file, the problem itself, the molecular datafile to be used and a few fortran codes enabling you to read the molecular data-file. Second: the results available to date can be viewed on screen. Third: the results available so far can be down-loaded. We would appreciate it very much if users send their results to radtrans@strw.leidenuniv.nl. The results will be discussed with the author before they are added on to the web-page.

A paper discussing these problems, and comparing the results of as many as eight independent codes, has recently been accepted for publication in Astronomy & Astrophysics. The paper can be downloaded here [PostScript file]. The present web page will be updated by the end of September 2002 to include all results from that paper.