2002/08/29 by Gerd‐Jan van Zadelhoff, G. -J. van Zadelhoff, C. P. Dullemond +11 · 1 citation
Chemistry · Earth and Planetary Sciences · Mathematics · Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Atmospheric radiative transfer codes #Computational physics #Computer science #Convergence (economics) #Envelope (radar) #Geometry #Line (geometry) #Mathematics #Molecular cloud #Optics #Physics #Population #RADIUS #Radiative transfer #Spectroscopy and Laser Applications #Telecommunications #astro-ph
paper · pdf · doi:10.1051/0004-6361:20021226
published as Astron.Astrophys. 395 (2002) 373 · Accepted for publication in A&A
arxiv created 2002/08/29 · openalex publication_date 2002/10/29 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Comparison is made between a number of independent computer programs for radiative transfer in molecular rotational lines. The test models are spherically symmetric circumstellar envelopes with a given density and temperature profile. The first two test models have a simple power law density distribution, constant temperature and a fictive 2-level molecule, while the other two test models consist of an inside-out collapsing envelope observed in rotational transitions of HCO+. For the 2-level molecule test problems all codes agree well to within 0.2%, comparable to the accuracy of the individual codes, for low optical depth and up to 2% for high optical depths (). The problem of the collapsing cloud in HCO+ has a larger spread in results, ranging up to 12% for the population. The spread is largest at the radius where the transition from collisional to radiative excitation occurs. The resulting line profiles for the HCO+ –3 transition agree to within 10%, i.e., within the calibration accuracy of most current telescopes. The comparison project and the results described in this paper provide a benchmark for future code development, and give an indication of the typical accuracy of present day calculations of molecular line transfer.