Open Accessmocassin : a fully three‐dimensional Monte Carlo photoionization code
Author(s) -
Ercolano B.,
Barlow M. J.,
Storey P. J.,
Liu X.W.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06371.x
Subject(s) - physics , photoionization , radiative transfer , monte carlo method , circular symmetry , stars , astrophysics , code (set theory) , symmetry (geometry) , planetary nebula , computational physics , ionization , optics , classical mechanics , quantum mechanics , geometry , ion , programming language , statistics , mathematics , set (abstract data type) , computer science
The study of photoionized environments is fundamental to many astrophysical problems. Up to the present most photoionization codes have numerically solved the equations of radiative transfer by making the extreme simplifying assumption of spherical symmetry. Unfortunately very few real astronomical nebulae satisfy this requirement. To remedy these shortcomings, a self‐consistent, three‐dimensional radiative transfer code has been developed using Monte Carlo techniques. The code, mocassin , is designed to build realistic models of photoionized nebulae having arbitrary geometry and density distributions, with both the stellar and diffuse radiation fields treated self‐consistently. In addition, the code is capable of treating one or more exciting stars located at non‐central locations. The gaseous region is approximated by a cuboidal Cartesian grid composed of numerous cells. The physical conditions within each grid cell are determined by solving the thermal equilibrium and ionization balance equations. This requires a knowledge of the local primary and secondary radiation fields, which are calculated self‐consistently by locally simulating the individual processes of ionization and recombination. The structure and the computational methods used in the mocassin code are described in this paper. mocassin has been benchmarked against established one‐dimensional spherically symmetric codes for a number of standard cases, as defined by the Lexington/Meudon photoionization workshops: at Meudon in 1985 and at Lexington in 1995 and 2000. The results obtained for the benchmark cases are satisfactory and are presented in this paper. A performance analysis has also been carried out and is discussed here.