Journal Article

Multifrequency, thermally coupled radiative transfer with <span class="smallCaps">traphic</span>: method and tests

Andreas H. Pawlik and Joop Schaye

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 412, issue 3, pages 1943-1964
Published in print April 2011 | ISSN: 0035-8711
Published online April 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.18032.x
Multifrequency, thermally coupled radiative transfer with traphic: method and tests

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We present an extension of traphic, the method for radiative transfer of ionizing radiation in smoothed particle hydrodynamics simulations that we introduced in Pawlik & Schaye. The new version keeps all advantages of the original implementation: photons are transported at the speed of light, in a photon-conserving manner, directly on the spatially adaptive, unstructured grid traced out by the particles, in a computation time that is independent of the number of radiation sources, and in parallel on distributed memory machines. We extend the method to include multiple frequencies, both hydrogen and helium, and to model the coupled evolution of the temperature and ionization balance. We test our methods by performing a set of simulations of increasing complexity and including a small cosmological reionization run. The results are in excellent agreement with exact solutions, where available, and also with results obtained with other codes if we make similar assumptions and account for differences in the atomic rates used. We use the new implementation to illustrate the differences between simulations that compute photoheating in the grey approximation and those that use multiple frequency bins. We show that close to ionizing sources the grey approximation asymptotes to the multifrequency result if photoheating rates are computed in the optically thin limit, but that the grey approximation breaks down everywhere if, as is often done, the optically thick limit is assumed.

Keywords: hydrodynamics; radiative transfer; methods: numerical; H ii regions; diffuse radiation; large-scale structure of Universe

Journal Article.  18157 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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