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3D-PDR: a new three-dimensional astrochemistry code for treating photodissociation regions

Bisbas, T; Bell, T; Viti, S; Yates, J; Barlow, M; (2012) 3D-PDR: a new three-dimensional astrochemistry code for treating photodissociation regions. Monthly Notices of the Royal Astronomical Society , 427 (3) 2100 - 2118. 10.1111/j.1365-2966.2012.22077.x. Green open access

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Abstract

Photodissociation regions (PDRs) define the transition zone between an ionized and a dark molecular region. They consist of neutral gas which interacts with far-ultraviolet radiation and are characterized by strong infrared line emission. Various numerical codes treating one-dimensional PDRs have been developed in the past, simulating the complexity of chemical reactions occurring and providing a better understanding of the structure of a PDR. In this paper we present the three-dimensional code, 3D-PDR, which can treat PDRs of arbitrary density distribution. The code solves the chemistry and the thermal balance self-consistently within a given three-dimensional cloud. It calculates the total heating and cooling functions at any point in a given PDR by adopting an escape probability method. It uses a HEALPIx-based ray tracing scheme to evaluate the attenuation of the far-ultraviolet radiation in the PDR and the propagation of the far-infrared/submm line emission out of the PDR. We present benchmarking results and apply 3D-PDR to (i) a uniform-density spherical cloud interacting with a plane-parallel external radiation field, (ii) a uniform-density spherical cloud interacting with a two-component external radiation field and (iii) a cometary globule interacting with a plane-parallel external radiation field. We find that the code is able to reproduce the benchmarking results of various other one-dimensional numerical codes treating PDRs. We also find that the accurate treatment of the radiation field in the fully three-dimensional treatment of PDRs can in some cases leads to different results when compared to a standard one-dimensional treatment.

Type: Article
Title: 3D-PDR: a new three-dimensional astrochemistry code for treating photodissociation regions
Open access status: An open access version is available from UCL Discovery
DOI: 10.1111/j.1365-2966.2012.22077.x
Publisher version: http://dx.doi.org/10.1111/j.1365-2966.2012.22077.x
Language: English
Additional information: © 2012 RAS Definitive versions of articles pre-2013 are available at http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2966, now published by http://mnras.oxfordjournals.org
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1383436
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