3D-PDR: a new three-dimensional astrochemistry code for treating photodissociation regions
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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2012
- DOI:
- 10.1111/j.1365-2966.2012.22077.x
- arXiv:
- arXiv:1209.1091
- Bibcode:
- 2012MNRAS.427.2100B
- Keywords:
-
- astrochemistry;
- radiative transfer;
- methods: numerical;
- ISM: abundances;
- photodissociation region (PDR);
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 19 pages, 11 figures, accepted for publication in MNRAS