Implementation of Chemistry in the Athena++ Code

Chemistry plays a key role in many aspects of astrophysical fluids. Atoms and molecules are agents for heating and cooling, determine the ionization fraction, serve as observational tracers, and build the molecular foundation of life. We present the implementation of a chemistry module in the public...

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Bibliographic Details
Published in:The Astrophysical journal. Supplement series 2023-10, Vol.268 (2), p.42
Main Authors: Gong, Munan, Ho, Ka Wai, Stone, James M., Ostriker, Eve C., Caselli, Paola, Grassi, Tommaso, Kim, Chang-Goo, Kim, Jeong-Gyu, Halevi, Goni
Format: Article
Language:English
Subjects:
Astrochemistry
astronomy
ASTRONOMY AND ASTROPHYSICS
astrophysics
Chemistry
Cooling
Cosmic ray ionization
Cosmic rays
Coupling (molecular)
Differential equations
Exact solutions
Fluid flow
Gas dynamics
Heating
Heating and cooling
Interstellar chemistry
Interstellar matter
Interstellar medium
Ionization
Magnetohydrodynamical simulations
Ordinary differential equations
Photodissociation
Robustness (mathematics)
Simulation
Tracers
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Summary:Chemistry plays a key role in many aspects of astrophysical fluids. Atoms and molecules are agents for heating and cooling, determine the ionization fraction, serve as observational tracers, and build the molecular foundation of life. We present the implementation of a chemistry module in the publicly available magnetohydrodynamic code Athena++ . We implement several chemical networks and heating and cooling processes suitable for simulating the interstellar medium (ISM). A general chemical network framework in the KIDA format is also included, allowing users to easily implement their own chemistry. Radiation transfer and cosmic-ray ionization are coupled with chemistry and solved with the simple six-ray approximation. The chemical and thermal processes are evolved as a system of coupled ordinary differential equations with an implicit solver from the CVODE library. We perform and present a series of tests to ensure the numerical accuracy and convergence of the code. Many tests combine chemistry with gas dynamics, including comparisons with analytic solutions, 1D problems of the photodissociation regions and shocks, and realistic 3D simulations of the turbulent ISM. We release the code with the new public version of Athena++ , aiming to provide a robust and flexible code for the astrochemical simulation community.
ISSN:0067-0049
1538-4365
DOI:10.3847/1538-4365/aceaf9