Astrochem is a code to compute the abundances of chemical species in the interstellar medium, as function of time. It is designed to study the chemistry in a variety of astronomical objects, including diffuse clouds, dense clouds, photodissociation regions, prestellar cores, protostars, and protostellar disks. Astrochem reads a network of chemical reactions from a text file, builds up a system of kinetic rates equations, and solve it using a state-of-the-art stiff ordinary differential equation (ODE) solver. The Jacobian matrix of the system is computed implicitly, so the resolution of the system is extremely fast: large networks containing several thousands of reactions are usually solved in a few seconds. A variety of gas phase process are considered, as well as simple gas-grain interactions, such as the freeze-out and the desorption via several mechanisms (thermal desorption, cosmic-ray desorption and photo-desorption). The computed abundances are written in a HDF5 file, and can be plotted in different ways with the tools provided with Astrochem. Chemical reactions and their rates are written in a format which is meant to be easy to read and to edit. A tool to convert the chemical networks from the OSU and KIDA databases into this format is also provided. Astrochem is written in C, and its source code is distributed under the terms of the GNU General Public License (GPL).
Astrochem installation follows a standard procedure and is fairly straightforward. Generic installation instructions can be found in the INSTALL.md file. Additional platform-specific instructions can be found on Astrochem's wiki.
Astrochem comes with a comprehensive documentation. Each command also has a man page.
A list of known bugs can be found here. If you find a bug which is not listed there, please open a new issue.
Contributions to Astrochem are welcome. Please see the CONTRIBUTING.md file for instructions.
If you use the code for your research, please cite Maret & Bergin (2015) in your papers.
For more information on Astrochem and its development, please see the project page on GitHub.
