The GALPROP code for cosmic-ray transport and diffuse emission production

GALPROP is a numerical code for calculating the propagation of relativistic charged particles and the diffuse emissions produced during their propagation. The GALPROP code incorporates as much realistic astrophysical input as possible together with latest theoretical developments. The code calculates the propagation of cosmic-ray nuclei, antiprotons, electrons and positrons, and computes diffuse γ-rays and synchrotron emission in the same framework. Each run of the code is governed by a configuration file allowing the user to specify and control many details of the calculation. Thus, each run of the code corresponds to a potentially different ``model''. The code itself continues to be developed and is available to the scientific community via this website.

MOTIVATION AND ACKNOWLEDGEMENTS

Discoveries and studies in cosmic-ray physics and, generally, in high-energy astrophysics are closely related to research in many areas of particle physics and cosmology: the search for dark matter, antimatter, new particles, and exotic physics; nucleosynthesis studies; the origin of the Galactic and extragalactic γ-ray diffuse emission; the formation of the large scale structure of the Universe; heliospheric modulation, and so forth. In turn, the astrophysics of cosmic rays, γ-rays, and other diffuse emissions, depends very much on the quality of the data and their proper interpretation. The quality of data from cosmic-ray experiments such as Ulysses, the Advanced Composition Explorer (ACE), the Voyagers, TIGER, the Fermi LAT (formerly GLAST), PAMELA, CREAM, BESS-Polar, AMS, and possibly ACCESS, far exceeds the accuracy of analytical propagation models, such as the ``leaky-box'' model that has remained one of the main research tools for the last 50 years. These missions are specifically designed to search for dark matter signals in cosmic rays and diffuse γ-rays, searches for antimatter, and to study the diffuse Galactic and extragalactic diffuse emission, over a wide energy range. Meanwhile, developments in astrophysics, such as detailed 3-dimensional maps of the Galactic gas distribution, detailed studies of composition of interstellar dust, grains, the Local Bubble, interstellar radiation and magnetic fields, and new classes of cosmic-ray sources, all have implications for the interpretation of data obtained from ballon-borne and space-based experiments. The same can be said for more accurate measurements of nuclear isotopic production cross sections and new particle data that become increasingly available. Having the latest results and theoretical knowledge distilled and easily accessible in a unified framework is advantageous for the scientific community, as well as for planning and setting the goals for new missions.

The first version of the GALPROP code was written in FORTRAN-90/77 in the mid-1990s by Andrew W. Strong and Igor V. Moskalenko and then rewritten in C++ (with the well-tested FORTRAN-77 routines remaining). Seth W. Digel and Troy A. Porter joined the project in the early 2000s with Gulli Johannesson, Elena Orlando, and Andrey Vladimirov as more recent additions to the team. Other people have contributed by providing libraries, expertise, and data sets over the years: Stepan G. Mashnik, Olaf Reimer, V. S. Barashenkov, A. Polanski, R. Silberberg, C. H. Tsao, and W. R. Webber. We remember our late colleague Patrick Nolan who has shared a great deal of his knowledge, time and humor with the GALPROP team.

We are grateful to Jeff Wade who provides valuable assistance with the system administration for the GALPROP web servers and computing cluster. We also thank Irina V. Malkova for her help in designing and supporting the first version of this website.

The GALPROP development team acknowledges the use of HEALPix https://healpix.jpl.nasa.gov/ described in: K.M. Gorski et al., 2005, Ap.J., 622, p.759

This website is supported by NASA through an APRA "Laboratory Astrophysics" grant, by Stanford University, and by the GALPROP project. This is a free service to the scientific community. GALPROP source code and data sets can be freely copied, however, it is requested that in any subsequent use of the code and associated data sets be given appropriate acknowledgment.