γ-Cascade V4: A semi-analytical code for modeling cosmological gamma-ray propagation

Since the universe is not transparent to gamma rays with energies above around one hundred GeV, it is necessary to account for the interaction of high-energy photons with intergalactic radiation fields in order to model gamma-ray propagation. Here, we present a public numerical software for the modeling of gamma-ray observables. This code computes the effects on gamma-ray spectra from the development of electromagnetic cascades and cosmological redshifting. The code introduced here is based on the original γ-Cascade, and builds on it by improving its performance at high redshifts, introducing new propagation modules, and adding many more extragalactic radiation field models, which enables the ability to estimate the uncertainties inherent to EBL modeling. We compare the results of this new code to existing Monte Carlo electromagnetic transport models, finding good agreement within EBL uncertainties. PROGRAM SUMMARY Program title: γ-Cascade CPC Library link to program files: https://doi.org/10.17632/3vw7ybpjnk.1 Developer's repository link: https://github.com/GammaCascade/GCascade Licensing provisions: GPLv3 Programming language: Wolfram Language. Supplementary material: Tutorial notebook, functional and auxiliary file libraries. Nature of problem: Obtaining gamma-ray fluxes from astrophysical sources active above ∼100 GeV is not trivial due to the absorption and regeneration of these particles en route to the Earth, producing electromagnetic cascades. Accurate simulation of cosmological cascade development typically requires the precision of numerical codes. Solution method: γ-Cascade efficiently calculates cascaded fluxes from point-like and diffuse populations of sources, employing semi-analytical methods over discrete energy and redshift grids.