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.

由于宇宙对能量约100GeV以上的伽马射线不透明，为了模拟伽马射线的传播过程，必须考虑高能光子与星系际辐射场的相互作用。在此，我们公开了一款用于伽马射线可观测特征建模的数值软件。该代码可计算电磁级联演化与宇宙学红移对伽马射线能谱的影响。本文介绍的这款代码基于原始γ-Cascade开发，并针对其开展了多项改进：提升了高红移场景下的运行性能，新增了传播模块，同时补充了更多河外辐射场模型，由此得以估算河外背景光（Extragalactic Background Light，EBL）建模过程中固有的不确定性。我们将该新代码的计算结果与现有的蒙特卡洛电磁输运模型进行了对比，发现在EBL的不确定性范围内二者吻合度良好。