Cosmological Radiation Simulation Analysis: Taking Arepo-RT as an Example

Abstract

With the fast-growing progress in computational physics, astrophysical simulations are made possible and continually upgraded with novel physical models. Contemporarily, many modern simulations feature the capability of cosmological radiation. In order to collate the recent improvements in this field, the numerical solver Arepo-RT is discussed as an important example. This study reorganizes and interprets the main physical models and numerical techniques used in Arepo-RT and similar solvers, with some details simplified to suit common readers. This paper describes simply and briefly the finite volume method, the radiative transfer model, the radiation source model, the Godunov-type schemes and the time integration, all of which are frequently used in modern radiation simulations. Apart from the realizations of the solvers, the results and limitations are also outlined in this paper, including the justification of reduced speed of light approximation, the results compared with JWST, and the issue of missing photons. These results shed light on guiding further improvements for Arepo-RT.