A radiative transfer scheme for cosmological reionization based on a local Eddington tensor

A radiative transfer scheme is presented, based on a moment description of the equation of radiative transfer and the so-called 'M1 closure model' for the Eddington tensor. This model features a strictly hyperbolic transport step for radiation: it has been implemented using standard Godunov-like techniques in a new code called aton. Coupled to simple models of ionization chemistry and photoheating, aton is able to reproduce the results of other schemes on a various set of standard tests such as the expansion of a H ii region, the shielding of the radiation by dense clumps and cosmological ionization by multiple sources. Being simple yet robust, such a scheme is intended to be naturally and easily included in grid-based cosmological fluid solvers.