Smoothed particle radiation hydrodynamics: two-moment method with local Eddington tensor closure

We present a new radiative transfer method (SPH-M1RT) that is coupled dynamically with smoothed particle hydrodynamics (SPH). implement it in the (task-based parallel) SWIFT galaxy simulation code but can be straightforwardly implemented other SPH codes. Our moment-based simultaneously solves radiation energy and flux equations SPH, making adaptive space time. modify M1 closure relation to stabilize fronts optically thin limit. also introduce anisotropic artificial viscosity high-order diffusion schemes, which allow handle transport accurately both thick regimes. Non-equilibrium thermo-chemistry solved using semi-implicit sub-cycling technique. The computational cost of our independent number sources lowered further by reduced speed light approximation. demonstrate robustness applying set standard tests from cosmological comparison project Iliev et al. SPH-M1RT scheme well-suited for modelling situations numerous emit ionising radiation, such as simulations formation or interstellar medium.