Cosmological Radiation Hydrodynamics with ENZO

TL;DR

This paper extends the ENZO cosmological simulation code to include self-consistent ionizing radiation transport using an implicit flux-limited diffusion approach, enabling more accurate modeling of hydrogen reionization.

Contribution

It introduces a novel implicit coupled solver for radiation, ionization, and heating in cosmological simulations, improving resolution independence and scalability.

Findings

Successfully verified with Stromgren sphere test

Applied to cosmological hydrogen reionization

Demonstrated scalable multigrid solution

Abstract

We describe an extension of the cosmological hydrodynamics code ENZO to include the self-consistent transport of ionizing radiation modeled in the flux-limited diffusion approximation. A novel feature of our algorithm is a coupled implicit solution of radiation transport, ionization kinetics, and gas photoheating, making the timestepping for this portion of the calculation resolution independent. The implicit system is coupled to the explicit cosmological hydrodynamics through operator splitting and solved with scalable multigrid methods. We summarize the numerical method, present a verification test on cosmological Stromgren spheres, and then apply it to the problem of cosmological hydrogen reionization.