Radiation Hydrodynamics of First Stars with SimpleX Radiative Transfer

Abstract

We present a new radiative transfer method, the SimpleX method, that solves the radiative transfer equation on an unstructured, physical grid. SimpleX is a computationally very fast method that does not scale with the number of sources in the simulation domain. Tests show that the results of ionization front calculations done with SimpleX are comparable to the results of other methods, but at lower computational costs. It is important to incorporate diffuse photons in calculations of ionization fronts. The outer parts of H II regions are dominated by diffuse photons, so we need to incorporate these to model the shape and dynamics of ionization fronts properly. Because SimpleX does not scale with the number of sources in the simulation domain, we can model diffuse photons without extra computational costs. Our goal is to couple SimpleX to the hydrodynamics code FLASH to calculate radiative transfer in step with the hydrodynamics calculations. We plan to investigate primordial star formation, specifically the interaction of radiation with the accreting protostar, to determine the final mass of the first stars, and the influence of the star's UV radiation on the surrounding minihalo.