Monte Carlo radiation hydrodynamics in the super-Eddington regime

In this dissertation, we present three projects addressing the dynamical importance of radiation in turbulent media with super-Eddington flux. Examples of such media are massive star-forming environments and supermassive star atmospheres. While there are many theoretical models claiming the pivotal role of radiation in driving strong outflows and setting the star formation efficiency in the course of massive star formation, often they are based on ideal geometries and closure relations of the moment equations for radiation. To directly tackle the challenge of numerically modeling radiation-matter interactions in hydrodynamical simulations, we have adopted and tested a hybrid Monte Carlo radiation transport scheme. In the first project, with a standardized two-dimensional radiation-driven winds setup, we show that low-order methods tend to artificially reinforce the development of the low-density channels and underestimate the strength of radiation pressure. The accuracy of any numerical radiation transport scheme in producing truthful dynamics therefore depends on the validity of its underlying assumptions. In the second project, we carry out radiation hydrodynamical simulations of the formation of super star clusters in supersonically turbulent molecular clouds. The gas distribution is strongly inhomogeneous and that reduces the strength of radiation pressure in halting gas accretion compared to previous predictions. In the last project, unlike the inflow-outflow scenario of the first two, we aim to simulate the radiation hydrodynamics in quasi-hydrostatic media with extreme sensitivity of the opacity to density and temperature. We present the implementation and robustness test of the hybrid Monte Carlo estimators in preparation for direct simulations of the convective, radiation-dominated dynamics prevalent in the atmospheres of supermassive stars.