A general hybrid radiation transport scheme for star formation
  simulations on an adaptive grid
  Radiation feedback plays a crucial role in the process of star formation. In
order to simulate the thermodynamic evolution of disks, filaments, and the
molecular gas surrounding clusters of young stars, we require an efficient and
accurate method for solving the radiation transfer problem. We describe the
implementation of a hybrid radiation transport scheme in the adaptive
grid-based FLASH general magnetohydrodynamics code. The hybrid scheme splits
the radiative transport problem into a raytracing step and a diffusion step.
The raytracer captures the first absorption event, as stars irradiate their
environments, while the evolution of the diffuse component of the radiation
field is handled by a flux-limited diffusion (FLD) solver. We demonstrate the
accuracy of our method through a variety of benchmark tests including the
irradiation of a static disk, subcritical and supercritical radiative shocks,
and thermal energy equilibration. We also demonstrate the capability of our
method for casting shadows and calculating gas and dust temperatures in the
presence of multiple stellar sources. Our method enables radiation-hydrodynamic
studies of young stellar objects, protostellar disks, and clustered star
formation in magnetized, filamentary environments.
