Makemake + Sedna: A Continuum Radiation Transport and Photoionization
  Framework for Astrophysical Newtonian Fluid Dynamics
  Astrophysical fluid flow studies often encompass a wide range of physical
processes to account for the complexity of the system under consideration. In
addition to gravity, a proper treatment of thermodynamic processes via
continuum radiation transport and/or photoionization is becoming the state of
the art. We present a major update of our continuum radiation transport module,
MAKEMAKE, and a newly developed module for photoionization, SEDNA, coupled to
the magnetohydrodynamics code PLUTO. These extensions are currently not
publicly available; access can be granted on a case-by-case basis. We explain
the theoretical background of the equations solved, elaborate on the numerical
layout, and present a comprehensive test suite for radiation-ionization
hydrodynamics. The grid-based radiation and ionization modules support static
one-dimensional, two-dimensional, and three-dimensional grids in Cartesian,
cylindrical, and spherical coordinates. Each module splits the radiation field
into two components, one originating directly from a point source - solved
using a ray-tracing scheme - and a diffuse component - solved with a
three-dimensional flux-limited diffusion (FLD) solver. The FLD solver for the
continuum radiation transport makes use of either the equilibrium
one-temperature approach or the linearization two-temperature approach. The FLD
solver for the photoionization module enables accounting for the temporal
evolution of the radiation field from direct recombination of free electrons
into hydrogen's ground state as an alternative to the on-the-spot
approximation. A brief overview of completed and ongoing scientific studies is
given to explicitly illustrate the multipurpose nature of the numerical
framework presented.
