Modelling of ionising feedback with Smoothed Particle Hydrodynamics and
  Monte Carlo Radiative Transfer on a Voronoi grid
  The ionising feedback of young massive stars is well known to influence the
dynamics of the birth environment and hence plays an important role in
regulating the star formation process in molecular clouds. For this reason,
modern hydrodynamics codes adopt a variety of techniques accounting for these
radiative effects. A key problem hampering these efforts is that the
hydrodynamics are often solved using smoothed particle hydrodynamics (SPH),
whereas radiative transfer is typically solved on a grid. Here we present a
radiation-hydrodynamics (RHD) scheme combining the SPH code Phantom and the
Monte Carlo Radiative Transfer (MCRT) code CMacIonize, using the particle
distribution to construct a Voronoi grid on which the MCRT is performed. We
demonstrate that the scheme successfully reproduces the well-studied problem of
D-type H II region expansion in a uniform density medium. Furthermore, we use
this simulation setup to study the robustness of the RHD code with varying
choice of grid structure, density mapping method, and mass and temporal
resolution. To test the scheme under more realistic conditions, we apply it to
a simulated star-forming cloud reminiscing those in the Central Molecular Zone
of our galaxy, in order to estimate the amount of ionised material that a
single source could create. We find that a stellar population of several
$10^3~\rm{M_{\odot}}$ is needed to noticeably ionise the cloud. Based on our
results, we formulate a set of recommendations to guide the numerical setup of
future and more complex simulations of star forming clouds.
