A new algorithm for modelling photoionizing radiation in smoothed particle hydrodynamics

We present a new fast algorithm which allows the simulation of ionizing radiation emitted from a point source to be included in high-resolution three-dimensional smoothed particle hydrodynamics simulations of star cluster formation. We employ a Strömgren volume technique in which we use the densities of particles near the line-of-sight between the source and a given target particle to locate the ionization front in the direction of the target. Along with one-dimensional tests, we present fully three-dimensional comparisons of our code with the three-dimensional Monte Carlo radiative transfer code, MOCASSIN, and show that we achieve good agreement, even in the case of highly complex density fields.