Photon-conserving radiative transfer around point sources in multidimensional numerical cosmology

Many questions in physical cosmology regarding the thermal and ionization history of the intergalactic medium are now being successfully studied with the help of cosmological hydrodynamical simulations. Here we present a numerical method that solves for the radiative transfer around point sources within a three-dimensional Cartesian grid. The method is energy-conserving independent of resolution; this ensures correct propagation speeds for ionization fronts. We describe the details of the algorithm and compute as a first numerical application the ionized region surrounding a mini-quasar in a cosmological density field at z = 7.