Radiative transfer of ionizing radiation through gas and dust: stellar source case

We present a new dust extension to the Monte Carlo radiative transfer code CRASH, which enables it to simulate the propagation of ionizing radiation through mixtures of gas and dust. The new code is applied to study the impact of dust absorption on idealized galactic H II regions and on small scale reionization. In general agreement with semianalytic predictions we find that H II regions are reduced in size by the presence of dust, while their inner temperature and ionization structure remain largely unaffected. In the small scale reionization simulation, dust hardens ionization fronts and delays the overlap of ionized bubbles. This effect is found to depend only weakly on the assumed abundance of dust in underdense regions. Grain charging is presented as a preview of future extensions focussing on the photo-electrons released by dust.