Large-scale simulations of reionization

We use cosmological simulations to explore the large-scale effects of reionization. Since reionization is a process that involves a large dynamic range-from galaxies to rare bright quasars-we need to be able to cover a significant volume of the universe in our simulation without losing the important small-scale effects from galaxies. Here we have taken an approach that uses clumping factors derived from small-scale simulations to approximate the radiative transfer on subcell scales. Using this technique, we can cover a simulation size up to 1280 h(-1) Mpc with 10 h(-1) Mpc cells. This allows us to construct synthetic spectra of quasars similar to observed spectra of Sloan Digital Sky Survey (SDSS) quasars at high redshifts and compare them to the observational data. These spectra can then be analyzed for H II region sizes, the presence of the Gunn-Peterson trough, and the Ly alpha forest.