Impacts of ultraviolet radiation feedback on the cosmic reionization history

We aim to clarify the impact of ultraviolet (UV) radiation feedback on cosmic reionization history. For the purpose, we perform radiation hydrodynamic simulations in which the formation of galaxies regulated by internal UV feedback and the global ionization of IGM by ionizing photons emitted from these galaxies are consistently solved. As a result, we find that the internal UV feedback severely suppresses the star formation not only in low mass galaxies but also in massive galaxies. One of the reasons for the suppression of the star formation in massive galaxies is smoothing of internal density structures by the internal UV and SN feedback. The smoothing of internal density structures also results in enhancements of the ionizing photon escape fractions. Our simulations well reproduce observed star formation rate densities and neutral hydrogen fractions at z ≤ 7 - 8, but cannot reproduce the optical depth for the Thomson scattering measured by WAMP. These results imply that missing sources, such as Popuplation III stars, are responsible for the reonization in the early Universe.