Dr Oh and his team will study the effect of newly-forming galaxies on the diffuse intergalactic medium, as the ultraviolet radiation from their young stars and active nuclei reionizes the gas. They will incorporate Monte-Carlo radiative transfer into the cosmological hydrodynamics code of collaborator Yoshida, and use this code to investigate how radiation pressure and the trapping of Lyman-alpha photons can regulate star formation and gas flow in early proto-galaxies. Several low-frequency radio telescopes now under construction will measure the redshifted 21cm radiation emitted by neutral hydrogen gas less than half a billion years after the Big Bang. Dr Oh and his team will develop better numerical algorithms and statistics to analyze these observations, and to remove signals from nearby objects. This will provide better measures of how the fraction of neutral gas decreases with time, and of the location and size of the regions ionized by nascent galaxies. The remaining neutral gas produces absorption lines in the spectra of distant quasars. This team will use simulations to derive an improved model that will allow better estimates for the time that hydrogen and helium were reionized, for the equation of state of the intergalactic gas at early times, and for the clustering of intergalactic gas clouds close to the present day.
Both graduate and undergraduate students will be trained by participating in the research. Dr Oh and his team will make their analysis codes available to the astronomical community. This is an international project in collaboration with a Japanese investigator.
