Title: The thermal and ionization history of the post-recombination universe
Description: The reionization of the hydrogen and helium are two of the least understood epochs in our cosmic history. We model using both numerical and analytical methods the reionization of these primordial elements and discuss different observational techniques to study these epochs. We show that the morphology of hydrogen reionization is principally shaped by the clustering of the first galaxies. This is fortunate because this is the property of high-redshift galaxies that is best understood. We discuss the sensitivity of 21cm observations to the hydrogen reionization epoch, and we outline how to use the clustering of Lyman-α emitting galaxies to definitively detect it. In the final chapter, we show that the temperature structure imprinted on the intergalactic gas by HeII reionization is complex and considerably different than previous studies have found. We discuss the implications that this result has on observations of the Lyα forest.