Abstract
In the Epoch of Reionization (EoR), the neutral IGM was ionized by the rapidly evolving ultraviolet background produced by early stars and galaxies. Studying this era is difficult due in part to the high opacity of the IGM, yet creating a clearer picture of it could reveal much about the traits of early galaxies and gas enrichment. Using cosmological simulations of the EoR that incorporate in-situ multi-frequency radiative transfer in tandem with mock quasar absorption spectra, we analyze metrics of metal absorption and other gas parameters to illuminate their connection to the process of reionization. By incorporating stellar population synthesis models including either single or binary stars, we additionally examine how differing stellar emissivities impact the timing of reionization and the preferred ionization states of metals in the enriched CGM and IGM. We find that common absorbing transitions are sensitive to the amplitude and spectral shape of the ionizing background, suggesting that careful observations of these systems will place constraints on the nature of the primary contributors to reionization. Further, we determine the redshift evolution of metal ionization can help constrain the timing of reionization. Finally, we show that although the hard spectra of binary stars significantly impact elemental ionization states and lead to an accelerated H I reionization history, they also lead to a decreased star formation rate density through photoheating and a cascade of related physical effects in galaxies and the CGM and IGM.