Adam Lidz (U. Penn)
An exciting frontier in observational and theoretical cosmology is the study of the first galaxies and accreting black holes. These sources emitted ultraviolet light and ionized bubbles of hydrogen gas around them, eventually filling the entire volume of the universe with ionized hydrogen in a process known as reionization. I will challenge conventional wisdom regarding one of the primary observational constraints on reionization. It is often claimed that quasar absorption spectra require reionization to complete at a redshift higher than six (z >6). I will discuss how and why this may, in fact, be incorrect. The possibility of incomplete reionization at z < 6 is testable with current and future Lyman-alpha forest measurements: I will describe the prospects here and show some preliminary results. Turning to 21 cm, I will briefly discuss the claimed detection of a 21 cm absorption signal in the sky-averaged radio spectrum by the EDGES experiment. Finally, I will describe how future observations of 21 cm fluctuations during reionization may be fruitfully combined with line-intensity mapping surveys in other emission lines.
