Cross-correlation studies as a probe of reionization physics

The process of reionization is now believed to have proceeded in an orchestrated manner beginning with ultraviolet photons emitted by high-redshift galaxies containing a large fraction of Pop III stars carving out ionized regions around them. The physics during this era can be studied with a combination of redshifted 21-cm spin-flip transition tracing neutral hydrogen gas, IR emission from massive primordial stars that trace the global star formation rate during reionization, and the imprint of hot electrons in first supernova remnants Compton-cooling off of cosmic microwave background radiation through the Sunyaev-Zel'dovich effect. While these individual effects and their observable signatures have been advocated as probes of reionization history, here we show how cross-correlation studies between these signals can be used to further understand physics during reionization. Cross-correlation studies are advantageous since the measurable statistics do not suffer in the same manner from foregrounds and systematic effects as is the case of auto-correlation function measurements. We discuss the prospects for detecting various cross-correlation statistics using present and next-generation experiments and the information related to reionization captured by them.