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 UV photons emitted by high redshift galaxies containing a large fraction of Population III stars carving out ionised 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 supernovae remnants Compton-cooling off of cosmic microwave background (CMB) 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.