Cosmological probes of helium reionization

Joint analysis of cosmic microwave background (CMB) and large-scale structure at high redshifts provide new and unique windows into unexplored epochs of early structure formation. Here, we demonstrate how cosmic infrared background and high-redshift galaxies can be jointly analyzed with CMB to probe the epoch of helium reionization (2 < z < 4) on the light cone using kinetic Sunyaev Zel'dovich tomography. Characterizing this epoch has great potential significance for understanding astrophysics of galaxy formation, quasar activity and formation of the supermassive black holes. We find a detection at 8-10 sigma can be expected from combinations of data from CCAT prime, Vera Rubin Observatory, and CMB-S4 in the upcoming years.