Reionization of helium is expected to occur at redshifts z∼3 and have important consequences for quasar populations, galaxy formation, and the morphology of the intergalactic medium, but there is little known empirically about the process. Here we show that kinetic Sunyaev-Zel'dovich tomography, based on the combination of cosmic microwave background (CMB) measurements and galaxy surveys, can be used to infer the primordial helium abundance as well as the time and duration of helium reionization. We find a high-significance detection at ∼10σ can be expected from Vera Rubin Observatory and CMB-S4 in the near future. A more robust characterization of helium reionization will require next-generation experiments like MegaMapper (a proposed successor to the Dark Energy Spectroscopic Instrument) and CMB-HD.
ASJC Scopus subject areas
- Nuclear and High Energy Physics