Probing helium reionization with kinetic Sunyaev Zel'dovich tomography

TL;DR

This paper proposes using kinetic Sunyaev-Zeldovich tomography with upcoming CMB and galaxy surveys to empirically study helium reionization, including its timing, duration, and primordial abundance.

Contribution

It introduces a novel method combining CMB and galaxy data to probe helium reionization and estimates high-significance detection prospects with future experiments.

Findings

Expected ~10σ detection with Vera Rubin and CMB-S4

Next-generation experiments can improve characterization of helium reionization

Method enables empirical inference of helium abundance and reionization timeline

Abstract

Reionization of helium is expected to occur at redshifts $z\sim3$ 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-Zeldovich (kSZ) tomography, based on the combination of 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 ${\sim10\sigma}$ 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 DESI) and CMB-HD.