Detecting patchy reionization in the CMB

TL;DR

This paper introduces a new statistical method to isolate the high-redshift patchy reionization signal in small-scale CMB temperature fluctuations, enabling more precise measurements of the reionization era without external data.

Contribution

A novel statistic that separates the kSZ effect from other small-scale CMB fluctuations and decomposes it into redshift bins, including high redshift, without relying on external datasets.

Findings

Effective separation of kSZ signal from other effects.

High-redshift reionization signal can be isolated.

Enables future high-significance measurements of reionization.

Abstract

Upcoming cosmic microwave background (CMB) experiments will measure temperature fluctuations on small angular scales with unprecedented precision. Small-scale CMB fluctuations are a mixture of late-time effects: gravitational lensing, Doppler shifting of CMB photons by moving electrons (the kSZ effect), and residual foregrounds. We propose a new statistic which separates the kSZ signal from the others, and also allows the kSZ signal to be decomposed in redshift bins. The decomposition extends to high redshift, and does not require external datasets such as galaxy surveys. In particular, the high-redshift signal from patchy reionization can be cleanly isolated, enabling future CMB experiments to make high-significance and qualitatively new measurements of the reionization era.