The effect of reionization on the CMB-density correlation

TL;DR

This paper investigates how reionization-induced rescattering of CMB photons influences temperature-matter correlations, potentially impacting interpretations of large-scale anisotropies and serving as a probe of reionization history.

Contribution

It demonstrates that rescattering during reionization significantly affects CMB-density correlations, especially at large scales, providing a new method to study reionization.

Findings

Reionization rescattering impacts large-scale CMB-density correlations.

These effects can be substantial at high redshift.

Potential to use correlations as a probe of reionization history.

Abstract

In this paper we show how the rescattering of CMB photons after cosmic reionization can give a significant linear contribution to the temperature-matter cross-correlation measurements. These anisotropies, which arise via a late time Doppler effect, are on scales much larger than the typical scale of non-linear effects at reionization; they can contribute to degree scale cross-correlations and could affect the interpretation of similar correlations resulting from the integrated Sachs-Wolfe effect. While expected to be small at low redshifts, these correlations can be large given a probe of the density at high redshift, and so could be a useful probe of the cosmic reionization history.