Secondary anisotropies of the CMB

TL;DR

This paper reviews the secondary anisotropies in the Cosmic Microwave Background, focusing on their physical origins, signatures, and observational status, to better understand the universe's reionisation and structure growth.

Contribution

It provides a comprehensive review of the physics, signatures, and current observational efforts related to secondary CMB anisotropies, highlighting their importance in cosmology.

Findings

Detailed description of secondary anisotropies and their physical mechanisms.

Analysis of signatures in temperature, polarisation, and statistics.

Overview of current and future observational efforts.

Abstract

The Cosmic Microwave Background fluctuations provide a powerful probe of the dark ages of the universe through the imprint of the secondary anisotropies associated with the reionisation of the universe and the growth of structure. We review the relation between the secondary anisotropies and and the primary anisotropies that are directly generated by quantum fluctuations in the very early universe. The physics of secondary fluctuations is described, with emphasis on the ionisation history and the evolution of structure. We discuss the different signatures arising from the secondary effects in terms of their induced temperature fluctuations, polarisation and statistics. The secondary anisotropies are being actively pursued at present, and we review the future and current observational status.