Cosmology from the kinetic polarized Sunyaev Zel'dovich effect

TL;DR

This paper explores the kinetic polarized Sunyaev Zel'dovich (kpSZ) effect, a polarization anisotropy in the CMB caused by relativistic corrections, and forecasts its detectability with future surveys, also proposing a new estimator for the velocity field.

Contribution

It introduces a quadratic estimator for the transverse peculiar velocity squared and discusses the potential of the kpSZ effect to probe cosmic birefringence and primordial non-Gaussianity.

Findings

Future experiments can statistically detect the kpSZ effect.

A quadratic estimator for the velocity squared is proposed.

kpSZ can probe fundamental cosmological phenomena.

Abstract

The cosmic microwave background (CMB) photons that scatter off free electrons in the large-scale structure induce a linear polarization pattern proportional to the remote CMB temperature quadrupole observed in the electrons' rest frame. The associated blackbody polarization anisotropies are known as the polarized Sunyaev Zel'dovich (pSZ) effect. Relativistic corrections to the remote quadrupole field give rise to a non-blackbody polarization anisotropy proportional to the square of the transverse peculiar velocity field; this is the kinetic polarized Sunyaev Zel'dovich (kpSZ) effect. In this paper, we forecast the ability of future CMB and galaxy surveys to detect the kpSZ effect, finding that a statistically significant detection is within the reach of planned experiments. We further introduce a quadratic estimator for the square of the peculiar velocity field based on a galaxy survey and CMB polarization. Finally, we outline how the kpSZ effect is a probe of cosmic birefringence and primordial non-Gaussianity, forecasting the reach of future experiments.