Kinetic Sunyaev Zeldovich effect in an anisotropic CMB model: measuring low multipoles of the CMB at higher redshifts using intensity and polarization spectral distortions

TL;DR

This paper develops a new formalism to compute kinetic Sunyaev-Zeldovich (kSZ) signals caused by anisotropic primordial CMB, enabling the measurement of low multipoles at high redshifts through intensity and polarization spectral distortions.

Contribution

It introduces a novel mathematical framework for calculating intensity and polarization distortions due to anisotropic CMB, including effects of cluster motion and frequency dependence.

Findings

Polarization signals primarily probe the CMB quadrupole and higher moments.

Corrections to polarization due to cluster motion are 2-10% at 200-600 GHz.

Correlations between intensity and polarization can enhance measurement sensitivity.

Abstract

We present a novel mathematical formalism that allows to easily compute the expected kinetic Sunyaev Zeldovich (kSZ) signal in intensity and polarization due to an anisotropic primordial Cosmic Microwave Background (CMB). We derive the expected intensity and polarization distortions in the direction of non-moving galaxy clusters and then we generalize our calculations for non-zero peculiar velocity. We show that, in the direction of moving clusters, low CMB multipoles impose intensity and polarization spectral distortions with different frequency dependences. The polarization signal primarily probes the quadrupole moment of the CMB, with a significant contribution from the primordial dipole and octupole moments. For a typical cluster velocity of 1000 km/s, corrections to the quadrupole-induced polarization of a non-moving cluster are of the order of 2-10% between 200-600 GHz, and depend on cluster's position on the sky, velocity magnitude and direction of motion. We also find that the angular dependence of the signal varies with frequency of observation. The distinct frequency and angular dependences of the polarization induced by the primordial dipole and octupole can be exploited to measure them despite other physical effects and foregrounds. Contrary to polarization, intensity distortions are affected by all the CMB multipoles, so they cannot be readily used to probe the low multipoles at higher redshifts. However, correlations between intensity and polarization signals, can be used to enhance the signal to noise ratio for the measurements of the primordial dipole, quadrupole and octupole. The more general calculation of the aberration kernel presented in this work has applications reaching beyond the SZ cluster science addressed here. For example, it can be exploited to the deboost/deaberrate CMB multipoles as observed in our local frame.