Camouflaged galactic CMB foregrounds: total and polarized contributions of the kinetic Sunyaev Zeldovich effect

TL;DR

This paper investigates the galactic kinetic Sunyaev-Zeldovich effect as a potential CMB foreground, finding it negligible for detection and contamination, and provides maps for future data analysis.

Contribution

It demonstrates that the galactic kinetic SZ effect is undetectable and does not significantly contaminate the polarized CMB, offering maps for future high-precision observations.

Findings

Kinetic SZ effect is undetectable with current techniques.

Galactic kinetic SZ does not significantly contaminate polarized CMB.

Second scattering of CMB quadrupole photons dominates potential polarization contamination.

Abstract

We consider the role of the galactic kinetic Sunyaev Zeldovich (SZ) effect as a CMB foreground. While the galactic thermal Sunyaev Zeldovich effect has previously been studied and discarded as a potential CMB foreground, we find that the kinetic SZ effect is dominant in the galactic case. We analyse the detectability of the kinetic SZ effect by means of an optimally matched filter technique applied to a simulation of an ideal observation. We obtain no detection, getting a S/N ratio of 0.1, thereby demonstrating that the kinetic SZ effect can also safely be ignored as a CMB foreground. However we provide maps of the expected signal for inclusion in future high precision data processing. Furthermore, we rule out the significant contamination of the polarised CMB signal by second scattering of galactic kinetic Sunyaev-Zeldovich photons, since we show that the scattering of the CMB quadrupole photons by galactic electrons is a stronger effect than the Sunyaev Zeldovich second scattering, and has already been shown to produce no significant polarised contamination. We confirm the latter assessment also by means of an optimally matched filter.