The Kinetic Sunyaev-Zel'dovich Effect Due to the Electrons of Our Galaxy

TL;DR

This paper calculates the kinetic Sunyaev-Zel'dovich effect caused by electrons in our Galaxy, revealing a small, predictable anisotropy in the CMB that can be modeled precisely for future measurements.

Contribution

It provides the first detailed computation of the Galactic electron-induced kinetic SZ effect, including its angular power spectrum and potential impact on CMB observations.

Findings

The effect is approximately 2 microkelvin in magnitude.

The angular power spectrum exhibits a sawtooth pattern with suppressed even multipoles.

The signal is sub-dominant but can be accurately modeled for future CMB analyses.

Abstract

We compute the effect of local electrons on the CMB temperature anisotropies. The number density and distribution of free electrons in our Galaxy has been accurately measured from pulsar dispersion measurements. Because of their distribution, the dynamics of our Galaxy and the Galaxy peculiar velocity with respect to the Hubble flow, these free electrons leave a frequency-independent imprint on the cosmic microwave background (CMB). In particular, the coherent motion of the free electrons respect to us and to the CMB rest frame produce a kinetic Sunyaev-Zeldovich signal. We compute this effect and we note that the large-scale antisymmetry of the signal gives it an angular power spectrum with a sawtooth pattern where even multipoles are suppressed with respect to the odd ones. We find the signal to be small (~ 2 uK) and sub-dominant compared to the primary CMB and other foreground signals. However, since there are no free parameters in the modeling of this signal, it can be taken into account if more precise measurements of the primordial signal are required.