SZ effects from annihilating dark matter in the Milky Way: smooth halo, subhalos and intermediate-mass-black-holes

TL;DR

This study evaluates the potential for detecting the Sunyaev-Zel'dovich effect caused by dark matter annihilation or decay in the Milky Way, concluding it is unlikely to produce observable distortions in the CMB spectrum.

Contribution

The paper provides a comprehensive analysis of the SZ effect from various dark matter components in the Galaxy, including smooth halo, subhalos, and black hole spikes, showing they are undetectable with current instruments.

Findings

Dark matter-induced SZ effect is below detection thresholds of Planck and ALMA.

Optical depth from dark matter annihilation is at most ~10^{-7}.

Galactic dark matter effects do not significantly distort the CMB spectrum.

Abstract

We study the Sunyaev-Zel'dovich effect potentially generated by relativistic electrons injected from dark matter annihilation or decay in the Galaxy, and check whether it could be observed by Planck or the Atacama Large Millimeter Array (ALMA), or even imprint the current CMB data as, e.g., the specific fluctuation excess claimed from an recent reanalysis of the WMAP-5 data. We focus on high-latitude regions to avoid contamination of the Galactic astrophysical electron foreground, and consider the annihilation or decay coming from the smooth dark matter halo as well as from subhalos, further extending our analysis to a generic modeling of spikes arising around intermediate-mass black holes. We show that all these dark Galactic components are unlikely to produce any observable Sunyaev-Zel'dovich effect. For a self-annihilating dark matter particle of 10 GeV with canonical properties, the largest optical depth we find is $\tau_e \lesssim 10^{-7}$ for massive isolated subhalos hosting intermediate-mass black holes. We conclude that dark matter annihilation or decay on the Galactic scale cannot lead to significant Sunyaev-Zel'dovich distortions of the CMB spectrum.