WMAP Microwave Emission Interpreted as Dark Matter Annihilation in the Inner Galaxy

TL;DR

This paper suggests that excess microwave emission in the inner Galaxy can be explained by synchrotron radiation from relativistic electrons produced by dark matter annihilation, aligning with gamma-ray observations and ruling out conventional sources.

Contribution

It proposes a dark matter annihilation model with specific parameters as the source of microwave excess, providing a novel interpretation of the emission.

Findings

Microwave excess consistent with dark matter annihilation-produced electrons

Conventional emission sources are ruled out as explanations

Dark matter model fits current microwave and gamma-ray data

Abstract

Excess microwave emission observed in the inner Galaxy (inner ~1 kpc) is consistent with synchrotron emission from highly relativistic electron-positron pairs produced by dark matter particle annihilation. More conventional sources for this emission, such as free-free (thermal bremsstrahlung), thermal dust, spinning dust, and the softer Galactic synchrotron traced by low-frequency surveys, have been ruled out. The total power observed in the range 23 < nu < 61 GHz is between 10^{36} and 5x10^{36} erg/s, depending on the method of extrapolation to the Galactic center, where bright foreground emission obscures the signal. The inferred electron energy distribution is diffusion hardened, and is in qualitative agreement with the energy distribution required to explain the gamma ray excess in the inner Galaxy at 1-30 GeV as inverse-Compton scattered starlight. We investigate the possibility that this population of electrons is produced by dark matter annihilation of 100 GeV particles, with cross section <sigma v>=2x10^{-26} cm^3/s, and an 1/r dark matter mass profile truncated in the inner Galaxy, and find this scenario to be consistent with current data.