A possible signature of annihilating dark matter

TL;DR

This paper proposes a new radio signature of dark matter annihilation in NGC 1569, suggesting that electrons and positrons from 25 GeV dark matter particles could explain observed spectral features, challenging previous cosmic ray interpretations.

Contribution

It introduces a novel interpretation of radio spectral features as evidence of dark matter annihilation, specifically via the 4-e channel with a 25 GeV mass.

Findings

Radio spectral index change aligns with dark matter annihilation predictions.

Cosmic ray contribution alone cannot explain the observed radio flux.

Best-fit dark matter mass is 25 GeV.

Abstract

In this article, we report a new signature of dark matter annihilation based on the radio continuum data of NGC 1569 galaxy detected in the past few decades. After eliminating the thermal contribution of the radio signal, an abrupt change in the spectral index is shown in the radio spectrum. Previously, this signature was interpreted as an evidence of convective outflow of cosmic ray. However, we show that the cosmic ray contribution is not enough to account for the observed radio flux. We then discover that if dark matter annihilates via the 4-e channel with the thermal relic cross section, the electrons and positrons produced would emit a strong radio flux which can provide an excellent agreement with the observed signature. The best-fit dark matter mass is 25 GeV.