Axion dark matter-induced echo of supernova remnants

TL;DR

This paper proposes that axion dark matter can produce detectable radio echoes from supernova remnants through stimulated decay, offering a new method to search for axions in the 1-10 μeV mass range.

Contribution

It introduces a novel observational signature of axion dark matter as radio echoes from supernova remnants, providing a new way to constrain axion properties.

Findings

Axion decay echoes could be detectable from supernova remnants.

Non-detection can set new limits on axion dark matter in the 1-10 μeV range.

The method fills gaps in current axion search coverage.

Abstract

Axions are a theoretically promising dark matter (DM) candidate. In the presence of radiation from bright astrophysical sources at radio frequencies, nonrelativistic DM axions can undergo stimulated decay to two nearly back-to-back photons, meaning that bright sources of radio waves will have a counterimage ("gegenschein") in nearly the exact opposite spatial direction. The counterimage will be spectrally distinct from backgrounds, taking the form of a narrow radio line centered at $\nu = m_a/4\pi$ with a width determined by Doppler broadening in the DM halo, $\Delta \nu/\nu \sim 10^{-3}$. In this work, we show that the axion decay-induced echoes of supernova remnants may be bright enough to be detectable. Their non-detection may be able to set the strongest limits to date on axion DM in the $\sim 1-10 \, \mu$eV mass range where there are gaps in coverage from existing experiments.