Axion dark matter-induced echo of supernova remnants

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 ν = ma/4π with a width determined by Doppler broadening in the DM halo, ∆ν/ν ∼ 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 ∼ 1 − 10 µeV mass range where there are gaps in coverage from existing experiments.

Astrophysical and Cosmological Probes of Dark Matter

“…A common strategy is to exploit a putative axion-photon coupling. This coupling could be detected through the decay of axions to photons (which can be stimulated [225][226][227][228][229][230][231][232] or resonantly enhanced [233][234][235][236][237][238][239][240][241]), axion-photon mixing in an external magnetic field [242] (which can notably also imprint an asymmetry on the polarization spectrum, see [e.g. 243]), birefringence [244][245][246][247][248][249][250][251], or the production of axions from non-orthogonal electric and magnetic fields [252].…”