Looking in the axion mirror: An all-sky analysis of stimulated decay

TL;DR

This paper analyzes the potential of using all-sky radio observations to detect axion dark matter through stimulated decay, leveraging existing radio sources and forecasting the capabilities of upcoming radio telescopes.

Contribution

It introduces an all-sky analysis method for axion-induced echo images using various radio sources and demonstrates that current and future radio telescopes can effectively search for axions without additional hardware.

Findings

Radio telescopes can detect axion decay signals with existing infrastructure.

The aggregate signal is robust against uncertainties in individual source properties.

Forecasts show competitive sensitivity of upcoming telescopes like CHIME and HERA.

Abstract

Axion dark matter (DM) produces echo images of bright radio sources via stimulated decay. These images appear as a faint radio line centered at half the axion mass, with the line width set by the DM velocity dispersion. Due to the kinematics of the decay, the echo can be emitted in the direction nearly opposite to the incoming source of stimulating radiation, meaning that axions effectively behave as imperfect monochromatic mirrors. We present an all-sky analysis of axion DM-induced echo images using extragalactic radio point sources, Galactic supernova remnants (SNRs), and Galactic synchrotron radiation (GSR) as sources of stimulating radiation. The aggregate signal strength is not significantly affected by unknown properties of individual sources of stimulating radiation, which we sample from an empirical distribution to generate an ensemble of realizations for the all-sky signal template. We perform forecasts for CHIME, HERA, CHORD, HIRAX, and BURSTT, finding that they can run as competitive axion experiments simultaneously with other objectives, requiring no new hardware.