Axion Condensate Dark Matter Constraints from Resonant Enhancement of Background Radiation

Abstract

We investigate the possible parametric growth of photon amplitudes in a background of axion-like particle (ALP) dark matter. The observed extragalactic background radiation limits the allowed enhancement effect. We derive the resulting constraints on the axion-photon coupling constant $g_{a\gamma }$ from Galactic ALP condensates as well as over-densities. If ALP condensates of size $R$ exist in our Galaxy, a scan for extremely narrow unresolved spectral lines with frequency $\nu$ can constrain the axion-photon coupling at ALP mass $m_a=4\pi \nu$ to $g_{a\gamma }\lesssim 2\times 10^{-14}(10\mathrm{kpc}/R){\mathrm{GeV}}^{-1}$. Radio to optical background data yield constraints at this level within observed wavebands or ALP mass windows over a broad range $0.08\mu \text{eV}\lesssim m_a\lesssim 8\text{ eV}$. These condensate constraints on $g_{a\gamma }$ probe down to the QCD axion band for $m_a\gtrsim$ 10 $\mu$eV.

6+7 pages, 2 figures, 3 tables, Comments welcome!

Cited by in corpus (2)

• Searching for Light in the Darkness: Bounds on ALP Dark Matter with the optical MUSE-Faint survey
• Challenging the Stability of Light Millicharged Dark Matter