Constraints on axions from patchy screening of the cosmic microwave background

Abstract

The resonant conversion of cosmic microwave background (CMB) photons into axions within large-scale structure induces an anisotropic spectral distortion in CMB temperature maps. Applying state-of-the-art foreground cleaning techniques to $\text{Planck}$ CMB observations, we construct maps of axion-induced "patchy screening" of the CMB. We cross-correlate these maps with data from the $\text{unWISE}$ galaxy survey and find no evidence of axions. We constrain the axion-photon coupling, $g_{a\gamma \gamma }\lesssim 2\times 10^{-12}{\mathrm{GeV}}^{-1}$, at the 95% confidence level for axion masses in the range $10^{-13}\mathrm{eV}\lesssim m_a\lesssim 10^{-12}\mathrm{eV}$. These constraints are competitive with the tightest astrophysical axion limits in this mass range and are inferred from robust population-level statistics, which makes them complementary to existing searches that rely on modeling of individual systems.

5+15 pages; 3+15 figures