Constraints on Axion-Like Particles from X-ray Observations of NGC1275

Abstract

Axion-like particles (ALPs) can induce localised oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Ultra-deep Chandra observations of the Perseus cluster contain over $5\times 10^5$ counts from the AGN of the central cluster galaxy NGC1275, and represent a dataset of extraordinary quality for ALP searches. We use this dataset to search for X-ray spectral irregularities from the AGN. The absence of irregularities at the O(30%) level allows us to place leading constraints on the ALP-photon mixing parameter $g_{a\gamma \gamma }\lesssim 1.4-4.0\times 10^{-12}{\mathrm{GeV}}^{-1}$ for $m_a\lesssim 10^{-12}$ eV, depending on assumptions on the magnetic field realisation along the line of sight.

Comments: v1. 37 pages, 17 figures; v2. references added, additional discussion of gain and bounds; v3. final version accepted by ApJ