IMPLICATIONS OF PHOTON–AXION OSCILLATIONS ON X-RAY OBSERVATIONS OF THE COMA CLUSTER

Axion-like particles (ALPs) emerge as predictions from various extensions of the Standard Model, standing out as plausible candidates for dark matter. Axions are thought to be produced when light passes through regions of magnetic fields. This positions astrophysical environments as prime sites for their production and subsequent detection. However, establishing precise constraints on axion parameters remains challenging, primarily due to the limited understanding of astrophysical magnetic fields. The Coma cluster is notable for being the sole cluster where the profile of magnetic field strength has been relatively accurately determined using Faraday Rotation Measures. We examined the X-ray spectrum of the Coma galaxy cluster using data from the XMM-Newton observatory. We combined data from eight XMM-Newton observations conducted between 2000 and 2005, spanning a 40′ × 40′ area centered on the Coma cluster, totaling 343.8 ks. The X-ray spectrum of the ICM was characterized by modeling it with emissions from a single-temperature hot plasma. Furthermore, we explored the potential impact of photon-to-ALP conversion on the spectrum of the Coma cluster. Our investigation encompassed a range of parameters – the coupling constant and the axion mass, focusing on regions that have not yet been excluded. For the selected axion parameters, the primary impact on the spectrum could occur at high energies exceeding 5 keV. Analysis of the limited statistics gathered in this study indicates that the excluded parameter space for ALPs, based on X-ray observations of the Coma cluster, lies above the following values: gaγ < 5 · 10−13 GeV−1, ma < 1 · 10−12 eV with 95% probability.