Effects of Magnetic Fields Models on Photon to Axion-like Particles Conversion

Sammanfattning

Axion-like particles (ALPs) are strongly-motivated extensions of the Standard Model and convincing dark matter candidates. Their detection could have implications for both particle physics and cosmology. One promising strategy for ALP searches is to look for energy-dependent modulations in the high-energy spectra of X-ray and gamma-ray sources located behind galaxy clusters. These modulations may be caused by photon– ALP conversion in the magnetic fields of the intracluster medium (ICM). Previous studies generally rely on simplified magnetic field models, which may not ac- curately describe the structure of galaxy cluster environments. In this work, we study axion–photon mixing in a Perseus-like cluster using magnetic field and electron density profiles extracted from the IllustrisTNG cosmological magnetohydrodynamical (MHD) simulation (Nelson et al. (2021)). We perform photon–ALP mixing calculations using the Fourier formalism described by Marsh et al. (2022), as well as the ALPro Matthews et al. (2022) and gammaALPs Meyer et al. (2021) packages. This enables a direct comparison between analytical propagation, cell-by-cell domain evolution and statistical realizations of turbulent magnetic fields. The statistics of the conversion probability are analyzed using cumulative distributions. While the GRF magnetic field produces distributions consistent with the expected ex- ponential behavior, the MHD magnetic field extracted from IllustrisTNG systematically exhibits heavier tails, corresponding to an enhanced occurrence of larger conversion events. This tendency is quantified via increased skewness and kurtosis, which is also consistent with previous predictions by Carenza et al. (2023). These results underline the crucial role of realistic magnetic field implementations in predicting photon–ALP mixing signatures in galaxy clusters. Ultimately, this work provides a relevant benchmark for evaluating ALP signals in astrophysical environments using precise cosmological MHD simulations.