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arXiv · 2405.08878

A power spectrum approach to the search for Axion-like Particles from resolved galaxy clusters using CMB as a backlight

Harsh Mehta·Suvodip Mukherjee
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Abstract

Axions or ALPs are hypothetical particles predicted by BSM theories, which make one of the dark matter candidates. These particles can convert into photons and vice-versa in the presence of magnetic field, with a probability decided by its coupling strength $\mathrm{g_{aγ}}$. One of the ways to detect these particles is using the CMB as a backlight. As the CMB photons pass through a galaxy cluster, they can get converted into ALPs in the mass range $10^{-15}$ eV to $10^{-11}$ eV through resonant conversion in the presence of cluster magnetic fields. This leads to a polarized spectral distortion ($α$-distortion) in the CMB as the photon polarization parallel to the magnetic field in the galaxy cluster is involved in the conversion. The fluctuations in the magnetic field and electron density in a galaxy cluster lead to spatially varying $α$-distortion around the cluster, with a power spectrum that is different from the lensed CMB polarization power spectrum for the standard model of cosmology. By measuring the difference in the polarization power spectrum around a galaxy cluster from the all-sky signal, one can find new $α$-distortion in the sky. For galaxy clusters resolvable in multiple EM bands, one can measure the coupling strength $\mathrm{g_{aγ}}$ from the ALP power spectrum. Using multi-frequency techniques like ILC to clean the foregrounds, we show that the new power spectrum-based approach of the resolved galaxy clusters from upcoming CMB experiments such as Simons Observatory and CMB-S4 can detect (or put constraints) on the ALP-photon coupling strength of $\mathrm{g_{aγ} < 5.2 \times 10^{-12} \, GeV^{-1}}$ and $\mathrm{g_{aγ} < 3.6 \times 10^{-12} \, GeV^{-1}}$ at 95\% C.I. respectively for ALPs of masses $10^{-13}$ eV or for smaller $\mathrm{g_{aγ}}$ for lighter ALP masses (Abridged).

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Harsh Mehta, Suvodip Mukherjee. 2024-09-16. A power spectrum approach to the search for Axion-like Particles from resolved galaxy clusters using CMB as a backlight. https://doi.org/10.1088/1475-7516%2F2024%2F09%2F037

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