The nature of dark matter is an unsolved cosmological problem and axions are one of the weakly interacting cold dark matter candidates. Axions or ALPs (Axion-like particles) are pseudo-scalar bosons predicted by beyond-standard model theories. The weak coupling of ALPs with photons leads to the conversion of CMB photons to ALPs in the presence of a transverse magnetic field. If they have the same mass as the effective mass of a photon in a plasma, the resonant conversion would cause a polarized spectral distortion leading to temperature fluctuations with the distortion spectrum. The probability of resonant conversion depends on the properties of the cluster such as the magnetic field, electron density, and its redshift. We show that this kind of conversion can happen in numerous unresolved galaxy clusters up to high redshifts, which will lead to a diffused polarised anisotropy signal in the microwave sky. The spectrum of the signal and its shape in the angular scale will be different from the lensed CMB polarization signal. This new polarised distortion spectrum will be correlated with the distribution of clusters in the universe and hence, with the large-scale structure. The spectrum can then be probed using its spectral and spatial variation with respect to the CMB and various foregrounds. An SNR of ~ 4.36 and ~ 93.87 are possible in the CMB-S4 145 GHz band and CMB-HD 150 GHz band respectively for a photon-ALPs coupling strength ofg_aγ = 10^-12GeV^-1using galaxy clusters beyond redshiftz= 1. The same signal would lead to additional RMS fluctuations of ~7.5 × 10^-2 μK at 145 GHz. In the absence of any signal, future CMB experiments such as Simons Observatory (SO), CMB-S4, and CMB-HD can put constraints on the coupling strength better than current bounds from particle physics experiment CERN Axion Solar Telescope (CAST).

中文翻译：

---

微波天空中轴子状粒子的扩散背景


暗物质的本质是一个未解决的宇宙学问题，轴子是弱相互作用的冷暗物质候选者之一。轴子或 ALP（类轴子粒子）是超标准模型理论预测的伪标量玻色子。 ALP 与光子的弱耦合导致 CMB 光子在横向磁场存在下转化为 ALP。如果它们的质量与等离子体中光子的有效质量相同，则共振转换将导致偏振光谱畸变，从而导致畸变光谱的温度波动。共振转换的概率取决于团簇的特性，例如磁场、电子密度及其红移。我们表明，这种转换可能发生在许多未解决的星系团中，直到高红移，这将导致微波天空中扩散的偏振各向异性信号。信号的频谱及其在角度尺度中的形状将不同于透镜 CMB 偏振信号。这种新的偏振畸变光谱将与宇宙中星团的分布相关，从而与大尺度结构相关。然后可以利用相对于 CMB 和各种前景的光谱和空间变化来探测光谱。当光子-ALP 耦合强度为_γ = 10 ^-12 GeV ^-1使用超出红移的星系团z = 1. 相同的信号会导致额外的 RMS 波动 ~7.5 × 10 ^-2 μ 145 GHz 时的 K。 在没有任何信号的情况下，西蒙斯天文台 (SO)、CMB-S4 和 CMB-HD 等未来的 CMB 实验可以对耦合强度进行比粒子物理实验 CERN 轴子太阳望远镜 (CAST) 的当前限制更好的约束。