论文标题
测试两极分化CMB前景的光谱指数变化
Testing for spectral index variations in polarised CMB foregrounds
论文作者
论文摘要
我们提出了一种用于极化微波天空图的贝叶斯参数分量分离方法。我们共同求解主要的宇宙微波背景（CMB）信号和主要银河偏振前景成分。对于后者，我们考虑电子合成的辐射和热灰尘发射，分别以频率为模型，分别以功率定律和改良的黑体模型。我们说明输入图的噪声协方差矩阵中的像素间相关性，并在光谱指数β的先前矩阵中引入了空间相关长度。我们将我们的方法应用于低分辨率极化Planck 2018低频和高频仪器（LFI/HFI）数据，包括HFI数据的Sroll2重新处理。我们找到了同步子光谱指数空间变化的证据，也没有证据表明灰尘的去极化。使用HFI Sroll2映射，并在光谱指数上应用宽幅先验，我们在beta-sync = -2.833 +-0.620的未掩盖的天空上找到平均极化的同步子光谱指数。对于偏振粉尘发射，我们获得β-盘= 1.429 +-0.236。我们的方法返回了天空模型所有组件的不确定性。使用我们恢复的CMB图和相关的不确定性，我们使用基于跨光谱的似然性 - 附近敏化方案（Momento）将光学深度限制为电去离子Tau，以tau = 0.0598 +-0.0059。我们使用基于像素的可能性（Pixlike）确认我们的发现。在这两种情况下，我们都获得了与通过减去空间均匀前景模板所发现的Sigma的一部分相一致的结果。尽管后一种方法足以容纳普朗克的当前极化数据，但下一代太空携带的CMB实验将需要更强大的方案，例如此处介绍的方案。
We present a Bayesian parametric component separation method for polarised microwave sky maps. We solve jointly for the primary cosmic microwave background (CMB) signal and the main Galactic polarised foreground components. For the latter, we consider electron-synchrotron radiation and thermal dust emission, modelled in frequency as a power law and a modified blackbody respectively. We account for inter-pixel correlations in the noise covariance matrices of the input maps and introduce a spatial correlation length in the prior matrices for the spectral indices beta. We apply our method to low-resolution polarised Planck 2018 Low and High Frequency Instrument (LFI/HFI) data, including the SRoll2 re-processing of HFI data. We find evidence for spatial variation of the synchrotron spectral index, and no evidence for depolarisation of dust. Using the HFI SRoll2 maps, and applying wide priors on the spectral indices, we find a mean polarised synchrotron spectral index over the unmasked sky of beta-sync = -2.833 +- 0.620. For polarised dust emission, we obtain beta-dust = 1.429 +- 0.236. Our method returns correlated uncertainties for all components of the sky model. Using our recovered CMB maps and associated uncertainties, we constrain the optical depth to reionization, tau, using a cross-spectrum-based likelihood-approximation scheme (momento) to be tau = 0.0598 +- 0.0059. We confirm our findings using a pixel-based likelihood (pixlike). In both cases, we obtain a result that is consistent with, albeit a fraction of a sigma higher than, that found by subtracting spatially uniform foreground templates. While the latter method is sufficient for current polarisation data from Planck, next-generation space-borne CMB experiments will need more powerful schemes such as the one presented here.
