Testing for spectral index variations in polarized CMB foregrounds
Testing for spectral index variations in polarized CMB foregrounds
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测试偏振 CMB 前景中的光谱指数变化
DOI：
10.1093/mnras/stac2825
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发表时间：
2022
影响因子：
4.8
通讯作者：
De Belsunce R
中科院分区：
文献类型：
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作者：
De Belsunce R
我们提出了一种用于偏振微波天空图的贝叶斯参数分量分离方法。我们联合求解主要宇宙微波背景（CMB）信号和主要银河偏振前景分量。对于后者，我们考虑电子同步辐射和热尘埃发射，分别以幂律和修正黑体的频率建模。我们考虑输入图的噪声协方差矩阵中的像素间相关性，并在频谱索引 β 的先验矩阵中引入空间相关长度。我们将我们的方法应用于低分辨率极化 Planck2018 低频和高频仪器 (LFI/HFI) 数据，包括 HFI 数据的 SRoll2 重新处理。我们发现了同步加速器光谱指数空间变化的证据，但没有发现尘埃去极化的证据。使用 HFISRoll2maps，并对光谱指数应用广泛的先验，我们找到了未遮蔽的天空上的平均偏振同步加速器光谱指数。对于偏振热粉尘发射，我们得到。使用我们恢复的 CMB 图和相关的不确定性，我们使用基于跨谱的似然近似方案（动量）将光学深度限制为再电离 τ = 0.0598 ± 0.0059。我们使用基于像素的可能性 (pixLike) 证实了我们的发现。在这两种情况下，我们获得的结果与通过减去空间均匀前景模板得到的结果一致。虽然后一种方法足以满足当前来自普朗克的偏振数据，但下一代星载宇宙微波背景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 polarized microwave sky maps. We solve jointly for the primary cosmic microwave background (CMB) signal and the main Galactic polarized 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 β. We apply our method to low-resolution polarizedPlanck2018 Low and High Frequency Instrument (LFI/HFI) data, including theSRoll2re-processing of HFI data. We find evidence for spatial variation of the synchrotron spectral index, and no evidence for depolarization of dust. Using the HFISRoll2maps, and applying wide priors on the spectral indices, we find a mean polarized synchrotron spectral index over the unmasked sky of. For polarized thermal dust emission, we obtain. Using our recovered CMB maps and associated uncertainties, we constrain the optical depth to reionization, τ, using a cross-spectrum-based likelihood-approximation scheme (momento) to be τ = 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 that found by subtracting spatially uniform foreground templates. While the latter method is sufficient for current polarization data fromPlanck, next-generation space-borne CMB experiments will need more powerful schemes such as the one presented here.