We examine the statistical properties of polarization maps from Planck 2018 within the patch of sky observed by the BICEP2/Keck experiment using the one point distribution function (1PDF), skewness, and kurtosis statistics. Our analysis is performed for the Q and U Stokes parameters and for the corresponding E- and B-modes of the CMB signals. We extend our analysis by studying the correlations between CMB polarization maps and residual maps (the difference between the full signal and the CMB map) for the frequency range of 100--217 GHz with both the Q/U and E/B approaches. Although all the CMB maps reveal almost Gaussian statistical properties for Q/U and E/B domains, we have detected very significant anomalies for cross-correlations with residuals at 100 GHz at the level of $3.7\sigma$ for the Commander map and $5.2\sigma$ for NILC, for both the Q and U parameters. Using the NILC--Commander difference, which does not contain a cosmological signal, we find a sub-dominant non-Gaussian component in Q skewness and kurtosis at the level of $4.3\sigma$ and $10\sigma$, respectively. For the B-mode we have found a very high level of cross-correlation (0.63--0.69) between the NILC/Commander maps and the 143 GHz total signal, which cannot be associated with the cosmological component. These strong deviations suggest that remnants of foregrounds, systematic effects, and component separation exist in the 2018 Planck CMB polarization maps in the BICEP2 sky area, which is far away from the Galactic plane. Our analysis also demonstrates the preferability of the Q/U domain over E/B for determination of the statistical properties of the derived CMB signals, due to non-locality of the transition Q/U $\rightarrow$ E/B.

中文翻译：

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BICEP2/Keck 区域普朗克 2018 CMB 偏振图的比较

我们使用一点分布函数 (1PDF)、偏度和峰态统计量检查了 BICEP2/Keck 实验观察到的天空斑块内普朗克 2018 偏振图的统计特性。我们对 Q 和 U Stokes 参数以及 CMB 信号的相应 E 和 B 模式进行了分析。我们通过使用 Q/U 和 E/B 方法研究 100--217 GHz 频率范围内 CMB 极化图和残差图（完整信号和 CMB 图之间的差异）之间的相关性来扩展我们的分析。尽管所有 CMB 地图都显示 Q/U 和 E/B 域的几乎高斯统计特性，但我们已经检测到非常显着的与 100 GHz 残差的互相关异常，Commander 地图的 $3.7\sigma$ 和 $5.2\西格玛 $ 为 NILC，对于 Q 和 U 参数。使用不包含宇宙学信号的 NILC--Commander 差异，我们在 Q 偏度和峰度中分别在 $4.3\sigma$ 和 $10\sigma$ 的水平上找到了一个次显性的非高斯分量。对于 B 模式，我们发现 NILC/Commander 地图和 143 GHz 总信号之间存在非常高的互相关 (0.63--0.69)，这与宇宙学分量无关。这些强烈的偏差表明，2018 年普朗克 CMB 偏振图中的 BICEP2 天空区域存在前景残留、系统效应和分量分离，该区域远离银河平面。我们的分析还证明了 Q/U 域优于 E/B，用于确定导出的 CMB 信号的统计特性，