标题： 由河外源掩模引起的透镜化CMB功率谱偏差 显示英文标题

标题： Lensed CMB power spectrum biases from masking extragalactic sources

摘要： 宇宙微波背景（CMB）被大尺度结构引力透镜效应扭曲，这会改变在特定方向上原始各向异性观测的结果。从整个天空平均来看，这种重要效应通常通过透镜化的CMB功率谱来建模。这考虑了这种扭曲的方差，其中主要的方差效应是透镜偏转的二次项。然而，我们证明，如果与大尺度结构相关的亮源在CMB图中被掩膜，那么使用标准伪-$C_\ell$估计器在未掩膜区域测量到的功率谱具有额外的~\emph{线性}透镜效应，该效应来源于掩膜区域和透镜之间的相关性。这导致未掩膜点对之间未透镜距离的尺度依赖平均去放大效应，并且对CMB相关函数产生峰值在$\sim 10\,\arcmin$的负贡献。我们给出了点源和基于相关高斯前景场的阈值掩膜的简单解析模型。我们通过现实的数值模拟验证了它们对于去除射电源、太阳泽维奇-泽尔多维奇以及宇宙红外背景辐射峰值的预测一致性。我们讨论了简单的诊断方法，可以在掩膜源没有良好模型的情况下测试该效应，并表明通过构建特定掩膜可以在这类数据上观察到该效应。对于用于分析普朗克及其他当前数据集的掩膜，该效应可能可以忽略不计，但如果大量已分辨源被掩膜，则该效应可能是未来巡天的重要亚百分比修正。 显示英文摘要

摘要： The cosmic microwave background (CMB) is gravitationally lensed by large-scale structure, which distorts observations of the primordial anisotropies in any given direction. Averaged over the sky, this important effect is routinely modelled with the lensed CMB power spectra. This accounts for the variance of this distortion, where the leading variance effect is quadratic in the lensing deflections. However, we show that if bright extragalactic sources correlated with the large-scale structure are masked in a CMB map, the power spectrum measured over the unmasked area using a standard pseudo-$C_\ell$ estimator has an additional~\emph{linear} lensing effect arising from correlations between the masked area and the lensing. This induces a scale-dependent average demagnification of the unlensed distance between unmasked pairs of observed points and a negative contribution to the CMB correlation function peaking at $\sim 10\,\arcmin$. We give simple analytic models for point sources and a threshold mask constructed on a correlated Gaussian foreground field. We demonstrate the consistency of their predictions for masks removing radio sources and peaks of Sunyaev-Zeldovich and cosmic infrared background emissions using realistic numerical simulations. We discuss simple diagnostics that can be used to test for the effect in the absence of a good model for the masked sources and show that by constructing specific masks the effect can be observed on Planck data. For masks employed in the analysis of Planck and other current data sets, the effect is likely to be negligible, but may become an important subpercent correction for future surveys if substantial populations of resolved sources are masked.