论文标题
外乳外前景对CMB B模式极化内部删除的影响
The impact of extragalactic foregrounds on internal delensing of CMB B-mode polarization
论文作者
论文摘要
搜索CMB的原始$ b $ mode两极分化受重力透镜在以后产生的$ b $ modes的样本差异的限制。可以通过“删除”来改善约束：使用物质分布的某些代理来部分删除镜头诱导的$ b $ modes。当前和很快的实验将从CMB的温度各向异性中推断出一个物质图（至少部分）。这些重建受到静脉外的前景污染：发射射电星系，宇宙红外背景或Sunyaev-Zel'Dovich效应。使用Websy模拟，我们表明前景通过非高斯较高点功能添加了$ b $ - modes的角度自动光谱，对张量与量表比的偏见约束，$ r $ $ r $。我们考虑了类似于西蒙斯天文台的理想化实验，没有银河或大气前景。在删除可在143 GHz处检测到的点源并使用Hu-Okamoto二次估算器（QE）从CMB温度模式$ L <3500 $重建镜头后，我们推断出$ r $的值为$ 1.5 \，σ$，比True $ r = 0 $高。而不是从最小值的ILC地图重建仅加剧了问题，这使偏置超过$ 3 \，σ$。当$ tt $估算器与其他QE或外部物质示踪剂共同添加时，随后随后将其部分取消$ tt $的稀释偏置。我们提供简单有效的处方，以建模这些效果。此外，我们证明了点源固定或剪切的QE不仅可以使偏见降低到可接受的水平，而且在删除后的Hu-Okamoto QE中也会带来更低的功率。因此，基于温度的重建仍然是测量$ r $的强大工具。
The search for primordial $B$-mode polarization of the CMB is limited by the sample variance of $B$-modes produced at later times by gravitational lensing. Constraints can be improved by `delensing': using some proxy of the matter distribution to partially remove the lensing-induced $B$-modes. Current and soon-upcoming experiments will infer a matter map -- at least in part -- from the temperature anisotropies of the CMB. These reconstructions are contaminated by extragalactic foregrounds: radio-emitting galaxies, the cosmic infrared background, or the Sunyaev--Zel'dovich effects. Using the Websky simulations, we show that the foregrounds add spurious power to the angular auto-spectrum of delensed $B$-modes via non-Gaussian higher-point functions, biasing constraints on the tensor-to-scalar ratio, $r$. We consider an idealized experiment similar to the Simons Observatory, with no Galactic or atmospheric foregrounds. After removing point sources detectable at 143 GHz and reconstructing lensing from CMB temperature modes $l<3500$ using a Hu-Okamoto quadratic estimator (QE), we infer a value of $r$ that is $1.5\,σ$ higher than the true $r=0$. Reconstructing instead from a minimum-variance ILC map only exacerbates the problem, bringing the bias above $3\,σ$. When the $TT$ estimator is co-added with other QEs or with external matter tracers, new couplings ensue which partially cancel the diluted bias from $TT$. We provide a simple and effective prescription to model these effects. In addition, we demonstrate that the point-source-hardened or shear-only QEs can not only mitigate the biases to acceptable levels, but also lead to lower power than the Hu-Okamoto QE after delensing. Thus, temperature-based reconstructions remain powerful tools in the quest to measure $r$.
