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arXiv 2408.13612astro-ph.CO
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对重构的CMB引力透镜功率谱中旋转诱导偏差的高效估计

Efficient estimation of rotation-induced bias to reconstructed CMB lensing power spectrum

Hongbo Cai, Yilun Guan, Toshiya Namikawa, Arthur Kosowsky

备注：
12 pages, 3 figures, Accepted for publication in PRD
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AI总结：

本研究识别出各向异性旋转导致的类$N_L^{(1)}$噪声是CMB引力透镜功率谱重构偏差的主因，给出其解析表达式与模拟估计量，构建了有效数值框架以建模和缓解该偏差，助力未来CMB实验的宇宙学参数测量。

摘要：

宇宙微波背景（CMB）引力透镜功率谱是研究晚期宇宙的有力工具，蕴含着中微子质量总和、暗能量状态方程等宇宙学参数的宝贵信息。然而，各向异性宇宙双折射的存在会使利用CMB偏振图重构的CMB引力透镜功率谱产生偏差，尤其在小尺度上更为明显，进而影响对这些参数的约束。即将开展的、以偏振引力透镜信号为主的实验尤其容易受到这种偏差的影响。我们确定了该偏差的主要贡献项为一种类似$N_L^{(1)}$的噪声，它由各向异性旋转而非引力透镜引起。我们表明，对于类CMB-S4的实验而言，标准差为0.05度的标度不变各向异性旋转场，对小尺度引力透镜功率谱（$L\boldsymbol{\nu}_{i}}=50~\rm{meV}$的有质量中微子的影响程度相当，这使得旋转场成为未来CMB实验中微子质量测量的一种重要简并源。我们给出了这种类似$N_L^{(1)}$噪声的解析表达式和基于模拟的估计量，可用于未来实验中高效的预测和偏差缓解。此外，我们研究了非标度不变旋转功率谱对重构引力透镜功率谱的影响，发现小尺度旋转功率谱的功率过剩会导致更大的偏差。我们的工作提供了一个有效的数值框架，可在未来的CMB引力透镜测量中准确建模并考虑各向异性旋转引起的偏差。

英文摘要：

The cosmic microwave background (CMB) lensing power spectrum is a powerful probe of the late-time universe, encoding valuable information about cosmological parameters such as the sum of neutrino masses and dark energy equation of state. However, the presence of anisotropic cosmic birefringence can bias the reconstructed CMB lensing power spectrum using CMB polarization maps, particularly at small scales, and affect the constraints on these parameters. Upcoming experiments, which will be dominated by the polarization lensing signal, are especially susceptible to this bias. We identify the dominant contribution to this bias as an $N_L^{(1)}$-like noise, caused by anisotropic rotation instead of lensing. We show that, for an CMB-S4-like experiment, a scale-invariant anisotropic rotation field with a standard deviation of 0.05 degrees can suppress the small-scale lensing power spectrum ($L\gtrsim 2000$) at a comparable level to the effect of massive neutrino with $\sum_i m_{ν_{i}}=50~\rm{meV}$, making rotation field an important source of degeneracy in neutrino mass measurement for future CMB experiments. We provide an analytic expression and a simulation-based estimator for this $N_L^{(1)}$-like noise, which allows for efficient forecasting and mitigation of the bias in future experiments. Furthermore, we investigate the impact of a non-scale-invariant rotation power spectrum on the reconstructed lensing power spectrum and find that an excess of power in the small-scale rotation power spectrum leads to a larger bias. Our work provides an effective numeric framework to accurately model and account for the bias caused by anisotropic rotation in future CMB lensing measurements.

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