arXiv 2602.045042026-02astro-ph.CO

弱引力透镜低多极子

Weak Lensing Low Multipoles

Sorbonne Université, CNRS, Institut d’Astrophysique de Paris（索邦大学，法国国家科学研究中心，巴黎天体物理学研究所）；Rudolf Peierls Centre for Theoretical Physics, University of Oxford（鲁道夫·派尔斯理论物理中心，牛津大学）

Albert Bonnefous, Roya Mohayaee

备注：: Match the version published in MNEAS
发表信息：: Mon Not R Astron Soc (2026)
DOI：: 10.1093/mnras/stag633

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AI总结：

研究弱引力透镜收敛场低多极子成分，分析其在ΛCDM模型中的表现，并探讨其对宇宙各向异性异常的贡献。

摘要：

我们分析了在FLRW宇宙中弱引力透镜收敛场的低多极子成分。低多极子收敛场编码了大角度相干势梯度，对于评估数据中的大角度特征至关重要。为了研究这一大角度信号，我们进行了结合分析、数值和观测研究。从收敛功率谱的精确解析表达式出发，我们量化了二阶、四阶和八阶多极子随源红移的变化，并显示在ΛCDM模型中它们的振幅达到约10^-4量级。然后我们使用全天空、视界尺度的N体模拟（Quijote）来探索该信号对观测者环境的依赖性，比较随机观测者与“银河系类”观测者。同时，我们利用2MASS红移巡天（2MRS）重建本地宇宙的收敛场，并正确处理不完整性和星系偏置。我们发现观测到的低多极子高于ΛCDM均值预测，但在模拟中与“银河系类”观测者一致。最后，通过将收敛二阶多极子转换为数数二阶多极子，我们测试弱引力透镜是否能对宇宙各向异性异常做出贡献，这一想法受到其与CMB二阶各向异性自然对齐的启发，以及由于透镜作用不同于聚类作用，无法通过交叉匹配调查去除，因此在所有高红移目录中都得以保留。我们显示弱引力透镜由本地结构贡献最多几百分比到这一观测到的异常。

英文摘要：

We analyse the low--multipole components of the weak-lensing convergence field in a FLRW universe. The low--multipole convergence field, encodes the largest-angle coherent potential gradients, essential for assessment of large-angle features in data. To study this large angle signal, we perform a combined analytical, numerical and observational study. Starting from exact analytical expressions for the convergence power spectrum, we quantify how the dipole, quadrupole and octupole build up with source redshift and show that, in $Λ$CDM, they saturate at an amplitude of order $10^{-4}$. We then use full-sky, horizon-scale $N$-body simulations (Quijote) to explore the dependence of this signal on the observer's environment, comparing random observers to ``Milky Way--like'' observers. In parallel, we reconstruct the convergence field due to our local Universe with the 2MASS Redshift Survey (2MRS), with proper treatment of incompleteness and galaxy bias. We find that the observed low multipoles from observation is above the $Λ$CDM mean predictions, but in full agreement with Milky Way--like observers in the simulation. Finally, by converting the convergence dipole into a number-count dipole, we test whether weak lensing can contribute to the cosmic dipole anomaly, an idea motivated by its natural alignment with the CMB dipole and by the fact that lensing, unlike clustering, cannot be removed by cross-matching surveys and thus survives in all high-redshift catalogues. We show that weak lensing by local structure contributes at most a few percent to this observed anomaly.

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