标题： 宇宙偶极子与横向本征速度对齐的探测 显示英文标题

标题： Detection of cosmological dipoles aligned with transverse peculiar velocities

摘要： 奇点速度编码了丰富的宇宙学信息，但其横向分量难以测量。 在这里，我们展示了横向速度的一种新效应的首次观测结果：它们在宇宙微波背景（CMB）上留下的偶极子特征。 奇点速度场指向引力井并远离势能丘陵，反映了大尺度上的引力势偶极子，在数百兆秒差距范围内具有连贯性。 类似的偶极子也将在所有与势能相关的其他场中存在。 这些偶极子可以通过引力透镜和积分 Sachs-Wolfe（ISW）效应在CMB天空投影中轻松观察到——两者都与横向奇点速度相关联。 大尺度ISW偶极子不同于小尺度移动透镜效应，后者具有相反符号的偶极子。 我们提供了一个统一的框架来分析这些与速度相关的偶极子，并演示了如何通过星系属性、CMB温度和透镜的天空图叠加提取信号。 我们表明，CMB偶极子信号独立于星系偏差，并且与通常的方向平均相关函数正交，因此这一新的可观测量提供了额外的宇宙学信息。 我们使用SDSS-III BOSS调查中的星系和Planck的CMB地图，首次检测到（i）星系密度；（ii）CMB透镜收敛；以及（iii）CMB温度——解释为ISW效应——的偶极子信号。 我们表明，观测到的信号与$\Lambda$CDM预测一致，并利用透镜和ISW结果限制了修改重力线性模型。 显示英文摘要

摘要： Peculiar velocities encode rich cosmological information, but their transverse components are hard to measure. Here, we present the first observations of a novel effect of transverse velocities: the dipole signatures that they imprint on the Cosmic Microwave Background. The peculiar velocity field points towards gravitational wells and away from potential hills, reflecting a large-scale dipole in the gravitational potential, coherent over hundreds of Mpc. Analogous dipoles will also exist in all other fields that correlate with the potential. These dipoles are readily observed in projection on the CMB sky via gravitational lensing and the integrated Sachs-Wolfe (ISW) effect -- both of which correlate with transverse peculiar velocities. The large-scale ISW dipole is distinct from the small-scale moving lens effect, which has a dipole of the opposite sign. We provide a unified framework for analysing these velocity-related dipoles and demonstrate how stacking can extract the signal from sky maps of galaxy properties, CMB temperature, and lensing. We show that the CMB dipole signal is independent of galaxy bias, and orthogonal to the usual direction-averaged correlation function, so this new observable provides additional cosmological information. We present the first detections of the dipole signal in (i) galaxy density; (ii) CMB lensing convergence; and (iii) CMB temperature -- interpreted as the ISW effect -- using galaxies from the SDSS-III BOSS survey and CMB maps from Planck. We show that the observed signals are consistent with $\Lambda$CDM predictions, and use the combined lensing and ISW results to set limits on linearised models of modified gravity.