阿里原初引力波探测计划的去透镜预研究  

Forecast on the delensing of AliCPT-1 project

作　　者：韩嘉康 曹烨 胡彬 HAN JiaKang;CAO Ye;HU Bin(Institute for Frontier in Astronomy and Astrophysics,Beijing Normal University,Beijing 102206,China;Department of Astronomy,Beijing Normal University,Beijing 100875,China)

机构地区：[1]北京师范大学天文与天体物理前沿所,北京102206 [2]北京师范大学天文系,北京100875

出　　处：《中国科学：物理学、力学、天文学》2023年第11期215-223,共9页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家重点研发计划(编号:2020YFC2201603)资助项目。

摘　　要：前景大尺度物质密度结构会通过引力相互作用产生对原初宇宙微波背景(CMB)光子偏振模式的畸变,将一部分CMB的E模偏振转化为B模偏振.该效应产生的B模偏振信号被称为透镜B模.透镜B模会对由原初引力波产生的原初B模偏振信号产生强烈的污染.为了探测微弱的原初B模信号,我们需要在天图层面上对透镜B模进行扣除,该操作被称为“去透镜”.阿里原初引力波探测计划1期(AliCPT-1)是国际上首个位于北半球的地基毫米波宇宙学巡天观测计划.本文基于5个观测季的模拟数据分析了AliCPT-1的“透镜重构”和“去透镜”能力.对于“透镜重构”,我们发现透镜重构的信噪比可以达到SNR=13.4.对于“去透镜”,我们采用了只依赖CMB数据的“内部”和需要引入宇宙红外背景数据的“外部”两种不同的去透镜方案.我们发现,“内部去透镜”方案在球谐多极矩l=200处的去透镜效率最高,约为10%;而“外部去透镜”方案则更为有效,最大去透镜效率出现在l■100处,约为23%.利用外部去透镜方案,有望将对张标比的测量精度由r≤0.03降至≤0.02.The gravitational scattering from foreground large-scale structures to the primary cosmic microwave background(CMB)photons distorts the linear polarization pattern,converting E-mode into B-mode polarization.The resulting signal is referred to as Lensing-B mode,which strongly contaminates measurements of the primordial B-mode produced by primordial gravitational waves.To measure the primordial B-mode with a high degree of precision,we must subtract the Lensing-B mode at the map level.This operation is called delensing.The Ali CMB polarization telescope 1st-phase project(AliCPT-1)is the first ground-based cosmological millimeter survey in the northern hemisphere.This article forecasts AliCPT-1’s lensing reconstruction and delensing capacity based on simulated data over five seasons.A signal-to-noise ratio of 13.4 can be achieved for lensing reconstruction.Two methods were employed for delensing:the“internal”and“external”methods.The former relies solely on CMB data,while the latter requires cosmic infrared background data.Furthermore,we find that the delensing efficiency of the internal method is lower than that of the external method.The maximum delensing efficiency for the internal method peaks at the spherical harmonic modeℓ=50 with an amplitude of 10%,whereas that of the external method peaks atℓ≃200 with an amplitude of 20%.The external delensing method could improve the measured value of the tensor-to-scalar ratio from r≤0.03 to r≤0.02.

关 键 词：宇宙微波背景辐射 引力透镜 宇宙学 

分 类 号：P142.84[天文地球—天体物理]