学术报告—How to make a weak lensing convergence map?

报告摘要：

A weak lensing convergence(kappa) map, comparing to its counterpart of shear catalog, is more straightforwardly connected to the underlying matter field, and is more convenient to perform analysis of 2pt and beyond-2pt summary statistics. However, making such a kappa map is highly non-trivial and existing methods often fail to meet the requirement of precision cosmology. We present map making methods for both cases of cosmic shear and cosmic magnification. (1) For cosmic shear, we present the Accurate Kappa Reconstruction Algorithm (AKRA) for masked shear catalog. Unlike other methods, it solves the issue of masks robuslty from first principle and acurately reconstruct the kappa map, as verified by simulated mocks. We will aply AKRA to HSC and DES. (2) For cosmic magnification, we modify the internal linear combination algorithm, surpress the otherwise overwhelming contamination of galaxy intrinsic clustering by 2 orders of magnitude, and reconstruct kappa maps by counting DECaLS and DES galaxies. We also find issues in the reconstruction, which will be improved by better data with higher galaxy number density and better determination of the cosmic magnification response coefficient.

报告人简介：

张鹏杰，上海交通大学教授，天文系系主任。从事宇宙学研究，重点是宇宙大尺度结构及其在基础物理中的应用，包括宇宙微波背景辐射次级各向异性（SZ效应、ISW效应、CMB lensing等）、弱引力透镜、星系红移畸变与本动速度场、广义相对论的宇宙学检验等。