Avoiding The Geometric Boundary Effect In Shear Measurement

Weak lensing is a powerful probe in cosmology.In this paper,we mainly focus on the method of shear measurement and systematic error in it.In chapter 1,we introduce the corresponding gravitational lensing knowledge and the method of shear measurement,especially Fourier＿Quad method.In chapter 2,we introduce the Fourier＿Quad pipeline which is based on Fourier＿Quad method and other steps such as background removal,source detection,etc in data analyzing.In chapter 3,we introduce the systematic error in shear signal,especially the additive bias generated by the geometric boundary effect.These boundary conditions make the source detection process not statistically isotropic.It can lead to additive shear bias near the boundaries.We build a phenomenological model to understand the bias,and propose a simple method to effectively eliminate the influence of geometric boundaries on shear measurement.We demonstrate the accuracy and efficiency of this method using both simulations and the z-band imaging data from the third data release of the DECam Legacy Survey.In chapter 4,we summarize the whole paper and briefly introduce the planned research about matter field reconstruction.This work can give us a better constrained cosmological parameters.