Weak lensing detection and analysis of galaxy clusters in CFHT and VST surveys

摘要

This thesis discusses weak gravitational lensing as a method to obtain a completecensus of galaxy clusters, the most massive cosmic systems, with mass up to ～ 1015M☉and to calibrate their empirical scaling relations.Galaxy clusters are important cosmological probes, as their mass function is a sensible function of the cosmological parameters.Weak gravitational lensing offers the unique possibility of a robust measurementof galaxy clusters mass, regardless any assumption about their dynamical state or masscomposition.
　　This technique requires wide and deep surveys of the sky (i.e., several hundreds ofsquare degrees) in order to be effective and with results comparable with more traditionalones.First effective weak lensing surveys of galaxy clusters have been possible onlyrecently, with the advent of wide field detectors on 4m-class telescopes.
　　In October 2011, a new, promising survey machine, the VLT Survey Telescope, hasstarted its scientific operations.Two complementary surveys are aim at the detectionof weak lensing phenomena by galaxy clusters, the wide and shallow survey KiDS (KiloDegree Survey) covering 1500 square degrees, and the deep survey VOICE (VST OpticalImaging of the CDFS and ES1 Fields), over 8 square degrees.
　　The goal of this Thesis is twofold.①Birst we aim at using the weak lensing pipelinedeveloped in our team to build a catalog of mass-selected galaxy clusters and studytheir scaling relations at intermediate redshift, by using well characterized data from theCanada France Hawaii Telescope.②Second, we use recent data from the VST in order totest its performance as a weak lensing machine, effort done here for the first time.

目录

Abstract

Contents

Acknowledgments

Chapter 1 Introduction

1．1 The standard cosmological model

1．2 Galaxy clusters used as cosmological probes

1．2．1 Physical properties

1．2．2 Mass estimation

1．2．3 Scaling relations

Chapter 2 Theory of gravitational lensing

2．1 Historical background

2．2 Examples of GL

2．2．1 Deflection by a point mass M

2．2．2 Deflection by a generic mass distribution

2．3 The lens equation

2．4 Deflection and Fermat potentials

2．5 GL：observational effects

2．5．1 Multiple images

2．5．2 Magnification

2．5．3 Shape distortions

2．5．4 Time delay

2．6 Strong lensing by galaxies

2．6．1 Mass determination

2．6．2 Mass models

2．7 Weak lensing

2．7．1 Detection of galaxy clusters

Chapter 3 Shear measurements

3．1 Dataset

3．1．1 The Canada-France-Hawaii-Telescope (CFHT)

3．1．2 The CFHT Legacy Survey

3．2 Image analysis step-by-step

3．2．1 S-Extractor

3．2．2 Masking noisy regions

3．3 Correction of the anisotropic part of the Point Spread Function

3．4 Two-point correlation analysis

Chapter 4 2-D mass profile of candidate galaxy clusters

4．1 The mass aperture statistics

4．2 Convergence maps from measured shear

4．2．1 Statistics of the convergence map

4．3 Galaxy clusters catalog by weak lensing

4．4 Properties and mass estimation of candidate galaxy clusters

4．4．1 Scaling relations

4．5 2-D mass profile for CFHTLenS catalog of massive clusters

Chapter 5 VST data：a first weak lensing analysis

5．1 The VLT Survey Telescope

5．2 VST surveys

5．2．1 The SUDARE／VOICE project

5．2．2 The COSMOS field

5．2．3 The Chandra Deep Field South

5．3 VST data analysis

5．3．1 The VST mosaics (COSMOS，CDFS)

5．3．2 PSF anisotropy

5．3．3 Shear measurements

5．4 VST weak lensing analysis in the next future

Appendix A The singular isothermal sphere (SIS) density profile

Appendix B Gravitational lensing in the Schwarzchild spacetime

Appendix C The angular diameter distance

Appendix D The Point Spread Function

Bibliography

声明