Probing the dark universe with gravitational lensing

Abstract

Since its early success as an experimental test of the theory of general relativity in 1919, gravitational lensing has come a long way and is firmly established as an indispensable element for many astrophysical applications. In this thesis, we explore novel applications of gravitational lensing that further our understanding of the dark sectors of the cosmos and other astrophysical objects, namely dark matter nanostructure, black holes and the Galactic disk. We pay particular attention to developing concrete and optimal statistical methodologies and numerical implemen- tations for these novel probes. We start by developing a statistical framework to measure the dark matter power spectrum in the deep nonlinear regime, using transient weak lensing, and simultaneously measure the time delays for strongly lensed quasars. We then outline how observations of microlensing in optical and radio can unravel the structure, dynamics, and content of the Galactic disk, and in particular, be used to detect stellar mass black holes. Lastly, using the shadow images of the super-massive black holes caused by extreme lensing effect, we can learn about the structure of space-time, accretion flows and astrophysical jets. We present a Bayesian framework for analyzing the data from the Event Horizon Telescope Collaboration.