UC Irvine

The Universe’s mass is predominately comprised of dark matter, yet its exact particle nature remain elusive. The dark energy (Λ) plus Cold Dark Matter (ΛCDM) model of cosmology reigns as the prevalent model of our Universe, as it matches the observed large-scale structure. The formation mechanism of these so-called dark matter halos introduces many possible particle candidates for CDM models and further manifests attributes in the global abundance and the underlying mass distribution. Precise detection of these objects in the low-mass regime could further pave way to revealing the particle nature of dark matter. An exciting route to reveal the existence of dark matter structures within our Universe that have mass scales smaller than the faintest galaxies (i.e., Ultra-faint Dwarfs) is based on their lingering presence on strong gravitational lensed systems. The contents within this thesis provides, for the first time, in depth analysis of crucial lensing quantities derived from numerical simulations of dark matter halos and galaxies within the ΛCDM paradigm. Importantly, we explore models pertaining to the “line-of-sight” (LOS; i.e., field) perturbers, as these are one of most contributing population of dark matter halos to significantly impact the lensing signal, as compared to the subhalo population. We demonstrate that clustering in the vicinity of the lens host halo is an important component in any lensing configuration, as it produces a clear enhancement to the lensing signal relative to an assumption of unclustered halos with substructure. We also introduce an analytical surface density profile for low-mass dark matter halos that are parameterized by the so-called “projected concentration”, making it useful for modeling LOS perturbers in strong gravitational lensing models. Finally, we then extend this surface density model using a statistical sample of simulated dark matter halos to infer the median evolution of the projected concentration and the scatter as a function of mass.

The framework developed here inevitably broadens the scope of strong-lensing analyses for probing dark matter in a ΛCDM universe, thus demonstrating the power of strong gravitational lensing as a unique probe of dark matter physics.