Probing the connection between the intergalactic medium and galaxies with quasar absorption-line spectroscopy

Abstract

In this thesis, we examine the relationship between the metal-enriched intergalactic medium (IGM) and galaxies at z < 1. In particular, we investigate the nature and consequence of feedback from active galactic nuclei (AGN) and supernovae, which shape the evolution of galaxies and are responsible for enriching the IGM with metals. The IGM is surveyed in ultraviolet (UV) absorption lines against background quasars (QSOs), whilst galaxies are surveyed in emission by means of optical photometry and spectroscopy. Simulated samples of IGM absorption systems and galaxies are also extracted from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological hydrodynamical simulation for critical comparison with the data. We present the results of two primary studies that are designed to address key questions on the nature and consequence of feedback:
1. We examine complex absorption profiles in the spectrum of a QSO at z ~ 1, that trace a metal-rich outflow originating from the host galaxy. We show that these absorption profiles originate from dense, sub-pc scale gas clumps at distances of a few kpc from the central AGN. The gas is likely to be dynamically unstable, and is potentially far from ionization equilibrium. We favour a scenario in which the clumps are formed in-situ, and are entrained in a hot (T > 10^6 K) outflowing wind that may trace the majority of the mass, but is undetected in the UV. These observations provide a detailed set of constraints on the nature of feedback in QSO host galaxies.
2. We investigate the distribution and dynamics of metal-enriched gas around galaxies at z < 1 through the two-point cross- and auto-correlation functions of OVI absorbers and galaxies (abridged)