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Abstract

Recent cosmological hydrodynamical simulations were for the first time able to produce galaxy populations with realistic sizes and morphologies. This success can be attributed to the inclusion of subgrid models for supernovae winds and active galactic nuclei (AGN) feedback. In this thesis, we investigate the impact of feedback driven galactic outflows. First, the expulsion of gas proves to be crucial for the rotational support of haloes hosting realistic galaxies. We employ the state-of-the-art hydrodynamical simulation suites Illustris and IllustrisTNG to characterise the amount of specific angular momentum in the baryonic component of haloes. We find the baryonic spin at z = 0 to be a factor of ∼ 2 higher than the dark matter spin, which is due to the transfer of a constant cumulative spin of Δλ = 0.0013 by z = 0 from dark matter to the gas during mergers, and to the preferential expulsion of low angular momentum gas by mostly AGN feedback. Second, galactic outflows impact the state of the diffuse gas on large scales. We employ the Lyman-α forest to examine the feedback induced changes in the inter-galactic medium (IGM) that serves as gas reservoir for accretion onto galaxies. For a clean comparison, we have run a suite of simulations with both galaxy formation physics and with the Quick Lyman-α (QLA) technique yielding an unperturbed IGM. We find the Lyman-α flux power spectrum to exhibit increasingly more power at large scales and correspondingly less power at small scales in the presence of outflows, as well as the IGM to be generally hotter. Employing IllustrisTNG we investigate the excess Lyman-α absorption as a function of impact parameter for haloes exhibiting strong and weak feedback and find significant differences that can largely be explained by the higher temperature of the perturbed gas.