Constraining cosmology and galaxy evolution with highly multiplexed spectroscopy

• Main Author: MacKenzie, Ruari
• Published: Durham University 2018
• Subjects: 530
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.753801

The scientific questions addressed in this thesis divide into fundamental cosmology and galaxy evolution, although divergent in theme these are connected by the use of high multiplex spectroscopy. Specifically, we employ spectroscopic galaxy redshift surveys to probe the connection between galaxies and the Cosmic Microwave background, and to link galaxies to neutral gas reservoirs which contain fuel for star-formation. We present the following observational investigations: 1. A spectroscopic redshift survey of $\sim$7000 galaxies in the core of the Cosmic Microwave Cold Spot, with the aim of following up the claim of a supervoid capable of imprinting the Cold Spot via the Integrated Sachs-Wolfe effect. Using 2dF+AAOmega we have surveyed 66 deg$^2$ out to $z < 0.5$, using a $i\leq19.2$ magnitude limited selection based on imaging from the VST-ATLAS Survey. We confirm the presence of a void at $z=0.14$ with a scale radius of 119h$^{-1}$ Mpc and a density contrast of $\delta_{m}=-0.34$, however it is deeper and much less extended than previously claimed. The $\Lambda$CDM ISW imprint of this void is only -6.25 $\mu$K, compared to the Cold Spot’s central temperature of $\sim$150 $\mu$K . We detect further under-densities at $z=0.26$ and $0.30$, although these contribute even less to the temperature decrement than the larger $z=0.14$ void. When combined with previous data we can exclude a large contribution to the Cold Spot from a void at $z < 1$, at higher redshift the ISW effect is less significant. Similarity between our control field and the Cold Spot survey places constraints on any non-standard attempt to link the voids to the CMB Cold Spot. 2. An integral field survey of six $z\simeq3.5$ Damped Lyman $\alpha$ systems with MUSE, to search for host galaxies and to study their environments. Our survey did not preselect DLAs based on absorption properties, on the contrary of current leading DLA host searches that select only high metallicity systems. MUSE has revealed that three of the six fields contain bright Lyman $\alpha$ emitters (LAEs) with a few hundred km s$^{-1}$ of the absorption redshift, detecting associated galaxies out to larger impact parameters than was previously possible. In one field (J0255+0048) we discovered an extended Ly$\alpha$ nebula in close proximity to the DLA, extending up to 50 physical kpc from the DLA location. The object has a striking correspondence between absorption and emission components, which may indicate the structure is an ongoing merger with tidal debris at the DLA location. Our most metal-poor system (J1220+0921) was revealed with MUSE to be embedded in a dense filament-like structure, which extends across the full MUSE field of view (380 kpc). We have compared the distribution of galaxies around the DLAs to models and simulations, using the {\sc eagle} hydrodynamical simulation and a model based on the {\sc galics} semi-analytic prescription. Using these mock data we have shown our observations are consistent with both {\sc eagle} and simple halo prescription put forward to explain the strong clustering of DLAs. Furthermore we show how an expanded version of our survey may provide useful constraints on the small scale clustering of DLAs and the link between neutral gas reservoirs and star-formation.