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Galaxy clusters are the largest gravitationally bound structures in the Universe. Thought to form through a process of hierarchical merging, exactly how and when they form, and what happens to the galaxies within these dense environments, is still to be determined. At high redshifts we can find dense regions of space that we expect will evolve into a galaxy cluster by the present day but finding these regions, known as protoclusters, is difficult. Finding protoclusters is the main aim of this thesis and Chapters 3, 5 and 6 detail searches for protoclusters around quasars, sub-millimetre galaxies and radio galaxies, finding evidence that radio galaxies lie in the densest environments and sub-millimetre galaxies in the least dense on average. The protoclusters found are compared to simulations such as the Millennium Simulation in order to predict their eventual fate. The properties of the galaxies within these dense environments are also explored with reference to galaxies in the field, and in particular Chapter 4 presents a study of one interacting quasar system at z = 3.2 in detail. However, to fully understand galaxy and cluster evolution we must study both the high redshift protoclusters, and the highest redshift, virialised galaxy clusters, exploring how galaxy clusters continue to grow and evolve once they have formed and how these dense environments affect the galaxies within them. In Chapter 7 I present a sample of such high red shift galaxy clusters and explore their X-ray and infrared properties. This thesis reviews the work I have done over the last three and half years on the subject of galaxy clusters and protoclusters, starting with high redshift protoclusters and looking at the next 6 billion years of cluster evolution through the subsequent chapters.

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General Relativity (GR) is Einsteins' theory of gravity whereby the motions of bodies are explained due to their following geodesic paths (the shortest distance between two points) in a curved four dimensional space-time. The curvature being attributed to the presence of mass As such there is no explicit force present in this theory, contrary to Newtons' law of gravity. However in the limit of GR (where the field is both weak and static and bodies are travelling with velocities slow compared to that of light), then Newtons' law is recovered in the approximation. GR has explained all gravitational phenomena extremely well (eg solar system), that is until one considers the measured motions of galaxies. The galaxies are rotating too quickly to be consistent with GR/ Newton. An explanation for this discrepancy has originally been suggested, concerning the presence of extra mass, of as yet an unknown nature. However, to date not a hint of this `Dark Matter' has been detected. A second explanation is that of Modified Newtonian Dynamics (MOND), whereby at a certain very small acceleration, the actual gravitational physics deviates from that described by Newton. The MOND proposal seems to fit extremely well with observations without the need to invoke the presence of DM. The main problem with the MOND concept is that it does not fit in with the standard GR. ii The following work details an exploration into the novel assumption that the presence of mass is not only responsible for the curvature of space-time but also for a local expansion of space-time. By introducing an expansion factor at the very beginning of standard GR analysis, one �nds an extra term appears which is consistent throughout. With the inclusion of this extra term, one can, in the weak, static and slow velocity limit, �nd a direct link to the MOND phenomenology. It is found that the extra term is negligible for small systems (eg Solar) yet it is the dominant term for large systems (eg galaxies).

This thesis presents the results of several projects on the analysis of infrared observations of star-forming galaxies, all of which included observations by the AKARI Space Telescope. Spectroscopic redshifts have been measured for over 400 galaxies using the fibre spectrograph AAOmega in the AKARI Deep Field South, the first significant spectroscopic campaign in a relatively new, cirrus-free deep field. A local luminosity function of galaxies in this field is also presented, using far-infrared data from AKARI. Various properties are deduced from the atomic emission lines detected, and star-forming spectral energy distribution templates are fitted to these sources using the multi-wavelength data available. The majority of these galaxies are dominated by emission from star formation, and local sources show relatively low dust extinction. AKARI’s own near-infrared spectroscopic facility was used to observe well-known submillimetre targets in other well-studied deep fields. The most interesting result was the detection of high redshift (z > 3.5) Hα emission lines in two radio galaxies and two submillimetre galaxies shown to be associated with one of them, the highest-redshift Hα detections so far discovered in star-forming galaxies. Both radio galaxies are shown to be quasars, and one is part of a binary quasar. The result from stacking all the Hα targets is also presented. Two Graphic User Interfaces (GUIs) were written to help with these projects and are described in this thesis. Finally, the early results of an ongoing experiment to detect gravitational lenses by identifying quasars with enhanced far-infrared luminosity are presented, with about twenty quasars identified in the AKARI all-sky far-infrared survey. Several sources at high redshift appear to show enhanced luminosity, and follow-up optical spectroscopy of seven of these sources shows that three are high-redshift quasars.

Solid-state astrochemistry experiments have recreated the physical conditions of the interstellar medium (ISM) in a controlled laboratory environment, but traditionally neglected to employ realistic dust analogues. In the past decade only a few experiments focused on the effect of the underlying substrate on physical and chemical properties of ices. At the same time, current nanofabrication technologies enable us to reliably manufacture nano-structured surfaces with high-reproducibility over large areas. This thesis combines these two ideas and aims to produce and exploit nanotemplated surfaces such that each nanoparticle is representative in size, shape, and material of an "ideal" interstellar dust grain. Surfaces of silicaceous and carbonaceous materials have been manufactured and characterised, singularly and in combination, for this purpose. The optical properties of these surfaces are heavily influenced by the presence of nanoparticles. The "composite" surfaces show that even small layers of silica on carbon or vice-versa rapidly change the optical properties of the surface. The formation of water ice layers on the surfaces indicated topography-dependent growth and variation in intermolecular bonding co-ordination. Finally, a study of how the overlying media affects the ultra- violet extinction properties of these substrates indicates that it is vital to understand the growth regime of the icy material, because island growth and clumping of ices can lead to scattering rather than absorption of radiation, thus affecting laboratory data. In summary, this thesis shows how the nano-surfaces do affect chemical and physical properties of the ices on top of them, and particle size can affect the outcomes of astrochemical ice experiments. This work is a first step into extending astrochemistry research to using more realistic ISM dust size and material models, opening a plethora of routes for future laboratory studies.

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This thesis deals with the practical application of Weak Gravitational Lensing (WGL) as a tool for studying two of the most challenging problems in modern cosmology: the nature of dark energy and tests of Einstein’s General Relativity. To be a useful tool, WGL must be able to put robust constraints on the parameters of interest even in the presence of a strong systematic effect like the Intrinsic Alignment (IA) of galaxies. In chapter 2 we demonstrate how ignoring the effect of IAs will lead to strongly biased measurements of cosmology. We introduce a simple IA model and demonstrate how the bias can be removed, at the cost of weaker constraints, by marginalising over nuisance parameters in the model. We present the first joint constraints on IAs and cosmology from WGL and galaxy position information. The combination returns errorbars of the same order as the naive WGL calculation which ignored IAs. We extend the IA model to treat shear and position correlations in a unified way with > 100 nuisance parameters. We parameterise deviations from GR and show, in chapter 3, how the considerable (~75%) decrease in constraining power caused by IAs can be partially mitigated by the inclusion of position-position and shear-position correlations. In chapter 4 we find these results to extend across a wide range of survey specifications. We find that increased survey area is not always favoured at the expense of source density and that the impact of improved redshift knowledge is not dramatic. In chapters 5-7 we note the potentially very powerful constraints from a joint analysis of WGL and Redshift Space Distortions (RSDs) from a spectroscopic survey. We summarise some important preparatory work for future cosmic shear surveys and advances in shear measurement techniques before concluding and describing some directions for future work.