The formation and evolution of galaxies is studied using two alternative modelling techniques within the context of the LCDM cosmogony. In particular, we consider the capacity of the models to reproduce the fundamental components and internal structure of galaxies. We begin by outlining the theoretical basis for the study, describing the standard paradigm for structure formation and the details of the modelling techniques we employ. The extent of our current understanding of the processes responsible for morphological transformation is explored and we discuss what the structure of the Milky Way and its satellites can reveal about the wider pictures of galaxy formation and cosmology. Using data from two semi-analytical models, we investigate the origin of the disks and spheroids that represent the coarse-grain detail of galactic structure. Major galaxy mergers, which have long been regarded as the main mechanism by which elliptical galaxies and spiral bulges are generated, are found to play only a minor role in spheroid formation for all but the most massive systems. The models make similar predictions in many respects but disagree on the importance of gravitationally unstable disks in forming spheroids, serving to illustrate the uncertainty that remains in modelling morphology even at this basic level. We go on to introduce a smoothed particle hydrodynamics code which includes models for radiative gas heating and cooling, the structure of the interstellar medium, star formation and evolution, chemical enrichment and feedback from supernovae. We present a set of simulations that focus on a single Milky Way-mass galaxy and its local environment and summarise its bulk properties and formation history. We also show results from a code comparison project, which aims to quantify the effects of different physical mechanisms and modelling approaches on the formation of a galaxy disk. Our simulations also resolve the formation of a population of satellite galaxies which have a luminosity function similar to those found around the Milky Way. Through comparison with a dissipationless version of the same simulation, we determine that the baryonic component in each satellite has little effect on the structure of its dark matter halo. We also find a statistically significant discrepancy between the central mass densities of the simulated and observed satellites. Finally, we consider the formation of the haloes of hot gas and stars which surround the main galaxy disk. We find qualitative agreement with several observed properties of the Milky Way's stellar halo and with recent theoretical studies of the two components in the literature.

Major advances in the development of instruments for eight and ten meter class telescopes are revolutionising our understanding of galaxy formation. In particular, Integral Field Spectrographs (which produce a three dimensional (x, y, velocity) map of a galaxy) now permit studies of distant galaxies in nearly as much detail as local galaxies in our cosmic neighbourhood. These instruments can be employed to investigate specific problems in galaxy formation across 90% of the history of the Universe, and we demonstrate their capabilities by probing galaxy evolution from z=0.l to z=3. Locally, post-starburst (E+A) galaxies are thought to represent the transitional phase of galaxy evolution which links star-forming (late type) galaxies with their quiescent (early type) end products. We demonstrate that integral field spectroscopy can be employed to disentangle the stellar and dynamical structures of this post-star burst phase and therefore constrain the trigger (or triggers) of this phase of galaxy evolution. At higher redshift, (i.e., above z=l), "normal" galaxies are frequently too small and faint to observe via conventional observations. However, gravitational lensing by galaxy clusters provides us with a unique tool to study distant galaxies. By coupling the lensing phenomenon with Integral Field Spectroscopy, we investigate the evolution of the relation between the baryonic and non-baryonic components of galaxies from z=l to the present day through the Tully-Fisher Relation. By reconstructing the source morphologies and velocity fields of lensed galaxies, we find evidence for 0.5mag of brightening in the restframe B-band, but <0.lmag of evolution in the rest frame I-band, suggesting a clear preference for hierarchical growth of structure and increased star-formation activity at z=l. At these high redshifts, some galaxies (such as radio galaxies and SCUBA galaxies) are frequently bright enough and extended enough to study without the boost of a gravitational lens, and therefore can provide important comparison samples with which we can understand how high redshift proto-galaxies evolve into their present day descendants. By targeting the rest frame optical properties of SCUBA galaxies with traditional near-infrared longslit spectroscopy we find that the high redshift sub-mm population share many characteristics with the somewhat less luminous far-infrared galaxies identified in the local Universe. This includes the Ha equivalent widths, the proportion of obvious AGN and the typical spectral classification. Yet there remain important differences, with proportionally more highly-obscured activity in the high-redshift population, apparently larger dynamical mass, lower metallicities and much higher gas fractions on 10-kpc scales. With this sample of far-infrared luminous galaxies in hand, we use integral field spectroscopy to study the structural and dynamical properties of powerful high redshift SCUBA galaxies. We show the power of combining optical and near-infrared integral field spectroscopy to probe the power sources, masses and metallicities of powerful, distant galaxies, as well as understanding the role of AGN- and star-burst driven feedback processes in these high redshift systems.

This thesis investigates through situational and empirical analysis the beneficial and detrimental characteristics of the informal economy in Lebanon and its impact on the public and state interest through its socio-economic associations. The informal economy is a polymorphous entity, and in order to determine its versatile contribution, has been separated into four different variables or key drivers. The four key drivers constitute the determinant variables of the informal economy. The main method used to explore the four determinant variables is the Force Field analysis. The first key driver is informal remittances as they represent a significant fraction of the informal economic activity in Lebanon and make a major contribution to Gross Domestic Product. The second driver is corruption, as this involves massive economic transactions on a daily basis, with an enormous impact at both the microeconomic and macroeconomic levels. The third key driver is the informal employment and commerce sector, as the unpaid VAT and corporate and income tax evasion results in a huge annual loss of government revenue in Lebanon. The fourth and last key driver is the illegal networks, as Lebanon represents an international hub for smuggling, drug and people trafficking and money-laundering, with strong links with, and implication for, its sectarian constituents. The current situation in Lebanon fuels the creation of a chaotic socio-economic environment where it is impossible to estimate accurately the significance of the informal economy, or indeed the size of the overall economy. As far as possible in this research all the key drivers have been independently and collectively evaluated through the data collected from the primary sources (users/public opinion, government officials and academics) and secondary material in order to assess each key driver’s input to the informal economy. Subsequently the thesis provides an estimation of the beneficial and detrimental contribution of the informal economy in Lebanon, as well as the overall perceptions of each of the respondent groups. Lastly, the primary and secondary materials are collectively assessed from a single perspective to build, using an inductive approach, a theoretical model of the factors which fuel and perpetuate the informal economy in the country. The present thesis may constitute the foundation for future analysis of the informal economy in Lebanon by providing unconventional recommendations. It is an attempt to present the possibility of an alternative approach to the informal economy, by stressing its merits and advantages, while also recognising the dangers and challenges it poses for both the state and the society.

The instrumentation developments within this thesis are primarily aimed at instrumentation for the next generation of telescopes: Extremely large telescopes (ELTs). In the European astronomical community, the highest priority for ground-based optical and near-IR instrumentation has been identified as high-multiplex, multi-object spectroscopy (HMS) [1]. HMS includes both simultaneous observations of multiple faint objects at the limits of detection (Multiple Object Spectroscopy: MOS) and spatially-resolved spectroscopy over contiguous fields of brighter structured objects (Integral Field Spectroscopy: IFS) and a mixture of the two (Diverse Field Spectroscopy: DFS). However, before we can start to build instrumentation for ELTs it is important to: understand fibre characteristics more thoroughly and be able to predict behaviour with the use of a theoretical model (chapter 3); look at new technologies (Photonic Crystal Fibres, chapter 4, Volume Phase Holographic Gratings, chapter 5); use fibres in different ways (MAIFU, chapter 6).

This thesis investigates local cluster early-type galaxies, combining new spectroscopy with multi-wavelength imaging. We probe the stellar content of elliptical and lenticular galaxies, exploring the interconnection between age, chemical composition and dynamical substructure. We analyse the ultraviolet-infrared colour-magnitude relation, using new GALEX imaging of quiescent red-sequence galaxies in local clusters, and confirm that the intrinsic scatter is an order of magnitude larger than for the analogous optical relation. We compare the UV-IR colours to spectroscopic stellar populations parameters, and find a strong correlation with metallicity (albeit still with a large scatter), and only a marginal trend with age. We argue that the UV upturn is not significant in this sample, and demonstrate that the intrinsic scatter could be attributed to simple frosting by either a young or low metallicity subpopulation. We present a comprehensive study of the internal gradients in age, metallicity and a-element abundance for 25 cluster early-type galaxies, using data from the VLT VIMOS integral field unit. We find negative metallicity gradients, with a large intrinsic scatter for galaxies with σ ≥ 130 km s-(^1) which we speculate could be the lower limit for a formation history dominated by major mergers. Stellar population gradients are primarily related to the central metallicity: early-type galaxies with super-solar centres have steep negative metallicity gradients and positive age gradients; those with solar metallicity centres have negligible [Z/H] gradients and negative age gradients. B-R colour gradients predicted from the spectroscopic age and metallicity generally agree well with those measured directly from photometry. There is a strong observed anti-correlation between the gradients in age and metallicity. While a part of this trend can be attributed to correlated measurement errors, we demonstrate that there is an underlying intrinsic relation. We present new CMOS long-slit observations of seven edge-on lenticular galaxies in the Coma cluster, probing to several disc scale lengths in each. We strongly confirm that these S0s are significantly offset in luminosity from the spiral Tully-Fisher relation, and show that the size of this offset is correlated with projected local density. However, there appears to be no difference in the mean offset between S0 samples from various global environments (i.e. group and cluster). We derive the radial trends in the stellar populations, and find generally regular profiles consistent with those observed in the VIMOS sample. Significant deviations from the general radial trends coincide with structural and kinematic boundaries. We find that the age of the disc component is correlated with the offset from the Tully-Fisher relation, and agrees well with simple models of abrupt star formation truncation in a spiral disc. We show that SO discs tend to be older and more metal poor than the central regions, supporting the theory of bulge growth alongside disc quenching, during S0 formation

This thesis involves the study of strong and weak gravity phenomenology within the braneworld paradigm. We begin with a general overview of the hypothesised concept of extra spatial dimensions and explain why they are so interesting. Turning next to the topic of classical four-dimensional black holes, we discuss their formation via gravitational collapse and indicate some of the strong observational evidence of their existence. We then merge the two independent theories of extra dimensions and black holes together to form braneworld black holes. Focusing our attention on two distinct braneworld scenarios, we examine the effects produced from either strong or weak gravity. The prospect of obtaining experimental verification of the existence of additional spacelike dimensions in the upcoming ground-based accelerators, makes the theoretical research of braneworld gravity within this thesis even more enticing. We start with a non-perturbative approach to look for exact, spherically symmetric star or black hole solutions on a Randall-Sundrum brane from the perspective of the five-dimensional spacetime. By fixing the background, we explore the permissible braneworld trajectories within it that correspond to a braneworld observer, the solutions of the brane Tolmann-Oppenheimer-Volkoff equations. A variety of static gravitating matter sources on the brane are obtained in a range of different backgrounds. Our final aim is a consistent brane embedding in a Schwarzschild- Anti de Sitter spacetime as these solutions are potential candidates for brane stars or black holes. The weak and dominant energy conditions determine the physically sensible solutions which have the interpretation of braneworld stars. We then study time-dependent trajectories as a possible description of time-dependent braneworld black holes. This work is then generalised by relaxing the simplifying assumption of Z(_2)-symmetry, previously imposed around the brane. Non-Z(_2) symmetric spacetimes are applicable in processes which concern only one side of the brane, for example black hole recoil or the emission of Hawking radiation. We determine that a subset of the allowed brane trajectories in an asymmetric background are exactly the same as the Z(_2)-symmetric case. Next, we explore perturbative gravity in the Hofava-Witten model of heterotic M-theory. The study of scalar and gravitational fluctuations determines that the radion mode is coupled to the bulk scalar field, indicating only one single degree of freedom. Our analysis also determines the instability of a black string. We then compute the complete mass spectrum of the graviton mode. Using the five-dimensional gravitational physics, we determine what the gravitational interaction an observer on the braneworld would perceive. This analysis involves the computation of the Newtonian potential between two test masses on the visible brane, together with the four-dimensional tensor structure of the massless graviton propagator. Finally, as an application to the earlier work, we comment on work which is in progress: the study of possible brane black hole solutions in low energy heterotic M-theory.

Observations of starburst galaxies have revealed a large number of point-like X-ray sources located within these systems, including active galactic nuclei (AGN), X-ray binaries (XRBs), and utraluminous X-ray sources (ULXs). In this thesis we investigate the physical properties of a variety of these objects using both their X-ray emission characteristics and their optical counterparts, in order to better understand the accretion physics of such objects, and the environments in which they are found. This work begins with a study of 3 moderate-redshift (z ~ 0.1) X-ray bright (> 10^42 erg s^-1) galaxies, all of which display no clear signs of the presence of an AGN in the optical band. Given the high X-ray luminosities of these objects, they must either be the most X-ray luminous starburst galaxies known; or they must harbour a hidden AGN. We use new, pointed observations of the galaxies to determine their detailed X-ray characteristics, and demonstrate that each X-ray source is consistent with an AGN. The most likely explanation for the lack of AGN signatures in the optical spectra of these galaxies is that the AGN emission lines are being diluted by star formation signatures from within the host galaxies. Next, we present age constraints on 13 bright XRBs located within the high-metallicity drop-through ring galaxy NGC 922. While less than half the X-ray sources are located close to recent star formation as traced by Hα emission, the majority of sources are associated with star clusters, that we are able to age on the basis of their optical colours. We find that the sources that are closest to clusters tend to also have the youngest counterpart clusters and, in most cases, are close to H$\alpha$ emission, placing a limit of < 10 Myrs on their age, while those with greater distances to star clusters are also significantly older. We also investigate the possibility that the X-ray sources were ejected from their parent clusters, either by dynamical interactions, or by supernova kicks. An important caveat to the results of this work is that the a number of sources may have associated clusters that are highly extinguished and are therefore undetectable in the optical band. Finally, we present a study of the 8 brightest X-ray point-sources in the prototypical starburst galaxy M82, using the rich data set afforded to us by a ~ 480 ks Chandra observation of the galaxy. From our investigation, we find that the sources with X-ray luminosities < 10^39 erg s^-1 are heterogeneous, but all display X-ray properties that are typically observed in canonically accreting back hole binaries. A possible bi-modality is seen in accretion states between the more luminous and less luminous sources in this subset of our sample. The majority of these sources show significant long-term variability, with one of the sources being identified as a transient candidate. The three brightest sources in our sample, all of which are known ULXs, display long-term variability and spectral characteristics consistent with previous observations. This work demonstrates the rich potential for future studies of the diverse X-ray binary populations in nearby galaxies.

Neutron stars are very dense stars composed almost entirely of neutrons. As such, they should be able to be described by Quantum Chromodynamics (QCD). As QCD is a very complicated theory from which it is difficult to produce quantitative results we rely on effective theories to describe QCD physics. It has previously been shown that the Skyrme model, which has topological soliton solutions that can be identified as baryons, is such a low energy effective field theory for QCD. In this thesis, after presenting background material in chapters 1, 2 and 3, we explore the results of attempting to use the theory proposed by Skyrme to model neutron stars by investigating two models. The first, discussed in chapter 4 and based on original research, considers rational map ansatz solutions to the Skyrme model. By coupling the model using this ansatz to gravity and introducing a new way of stacking together the shell-like solutions that form we find minimum energy configurations that are stable models of neutron stars. They are, however, slightly too small to be considered a good model so a second approach is tried. The second model considers Skyrme crystal configurations. By using a relation between the energy per baryon of a Skyrme crystal and its anisotropic deformations we are able to find two equations of state for the crystal. These are combined with a Tolman-Oppenheimer-Volkoff equation, generalised to describe anisotropic deformations, to model neutron stars. We find that below a critical mass all deformations are isotropic and above it they are anisotropic up to a particular maximum mass and that this approach compares well with experimental observations. This second model is described in chapter 5 and is based on original research.

In this thesis I examine supernova feedback in hydrodynamical simulations of galaxy disks. Understanding this process entails the numerical evaluation of cooling in radiative shocks, and we present a set of simulations using two widely used numerical schemes: smoothed particle hydro- dynamics and adaptive mesh refinement. We obtain a similarity solution for a shock-tube problem in the presence of radiative cooling, and test how well the solution is reproduced. We interpret our findings in terms of a resolution criterion, and apply it to realistic simulations of cosmological accretion shocks onto galaxy halos, cold accretion and thermal feedback from supernovae or active galactic nuclei. To avoid numerical overcooling of accretion shocks onto halos that should develop a hot corona requires a particle or cell mass resolution of 10^6 M⊙, which is within reach of current state-of-the-art simulations. At this mass resolution, thermal feedback in the interstellar medium of a galaxy requires temperatures of supernova or AGN driven bubbles to be in excess of 10^7 K at densities of n_H = 1.0 cm−3, in order to avoid spurious suppression of the feedback by numerical overcooling. In order to improve sub-grid models of feedback we perform a series of numerical experiments to investigate how supernova explosions shape the interstellar medium in a disk galaxy and power a galactic wind. We model a simplified ISM, including gravity, hydrodynamics, radiative cooling above 10^4 K, and star formation that reproduces the Kennicutt-Schmidt relation. By simulating a small patch of the ISM in a tall box perpendicular to the disk, we obtain sub-parsec resolution allowing us to resolve individual supernova events. We run a large grid of simulations in which we vary gas surface density, gas fraction, and star formation rate in order to investigate the dependencies of the mass loading, β ≡ dot M_wind / dot M_star. In the cases with the most effective outflows we observe a β of 4, however in other cases we find β<<1. We find that outflows are more efficient in disks with lower surface densities or gas fractions. A simple model in which the warm clouds are the barriers that limit the expansion of the blast wave reproduces the scaling of outflow properties with disk parameters at high star formation rates. We extend the scaling relations derived from an ISM patch to infer an effective mass loading for a galaxy with an exponential disk, finding that the mass loading depends on circular velocity as β ∝ V −α with α ≈ 2.5 for a model which fits the Tully-Fisher relation. Such a scaling is often assumed in phenomenological models of galactic winds in order to reproduce the flat faint end slope of the mass function. Our normalisation is in approximate agreement with observed estimates of the mass loading for the Milky Way. Finally, we extend these simulations to follow the ejecta produced by these SNe, allowing us to track the distribution of metals as they are mixed into the different phases of the ISM and swept out into a galactic wind. Such calculations are important both directly in predicting the enrichment of the intergalactic medium, but also with the sister problem of understanding the enrichment of the host galaxies and the mass-metallicity relation, owing to the unique role that supernovae are believed to play both as the sources of galactic winds and the sources of galactic metals. We study the dependence of the amount of metals released per unit of star formation, β_Z ≡ dot M_z / dot M_star, and the fraction of metals released, β_Z / y. We include thermal and momentum feedback from massive stars and find these make a less significant contribution to the galactic wind than SNe. We build up a model of galactic chemical evolution and we demonstrate that these models are compatible with the metallicity distributions of faint stars and compare to closed box models of chemical evolution. We infer metal retention fractions from the observed data, although this may be complicated by recycling in the galaxy halos. We compare these rates to the fraction of metals ejected in the simulations and demonstrate approximate agreement, although the simulation data has considerable scatter, primarily due to the stochastic nature of the feedback in the limited volumes of the simulations.

An experiment designed to measure Cerenkov radiation from cosmic ray extensive air showers was deployed at Dugway, Utah from October 1977 to March 1980. This thesis is concerned with Cerenkov light measurements made at Dugway during the second season of observation from October 1978 to March 1979.An introduction to cosmic rays and extensive air showers is followed by a review of previous studies (both theoretical and experimental) of Cerenkov radiation from EAS. Particular attention is given to Cerenkov light parameters which relate to the depth of electron cascade maximum. A detailed account of the design and performance of the array of Cerenkov light detectors is then given, combined with an account of the first season of observation from October to December 1977.The calibration of the equipment during the second season of observation is discussed, indicating the sensitivity of the equipment to a light flux. This is followed by a description of the procedure employed to reduce the data from the experiment. A small sample of the recorded showers was selected to form the basis of a preliminary analysis presented in this thesis. Analysis of this sample of showers enabled the average characteristics of Cerenkov radiation from showers of energy 5x10(^16) - 5x10(^17)eV to be determined. The study of the average characteristics of Cerenkov radiation indicated that the lateral distribution of photon density, the peak height and FWHM of the Cerenkov pulses were sensitive to the zenith angle and energy of the showers. From the lateral distribution of photon density a primary energy estimator was established. Consistency was found between the preliminary results presented here and computer simulations. There were also favourable comparisons between the results of the Dugway experiment and similar measurements made at other establishments. A survey of vertically incident computer simulations of extensive air showers indicated that the basic assumptions behind the recently introduced elongation theorem may not be valid. Finally, a review of the future work of the Dugway experiment is presented.