The chemistry of galaxies provides a powerful probe of the underlying physics driving their evolution, complementing the traditional tools of morphology, kinematics,and colours. This dissertation examines several aspects of the galactic chemical evolution of late-type galaxies - both disc-like and dwarf - using a suite of cosmological hydrodynamical simulations, which incorporate the nucleosynthetic pollution of the interstellar medium, supplemented with classical analytical models of Local Group dwarfs. Throughout the work, these models are confronted with extant observations of both local and high-redshift systems, in order to identify both the strengths and weaknesses of the current generation of galaxy models. The work here has been presented across four primary science chapters which follow on from the Introduction and Motivation, prior to closing with the Conclusions and Future Directions. The first science result (Chapter 2) derives from an examination of the cold (neutral)gas content of the first-ever simulated bulgeless dwarf disc galaxies (Governato et al. 2010), and builds upon the work first presented in Pilkington et al. (2011). The focus of the work is on comparing the observables inferred from the simulated interstellar media, with those seen in nature (including The HI Nearby Galaxies Survey and the Magellanic Clouds), including their velocity dispersion profiles, disc flaring, and the distribution of power within the ISM’s structure, on different scales. Going beyond the work in Pilkington et al. (2011), two additional simulations from the Governato et al. (2010) suite are included, and the original work has been extended to include an analysis of the chemical properties of the dwarf galaxies. The second science result (Chapter 3) examines the role of feedback, metal diffusion, and initial mass function selection, on the resulting chemistry of a new grid of M33-like disc simulations. The emphasis of the analysis is upon the resulting age-metallicity relations and metallicity distribution functions (in particular, the extreme metal-poor tail). Aspects of the work have been presented by Pilkington et al. (2012b), enhanced here by a further examination of the satellites associated with their respective host galaxies. The satellites are seen to be free of gas, with star formation histories which make them not unlike Local Group dwarf spheroidals. The third science result (Chapter 4) is based upon an analysis of the temporal evolution of metallicity gradients in Milky Way-like systems, and derives from the work presented in Pilkington et al. (2012d). A large suite of simulations, sampling a range of numerical codes (particle- and grid-based, in addition to classical Galactic Chemical Evolution (GCE) models), each with different treatments of star formation, energy feedback, and assembly histories, was employed. The analysis focussed on both the radial and vertical abundance gradients, emphasising the role of feedback in shaping the gradients, and demonstrates the critical role that new observations of in situ gradients at high-redshift can play in constraining the uncertain nature of feedback within simulations. This work has been complemented by a brief examination of the azimuthal abundance variations in the massive discs. The fourth science result (Chapter 5) expands upon our earlier exploration of the chemical properties of simulated dwarf galaxies, but now employs a classical semi-numerical GCE approach. By coupling colour-magnitude diagram-constrained star formation histories with our GEtool GCE code, we attempt to constrain the relative rates of gas infall and outflow, for the Carina, Fornax, and Sculptor Local Group dwarfs, in order to match their empirical chemical abundance patterns and metallicity distribution functions. This builds upon the preliminary work, as presented by Pilkington & Gibson (2012a).

The Earth's crust is deforming continuously due to plate tectonics. Deformation at plate boundaries causes volcanoes and most destructive earthquakes. Monitoring such deformation is essential to gaining an insight into the mechanisms of plate tectonics. Deformation analysis is one of the most important aspects of geodetic research. Space geodesy, with which long baselines can be measured to millimetre accuracy, plays an important role in determining crustal deformation parameters, since deformation in general, means a change in geometric configuration. The main deformation monitoring problem is to determine the spatial relationship of a set of object points relative to a number of reference points. Ideally reference and object point observations are made at regular intervals. After mathematical adjustment of each epoch's observations, which includes 'data snooping', a displacement vector is obtained by simply differencing the estimated coordinates at consecutive epochs. The use of thismethod also however, increases the noise level. In this thesis, the author proposes a deformation analysis technique which mainly uses a Kalman Filter. However, Kalman filter estimation may not be optimal if local movement occurs between observation epochs. To overcome this kind of deficiency, two sub-optimal filters have been proposed: Fading Memory Filter and Adaptive Kalman Filter for a System with Unknown Measurement Bias. These two filtering techniques have been used in this research and tested on real/simulated data based on the EASTMED project. In addition to this, data from the EUREF Permanent GPS Network, and from the UK Tide Gauge Monitoring C Project are also processed and the result presented.

We address the issue of kinematic heating in disc galaxies by analysing a suite of cosmological Milky Way-type disc simulations run with different particle-and grid-based hydrodynamical codes and different resolution, and compare them with observations of the Milky Way. By studying the kinematics of disc stars in these simulations, we seek to determine whether or not the existence of a fragile thin disc is possible within a cosmological framework, where multiple mergers and interactions are the essence of galaxy formation. We study the velocity dispersion-age relation for disc stars at $z=0$ and find that four of the simulations, the stellar disc appears to undergo continual/secular heating. Two other simulations suggest a “saturation” in the heating profile for young stars in the disc. None of the simulations have thin discs as old as that of the Milky Way. We also analyse the kinematics of disc stars at the time of their birth, and find that in some simulations old stars are born cold within the disc and are subsequently heated, while other simulations possess old stellar populations, which are born relatively hot. The models which are in better agreement with observations of the Milky Way's stellar disc undergo significantly lower minor-merger/assembly activity after the last major merger. By running a set of isolated Milky Way-type simulations with different resolution and different density thresholds for star formation we conclude that, on top of the effects of mergers, there exists a ``floor'' in the dispersion that is related to the underlying treatment of the heating and cooling of the interstellar medium, and the low density threshold which such codes use for star formation. A persistent issue in simulations of disc galaxies is the formation of large spheroidal components, and disc galaxies with larger bulge to disc ratios than is observed. This problem is alleviated by supernova feedback. We found that by increasing the feedback in the simulations, we decrease the amount of stars that are accreted onto the main galaxy. The star formation is quenched more efficiently in low mass satellites when stronger feedback is implemented as well as in the main halo. These effects result in a disc galaxy, which has formed less stars overall, but more importantly, contains less accreted stars. As the strong stellar feedback quenches the star formation in the small building blocks, the metallicity of the accreted stars is lower than in the case where less feedback was used. In the context of hierarchical formation, mass assembly is expected to be scale free. Yet the properties of galaxies depend strongly on their mass. We examine how baryonic physics has different effects at different mass scales by analysing three cosmological simulations using the same initial conditions that are scaled to three different masses. Despite their identical dark matter merger history, we show that the simulated galaxies have significantly different stellar accretion histories. As we go down in mass, the lowest mass progenitors are unable to form stars, resulting in a low mass galaxy with less accreted stars. The overall chemical properties are also distinct at the different mass scales, as one might expect from the mass-metallicity relation of observed galaxies. We examine gradients of chemical abundances with radius and with height above the disc, and look for properties that are retained at different mass scales and properties which change, often dramatically. We analyse the kinematic and chemical properties of their accreted and in-situ populations. Again, trends can be found that persist at all mass scales, providing signatures of hierarchical structure formation. We find that accreted populations in the high mass simulation did not resemble any of the populations in the lower mass galaxies, showing that the chemical properties of proto-galaxies, which merge at high redshift to form massive galaxies, differ from the properties of low mass galaxies that survive at z=0. We probe further the signatures of hierarchical structure formation at smaller scales, in dwarf galaxies. We analysed the morphologies, kinematics and chemical properties of two simulated dwarf galaxies with different merger histories. We again analyse the accreted and in-situ populations. Observations of dwarf galaxies have found that they are comprised of multiple components. Our simulated dwarfs indicate that such populations may indeed be a manifestation of the hierarchical formation process in action in these lower mass galaxies. In one simulated dwarf, the in-situ stellar component forms a thin disc and a thick disc. We show that the thick disc in this simulation forms from in-situ stars that are born kinematically hot in the disc from early gas-rich mergers. The thin disc is formed quiescently from the later infall of gas. The accreted stars in the simulation were found to form an extended stellar halo. Chemical signatures of the three populations are also explored. The second dwarf we analysed has different galactic components, a result found to be due to the different merger history of this galaxy. The last major merger in this simulation occurs early on in the formation process between two proto-galaxies of similar mass. The result is a dwarf galaxy comprised of a disc formed of in-situ stars and a flattened rotating stellar halo formed of accreted stars. The angular momentum of the accreted and old in-insitu stars is obtained from the last major merger. We discuss the resemblance of this flattened rotating stellar halo to fast rotating flattened elliptical galaxies, and propose that such structures may explain some of the observed extra-galactic thick discs. These studies show that galactic properties emerge through the complex inter-play between hierarchical structure formation, star formation, and feedback from supernovae. Different modelling of these processes will alter the simulated galaxy's properties, and detailed comparisons with observations can then be made to determine the dominant processes responsible for different galactic properties. We remain optimistic that further improvement in modelling will allow deeper insights into the processes of galaxy formation and evolution.

We present an investigation into the environments of quasars with respect to galaxy clus- ters, and environment evolution with redshift and luminosity. The positions of quasars with respect to clusters have been studied using cluster and quasar catalogues available, covering the redshift range 0.2 < z < 1.2. The 2D projected separations and the 3D separations have been found and the orientation of the quasar with respect to the major axis of the closest cluster calculated, introducing new information to previous work. The positions of quasars with respect to clusters of galaxies will give an indication of the large scale environment of quasars and potentially clues as to which formation mechanisms are likely to dominate at various redshifts. For example, galaxy mergers are most likely to occur in galaxy group environments and will create luminous quasars. Galaxy harassment is more likely to occur on the outskirts of galaxy clusters and create lower luminosity AGN. Secular processes such as bar instability can also create AGN and are likely to be the cause of nuclear activity in isolated galaxies. The aim of this work is to study the large scale environment over a large redshift range and study the evolution as well as any change in environment with quasar luminosity and redshift. Another aim of this work is to study the orientation of a quasar with respect to a galaxy cluster. If galaxy clusters lie orientated along filaments, the position of a quasar with respect to a cluster will give an indication as to where quasars lie with respect to the filament and therefore the large scale structure. There is a deficit of quasars lying close to cluster centres for 0.4 < z < 0.8, indicating a preference for less dense environments, in agreement with previous work. Studying the separations as a function of cluster richness, there was a change in quasars lying closer to poorer clusters for z < 0.2 (Lietzen et al. 2009) to lying closer to richer clusters for 0.2 < z < 0.4, though more clusters at low redshifts will be needed to confirm this. There is no obvious relation between the orientation angle between a quasar and the major axis of the closest galaxy cluster and 2D projected separations. Using faint (Mr > −23.0 mag) and bright (Mr < −23.0 mag) quasars, there is no difference between the two magnitude samples for the 2D separations or the cluster richness, in contrast to Strand et al. (2008) who found brighter quasars lying in denser environments than dimmer quasars. These is no change with redshift (over 0 < z < 1.2) in the positions of the quasars with respect to the cluster or the cluster richness as a function of absolute quasar magnitude. There is also no preferred orientation between the quasar and the cluster major axis for bright or faint quasars. Spectra of a selection of 680 star forming galaxies, red galaxies, and AGN were taken by Luis Campusano and Ilona S¨ochting and 515 redshifts calculated. Though few of these galaxies turned out to be cluster members as was originally intended, it was possible to use these galaxies to study the environments of quasars with respect to star-forming galaxies and galaxy clusters. The objects were classified (33 classed as AGN), and star formation rates calculated and compared. Three AGN and 10 star forming galaxies lie at the same redshift (z = 0.29) as three galaxy clusters. The three galaxy clusters have the same orientation angle and may be part of a filament along with the star forming galaxies and AGN. Further study will investigate the relation between AGN positions and filaments of structure. A sample of quasar spectra taken by Lutz Haberzettl using Hectospec on the MMT were taken to increase the number of quasars used in this study. However, when studying the spectra, a number of high redshift quasars showed evidence of ultra-strong UV Feii emission in their spectra. The redshifts of these quasars were too high to be included in the main body of the study. However, a significantly large number of ultra-strong UV Feii emitting quasars have been found in the direction of three LQGs in the redshift range 1.1 < z < 1.6, including the Clowes-Campusano Large Quasar Group (CCLQG). Ly� fluorescence can increase the UV Feii emission. However, Ly� emission from other quasars was found to be negligible compared to emission from the quasar’s central source. Though there has been no previous indication that the LQG environment is unique, the high level of iron emission may indicate a difference in environment. Plans for future work based on these results are outlined.

The chemistry of large carbon-containing molecules in space is widely researched with notable advances including understanding of the aromatic infrared emission features in terms of their general origin in polycyclic aromatic hydrocarbon (PAH) molecules, identification of the fullerenes C60 and C70 as the largest molecules detected in the interstellar medium, and knowledge of the structure and composition of various solid-state interstellar grains. However, there remain major challenges. The work described in this Thesis addresses some longstanding, unanswered questions in astrochemistry, such as the origin of variation in the profiles of the aromatic infrared bands, the route to formation of C60, and the role of astrophysical grains in the reactions of carbon-containing species. This research was carried out using a range of laboratory and computational techniques, in combination with astronomical data, yielding new results that can be compared with existing work to find solutions to these problems. The varying profile of the 11.2 μm aromatic infrared emission band within two objects, NGC 7023 and the Red Rectangle, is investigated. The feature’s changing spectral shape, which depends on the position within the object, is interpreted in terms of variation in the distribution of molecular masses of the PAHs that give rise to the feature. This was achieved using a model that fits astronomical data which was obtained with the instrument MICHELLE on the UKIRT telescope in Hawaii and the Spitzer satellite observatory. Based on the calculated emission features of four neutral PAHs that are taken to represent ‘low-mass’ (fewer than 50 C atoms) or ‘high-mass’ (more than 50 C atoms), it is found that, with increasing distance from the star, there is an increase in the proportion of low-mass PAHs in NGC 7023, in good agreement with less specific previous studies that have been carried out using other approaches. The modelling results for the Red Rectangle indicate that the mass distribution does not change significantly with offset, although evidence from other sources appears in part to contradict this conclusion. A laboratory investigation is detailed in which formation of C60 from PAH precursors is explored. Transmission electron microscopy (TEM) and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) are used to irradiate, using the electron beam (e-beam) in TEM and the UV laser in MALDI-TOF MS, samples of PAH molecules and to monitor the products of any resulting transformations within the samples. It is found that under both e-beam and UV irradiation, PAH molecules lose one or more H atoms and form larger PAH 'oligomers’. Based on the MALDI-TOF MS results, specific chemical structures of these oligomers are proposed, and it is found that the precursor molecules coronene and perylene give rise to formation of C60. A mechanism is given for this process, in which an oligomer containing 60 carbon atoms or more is formed, and then ‘shrinks’ via loss of H atoms, C-C bond formation, and Stone-Wales rearrangements. Important structural features required for these mechanisms, namely the presence of ‘bay’ and 'fjord’ carbon edge sites, are discussed in an astrophysical context. An experimental methodology was designed and implemented to use TEM and MALDI-TOF MS in conjunction with each other, in which a specific area of a PAH sample is viewed using low-dose TEM, is then irradiated using the UV laser in MALDI-TOF MS, and finally is viewed a second time using TEM to observe the effects of the UV irradiation. Experiments were carried out to investigate reactions of acetylene and CO in the presence of astrophysically relevant grains. It was found that CO undergoes a disproportionation reaction over olivine grains, forming gaseous CO2 and depositing solid-state carbon on the grain surface; this has implications for the formation of other carbonaceous species such as PAHs and even carbon nanotubes. The formation of PAHs from acetylene gas over grains of SiC is reported, in addition to the inhibiting impact of CO when mixed with acetylene. In one experiment olivine samples were irradiated by the e-beam in TEM, and decomposition of the olivine structure was seen to occur, resulting in the formation of metallic nanoparticles. This behaviour is discussed in terms of its likely occurrence in astrophysical environments such as the Red Rectangle, and its potential for catalysis that results from reactions of molecules on the metal nanoparticle surface.

The thesis focuses on the asteroseismology of main sequence B-type stars, particularly β Cephei and Be stars. Photometric observations of these stars were analysed in order to detect stellar oscillations. The photometric data analysed in this thesis were collected using the Solar Mass Ejection Imager (SMEI). The analysis initially focussed on known β Cephei stars, to refine information on previously detected frequencies and detect further oscillations. A survey was then conducted using data from the SMEI instrument to search for further β Cephei stars. The results from this survey were analysed, and individual stars were examined in more detail which may possibly be β Cephei like. Due to the long duration of light curves obtained with the SMEI instrument, stellar oscillations can be analysed for evidence of amplitude and phase change. This type of analysis was completed on two Be stars, Achernar and \(\zeta\) Oph, and significant amplitude changes in the oscillations of both of these stars were detected. There is evidence that the amplitude variations may be linked with the outburst events that occur on Be stars, and therefore this analysis may be used to help solve the puzzle of the Be phenomenon.

The time delay estimation between time series is a real-world problem in gravitational lensing, an area of astrophysics. Lensing is the most direct method of measuring the distribution of matter, which is often dark, and the accurate measurement of time delays set the scale to measure distances over cosmological scales. For our purposes, this means that we have to estimate a time delay between two or more noisy and irregularly sampled time series. Estimations have been made using statistical methods in the astrophysics literature, such as interpolation, dispersion analysis, discrete correlation function, Gaussian processes and Bayesian method, among others. Instead, this thesis proposes a kernel-based approach to estimating the time delay, which is inspired by kernel methods in the context of statistical and machine learning. Moreover, our methodology is evolved to perform model selection, regularisation and time delay estimation globally and simultaneously. Experimental results show that this approach is one of the most accurate methods for gaps (missing data) and distinct noise levels. Results on artificial and real data are shown.

The sensitivity of the next generation of interferometric gravitational wave detectors will be limited in part by thermal noises of the optics. It has been proposed that using higher-order Laguerre-Gauss (LG) beams in the interferometers can reduce this noise. This thesis documents progress made in assessing the compatibility of higher-order LG beam technology with the existing precision interferometry framework used in the gravitational wave detector community. A numerical investigation was made into techniques for generating higher-order LG modes with a phase modulating surface. The optimal conditions for mode conversion were determined using fast Fourier transform (FFT) simulations, and predictions were made for the mode purity achievable with this method. Table-top experiments performed at Birmingham demonstrated the generation of higher-order LG modes using a spatial light modulator, and showed for the first time the feedback control of an optical cavity on resonance for higher-order LG modes. An increase in the purity of LG\(_{33}\) modes from 51% to over 99% upon transmission through the cavity was shown. Investigations were carried out at the Glasgow 10m prototype detector into the performance of the LG\(_{33}\) mode in a suspended 10m cavity, providing useful insights into the compatibility of LG modes with larger scale interferometers.

Massive stars have very strong stellar winds which interact with their environment. This work has involved the study of these interactive winds at radio and other wavelengths. Radio observations have been made of the massive runaway star BD+43◦ 3654 and its bow shock which is interacting with the inter-stellar medium. These observations, together with archive data at other wavelengths, have revealed stratified dust and turbulent gas in this interaction zone. Further radio studies have been undertaken of the interaction zones of the colliding winds of massive binary systems. Observations of the colliding wind binary WR 147 at 5GHz have revealed a curved collision zone, suggestive of simple interactive models. Measurements of the flux from the Wolf-Rayet component of this massive binary system has allowed a mass-loss rate to be derived and though the companion O-star is not detected, an upper flux limit has allowed upper limits on the mass-loss rate and limits on the terminal velocity to be inferred. Also revealed is a curious ’bridge’ feature previously observed in WR 147 which occurs between the two binary components. One mechanism is suggested to explain this anomalous feature, the ionising flux of one binary component, the O-star, may be ionising the wind of the other, the WR component. Modelling of the ionisation structure of the stellar winds has been undertaken to verify that this may be occurring. Radio observations of massive stars made at low-frequency have produced detections of WR 147 and the brighter colliding wind binary, WR 146. These detections have allowed modelling of the non-thermal emission in order to deduce where the non-thermal absorption turn-over occurs in these systems. The resultant modelling has illustrated that these colliding wind regions are complex, with multiple absorption regions best describing their nature.

The detection of galaxy groups and clusters is of great importance in the field of astrophysics. In particular astrophysicists are interested in the evolution and formation of these systems, as well as the interactions that occur within galaxy groups and clusters. In this thesis, we developed a probabilistic model capable of detecting galaxy groups and clusters based on the Hough transform. We called this approach probabilistic Hough transform based on adaptive local kernel (PHTALK). PHTALK was tested on a 3D realistic galaxy and mass assembly (GAMA) mock data catalogue (at close redshift z < 0:1) (mock data: contains information related to galaxies' position, redshift and other properties). We compared the performance of our PHTALK method with the performance of two versions of the standard friends-of-friends (FoF) method. As a performance measures, we used the precision versus recall curve. Furthermore, to test the efficiency of recovering the galaxy groups' and clusters' properties, we also used completeness and reliability, fragmentation and merging, velocity and mass estimation of the detected groups. The new PHTALK method outperformed the FoF methods in terms of reducing the detection of spurious agglomerations (false positives (FPs)). This smaller sensitivity to the false positive (FP) is mainly due to the clear description of the galaxy groups' model based on astrophysical prior knowledge; in particular, the fingers of god (FoG) pattern (a pattern formed by the projected velocity dispersion of galaxies, inside a galaxy group, along the line of sight). However, the FoF methods seem to outperform the PHTALK in terms of detecting galaxy groups or clusters that do not follow the FoG pattern. The main advantage of our probabilistic model is its flexibility to incorporate any prior knowledge expressed in terms of a galaxy group model.