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It was in 1864 that the first clues as to the nature of the space between stars were first identified in literature. These spaces became known as the interstellar medium. Any study of star formation must include an understanding of this interstellar medium (ISM) and its various component parts. Molecular clouds, dense regions of the ISM, are the sites where all known star formation is thought to occur. Hence, whenever an area containing young stars reside, it is assumed that one will also find a molecular cloud. Knowledge of these stellar birthplaces assist not only in models of stellar evolution, star formation potential, rate and efficiency - but also the ISM gives indications as to Galactic structure and the dynamics therein. Within this thesis I begin with an introduction and historical background of the field before detailing the research which was conducted. Firstly, I discuss a new model describing the spatial and kinematic structure of the Milky Way’s spiral potentials; the Perseus arm, the Outer arm and the outer Scutum-Centaurus arm and also the kinematics of the streaming motions of the gas within them. Material associated with each of these arms is then extracted. Using the models and spiral arm maps derived, I present spatially convolved maps of each spiral arm region (Perseus, Outer and Scutum-Centaurus) at a constant linear scale. By minimising the biases inherent with angular observations of our Galaxy, this presents the data as an analogue of - and as such directly comparable to - extragalactic observations of spiral structure. Finally I present a series of analyses performed on the data and models; derivation of large-scale properties of the spiral arms (i.e. identification of where the arm is unconfused with fore- and back-ground emission, scale height, velocity dispersions, arm mass); dynamical analyses of the models; molecular cloud decomposition of the constant-linear-scale-maps. The findings are then compared with those in the Galactic and extra-galactic literature.

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The stellar kinematics of the spheroids and disks of SO galaxies contain clues to their formation histories. Unfortunately, it is difficult to study these components using con- ventional absorption line spectroscopy - it is difficult to disentangle the two compo- nents and to recover the stellar kinematics in the faint outer parts of the galaxies. This thesis presents data on the stellar kinematics of 6 SO galaxies, in a range of environ- ments, derived from observations using the Planetary Nebula Spectrograph. These datasets allow the study of the kinematics of the faint outer parts of the galaxies, using planetary nebulae as tracers of the stellar populations. We have developed a new maximum-likelihood method that combines these data with a photometric spheroid-disk decomposition, in order to separate the kinematics of the two components. The method was tested on a simulated galaxy to ensure it correctly recovered the galaxy kinematics in the disk and the spheroid. This method is applied to NGC 1023 and the results are compared to a previous kine- matic analysis in the literature. We show that the unusual kinematics previously in- ferred for this galaxy were the result of not separating the disk and spheroid compo- nents. NGC 1023 is in fact found to exhibit spiral-like kinematics, once its components are properly decomposed. The maximum-likelihood clipping applied in the method also reveals a star stream associated with NGC 1023A, confirming the method's ro- bustness against such contaminants and its ability to uncover additional kinematic components. The method is then applied to the full sample of 6 SOs and we show that, with one exception, they have flat rotation curves, ordered motions dominate ran- dom motions in the disks, and the spheroid velocity dispersions remain approximately constant with radius. The derived kinematic parameters are studied and compared to those of spiral and el- liptical galaxies. The inferred circular speeds, after applying the asymmetric drift cor- rection, are in good agreement with those derived directly from gas kinematics, where such data are available. Although primarily rotationally supported, the disks are found to have systematically larger random motions than typical spiral galaxies, with this dif- ference most apparent in the SOs with the largest bulges. By investigating the Tully- Fisher and Faber-Jackson relations for the decomposed disks and spheroids respec- tively, we find that these SOs have systematically fainter disks and brighter spheroids than spiral galaxies and ellipticals in the literature. All these results are consistent with a scenario in which SO galaxies are formed from spirals through a moderately-violent mechanism, such as a series of very minor mergers.

The Unidentified Infrared (UIR) bands are a family of emission features seen in dusty objects, which are generally attributed to IR fluorescence of small (~ 50 C-atoms) polycyclic aromatic hydrocarbon (PAH) molecules. However, no specific PAH has so far been identified. The spatial distribution of 3.3 p,m PAH emission in the inner region of the Red Rectangle nebula is studied using an Integral Field spectroscopy technique. The presence of two components at 3.28 and 3.30 p,m with different spatial distributions, originally proposed by Song et al. (2003, 2007) is supported by these data. This implies the presence of two classes of 3.3 p,m band carrier with peak wavelength separation of ",0.02 p,m. From comparison of the 3.3 p,m observations with laboratory and theoretical spectra for a range of PAH molecules it is inferred that the 3.28 p,m and 3.30 p,m components arise from 'bay' and 'non-bay' hydrogen sites, respectively, on the periphery of neutral PAHs. The vibrational spectrum of a large number of PAH molecules are investigated with Density Functional Theory (DFT) calculations to find possible trends which may help in the identification of specific PAHs. It has been found that for acenes (single row), the position of the solo out-of-plane bending mode moves to shorter wavelength with increase number of carbon atoms. A similar behaviour holds also for 2-rows, 3-rows and large compact PAH molecules. Pericondensed and catacondensed PAHs with functional groups are investigated to assess their contribution to the unidentified 21 p,m feature, found in carbon-rich environments. They are unlikely to be responsible for the feature. The results of DFT calculations for large, solo-containing PAHs are then used to model Abstract 4 the asymmetric profile of the 11.2 p,m feature. The IR emission mechanism is taken into account, together with the effects of the DV radiation field in different sources; the temperature dependence of the solo out-of-plane bending mode and position are also considered, using state-of-the-art experimental data. It is found that the model reproduces very well the shape and the val1ations of the 11.2 p,m band in a few environments, supporting the idea that these variations are due to different mass distributions of PAHs, rather than anharmonicity. A similar model is then applied to acenes, which appear to contribute most of the intensity of the 11.0 p,m feature. High-resolution long-slit spectroscopic observations of the 11.2 p,m band in two PNe (NGC 7027 and BD+30° 3639) and in a PDR (The Orion Bar), in a search for fine stmcture have been carried out. While the presence of fine structure cannot ruled out, changes in the 11.2 p,m feature along the Orion Bar, from the molecular cloud to the ionised region, is seen suggesting possible evolution of the carriers of the feature. ..

This thesis describes work on inflationary cosmology, specifically in relation to observations. After reviewing the theory of inflation and dark matter, we introduce a model, 'S-infiation', in which a gauge singlet scalar S (with quartic self-coupling As) is both thermal relic dark matter and the inflaton. This is made possible by its non-minimal coupling es to gravity, where *. '" 4.6 X 104 at tree level. Reheating occurs primarily through a stochastic resonance to Higgs bosons, which then annihilate to relativistic particles. Primary importance is given to the predictions the model makes for the Higgs mass (mh), spectral index (n) and S mass (ms). Under reasonable assumptions, 130 GeV < tiu, < 170 GeV, 50 GeV < ms < 1 TeV and n > 0.966. All - of these are in principle within reach of the LHC, Planck and direct detection dark matter experiments, such as XENONlOO. We then show that the renormalization group improved effective potential is a superior method to the standard Coleman Weinberg potential for calculating inflation observables. Then, we compare the predictions of S-inflation to those of pure Higgs inflation and Higgs inflation with an additional scalar. For mh 2: 130 GeV, the models are in general distinguishable through the spectral index n, with n > ne! for S-inflation models and n < ne! for Higgs inflation. For N e-foldings of inflation, ne! ~ 1 - t; - 2~2 ~ 0.966. We next explain the origin of the apparent violation of unitarity at energy scales greater than A '" !:[;- (Mp is the reduced Planck mass). As we demonstrate, the calculation of the unitarity bound is done perturbatively, while the theory is non-perturbative at the energy of unitarity violation. Therefore, it is not possible to conclude whether or not unitarity is violated in the model. The model may instead be strongly coupled, meaning that the calculation of scattering amplitudes at E '" A becomes non-perturbative, while the analysis of inflation is unchanged. If unitarity is shown to be violated in the original model, a new, unitarity conserving version of the model can be considered. This has a simple form in the Einstein frame, and predicts a larger spectral index (n:::::: 0.975) than the original model.

This may be interpreted as evidence that the profile of sub-structure of the lambda 6614 DIB is skewed towards the red in these three sightlines (Sk -68°135, Sk -69°223 and Sk -69°243) to a greater degree than that found in the Galactic ISM. Compared to Galactic trends, the LMC DIBs are found to be weak with respect to the reddening and neutral potassium column density towards Sk -67°2 and Sk -68°135. This may be attributable to a combination of the high UV flux and reduced shielding of interstellar clouds due to the low metallicity of the interstellar gas of the LMC, and results in the destruction of DIB carriers by photodissociation and/or photoionisation. Relative to N(H I) the lambda 6284 DIB observed in four LMC sightlines is shown to be approximately 1/5 to 1/2 of its average strength in the Milky Way. This supports the idea that the metallicity and/or dust-to-gas ratio of the ISM is closely linked with the chemistry that governs the abundance of DIB carriers relative to N(H I). Variations in the N(Ca II)/N(Ti II) ratio are found over at least an order of magnitude in the LMC ISM, and are taken as evidence for significant variation in the Ca n/Ca m ionisation balance. Derived logarithmic titanium depletions are found to be relatively low in the six LMC sightlines studied, with values between approximately -0.8 and -1.9, which are similar to the levels of depletion generally seen in the warm, shocked interstellar medium of the Galaxy.

Planetary nebulae are formed from the ejecta of evolved stars. These ejecta are swept up by the fast low density wind from the hot central star, as it evolves towards a white dwarf. The sweep-up mechanism is called the Interacting Stellar Winds model (Kwok et al. 1978). The history of mass loss is imprinted on the nebular ejecta. The velocity field of the ejecta traces the mass loss event. A continuous mass loss gives a different velocity field from a brief mass loss event. We employed Integral Field Unit spectroscopy to study the velocity fields of three Bulge Planetary Nebulae. The preliminary results show the advantage of continuously sampled IFU spectroscopy over long slit spectroscopy. The kinematic of the nebula NGC 6302 was studied in the plane of the sky by com- parison of two epochs of Hubble Space Telescope images separated by 10 years. A two dimensional velocity field was created from 200 measurements. The nebular lobes are found to follow a Hubble-Flow, and were ejected in a brief event 2250 ± 35 yr ago. The ejection of lobes occurred about 700 yr after the end of AGB mass loss. The distribution of ages revealed that the inner nebula appears to be younger. This effect can be explained with additional acceleration at later stages of nebula evolution. The central star of NGC 6302 is believed to be extremely hot based on observed ionization stages in the spectrum. In this thesis the detection of the NGC 6302 central star is reported. The luminosity of the star was determined to be 4 010 L⊙. Together with age of the nebula age the mass of the star could be considerably narrowed down the mass determination of the star to 0.64 ± 0.01 M⊙.