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Studying the emission of Active Galactic Nuclei (AGN), particularly in the X-ray band can offer considerable insights into the accretion process. This is important as AGN activity has a strong effect on the evolution of their host galaxies. This thesis reports studies of a large sample of type 1 AGN, created by cross-correlating the optical SDSS DR5 quasar catalogue and the catalogue of serendipitous X-ray source detections, 2XMMi. A sample of 761 sources with X-ray spectra of sufficient quality for spectral modelling was obtained. The typical spectral shape of the sources is a power law of ‹Γ› = 1.99 ± 0.01 with an intrinsic dispersion of σ‹Γ› = 0.30 ± 0.01. However, ~ 3% were found to have intrinsically flat or steep Γ slopes. Significant trends between Γ and LX and Γ and Eddington ratio were found. The radio loudness of the sources was also determined and the RLQ show higher LX values and flatter Γ values than RQQ, suggesting an additional X-ray component is present. Intrinsic cold absorption was found in ~ 4% of sources with NH ~ 1021 − 1023 cm−2, despite being unexpected in optically classified type 1 AGN. A soft excess was found in ~ 8% of sources with an average blackbody temperature of ‹kT› = 0.17 ± 0.09 keV. This temperature correlates with LX and a strong correlation is found between the luminosities in the blackbody and power-law components. The detectability of these additional components is limited by the quality of the spectra. By simulating spectra with typical spectral shapes, the intrinsic percentage of the sample with a soft excess was found to be 75 ± 23%. The sample is also cross-correlated with archival multiwavelength catalogues and spectral energy distributions are created for each object. The infrared to ultraviolet region is found to be similar between sources regardless of their radio loudness, and the SEDs of low luminosity, low accretion rate sources tend to be flatter, with the optical/UV disc emission becoming more prominent with increases in these parameters.

We combine UV-optical photometry of early-type galaxies with galaxy formation models in the standard LCDM framework, to study their evolution over the last eight billion years. We demonstrate that LCDM comfortably reproduces the optical properties of early-type galaxies and, contrary to traditional beliefs, such optical characteristics are not conclusive proof that early-types form 'monolithily' in a short efficient burst at high redshift followed by passive ageing.

Dwarf galaxies are key objects in many cosmological theories, being the most numerous galaxy type in the local universe, the simplest stellar systems that appear to be dominated by dark matter and possible local analogues to the earliest galaxies formed. Due to their intrinsic faintness, however, detailed studies of dwarfs outside of our Local Group are currently limited. This work presents new K-band images of eight dwarf elliptical galaxies in the Fomax Cluster. Morphological and photometric parameters are acquired from the images by surface brightness profile fitting and galaxy modelling techniques. This new infrared data is combined with available optical data to obtain average colours, colour profiles and colour maps of the galaxies.

In part I. I construct a sample of radio-loud active galactic nuclei (AGN) host galaxies from the optical Sloan Digital Sky Survey (SDSS) and Faint Images of the Radio Sky at Twenty cm (FIRST). These have 1.4GHz luminosities in the range 1023 - 1025 WHZ-l, span redshifts 0.02 < z < 0.18, are brighter than rpetro < 17.77 mag and are constrained to 'early-type' morphology in colour space (u• - r• > 2.22 mag). Optical emission-line ratios (at > 311) are used to remove type 1 AGN and star-forming galaxies from the radio sample using BPT diagnostics. For comparison, a sample of radio-quiet galaxies with the same r• -band magnitude-redshift distribution as the radio sample is selected. I also create comparison radio and control samples derived by adding the NRAO VLA Sky Survey (NVSS), to quantify the effect of completeness on the results. I investigate the effective radii of the surface brightness profiles in the SDSS r and u bands in order to quantify any excess of blue colour in the inner region of radio galaxies. A ratio is defined, R = r e( r) Ir e( u), and maximum likelihood analysis is used to compare the average value of R and its intrinsic dispersion between samples. R is larger for the radio-loud AGN sample as compared to its control counterpart, and I conclude that the two samples are not drawn from the same population at > 99% significance. I discuss host galaxy features that cause the presence of a radio-loud AGN to increase the scale size of a galaxy in red relative to blue light, including excess central blue emission driven by star formation, point-like blue emission from the AGN itself, and/or diffuse red emission. I favour an explanation that arises from the stellar rather than the AGN light. Given that iii star formation proceeds over a longer time than radio activity, the difference suggests that a subset of galaxies has a structured predisposition to become radio loud. In Part 2, I report results from Chandra and XMM-Newton observations of seven nearby (z < 0.07) radio galaxies. Each source shows evidence of an X-ray emitting gas belt, 011hogonal to and lying between the radio lobes, coincident with a deficit in radio emission. Detection of weak emission from a second, more ex tended group-type environment is also reported, as well as inverse-Compton X-ray emissions from the radio lobes in six of the sources. The X-ray emission from the nuclei correlates well with the core 5 GHz flux densities, supporting an emission origin at the base of the jet. Three high-ionization narrow-line radio galaxies in the sample show evidence for an additional absorbed component, consistent with the model in which they are fuelled by a standard thin accretion disk, heavily absorbed in X-rays when edge-on to the observer. The work extends previous detection of lobe inverse-Compton X-ray emission into the FRI regime, and the magnetic-field estimates shows that these systems are close to equipartition, or slightly electron dominated, as is found for FR II sources in other studies. The origin of the gas belts is diverse. The work concludes that two of the belts (those of NGC 7385 and NGC 6109) are galactic coronae, flattened by the expanding radio lobes. The belts of3C 192 and 4C73.08 are attributed to accumulated gas from merging groups of galaxies residing within the gas belt. For 3C 386, the belt is consistent with a hot gas halo surrounding an isolated field elliptical In the case of 3C 35 and 3C 98, the gas belt is interpreted as fossil -group gas driven outwards by the expanding radio lobes. The morphological structure of the radio lobes and gas belt point to co-evolution. Furthermore, the radio sources are powerful enough to eject galaxy-scale gas out to the edges of the gas belts, and the ages of the belts and radio structures are comparable in both sources. The destruction of 3C 35 and 3C 98's atmospheres may offer clues as to how fossil systems are regulated: radio galaxies may need to be within a particular range of intermediate powers to displace and regulate fossil-group gas. I discuss the implications of the gas belts in 3C 35 and 3C 98 in terms of AGN fuelling and feedback.

The body of this thesis looks at two large observational programmes: The VLT-FLAMES Survey of Massive Stars (VFSMS) and The VLT-FLAMES Tarantula Survey. The VFSMS aimed to advance the current understanding of massive star evolution by pressing the issue of rotational mixing for a sample of over 700 early type stars in the Galaxy and Magellanic Clouds. The YFTS is an extension of the VFSMS to study, in detail , the comparison of binary and single massive stars. A detailed investigation into several different massive star populations is given, from both the VFSMS and the VFTS. The work of the VFSMS is focused on a sample of 64 Be-type stars within the Magellanic Clouds . Atmospheric parameters and photospheric abundances have been used to show the Be-type star sample is inconsistent with stars rotating close to critical velocity. The VFTS investigates the number of B-type binary systems within the 30 Doradus region of the LMC, by using a cross correlations analysis technique. A binary fraction of 29% is determined from over 500 B-type stars, further refined to a true binary fraction of 66% by modelling the sample incompleteness. From the binary search, investigations are presented into three high radial velocity variable stellar objects. Firstly a study highlights the B[e] phenomenon through the analysis of the supergiant B[e ]-like binary, VFTS698. Secondly a detailed analysis of two Tare blue supergiant binary systems, VFTS450 and VFTS652 is undertaken. Finally consideration is given to the remaining B-type star samples of the VFTS that require further investigation, viz. the projected rotational velocity distribution of binaries, and the potential short-period binary systems.

Until recently, the advantages of using mid- to far-infrared (MFIR) observations to investigate the thermal dust emission from active galaxies (AGN) had not been fully exploited. Therefore, this thesis presents the results from deep MFIR imaging observations (Spitzer/MIPS) of complete samples of 2Jy and 3CRR radio galaxies (0.03< z <0.7), as well as the results of two complementary radio imaging program (ATCA, VLA) for the 2Jy sample at high radio frequencies. The Spitzer data have been used to investigate the origin of the thermal MFIR emission, focussing on the correlations between 24, 70ILm and [O111j..\5007 luminosities. Because [0111j..\5007 emission line luminosity acts as a proxy for intrinsic AGN power, the tight correlations found between MFIR and [0111j..\5007 luminosities provide strong evidence that direct AGN illumination is the primary heating mechanism for the dust producing both the mid-IR and far-IR continuum. Using optical spectroscopic information about the level of recent star formation activity in the host galaxies, I deduce that starbursts significantly boost the far-IR emission in only a minority ofradio-Ioud AGN (17-35%). This result is supported by analysis of polycyclic aromatic hydrocarbon star formation tracers in objects observed with Spitzer/IRS as well as the analysis of MFIR colours. Given the lack of optical and infrared evidence for starburst activity, it is unlikely that the majority of powerful radio-loud AGN are triggered at the peaks of major, gas rich mergers. In addition, at high [0111] luminosities, the similarities between the MFIR properties (luminosities and colours) of broad-line radio galaxies (BLRG), quasars and narrow line radio galaxies support orientation-based unified schemes for powerful radio sources. However there remain groups of objects at low redshifts/luminosities, (e.g. weak line radio galaxies and low redshift 3C BLRG) whose characteristics at MFIR wavelengths are not readily explained in the simplest versions of such schemes. Overall, the results presented here underline the merits of observing complete samples of AGN atMFIR wavelengths. Much of the work presented in this thesis forms the basis of 3 publications (Tadhunter et al., 2007, Dicken et al., 2008, 2009). This work is based [in part] on observations made with the following facilities. Spitzer Space Telescope: operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. ATCA: operated by the Australia Telescope National Facility, a division of CSIRO. the VLA: operated by The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. as well as on observations made with ESO Telescopes at the Paranal Observatory. This research has also made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. I also acknowledge finacial support from the STFC.

Rhodococcus has been used in bioremediation because of its low eco- toxicity, high tolerance to harsh environments, and ability to be cultivated in mixed microbial consortia with certain contaminants as its nutrients. Excretion of extracellular polymeric substances (EPS) allows Rhodococcus to trap and to effectively degrade contaminants. Mycolic acid (MA) which covers the cell wall provides Rhodococcus with a hydrophobic cell surface to contact hydrocarbon contaminant droplets. This work concerns the influence of the conformational change in MA and rhodococcal EPS on their mechanical properties. Neutron reflection revealed that when the solution pH increases, a hydration layer is generated between the bound (hydrophobic) MA (LB _MA) and the silicon substrate, whereas the intermolecular repulsion unfolds the extractable (hydrophilic) MA (LS_MA), and allows water to fill in the formerly folded space. Force spectroscopy using a polystyrene colloidal probe showed that the strength of the adhesion force between a hydrophobic particle and MA is affected by the conformation of MA. The existence of a hydration layer in the MA enhances cell adhesion. Classical DLVO theory indicated that the electrostatic force dominates the long range (a distance larger than the Debye length) interactions between a polystyrene (hydrophobic) particle and MA, whereas the van der Waals force has a negligible influence. EPS generated at the early exponential phase (E EPS) and the late stationary phase (S EPS) of Rhodococcus manifested different physiochemical and mechanical properties. Force spectroscopy using Rhodococcus as a bacterial cell probe suggested that S EPS possess a higher differential capacitance than E EPS do for cells to store charges and energy. The nonspecific binding sites to silicon (an abundant material in the sediments of groundwater) are not evenly distributed; they exist mainly in S EPS close to the cell surface, but rarely in E EPS. Therefore, S EPS have a stronger adhesion to the silicon surface than E EPS do. Contraction and stretch of the EPS chains affect the strength of the adhesion force to a silicon surface. S EPS possess a better resilience against compression than E EPS do, thus retaining water in both S EPS and the inner E EPS. 4

No description available.

We investigate the local large-scale structure of the Universe, addressing various possible issues confronting the ACDM paradigm. Primarily, we investigate the clustering statistics of the newly-completed 2 Micron All Sky Survey (2MASS), the largest all sky galaxy survey to date.The 2MASS galaxy number counts over the ͌ 4000 deg(^2) APM survey area are found to be low compared to predictions but are in good agreement with previous optical results. Surprisingly, the number counts over almost the entire sky ([b] >20 ͌ 27000 deg(^2) ) are also deficient compared to our predictions. These results do not appear to be significantly affected by systematic errors. Assuming a ACDM cosmology, the observed deficiencies in the APM survey area and for [b] >20 represent ͌ 2.5σ and ͌ 4.0σ fluctuations in the local galaxy distribution respectively. These results are therefore potentially at odds with the form of clustering expected on large scales. We examine the form of galaxy clustering to Ṯ < 1000 h (^-1) Mpc scales using the 2MASS angular power spectrum. We find a 3σ excess over mock ACDM results; however this is not enough to account for the observed number counts mentioned above. We determine the implied cosmological constraints; the 2MASS galaxy angular power spectrum is, in fact, in strong support of ACDM, with a measured power spectrum shape of Γ (_eff) = 0.14±0.02. In addition, we determine a K(_8)-band galaxy bias of b(_K) = 1.39 ± 0.12.We determine high-order correlation functions of the 2MASS galaxy sample to extremely large scales (Ṯ < 1000 h (^-1)). The results are in strong support of Gaussian initial conditions and hierarchical clustering; we reject primordial strong non-Gaussianity at the ͌ 2.5σ confidence level. Unlike all previous such analyses, our results are relatively robust to the removal of large superclusters from the sample. We also measure a K(_8)-band quadratic galaxy bias of c(_2) = 0.57 ± 0.33. This result differs significantly from previous negative constraints; we discuss a possible explanation for this apparent discrepancy. Finally, we examine the extent of possible Sunyaev-Zeldovich contamination in the first year Wilkinson Microwave Anisotropy Probe (WMAP) data using various foreground galaxy cluster catalogues. We find evidence suggesting that the associated temperature decrements extend to > 1 scales. Such a result would indicate a much higher baryon density than the concordance value; in addition, CMB power spectrum fits and the associated cosmological constraints would also be compromised.