This thesis describes an investigation of high-energy accretion in stellar-mass black holes and neutron stars using radio and X-ray observations. In particular, two of the largest Galactic X-ray binaries, with black hole masses of rv 10 M0 were examined in detail: GRS 1915+105 and Cygnus X-I. Observations were taken with radio interferometers at frequencies between 1.4 and 15 GHz. These were compared with X-ray observations made between 2 to 12 keY, taken with instrumentation on-board spacecraft in near Earth orbit. Technical developments in data transport have proved the feasibility of using the internet to transfer real-time astronomical data at gigabits per second. A proof-of-concept experiment described here, has shown that it is possible to make rapid e-VLBI observations of transient sources such as Galactic X-ray binaries. The first e-VLBI observations of GRS 1915+105 were made with the e-EVN immediately showing the inner structure of the steady jet. 'Adaptive e-VLBI' successfully proved the use of this technique to take snap shots of the inner region to then schedule further observations. A long series of MERLIN observations of GRS 1915+105 at 1.4 and 1.6 GHz are presented showing differences in the large-scale structure (> 50 mas) during various X-ray states. Polarisation measurements were also taken showing de-polarisation in the inner core during the ejection of a superluminal knot. Results have shown that the change in X-ray spectral hardness, from hard to soft, immediately coincided with the ejection of a superluminal knot; however, observations have shown no large-scale extended structure, during the so-called 'plateau' state, despite this being the strongest radio state. Only a steady jet with a flat spectrat index is observed at angular scales of less than 10 mas. Monitoring with the Ryle Telescope has then shown this steady jet to be present for periods of about 5 to 60 days every 1.3 years.

In this thesis I use the UKIDSS Ultra-Deep Survey and complementary spectroscopic survey (the UDSz) to investigate AGN and galaxy evolution across a wide redshift range 1.0 < z < 2.5. The work presented here is divided broadly into two themes: a study of AGN and how they are affected by their environment, and a study of galactic winds and feedback processes. To explore how AGN are affected by their environment, I use angular crosscorrelation techniques to study X-ray and radio-loud AGN as a function of galaxy density in the red shift range 1.0 < z < 1.5. I find that AGN preferentially reside in over dense environments at these epochs, typically residing in dark matter halos of mass M2: 5x 1013 M0 . This is in contrast to what I find in the local Universe, where typical X-ray AGN reside in a range of environments, including small groups of galaxies and the outskirts of moderately dense clusters. To study galactic winds and feedback processes, I use spectra from the UDSz spectroscopic survey. This survey is a recent enhancement of the UDS, in which rv3500 high redshift galaxy spectra were obtained using the VIMOS and FORS2 spectrographs on the VLT. I discuss the data reduction and the process of redshift determination of the VIMOS data. rv1600 galaxy spectra are used in the work on feedback and galactic winds as a direct consequence of the reduction. Using the UDSz spectra, I then present a study of galactic-scale outflows at redshift 0.71 < z < 1.63. For this work, I use a large sample of galaxies with an average stellar mass of rv 109.5 M0 and spanning a wide range of rest-frame colours, which represent typical star-forming galaxies at this epoch. By stacking the data by galaxy property, I find that outflows are present in virtually all spectral stacks, with velocities ranging from 100-1000 km S-1. The highest velocity outflows (2:500 km S-1) are found in galaxies with the highest stellar masses and the youngest stellar populations. Our findings suggest that high velocity outflows are mostly driven by star-forming processes rather than AGN, with implied mass outflow rates COlTlparable to the rates of star formation. Such behaviour is consistent with models required to reproduce the high redshift mass-metallicity relation. To investigate the mass-metallicity relation further, I use the UV region of the electromagnetic spectrum to investigate metallicities of galaxies at redshifts 1.0 < z < 2.5. I confirm that, at this epoch, the most massive galaxies tend to be the most metal rich. I also find that these galaxies have a lower metallicity than analogous galaxies in the local Universe. From our investigation into galactic winds and feedback processes, I conclude that these mechanisms have an extremely important role to play in galaxy evolution. Consequently. disentangling the precise balance of star formation, galactic winds and AGN-driven winds in galaxies will remain a significant topic of research in astronomy in years to come. ix \.

The braneworld paradigm provides an interesting framework within which to explore the possibility that our Universe lives in a fundamentally higher dimensional space- time. In this thesis we investigate black holes in the Randall-Sundrum braneworld scenario. We begin with an overview of extra-dimensional physics, from the original proposal of Kaluza and Klein up to the modern braneworld picture of extra dimensions. A detailed description of braneworld gravity is given, with particular emphasis on its compatibility with experimental tests of gravity. We then move on to a discussion of static, spherically symmetric braneworld black hole solutions. Assuming an equation of state for the "Weyl term", which encodes the effects of the extra dimension, we are able to classify the general behaviour of these solutions. We then use the strong field limit approach to investigate the gravitational lensing properties of some candidate braneworld black hole solutions. It is found that braneworld black holes could have significantly different observational signatures to the Schwarzschild black hole of standard general relativity. Rotating braneworld black hole solutions are also discussed, and we attempt to generate rotating solutions from known static solutions using the Newman-Janis complexification "trick".

In this thesis two aspects of braneworld models are studied. A new attempt at finding the metric of a braneworld black hole within the second Randall-Sundrum model is explored. Branes containing distributions of perfect fluid are embedded in a variety of 5-dimensional 5O(4)-symmetric bulk spacetimes so that the Israel junction conditions are satisfied. A particular class of time-dependent embeddings are studied and shown to be unable to describe the braneworld black hole. Static trajectories are then investigated in five-dimensional anti-de Sitter and Schwarzschild backgrounds. These reveal a wide variety of permissible trajectories which are classified according to their energy-momentum profiles. The static embedding of branes in a Schwarzschild-anti-de Sitter spacetime is then explored, revealing objects with possible interpretation as "braneworld stars”. The evaporation of higher-dimensional rotating black holes, both on the brane and in the bulk is studied from an analytical perspective. A matching technique is employed to derive the solution for the radial component of the fields of scalars, fermions and gauge bosons propagating in the brane-induced line-element of a higher-dimensional rotating black hole. These solutions are used to calculate Hawking radiation spectra from a black hole in the spin-down phase of its lifetime within the Arkani-Hamed-Dimopoulos-Dvali model. The same method is used to calculate the emission of scalar fields into the bulk spacetime of a higher-dimensional rotating, black hole and a comparison is made between brane and bulk emission rates. Finally the matching technique is applied to the problem of graviton emission in the bulk from a higher-dimensional Schwarzschild black hole.

We present the evidence for and intriguing black hole/qubit correspondence. This correspondence will map the entanglement classification of three and four qubits over to the BPS and extremal classification of black holes in the STU model. We will start by looking at BPS black holes and use a variety of means to classify them and calculate their orbits. We will discover that three qubits, or more accurately, three real qubits will exhibit exactly the same structure as the black holes. This will allow us to identify the entropy of the black hole with the entanglement of the qubits. A mathematical framework known as the Freudenthal triple system will be used to classify both systems. We will be able to use the wrapped branes picture of the black holes as an explanation of the binary nature of the qubit. We will then develop this correspondence further and use the mathematics of nilpotent orbits and the Kostant-Sekiguchi correspondence to directly map the classification of extremal black holes to the entanglement classification of four qubits. We will discover that the classification of four qubits is related to the distinct orbits that exists of the SL(2,C)4 on nilpotent (2, 2, 2, 2). We will also discover that the extremal black holes of the STU model correspond to nilpotent orbits of the Lie algebra so4,4. We will then use the Kostant-Sekiguchi correspondence as a diffeomorphism between these two types of orbits.

No description available.

Understanding the formation and evolution of galaxies is one of the primary research goals of astronomy today. Galaxies are observed to have a range of masses, colours and morphologies, and various processes, including feedback, have been proposed to explain these differences. Some of these processes are related to the environment in which a galaxy resides. In this Thesis I present the results of three projects I have undertaken to help increase our understanding of galaxy formation. The first was to investigate the different methods of structure detection used in simulations. Placing an identical subhalo at different radii inside a larger halo demonstrated that subhalo mass recovery is radially dependent. Subhaloes closer to the centre of a halo are recovered smaller than haloes near the edge, but their peak circular velocity is less affected. The second project set about investigating different ways of measuring galaxy environment. Observationally galaxy environment is most commonly measured through nearest neighbours or fixed apertures, and these have different relationships to the underlying dark matter haloes. Fixed aperture measures are sensitive to halo mass and best probe the `large-scale environment' external to a halo. Meanwhile nearest neighbour measures are insensitive to halo mass and best probe the `local environment' internal to a halo. The final project involved implementing the Accretion Disc Particle (ADP) model of black hole growth within a cosmological, large volume simulation, including cooling, star formation and feedback. Comparing this method with a modified Bondi-Hoyle model allows for the investigation of how accretion rates affect feedback and galaxy properties. ADP suffers from the limited resolution of large-scale simulations and produces unphysically large accretion discs. Both models can reproduce the local black hole scaling relations, but produce black hole mass functions that do not agree with observations.

Radio galaxies and quasars are among the largest and most powerful single objects known and are believed to have had a significant impact on the evolving Universe and its large scale structure. Their jets inject a significant amount of energy into the surrounding medium, hence they can provide useful information in the study of the density and evolution of the intergalactic and intracluster medium. The jet activity is also believed to regulate the growth of massive galaxies via the AGN feedback. In this thesis I explore the intrinsic and extrinsic physical properties of the population of Fanaroff-Riley II (FR II) objects, i.e. their kinetic luminosities, lifetimes, and central densities of their environments. In particular, the radio and kinetic luminosity functions of these powerful radio sources are investigated using the complete, flux limited radio catalogues of 3CRR and BRL. I construct multidimensional Monte Carlo simulations using semi-analytical models of FR II source time evolution to create artificial samples of radio galaxies. Unlike previous studies, I compare radio luminosity functions found with both the observed and simulated data to explore the best-fitting fundamental source parameters. The Monte Carlo method presented here allows one to: (i) set better limits on the predicted fundamental parameters of which confidence intervals estimated over broad ranges are presented, and (ii) generate the most plausible underlying parent populations of these radio sources. Moreover, I allow the source physical properties to co-evolve with redshift, and I find that all the investigated parameters most likely undergo cosmological evolution; however these parameters are strongly degenerate, and independent constraints are necessary to draw more precise conclusions. Furthermore, since it has been suggested that low luminosity FR IIs may be distinct from their powerful equivalents, I attempt to investigate fundamental properties of a sample of low redshift, low radio luminosity density radio galaxies. Based on SDSS-FIRST-NVSS radio sample I construct a low frequency (325 MHz) sample of radio galaxies and attempt to explore the fundamental properties of these low luminosity radio sources. The results are discussed through comparison with the results from the powerful radio sources of the 3CRR and BRL samples. Finally, I investigate the total power injected by populations of these powerful radio sources at various cosmological epochs and discuss the significance of the impact of these sources on the evolving Universe. Remarkably, sets of two degenerate fundamental parameters, the kinetic luminosity and maximum lifetimes of radio sources, despite the degeneracy provide particularly robust estimates of the total power produced by FR IIs during their lifetimes. This can be also used for robust estimations of the quenching of the cooling flows in cluster of galaxies.

We investigate the possibility that present-day galaxies and their dark matter halos contain a population of massive black holes (MBHs) that form by hierarchical merging of the black hole remnants of the first stars in the Universe. Some of the MBHs may be large enough or close enough to the centre of the galactic host that they merge within a Hubble time. We estimate to what extent this process could contribute to the mass of the super-massive black holes (SMBHs) observed in galactic centres today. The relation between SMBH and galactic bulge mass in our model displays the same slope as that found in observations. Many MBHs will not reach the centre of the host halo, however, but continue to orbit within it. In doing so MBHs may remain associated with remnants of the satellite halo systems of which they were previously a part. Using a semi-analytical approach that explicitly accounts for dynamical friction, tidal disruption and encounters with galactic disks, we follow the hierarchical merging of MBH systems and their subsequent dynamical evolution inside the respective host halos. In this context two types of dynamical processes are examined in more detail. We predict the mass and abundance of MBHs in present-day galactic halos and also estimate the MBH mass accretion rates considering two different accretion scenarios. On this basis we determine the bolometric, optical and X-ray luminosity functions for the accreting MBHs using thin disk and advection dominated accretion flow models. Our predicted MBH X-ray emissions are then compared with observations of ultra-luminous X-ray sources in galaxies. We find that the slope and normalisation of the predicted X-ray luminosity function are consistent with the observations. We also estimate the rate of gravitational wave events received from MBH mergers across all redshifts. At the end of their lives the first stars may explode in supernovae that are associated with gamma ray bursts (GRBs). Provided these are in principle detectable we have estimated the expected rate of events observed.

In this thesis we investigate selection effects in astrophysical observations. We demonstrate that the determination of the quasar black hole mass function and Eddington ratio distribution via observations are biased. By modelling the quasar selection function and the black hole mass measurement process we show that one is able to infer the true distribution of physical quantities from observations. We present the intrinsic accretion rates of AGN, the intrinsic accretion rates and the black hole mass function for optically selected quasars up to redshift of two. The results show that the Eddington limit continues to be a real physical limit to black hole accretion. We present a new upper limit of black hole masses from the inferred intrinsic black hole mass function and demonstrate the need of a mass dependent accretion rate in accordance with down sizing. Finally we investigate correlations between radio luminosity and observed black hole mass for optically selected quasars. We first show that mixing of fiat and steep spectrum quasars leads to results that are dependent on the observing frequency, and therefore should be treated with caution. We demonstrate that beaming of the radio core together with an orientation dependent optical selection effect can give rise to a bimodal distribution in the radio luminosities of optically selected quasars.