We study the coevolution of black holes (BHs) and their host galaxies through cosmic time. The calculation is embedded in the GALFORM semi-analytic model which simulates the formation and evolution of galaxies in a cold dark matter (CDM) universe. The BH and galaxy formation models are coupled: during the evolution of the host galaxy, hot and cold gas are added to the BH by flows triggered by halo gas cooling, disc instabilities and galaxy mergers. This builds up the mass and spin of the BH, and the resulting accretion power regulates gas cooling and subsequent star formation. Using the Blandford–Znajek mechanism for jet production to calculate the jet power, our model reproduces the radio loudness of radio galaxies, LINERS and Seyferts, suggesting that the jet properties of active galactic nuclei (AGN) are a natural consequence of both the accretion rate onto and the spin of the central BH. The model also reproduces the observed luminosity functions (LF) of AGN (optical, soft and hard X-ray, and bolometric) for a wide range of redshifts (0 < z < 6). We find downsizing in the AGN population, in terms of the differential growth with redshift of the space density of faint and bright AGN. This arises naturally from the interplay between the different accretion channels that drive the growth of BHs. The predictions of our model are extended to 6 < z < 20 to study the early growth of BHs. Our model predicts that the first 10^{8} M⊙ BHs appear at z = 14, along with the first luminous quasars. Finally, we explore the dependence of AGN activity and luminosity on environment. We find that quasars inhabit haloes with masses 10^{12} − 10^{13} M⊙. Quasar activity in more massive haloes in suppressed due to AGN feedback. In contrast, radio galaxies occupy the centres of the most massive haloes. Our model represents the first consistent demonstration that the phenomenology and evolution of AGN can be naturally explained by the coeval evolution of galaxies and BHs, coupled by AGN feedback, in a CDM universe.

In this thesis we study how subhaloes evolve and interact in the central regions of galactic dark matter haloes in a ΛCDM universe. We examine the effect that subhalo impacts have on disc galaxies and what visible signatures they leave behind. We use the Aquarius simulations, a set of high resolution simulations of Milky Way mass haloes, as the basis of the work in this thesis. We summarise the main properties of these haloes and show that they are typical haloes for most characteristics. We develop a method to approximate the potential of host haloes that helps us understand how subhaloes evolve in the tidal field of their host. Using a basis function expansion method, we show that it is possible to create a time-evolving density/potential approximation of the late growth of simulated N-body dark matter haloes, and that particle and subhalo orbits can be integrated in this realistic, time-varying halo potential approximation at much lower computational cost than the original simulations. Using samples of subhaloes extracted from the Aquarius haloes, we estimate the disc heating caused by substructure bombardment using the Benson et al. (2004) semi-analytical model. A critical evaluation of the model, however, finds that there are problems with the original implementation, including a numerical factor, that call into question its validity. We then approach the same problem using high resolution N-body simulations of subhalo interactions with discs. We find that only the most massive of subhaloes appreciably affect stellar discs, heating and thickening them, and that the majority of any heating occurs at early times and happens quickly. However, the substructure bombardment since redshift one is negligible in most of the haloes, and in the haloes that do show significant heating it is caused by a single massive subhalo.

In this thesis I present a detailed study of the optical to X-ray spectral properties of Active Galactic Nuclei (AGN). We propose a new broadband SED model which combines the standard accretion disc emission, low and high temperature Comptonisation components by introducing a corona radius. Applying the new models to broadband spectral data, we found that RX J0136.9-3510 and RE J0134+396 have similar {\it rms} spectra and broadband SEDs, representing a distinct spectral state which can only be attained by super Eddington flows. A detailed optical and X-ray spectral analysis is then carried out for a big sample of 51 unobscured nearby type 1 AGNs. We find that NLS1s tend to have softer 2-10 keV spectra, lower black hole mass, higher Eddington ratio, higher $\alpha_{ox}$ index and smaller coronal radius. The edge of Balmer continuum is shifted redwards and smoothed by more than predicted by the FWHM of the Balmer emission lines. A new method called `Correlation Spectra Technique (CST)' is proposed, which is powerful for multi-waveband spectral analysis. We find that among the three Balmer line components, the broad component has the best correlation with hard X-ray emission. Optical oxygen forbidden lines all well correlate with the hard X-ray emission. We conducted a systematic cross-correlation among the 9 key SED parameters: $\Gamma_{2-10keV}$, $\kappa_{2-10keV}$, $\kappa_{5100A}$, $\lambda_{Edd}$, FWHM$_{H\beta}$, M$_{BH}$, $\alpha_{ox}$, L$_{bol}$ and L$_{2-10keV}$, and found the driven parameters to be M$_{BH}$, $\lambda_{Edd}$ and L$_{bol}$ (or equivalently $\dot{M}$). AGN's intrinsic SEDs exhibit strong diversity and changes similarly with $\lambda_{Edd}$, $\kappa_{2-10keV}$, $\kappa_{5100}$, $\Gamma_{2-10keV}$, FWHM$_{H\beta}$ and M$_{BH}$. However, the SED shape is not sensitive to L$_{bol}$.

We present a study of the evolution of galaxies in massive X-ray selected clusters across half the age of the Universe. This encompasses galaxies on the red sequence from the Brightest Cluster Galaxy (BCG) to the faint red population. We begin at the tip of the red sequence with an investigation into the near infrared evolution of BCGs since z =1. By comparing the BCG Hubble diagram and near-infrared colour evolution to a set of stellar population and semi-analytic models we constrain the evolution and formation redshift of these massive galaxies. Moving down in luminosity from the BCG, in chapter 3 we study the build up of the red sequence in massive clusters. To achieve this we compare the luminosity functions for red galaxies in a homogeneous sample of ten X-ray luminous clusters at z ~ 0.5 to a similarly selected X-ray cluster sample at z ~ 0.1. We quantify this result by measuring the dwarf to giant ratio to ascertain whether faint galaxies have joined the red sequence over the last 5 Gyr. In chapter 4 we study the evolution of the red sequence slope in massive clusters from z=l to present day. We compare our observed slope evolution to that predicted from semi- analytical models based on the Millennium simulation. We also look for trends between the red sequence slope and other cluster observables, such as X—ray luminosity, to investigate whether this will effect cluster detection methods which search for a colour-magnitude relation. In the final science chapter we present the details of our own cluster detection algorithm. This simple algorithm is based on finding clusters through the near-infrared and optical properties of the red sequence, drawing on our galaxy cluster evolution research. We describe the application of the algorithm to object catalogues from the UKIDSS DXS fields in order to find clusters at z ~ 1. To confirm the presence of the clusters we employ deep multi-object spectroscopy on the photometric members. The clusters found in this study are fed back into the high redshift regime of our galaxy evolution research.

Astrophysical black holes are the simplest possible objects. They are completely described by only two parameters in general relativity, their mass and the specific angular momentum, spin. The spin is a fundamental characteristic of a black hole, but unlike mass it leaves a mark on space-time only very close to the event horizon, and is therefore more difficult to measure. The observational relevance of the spin comes from the fact that it sets the size scale of the last stable orbit around the accreting black hole, dragging the accretion disc farther in the faster it spins. Black hole spin is a very controversial topic in both stellar and supermassive black holes. There are two methods to determine spin in binary systems, using either the direct disc continuum or the reflected emission. These can give significantly different values, and understanding the source of this discrepancy is important especially for interpreting AGN spin, where only the reflection method can be used. We have strived to understand and carefully model the time-averaged energy spectra from several Galactic black hole binaries, in order to ultimately measure the black hole spin. Achieving this has required in-depth understanding of the instruments as well as the data analysis methods. The spin leaves only minor traces in the data, and these can be affected by calibration uncertainties, uncertainties in the models and systematic uncertainties. This knowledge is absolutely essential for a detailed analysis of all relativistically smeared atomic features seen in the time-averaged energy spectra of compact objects.

A technique of constructing crude, low-resolution Spectral Energy Distributions (SEDs) for galaxies in distant clusters, using a set of intermediate bandwidth filters and a CCD detector, is developed which is capable of redressing many of the problems which have previously beset work in this field. The technique has been used to study galaxies in the distant clusters 0016+16 (z = 0.54) and Abell 370 (z = 0.37).These SEDs are then used to individually classify each object in the CCD field, ascribing both an estimated redshift and a galaxy type. The SEDs have been extended into the rest-frame ultraviolet (~ 270 nm) by imaging high redshift galaxies in blue passbands. Monitoring the behaviour of the Colour-Magnitude effect in the optical and -ultraviolet (uv) regions, indicates the presence of a new class of object which exhibits excess emission in the uv whilst having optical colours similar to nearby E/SO galaxies. The significance of this uv-excess is addressed by examining the available uv spectroscopy of nearby early-type galaxies obtained from observations carried out on the International Ul traviolet Explorer satellite. This study, in conjunction with a series of crude evolutionary models, leads to the conclusion that the uv-excess is most likely a manifestation of evolutionary differences in the spectral properties of galaxies at high redshifts, resulting from increased levels of star formation. Having developed such methods for using distant clusters of galaxies as evolutionary probes, a catalogue of candidate distant clusters is constructed from high contrast copies of deep 4m photographic plates. Finally, a series of possible future observations bcised on such a resource, combining a wide range of techniques, is outlined.

No description available.

The momentum spectra of cosmic ray protons and pions up to an energy of I50 GeV have been measured at Durham, 198 feet above sea-level. Assuming a particular model for the interaction of high energy nucleons, a new estimate has been made of the primary cosmic ray nucleon spectrum. This may be represented in the energy range 10(^10) to 3 x 10(^13) eV nucleon by the expression:-I(>E) = 0.87(^+0.52) (_-0.30) E(^-1.58) cm(^-2) sec(^-1) Sterad(^-1) where E is in units of GeV. It has been shown that a model in which the mean value of the elasticity of nucleon=air nucleus collisions is not a function of ' incident energy describes the experimental results accurately. The value found for the fraction of this energy retained by the incident nucleon is 53%. The effect of large fluctuations in elasticity from collision to collision has been investigated and found to be negligible. The result of taking fluctuations into account is to give a mean value of elasticity ~3% lower than the value obtained assuming the elasticity not to fluctuate.

Measurements on the electrification on freezing of individual water drops of diameter between 3 and 5 mm supported by an air stream have shown that the freezing behaviour of the drops is temperature-dependent. Above -10 c the freezing progressed uniformly throughout the drop from a single point. Below -10 c the outer surface of the drop froze rapidly with the exception of a small area at the top of the drop. Freezing then progressed uniformly from the base of the drop upwards. No shattering or electrification of the drops were observed during their freezing. These results are contracted with those of previous workers who observed the freezing of drops suspended on fibres. Measurements of the electrification of ice spheres supported by an air stream have indicated that the sign of the charge acquired by the spheres due to riming is temperature dependent. When the sphere is rimed by droplets at temperatures above -10 c it acquires a negative charge, and when the riming droplets are at temperatures below -10 c the ice sphere acquires a positive charge. An explanation is proposed for this effect in terms of the observed freezing behaviour of individual water drops. It is suggested that this effect could lead to thunderstorm electrification of the observed polarity. Measurements on the electrification of melting ice spheres supported by an air stream indicated that the sign of the charge acquired by the spheres is dependent on whether or not water is flung off from the sphere during melting. If no. water was flung off the charge was positive, while if water was flung off the charge was negative. This may explain the discrepancies between the laboratory and field measurements of MacCready and Proudfit.

The aim of this thesis is to analyze statistically the available QSO, LRG, galaxy and cluster samples in order to estimate the QSO-galaxy lensing anti-correlation signal and measure the mass of foreground galaxies and clusters and to estimate the QSO-LRG clustering amplitude, the QSO bias and their dependence on QSO luminosity. We also investigate the behaviour of the group-galaxy infall parameter and their rms velocity dispersions for different group memberships. The aim here is to make dynamical estimates of the group masses to check the QSO lensing results. We first cross-correlate the SDSS photo-z, g < 21, 1.0 < Z(_p) < 2.2 QSOs with g < 21 galaxies and clusters in the same areas. The anti-correlation found is somewhat less than the results of Myers et al. based on 2QZ QSOs. But contamination of the QSOs by low redshift NELGs and QSOs can cause underestimation of the anticorrelation lensing signal. Correcting for such low redshift contamination at the levels indicated by our spectroscopic checks suggests that the effect is generally small for QSO cross-correlations with g < 21 galaxies but may be an issue for fainter galaxy samples. Thus when this correction is applied to the photo-z QSO sample of Scranton et al. the anti-correlation increases and the agreement with the 2QZ results of Myers et al. is improved. When we also take into account the fainter r < 21 galaxy limit of Scranton et al. as opposed to g < 21 for Myers et al., the two observational results appear to be in very good agreement. We then measure the bias of QSOs as a function of QSO luminosity at fixed redshift (z < 1) by cross-correlating them with Luminous Red Galaxies (LRGs) in the same spatial volume, hence breaking the degeneracy between QSO luminosity and redshift. We use three QSO samples from 2SLAQ, 2QZ and SDSS covering a QSO absolute magnitude range -24.5 < M(_bj) < -21.5, and cross-correlate them with 2SLAQ (z ≈ 0.5) and AAOmega (z ≈ 0.7) photometric and spectroscopic LRGs in the same redshift ranges. The 2-D and 3-D cross-clustering measurements are generally in good agreement. Our (2SLAQ) QSO-LRG clustering amplitude (r(_0) = 6.8 (^+0.1_-0.3)h(^-1)Mpc) as measured from the semi-projected cross-correlation function appears similar to the (2SLAQ) LRG-LRG auto-correlation amplitude (r(_0) = 7.45 ± 0.35h(^-1)Mpc) and both are higher than the (2QZ-t-2SLAQ) QSO-QSO amplitude (r(_0) ≈ 5.0h(^-1)Mpc). Our measurements show remarkably little QSO-LRG cross- clustering dependence on QSO luminosity. Assuming a standard ACDM model and values for b(_LRG) measured from LRG autocorrelation analyses, we find b(_Q) = 1.45 ± 0.11 at M(_bj) ≈ -24 and b(_Q) = 1.90 ± 0.16 at M(_bj) ≈ -22. We also find consistent results for the QSO bias from a z-space distortion analysis of the QSO-LRG cross-clustering at z ≈ 0.55. The velocity dispersions fitted to QSO-LRG cross-correlation, ع (σ,π), at 680 kms(^-1) are intermediate between those for QSO-QSO and LRG-LRG clustering, as expected given the larger QSO redshift errors. The dynamical infall results give ẞ(_Q) = 0.55 ± 0.10, implying b(_Q) = 1.4 ± 0.2. Thus both the z-space distortion and the amplitude analyses yield b(_Q) ≈ 1.5 at M(_bj) ≈ -23. The implied dark matter halo mass inhabited by QSOs at z ≈ 0.55 is ~ 10(^13)h(^-1)M(_ʘ), again approximately independent of QSO luminosity. Prompted by the indications from QSO lensing that there may be more mass associated with galaxy groups than expected from virial analyses, we make new dynamical infall estimates of the masses associated with 2PIGG groups and clusters. We analyse the redshift distortions in the cluster-galaxy cross-correlation function as a function of cluster membership, cross-correlating z < 0.12 2PIGG clusters and groups with the full 2dF galaxy catalogue. We make estimates of the dynamical infall parameter, ẞ, and new estimates of the group velocity dispersions for group membership classes out to z < 0.12. We first find that, out to 30-40h(^-1)Mpc, the amplitude of the full 3-D redshift space cross-correlation function, ع (_cg), rises monotonically with group membership. We use a simple linear-theory infall model to fit ع (σ,π), in the range 5 < s < 40h(^-1) Mpc. We find that the ẞ versus membership relation for the data shows a minimum at intermediate group membership n ≈ 20 or L ≈ 2 x l0(^11)h(^-2)L(_ʘ), implying that the bias and hence M/L ratios rise by a significant factor (≈ 5x) both for small groups and rich clusters. The minimum for the mocks is at a 2 - 3x lower luminosity than for the data. However, the mocks also show a systematic shift between the location of the ẞ minimum and the M/L minimum at L ≈ l0(^11)h(^-2)L(_ʘ), given by direct calculation using the known DM distribution. Our overall conclusion is that bias estimates from dynamical infall appear to support the minimum in star-formation efficiency at intermediate halo masses. Nevertheless, there may still be significant systematic problems arising from measuring ẞ x (^1/_b) ∂P(_mass) /∂P(_gaiaxies) using large-scale infall rather than M/L using small-scale velocity dispersions