In this thesis we use techniques associated with the statistical properties of large stochastic datasets to probe the scaling properties of solar wind timeseries. In particular, we consider single-point spacecraft measurements of interplanetary vector quantities such as velocity and magnetic field. These techniques are first applied to well-known distributions such as the normal distribution in order to demonstrate the scaling properties associated with different types of timeseries. For example, a normal distribution can be thought of as the steps of a Brownian walk and is a fractal process or in other words there is a power-law relation between stepsize and the length of the walk. This simple behaviour is complicated when intermittency (similar to large jumps in a random walk) and multifractality are introduced. We also show other model distributions exhibiting these effects and the consequences on the statistical analysis results. These methods are then applied to in situ solar wind observations by monitors such as the ACE and Ulysses spacecraft. ACE occupies a privileged position at the Lagrangian point between the Sun and the Earth, whereas Ulysses was the first spacecraft to explore the Sun’s polar regions. We are thus able to show the scaling behaviour of velocity and magnetic field fluctuations for a wide range of different solar wind conditions (such as fast and slow solar wind speeds) and between periods of maximum and minimum solar activity and to examine both ecliptic and polar solar wind behaviour. The large datasets available mean we can probe fluctuations over a wide range of scales from the inertial range to the larger energy containing scales. We find that the polar inertial range (small-scale) behaviour for fast solar wind can be summarised for the magnetic field by a single function, which holds for all components and for different successive solar minima. We further use ACE measurements to examine the velocity and magnetic field large-scale fluctuations normal and parallel to the local background magnetic field and propose that the parallel velocity component carries the signature of coronal processes convected outwards into the solar wind. The scaling exponents obtained constrain the models for these processes.

Observations of the cataclysmic variable systems EX Dra, Z Cha, and OY Car using multi-wavelength data ranging from near-infrared to X-ray bands are presented and analysed. Obscuration of the white dwarf by intervening material is discussed in context of all three systems, including the confirmation of iron lines in the spectrum of OY Car and the absorbing nature of the accretion disc upon the soft X-ray band in Z Cha. Evidence for spiral shocks and slingshot prominences from the secondary star are found in EX Dra, while the extent of Z Cha's boundary layer is probed with extensive modelling of simultaneous optical and X-ray data. Combined with a spectral analysis, this leads to the conclusion of a truncated inner disc present within the system. The first radial velocity measurement of OY Car's red secondary star is presented, and used to produce a fully spectroscopic determination of the system's mass ratio which is compared to previous attempts using the photometric method. The second part of this thesis deals with the improvement of the Ultracam and Ultraspec instruments. For the former, increased colour precision is achieved by careful calibration of the instrument's filter response with respect to the SDSS system; a charge modulation problem is investigated and quantified; and the development of a software system designed to improve observation and reduction workflow is detailed. For Ultraspec, a careful analysis of the CCD parameters is performed in order to prepare the instrument for scientific quality data publication, including an analysis of spurious charge found present. It is also shown that the AC coupling of the video circuit in the CCD can cause erroneous values in the readout but can be rectified, and presence of charge trailing caused by electron traps is investigated with preliminary corrections shown.

In this thesis the Big Bang and inflation theory are reviewed. The success of inflation is largely due to the predicted generation of inhomogeneities. We review the dynamical equations of motion for an accelerating expansion of the Universe and the flow equations which describe the evolution of the Hubble slow-roll parameters. We use cosmological perturbation theory to find a new expression relating comoving curvature perturbations generated during inflation to density perturbations responsible for structure formation. Primordial black holes (PBHs) may form from primordial perturbations. We compile and update constraints on the abundance of PBHs. We then use our new relationship to translate these abundance limits into constraints on the power spectrum of primordial curvature perturbation. In addition we investigate the possible formation of ultracompact dark matter minihalos (UCMHs) which may also form from primordial pertubations. If dark matter is in the form of weakly interacting massive particles (WIMPs) then WIMP annihilation may produce a detectable gamma-ray signature. We calculate the potential constraints which would arise from a detection by the Fermi satellite. Finally, we investigate single field models of inflation using a stochastic technique to generate a large ensemble of models. Using a numerical approach along with a modified flow algorithm we find models of inflation compatible with all cosmological data which have large perturbations on small scales. Significant PBH formation occurs in models in which inflation can continue indefinitely and is ended via a secondary mechanism. We use our PBH constraints to eliminate such models which overproduce PBHs. In this work we demonstrate that PBH constraints, although weak, are effective at constraining models of inflation. We also demonstrate that a gamma-ray detection from UCMHs could potentially constrain the power spectrum of curvature perturbation on small scales very tightly in the near future.

This thesis studies the origin of local S0 galaxies and their possible links to other morphological types. To address these issues, two different approaches have been adopted: a detailed study of the stellar populations of S0s in the Fornax Cluster and a study of the Tully-Fisher Relation (TFR) of local S0s in different environments. The analysis of the central absorption line indices of 9 S0 galaxies in the Fornax Cluster indicates that they correlate with central velocity dispersions (sigma0). However, the stellar population properties of these S0s indicates that the observed trends seem to be produced by relative differences in age and alpha-element abundances and not in metallicity as previous studies have found in ellipticals. The observed scatter in the line indices versus sigma0 relations can be partially explained by the rotationally-supported nature of many of these systems. It was also confirmed that the dynamical mass is the driving physical property of all these correlations and in our Fornax S0s it has to be estimated assuming rotational support. A study of the local B- and Ks-band TFR in S0 galaxies shows that these objects lie systematically below the TFR for nearby spirals in both the optical and infrared bands. This offset can be crudely interpreted as arising from the luminosity evolution of spiral galaxies that have faded since ceasing star formation. However, a large scatter is also found in the S0 TFR, which means that these galaxies cannot have formed exclusively by this simple fading mechanism after all transforming at a single epoch. For the Fornax Cluster data, the offset from the TFR correlates with the estimated age of the stars in the centre of individual galaxies implying that part of the scatter in the S0 TFR arises from the different times at which galaxies began their transformation.

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.

One of the most fundamental observational probes of galaxy evolution is determining the build-up of stellar mass. However, around half of all energy ever emitted from galaxies has been absorbed and reprocessed by dust, which is an end-product of stellar evolution. In order to obtain a more complete understanding of galaxy evolution, sensitive observations in the far-infrared and submillimetre are required where the dust emission peaks. Previous surveys have found galaxies were significantly dustier at earlier times, but the cause of this evolution, and the origin of the dust, are hotly debated topics in astrophysics. With the Herschel Space Observatory, a complete census of the dusty galaxy population has now recently been obtained. In this thesis I investigate the properties of the diverse dusty galaxy population via a panchromatic approach, utilising data from the UV to the submillimetre to study galaxy evolution. Using the first unbiased survey of dust in the local Universe, I explore the properties of galaxies in the local Universe as a function of morphology and highlight particularly interesting populations which are traditionally thought to be passive. The star-formation histories, dust content and environments of dusty early-type galaxies and passive spirals are investigated. I show that dusty early-type galaxies comprise a small minority of the general early-type galaxy population (5.5%), and harbour on average 5.5x10^7 M_sun of dust, which is comparable to that of some spiral galaxies in our sample. I compare these dusty populations to control samples to investigate how these galaxies are different to the general galaxy population. High redshift submillimetre galaxies are the most actively star-forming and dusty galaxies in the Universe. Constraining the properties of these galaxies is important for understanding the evolution of massive galaxies and galaxy evolution models in general. Using panchromatic data from the UV to the submillimetre, I explore the physical properties of a sample of ~250um rest-frame selected galaxies at high redshift, and compare them to dusty galaxies at low redshift selected in a similar way, to investigate the differences in the dusty galaxy populations over cosmic time. I find high redshift dusty galaxies have significantly higher star-formation rates and dust masses than z<0.5 dusty galaxies selected to have a similar stellar mass. Galaxies which are as highly star forming and dusty as those at z~2 are rare in the local Universe. My results support the idea that the most dusty galaxies at high redshift are a heterogeneous population, with around 60% of our sample consistent with secular evolution, and the other 40% of galaxies are starbursting, possibly merger-driven systems. The origin of dust in galaxies at both low and high redshifts presents a challenge to current theories of galaxy evolution. Recent work has revealed a `dust budget crisis', whereby the mass of dust observed in galaxies at low and high redshift cannot be accounted for by stellar mass loss from low-intermediate mass stars. I tackle this challenge using chemical evolution modelling of the high redshift submillimetre galaxies, with a detailed treatment of the star-formation histories and the dust sources and sinks in these galaxies. It is clear that a significant mass of dust must be from supernovae and/or grain growth; however, the origin of dust in high redshift dusty galaxies remains uncertain. I also consider the impact of inflows and outflows of gas, and the effect of changing the IMF on the physical properties of high redshift dusty galaxies.

This thesis describes the properties and evolution of massive (Mstellar ≥ 1011h−2 70 M⊙) galaxies at 0 < z < 3, including their relationship to lower mass systems. Present-day massive galaxies are composed mostly of early-type objects, although it is unknown whether this was also the case at higher redshifts. In a hierarchical assembling scenario the morphological content of the massive population is expected to change with time from disk-like objects in the early Universe to spheroid-like galaxies at present. We first probe this theoretical expectation by compiling a large sample of massive galaxies in the redshift interval 0<z<3. Our sample of 1082 objects is composed of 207 local galaxies selected from the Sloan Digital Sky Survey, plus 875 objects observed with the HST from the POWIR/DEEP2 Survey and the GOODS NICMOS Survey. 639 of our objects have spectroscopic redshifts. Our morphological classification is done in the V-band restframe both quantitatively (using the S´ersic index as a morphological proxy) and qualitatively (by visual inspection). Using both techniques we find a significant change in the dominant morphological class with cosmic time. The fraction of earlytype galaxies among the massive galaxy population has changed from ∼20-30% at z∼3 to∼70%at z=0. Spheroid-like galaxies have been the predominantmorphological massive class only since z∼1. This morphological evolution is so far based on the detailed morphological analysis of these objects, which ultimately rests on the shape of their surface brightness profiles. To explore the consistency of this scenario, we examine the kinematic status of a small subset of these galaxies. We have observed in the H-band 10 massive galaxies at z ∼ 1.4 with the Integral Field Spectrograph SINFONI at VLT. Our sample of galaxies have been selected purely by their photometric stellar mass without accounting for any morphological criteria a priori, and having [OII] line equivalent widths of > 15°A Abstract 5 to secure their kinematical measurements. Through a 3D kinematical spectroscopy analysis we conclude that half (i.e. 50±7%) of our galaxies are compatible with being rotationally supported disks in agreement with our previous photometric expectations. This is around a factor of two higher than what is observed in the present Universe for objects of the same stellar mass. Strikingly, the majority of these massive galaxies show clear and fairly large rotational velocity maps, implying that massive galaxies acquire rapidly rotational support and hence gravitational equilibrium. In addition, we have evidence, based on our measured velocity dispersions and imaging, to favour a picture in which minor (and major) mergers are the main driving force behind the evolution of this massive galaxy population. There is also cumulative evidence showing that the formation process for a number of these massive galaxies occur at even higher redshifts (z > 5) and that their morphological features are preserved when observing them in the UV restframe. Hence, we made use of the excellent capabilities of GNS to locate and study massive galaxies beyond z = 3 within our imaging and secondly determining whether the strong masssize relation found for the most massive objects holds as well for lower mass objects. Our findings show the extreme compactness of massive objects at z > 3 and only a moderate evolution in size below our 1011M⊙ mass limit.

Cosmic strings are linear concentrations of energy that may have been formed after cosmological phase transitions in the early universe. Cosmic superstrings are analogous objects arising in string theory, and in particular in models of brane inflation. The latter possess two particular features, which differentiate them from the ordinary cosmic strings: a reduced intercommuting probability, and the ability to form junctions. This thesis is concerned with the dynamics and cosmological implications of cosmic strings and superstrings with junctions. In Chapter1, we give a brief introduction to the standard Big Bang model and t he inflationary paradigm. W e also discuss cosmic string formation after the spontaneous breaking of an Abelian U (I) gauge symmetry in the early Universe. In Chapter 2, we present an overview of cosmic string dynamics using the Nambu-Goto method. We discuss the properties of individual cosmic string segments and loops, as well as network evolution in an expanding Universe. We also introduce cosmic superstrings, and review the Nambu-Goto approach to study the evolution of junctions and the kinematic constraints that govern their formation. We conclude with the study of junctions in an expanding spacetime and present an exact solution for a closed loop of three strings and two junctions in a de Sitter Universe. In Chapter3, we compare the two different approaches developed to study the dynamics of strings with junctions. We first extensively study the dynamics and stability of a cosmic string loop with junctions using the modified Nambu-Goto approach. Comparing our results with a field theory model that permits junctions we find very good agreement. The Nambu-Goto method is once again confirmed to be a good approximation for studying cosmic string configurations. In Chapter4, we review the observational signatures of cosmic strings. More specifically, we concentrate on their gravitational effects, discussing results and constraints from lensing, gravitational radiation, CMB and pulsar timing. We also present recent results of the case of cosmic (super)-strings with junctions. Chapter5 is concerned with the cosmological implications of cosmic superstring networks. W e first study the scaling patterns of such networks for different values of the string coupling g8, and different charges (p, q) on the strings. We then focus on their CMB signatures and derive upper bounds for the fundamental tension MuF using CMB and pulsar timing constraints. The difference between the scaling behaviour of the networks at high and low values of g, is imprinted as a movement of the position of the peak in the B –mode spectrum. Together with the constraints on GMuF from CMB and pulsar timing, this allows for the exciting possibility to constrain the value of the string coupling g8 using CMB data. We conclude in Chapter 6.

In this thesis I primarily use the UKIDSS Ultra-Deep Survey (UDS) to investigate the effect environment has on galaxies across the redshift range 0.25 < z < 3.25. The UDS is a K-selected survey so it does not suffer from the strong iases that affect optical surveys at high redshift (z > 1). The combination of a large contiguous area (0.77 deg2) and depth (KAB ∼24) allows us to study a range of environments up to a redshift of z ∼3. Due to the multiwavelength coverage we are able to obtain reliable photometric redshifts which are necessary for studies of environment. I utilise progressive releases of the UDS data to study the effect environment has on the rest frame (U-B) colour of galaxies. Using the U-B colour and absolute K-band magnitude I was able to divide our galaxies into red and blue and study their average environments. In this thesis I also employ data from the spaced based, GOODS NICMOS Survey (GNS) to help study the environments out to high redshift (z ∼3), in which I also study the colour-density relation. The UDS project was recently enhanced by the addition of ∼3500 spectra of highredshift galaxies, obtained using the VIMOS and FORS2 instruments on the VLT. The data reduction and redshift determination for the VIMOS data is discussed and is exploited to improve the photometric redshifts for the study of environments in the DR8. The ∼1600 reliable spectra are utilised directly to investigate the effect that environment has on the spectral properties of galaxies. We find that red galaxies are on average in denser environments than blue galaxies up to a redshift of z ∼2. The colour-density relation is strongest at the lowest redshifts studied (0.25 < z < 0.75) and gradually weakens out to redshift z ∼2 where it becomes almost flat. We also observe a distinct positive correlation between K-band luminosity and local density for galaxies between 1.25 < z < 2.75. This relation becomes strongest for the blue galaxies on the smallest scale studied (125kpc radius). Through studying the effect of environment on spectral features we have found evidence that galaxies between a redshift of 1.25 < z < 2.2 have significantly larger values of the C(29-33) index, in denser environments, indicating that older/more passive galaxies, even at this high redshift, reside in denser environments. The other indices similarly tend to indicate that older galaxies inhabit denser environments, whilst the environment has little effect on the properties of the blue galaxies. The spectra also indicate that one age determining index, C(29-33) is a very good indicator of colour for samples of galaxies at high redshift where the traditional measures such as the 4000°A break strength are difficult to obtain. This study of environments leads us to the final conclusion that although the stellar mass of a galaxy is clearly important in determining its evolution, its environment is also an important driver in a galaxy’s evolution. Disentangling the relative importance of these drivers (nature vs nurture) will be a major goal in the coming years.

In this thesis, we investigate the internal kinematics and stellar populations of a subsample of the bulges of nearby galaxies defined by Balcells & Peletier (1994). To do that we have analysed minor axis spectroscopic data of the sample together with Integral Field observations of one the most interesting galaxies in it (NGC7332). We introduce, for the first time, the use of single-burst stellar population models to obtain stellar velocities, velocity dispersions and higher order Gauss-Hermite moments (h_3, h_4) from galaxy spectra in the near-infrared Ca II triplet region. We detect small-amplitude minor-axis rotation, generally due to inner isophotal twists as a result of slightly triaxial bulges or misaligned inner disks. Velocity dispersion profiles, which extend well into the disk region, show a wide range of slopes. Flattened bulges tend to have shallower velocity dispersion profiles. The inferred similarity of radial velocity dispersion profiles of bulge and disk supports the interpretation of these bulges as thickened disks. We also investigate the position of our sample on the fundamental plane of early-type galaxies. We find that bulges, both in the B and K band, lie close to but slightly below the relation defined by ellipticals and S0s. The most deviant point is NGC7332, whose offset w.r.t the FP cannot be explained by measurement errors. Besides, there are hints that bulges of later morphological type are situated below the other bulges in our sample. The fact that bulges lie so close to the FP of ellipticals and S0s implies that their formation epoch must have been similar to that of cluster Es and S0s. We then proceed to present measurements of near-IR Ca triplet (CaT, CaT*), Paschen (PaT) and Magnesium (MgI) indices for the same sample. We find that CaT* decreases with central velocity dispersion (sigma) with small scatter, unlike other metal indices that generally increase. Our result shows that the CaT* - sigma relation is independent of galaxy type from ellipticals to intermediate-type spirals. Finally we have made use of SAURON observations to unravel the origin of peculiar features in the S0 galaxy NGC7332. We have discovered a Kinematically Decoupled Core, found kinematic evidence for a central disk and mapped a rather disturbed gas distribution counter-rotating w.r.t the stellar body of the galaxy. 2D stellar populations maps reveal that NGC7332 is young everywhere. The fact that we see gas inflow now, together with many features indicates that there must have been gas infall for Gyrs in a row, leading to a continuum formation of this galaxy.