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We examine a sample of 1495 galaxies in the UDS/CANDELS field to determine the evolution of two component galaxies, including bulges and discs, within massive galaxies at the epoch 1 < z < 3 when the Hubble sequence forms. We fit all of our galaxies’ light profiles with a single Sérsic fit, as well as with a combination of exponential and Sérsic profiles. The latter is done in order to describe a galaxy with an inner and an outer component, or bulge and disc component. We develop and use three classification methods (visual, F-test and the RFF) to separate our sample into 1-component galaxies (disc/spheroids-like galaxies) and 2-component galaxies (galaxies formed by an ‘inner part’ or bulge and an ‘outer part’ or disc). We then compare the results from using these three different ways to classify our galaxies. We find that the fraction of galaxies selected as 2-component systems increases on average 50% from the lowest mass bin to the most massive galaxies, and decreases with redshift by a factor of 4 from z = 1 to z = 3. We find that single Sérsic ‘disc-like’ galaxies have the highest relative number densities at all redshifts, and that 2-component galaxies have the greatest increase and become at par with Sérsic discs by z = 1. We also find that the systems we classify as 2-component galaxies have an increase in the sizes of their outer components, or ‘discs’, by about a factor of 3 from z = 3 to z = 1.5, while the inner components or ‘bulges’ stay roughly the same size. This suggests that these systems are growing from the inside out, whilst the bulges or protobulges are in place early in the history of these galaxies. We then extend our study to a broader range in wavelength, using all available bands from the HST in the UDS/CANDELS field (H, J, i and V band) in order to calculate rest-frame magnitudes, stellar masses and SFRs for each component. We show that galaxies which are better fit as 2-component systems can have the stellar masses and star formation rates of their inner and outer components measured accurately. We examine the position of our inner/outer components in the UVJ diagram, finding that the majority of both inner and outer components lie in the star forming region (68% and 90% respectively), but that the inner portions, the likely forming bulges, are dominated by dusty star formation. Furthermore, we show that the outer components of these forming galaxies have a higher star formation rate, and the relative star formation rate increases in outer components (or discs) as redshift decreases. On the other hand, the relative stellar mass of both components remains statistically constant at z < 3. This suggests that mass formed in the outer components of galaxies is being transferred to the inner components. Finally, we find that the presence of an AGN is more common in both 1-component spheroid-like galaxies and 2-component systems (13 ± 3% and 11 ± 2%) than in 1-component disc-like galaxies (3 ± 1%), demonstrating that the formation of a central inner component likely triggers the formation of the central massive black holes in these galaxies. Lastly we explore the properties of spiral galaxies in UDS, GOODS-S and COSMOS CANDELS fields. We use the CANDELS Galaxy Zoo classification to select spiral galaxies, clumpy spiral and smooth discs. We show that galaxies classified as spirals decrease with increasing redshift, although part of this trend is due to redshift effects. After correcting such effects, we find that the number density of spirals galaxies increases by a factor of 14 ± 2 from z = 2.5 to z = 0.5. We find morphological differences between spiral galaxies and smooth discs, with the former being more ‘disky’ and asymmetric, and the latter being more centrally concentrated. We show that spiral galaxies, and in particular clumpy spirals, dominate the star formation at all redshifts, with average SFRs of SFR = 40 ± 3 Moyr−1 and SFR = 50 ± 7 Moyr−1 respectively, and that there is no benefit of having a large mass to produce spiral structures.

Submillimetre galaxies (SMGs) and post-starburst (PSB) galaxies are among the most rare and interesting classes of objects in extragalactic study. SMGs are extremely active dust-obscured galaxies in the early Universe, forming stars with an immense rate of up to 1000 solar masses per year. PSB galaxies are characterised by strong Balmer absorption lines in their spectra, consistent with a recent burst of star formation before being rapidly quenched. The origin of both of these objects and how they relate to the more common populations of red-sequence and blue-cloud galaxies remain elusive. My thesis involves weighing the dark matter halos inhabited by these rare galaxies, by investigating their clustering at 0.5 < z < 3.5. To achieve this, I use data from two deep large-scale near-infrared surveys: the UKIDSS Ultra Deep Survey (UDS) and the Cosmic Evolution Survey (COSMOS). The former survey is complemented by 850 micron maps from the SCUBA-2 Cosmology Legacy Survey, from which SMGs are identified. Both UDS and COSMOS fields also benefit from a wide range of multi-wavelength imaging, vital for the photometric selection of PSB galaxies. I begin this thesis with a review of a novel Principal Component Analysis (PCA) technique used to select PSB galaxies with broad-band photometry. I implement this technique to identify ~4000 PSB candidates in the COSMOS field up to z=2.5, making this the largest high-redshift sample of its kind. The photometric selection of PSB candidates is confronted with spectroscopy, revealing that the PCA is robust. In Chapter 3, I set out to investigate the clustering of 610 SMG counterparts identified in the UDS field. Using angular cross-correlation techniques, I found that the SMGs, on average, occupy high-mass dark matter halos (M_halo > 10^13 solar masses) at redshifts z > 2.5, consistent with being the progenitors of massive quiescent galaxies in present day clusters. I also find evidence of halo downsizing, in which SMG activity shifts to lower mass haloes at lower redshifts. In terms of their clustering and halo masses, SMGs appear to be consistent with normal star-forming galaxies at any given redshift. In Chapter 4, I obtain clustering measurements for the PCA-selected populations in the UDS and COSMOS fields, using the same methodology as Chapter 3. Low-mass, low-redshift (0.5 < z < 1.0) PSB galaxies preferentially reside in very high-mass dark matter halos (M_halo > 10^14 solar masses) and are likely to be infalling satellite galaxies in cluster-like environments. Conversely, high-mass PSB galaxies are not as clustered. These key results indicate two main channels are responsible for the rapid quenching of galaxies. High-redshift (z > 1) galaxies tend to be quenched by feedback mechanisms related to the stellar mass of the galaxy ('mass-quenching'). Processes associated with dense environments ('environmental-quenching') are likely to be the key driver of rapid quenching of galaxies in the low-redshift Universe (z < 1). Finally, we present tentative evidence that SMGs pass through a PSB phase before migrating to the red-sequence, over timescales of ~500 Myr.

This work uses data from the Herschel Space Observatory and complementary surveys to study how the properties of star forming galaxies have changed over a large redshift range. Using the likelihood ratio technique, infrared counterparts from the VIKING survey are found for a large sample of Herschel ATLAS galaxies over the three GAMA fields. I find that approximately half of all Hershcel ATLAS galaxies have a reliable VIKING counterpart. I find that the fraction of Herschel sources with a reliable VIKING counterparts remains above 30% for Herschel sources at redshifts above z = 3, beyond the VIKING detection limit. We propose that this is the result of observing a large number of gravitationally lensed sources in the Herschel ATLAS survey. I match a sample of Herschel ATLAS sources to the optical Subaru Deep Field (SDF) catalogue, using radio data as an intermediary step to attain accurate positions. I compare this technique with matching Herschel ATLAS sources directly to the SDF catalogue and find that of the common matched sources, 6% of Herschel ATLAS sources are matched to two different SDF sources. I study the star forming properties of Herschel ATLAS and Herschel-GOODS galaxies. I study the two galaxy samples in terms of the galaxy main sequence, Kennicutt-Schmidt relation and the K magnitude-redshift relation. I find that the Herschel galaxies are relatively homogeneous. There is little evidence that the starburst phase of galaxies plays a large role in the star formation history of Herschel galaxies. I find that the star formation efficiency of our starburst galaxies is on average the same as main sequence galaxies, implying that starburst galaxies form more stars due an increased gas mass. The optical images of the Herschel-GOODS sample of galaxies are decomposed in to their bulge and disc components. I find that 67% feature a bulge which is best fit with a low Sersic index profile, suggesting the majority of the population feature a disc-like or pseudo-bulge. I see little evidence of a correlation between the properties of the bulge and the overall star forming properties of the galaxy.

IN this thesis I describe the development and validation of a generic time domain simulator of exoplanet transit spectroscopy called ExoSim, and apply it to various problems in the field. ExoSim models both the astrophysical scene and the optical system in an end-to-end simulation, outputting a time series of images akin to a real observation. The simulator was validated through a series of tests against predictions, alternate simulations and published data, showing it was accurate to within 5% of most comparisons. ExoSim modeled the Hubble Wide Field Camera 3 IR instrument, finding that scanning mode was superior to staring mode (38% less noise), with no significant excess noise. The results supported uncertainties in published studies for GJ 1214b. ExoSim was used in the ARIEL Phase A study, playing a key role in formulating and verifying an instrument design that was low risk and compatible with the science case of spectroscopically surveying 1000 exoplanets. Spectral jitter noise was found to be a feature of ARIEL observations, but using ExoSim it was shown this could be mitigated in data reduction without design level changes. ExoSim was used to quantify the uncertainties due to stellar variability on the transmission spectrum, finding that noise from pulsations and granulation is not significant in ARIEL observations. For spots, variations of +3.9 to -5.2% in contrast ratio were projected for GJ 1214b and +0.9 to -0.5% for HD209458b in the visual range, but in the mid-IR range variations fall well within the photon noise limit. ExoSim was used to simulate observations of the TRAPPIST-1 system, from which we found that ARIEL could characterise primordial H2-He atmospheres on all 7 planets, but that only planets b and h would be candidates for observing high molecular weight atmospheres. Overall, ExoSim was found to be a valuable tool applicable to diverse problems in the field of transit spectroscopy.

Photometric transit surveys on the ground & in space have detected thousands of transiting exoplanets, typically by analytically combining the signals from multiple transits. This technique of exoplanet detection was exploited in K2 to detect nearly 200 candidate planets, and extensive follow-up was able to confirm the planet K2-110b as a 2:6 0:1R , 16:7 3:2M planet on a 14d orbit around a K-dwarf. The ability to push beyond the time limit set by transit surveys to detect long-period transiting objects from a single eclipse was also studied. This was performed by developing a search technique to search for planets around bright stars in WASP and NGTS photometry, finding NGTS to be marginally better than WASP at detecting such planets with 4:14 0:16 per year compared to 1:43 0:15, and detecting many planet candidates for which follow-up is on-going. This search was then adapted to search for deep, long-duration eclipses in all WASP targets. The results of this survey are described in this thesis, as well as detailed results for the candidate PDS-110, a young T-Tauri star which exhibited 20d-long, 30%- deep eclipses in 2008 and 2011. Space-based photometers such as Kepler have the precision to identify small exoplanets and eclipsing binary candidates from only a single eclipse. K2, with its 75d campaign duration and high-precision photometry, is not only ideally suited to detect significant numbers of single-eclipsing objects, but also to characterise them from a single event. The Bayesian transit-fitting tool ("Namaste: An MCMC Analysis of Single Transit Exoplanets") was developed to extract planetary and orbital information from single transits, and was applied to 71 candidate events detected in K2 photometry. The techniques developed in this thesis are highly applicable to future transit surveys such as TESS & PLATO, which will be able to discover & characterise large numbers of long period planets in this way.

The Lyα forest is a series of absorption lines seen in quasar spectra and is a powerful tool for probing the thermal state of the intergalactic medium (IGM) across a wide redshift range. At intermediate redshifts (2< z <5), the statistical properties of the Lyα forest predicted by recent hydrodynamical simulations are in good agreement with a range of spectroscopic data. However, at lower and higher redshifts this is still not the case. Some of the key questions still challenging our understanding at low redshifts are the nature of absorbers, the evolution of the ultraviolet background and the impact of feedback from supernovae and active galactic nuclei (AGN). Furthermore, as a range of reionsation models remain unconstrained and the precise timing of reionsation remains elusive, high redshift Lyα forest data can provide valuable insight due to its sensitivity to the post-reionsation thermal properties of the IGM. At low redshift, this investigation focuses on understanding the effect of different feed-back prescriptions on the properties of the Lyα forest using simulations from the Sherwood simulation suite. The simulations incorporate three different prescriptions for treating cold dense gas and galactic feedback from supernovae and AGN. These implementations have only a small effect on the properties of the Lyα column density distribution function (CDDF) and Lyα line velocity width distribution. Therefore, feedback does not solve the discrepancy between the Cosmic Origins Spectrograph (COS) observations of the CDDF at z≃0.1 for high column density systems (NHI > 1014cm−2), as well as the line width distribution, which has lines broader then the simulation data. Some of the possible solutions may be feedback that ejects more overdense gas into the IGM, an increase in the temperature of the overdense gas (which is rather fine-tunedso that the gas is able to still contribute to the Lyα forest), or an unresolved turbulentin the IGM. The low redshift Lyα forest investigation is concluded by performing a series of numerical convergence tests on the quantities most widely employed in absorption line studies at low redshift. The mass resolution of the simulations can significantly impact on the estimated line velocity widths, by overestimating line widths for low mass resolution runs. By contrast, the Lyα CDDF is quite well converged for low column density absorbers. At higher redshifts, a feasibility analysis to constrain the thermal history of the IGM using cosmological hydrodynamical simulations of the Lyα forest is performed. This problem is approached by utilising the Lyα forest transmitted flux power spectrum at z∼5. The integrated heating during reionsation has a measurable impact on the power spectrum. The integrated heating is parameterised using the cumulative energy per proton deposited into a gas parcel at the mean background density. A Markov Chain Monte Carlo approach is used to recover the cumulative energy per proton with a statistical uncertainty of ∼ 20 per cent (at 68 per cent confidence interval), by making assumptions consistent with current observational data sets. However, systematics may increase the uncertainty to ∼ 30 per cent at these redshifts. This method can distinguish between early (z = 12) and late (z= 7) reionisation in the simulations. Finally, to expand on this investigation, the first constraints on the cumulative energy per proton using recent Lyα flux power spectrum measurements at high redshift are obtained. A consistent picture of galaxy driven reionsation with reionsation occurring at z∼9 is found.

A proposal for performing quantum memory schemes with a light matter interface in Hollow Core Fibres is introduced. Various technical aspects of implementing such a scheme in the proposed interface are outlined and the different elements required to realize this scheme are discussed, primarily the detection of atomic levels and the extension of the scheme to magnetically trappable levels. A new method to dispersively measure populations and population difference of alkali atoms prepared in their two clock states is introduced, for future use in the Hollow Core Fibre interface. The method essentially detects the atom numbers based on the influence of the linear birefringence in the ensemble on the detection light beams via polarization homodyning. Sideband detection is performed after dressing the atoms with a radio-frequency field to circumvent low-frequency technical noises. The noise performance of this scheme is discussed along with design modifications aimed at reaching the atomic shot noise limit. Another technical aspect of realizing the quantum memory scheme in the proposed light-matter interface is the extension of the scheme to the trappable states of the atomic system as the atoms will be trapped in an atom chip magnetic field. We achieve this extension by showing the microwave spectroscopy of the ground state ensemble of radio-frequency dressed atoms which proves the existence of pseudo one-photon transitions between the trappable clock states. Finally, the preliminary designs and results of integrating an HCF in an atom chip experiment are discussed.

The thesis presents millimetre (mm) and submm continuum imaging observations of the four, nearby active galaxies Cygnus A, NCC 4374, Centaurus A and M 82. These were undertaken using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope in Hawaii. The study focused on the properties of the cool to cold dust (~ 80 to 10K) and its associations with star formation and nuclear activity in the galaxies. The observations of Cygnus A constrained the galaxy's cold dust temperature between 37 and 85K, corresponding to dust masses between 1.0 x 10 8M® and 1.4 x 106M® respectively. Based on the dust spatial and mass limits, it is possible the heating of the cold dust in Cygnus A is dominated by high-energy nuclear activity or star formation. Detailed photometric observations of the core and two major hotspots (A and D) in Cygnus A showed that their mm to submm spectral indices extend smoothly to about 450μm (677GHz), with no evidence of spectral steepening. The results allow tight determinations for model parameters of synchrotron electron lifetimes in these components. In pilot survey observations of the elliptical galaxy NGC 4374, a mass upper-limit Of ~ 2 x 107M® (i.e. comparable to the dust contents of luminous spiral galaxies) was placed on the diffuse dust that, if it exists, would affect colour and metallicity studies of elliptical galaxies. Following the pilot observations, a strategy was devised to select a good sample of ellipticals in which to search for this low-level, very cold dust. For the first time ever, the observations of Centaurus A delineated the galaxy's submm unresolved core, an inner-jet interacting with gas in the dust lane, and extended emission from multi-temperature cold dust at ~ 40, 30 and 12K. Also for the first time ever, a submm high surface brightness ringed, spiral structure of radii ~ 90", that coincides with the regions of intense star formation and mid-infrared continuum, was revealed in the optical dust-lane, confirming predictions by a geometric warped disc model consisting of tilted rings. From the spatial associations in the galaxy, star formation seems to dominate at lease 50% of the heating of the cold dust, while the rest appears to be heated by diluted stellar radiation. In M82, the 850μm continuum has been detected out to 1.5kpc, at least 10% farther in radius than previous detections in this starburst galaxy. The overall submm morphology and nuclear spectral index distribution have a general north-south asymmetry similar to that of H. and X-ray winds, supporting the association of the extended continuum with outflows of dust grains from the nucleus into the halo. The work of M 82 raises many interesting points about the origin and structure of the submm emission, however the results are displayed here still under investigation and therefore are rather preliminary. In short, the submm continuum observations of Cygnus A, NGC 4374, CentaurusA and M 82 are presented in this thesis that constrain the physical properties of cold dust in these active galaxies and elucidate the associations of the dust with star formation, nuclear activity and stellar components in these galaxies in particular, and other similar galaxies in general.

This thesis presents an examination of a range of dynamic phenomena present throughout the solar atmosphere, from the photosphere to the corona. Above the photosphere, where the plasma fi is small, the emitting plasma structure and dynamics are tied intimately to the solar magnetic field. Firstly, a wavelet analysis is applied to multi-temperature spectroscopic data observing network-internetwork regions across a coronal hole boundary region. The nature of quasiperiodic variability is investigated through the different temperature lines across the observed structures. Statistically significant periods are found within the range 100-900 seconds, along with short period wavepackets with periods 50-100 seconds. These oscillations are discussed in terms of possible wave mechanisms. An example of a time-dependent period is observed above the network region on the coronal hole boundary and possible theoretical origins are discussed. Secondly, a detailed analysis is applied to an active region observed on the solar limb. A dynamic transition region loop, and closely associated ejection event are observed within the active region. These structures are characterised by their emission line profiles; the transition region loop is found to have a flow geometry of -20---*40 km c 1 , and the ejection event is found to have a velocity gradient up to -20—*50 km across its width, suggesting a rotating transition region structure consistent with a macrospicule. Thirdly, an upwardly propagating disturbance is observed along a coronal loop associated with a plage region with a velocity 50-195 km s perpendicular to the line of sight, and period of 5 minutes. A wavelet analysis reveals that the five minute period is present in co-spatial, co-temporal chromospheric and transition region observations. This is interpreted as the first observation of a 5-mm p-mode propagating through the chromosphere, transition region and into a coronal loop. Fourthly, an observing campaign is designed and executed to probe the connectivity between the chromosphere, transition region and corona within active regions. Oscillations within the 3-min band are observed above the umbra of a sunspot active region. These oscillations show two closely separated frequencies of 6.1 & 7.1 mHz in the chromosphere, 5.9 & 7.3 mHz in the transition region and 5.9 & 7.3 mHz in the corona. These observations are interpreted as acoustic/maneto-acoustic wave modes propagating upwards through the chromosphere, transition region and into the corona. The frequencies are observed as oscillations in the chromosphere and transition region, and propagations in the emerging coronal loops, due to the combined effect of the temperature scale height in the different spectral lines and the diverging magnetic flux geometry above the sunspot. The energy flux of acoustic waves is estimated in the different temperature lines as 28.3 erg cm 2 in the chromosphere, 201.0 erg cm2 sin the transition region and 225.6 erg cm 2 in the corona. Finally, future work is discussed in terms of progressing the work completed, and exploiting upcoming spaced based missions.