Impact cratering and asteroid collisions are major processes throughout the Solar System. Although previous collision-related impact investigations exist (Flynn et al. 2015, Holsapple et al. 2002 and Burchell et al. 1998 are good examples), in the works covering this broad range of investigation, the targets are non-rotating (for the purposes of catastrophic disruption) and different temperature conditions are not considered (for impact cratering). Accordingly, I present experimental processes and data, regarding hypervelocity impact experiments into analogues of (1) rotating asteroids and (2) temperature dependant terrestrial planetary rock. During the course of this work, it was necessary to develop new apparatus and new experimental techniques such as three separate target holders to aid in both catastrophic disruption and heated impact projects, a 3-dimensional model analysis of craters and a completely new, statistically robust, technique to determine a complete crater profile called the KDM method where KDM is Kinnear-Deller-Morris. The main result from this work showed that during an asteroid impact collision where the asteroid is not rotating, the impact energy density for catastrophic disruption is Q*static = 1442 ± 90 J kg-1. However, when the target asteroid was rotating, the condition Q*rotation = 1097 ± 296 J kg-1. The mean value of Q* had thus reduced, but the spread in the data on individual experiments was larger. This leads to two conclusions. The mean value for Q*, based on measurements of many impacts, falls, due to the internal forces acting in the body which are associated with the rotation. This energy term reduction means that the amount of energy to instigate catastrophic disruption is lower and that a rotating asteroid is effectively weaker upon impact than a stationary asteroid. However, the spread in the results indicates that this is not a uniform process, and an individual result for Q* for a rotating or spinning target may be spread over a large range. For the temperature related impacts, as the targets were heated to approximately 1000 K, the target rocks showed an impact dependence more similar to a plastic phase-state than to solidus, due to being held close to temperatures associated with semi-plastic phases. Basalt impact craters displayed this relationship greatest with crater sizes becoming smaller at the higher temperature ranges but larger in the colder brittle solidus temperatures, partly explained in experiments by increased spallation.

Globular clusters were among the first luminous objects to form in the Universe. They are dense collections of hundreds of thousands of stars. Globular cluster formation is a major unsolved problem in astrophysics. A new constraint on the problem came from the discovery of unexpected star-to-star variations in the abundances of some light elements. These abundance variations (or multiple stellar populations) are ubiquitous to all globular clusters studied to date. The pursuit to explain this longstanding prob- lem using these new constraints (i.e. the abundance variations), has reinvigorated the study of globular clusters, and at the same time has challenged our understanding of nucleosynthesis and stellar evolution. Several scenarios have been put forward to explain the presence of multiple stellar populations in globular clusters, nearly all requiring multiple generations of stars. The basic hypothesis in these models is that a second generation of stars is born during the early life of the globular cluster from the chemically-processed ejecta of some first generation stars in order to account for the signature multiple stellar populations observed in old globular clusters today. Many of these scenarios are mutually exclusive. Therefore, to determine which of them fits the current evidence the best became the priority of globular cluster studies. Modern observational facilities cannot resolve the globular cluster formation process in the early Universe. However, none of the scenarios for the origin of globular cluster and their multiple stellar populations make any distinctions between star/cluster formation at the present day and earlier epochs of the universe. Accordingly, the processes invoked in these scenarios can, in principle, be constrained by studies of the formation of young massive star clusters in the local Universe, which have similar sizes and masses as present-day globular clusters, but are significantly younger. In this work, I present some of the strongest constraints from such studies coming from the gas content of young massive clusters and their star formation histories. These studies showed that: 1) young massive clusters are consistent with a single star formation burst, and 2) there is no significant cool gas reservoirs left within young massive clusters that can fuel future star-formation events. These results are in stark contrast with the predictions of nearly all the scenarios that have been proposed to explain the origin of abundance variations in globular cluster stars, which require that young massive clusters should host multiple star formation events.

Radio galaxies with extended lobes are believed to interact strongly with their environment. In this thesis, I investigate the evolution of radio galaxies with different properties and track them through the cosmological ages. In Chapters 2 and 3, I perform a ”Monte-Carlo-based” population synthesis study which combines a model for the luminosity evolution of an individual FRII source with the radio luminosity function as a function of redshift. The artificial samples generated are then compared with complete observational samples. The results show that the properties of FRII sources are required to evolve with redshift. I also study the distribution of the jet properties as a function of redshift. From currently available data it is not possible to constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately -2. This power-law slope does not change with redshift out to z = 0.6. I also find the distribution of the pressure in the lobes of FRII sources to evolve with redshift up to z ∼ 1.2. FRI sources are not yet considered in Chapter 3, as existing analytical models for FRI soures are less successful. Thus in Chapters 4, I present a new analytical model for FRI jets. The model is based on a mixing-layer structure in which an initially laminar, relativistic flow is surrounded by a shear layer. I apply the appropriate conservation laws to constrain the jet parameters, starting the model where the radio emission is observed to brighten abruptly. Applying the model to a sample of the well-observed FRI sources, including example 3C 31, I find a self-consistent solution, from which I derive the jet power together with other properties like the entrainment rate. The model in Chapter 4 leads an idea of estimating the maximum lengths and ages of the FR II sources by considering the entrainment process during their evolutions. In Chapter 5, I consider the laminar part of the jet may be destroyed due to the entrainment under certain assumpsions, in which case the radio outflows cease to be FR IIs after a few 10 8 yrs, at which point they have typically reached sizes of around 1 Mpc. Based on this idea, I then further discuss a plausible transition process from FRIIs into FRIs.

High-mass X-ray binaries (HMXBs) have proved to be some of the most interesting X-ray sources in the sky. The growing opulation of Small Magellanic Cloud (SMC) Be/X-ray binaries is monitored weekly with two 15ks RXTE observations. My thesis focuses on presenting the analysis of the X-ray data and the optical follow-up that enhances it. I present detailed studies of the H emission features in several prominent Be/X-ray inaries in the SMC and examine their outbursting nature by combining the OGLE optical light curves with the RXTE light curves. This has culminated in an orbital solution for SXP18.3 as well as measured orbital periods for SXP2.37, SXP172 and SXP202B. Through detections of quasi-periodic variations in the optical light curves, the details of interactions taking place between the Be star’s circumstellar disk and the neutron star are being revealed. These data are providing the building blocks that may help explain the physical processes that produce the circumstellar disk. In addition, the optical counterpart to SXP15.3 is discussed in the light of recent XMM-Newton results, raising doubt over the true optical counterpart.

Within this thesis are discussed two main topics of contemporary astrophysics. The first is that of machine learning algorithms for astronomy whilst the second is that of magnetic cataclysmic variables (mCVs). To begin, an overview is given of ISINA: INTEGRAL Scouce Identifiction Network Algorithm. This machine learning algorithm, using random forests, is applied to the IBIS/ISGRI data set in order to ease the production of unbiased future soft gamma-ray source catalogues. The feature extraction process on an initial candidate list is described together with feature merging. Three trainng and testing sets are created in order to deal with the diverse time-scales encountered when dealing with the gamma-ray sky: one dealing with faint persistent source recognition, one dealing with strong persistent sources and a final one dealing with transients. For the latter, a new transient detection technique is introduced and described: the transient matrix. Finally the performance of the network is assessed and discussed using the testing set and some illustrative source examples. ISINA is also compared to the more conventional approach of visual inspection. Next mCVs are discussed, and in particular the properties arising from a hard X-ray selected sample which has proven remarkably efficient in detecting intermediate polars and asynchronous polars, two of the rarest type of cataclysmic variables (CVs). This thesis focuses particularly on the link between hard X-ray properties and spin/orbital periods. To this end, a new sample of these objects is constructed by cross-corelating candidate sources detected in INTEGRAL/IBIS observations against catalogues of known CVs. Also included in the analysis are hard X-ray Observations from Swift/BAT and SUZAKU/HXD in order to make the study more complete. It is found that most hard X-ray detected mCVs have Pspin/Porb<0.1 above the period gap. In this respect, attention is given to the very low number of detected systems in any ban between Pspin/Porb = 0.3 and Pspin/Porb = 1 and the apparent peak of the Pspin/Porb distribution at about 0.1. The observational features of the Pspin - Porb plane are discussed in the context of mCV evolution scenarios. Also presented is evidence for correlations between hard X-ray spectral hardness and Pspin, Porb and Pspin/Porb. An attempt to explain the observed correlations is made in th context of mCV evolution and accretion footpring geometrirs on the whit dwarf surface.

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.

A custom made five panel filter mosaic window was designed, installed and operated with the HiTIES (High Throughput Imaging Echelle Spectrograph) at the Nordlysstasjonen in Svalbard, Norway (78.2025N and 15.829E). The filter provides images of the resonant scattered spectra of N+ 2 1N (0,1), (1,2), (2,3) bands and a neutral N2 2P (0,3) band. Ab initio models were created for describing the populations of vibrational and rotational energy levels in both excited and ionised N2 molecules in the ionosphere. In the rotational profiles the species are treated to be in thermal equilibrium, whereas the vibrational levels assume a non-thermal steady state time independent model. Rotational temperatures were evaluated for different auroral forms for the N+ 2 (0,2) band from the magnetic zenith and along the meridian slit in HiTIES data from winter. A clear trend in neutral temperature is found, with higher values for times of lower energy precipitation. The relationship between resonant scattering of solar photons via N+ 2 and direct emission from electron impact on N2 was evaluated qualitatively and quantitatively with HiTIES data from January-March 2007. A relationship was found that clearly indicates the emission profiles are a function of primary electron energy and solar shadow height when auroral arcs are partially sunlit during events of electron precipitation.

High Mass X-ray Binaries (HMXBs) represent an important stage in the evolution of massive stars and are some of the brightest sources in the X-ray sky. In the first half of this thesis a detailed analysis of X-ray observations of two HMXBs, the Be/X-ray Binary (BeXRB) Swift J045106.8-694803 and the supergiant/X-ray Binary XTE J0421+560/CI Camelopardalis, is presented. Simulations of the X-ray spectrum of Swift J045106.8-694803 show that both the spectral and timing properties can be reproduced by a blackbody and power law pulsating ∼ pi out of phase with each other. The pulse profile of the blackbody is used to determine the angle between the rotation and magnetic axes of the neutron star and the angle between the rotation axis and line of sight. The apparently broad iron line of XTE J0421+560 is decomposed into three intrinsically narrow lines, FeI-Ka, FeIK b and FeXXIV-XXVKa. The light curve extracted in the energy range defined as the Fe-Ka line from the spectral fits shows marginal evidence for a lag when cross correlated with that of the continuum. The lag is interpreted as the light crossing time of the circumbinary torus and implies a radius of 10 AU. The second part of this thesis considers HMXBs as a population. I describe the search for XRBs in the Phoenix dwarf galaxy, a Local Group dwarf irregular galaxy which share many similarities with the Small Magellanic Cloud (SMC), which has an apparent overabundance of HMXBs. Finally, I discuss why the BeXRB population in the SMC is ideal for population studies and outline the work done to search for evidence for two different neutron star formation channels in their physical parameters

The X-ray emission from accreting black holes provides the perfect probe for testing the geometry, behaviour and conditions present in the innermost regions of the accretion flow. In this thesis I use X-ray spectral analysis to investigate the properties of accreting black holes that extend over several orders of magnitude in accretion rate (m˙ E) and black hole mass (MBH), from the stellar mass black holes in X-ray binary systems (XRBs)to the supermassive black holes in active galactic nuclei(AGN). Firstly, through a survey of X-ray emission in the nuclei of nearby galaxies I show that the usefulness of the X-ray to optical line ratios as a Compton-thick diagnostic does not extend to low luminosity AGN, and instead these ratios may have more practical use in distinguishing between AGN and non-AGN emission processes. Secondly, and more importantly, the main focus of this thesis is upon the variability of the Comptonised power-law X-ray spectral component, and more specifically an examination of how the photon index

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