Bent tail radio sources (BTRSs) are radio galaxies which have jets that show a characteristic C‐shape that is believed to be due to ram pressure caused by the motion of the galaxy through the ambient medium. They are generally found in galaxy clusters in the local Universe. They have already been used in observations as tracers of galaxy clusters at redshifts of up to z _ 1. They have, however, been shown to be numerous in galaxy groups as well. The ability to find high redshift galaxy clusters is important in cosmology because they are important cosmological probes. According to the _ CDM model, galaxy clusters form around redshift of z _ 2 and finding clusters of halo mass greater than 1014 M_ at redshift greater than z = 2:5 would disprove the current concordance model. Finding galaxy clusters at those redshifts is more feasible with the new generation of radio telescopes and the upcoming square kilometer array (SKA). In this work we look at some SMBH mass measurements, which are crucial in the determination of the correlations between the SMBH mass and some galaxy characteristics including jet length and luminosity. The high redshift SMBH mass measurement methods are calibrated using local Universe correlations. This makes SMBH mass measurement an important aspect in the study of high redshift radio galaxies and hence BTRSs. We use cosmological simulations from the MareNostrum Universe simulation to look at the efficacy of using BTRSs as tracers of clusters assuming the ram pressure is the cause of the jet bending. This is the first step in predicting the possible number of BTRSs that we may observe with the SKA. We find that SMBH masses can be measured up to redshift of z = 4:5 using the virial mass estimator method. The BTRSs are equally likely to be found in galaxy clusters and galaxy groups in the local Universe. This means that around 50% of the BTRSs that we are likely to find at high redshift will be in galaxy clusters. However, finding a pair of BTRSs in close proximity is a sign of a galaxy cluster environment. These results are still dependent on the resolution of degeneracies in our understanding of the duty cycles of AGN radio jets, projection effects of the radio jets, the environmental dependence of radio‐loudness in galaxies and other open questions.

I have conducted a systematic survey of eleven nearby novalike cataclysmic variables in the radio band, using the MeerKAT radio interferometer. Radio emission is detected from four out of the eleven systems: IM Eri, RW Sex, V3885 Sgr and V603 Aql. While RW Sex, V3885 Sgr and V603 Aql had been previously detected, this is the first reported radio detection of IM Eri. These observations have doubled the sample of non-magnetic cataclysmic varaibles with sensitive radio data. I observe that at these radio detection limits, a specific optical luminosity & 2.2 × 1018 erg s−1 Hz−1 (corresponding to MV . 6.0) is required to produce a radio detection. I also find that the X-ray and radio luminosities of the detected novalikes are on an extension of the LX ∝ L ∼0.7 R power law originally proposed for non-pulsating neutron star low-mass X-ray binaries. No other correlations are found between the radio emission and emission in other wavebands or any other system parameters for the existing sample of radio-detected novalikes. In-band (0.9–1.7 GHz) radio spectral indices are measured, and are found to be consistent with reports from earlier work. I construct broad spectral energy distributions for this sample from published multi-wavelength data, and use them to place constraints on the mass transfer rates of these eleven systems. Finally, I also present the results of time-resolved optical spectroscopy of two little-studied systems in the sample: V5662 Sgr and LSIV -08 3. I obtain orbital periods for these two systems that are consistent with previous measurements in the literature.

We aim to characterise the X-ray binary population as a function of the local stellar population (in terms of age, metallicity, and stellar density) in the Magellanic Bridge, the interconnecting region between the Small and Large Magellanic Cloud. Gardiner and Noguchi (1996) suggest that closest approach between Small and Large Magellanic Cloud, as evidenced by dramatic phase shift in star formation, occurred approximately 200 Myr ago. During the approach, gas had been tidally stripped (most likely from the Small Magellanic Cloud) into the interconnecting Bridge. According to models of star formation history (Harris, 2007), alongside optical surveys of the Bridge (Skowron et al., 2014), there is strong evidence to suggest that the young, low metallicity stellar population formed in situ, rather than being tidally stripped from either Magellanic Cloud. Three fields located near the Western Bridge observed by Harris (2007) were also observed with the XMMNewton. Cross-matching between optical and X-ray sources was performed, and any interesting matches were followed up with spectroscopic analysis, using the 1.9 m telescope located in Sutherland. A Be/X-ray Binary (BeXRB) candidate is discussed, and if confirmed, will be the furthest known BeXRB from the SMC.

Bibliography: pages 136-138. / The design and construction of an astronomical polarimeter is described and an evaluation made of its performance. Extensive observations of cataclysmic variables with emphasis on the AM Her and DQ Her classes are then presented. After consideration of the basic principles involved in the development of an efficient and accurate polarimeter, a design using two super-achromatic retarders (a 1/4 wave and a 1/2 wave) rotating above a fixed analyser was adopted. This permitted simultaneous linear and circular polarisation measurements, or, by rearranging the order of the retarders in the beam, linear polarisation measurements alone, or circular polarisation measurements alone, with enhanced efficiency. The polarimeter was found to have extremely low instrumental polarisations and, because of the superachromatic retarders used, the efficiency correction factors were very close to 1 at all wavelengths. The polarisations are calculated at the telescope and the light curve at a higher time resolution may also be recorded if this is required. Extensive sets of observations using the polarimeter were obtained for six of the ten AM Her variables (or "polars"). EF Eri and El405-451 were observed most. Evidence was found in El405-451 for movement of the apparent location of the accretion region on the primary star and the inclination and magnetic dipole off set from the rotation axis was determined. This allowed a comparison to be made between the competing models for the cyclotron emission, showing that those which take into account the temperature structure of the accretion region provide the best results. Observations and an analysis of the polarisation data from H0139-68, E2003+225, VV Puppis and PG1550+191 are also presented in some detail. A final chapter presents results from observations made to detect a modulation in the polarisation at the rotation period of the primary in the DQ Her variables. Upper limits are set for 4 members of the class and the implications of the results are discussed.

No description available.

Includes abstract / Includes bibliographical references. / Long-term variability in all types of X-ray binaries is a well established characteristic, but due to observation limitations and lack of long-term monitoring capability these variations have not been studied before in a systematic way. In this thesis, we exploit the ~ 16 yr optical light curves from the MACHO and OGLE databases, and combine these with archival XMM-Newton X-ray observations to study the long-term properties of Be/X-ray binaries and Supersoft X-ray Sources in the Magellanic Clouds.

The six chapters of this thesis contain the results of four years spent in the investigation of old open clusters at the SAAO. Each chapter is a preprint of a paper which has been submitted or accepted for publication and is therefore an independent entity with its own list of acknowledgements and references. Since each chapter is intelligible without continual reference to its fellow chapters, considerable overlap has sometimes occurred. As a thesis, the end product is of necessity a little disjointed. This approach has been adopted because 'the publication of the results has higher priority than the presentation of a thesis. The style is as compact as seems consistent with reasonable clarity and I hope that reading it will not present too great a problem of digestion to those interested in the evolution of solar-type stars.

Includes bibliographical references. / This thesis is based on the Edinburgh-Gape Blue Object Survey and includes a general review of blue star sky surveys, a detailed discussion of the selection techniques, the present status of the survey, and follow-up photometry and spectroscopy of the cataclysmic variable stars (GVs) found by the survey. Because of the north-south imbalance in the number of blue objects, the Edinburgh-Gape Blue Object survey was designed to discover previously unknown blue objects with B≤~18 at high galactic latitude in the southern hemisphere. At present, all the planned fields (61 fields) in the North Galactic Pole region and 26 fields in the South Galactic Pole regions are complete, covering 2488 square degrees. The preliminary results show that the survey has an internal completeness of ~94% for objects with U-B bluer than the cutoff --0.3, and selects objects with an accuracy in photographic U-B of 0.16 mag. UBV measurements and spectra have been obtained for ~2000 objects. Half of these objects are hot subdwarfs which comprise the sdO, sdB, and sdOB stars. The white dwarfs account for about 17% of the total. About 18% of the objects are horizontal branch B and normal B stars. Cataclysmic variable stars and quasars comprise only a small fraction, 2 and 6 percent, respectively. Less than one percent are galaxies. The remaining ~5% have unknown spectral classes at present. So far, 25 cataclysmic variable stars have been found by the survey. The space density was estimated to be 1.6xl0-⁶ pc-³. Among these cataclysmic variables, 6 dwarf novae and 8 nova-like variables are new discoveries; detailed study of their photometric and spectroscopic characteristics are discussed in Chapters 6-10. One of the stars discovered, a close binary with large reflection effect, is a predecessor of the cataclysmic variables. Napier's (1968) method for the reflection effect in close binaries was used to model the light curve in order to solve for the physical properties of the system. Photometry, spectroscopy, and model fits for this system are discussed in Chapter 5.

Context: Stellar population modelling is a popular technique that has been extensively applied to main sequence galaxies. Yet starburst galaxies and Luminous InfraRed Galaxies (LIRGs) have, so far, not been studied as much using the method. LIRGs in the local universe are known to be highly interacting galaxies with strong star formation in obscured environments. Still, LIRGs also have diversity in terms of morphology and mode and location of star formation. Aim: This thesis investigates the stellar population properties of a group of 52 starbursts and luminous infrared galaxies (LIRGs) in the local universe that forms part of the SUperNovae and starBurst in the InfraReD (SUNBIRD) survey. The galaxies in a distance range of 3.5 < Dl < 280 Mpc and infrared luminosity of 10.30 < LIR < 11.91 L were observed with the Southern African Large Telescope in long-slit spectroscopy mode. Method: The stellar populations of the galaxies are derived by fitting Bruzual &amp; Charlot (2003) templates to the reduced spectra using STARLIGHT software with a Monte Carlo method implemented to recover uncertainties on age, metallicity and extinction. The derived stellar population models are then subtracted from the observed spectra to produce emission spectra from which emission line fluxes are measured. Both integrated spectra and spatially resolved apertures are extracted to be analysed in this work. Results: The light-weighted and mass weighted age of the sample is found to be 160 Myr and 7.2 Gyr respectively. The star formation history of the sample shows a rise of activity in the past ∼ 50 Myr and with a jump of an order of magnitude in the past 3 Myr. Analysis of the stellar metallicity hints at inflow of pristine gas, which decreases the observed metallicity content as well as ignites SF-activity. Analysis of the oxygen abundances shows that while LIRGs and SF galaxies are under abundant, their under-abundance may have previously been over-estimated as compared to main sequence galaxies. The radial age profile of the sample is flat, similar to that of late-type Sd galaxies. Interaction is found to cause a drop in the age of apertures although the post-merging stages shows continued star forming activity in the nuclear region. The stellar metallicity gradient is found to be −0.029 ± 0.018 dex/kpc, comparable to Sb or Sbc galaxies favouring an inside-out formation scenario for the galaxies. As interaction stage increases, both age and metallicity gradients are seen to get flatter, eventually getting slightly positive. The more active interaction stages are HII driven, while isolated and post merging stages shows higher AGN activity. The current work offers an update on the abundances of IR dominated galaxies from the previous work done by Rupke et al. (2008). The formation scenario of our LIRGs in the local universe is shown to be in line with the scenario put forward by Hopkins et al. (2008). Future works with medium resolution spectra acquired during the course of this thesis should allow for detection of gas inflows and better constrain the different ionising mechanisms involved at different interaction stages.

Includes bibliographical references (p. 233-242). / This thesis presents the results of a detailed multi-wavelength study of the nearby blue compact dwarf galaxies NGC 2915 and NGC 1705. The primary data set (nearly 100 hours of on-source data) for each galaxy consists of new observations of the neutral hydrogen (Hi) line obtained with the Australia Telescope Compact Array, October 2006 - May 2007. The stellar disk of NGC 1705 is host to an intense star-bursting core which is rapidly depleting the galaxy's central Hi reservoir. This galaxy can be used to rigorously test theories of star formation. Detailed studies of the distribution and kinematics of the neutral inter- stellar medium (ISM) within each galaxy are carried out. A suite of star formation recipes and models are examined for each galaxy to quantify the relationship between the observed star formation activity and the distribution and kinematics of the ISM.