Includes abstract. / Includes bibliographical references. / This thesis presents a deep optical galaxy catalogue of the Vela region in the Zone of Avoidance (I b < 10°.245 < I < 280. This region was searched for galaxy candidates by optical inspection of IIIaJ (3950 A to 5400 A) film copies of the ESO/SRC sky survey as part of an effort to reduce the ZoA.

Includes bibliographical references (p. 71-75). / NGC 6822, a Local Group dwarf irregular galaxy, was observed in the nearinfrared JHKS bands using the Japanese-SAAO Infrared Survey Facility (IRSF) telescope over a period of about four years. An extensive search for large amplitude asymptotic giant branch variables over the observed 7.5' x 21.1' area of NGC 6822 found 162 probable variables. In particular, 30 Miras and 9 semiregulars have been identified and characterised.

The lenticular (S0) galaxies introduced by Hubble (1936) as a morphological transition class between elliptical and early-type spiral galaxies, which have the most massive bulges among disk galaxies, may have formed in several different ways as suggested by theoretical and numerical simulation studies. A sample of lenticular galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G) using the Spitzer Space Telescope along with Sloan Digital Sky Survey (SDSS) was used for this project to study molecular gas properties as well morphologies associated with dust where molecular gas is present. A variety of image processing techniques are employed to study the details of galaxies to uncover the presence of molecular gas in S0 galaxies. We obtained colour maps using 3:6 and 4:5 micron images and SDSS r and i band images to find these galaxies have sufficient amount of dust and molecular gas along with variety of dust morphologies. In this thesis, we have shown, for the first time that the mass of molecular gas obtained by Carbon Monoxide (CO) is correlated to colour excess measured from (r - 3:6) and (i - 4:5) colour maps. It would be important to study this relation using advance facilities such as ALMA and MeerKAT to explore properties of molecular gas in nearby early-type galaxies in detail.

Includes abstract. Includes bibliographical references (leaves 105-110).

Includes bibliographical references. / Galaxy clusters can be sites of considerable dynamic activity due to intra-cluster and inter-cluster interactions. These interactions include cluster-cluster mergers which are accompanied by large release of energy observed via thermal X-ray emission. The work presented here focuses on clusters that exhibit extended radio sources called radio relics and radio halos. The relics tend to be found in the peripheral regions of galaxy clusters while halos tend to be located at the central regions. These two types of sources share many of their characteristics but some of their key difference is radio polarization: relics tend to have polarised emission while halos do not. The observed polarisations and the non-thermal nature of the emission of these sources suggests the existence of large scale magnetic fields which permeate galaxy cluster volumes. Investigations into relic and halo sources may shed light into the formation of galaxy clusters and how they evolve. A way of analysing the evolution of clusters is to investigate the evolutionary state of their galaxy populations. This work aims to both characterise galaxy membership and probe galaxy evolution in these clusters through a spatial, kinematic and photometric analysis.

Since 1974, when the Glass standards were published, four other infrared groups have been set up at the other main southern observatories, i.e. the two Australian observatories, Mount Stromlo and Siding Spring Observatory CMSO) and Anglo-Australian Observatory (AAO) and the two observatories in Chile, European Southern Observatory (ESO) and the Cerro Tololo Inter-American Observatory (which uses the California Institute of Technology standard system) (CIT). Unfortunately there has been a serious lack of conformity. Each group has used a different set of filters and has different zero points. No standards are common to all the groups and only a few are in common between any of the systems. Several transformat1ons between the various systems have recently been published (Elias et al 1983 and Glass 1983) but the large errors in the transformation equations show the need for more accurate standard stars. Therefore, on the surface, the introduction by us of a new set of standards would appear in danger of adding confusion to the issue, but this is not, in fact, the case. Firstly, the new set is basically the same system as tha Glass standards but with greatly increased accuracy. Secondly, the work involved has shown up several anomalies and inaccuracies in other systems. Thirdly, this work has shown why such large errors are apparent when comparing the various sets of standards and where the causes probably lie. The observations for these new standards were started in August 1979. The standards were introduced at the SAAO at the beginning of March 1984. The set is likely to evolve with time, increase in number of stars and improve in accuracy.

Includes abstract. / Includes bibliographical references (leaves 86-90). / We report on a study of super star cluster (SSC) candidates in the star-forming regions of a representative sample of local luminous infrared galaxies (LIRGs) using KS-band near-infrared (NIR) adaptive optics imaging with GEMINI/ALTAIR and VLT/NACO instruments. The evolution of the cosmic star formation rate (CSFR) indicates its rapid decline in the local Universe.

abstract: The 78 secondary eclipse depths for a sample of 36 transiting hot Jupiters observed at 3.6- and 4.5 μm using the Spitzer Space Telescope is here reported. Eclipse results for 27 of these planets are new and include highly irradiated worlds such as KELT-7b (Kilodegree Extremely Little Telescope), WASP-87b (Wide Angle Search for Planets), WASP-76b, and WASP-64b, and important targets for the James Webb Space Telescope (JWST) such as WASP-62b. WASP-62b is found to have a slightly eccentric orbit (ecosω=0.00614±0.00058), and the eccentricities of HAT-P-13b (Hungarian Automated Telescope Project) and WASP-14b are confirmed. The remainder are individually consistent with circular orbits, but there is statistical evidence for eccentricity increasing with orbital period in this range from 1 to 5 days. Day-side brightness temperatures (Tb) for the planets yield information on albedo and heat redistribution, following Cowan and Agol (2011). Planets having maximum day side temperatures exceeding ∼2200 K are consistent with zero albedo and distribution of stellar irradiance uniformly over the day-side hemisphere. The most intriguing result is a detection of a systematic difference between the emergent spectra of these hot Jupiters as compared to blackbodies. The ratio of observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with equilibrium temperature by 98±26 parts-per-million per Kelvin, over the entire temperature range in the sample (800K to 2500K). No existing model predicts this trend over such a large range of temperature. This may be due to a structural difference in the atmospheric temperature profile between the real planetary atmospheres as compared to models. / Dissertation/Thesis / Masters Thesis Geological Sciences 2019

This thesis records a detailed examination of the impact of the merger-pair galaxy environment on both the neutral hydrogen (Hi ) and mid-infrared (MIR) properties of galaxies in the nearby Universe. Making use of publicly available Hi profiles from the ALFALFA survey I construct the first statistically significant samples of close-pair galaxies (348 Hi -optical and 282 Hi - Hi pairs), and contrast their Hi content and star formation (SF) properties with a statistically significant Hisub-sample of isolated galaxies (544 galaxies) from the AMIGA project (Analysis of the interstellar Medium in Isolated GAlaxies; Verdes-Montenegro et al. (2005)). I present the first study of pairs using WISE data, and specifically examine their location on the MIR star-formation rate-stellar mass sequence (SFR-M★), or star-forming main sequence (SFMS), as a way to study how the close-pair environment influences the build up of galaxy stellar mass via SF. I also present the first MIR SFMS for isolated galaxies from the AMIGA catalogue to serve as the precedent for secular evolution. I derive an Hi scaling relation for isolated galaxies using WISE stellar masses, and thereby establish a baseline predictor of Hi content that can be used to assess the impact of environment on Hi content when compared with samples of galaxies in different environments. I use this updated relation to determine the Hi deficiency of both my paired and isolated galaxies, and invoke galaxy morphology (visual and MIR bulge-to-total ratios), the AMIGA isolation parameters 휂 (local number density) and Q (tidal influence), star formation efficiency (SFE), and Hi profile asymmetries to more closely inspect how these properties might be additionally driving the observed differences between the deficiency distributions of these two samples, as well as SFMS location. I also provide an analysis of the quantified Hi profile asymmetries of my pair and isolated galaxy samples, exploring not only the prevalence of asymmetry in Hi profiles, but also the possibility of using Hi profile asymmetries to trace merger activity. I find enhanced profile asymmetries in my pair sample, and propose that high profile asymmetries may be used to infer merger activity/identify close galaxy pairs at high redshifts, in lieu of the typically used 2D Hi maps we have for galaxies at low and intermediate redshifts, which are currently still limited. What my thesis shows is that although we have a plethora of data available (and coming), the key is to optimise how we use it, both in the questions we pose, and in understanding its limitations. We currently have large data-sets of Hi profiles in the local Universe, which, when incorporated into a cohesive multi- wavelength study, provide important clues as to how Hi forms, influences, and is processed in galaxies. These are the studies informing our theories for galaxy evolution, providing the incentive for superior telescopes (e.g. SKA), and ultimately guiding our decision-making in how to proceed in our ongoing endeavour to understand our Universe.

The environment in which a galaxy resides has long been known to have an impact on how the galaxy evolves. The denser the environment, the stronger the influence. Clusters of galaxies, which are some of the densest known cosmic environments, provide a unique opportunity to study the ongoing environmental processes influencing galaxy evolution. Optical studies have shown that galaxy clusters are typically home to a higher fraction of older elliptical, bulgedominated galaxies than the field which has a higher fraction of younger, disk-dominated galaxies. Which environmental processes are the cause of this morphology-density relation is still unknown. The dominant processes at play in the cluster environment tend to strongly impact the neutral hydrogen (H i) gas disks of galaxies. The H i disk often extends far out beyond the stellar disk making it susceptible to environmental processes before the stellar component of the galaxy is affected, and thus a useful tracer of the environment-driven galaxy evolution. In this thesis I study how the ongoing environmental processes in two galaxy clusters, the Coma cluster and Abell 2626, affect the average H i content of galaxies of different morphologies in different local environments or substructure. In the analysis of both clusters, I primarily use the H i stacking technique which uses the optical position and redshift information to extract global H i profiles of galaxies that are not necessarily directly detected in H i. The global profiles are aligned using the redshifts, and co-added to create an average H i spectrum with improved signal-to-noise statistics. Using yet-to-be published H i observations of the Coma cluster from the Westerbork Synthesis Radio Telescope, in combination with a new compilation of redshifts across the cluster, I explore the average H i content of galaxies located in different substructures within the cluster compared to cluster galaxies not associated with any substructure. While no conclusions can be made about which environment in Coma has a more dominant effect on the H i content, the analysis showed that there was a clear bimodality in the H i content of the cluster galaxies: either the galaxies were detected in H i, or the H i masses were well below the detection threshold. Where galaxies were not directly detected, they were found to be at least 10–50 times more H i deficient than field galaxies of the same type. Unlike the Coma cluster, Abell 2626 has not been as well studied, and so little is known about this cluster and its environs. In the second part of the thesis, I present new radio and optical observations of the cluster. Abell 2626 was observed by MeerKAT as part of the first open call for proposals. These observations have yielded H i data for Abell 2626 at the same H i mass sensitivity as the Westerbork observations of the Coma cluster, which is 2.5 times more nearby. Using the multi-object spectrograph, Hectospec, on the MMT telescope, we have created a spectroscopic catalogue of the Abell 2626 field that matches the MeerKAT observations and is 70% complete at r = 19.1 mag. The new spectroscopic catalogue around Abell 2626 enabled the characterisation of both the large scale structure in front of and behind the cluster, as well as the identification of substructure associated with the cluster. I am also able to determine that Abell 2626 is a rich cluster, comparable to the similarly sized Virgo cluster. I explore how the average H i content of galaxies of different luminosity, colour, and morphology change across the different local environments and substructure within the cluster. I find that late-type cluster galaxies located in substructures contain on average more H i than the late-type cluster galaxies not in substructures. I postulate that this suggests that the group environment protects the late-type galaxies from gas stripping mechanisms dominant in the global cluster environment. The H i stacking analysis shows that while Abell 2626 is not as H i deficient as the more massive Coma cluster, the Abell 2626 cluster galaxies do show a radial trend in the H i deficiencies as is observed in other clusters.