| Summary: | Galaxy clusters are the largest gravitationally bound objects in the Universe. The study of galaxy clusters can give insights into the large-scale structure of the Universe and provide constraints on the cosmological parameters that dictate the evolution of the Universe. Bent-tail radio sources are a class of Active Galactic Nuclei (AGN) where the jets or lobes have been distorted significantly due to the relative movement through a dense medium. This behaviour is expected to occur in galaxy clusters, especially those of high mass. I have planned and carried out the observations for the ATLAS-SPT survey, a radio continuum survey of ~86 deg2 using the Australia Telescope Compact Array at a central observing frequency of 2.1GHz over a bandwidth of 2GHz, with the telescope in an extended array configuration with a maximum baseline length of 6 km. The calibrated dataset was imaged, deconvolved using a multi-frequency deconvolution algorithm, and corrected for wide-bandwidth primary beam effects to produce total intensity and spectral variation images for each pointing. The limited u, v coverage of the survey caused several imaging challenges; the most significant being a poorly behaved synthesised beam response pattern and sidelobes from moderately bright outlier sources producing image artefacts. I devised an imaging pipeline which minimised the outlier source artefacts by employing a two-stage imaging process: 1) each pointing was imaged well beyond the primary beam with a coarse pixel resolution to find bright outlying sources; 2) outlying sources with a brightness expected to produce a synthesised beam pattern above the thermal noise of the pointing were modelled and subtracted from the pointing dataset. After subtracting the outlying sources, imaging could proceed as normal. Once each pointing was imaged, they were convolved with a Gaussian to produce a common angular resolution of 800 and linearly mosaicked to produce two images of the entire field: one total intensity mosaic and a spectral index mosaic. Due to limitations in the mosaicking software, 9 overlapping mosaic tiles were produced and subsequently combined with a custom imaging script. The final combined total intensity mosaic contains approximately 43 000 x 40 000 px and has a median rms noise level of approximately 180 μJy. I have produced a radio source catalogue containing positions and flux densities of 6067 sources. 722 of these sources have sufficient signal-to-noise ratios to provide a reliable spectral index measurement which is also included in the catalogue. I conducted a completeness simulation which indicates that the catalogue is 100% complete at the 1.3mJy beam−1 flux density level. This simulation was also used to estimate the flux density and positional accuracies. Due to noise fluctuations, flux densities of the faintest catalogued sources (~0.36mJy beam−1) are boosted by ~30%, and the boosting level falls below 5% for sources ≥$0.74mJy beam−1. The extracted positions have a median offset of ≪1" from their simulated input positions with a standard deviation of σ = 1.6" for the faintest sources, improving to σ = 0.5" for sources with flux densities ≥$1.3mJy beam−1. The catalogue was also matched and compared with the ATCA-XXL survey which covered the inner 25 deg2 of the field to a greater sensitivity. The matched sources are shown to be in excellent flux density and positional agreement. I constructed a Euclidean-normalised differential source count using the ATLAS-SPT catalogue, incorporating the necessary flux density corrections from the completeness simulation. The source counts agree well with others from the literature. The result confirms that the ATLAS-SPT survey is most sensitive to AGN and the steepening of the source counts clearly show the evolution of these sources. The source counts toward the catalogue sensitivity limit show the characteristic flattening, indicating the increased population of star-forming galaxies at those flux densities. I have identified 50 bent-tail radio galaxy candidates from the ATLAS-SPT total intensity mosaic by visual inspection and cross-matched these sources with the deep 3.6 μm Spitzer– South Pole Telescope Deep Field (SSDF) catalogue of the field. I then cross-matched the SSDF sources to both the Blanco Cosmology Survey (BCS) and Dark Energy Survey (DES) Science Verification catalogues and provide photometric redshift estimates for 17 bent-tail candidates. I then cross-matched these bent-tail candidates with redshifts to known cluster catalogues (546 in total). I found that only 4 are associated with known clusters. Recent models when applied to this dataset predict that ~7 bent-tail sources should be associated with high-mass (M ≥ 10 15M.) clusters such as those from the SPT SZ cluster catalogue. Instead I find only one. The lack of bent-tail sources within clusters may be explained by various effects such as projection, resolution, and AGN duty cycle. However, the lack of clusters found around bent-tail sources is more problematic and suggests that bent-tails may reside in cluster of lower mass than expected.
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