Browsing by Author "Elson, Edward"

Now showing 1 - 4 of 4
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    Hi global scaling relations in the wise-whisp survey
    (Oxford University Press, 2021) Naluminsa, Elizabeth; Elson, Edward; Jarrett, Thomas
    We present the global scaling relations between the neutral atomic hydrogen gas, the stellar disk and the star forming disk in a sample of 228 nearby galaxies that are both spatially and spectrally resolved in HI line emission. We have used HI data from the Westerbork survey of HI in Irregular and Spiral galaxies (WHISP) and Mid Infrared (3.4 µm, 11.6 µm) data from the Wide-field Infrared Survey Explorer (WISE) survey, combining two datasets that are well-suited to such a study in terms of uniformity, resolution and sensitivity. We utilize a novel method of deriving scaling relations for quantities enclosed within the stellar disk rather than integrating over the HI disk and find the global scaling relations to be tighter when defined for enclosed quantities. We also present new HI intensity maps for the WHISP survey derived using a robust noise rejection technique along with corresponding velocity fields.
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    An hi study of the nearby dwarf galaxy ic 4710
    (University of Western Cape, 2021) Mothogoane, Getrude Thando; Elson, Edward
    This work aims to study the dark matter content of the nearby (7.38 Mpc) dwarf galaxy IC 4710 using the HI line observations from the Australia Telescope Compact Array (ATCA). We produce the rst interferometric maps of the galaxy HI distribution and dynamics and use these maps to measure important quantities such as total HI mass, velocity width, and size. We create a dynamical model of the galaxy using a three-dimensional modeling technique. The rotation curve was obtained by tting a 3D tilted ring model to the HI data cube of galaxy IC 4710. The dynamical modeling of IC 4710 is being done for the rst time. We compare the model to the data cube to check for accuracy and found that they are in good agreement; this shows that the results are reliable. The obtained rotation curve is rising steeply until it reaches the maximum rotation velocity of 24.6 km s􀀀1 at a radius of 100 arcsec.
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    Sample selection effects in laduma stacking experiments
    (University of the Western Cape, 2023) Gwebushe, Lwandile; Elson, Edward
    This study explores the impact of selection effects introduced by input optical cata-logues on high-redshift stacking experiments. Using the Hi stacking technique, the Hi content of LADUMA synthetic data cubes is analyzed within the redshift range of 0.7 < z < 0.758. The focus is on galaxies with stellar masses of M⋆/M⊙ ≥ 108.5. The investigation reveals several key findings. Firstly, the input optical catalogues displays biases towards specific galaxy types, including those with lower stellar masses, lower star-formation rates, lower specific star-formation rates, galaxies in groups, and red galaxies. These biases can lead to higher confusion rates in stacked spectra, emphasizing the need for appropriate correction methods to avoid overestimation in subsequent quantitative analyses. Secondly, the environmental impact on Hi gas properties is examined by comparing group galaxies and non-group galaxies. Non-group galaxies exhibit higher Hi richness and Hi gas fractions compared to group galaxies. Correlations between Hi properties and star-formation/stellar mass properties are observed, indicating that lower mass galaxies are relatively inactive within their environments and are at an earlier stage of evolution. The study also addresses the correction of confusion rates in stacked spectra. While a correction method is implemented, it is found to result in overestimated Hi deple-tion timescales. Criticism is directed towards the use of this method, stressing the importance of employing accurate and robust approaches to correct for confusion rates and ensure precise estimation of galaxy properties.
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    A study of the angular momentum content of early-type galaxies
    (University of the Western Cape, 2019) Tshiwawa, Unarine; Elson, Edward; Maartens, Roy