In this thesis, we investigate the flow field in and around the major large-scale structures in the southern Zone of Avoidance as derived from peculiar motions of galaxies. The peculiar velocities were derived from a galaxy sample based on the systematic deep Parkes HI Zone of Avoidance survey (HIZOA) using a newly optimized Near InfraRed (NIR) Tully-Fisher (TF) relation. The NIR imaging data of the HIZOA galaxies were obtained with the Infrared Survey Facility (IRSF) on the 1.4-m telescope at the South African Astronomical Observatory, which allows simultaneous three-colour (J; H; and Ks) imaging. We first calibrate the NIR Tully-Fisher relation for isophotal magnitudes, using the same 888 calibrator galaxies that were used for the derivation of the 2MASS TF relation for total magnitudes. The isophotal NIR TF relation allows for a significant improvement in the scatter of low surface brightness galaxies, and galaxies obscured by dust. We also simulate the effect of dust extinction on the shape of galaxies and derive a correction model. We show the ability of this model to reproduce the intrinsic axial ratio from the observed parameters up to extinction levels of AV ~ 11 mag. We present new narrow-band HI 21-cm observations for 394 selected galaxies from the HIZOA survey with improved velocity resolution. These new observations with high resolution allow a robust measurement of five different types of linewidth. We used a Bayesian mixture model to derive conversion equations between these five widths, which will be used to combine data sets of differently-derived linewidths. We present deep near-infrared (J; H; and Ks bands) observations of 1108 detections from the HIZOA survey. The average seeing, sky background and the isophotal magnitude errors are 1:38 arcsec, 20:1 mag, and 0:02 mag respectively, which are of sufficient accuracy for a Tully-Fisher analysis. Through comparisons with 2MASS and UKIDSS images we demonstrate the reliability of the IRSF photometry. We use these data and the isophotal Tully-Fisher relation to measure distances and peculiar velocities for 287 galaxies, which covers the whole southern ZOA. We derive the HI mass function to make predictions for the Malmquist bias, thus enabling us to correct the measured distances accordingly. The slope of the HI mass function agrees with both HIPASS Bright Galaxy Catalog (BGC) and ALFALFA, whereas the characteristic HI mass aligns more closely with ALFALFA than the HIPASS BGC. We map the velocity field around the major large-scale structures in the southern ZOA, such as the Great Attractor (GA), the Local Void (LV), and the Puppis region. In the GA region, we find a clear infall into the GA from both sides. Our analysis of the LV shows that the void galaxies are moving away from the center which confirms the recent results which show the draining of the LV. We also find outflow from the Puppis region. We present comparisons between the velocity field derived in this thesis, the 2MASS TullyFisher observations (2MTF), the 2MASS Redshift Survey (2MRS), as well as the IRAS Point Source Catalog Redshift Survey (PSCz) reconstructions. We find good agreement at low redshift with the 2MTF observations, better than the 2MRS and the PSCz reconstructions. At high redshift, our results disagree with the 2MTF observations, the 2MRS, and the PSCz reconstructions.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/25463 |
| Date | January 2017 |
| Creators | Soliman, Khaled Said Ahmed |
| Contributors | Kraan-Korteweg, Renée C, Jarrett, Thomas H, Staveley-Smith, Lister |
| Publisher | University of Cape Town, Faculty of Science, Department of Astronomy |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Doctoral Thesis, Doctoral, PhD |
| Format | application/pdf |
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