The results of the fourth part of the Rhodes University Skymap Program are presented. The observations cover the area of sky between right ascension 14h00m and 02h30m and declination -26⁰ and + 13⁰ at a frequency of 2.3 GHz. Contour maps of this region, with a resolution of 0.38⁰, are presented. Various methods of reducing the effect of the Galactic disc emission are analyzed. The results demonstrate the effectiveness of one of these methods in the production of a flat base level. The filamentary structure of the North Polar Spur is enhanced and results are obtained which support current theories of the origin of this object. The HII region surrounding Ophiuchi is examined in detail. A number of parameters are derived for the HII region. The spur associated with the HII region S54 is also examined. A listing of 1105 point sources appearing in the maps is presented. The limiting flux density of this listing is 0.5 Jy

The results of the second part of the Rhodes University Southern Sky Survey at 2.3GHz are presented. The area surveyed extends from 12hOO to 22hOO right ascension between declinations -63º and -24º. The observation technique and data reduction processes are analyzed. Digital data processing techniques used to enhance and display the data are dicussed. The results show that the Galactic emission extends as far as 40º latitude. Filamentary and loop-like structures are found superimposed on this general emission. Many of these features are unidentified as yet. A large region of emission is found to coincide with the Sco-Cen stellar association. A lower limit for the ionizing flux from the stars in the association is derived. All of the non-confused extragalactic sources with flux densities greater than O.5Jy are listed. The flux densities of these sources have been measured and any possible extended features are noted. / KMBT_363 / Adobe Acrobat 9.53 Paper Capture Plug-in

The Rhodes/HartRAO SKYMAP survey is the highest frequency (2326 MHz) and highest resolution (20 arcmin) large-area pencil-beam survey of the celestial radio continuum emission. The survey covers 67 % of the entire sky and is one of only two radio continuum surveys that cover the southern sky. These attributes make the survey eminently suitable for studying the extended radio continuum emission from the Milky Way. This thesis describes the methodology used to produce the SKYMAP survey map and presents an analysis of the galactic radio continuum emission. Mountfort (1989, PhD thesis, Rhodes University) designed and implemented the original SKYMAP observing and data reduction procedures. These original procedures have been modified and extended to accommodate instrumentation upgrades at HartRAO and take advantage of new computer technologies that have become available. A new procedure was developed to perform the merging of the ten individual target-area maps into a self-consistent combined map without discontinuities at the component map boundaries. Calibration and data quality procedures were devised and implemented in order to validate the temperature scale and pointing accuracy of the map data. The uncertainty in the relative full-beam temperature scale is estimated to be 2 % and the RMS pixel noise is less than 30 mK. The uncertainty in the zero-level of the survey map is conservatively estimated to be 80 mK. The RMS pointing accuracy is better than 1.9 arcmin. The diffuse galactic background (DGB) emission is shown to be consistent with four-arm spiral models for the Milky Way. The Gould Belt system and the galactic warp beyond the solar-circle are seen as non-symmetrical distortions in the DGB. An empirical model of the DGB was subtracted from the 2326 MHz map data in order to accentuate faint, extended radio sources. A new technique was devised to discriminate between thermal and non-thermal radio continuum emission on the basis of FIR/radio flux ratios. This procedure was used to reduce the source confusion near the galactic plane. 42 new shell-like radio sources with angular diameters ranging from 1.6 deg to 26 deg are identified in the SKYMAP 2326 MHz map. These sources are probably large-diameter supernova remnants (SNRs) that partially redress the incompleteness in existing SNR catalogues caused by limited surface brightness selection effects. The shells of some of these faint, extended sources are incomplete towards high-latitudes. This morphology suggests that these objects are breaking out of the galactic disk and are releasing hot gas into the halo. There is no evidence for linear worm- and chimney-like features in the non-thermal galactic emission. The spectral index of the diffuse galactic emission is calculated to be beta = 2.72 +/- 0.18 between 408 MHz and 2326 MHz and beta = 2.95 +/- 0.08 between 2326 MHz and 31 GHz, confirming previous work showing that the synchrotron spectrum steepens with increasing frequency. The high frequency spectral index is used to estimate upper limits on the galactic synchrotron foreground contamination of cosmic microwave background radiation measurements. The high-latitude 2326 MHz galactic emission is shown to correlate weakly with the far-infrared galactic cirrus clouds. This correlation is due to thermal free-free radio emission from extended, low-density HII regions associated with the cirrus dust. The RMS level of this thermal signal is estimated to be 1 mK at 2326 MHz. Two further experiments that need to be performed in order to complete the SKYMAP project are discussed: (a) the region of sky near the southern equatorial pole (SEP) needs to be mapped at HartRAO to complete the coverage of the entire southern sky, and (b) independent horn telescope (broad-beam) measurements of the sky temperature are required in order to reduce the baseline uncertainties in the current SKYMAP data.

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, June 2003. / Includes bibliographical references. Also available on the Internet.

A considerable number of Very Long Baseline Interferometry (VLBI) surveys have been conducted in the northern hemisphere and very few in the southern hemisphere mostly because of a lack of telescopes and therefore adequate baseline coverage. Thus there is a deficit of calibrator sources in the southern hemisphere. Further, some of the most interesting astronomical objects eg. the galactic centre and the nearest galaxies (the small and large Magellanic Clouds) lie in the southern hemisphere and these require high resolution studies. With a major expansion of radio astronomy observing capability on its way in the southern hemisphere (with the two SKA (Square Kilometre Array) precursors, meerKAT (Karoo Array Telescope) and ASKAP (Australian SKA Pathfinder), leading to the SKA itself) it is clear that interferometry and VLBI in the southern hemisphere need a dense network of calibration sources at different resolutions and a range of frequencies. This work seeks to help redress this problem by presenting an analysis of 31 southern sources to help fill the gaps in the southern hemisphere calibrator distribution. We have developed a multi-parameter method of classifying these sources as calibrators. From our sample of 31 sources, we have 2 class A sources (Excellent calibrators), 16 class B sources (Good calibrators), 9 class C sources (Poor calibrators) and 4 class D sources (Unsuitable calibrators).