Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers

New radio telescopes under development, will significantly enhance the capabilities of radio astronomy in the Southern Hemisphere. South Africa, in particular, is actively involved in the development of a new array (MeerKAT) as well as in the expansion of existing very long baseline interferomete...

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Main Author: De Witt, Aletha
Other Authors: Booth, R.
Format: Others
Language:en
Published: 2012
Subjects:
522
Online Access:http://hdl.handle.net/10500/7046
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spelling ndltd-netd.ac.za-oai-union.ndltd.org-unisa-oai-umkn-dsp01.int.unisa.ac.za-10500-70462016-04-16T04:08:15Z Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers De Witt, Aletha Booth, R. Bietenholz, M. Maritz, R. ISM: molecules Jets and outflows Herbig-Haro Objects Supernova remnants Star formation Methods & techniques: data analysis Line profiles Masers Interferometric Surveys Wavelengths: radio emission lines Radio continuum 522 Radio astronomy -- technique Masers Radio interferometers New radio telescopes under development, will significantly enhance the capabilities of radio astronomy in the Southern Hemisphere. South Africa, in particular, is actively involved in the development of a new array (MeerKAT) as well as in the expansion of existing very long baseline interferometer arrays in the south. Participation in these new developments demands a thorough understanding of radio astronomy techniques, and data analysis, and this thesis focusses on two projects with the aim of gaining such experience. The Southern Hemisphere very long baselines array is not well served with calibrator sources and there are significant gaps in the present calibrator distribution on the sky. An adequately dense, well distributed, set of strong, compact calibrator or reference sources is needed. With this in mind, observations using the Southern Hemisphere long baseline array were conducted to investigate a sample of candidate calibrator sources. The compactness of the sources was investigated and new potential calibrators have been identified. Single antenna radio spectroscopy of OH masers has identified sources of 1720 MHz emission associated with supernova remnants at the shock interface between the expanding supernova remnant and a molecular cloud. Models indicate that these masers are shock excited and can only be produced under tight physical constraints. Out ows from newly-formed stars create nebulous regions known as Herbig-Haro objects when they interact with the surrounding medium, and these regions are potentially similar to those seen in supernova remnants. If conditions behind the shock fronts of Herbig-Haro objects are able to support 1720-MHz OH masers they could be a useful diagnostic tool for star formation. A survey toward Herbig-Haro objects using a single-dish radio telescope did detect 1720-MHz OH lines in emission, but neither their spectral signature nor follow-up observations with the Very Large Array showed evidence of maser emission. Mathematical Sciences Ph.D. (Astronomy) 2012-10-31T09:34:45Z 2012-10-31T09:34:45Z 2012-03 Thesis http://hdl.handle.net/10500/7046 en 1 online resource (xii, 155 leaves : ill. (some col.))
collection NDLTD
language en
format Others
sources NDLTD
topic ISM: molecules
Jets and outflows
Herbig-Haro Objects
Supernova remnants
Star formation
Methods & techniques: data analysis
Line profiles
Masers
Interferometric
Surveys
Wavelengths: radio emission lines
Radio continuum
522
Radio astronomy -- technique
Masers
Radio interferometers
spellingShingle ISM: molecules
Jets and outflows
Herbig-Haro Objects
Supernova remnants
Star formation
Methods & techniques: data analysis
Line profiles
Masers
Interferometric
Surveys
Wavelengths: radio emission lines
Radio continuum
522
Radio astronomy -- technique
Masers
Radio interferometers
De Witt, Aletha
Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers
description New radio telescopes under development, will significantly enhance the capabilities of radio astronomy in the Southern Hemisphere. South Africa, in particular, is actively involved in the development of a new array (MeerKAT) as well as in the expansion of existing very long baseline interferometer arrays in the south. Participation in these new developments demands a thorough understanding of radio astronomy techniques, and data analysis, and this thesis focusses on two projects with the aim of gaining such experience. The Southern Hemisphere very long baselines array is not well served with calibrator sources and there are significant gaps in the present calibrator distribution on the sky. An adequately dense, well distributed, set of strong, compact calibrator or reference sources is needed. With this in mind, observations using the Southern Hemisphere long baseline array were conducted to investigate a sample of candidate calibrator sources. The compactness of the sources was investigated and new potential calibrators have been identified. Single antenna radio spectroscopy of OH masers has identified sources of 1720 MHz emission associated with supernova remnants at the shock interface between the expanding supernova remnant and a molecular cloud. Models indicate that these masers are shock excited and can only be produced under tight physical constraints. Out ows from newly-formed stars create nebulous regions known as Herbig-Haro objects when they interact with the surrounding medium, and these regions are potentially similar to those seen in supernova remnants. If conditions behind the shock fronts of Herbig-Haro objects are able to support 1720-MHz OH masers they could be a useful diagnostic tool for star formation. A survey toward Herbig-Haro objects using a single-dish radio telescope did detect 1720-MHz OH lines in emission, but neither their spectral signature nor follow-up observations with the Very Large Array showed evidence of maser emission. === Mathematical Sciences === Ph.D. (Astronomy)
author2 Booth, R.
author_facet Booth, R.
De Witt, Aletha
author De Witt, Aletha
author_sort De Witt, Aletha
title Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers
title_short Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers
title_full Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers
title_fullStr Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers
title_full_unstemmed Radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers
title_sort radio astronomy techniques : the use of radio instruments from single dish radio telescopes to radio interferometers
publishDate 2012
url http://hdl.handle.net/10500/7046
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