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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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.)) |
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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 |
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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 |
work_keys_str_mv |
AT dewittaletha radioastronomytechniquestheuseofradioinstrumentsfromsingledishradiotelescopestoradiointerferometers |
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1718224626124849152 |