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Title: The early lives of radio-loud quasars
Author: de Silva, E.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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The reason why Compact, Steep-Spectrum (CSS) radiosources are compact has been the subject of much debate, with current opinions divided between two competing theories. On the one hand it has been suggested that the growth of CSS jets is stunted by an external medium. On the other hand it is thought that CSSs may be the younger versions of classical doubles. In order to better investigate these ideas I have used a new, complete and well-defined sample, the Molonglo quasar sample (MQS). I have studied MQS CSSs, exploiting the superior angular resolution of the MERLIN radio interferometer, and the sensitivity and spectral capabilities of the ANU 2.3 m and AAT optical telescopes. Similar measurements exist for larger MQS objects, and this allows an accurate comparison to be made between the properties of the two sets. Using these radio and optical emission-line data I have evaluated the ages of a range of CSSs and larger objects from the MQS, finding that in fact CSSs are young. There is clear evidence for the presence of significant dust, neutral hydrogen and absorbing clouds of narrow-line gas around CSSs. Use of a source growth model has shown the way in which the density of the host galaxy environment changes with distance from the nucleus. That the jets interact strongly with their surroundings is verified by the dominance of shock-ionisation in CSSs, which, it appears, grow self-similarly, burrowing through the ISM clearing out surrounding material as they do so. The source evolution model presented fits with the unified scheme, and an evolutionary scenario in which CSSs occupy the phase after merger and triggering of the jets, and before eventual growth into classical doubles.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available