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Observational signatures of massive star formation : an investigation of the environments in which they form, and the applicability of the paradigm of low-mass star formation
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dc.contributor.advisor | Wood, Kenny | |
dc.contributor.author | Johnston, Katharine G. | |
dc.coverage.spatial | 212 | en_US |
dc.date.accessioned | 2011-06-23T09:11:26Z | |
dc.date.available | 2011-06-23T09:11:26Z | |
dc.date.issued | 2011-06-24 | |
dc.identifier.uri | https://hdl.handle.net/10023/1895 | |
dc.description.abstract | This thesis presents both a study of the cluster-scale environments in which massive stars form, investigating in particular how the ionized gas in these regions relates to the molecular star-forming material, as well as detailed studies of two luminous forming stars, AFGL 2591 and IRAS 20126+4104, to determine whether they are forming similarly to their low-mass counterparts. The results of this work include the identification of 35 HII regions (20 newly discovered) via a radio continuum survey of ionized gas towards 31 molecular cluster-forming clumps. The observed ionized gas was found to be preferentially associated with the clumps, which were shown to have a range of evolutionary stages. The massive star formation efficiency was determined for the clumps with associated ionized gas, and a relationship was found between the mass of the clumps and the mass of their embedded massive stars. By modelling the SEDs and images of AFGL 2591 and IRAS 20126+4104, it was found that the geometry of their circumstellar material was generally consistent with an envelope plus disk, similar to that expected for low-mass protostars. However, within the central ~1800 AU, the mid-IR images of IRAS 20126+4104 were better described by only a flattened envelope, suggesting that the radiation from IRAS 20126+4104 may be affecting the regions closest to the star. Observations of the ionized and molecular gas towards AFGL 2591 were carried out, and a photoionization code was developed to interpret these observations. The results showed that the observed 3.6 cm emission is likely to be produced by both a shock-ionized jet and a hypercompact HII region that does not appear to have disrupted the jet or the large-scale circumstellar environment. In addition, the C¹⁸O(1-0) emission observed towards AFGL2591 traces the densest parts of the outflow, with the blue-shifted emission exhibiting many of the properties of the outflows from low-mass protostars. | en_US |
dc.language.iso | en | en_US |
dc.publisher | University of St Andrews | |
dc.rights | Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported | |
dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/3.0/ | |
dc.subject | Astronomy | en_US |
dc.subject | Star formation | en_US |
dc.subject | Massive stars | en_US |
dc.subject | Modelling | en_US |
dc.subject | Observations | en_US |
dc.subject | Young stars | en_US |
dc.subject.lcc | QB843.S9J7 | |
dc.subject.lcsh | Supergiant stars | en_US |
dc.subject.lcsh | Stars--Formation | en_US |
dc.title | Observational signatures of massive star formation : an investigation of the environments in which they form, and the applicability of the paradigm of low-mass star formation | en_US |
dc.type | Thesis | en_US |
dc.type.qualificationlevel | Doctoral | en_US |
dc.type.qualificationname | PhD Doctor of Philosophy | en_US |
dc.publisher.institution | The University of St Andrews | en_US |
dc.publisher.department | School of Physics and Astronomy | en_US |
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