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Title: Investigations of Massive Stars in the Disk of the Milky Way with the UK Schmidt Ha Survey
Author: Hopewell, Ella Christina
ISNI:       0000 0004 2678 7593
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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New H-alpha emission line objects were searched for through spectroscopic follow-up of candidate H-alpha emitters from the UK/ST H-alpha survey using the 6dF and 2dF multi-object spectrographs. In total fifteen nights' of 6dF and four nights' of 2dF data were collected resulting in the discovery of more than 400 new emission line objects, of varying types - in several regions of the Southern Galactic Plane. A guide to the processes by which the target selection, observing and data reduction were conducted is presented. This process hinged upon using SHS catalogue data to construct (R-I)/(R-H-alpha) colour-colour plots and using these to identify sources with an apparent H-alphaexcess. The basics of the 6dfdr data reduction process are outlined. 5 massive Wolf-Rayet (WR) stars were discovered. The 6195-6775 A spectra of the stars are shown and discussed. A WC9 class is assigned to all 5 stars through comparison of their spectra with those of known late-type WC stars, bringing the known total number of Galactic WC9 stars to 44. Whilst three of the five WC9 stars exhibit near infrared (NIR) excesses characteristic of hot dust emission, as seen in the great majority of known WC9 stars, we find that two of the stars show no discernible evidence of such excesses. This increases the number of known WC9 stars without NIR excesses to 7. An additional WC9 star discovered from an alternative program of single slit follow-up is introduced and subjected to the same analysis as used on the other 5 WC9 stars. Observations of fields in and around the Puppis Window, an area known to show very low reddening, revealed a sample of early type stars. These stars were assigned spectral types based on comparisons with library spectra and the reddenings of these stars were estimated through four different methods. These data were used in conjunction with the spectral types to estimate distances through spectroscopic parallax and produces an estimation of the distance to the Perseus spiral arm of 4.1 ± 0.7 kpc.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available