1999boyceddbphd.pdf (3.42 MB)
UV studies of the local interstellar medium
thesis
posted on 2010-05-19, 09:25 authored by David Duncan BoyceWe present new measurements of the spatial distribution of cool and hot gas in the local
interstellar medium as a result of a search for O VI absorption in the FUV spectra of
100 white dwarfs at distances between 50 and 300 pc. We have carried out a detailed
velocity analysis on the detected O VI lines to ascertain the degree of contamination from
the background star. The position of the stars relative to the local cavity is calculated
through cold gas phase column density measurements. Through curve of growth analysis
we note that the local cavity is depleted in metals relative to hydrogen by a factor of 5
-10 compared to the space beyond.
Whereas the O VI producing hot gas was originally thought to be observed in the interface
regions between hot and cold gas, i.e. the cavity wall, our investigation nds no
unambiguously hot gas in lines of sight that span such regions. We do, however, nd hot
gas at high galactic latitudes where there are no such walls. We discuss the wider context
of this result by comparing the position of these detections to the soft X-ray background.
This work ultimately changes our picture of the local interstellar environment and its
processes by removing the ubiquitous million degree gas that was once thought to surround
the solar system. One possible explanation worthy of further investigation is that
the local cavity has recently begun to be inundated by hot gas spilling out of the loop 1
supernova remnant.
In support of this work there is an enclosed CD that contains the data and models used in
this thesis. Examples of the information found on this CD can be found in the appendix.
Explanations of the data, charts and graphs can be found in the body of the text when
required.
History
Supervisor(s)
Barstow, M.; Jameson, R.Date of award
2009-10-23Awarding institution
University of LeicesterQualification level
- Doctoral
Qualification name
- PhD