Year: 2009
Type: dissertation
Abstract: We present new measurements of the spatial distribution of cool and hot gas in the local\ninterstellar medium as a result of a search for O VI absorption in the FUV spectra of\n100 white dwarfs at distances between 50 and 300 pc. We have carried out a detailed\nvelocity analysis on the detected O VI lines to ascertain the degree of contamination from\nthe background star. The position of the stars relative to the local cavity is calculated\nthrough cold gas phase column density measurements. Through curve of growth analysis\nwe note that the local cavity is depleted in metals relative to hydrogen by a factor of 5\n-10 compared to the space beyond.\nWhereas the O VI producing hot gas was originally thought to be observed in the interface\nregions between hot and cold gas, i.e. the cavity wall, our investigation nds no\nunambiguously hot gas in lines of sight that span such regions. We do, however, nd hot\ngas at high galactic latitudes where there are no such walls. We discuss the wider context\nof this result by comparing the position of these detections to the soft X-ray background.\nThis work ultimately changes our picture of the local interstellar environment and its\nprocesses by removing the ubiquitous million degree gas that was once thought to surround\nthe solar system. One possible explanation worthy of further investigation is that\nthe local cavity has recently begun to be inundated by hot gas spilling out of the loop 1\nsupernova remnant.\nIn support of this work there is an enclosed CD that contains the data and models used in\nthis thesis. Examples of the information found on this CD can be found in the appendix.\nExplanations of the data, charts and graphs can be found in the body of the text when\nrequired.
Author: D. D. Boyce
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W223739314