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Einstein x-ray observations of galaxies.

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posted on 19.11.2015, 09:17 by Vaughan John. Stanger
The high sensitivity and precise imaging provided by the Einstein Observatory instrumentation has enabled detailed X-ray studies of a variety of astrophysical phenomena to be performed. In this thesis Einstein observations are used to investigate the characteristic X-ray properties of galaxies, thus allowing a galaxy's X-ray emission to be related to the properties and evolution of its stellar population(s). Analysis of Einstein HRI data for M82 - an archetypal peculiar galaxy - reveals complex structure both in the "starburst" nuclear region and in the galaxy's halo. The nuclear region's X-ray morphology corresponds closely with Population I optical features, thus linking the emission directly to the intense star formation activity. Moreover, the halo of diffuse X-ray emission distributed along the minor axis of M82 indicates thermal emission from outflowing hot gas, which is maintained by starburst-induced supernova heating; rapid cooling near shock fronts probably causes the observed correlation with the famous H? filament system. The majority of this thesis is devoted to an investigation of the X- ray properties of early type galaxies. Analysis of luminosity correlations displayed by the class as a whole, complemented by detailed studies of individual galaxies, confirms previous suggestions that for many early type galaxies, thermal emission from hot gas is the dominant X-ray emission mechanism. Supernova-driven hot winds keep some galaxies essentially gas free; their X-ray emission originates principally from stellar sources. In other galaxies hot gas generated by stellar evolution is retained and possibly incorporated into cooling flows. High resolution X-ray and radio studies of NGC 4636 and NGC 4649 confirm that cooling flow scenarios are viable for the central regions of both galaxies, thus explaining the fueling of the observed radio sources. Finally, the possibilities for further research presented by both current and future observational facilities are discussed.


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Physics and Astronomy

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University of Leicester

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