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Supervisors: Dr R Willingale, Dr R S Warwick
The ISM plays a vital role in the evolution and development of the Galaxy. It is the stuff from which new stars are born and it is the graveyard where dead stars are buried. Some regions are very hot, very tenuous and highly ionised while others are cool, dense and neutral.
X-ray observations provide a unique probe for the ISM. The hot plasma produces a diffuse soft X-ray component of the sky emission while the cool material absorbs soft X-rays from point sources beyond or immersed within. We are currently analysing all-sky soft X-ray absorption and emission data from ROSAT to map out the very local ISM often referred to as the Local Bubble. The quality and coverage of the present data give us the best view yet of the ISM within 200 parsecs of the Solar System. When this is complete the study of emission from more distant sources will allow us to extend the look out to 1000 parsecs or more. It is expected that forthcoming spectroscopic observations from the XMM Observatory will provide excellent detailed diagnostics of both the emission and absorption from the ISM and will tell us about the composition and ionisation state of material.
Supernovae are intimately linked with the ISM. They inject new stellar material and energy into the medium and the development of emission from supernova remnants acts as a probe of the interstellar environment surrounding the supernova. The ballistic kinetic energy of the initial ejector is gradually converted to thermal energy as the material ploughs into the ISM. Both thermal and non-thermal mechanisms give rise to the X-ray emission from SNRs and spectroscopic X-ray observations allow us to distinguish between the two. Detailed comparison of the X-ray emission with other wavebands from radio to optical gives us a powerful diagnostic of the physics of the shock.
The image above shows a composite ROSAT HRI image of the supernovae SN1006 displayed in false colour derived from the ROSAT PSPC spectra. Blue represents non-thermal emission, red represents thermal emission.
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Page maintained by Keith Sohl (kbs@star.le.ac.uk) |  |