O'Sullivan, Ewan
(2002).
X-ray properties of early-type galaxies.
University of Birmingham.
Ph.D.
Abstract
It has been known for some time that many early–type galaxies possess halos of X–ray emitting gas. However, the properties of these halos and the processes by which they form are as yet not well understood. We have compiled the largest catalogue of X–ray luminosities to date, and use it to examine the relationships between X–ray luminosity and galaxy age, environment and optical luminosity. It is shown that the mass of the X–ray halo increases with galaxy age, and that there is no trend in LX/LBwith environment. Group dominant galaxies are shown to be more X–ray luminous than galaxies in other environments, and the effect of this on the LX:LBrelation is explored. A smaller sample of highly X–ray luminous galaxies is studied in more detail, and their properties compared to those of galaxy groups and clusters. It is shown that while galaxy halos are similar to those of larger structures they differ in that their surface brightness profiles do not vary with system temperature. It is also shown that early–type galaxies have lower gas fractions than groups and clusters, probably owing to gas loss from the system through galaxy winds.
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