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Abstract: Thermal X-ray spectra of clusters of galaxies and other sources are commonlycalculated assuming Maxwellian electron distributions. There are situationswhere this approximation is not valid, for instance near interfaces of hot andcold gas and near shocks. The presence of non-thermal electrons affects theX-ray spectrum. To study the role of these electrons in clusters and otherenvironments, an efficient algorithm to calculate the X-ray spectra is needed.We approximate an arbitrary electron distribution by the sum of Maxwelliancomponents. The decomposition is done using either a genetic algorithm or ananalytical approximation. The X-ray spectrum is then evaluated using a linearcombination of those Maxwellian components. Our method is fast and leads to anaccurate evaluation of the spectrum. The use of Maxwellian components allows touse the standard collisional rates that are available in plasma codes such asSPEX. We give an example of a spectrum for the supra-thermal electrondistribution behind a shock in a cluster of galaxies. The relative intensitiesof the satellite lines in such a spectrum are sensitive to the presence of thesupra-thermal electrons. These lines can only be investigated with highspectral resolution. We show that the instruments on future missions likeAstro-H and IXO will be able to demonstrate the presence or absence of thesesupra-thermal electrons.



Author: J.S. Kaastra, A.M. Bykov, N. Werner

Source: https://arxiv.org/







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