The astrophysics of cosmic rays in galaxy clusters

Cosmic rays residing in galaxy clusters produce several astrophysical signatures among which there are diffuse synchrotron radio emission, ICS of CMB (and other background) photons which are then moved to higher frequencies 

The radio halo spectrum of Coma can be fitted out to ur 1.4 GHz with both primary and secondary models (e.g., Sarazin 1999, Blasi Colafrancesco 1999, Colafrancesco Mele 2001, Brunetti et al. 2001, Thierbach et al. 2003) and it does not provide a strong test bed. The claimed steepening of the spectrum at higher frequency can be attributed to the ageing of primarily accelerated electrons but can also reproduced in specific in-situ models (Thierbach et al. 2003). 

Both primary and secondary electron models (Atoyan Voelk 2000, Brunetti et al. 2001, Blasi Colafrancesco 1999, Miniati et al. 2001) have been analyzed to reproduce the spectral and spatial features of the EUV excess in Coma without a definite solution. Additional experimental information has been recently added to the complexity of the problem in particular, the EUV intensity distribution seems to be highly correlated with the thermal X-ray intensity and produce a constant ratio between the azimuthally averaged EUV and X-ray intensifies (Bowyer et al. 2004). Specific secondary models seem, at present, one of the few viable possibilities to reproduce the EUV emission features of Coma. 

in Diffuse Thermal and Relativistic Plasma in Galaxy Clusters , H. Boehringer, L. Feretti, P. Schuecker Eds., p. 

Longair, M. 1993, High-Energy Astrophysics , (CambridgeUniv. Press Cambridge) 

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