1999/07/09 by G. Brunetti, Brunetti, G., L. Feretti +6
Physics and Astronomy · #Astrophysics (astro-ph) #Cosmology and Gravitation Theories #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9907125
6 pages, plus 5.ps figures, Latex; to appear in proceedings of the Ringberg workshop on 'Diffuse Thermal and Relativistic Plasma in Galaxy Clusters', April 1999, H.Boeringer, L.Feretti, P.Schuecker (eds); type error in Eq.6 corrected
openalex publication_date 1999/07/09 · arxiv created 1999/07/19 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The radio spectral index map of the Coma halo shows a progressive steepening of the spectral index with increasing radius. Such a steepening cannot be simply justified by models involving continuous injection of fresh particles in the Coma halo or by models involving diffusion of fresh electrons from the central regions. We propose a scenario in which the relativistic particles injected in the Coma cluster by some processes (merger, accretion shocks, turbulence) are systematically reaccelerated for a relatively long time (∼ 1Gyr). We show that such a scenario can account for the synchrotron radio spectral index distribution, for the radio halo size at different frequencies, and for the total (integrated) radio spectrum of the Coma halo. We also show that for a suitable choice of the parameters the model can also account for the hard X-ray flux observed by BeppoSAX via the inverse Compton scattering of the cosmic microwave background radiation by the synchrotron electrons. The possibility to account for the EUV flux detected with the EUVE satellite by the inverse Compton emission is also discussed.