2002/08/28 by H. Liang, V. Dogiel, V. A. Dogiel +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Cosmic Phenomena #Bremsstrahlung #Coma Cluster #Compton scattering #Electron #Galaxies: Formation, Evolution, Phenomena #Galaxy cluster #Halo #Magnetic field #Population #Radio halo #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.2002.05937.x
published as Mon.Not.Roy.Astron.Soc. 337 (2002) 567 · 14 pages, 7 figures, accepted by MNRAS
arxiv created 2002/08/28 · openalex publication_date 2002/09/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We study the origin of the non-thermal emission from the intracluster medium, including the excess hard X-ray emission and cluster-wide radio haloes, through fitting two representative models to the Coma cluster. If the synchrotron-emitting relativistic electrons are accelerated in situ from the vast pool of thermal electrons, then a quasi-stationary solution of the kinetic equation with particle acceleration through turbulence at high energies (>200 keV) naturally produces a population of suprathermal electrons responsible for the excess hard X-ray emission through bremsstrahlung. Inverse Compton scattering is negligible at hard X-ray energies in this case. The radio halo flux density constrains the magnetic field strength to a value close to that of equipartition, ∼1 μG. Alternatively, if the relativistic electrons are injected from numerous localized ‘external’ sources, then the hard X-rays are best explained by inverse Compton scattering from GeV electrons, and little of the hard X-radiation has a bremsstrahlung origin. In this case, the magnetic field strength is constrained to ∼0.1–0.2 μG. Both models assume that the non-thermal emissions are generated by a single electron spectrum, so that only two free parameters, well constrained by the observed hard X-ray and radio halo spectra, are needed in either case. Measurements of the cluster magnetic field will distinguish between the models.