期刊
ASTROPHYSICAL JOURNAL
卷 530, 期 1, 页码 282-285出版社
UNIV CHICAGO PRESS
DOI: 10.1086/308370
关键词
cosmic rays; galaxies : clusters : individual (Abell 2199); intergalactic medium; magnetic fields; radio continuum : galaxies; X-rays : general
The Westerbork Northern Sky Survey (WENSS) and the NRAO/VLA Sky Survey were used to determine an upper limit to the diffuse radio flux from the nearby cluster Abell 2199. For the entire cluster, this limit is less than 3.25 Jy at 327 MHz from WENSS; for the inner 15' radius, the limit is less than 168 mJy at 1.4 GHz. These limits are used to constrain the cluster magnetic field by requiring that the radio flux be consistent with the hard X-ray (HXR) flux observed by BeppoSAX, assuming that the observed HXR excess is the result of inverse Compton scattering of cosmic microwave background photons by relativistic electrons in the intracluster gas. We find that the magnetic field must be very weak (<0.073 mu G) in order to avoid producing an observable radio halo. We also consider the possibility that the HXR excess is the result of nonthermal bremsstrahlung (NTB) by a population of suprathermal electrons that are being accelerated to higher energies. We find that a NTB model based on a power-law electron-momentum distribution with an exponent of mu approximate to 3.3 and containing about 5% of the number of electrons in the thermal ICM can reproduce the observed HXR flux.
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