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C. Ferrari F. Govoni S. Schindler A. M. Bykov Y. Rephaeli 《Space Science Reviews》2008,134(1-4):93-118
We review observations of extended regions of radio emission in clusters; these include diffuse emission in ‘relics’, and
the large central regions commonly referred to as ‘halos’. The spectral observations, as well as Faraday rotation measurements
of background and cluster radio sources, provide the main evidence for large-scale intracluster magnetic fields and significant
densities of relativistic electrons. Implications from these observations on acceleration mechanisms of these electrons are
reviewed, including turbulent and shock acceleration, and also the origin of some of the electrons in collisions of relativistic
protons by ambient protons in the (thermal) gas. Improved knowledge of non-thermal phenomena in clusters requires more extensive
and detailed radio measurements; we briefly review prospects for future observations. 相似文献
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J. S. Kaastra A. M. Bykov S. Schindler J. A. M. Bleeker S. Borgani A. Diaferio K. Dolag F. Durret J. Nevalainen T. Ohashi F. B. S. Paerels V. Petrosian Y. Rephaeli P. Richter J. Schaye N. Werner 《Space Science Reviews》2008,134(1-4):1-6
We present the work of an international team at the International Space Science Institute (ISSI) in Bern that worked together
to review the current observational and theoretical status of the non-virialised X-ray emission components in clusters of
galaxies. The subject is important for the study of large-scale hierarchical structure formation and to shed light on the
“missing baryon” problem. The topics of the team work include thermal emission and absorption from the warm-hot intergalactic
medium, non-thermal X-ray emission in clusters of galaxies, physical processes and chemical enrichment of this medium and
clusters of galaxies, and the relationship between all these processes. One of the main goals of the team is to write and
discuss a series of review papers on this subject. These reviews are intended as introductory text and reference for scientists
wishing to work actively in this field. The team consists of sixteen experts in observations, theory and numerical simulations. 相似文献
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Scattering of the cosmic microwave background (CMB) radiation by hot gas in clusters of galaxies produces a unique spectral signature – the Sunyaev–Zeldovich (S–Z) effect – that constitutes an important cosmological probe. The effect has been sensitively measured in more than 40 clusters, mostly with ground-based interferometric arrays operating at low microwave frequencies. These measurements have already yielded important information on cluster masses, and the Hubble constant. The scientific yield will be greatly increased when spectral and high-resolution spatial measurements of the effect in a large sample of nearby clusters will be made with stratospheric telescopes equipped with bolometric arrays. I review the current status of observational and theoretical S–Z work, and describe the main goals and challenges of using the effect as a more precise probe of cluster properties and cosmological parameters. 相似文献
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In this paper we review the possible radiation mechanisms for the observed non-thermal emission in clusters of galaxies, with
a primary focus on the radio and hard X-ray emission. We show that the difficulty with the non-thermal, non-relativistic Bremsstrahlung
model for the hard X-ray emission, first pointed out by Petrosian (Astrophys. J. 557, 560, 2001) using a cold target approximation, is somewhat alleviated when one treats the problem more exactly by including the fact
that the background plasma particle energies are on average a factor of 10 below the energy of the non-thermal particles.
This increases the lifetime of the non-thermal particles, and as a result decreases the extreme energy requirement, but at
most by a factor of three. We then review the synchrotron and so-called inverse Compton emission by relativistic electrons,
which when compared with observations can constrain the value of the magnetic field and energy of relativistic electrons.
This model requires a low value of the magnetic field which is far from the equipartition value. We briefly review the possibilities
of gamma-ray emission and prospects for GLAST observations. We also present a toy model of the non-thermal electron spectra that are produced by the acceleration mechanisms
discussed in an accompanying paper Petrosian and Bykov (Space Sci. Rev., 2008, this issue, Chap. 11). 相似文献
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