Equilibration Processes in the Warm-Hot Intergalactic Medium |
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Authors: | A M Bykov F B S Paerels V Petrosian |
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Institution: | (1) A.F. Ioffe Institute of Physics and Technology, St. Petersburg, 194021, Russia;(2) Columbia Astrophysics Laboratory, Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA;(3) Department of Physics, Stanford University, Stanford, CA 94305, USA |
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Abstract: | The Warm-Hot Intergalactic Medium (WHIM) is thought to contribute about 40–50% to the baryonic budget at the present evolution
stage of the universe. The observed large scale structure is likely to be due to gravitational growth of density fluctuations
in the post-inflation era. The evolving cosmic web is governed by non-linear gravitational growth of the initially weak density
fluctuations in the dark energy dominated cosmology. Non-linear structure formation, accretion and merging processes, star
forming and AGN activity produce gas shocks in the WHIM. Shock waves are converting a fraction of the gravitation power to
thermal and non-thermal emission of baryonic/leptonic matter. They provide the most likely way to power the luminous matter
in the WHIM. The plasma shocks in the WHIM are expected to be collisionless. Collisionless shocks produce a highly non-equilibrium
state with anisotropic temperatures and a large differences in ion and electron temperatures. We discuss the ion and electron
heating by the collisionless shocks and then review the plasma processes responsible for the Coulomb equilibration and collisional
ionisation equilibrium of oxygen ions in the WHIM. MHD-turbulence produced by the strong collisionless shocks could provide
a sizeable non-thermal contribution to the observed Doppler parameter of the UV line spectra of the WHIM. |
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Keywords: | Intergalactic medium Shock waves Galaxies: clusters: general |
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