Can Cluster Evaporation Explain the Missing Thermal Energy in Galaxy Clusters?

Abstract

Resent observations of a number of galaxy clusters using the Sunyaev-Zel'dovich effect indicate that about 1/3 of baryonic mass is missing from the hot intracluster medium (ICM), which is significantly larger than the fraction of stars and cool gas, which account for only about 10%. Here we address the question whether the remaining $22\pm 10$ can be accounted for by thermal evaporation of gas from clusters. We have found that evaporation can occur only from the cluster ``surface'', $r\sim r_{\mathrm{vir}}$, and not from it's interior. We evaluated particle diffusion through the magnetized ICM for several scenarios of ISM turbulence and found that diffusivity is suppressed by at least a factor of 100 or more, compared to the Spitzer value. Thus, only particles from radii $r\ga0.9r_{\rm vir}$ can evaporate. Diffusion of particles from inside the cluster, $r\la0.9r_{\rm vir}$, takes longer than the Hubble time. This lowers the cluster-averaged fraction of the evaporated hot gas to few percent or less. However, if the missing hot component {\it is indeed} due to evaporation, this strongly constrains the magnetic field structure in the cluster envelope, namely either (i) the gas is completely unmagnetized ($B\le 10^{-21}$ gauss) in the cluster halo or (ii) the magnetic fields in the ICM are rather homogeneous and non-turbulent.

ApJL, accepted version; 4 pages, 2 figures

References in corpus (11)

• A Universal Density Profile from Hierarchical Clustering
• Tracing cosmic evolution with clusters of galaxies
• Thermal Conduction in Clusters of Galaxies
• Turbulent gas motions in galaxy cluster simulations: The role of SPH viscosity
• Evolving turbulence and magnetic fields in galaxy clusters
• A Bayesian view on Faraday rotation maps - Seeing the magnetic power spectra in galaxy clusters
• Enhancement and suppression of heat transfer by MHD turbulence
• Measuring the Cluster Magnetic Field Power Spectra from Faraday Rotation Maps of Abell 400, Abell 2634 and Hydra A
• Turbulent Velocity Fields in SPH--simulated Galaxy Clusters
• Transport phenomena in stochastic magnetic mirrors
• On the thermal conduction in tangled magnetic fields in clusters of galaxies

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