http://arxiv.org/abs/1806.08822
The discrepancy between expected and observed cooling rates of X-ray emitting gas has led to the cooling flow problem at the cores of clusters of galaxies. A variety of models have been proposed to model the observed X-ray spectra and resolve the cooling flow problem, which involves heating the cold gas through different mechanisms. As a result, realistic models of X-ray spectra of galaxy clusters need to involve both heating and cooling mechanisms. In this paper, we argue that the heating time-scale is set by the magnetohydrodynamic (MHD) turbulent viscous heating for the Intracluster plasma, parametrised by the Shakura-Sunyaev viscosity parameter, $\alpha$. Using a cooling+heating flow model, we show that a value of $\alpha\simeq 0.08$ (with 20% scatter) provides improved fits to the X-ray spectra of cooling flow, while at the same time, predicting reasonable cold mass budgets accumulated in the cores of clusters over half the Hubble time. Our inferred values for $\alpha$ based on X-ray spectra are also in line with direct measurements of turbulent pressure in simulations and observations of galaxy clusters. This simple picture unifies astrophysical accretion, as a balance of MHD turbulent heating and cooling, across more than 16 orders of magnitudes in scale, from neutron stars to galaxy clusters.
M. Haghighi, N. Afshordi and H. Khosroshahi
Tue, 26 Jun 18
41/71
Comments: N/A