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Abstract: High resolution X-ray spectroscopy of the hot gas in galaxy clusters hasshown that the gas is not cooling to low temperatures at the predicted rates ofhundreds to thousands of solar masses per year. X-ray images have revealedgiant cavities and shock fronts in the hot gas that provide a direct andrelatively reliable means of measuring the energy injected into hot atmospheresby active galactic nuclei AGN. Average radio jet powers are near thoserequired to offset radiative losses and to suppress cooling in isolated giantelliptical galaxies, and in larger systems up to the richest galaxy clusters.This coincidence suggests that heating and cooling are coupled by feedback,which suppresses star formation and the growth of luminous galaxies. How jetenergy is converted to heat and the degree to which other heating mechanismsare contributing, eg. thermal conduction, are not well understood. Outburstenergies require substantial late growth of supermassive black holes. Unlessall of the approximately 10E62 erg required to suppress star formation isdeposited in the cooling regions of clusters, AGN outbursts must alterlarge-scale properties of the intracluster medium.

Author: B. R. McNamara U. Waterloo, P. E. J. Nulsen CfA

Source: https://arxiv.org/

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