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Final Activity Report Summary - ARGOX (Advanced Research into Galaxy Clusters Observed in the X-ray)

This proposal was devoted to perform a detailed study of the atmosphere of clusters of galaxies using the most advanced X-ray space observatories available. Clusters of galaxies are the largest gravitationally bound structures of our universe and may contain up few thousand galaxies. The space between galaxies is filled with a diffuse, very low density, and extremely hot gas which is in hydrostatic equilibrium with the potential well produced by the cluster itself.

Due to the very high temperature the gas is fully ionized and emits in the X-rays for thermal bremsstrahlung mechanisms. This gas acts like a fluid and its status is strongly sensible to the formation history and evolution of the cluster itself. Merging events, in fact, produce strong transient phenomena that substantially alter the energetic, the thermal and spatial structure of this gas. By studying these structures it is this possible to investigate both the formation history and the evolution of these giant structures in the universe. One of the most prominent results obtained during this study was the discovery of a prominent region in the cluster of galaxies MKW3S whose gas temperature is much higher than predicted for a gas in hydrostatic equilibrium. It has been shown that this gas may have been shock-heated by the intermittent activity of a powerful AGN present in the central galaxy of MKW3S.

This results is extremely important as it allow us to better understand if AGN activity may or may not effectively provide enough energy to balance the loss of energy induced by the X-ray emission itself and, thus, if they can prevent the gas to cool and flow toward the cluster centre.

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