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Abstract: The gas in the cores of many clusters and groups of galaxies has a shortradiative cooling time. Energy from the central black hole is observed to flowinto this gas by means of jets, bubbles and sound waves. Cooling is thus offsetby heating. We discuss the mechanisms involved and observed in the X-raybrightest clusters and explore the closeness of the heating-cooling balance. Itis surprisingly tight on the cooling side when soft X-ray spectra are examined.Non-radiative cooling by mixing is suggested as a means to relax the apparentstrong lack of cooling. Nevertheless the heating and cooling must balance onaverage to better than 20 per cent.



Author: A.C. Fabian, J.S. Sanders Institute of Astronomy, Cambridge, UK

Source: https://arxiv.org/







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