2003/10/07 by P. E. J. Nulsen, Paul Nulsen, Nulsen, Paul
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0310195
4 pages, in proceedings "The Riddle of Cooling Flows in Galaxies and Clusters of Galaxies," held at Charlottesville, VA, May 31 - June 4, 2003, eds T.H. Reiprich, J.C. Kempner, N. Soker, http://www.astro.virginia.edu/coolflow/
arxiv created 2003/10/07 · openalex publication_date 2003/10/07 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The process that prevents the deposition of cooled gas in cooling flows must rely on feedback in order to maintain gas with short cooling times, while preventing the bulk of the gas from cooling to low temperatures. The primary candidate for the feedback mechanism is the accretion of cooled and cooling gas by an active galactic nucleus (AGN). Despite some difficulties with this model, the high incidence of central radio sources in cooling flows and the common occurrence of radio lobe cavities, together, support this view. The Bondi accretion rate for the intracluster gas onto the AGN depends on the gas properties only through its specific entropy and that is governed directly by competition between heating and cooling. This provides a viable link for the feedback process. It is argued that the mass accreted between outbursts by the central AGN is only sensitive to the mass of the black hole and the gas temperature. Bondi accretion by an AGN leads to a simple expression for outburst energy that can be tested against observations.