AAS 205th Meeting, 9-13 January 2005
Session 145 Intergalactic Media
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[145.08] Cooling Flows and Heating Shocks in Hercules A

D.C. Hambrick (Harvey Mudd College), P.E.J. Nulsen (CfA), B.R. MacNamara, D.A. Rafferty, L. Birzan (Ohio University)

Hercules A is a radio-bright cooling-flow cluster at z=0.154. A 2001 Chandra observation shows a break in surface brightness about 1' (160 kpc) from the cluster center. This feature is interpreted as a shock in the intracluster medium, powered ultimately by the AGN of the cluster's central galaxy. Using a simple hydrodynamical model, the Mach number of the shock is found to be 1.6. The energy and age of the shock are also calculated from the model, and found to be 3 \times 1061 ergs and 6 \times 107 years, respectively. The heating efficiency of the shock is found to be of order 1/2, so this energy is sufficient to account for the X-ray luminosity of the cluster if similar shocks occur every 109 years. Other heating sources such as gas mixing and bubble enthalpy are explored within the context of the same model, but are found to be relatively unimportant for Hercules A. Data for the 6 known cooling-flow systems with shocks are gathered and compared.

DCH was supported by NSF REU award #9731923.

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