case western reserve university



Cluster Cooling Flows in the Chandra Era

Brian McNamara (Ohio U)

The giant cD galaxies located at the centers of galaxy clusters are often the sites of massive bursts of star formation. These starbursts occur preferentially in so-called cooling flow clusters, where the hot, X-ray-emitting intracluster medium appears to cool at rates of several hundred solar masses per year. X-ray images of cooling flow clusters taken with the Chandra X-ray Observatory show that the gas is cooling at rates that are considerably smaller than those from earlier missions. In addition, the Chandra imaging shows that cluster cores can be remarkably complex. I will present exciting new evidence that radio sources have a major impact on the structure of the intracluster medium. In some instances the radio sources are displacing the gas, leaving cavities supported by magnetic fields, cosmic rays, and perhaps a dilute, hot plasma. In addition, radio-faint, ``ghost'' cavities are seen in some clusters which may be relics of earlier radio outbursts. Radio sources may be capable of substantially reducing or quenching cooling flows, while at the same time triggering bursts of star formation in the residual cooling gas.