Conclusions

• Radio sources displace the X-ray-emitting gas in the centers of cooling flows, creating cavities or “bubbles.”

• In all clusters observed so far, there is no evidence that the radio sources are strongly shocking the ICM. The bright shells are cool, not hot. Weak shocks may have occurred in the past, creating the dense shells

• The X-ray gas pressures derived from the shells surrounding the bubbles are ~ 10x higher than the radio equipartition pressures. Problems with equipartition assumptions, or additional contributors to pressure in bubbles, such as very hot, diffuse, thermal gas?