The Cooling Flow “Problem”

• Where does the cooling gas go?

• Central cD galaxies in cooling flows do emit blue light and exhibit massive star formation, however the star formation accounts for only ~ 1--10% of the expected gas derived from the X-ray predictions (as measured from Einstein, ROSAT, and ASCA)

• Both Chandra and XMM-Newton have revealed an apparent lack of the expected quantities of cooler gas below about kT < 1- 2 keV (~107 K)

• Radio sources are possible heaters (but not by strong shocks).