Agn Feedback and Cooling Flows: the Failure of Simple Hydrodynamical Models

In recent years it has become increasingly clear that Active Galactic Nuclei, and radio-galaxies in particular, have an impact on large scale structure and galaxy formation. In principle, radiogalaxies are energetic enough to halt the cooling in the inner regions clusters, solving the cooling flow problem and explaining the high-mass truncation of the galaxy luminosity function. We explore this process through a series of high resolution, three dimensional hydrodynamic simulations of jetted active galaxies which act in response to cooling-mediated accretion of an ICM atmosphere. We find that such models are incapable of producing a long term balance of heating and cooling; catastrophic cooling can be delayed by the jet action but inevitably takes hold. At the heart of the failure of these models is the formation of a low density channel through which the jet can freely flow, carrying its energy out of the cooling core. While this obviously highlights the need to include physics beyond the ideal hydrodynamics considered here, it also underscores the importance of including jet dynamics in such models as opposed to the isotropically inflated bubble approach. Subject headings: cooling flows — galaxies: active — galaxies: formation — galaxies: jets — hydrodynamics — X-rays: galaxies: clusters