AGN Feedback and Cooling Flows: Problems with Simple Hydrodynamical Models

J. C. Vernaleo and C. S. Reynolds (University of Maryland)


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, radio-galaxies are energetic enough to halt the cooling of the virialized intracluster medium (ICM) in the inner regions of galaxy 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 that act in response to cooling-mediated accretion of an ICM atmosphere. We find that our 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. It is possible that this failure is due to an over-simplified treatment of the fast jet (which may underestimate the ``dentist drill'' effect). However, it seems likely that additional complexity (large-angle jet precession or ICM turbulence) or additional physics (magnetohydrodynamic effects and plasma transport processes) is required to produce a spatial distribution of jet heating that can prevent catastrophic cooling. This work also underscores the importance of including jet dynamics in any feedback model as opposed to the isotropically inflated bubble approach taken in some previous works.

PDF file of paper with high resolution figures.


Permission is granted to download and use these animations for educational or scientific purposes as long as you properly credit us. Please reference the paper: Vernaleo & Reynolds, 2006 (astro-ph/0511501, ApJ, 645 83). Also please refer to the paper for details and discussion.

Movies are available as animated gifs and mpegs (DivX 4 encoded avi files, so you may need additional software to view on Windows or Mac OS X).

Single Jet: Density gif mpeg; Entropy gif mpeg
Delayed Feedback (inner regions): Density gif mpeg; Entropy gif mpeg
Feedback with rotation (inner regions): Density gif mpeg; Entropy gif mpeg