Nonlinear Thermal Instability in Radio Mode AGN Feedback

Abstract

Substantial masses of cold gas found at the centers of cool core clusters are widely believed to be produced by thermally unstable cooling of the hot intracluster medium. A small part of the cold gas can power the radio jets that prevent much greater quantities of gas from cooling, sustaining a radio mode feedback cycle. I will argue that nonlinear hydrodynamic processes play a critical role in the onset of thermally unstable cooling, helping to define the necessary conditions for thermal instability. I will also show that uplift by radio lobes is a likely mechanism for driving this nonlinear thermal instability.