Cooling by heat conduction inside magnetic flux loops and the moderate cluster cooling-flow model

I study non-radiative cooling of X-ray-emitting gas via heat conduction along magnetic field lines inside magnetic flux loops in cooling-flow clusters of galaxies. I find that such heat conduction can reduce the fraction of energy radiated in the X-ray band by a factor of ∼1.5-2. This non-radiative cooling joins two other proposed non-radiative cooling processes, which can be more efficient. These are mixing of cold and hot gas, and heat conduction initiated by magnetic field reconnection between hot and cold gas. These processes when incorporated into the moderate cooling-flow model - where the effective age of the cooling-flow region since the last major heating event is assumed to be much shorter than the cluster age, hence the mass cooling rate is substantially reduced - lead to a general cooling-flow model with the following ingredients. (1) Cooling flow does occur, but with a mass cooling rate ∼10 times lower than in older versions of the cooling-flow model. Namely, heating occurs such that the effective age of the cooling flow is far below the cluster age, but the heating cannot prevent cooling altogether. (2) The cooling-flow region is in non-steady-state evolution. (3) Non-radiative cooling of X-ray-emitting gas can bring the model to much better agreement with observations. (4) The general behaviour of the cooling-flow gas, and in particular the role played by magnetic fields, make the intracluster medium in cooling-flow clusters similar in some respects to the active solar corona.