Isotropic Heating of Cool-Core Galaxy Cluster via Reccurrent, Rapidly Reorienting AGN Jets

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• Arif Babul (University of Victoria)
• Thursday 15 November 2012, 13:00-14:00
• Physics Library, Physics West Building.

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AGN jets are more than capable of staving of catastrophic cooling of the intracluster medium (ICM) in the cores of cool-core clusters. However, preventing catastrophic cooling requires the ICM to be heated nearly isotropically. Narrow bipolar jets are extremely inefficient at heating the gas in the transverse direction. Recent detailed studies of individual cool-core clusters show that successive generations of jet-lobe-bubbles are offset, often significantly, in the angular direction on the sky. Since the spin and the jet axises are one and the same, we interpret this as evidence that the spin axis of the supermassive black hole (SMBH) at the centers of these clusters is prone to change directions on timescales shorter than the gas cooling time in the cores. We argue that due to the extant conditions in the cluster cores, the SMB Hs experience short stochastic episodes of enhanced accretion via thin, typically misaligned, accretion disks that, in turn, cause the black hole’s spin axis to slew and change direction rapidly. Our model not only explains how AGN byproducts can end up tracing a nearly isotropic angular distribution about the cluster center but also explains how AGN jets effect isotropic heating. Since SMB Hs that host thin accretions will manifest as quasars, our model predicts that to the extent that the characteristics of the cluster population (i.e. the fraction of strong cool-core clusters, etc.) are comparable to those in the local universe, we expect a quasar at the centres of 1-2 systems within z < 0.5.

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