Isotropic heating of galaxy cluster cores via rapidly reorienting active galactic nucleus jets

Babul, Arif and Sharma, Prateek and Reynolds, Christopher S (2013) Isotropic heating of galaxy cluster cores via rapidly reorienting active galactic nucleus jets. In: Astrophysical Journal, 768 (1). 11_1-11_8.

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Abstract

Active galactic nucleus (AGN) jets carry more than sufficient energy to stave off catastrophic cooling of the intracluster medium (ICM) in the cores of cool-core clusters. However, in order to prevent catastrophic cooling, the ICM must be heated in a near-isotropic fashion and narrow bipolar jets with P-jet = 10(44-45) erg s(-1), typical of radio AGNs at cluster centers, are inefficient in heating the gas in the transverse direction to the jets. We argue that due to existent conditions in cluster cores, the supermassive black holes (SMBHs) will, in addition to accreting gas via radiatively inefficient flows, experience short stochastic episodes of enhanced accretion via thin disks. In general, the orientation of these accretion disks will be misaligned with the spin axis of the black holes (BHs) and the ensuing torques will cause the BH's spin axis (and therefore the jet axis) to slew and rapidly change direction. This model not only explains recent observations showing successive generations of jet-lobes-bubbles in individual cool-core clusters that are offset from each other in the angular direction with respect to the cluster center, but also shows that AGN jets can heat the cluster core nearly isotropically on the gas cooling timescale. Our model does require that the SMBHs at the centers of cool-core clusters be spinning relatively slowly. Torques from individual misaligned disks are ineffective at tilting rapidly spinning BHs by more than a few degrees. Additionally, since SMBHs that host thin accretion disks will manifest as quasars, we predict that roughly 1-2 rich clusters within z < 0.5 should have quasars at their centers.

Item Type:	Journal Article
Publication:	Astrophysical Journal
Publisher:	IOP Publishing Ltd
Additional Information:	Copyright of this article belongs to IOP Publishing Ltd.
Keywords:	Accretion, Accretion Disks; Black Hole Physics; Galaxies: Active; Galaxies: Clusters: Intracluster Medium; Galaxies: Jets; X-Rays: Galaxies: Clusters
Department/Centre:	Division of Physical & Mathematical Sciences > Joint Astronomy Programme Division of Physical & Mathematical Sciences > Physics
Date Deposited:	11 Jun 2013 07:41
Last Modified:	11 Jun 2013 07:41
URI:	http://eprints.iisc.ac.in/id/eprint/46636

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