Christopher J. Nixon (Leicester), Andrew R. King (Leicester) and Daniel J. Price (Monash)

full text pdf (2.0Mb), accepted to MNRAS on 24/02/12 (arXiv:1203.0008)


Accretion in the nuclei of active galaxies may occur chaotically. This can produce accretion discs which are counter-rotating or strongly misaligned with respect to the spin of the central supermassive black hole (SMBH), or the axis of a close SMBH binary. Accordingly we consider the cancellation of angular momentum in accretion discs with a significant change of plane (tilt) between inner and outer parts. We estimate analytically the maximum accretion rate through such discs and compare this with the results of Smoothed Particle Hydrodynamics (SPH) simulations. These suggest that accretion rates on to supermassive black holes may be larger by factors >~ 100 if the disc is internally tilted in this way rather than planar. This offers a natural way of driving the rapid growth of supermassive black holes, and the coalescence of SMBH binaries.

New Scientist Article

20th March 2012: "Hungry black holes eat two courses at once"


theta = 150 (3D) from Chris Nixon on Vimeo.

3D rendering (using splash) showing evolution of counter-rotating discs (150 degree inclination angle). Cancellation of angular momentum between the two discs leads to the formation of an inner "fallback" disc at a smaller radius.

theta = 150 from Chris Nixon on Vimeo.

As above, but showing column density.

theta = 150 (adiabatic) from Chris Nixon on Vimeo.

In this case the discs are not allowed to cool, i.e., they are treated as adiabatic. In this case a chaotic accretion ensues.

theta = 180 from Chris Nixon on Vimeo.

Exactly retrograde. Still, angular momentum cancellation is not perfect and an inner disc forms.

theta = 120 from Chris Nixon on Vimeo.

120 degree inclination.

theta = 90 from Chris Nixon on Vimeo.

90 degree inclination.

theta = 60 from Chris Nixon on Vimeo.

60 degree inclination.

theta = 30 from Chris Nixon on Vimeo.

30 degree inclination.

theta = 0 from Chris Nixon on Vimeo.

The control case.

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