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|Title:||Retrograde accretion and merging supermassive black holes|
|Authors:||Cossins, P. J.|
King, A. R.
Pringle, J. E.
|Publisher:||Oxford University Press (OUP)|
|Citation:||Monthly Notices of the Royal Astronomical Society , 2011, 412 (3), pp. 1591-1598|
|Abstract:||We investigate whether a circumbinary gas disc can coalesce a supermassive black hole binary system in the centre of a galaxy. This is known to be problematic for a prograde disc. We show that in contrast, interaction with a retrograde circumbinary disc is considerably more effective in shrinking the binary because there are no orbital resonances. The binary directly absorbs negative angular momentum from the circumbinary disc by capturing gas into a disc around the secondary black hole, or discs around both holes if the binary mass ratio is close to unity. In many cases the binary orbit becomes eccentric, shortening the pericentre distance as the eccentricity grows. In all cases the binary coalesces once it has absorbed the angular momentum of a gas mass comparable to that of the secondary black hole. Importantly, this conclusion is unaffected even if the gas inflow rate through the disc is formally super-Eddington for either hole. The coalescence time-scale is therefore always Graphic, where M2 is the secondary black hole mass and Graphic the inflow rate through the circumbinary disc.|
|Rights:||This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2011 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Deposited with reference to the publisher’s archiving policy available on the SHERPA/RoMEO website.|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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