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Title: Misaligned gas discs around eccentric black hole binaries and implications for the final-parsec problem
Authors: Aly, Hossam
Dehnen, Walter
Nixon, Christopher James
King, Andrew
First Published: 1-May-2015
Publisher: Oxford University Press (OUP)
Citation: Monthly Notices of the Royal Astronomical Society, 2015, 449 (1), pp. 65-76 (12)
Abstract: We investigate the evolution of low mass (M[Subscript: d]/M[Subscript: b] = 0.005) misaligned gaseous discs around eccentric supermassive black hole (SMBH) binaries. These are expected to form from randomly oriented accretion events on to a SMBH binary formed in a galaxy merger. When expanding the interaction terms between the binary and a circular ring to quadrupole order and averaging over the binary orbit, we expect four non-precessing disc orientations: aligned or counter-aligned with the binary, or polar orbits around the binary eccentricity vector with either sense of rotation. All other orientations precess around either of these, with the polar precession dominating for high eccentricity. These expectations are borne out by smoothed particle hydrodynamics simulations of initially misaligned viscous circumbinary discs, resulting in the formation of polar rings around highly eccentric binaries in contrast to the coplanar discs around circular binaries. Moreover, we observe disc tearing and violent interactions between differentially precessing rings in the disc significantly disrupting the disc structure and causing gas to fall on to the binary with little angular momentum. While accretion from a polar disc may not promote SMBH binary coalescence (solving the ‘final-parsec problem’), ejection of this infalling low-angular momentum material via gravitational slingshot is a possible mechanism to reduce the binary separation. Moreover, this process acts on dynamical rather than viscous time-scales, and so is much faster.
DOI Link: 10.1093/mnras/stv128
ISSN: 0035-8711
eISSN: 1365-2966
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Archived with reference to the Publisher's author self-archiving policy, available at
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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