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Black hole mergers: do gas discs lead to spin alignment?
被引:36
作者:
Lodato, Giuseppe
[1
]
Gerosa, Davide
[1
,2
]
机构:
[1] Univ Milan, Dipartimento Fis, I-20133 Milan, Italy
[2] Univ Mississippi, Dept Phys & Astron, University, MS 38677 USA
关键词:
accretion;
accretion discs;
black hole physics;
galaxies: evolution;
galaxies: nuclei;
ACTIVE GALACTIC NUCLEI;
FINAL PARSEC PROBLEM;
DIGITAL SKY SURVEY;
ACCRETION DISCS;
Z-GREATER-THAN-5.7;
QUASARS;
SDSS J092712.65+294344.0;
ADDITIONAL QUASARS;
BINARY;
CANDIDATE;
EVOLUTION;
D O I:
10.1093/mnrasl/sls018
中图分类号:
P1 [天文学];
学科分类号:
0704 ;
摘要:
In this Letter, we revisit arguments suggesting that the Bardeen-Petterson effect can coalign the spins of a central supermassive black hole binary accreting from a circumbinary (or circumnuclear) gas disc. We improve on previous estimates by adding the dependence on system parameters and noting that the non-linear nature of warp propagation in a thin viscous disc affects alignment. This reduces the disc's ability to communicate the warp, and can severely reduce the effectiveness of disc-assisted spin alignment. We test our predictions with a Monte Carlo realization of random misalignments and accretion rates, and we find that the outcome depends strongly on the spin magnitude. We estimate a generous upper limit to the probability of alignment by making assumptions which favour it throughout. Even with these assumptions, about 40 per cent of black holes with a greater than or similar to 0.5 do not have time to align with the disc. If the residual misalignment is not small and it is maintained down to the final coalescence phase, this can give a powerful recoil velocity to the merged hole. Highly spinning black holes are thus more likely being subject to strong recoils, the occurrence of which is currently debated.
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页码:L30 / L34
页数:5
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