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Dual black holes in merger remnants - II. Spin evolution and gravitational recoil

Dotti, M. ; Volonteri, M. ; Perego, A. ; Colpi, M. ; Ruszkowski, M. ; Haardt, F.

In: Monthly Notices of the Royal Astronomical Society, 2010, vol. 402, no. 1, p. 682-690

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    Titre
    • Dual black holes in merger remnants - II. Spin evolution and gravitational recoil
    Auteur
    • Dotti, M.. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
    • Volonteri, M.. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
    • Perego, A.. Department of Physics, University of Basel, Klingerbergstr. 82, 4056 Basel, Switzerland
    • Colpi, M.. Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
    • Ruszkowski, M.. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
    • Haardt, F.. Dipartimento di Fisica e Matematica, Università dell'Insubria, Via Valleggio 11, 22100 Como, Italy
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Monthly Notices of the Royal Astronomical Society, 2010, vol. 402, no. 1, p. 682-690. Blackwell Publishing Ltd
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:299096
    Summary
    Using high-resolution hydrodynamical simulations, we explore the spin evolution of massive dual black holes orbiting inside a circumnuclear disc, relic of a gas-rich galaxy merger. The black holes spiral inwards from initially eccentric co- or counter-rotating coplanar orbits relative to the disc's rotation, and accrete gas that is carrying a net angular momentum. As the black hole mass grows, its spin changes in strength and direction due to its gravito-magnetic coupling with the small-scale accretion disc. We find that the black hole spins loose memory of their initial orientation, as accretion torques suffice to align the spins with the angular momentum of their orbit on a short time-scale (≲1-2 Myr). A residual off-set in the spin direction relative to the orbital angular momentum remains, at the level of ≲10° for the case of a cold disc, and ≲30° for a warmer disc. Alignment in a cooler disc is more effective due to the higher coherence of the accretion flow near each black hole that reflects the large-scale coherence of the disc's rotation. If the massive black holes coalesce preserving the spin directions set after formation of a Keplerian binary, the relic black hole resulting from their coalescence receives a relatively small gravitational recoil. The distribution of recoil velocities inferred from a simulated sample of massive black hole binaries has median , much smaller than the median resulting from an isotropic distribution of spins