On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening
By N. Leigh, Aaron M. Geller, B. McKernan, K. Ford, M. Mac Low, J. Bellovary, Zoltán Haiman, Wladimir Lyra, J. Samsing, M. O’Dowd and 2 more. 2017
135 citations recorded by the source corpus.
We assess the contribution of dynamical hardening by direct three-body scattering interactions to the rate of stellar-mass black hole binary (BHB) mergers in galactic nuclei. We derive an analytic model for the single-binary encounter rate in a nucleus with spherical and disk components hosting a super-massive black hole (SMBH). We determine the total number of encounters $N_{\rm GW}$ needed to harden a BHB to the point that inspiral due to gravitational wave emission occurs before the next three-body scattering event. This is done independently for both the spherical and disk components. Using a Monte Carlo approach, we refine our calculations for $N_{\rm GW}$ to include gravitational wave emission between scattering events. For astrophysically plausible models we find that typically $N_{\rm GW} \lesssim$ 10. We find two separate regimes for the efficient dynamical hardening of BHBs: (1) spherical star clusters with high central densities, low velocity dispersions and no significant Keplerian component; and (2) migration traps in disks around SMBHs lacking any significant spherical stellar component in the vicinity of the migration trap, which is expected due to effective orbital inclination reduction of any spherical population by the disk. We also find a weak correlation between the ratio of the second-order velocity moment to velocity dispersion in galactic nuclei and the rate of BHB mergers, where this ratio is a proxy for the ratio between the rotation- and dispersion-supported components. Because disks enforce planar interactions that are efficient in hardening BHBs, particularly in migration traps, they have high merger rates that can contribute significantly to the rate of BHB mergers detected by the advanced Laser Interferometer Gravitational-Wave Observatory.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/9c22fffe51389f6e6e4b0961536f0ca0795f25d4
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In Astronomy and Astrophysics
Citations in the corpus
- Constraining Stellar-mass Black Hole Mergers in AGN Disks Detectable with LIGO (2017, background): “Thus, in order for fb to be moderately large in this channel, we require fg to be large, since otherwise the rate of ionizing encounters can ionize binaries (Leigh et al. 2017).”
- Black hole and neutron star mergers in galactic nuclei (2018, background): “This is because in the high-density, high-velocity dispersion environment of the Galactic Centre, triples should be rapidly destroyed due to dynamical interactions with single stars (e.g. Leigh et al. 2018).”