Long-Term Evolution of Massive Black Hole Binaries

By Milos Milosavljevic, D. Merritt. 2002

258 citations recorded by the source corpus.

The long-term evolution of massive black hole binaries at the centers of galaxies is studied in a variety of physical regimes, with the aim of resolving the "final parsec problem," i.e., how black hole binaries manage to shrink to separations at which emission of gravity waves becomes efficient. A binary ejects stars by the gravitational slingshot and carves out a loss cone in the host galaxy. Continued decay of the binary requires a refilling of the loss cone. We show that the standard treatment of loss cone refilling, derived for collisionally relaxed systems like globular clusters, can substantially underestimate the refilling rates in galactic nuclei. We derive expressions for nonequilibrium loss cone dynamics and calculate timescales for the decay of massive black hole binaries following galaxy mergers, obtaining significantly higher decay rates than heretofore. Even in the absence of two-body relaxation, decay of binaries can persist as a result of repeated ejection of stars returning to the nucleus on eccentric orbits. We show that this recycling of stars leads to a gradual, approximately logarithmic dependence of the binary binding energy on time. We derive an expression for the loss cone refilling induced by the Brownian motion of a black hole binary. We also show that numerical N-body experiments are not well suited to probe these mechanisms over long times as a result of spurious relaxation.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/cce026d51a68278071fd84f90ab83f60a0a94eb7

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In Astronomy and Astrophysics

Citations in the corpus

Efficient Merger of Binary Supermassive Black Holes in Nonaxisymmetric Galaxies (2006, methodology): “This behavior has been described quantitatively (Milosavljevic & Merritt 2003) on the basisof loss-cone theory: stars ejected by the binary are replaced in a time that scales as the two-body relaxation time, and the latt r increases roughly asN in a galaxy of fixed mass and size.”
Mass Deficits, Stalling Radii, and the Merger Histories of Elliptical Galaxies (2006, background): “It also allows for mechanisms that are not reproduced in the scattering experiments on which equations (1) and (2) are based, e.g., the ‘‘secondary slingshot’’ (Milosavljevic & Merritt 2003), or the effect of the changing nuclear density on the rate of supply of stars to the binary.”
Revised Rates of Stellar Disruption in Galactic Nuclei (2003, background): “Relaxation times in galactic nuclei are usually in excess of a Hubble time, particularly in the core galaxies (Faber et al. 1997), and it is not clear that the distributionof stars near the loss cone will have had time to reach a steady state in all of our galaxies (Milosavljevic & Merritt 2003).”
Massive black hole binary mergers within subparsec scale gas discs (2008, background): “10 and 11 the time-scale for orbital decay produced by scattering stars, tstellar, as estimated by Milosavljević & Merritt (2003), who c© 2008 RAS, MNRAS 000, 1–11 give tstellar ∼ 3 × 109yr a 0.1ahard 106 M⊙ M , (9) where ahard is the binary separation at the point where its orbital velocity is…”
Doing Science with eLISA: Astrophysics and Cosmology in the Millihertz Regime (2012, background): “ (cores) in their surface brightness proﬁles, i.e. lack of stars in their nuclei (Kormendy and Bender, 2009), and this missing light correlates with the mass of the central black hole (Merritt, 2006, Merritt et al., 2007). Thus, cores are evidence of binary black holes scouring out the nuclear stars”
Galaxy formation theory (2010, background): “…and Hernquist 1997; Milosavljevic and Merritt 2001), while the effective refilling of the loss cone by ejected stars returning oeccentric orbits (Milosavljevic and Merritt 2003; Sesana et al. 2007) and interactions with stars bound to the binary (Sesana et al. 2008) may enhance the rate of…”
Formation of z~6 Quasars from Hierarchical Galaxy Mergers (2006, background): “In a stellar environment, it has been argued that a binary hardens very slowly owing to an eventual depletion of stars that cause the binary to lose angular momentum (e.g., Begelman et al. 1980; Milosavljević & Merritt 2003).”
THE ASSEMBLY OF SUPERMASSIVE BLACK HOLES AT HIGH REDSHIFTS (2008, background): “The second assumption is valid for binaries in extremely gas-rich environments (see Milosavljevic & Merritt 2003 for a review), or in triaxial galaxies (Berczik et al. 2006).”
The evolution of massive black holes and their spins in their galactic hosts (2012, background): “…timescale (Armitage & Natarajan 2002); or the supply of star available for slingshot interaction may be replenished by star- tar encounters (Milosavljević & Merritt 2003; Yu 2002), or as aresult of the triaxial gravitational potential that one naturlly expects in galaxies forming from…”
A LARGE SYSTEMATIC SEARCH FOR CLOSE SUPERMASSIVE BINARY AND RAPIDLY RECOILING BLACK HOLES (2011, unknown): “However, it is still unknown whether this replenishment is possible via stellar dynamical processes (see, for example, discussions in Milosavljević & Merritt 2003; Berczik et al. 2006; Sesana, Haardt, & Madau 2007).”
Expected properties of the first gravitational wave signal detected with pulsar timing arrays (2015, background): “We simply assume that SBHBs coalesce efficiently following galaxy mergers, therefore bypassing the ‘last parsec problem’ (Milosavljević & Merritt 2003).”
The Afterglow of Massive Black Hole Coalescence (2004, background): “107M⊙, the gravitational slingshot ejection of stars is sufficient to guarantee coalescence in a Hubble time (Milosavljevíc & Merritt 2003).”
Intermediate and extreme mass-ratio inspirals—astrophysics, science applications and detection using LISA (2007, background): “In such conditions, relaxational processes are still controlling the EMRI rate, no matter how long the relaxation time is, but one cannot assume a steady-state rate of diffusion of stars onto orbits with small pericentres, as is often done in FP codes (see the discussion in [231], in the different c”
Massive Black Hole Binary Evolution (2004, methodology): “As N increases, the lower degree of collisionality allows the loss cone around the binary to remain partially unfilled and decay slows[200].”
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background (2023, background): “Galaxy mergers are the main drivers of hierarchical structure formation over cosmic time (Blumenthal et al. 1984) and lead to the formation of close massive–black-hole binaries long after the mergers (Begelman et al. 1980; Milosavljević & Merritt 2003).”