The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei. II. Black Hole Merging in a Nuclear Gas Disk

By A. Escala, R. Larson, Paolo De Coppi, Diego Mardones. 2003

346 citations recorded by the source corpus.

Using high-resolution SPH numerical simulations, we investigate the effects of gas on the in-spiral and merger of a massive black hole binary. This study is motivated by the very massive nuclear gas disks observed in the central regions of merging galaxies. Here we present results that expand on the treatment in a previous work by studying models in which the gas is in a disk. We run a variety of models, ranging from simulations with a relatively smooth gas disk to cases in which the gas has a more clumpy spatial distribution. We also vary the inclination angle between the plane of the binary and the plane of the disk, and the mass ratio between the MBHs and the gaseous disk. We find that, as in our previous work, in the early evolution of the system the binary separation diminishes mainly due to dynamical friction exerted by the background gas, and in the later stages the gaseous medium responds by forming an ellipsoidal density enhancement whose axis lags behind the binary axis. This offset produces a gravitational torque on the binary that causes continuing loss of angular momentum and is able to reduce the separation to distances at which gravitational radiation is efficient. The main difference is that between these two regimes we now find a new transition regime that was not apparent in our previous paper, in which the evolution is temporarily slowed down when neither of these mechanisms is fully effective. In the variety of simulations that we perform, we find that the coalescence timescale for the MBH binary varies between 5 × 106 and 2.5 × 107 yr for typical ULIRGs. For MBHs that satisfy the observed "m-σc" relation, our simulations suggest that in a merger of galaxies that have at least 1% of their total mass in gas, the MBHs will coalesce soon after the galaxies merge.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/aa63728a06acd135beed441273b626d6f086a659

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Quasars at z = 6: The Survival of the Fittest (2006, background): “Another possibility is that gas processes, rather than three-body interactions with stars or DM, may induce MBH binaries to shrink rapidly and coalesce (e.g. Mayer et al. (2006); Dotti et al. (2006); Escala et al. (2004); Liu et al. (2003); Armitage & Natarajan (2005); Gould & Rix (2000)).”
Formation and Evolution of Compact-object Binaries in AGN Disks (2019, background): “In this manner, gas dynamical friction hardens binaries (Escala et al. 2004; Kim & Kim 2007; Baruteau et al. 2011) and damps the velocity dispersion of BHs and stars (Papaloizou & Larwood 2000; Tanaka et al. 2002) in the disk.”
The NANOGrav 15 yr Data Set: Constraints on Supermassive Black Hole Binaries from the Gravitational-wave Background (2023, background): “Similarly, in gas-rich systems, circumbinary gas disks can also catalyze the binary evolution (Escala et al. 2005; Dotti et al. 2007; Haiman et al. 2009), but the efficiency of this process or whether the gas pushes the binary inward or outward is still unclear (Moody et al. 2019; Muñoz et al.…”
THE LUMINOSITY FUNCTION OF FERMI-DETECTED FLAT-SPECTRUM RADIO QUASARS (2011, background): “5 (Romani 2006), and it is plausible that major mergers, more frequently experienced in the early universe, might preferentially produce maximally rotating black holes (e.g., see Escala et al. 2004; Dotti et al. 2007).”
Phantom: A Smoothed Particle Hydrodynamics and Magnetohydrodynamics Code for Astrophysics (2017, methodology): “PASA (2018) doi:10.1017/pas.2018.xxx It has been used many times to test SPH codes with self-gravity, e.g. Hernquist & Katz (1989), Steinmetz & Mueller (1993), Thacker et al. (2000), Escala et al. (2004) and many others.”
THE POPULATION OF VISCOSITY- AND GRAVITATIONAL WAVE-DRIVEN SUPERMASSIVE BLACK HOLE BINARIES AMONG LUMINOUS ACTIVE GALACTIC NUCLEI (2009, background): “…the circumbinary gas, delivered to the nucleus in galactic mergers, can both play a catalyst role in driving rapid SMBHB coalescence (Begelman et al. 1980; Gould & Rix 2000; Escala et al. 2004), and could also accrete onto one or both SMBHs, accounting for bright emission during the orbital decay.”
Black hole mergers: can gas discs solve the ‘final parsec’ problem? (2009, background): “0.1 pc by dynamical friction against the stellar and gaseous background (Escala et al. 2005; Dotti et al. 2006).”
A LARGE SYSTEMATIC SEARCH FOR CLOSE SUPERMASSIVE BINARY AND RAPIDLY RECOILING BLACK HOLES (2011, neutral): “…of the binary orbit have been explored in an effort to solve this problem, most notably drag by a large gaseous reservoir (e.g. a disk) or torques on a binary at short separations by a circumbinary disk(e.g. Escala et al. 2004; Dotti et al. 2007, 2009b; Cuadra et al. 2009; Lodato et al. 2009).”
Journey to the MBH-σ relation: the fate of low-mass black holes in the Universe (2009, methodology): “The available simulations (Escala et al. 2004; Dotti, Colpi & Haardt 2006; Mayer et al. 2007) show that the binary can shrink to about parsec or slightly subparsec scale by dynamical friction against gas.”
THE EVOLUTION OF SWIFT/BAT BLAZARS AND THE ORIGIN OF THE MeV BACKGROUND (2009, background): “These events can produce a maximally rotating black hole by coalescence of the two black holes (Escala et al. 2004, 2005; Dotti et al. 2007) and by triggering large-gas accretion events that spin up the hole (Barnes & Hernquist 1996; Escala 2007; Bogdanović et al. 2007).”
Efficient Merger of Binary Supermassive Black Holes in Nonaxisymmetric Galaxies (2006, background): “In addition, gas is a significant component of disk galaxies and, in many mergers, the final hardening of the binary would be accelerated by gas-dynamical torques (Escala et al. 2005; Dotti et al. 2005).”
An Eccentric Circumbinary Accretion Disk and the Detection of Binary Massive Black Holes (2006, methodology): “Previous numerical simulations of circumbinary disks based on the smoothed particle hydrodynamics method (Artymowicz & Lubow 1994; Escala et al. 2005) and grid-based hydrodynamics with explicit bulk viscosity (Günther & Kley 2002) suggest that the surface density of a circumbinary disk drops…”
Direct Cosmological Simulations of the Growth of Black Holes and Galaxies (2007, background): “In a stellar environment, it has been argued that the binary hardens only very slowly (Begelman et al. 1980; Milosavljević & Merritt 2003), while in gaseous environments binaries may coalesce rapidly owing to strong dynamical frictionwith the gas (Makino&Funato 2004; Escala et al. 2004).”
Gravitational waves from resolvable massive black hole binary systems and observations with Pulsar Timing Arrays (2008, background): “If the binary evolution is gas–driven, typical hardening timescales are expected to be shorter than 108 yr (Escala et al. 2005, Dotti et al. 2006).”
Massive Black Hole Binary Evolution (2004, background): “ma to escape the SBH reduces the likelihood that large quantities of virialized gas would remain enmeshed with the binary’s orbit long enough to aﬀect its dynamical evolution. Recently, Escala et al. [40] carried out smoothed particle hydrodynamical (SPH) simulations of binary point masses interacti”
An analytic model of angular momentum transport by gravitational torques: from galaxies to massive black holes (2010, background): “Recently, numerical simulations using a variety of techniques have been able to follow the inflow of gas to smaller scales in galaxies (Escala et al. 2004; Escala 2007; Mayer et al. 2007; Wise et al. 2008; Levine et al. 2008; Hopkins & Quataert 2010a).”
Limiting eccentricity of subparsec massive black hole binaries surrounded by self-gravitating gas discs (2011, background): “…inside the massive gaseous nuclear disc resulting upon collision, the two BHs continue to lose orbital energy and angular momentum under the large-scale action of gas-dynamical friction, and end up forming a circular Keplerian binary, on parsec scales (Escala et al. 2005; Dotti et al. 2007, 2009).”