Mergers of Unequal Mass Galaxies: Supermassive Black Hole Binary Evolution and Structure of Merger Remnants

Abstract

Galaxy centers are residing places for Super Massive Black Holes (SMBHs). Galaxy mergers bring SMBHs close together to form gravitationally bound binary systems which, if able to coalesce in less than a Hubble time, would be one of the most promising sources of gravitational waves for the Laser Interferometer Space Antenna (LISA). In spherical galaxy models, SMBH binaries stall at a separation of approximately one parsec, leading to the "final parsec problem" (FPP). On the other hand, it has been shown that merger-induced triaxiality of the remnant in equal-mass mergers is capable of supporting a constant supply of stars on so-called centrophilic orbits that interact with the binary and thus avoid the FPP. In this paper, using a set of direct N-body simulations of mergers of initially spherically symmetric galaxies with different mass ratios, we show that the merger-induced triaxiality is able to drive unequal-mass SMBH binaries to coalescence. The binary hardening rates are high and depend only weakly on the mass ratios of SMBHs for a wide range of mass ratios q. The hardening rates are significantly higher for galaxies having steep cusps in comparison with those having shallow cups at centers. The evolution of the binary SMBH leads to relatively shallower inner slopes at the centers of the merger remnants. The stellar mass displaced by the SMBH binary on its way to coalescence is ~ 1-5 times the combined mass of binary SMBHs. The coalescence times for SMBH binary with mass ~ million solar masses are less than 1 Gyr and for those at the upper end of SMBH masses (~ billion solar masses) are 1-2 Gyr for less eccentric binaries whereas less than 1 Gyr for highly eccentric binaries. SMBH binaries are thus expected to be promising sources of gravitational waves at low and high redshifts.

Accepted for publication in the Astrophysical Journal (ApJ). 14 pages, 8 figures

References in corpus (13)

• The SAURON project -- IX. A kinematic classification for early-type galaxies
• Massive black hole binary mergers within sub-pc scale gas discs
• The influence of gas on the structure of merger remnants
• Dissipation and Extra Light in Galactic Nuclei: II. 'Cusp' Ellipticals
• Ejection of Supermassive Black Holes from Galaxy Cores
• The imprint of massive black hole formation models on the LISA data stream
• Performance Analysis of Direct N-Body Algorithms on Special-Purpose Supercomputers
• Dissipation and Extra Light in Galactic Nuclei: III. 'Core' Ellipticals and 'Missing' Light
• Self consistent model for the evolution of eccentric massive black hole binaries in stellar environments: implications for gravitational wave observations
• Growing Massive Black Hole Pairs in Minor Mergers of Disk Galaxies
• Dynamics of galaxy cores and supermassive black holes
• Long-Term Evolution of Massive Black Hole Binaries. III. Binary Evolution in Collisional Nuclei
• Massive perturbers and the efficient merger of binary massive black holes

Cited by in corpus (74)

• Science with the space-based interferometer LISA. V: Extreme mass-ratio inspirals
• The Quest for Dual and Binary Supermassive Black Holes: A Multi-Messenger View
• Massive binary black holes in galactic nuclei and their path to coalescence
• Gravitational-wave Limits from Pulsar Timing Constrain Supermassive Black Hole Evolution
• Supermassive Black Hole Binary Evolution in Axisymmetric Galaxies: the final parsec problem is not a problem
• The final-parsec problem in the collisionless limit
• Post-Newtonian Evolution of Massive Black Hole Triplets in Galactic Nuclei: IV. Implications for LISA
• Scattering experiments meet N-body I: a practical recipe for the evolution of massive black hole binaries in stellar environments
• Prospects for gravitational-wave detection and supermassive black hole astrophysics with pulsar timing arrays
• Swift coalescence of supermassive black holes in cosmological mergers of massive galaxies
• Binary super-massive black hole environments diminish the gravitational-wave signal in the pulsar timing band
• Post-Newtonian evolution of massive black hole triplets in galactic nuclei -- III. A robust lower limit to the nHz stochastic background of gravitational waves
• Galaxy Rotation and Rapid Supermassive Black Hole Binary Coalescence
• The final-parsec problem in non-spherical galaxies revisited
• Detection of eccentric supermassive black hole binaries with pulsar timing arrays: Signal-to-noise ratio calculations
• Post-Newtonian dynamical modeling of supermassive black holes in galactic-scale simulations
• Orbital Decay of Supermassive Black Hole Binaries in Clumpy Multiphase Merger Remnants
• Post-Newtonian Evolution of Massive Black Hole Triplets in Galactic Nuclei: I. Numerical Implementation and Tests
• Formation and Hardening of Supermassive Black Hole Binaries in Minor Mergers of Disk Galaxies
• The ATLAS3D Project -- XXIII. Angular momentum and nuclear surface brightness profiles
• Detecting eccentric supermassive black hole binaries with pulsar timing arrays: Resolvable source strategies
• Supermassive black hole pairs in clumpy galaxies at high redshift: delayed binary formation and concurrent mass growth
• Searching for Binary Supermassive Black Holes via Variable Broad Emission Line Shifts: Low Binary Fraction
• Eccentricity evolution of massive black hole binaries from formation to coalescence
• The puzzling case of the radio-loud QSO 3C 186: a gravitational wave recoiling black hole in a young radio source?
• Missing black holes in brightest cluster galaxies as evidence for the occurrence of superkicks in nature
• Dynamical Evolution and Merger Time-scales of LISA Massive Black Hole Binaries in Disk Galaxy Mergers
• Boosted Tidal Disruption by Massive Black Hole Binaries During Galaxy Mergers FROM The View of N-Body Simulation
• Galaxy Rotation and Supermassive Black Hole Binary Evolution
• The Three-Phase Evolution of the Milky Way
• Emission Signatures from Sub-parsec Binary Supermassive Black Holes I: Diagnostic Power of Broad Emission Lines
• Supermassive Black Hole Binaries: The Search Continues
• The Link Between Ejected Stars, Hardening and Eccentricity Growth of Super Massive Black Holes in Galactic Nuclei
• Accretion and Orbital Inspiral in Gas-Assisted Supermassive Black Hole Binary Mergers
• Supermassive black holes coalescence mediated by massive perturbers: implications for gravitational waves emission and nuclear cluster formation
• On the eccentricity evolution of massive black hole binaries in stellar backgrounds
• The lifetime of binary black holes in Sérsic galaxy models
• Pulsar timing array signals induced by black hole binaries in relativistic eccentric orbits
• Inward Bound: The incredible journey of massive black holes as they pair and merge; I. The effect of mass ratio in flattened rotating galactic nuclei
• An Improved Test of the Binary Black Hole Hypothesis for Quasars with Double-peaked Broad Balmer Lines
• The recoiling black hole candidate 3C 186: spatially-resolved quasar feedback and further evidence of a blue-shifted broad line region
• Gravitational Wave Driven Mergers and Coalescence Time of Supermassive Black Holes
• KETJU -- resolving small-scale supermassive black hole dynamics in GADGET-4
• Star cluster disruption by a massive black hole binary
• Extremely efficient mergers of intermediate mass black hole binaries in nucleated dwarf galaxies
• Modelling the accretion and feedback of supermassive black hole binaries in gas-rich galaxy mergers
• Ultramassive Black Hole Coalescence
• Dynamical evolution of massive black holes in galactic-scale N-body simulations - introducing the regularized tree code "rVINE"
• An Amusing Look at the Host of the Periodic Nuclear Transient ASASSN-14ko Reveals a Second AGN
• Direct n-body simulations of tidal disruption rate evolution in unequal-mass galaxy mergers
• Optical follow-up of the tick-tock massive black hole binary candidate
• The kinematic signature of the inspiral phase of massive binary black holes
• Multiple regimes and coalescence timescales for massive black hole pairs ; the critical role of galaxy formation physics
• Morphological evidence for a past minor merger in the Seyfert galaxy NGC 1068
• Evolution of supermassive black hole binaries and tidal disruption rates in nonspherical galactic nuclei
• Dynamics of supermassive black hole triples in the ROMULUS25 cosmological simulation
• Classification of Stellar Orbits in Axisymmetric Galaxies
• Merging timescale for supermassive black hole binary in interacting galaxy NGC 6240
• SDSS J154751.94+025550 with double-peaked broad Hβbut single-peaked broad Hα: a candidate for central binary black hole system?
• NOEMA observations support a recoiling black hole in 3C186
• RABBITS -- II. The impact of AGN feedback on coalescing supermassive black holes in disc and elliptical galaxy mergers
• Connecting traces of galaxy evolution: the missing core mass -- morphological fine structure relation
• A Massive, Clumpy Molecular Gas Distribution and Displaced AGN in Zw 3146
• Evolution of binary supermassive black holes and the final-parsec problem
• Astrophysics with the Laser Interferometer Space Antenna
• Where Have All the Little Red Dots Gone? Supermassive Black Hole Binary Dynamics and its Impact on Galaxy Properties
• Properties of loss cone stars in a cosmological galaxy merger remnant
• Merger Criteria of Multiple Massive Black Holes and the Impact on the Host Galaxy
• Detection of eccentric close-binary supermassive black holes with incomplete interferometric data
• A Massive Dense Gas Cloud close to the Nucleus of the Seyfert galaxy NGC 1068
• The Stellar Orbital Structure in Axisymmetric Galaxy Models with Supermassive Black Hole Binaries
• The Effect of Impact Parameters on the Formation of Massive Black Hole Binaries in Galactic Mergers
• Intermediate Mass Black Hole Binary Evolution in Nuclear Star Clusters: the effect of the stellar mass black hole population
• First Light And Reionization Epoch Simulations (FLARES) -- XIX: Supermassive black hole mergers in the early Universe and their environmental dependence