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Mergers of Unequal Mass Galaxies: Supermassive Black Hole Binary Evolution and Structure of Merger Remnants
Cosmology and Nongalactic Astrophysics · Submitted 9 Feb 2012
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim 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.
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The abstract, sentence by sentence
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.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Galaxy centers are residing places for Super Massive Black Holes (SMBHs). | background 1.00 | 0.04 | 0.01 | asserted 1.00 |
| s1 | 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). | background 1.00 | 0.04 | 0.03 | hedged possibility 0.62 |
| s2 | In spherical galaxy models, SMBH binaries stall at a separation of approximately one parsec, leading to the "final parsec problem" (FPP). | background 0.92 | 0.05 | 0.02 | asserted 0.99 |
| s3 | 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. | background 0.99 | 0.04 | 0.04 | asserted 0.95 |
| s4 | 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. | contribution 0.95 | 0.97 | 0.91 | asserted 1.00 |
| s5 | The binary hardening rates are high and depend only weakly on the mass ratios of SMBHs for a wide range of mass ratios q. | result 1.00 | 0.92 | 0.11 | asserted 1.00 |
| s6 | The hardening rates are significantly higher for galaxies having steep cusps in comparison with those having shallow cups at centers. | result 1.00 | 0.87 | 0.04 | asserted 1.00 |
| s7 | The evolution of the binary SMBH leads to relatively shallower inner slopes at the centers of the merger remnants. | result 1.00 | 0.87 | 0.05 | asserted 1.00 |
| s8 | The stellar mass displaced by the SMBH binary on its way to coalescence is ~ 1-5 times the combined mass of binary SMBHs. | result 1.00 | 0.90 | 0.04 | asserted 1.00 |
| s9 | 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. | result 0.99 | 0.81 | 0.08 | asserted 1.00 |
| s10 | SMBH binaries are thus expected to be promising sources of gravitational waves at low and high redshifts. | interpretation 1.00 | 0.17 | 0.12 | hedged possibility 0.93 |
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Original 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.
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6 arXiv papers cite this in 8 sentences
Papers citing it · 5 sentences without a confident label
Compares with it 2 papers
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Such long time-scales are on the upper end of coalescence time-scales for binary black hole mergers from simulations [ref] , especially if the initial merger was gas-poor.
The Host Galaxies and Narrow Line Regions of Four Double-Peaked [OIII] AGN · Undisturbed X-ray binary · 0.87
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Moreover, $M_d$ given by Eq. ([ref]) is consistent with the results of full $N$-body simulations by Khan et al. [ref] , as shown in the right panel of Figure [ref].
Science with the space-based interferometer LISA. V: Extreme mass-ratio inspirals · Cusp erosion and regrowth. · 0.97
Cites it as support 1 paper
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Additionally, realistic N-body simulations of massive galaxy mergers result in SMBH binaries in eccentric orbits due to stellar interactions [ref] .
Pulsar timing array signals induced by black hole binaries in relativistic eccentric orbits · Introduction · 0.96
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