Migration of massive black hole binaries in self-gravitating discs: retrograde versus prograde

Roedig, Constanze; Sesana, Alberto

doi:10.1093/mnras/stu194

Cited by 50 publications

(72 citation statements)

References 46 publications

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“…As a result, the gas inflow is expected to slow down (Artymowicz & Lubow 1994), leading to the formation of the inner cavity in the disk with a characteristic radius r c , see Figure 1 for illustration. A number of numerical studies (MacFadyen & Milosavljević 2008) find » r a 2 c b for binaries with comparable components (q 1), with some dependence on the binary eccentricity e b (Pelupessy & Portegies Zwart 2013;Roedig & Sesana 2014). The suppression of accretion by the cavity is likely not perfect , as the gas can flow into it via localized streams letting the binary to accrete at some finite rateṀ b , as discussed in Section 5.…”

Section: Basic Setupmentioning

confidence: 96%

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Accretion and Orbital Inspiral in Gas-Assisted Supermassive Black Hole Binary Mergers

Rafikov

2016

ApJ

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Many galaxies are expected to harbor binary supermassive black holes (SMBHs) in their centers. Their interaction with the surrounding gas results in the accretion and exchange of angular momentum via tidal torques, facilitating binary inspiral. Here, we explore the non-trivial coupling between these two processes and analyze how the global properties of externally supplied circumbinary disks depend on the binary accretion rate. By formulating our results in terms of the angular momentum flux driven by internal stresses, we come up with a very simple classification of the possible global disk structures, which differ from the standard constantṀ accretion disk solution. The suppression of accretion by the binary tides, leading to a significant mass accumulation in the inner disk, accelerates binary inspiral. We show that once the disk region strongly perturbed by the viscously transmitted tidal torque exceeds the binary semimajor axis, the binary can merge in less than its mass-doubling time due to accretion. Thus, unlike the inspirals driven by stellar scattering, the gas-assisted merger can occur even if the binary is embedded in a relatively low-mass disk (lower than its own mass). This is important for resolving the "last parsec" problem for SMBH binaries and understanding powerful gravitational wave sources in the universe. We argue that the enhancement of accretion by the binary found in some recent simulations cannot persist for a long time and should not affect the long-term orbital inspiral. We also review existing simulations of SMBH binary-disk coupling and propose a numerical setup which is particularly well suited to verifying our theoretical predictions.

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Section: Basic Setupmentioning

confidence: 96%

“…. Misaligned and counterrotating binary-disk systems have previously been considered by Nixon et al (2013), Roedig & Sesana (2014), Ivanov et al (2015), and Schnittman & Krolik (2015).…”

Section: Introductionmentioning

confidence: 99%

Accretion and Orbital Inspiral in Gas-Assisted Supermassive Black Hole Binary Mergers

Rafikov

2016

ApJ

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“…Roedig & Sesana 2014). In addition McKernan et al (2014) have recently considered the opposite limit of an extremely small mass ratio q = 10 −4 using the gridbased PENCIL CODE.…”

Section: Introductionmentioning

confidence: 99%

The evolution of a binary in a retrograde circular orbit embedded in an accretion disk

Ivanov

Papaloizou

Paardekooper

et al. 2015

A&A

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Aims. Supermassive black hole binaries may form as a consequence of galaxy mergers. Both prograde and retrograde orbits have been proposed. We study a binary with a small mass ratio, q, in a retrograde orbit immersed in and interacting with a gaseous accretion disk in order to estimate the time scales for inward migration that leads to coalescence and the accretion rate to the secondary component. Methods. We employed both semi-analytic methods and two-dimensional numerical simulations, focusing on the case where the binary mass ratio is small but large enough to significantly perturb the disk. Results. We develop the theory of type I migration in this case and go on to determine the conditions for gap formation. We find that when this happens inward migration occurs on a time scale equal to the time required for one half of the secondary mass to be accreted through the unperturbed accretion disk. The accretion rate onto the secondary itself is found to only play a minor role in the orbital evolution as it is of the order of q 1/3 of that to the primary. We obtain good general agreement between the semi-analytic and fully numerical approaches and note that the former can be applied to disks with a wide dynamic range on long time scales. Conclusions. We conclude that inward migration induced by interaction with the disk can enable the binary to migrate inwards, alleviating the so-called final parsec problem. When q is sufficiently small, there is no well-pronounced cavity inside the binary orbit, unlike the prograde case. The accretion rate to the secondary does not influence the binary orbital evolution much, but can lead to some interesting observational consequences, provided the accretion efficiency is sufficiently large. In this case the binary may be detected as, for example, two sources of radiation rotating around each other. However, the study should be extended to consider orbits with significant eccentricity and the effects of gravitational radiation at small length scales. Also, torques acting between a circumbinary accretion disk, which has a non-zero inclination with respect to a retrograde binary orbit at large distances, may cause the inclination to increase on a time scale that can be similar to, or smaller than, the time scale of orbital evolution, depending on the disk parameters and binary mass ratio. This is also an aspect for future study.

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“…Retrograde circumbinary discs (Nixon et al 2011a;Nixon 2012;Roedig & Sesana 2014) have received relatively little attention compared to prograde discs (e.g. Artymowicz & Lubow 1996;Escala et al 2005;Lodato et al 2009;Cuadra et al 2009;Roedig et al 2012;D'Orazio et al 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The simulations of Nixon et al (2012) and Nixon (2012) focussed on circular orbit binaries, with only a few simulations with e 0, in which the eccentricity was always small. Roedig & Sesana (2014) performed simulations of retrograde discs with eccentricities as high as e = 0.9, but due to the strongly self-gravitating discs employed, and the induction of disc tilt due to the dominant disc angular momentum (cf. King et al 2005;Nixon et al 2011b), the subtle resonant effects sought here may have been missed.…”

Section: Introductionmentioning

confidence: 99%

Resonances in retrograde circumbinary discs

Nixon

Lubow

2015

Monthly Notices of the Royal Astronomical Society

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We analyse the interaction of an eccentric binary with a circular coplanar circumbinary disc that rotates in a retrograde sense with respect to the binary. In the circular binary case, no Lindblad resonances lie within the disc and no Lindblad resonant torques are produced, as was previously known. By analytic means, we show that when the binary orbit is eccentric, there exist components of the gravitational potential of the binary which rotate in a retrograde sense to the binary orbit and so rotate progradely with respect to this disc, allowing a resonant interaction to occur between the binary and the disc. The resulting resonant torques distinctly alter the disc response from the circular binary case. We describe results of three-dimensional hydrodynamic simulations to explore this effect and categorise the response of the disc in terms of modes whose strengths vary as a function of binary mass ratio and eccentricity. These mode strengths are weak compared to the largest mode strengths expected in the prograde case where the binary and disc rotate in the same sense. However, for sufficiently high binary eccentricity, resonant torques open a gap in a retrograde circumbinary disc, while permitting gas inflow on to the binary via gas streams. The inflow results in a time varying accretion rate on to the binary that is modulated over the binary orbital period, as was previously found to occur in the prograde case.

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Migration of massive black hole binaries in self-gravitating discs: retrograde versus prograde

Cited by 50 publications

References 46 publications

Accretion and Orbital Inspiral in Gas-Assisted Supermassive Black Hole Binary Mergers

Accretion and Orbital Inspiral in Gas-Assisted Supermassive Black Hole Binary Mergers

The evolution of a binary in a retrograde circular orbit embedded in an accretion disk

Resonances in retrograde circumbinary discs

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