Binary black hole mergers in AGN accretion discs: gravitational wave rate density estimates

Gröbner, Matthias; Ishibashi, W.; Tiwari, Shubhanshu; Haney, M.; Jetzer, Philippe

doi:10.1051/0004-6361/202037681

Cited by 103 publications

(68 citation statements)

References 46 publications

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“…BBH formation and merger can also be facilitated within the star clusters (Sigurdsson & Hernquist 1993;Portegies Zwart & McMillan 2000;Rodriguez et al 2015;Antonini & Rasio 2016;Gerosa & Berti 2019). This could include their formation in active galactic nuclei (Stone et al 2017;Gröbner et al 2020;Yang et al 2019;Tagawa et al 2021;Gayathri et al 2021) or formation of binaries due to scattering in galactic cusps (O'Leary et al 2009). The mass spectrum can potentially inform about the many-body dynamics in the star clusters.…”

Section: Astrophysical Implicationsmentioning

confidence: 99%

Exploring Features in the Binary Black Hole Population

Tiwari

2021

Preprint

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Vamana is the mixture model framework that infers the chirp mass, mass ratio and aligned spin distributions of the binary black holes (BBH) population. We extend the mixing components to also model the redshift evolution of merger rate and report all the major one and two-dimensional features in the BBH population using the 69 gravitational wave (GW) signals detected with a false alarm rate < 1yr −1 in the third Gravitational Wave Transient Catalog (GWTC)-3. Endorsing our previous report and corroborating recent report from LIGO Scientific, Virgo and KAGRA Collaborations, we observe the chirp mass distribution has multiple peaks and a lack of mergers with chirp masses 10-12M . In addition, we observe aligned spins show mass dependence with heavier binaries exhibiting larger spins, mass ratio does not show a notable dependence on either the chirp mass or the aligned spin, and the redshift evolution of the merger rate for the peaks in the mass distribution is disparate. These features possibly reflect the astrophysics associated with the BBH formation channels. However, additional observations are needed to improve our limited confidence in them.

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Section: Astrophysical Implicationsmentioning

confidence: 99%

Exploring Features in the Binary Black Hole Population

Tiwari

2021

Preprint

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“…Additional alternatives to dynamical formation in dense star clusters include dynamical formation in active galactic nuclei discs (Yang et al 2019;McKernan et al 2020;Gröbner et al 2020;Li et al 2021), which may be efficient factories for eccentric binary black holes Tagawa et al 2021). However, the distribution of mass, spin, and eccentricity for binary black holes in active galactic nuclei discs are comparatively poorly understood owing to the complicated environment.…”

Section: Introductionmentioning

confidence: 99%

Signs of eccentricity in two gravitational-wave signals may indicate a sub-population of dynamically assembled binary black holes

Romero-Shaw,

Lasky,

Thrane

2021

Preprint

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The orbital eccentricity of a merging binary black hole leaves an imprint on the associated gravitational-wave signal that can reveal whether the binary formed in isolation or in a dynamical environment, such as the core of a dense star cluster. We present measurements of the eccentricity of 26 binary black hole mergers in the second LIGO-Virgo gravitational-wave transient catalog, updating the total number of binary black holes analysed for orbital eccentricity to 36. Using the SEOBNRE waveform, we find the data for GW190620A is poorly explained by the zero-eccentricity hypothesis (frequentist 𝑝-value 0.1%). With a uniform eccentricity prior, the data prefer 𝑒 10 ≥ 0.11 at 90% credibility, while assuming a uniform-in-log eccentricity prior yields a 90% credible lower eccentricity limit of 0.001. Using the log-uniform prior, the eccentricity at 10 Hz for GW190620A is constrained to 𝑒 10 ≥ 0.05 (0.1) at 74% (65%) credibility. This is the second measurement of a binary black hole system with statistical support for non-zero eccentricity; the intermediate-mass black hole merger GW190521 was the first. Interpretation of these two events is currently complicated by waveform systematics; we are unable to simultaneously model the effects of relativistic precession and eccentricity. However, if these two events are, in fact, eccentric mergers, then there are potentially many more dynamically assembled mergers in the LIGO-Virgo catalog without measurable eccentricity; 27% of the observed LIGO-Virgo binaries may have been assembled dynamically in dense stellar environments (95% credibility).

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“…Active galactic nucleus (AGN) disks have been proposed as one of the most promising locations for producing some of the detected stellar mass binary black hole (BBH) and neutron star mergers (e.g., McKernan et al 2012;Bartos et al 2017;Stone et al 2017;Leigh et al 2018;Gröbner et al 2020;Kimura et al 2021;Wang et al 2021;Zhu et al 2021), especially for the recent detection of the heaviest BBH merger event GW190521 with a possible electromagnetic counterpart (Abbott et al 2020;Graham et al 2020). This "AGN channel" could be an intriguing alternative to other traditional formation channels (Belczynski et al 2016;Fernández & Kobayashi 2019;Fragione et al 2021;Liu & Lai 2021).…”

Section: Introductionmentioning

confidence: 99%

Hot Circumsingle Disks Drive Binary Black Hole Mergers in Active Galactic Nucleus Disks

Li,

Dempsey,

et al. 2021

Preprint

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Binary black hole (BBH) mergers, particularly those with component masses in the pair-instability gap, may be produced by hierarchical mergers in the disks surrounding Active Galactic Nuclei (AGN). While the interaction of an embedded BBH with an AGN disk is typically assumed to facilitate merger, recent high-resolution hydrodynamical simulations challenge this assumption. However, these simulations often have simplified treatments for the gas thermodynamics. In this work, we model the possible consequence of various feedback from an embedded BBH with a simple model that maintains an enhanced temperature profile around each binary component. We show that when the mini-disks around each BH become hotter than the background by a factor of three, the BBH orbital evolution switches from expansion to contraction. By analyzing the gravitational torque profile, we find that this change in direction is driven by a weakening of the mini-disk spirals and their positive torque on the binary. Our results highlight the important role of thermodynamics around BBHs and its effect on their orbital evolution, suggesting that AGN disks could be efficient factories for BBH mergers.

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Binary black hole mergers in AGN accretion discs: gravitational wave rate density estimates

Cited by 103 publications

References 46 publications

Exploring Features in the Binary Black Hole Population

Exploring Features in the Binary Black Hole Population

Signs of eccentricity in two gravitational-wave signals may indicate a sub-population of dynamically assembled binary black holes

Hot Circumsingle Disks Drive Binary Black Hole Mergers in Active Galactic Nucleus Disks

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