Hierarchical mergers of stellar-mass black holes and their gravitational-wave signatures

Gerosa, Davide; Fishbach, Maya

doi:10.48550/arxiv.2105.03439

Cited by 12 publications

(16 citation statements)

References 257 publications

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“…While we will broadly consider IMRI systems, one particular focus is on memory from hierarchical mergers involving second-or third-generation black holes. These systems present, on average, both larger masses and larger spins [38]. Many of our experiments consider systems with M = 200 M , q = 10, and large-spin systems, which is consistent with a GW190521like remnant capturing a first-generation, stellar-mass black hole.…”

Section: Phenomenology and Detectabilitysupporting

confidence: 60%

“…In this work, using a recently-developed spin [25] and higher multipole displacement memory model [12], we systematically investigate the total memory effects for intermediate mass ratio inspirals (IMRIs) while primarily focusing on the potential detectability of these signals. Our work is motivated by binary systems formed through hierarchical mergers [37,38], for example, when a GW190521-like remnant captures a stellar-mass black hole. Such systems typically have a large total mass, large spin on the primary, and possibly residual eccentricity; features that potentially raise the prospect for memory detection especially when subdominant modes are included into the analysis.…”

Section: Discussionmentioning

confidence: 99%

“…Heavy binaries with large positive spins are particularly promising for memory detections. For hierarchical mergers with second-generation (or higher) component black holes, spins of up to χ ≈ .9 are expected [37,38]. The increased SNR at larger spin values would favorably contribute to forecasts for memory detection.…”

Section: Discussionmentioning

confidence: 99%

“…The angle-averaged SNR for the displacement memory is between ∼ 1 (for χ = −.8) and ∼ 20 (for χ = .99). For hierarchical mergers with second-generation (or higher) component black holes, spins of up to χ ≈ .9 are expected [37,38], suggesting that memory from some of these system may be directly observed with ET even in the typical case. Indeed, a handful of high-spin black holes have been identified [82,83] and may therefore be the most promising candidates for memory detections.…”

Section: Effect Of Spinmentioning

confidence: 99%

“…The GW190521 remnant black hole has an estimated mass and dimensionless spin of 142 +28 −16 M and 0.72 +0.09 −0.12 , respectively. When formed through hierarchical mergers [37,38], for example when a GW190521-like remnant captures a stellar mass black hole, IMRI systems typically have a large total mass, large spin on the primary, and possibly residual eccentricity; features that potentially raise the prospect for memory detection especially when subdominant modes are included into the analysis [12,39]. On the other hand, a competing effect is that higher-mass-ratio sources emit weaker signals.…”

Section: Introductionmentioning

confidence: 99%

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Survey of gravitational wave memory in intermediate mass ratio binaries

Islam¹,

Field²,

Khanna³

et al. 2021

Preprint

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The non-linear gravitational wave (GW) memory effect is a distinct prediction in general relativity. While the effect has been well studied for comparable mass binaries, it has mostly been overlooked for intermediate mass ratio inspirals (IMRIs). We offer a comprehensive analysis of the phenomenology and detectability of memory effects, including contributions from subdominant harmonic modes, in heavy IMRIs consisting of a stellar mass black hole and an intermediate mass black hole. When formed through hierarchical mergers, for example when a GW190521-like remnant captures a stellar mass black hole, IMRI systems have a large total mass, large spin on the primary, and possibly residual eccentricity; features that potentially raise the prospect for memory detection. We compute both the displacement and spin non-linear GW memory from the m = 0 gravitational waveforms computed within a black hole perturbation theory framework that is partially calibrated to numerical relativity waveforms. We probe the dependence of memory effects on mass ratio, spin, and eccentricity and consider the detectability of a memory signal from IMRIs using current and future GW detectors. We find that (i) while eccentricity introduces additional features in both displacement and spin memory, it does not appreciatively change the prospects of detectability, (ii) including higher modes into the memory computation can increase singal-to-noise (SNR) values by about 7% in some cases, (iii) the SNR from displacement memory dramatically increases as the spin approaches large, positive values, (iv) spin memory from heavy IMRIs would, however, be difficult to detect with future generation detectors even from highly spinning systems. Our results suggest that hierarchical binary black hole mergers may be a promising source for detecting memory and could favorably impact memory forecasts.

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Section: Phenomenology and Detectabilitysupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Effect Of Spinmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Survey of gravitational wave memory in intermediate mass ratio binaries

Islam¹,

Field²,

Khanna³

et al. 2021

Preprint

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Formation of supermassive black holes in galactic nuclei – I. Delivering seed intermediate-mass black holes in massive stellar clusters

Askar

Davies

Church

2021

Monthly Notices of the Royal Astronomical Society

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Supermassive black holes (SMBHs) are found in most galactic nuclei. A significant fraction of these nuclei also contain a nuclear stellar cluster (NSC) surrounding the SMBH. In this paper, we consider the idea that the NSC forms first, from the merger of several stellar clusters that may contain intermediate-mass black holes (IMBHs). These IMBHs can subsequently grow in the NSC and form an SMBH. We carry out N-body simulations of the simultaneous merger of three stellar clusters to form an NSC, and investigate the outcome of simulated runs containing zero, one, two and three IMBHs. We find that IMBHs can efficiently sink to the centre of the merged cluster. If multiple merging clusters contain an IMBH, we find that an IMBH binary is likely to form and subsequently merge by gravitational wave emission. We show that these mergers are catalyzed by dynamical interactions with surrounding stars, which systematically harden the binary and increase its orbital eccentricity. The seed SMBH will be ejected from the NSC by the recoil kick produced when two IMBHs merge, if their mass ratio q ≳ 0.15. If the seed is ejected then no SMBH will form in the NSC. This is a natural pathway to explain those galactic nuclei that contain an NSC but apparently lack an SMBH, such as M33. However, if an IMBH is retained then it can seed the growth of an SMBH through gas accretion and tidal disruption of stars.

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Globular cluster formation histories, masses, and radii inferred from gravitational waves

Fishbach

Fragione

2023

Monthly Notices of the Royal Astronomical Society

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Globular clusters (GCs) are found in all types of galaxies and harbor some of the most extreme stellar systems, including black holes that may dynamically assemble into merging binaries (BBHs). Uncertain GC properties, including when they formed, their initial masses and sizes, affect their production rate of BBH mergers. Using the gravitational-wave catalog GWTC-3, we measure that dynamically-assembled BBHs – those that are consistent with isotropic spin directions – make up ${61^{+29}_{-44}\%}$ of the total merger rate, with a local merger rate of ${10.9^{+16.8}_{-9.3}}$ Gpc−3 yr−1 rising to ${58.9^{+149.4}_{-46.0}}$ Gpc−3 yr−1 at z = 1. We assume this inferred rate describes the contribution from GCs and compare it against the Cluster Monte Carlo (cmc) simulation catalog to directly fit for the GC initial mass function, virial radius distribution, and formation history. We find that GC initial masses are consistent with a Schechter function with slope ${\beta _m = -1.9^{+0.8}_{-0.8}}$. Assuming a mass function slope of βm = −2 and a mass range between 104–108 M⊙, we infer a GC formation rate at z = 2 of ${5.0^{+9.4}_{-4.0}}$ Gpc−3 yr−1, or ${2.1^{+3.9}_{-1.7}}\times 10^6\, M_\odot$ Gpc−3 yr−1 in terms of mass density. We find that the GC formation rate probably rises more steeply than the global star formation rate between z = 0 and z = 3 (82 per cent credibility) and implies a local number density that is ${f_\mathrm{ev} = 22.6^{+29.9}_{-16.2}}$ times higher than the observed density of survived GCs. This is consistent with expectations for cluster evaporation, but may suggest that other environments contribute to the rate of BBH mergers with significantly tilted spins.

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Hierarchical mergers of stellar-mass black holes and their gravitational-wave signatures

Cited by 12 publications

References 257 publications

Survey of gravitational wave memory in intermediate mass ratio binaries

Survey of gravitational wave memory in intermediate mass ratio binaries

Formation of supermassive black holes in galactic nuclei – I. Delivering seed intermediate-mass black holes in massive stellar clusters

Globular cluster formation histories, masses, and radii inferred from gravitational waves

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