Black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections

Antonini, Fabio; Gieles, M.; Gualandris, Alessia

doi:10.1093/mnras/stz1149

Cited by 225 publications

(214 citation statements)

References 135 publications

(158 reference statements)

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“…Nonetheless, the potential well of the heaviest clusters (globular and nuclear clusters) might be sufficiently deep to retain some of the post-merger BHs. This allows the remnant BHs to possibly undergo multiple mergers (Miller & Hamilton 2002;Gerosa & Berti 2017;Antonini et al 2019;Arca Sedda & Benacquista 2019;Kimball et al 2020;Doctor et al 2020;Rodriguez et al 2019), leading to higher and higher BH masses. The probability for BHs to undergo at least two mergers can rise up to~40% for both globular and nuclear clusters .…”

Section: Gw Recoilmentioning

confidence: 99%

“…Dense stellar systems, like globular or nuclear clusters, can potentially retain merger products and favor multiple mergers, thus allowing BH mass buildup Antonini et al 2019;Gerosa et al 2018;Qin et al 2018;Arca Sedda & Benacquista 2019;Doctor et al 2020;Rodriguez et al 2019). These second generation BHs can significantly affect the BH mass spectrum.…”

Section: Introductionmentioning

confidence: 99%

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Fingerprints of Binary Black Hole Formation Channels Encoded in the Mass and Spin of Merger Remnants

Sedda¹,

Mapelli

Spera

et al. 2020

ApJ

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Binary black holes (BBHs) are thought to form in different environments, including the galactic field and (globular, nuclear, young, and open) star clusters. Here, we propose a method to estimate the fingerprints of the main BBH formation channels associated with these different environments. We show that the metallicity distribution of galaxies in the local universe along with the relative amount of mergers forming in the field or in star clusters determine the main properties of the BBH population. Our fiducial model predicts that the heaviest merger to date, GW170729, originated from a progenitor that underwent 2-3 merger events in a dense star cluster, possibly a galactic nucleus. The model predicts that at least one merger remnant out of a hundred BBH mergers in the local universe has mass <  M M 90 110 rem  , and one in a thousand can reach a mass as large as  M M 250 rem . Such massive black holes would bridge the gap between stellar-mass and intermediate-mass black holes. The relative number of low-and high-mass BBHs can help us unravel the fingerprints of different formation channels. Based on the assumptions of our model, we expect that isolated binaries are the main channel of BBH merger formation if~70% of the whole BBH population has remnants with masses < M 50  , whereas 6% of remnants having masses > M 75  points to a significant subpopulation of dynamically formed BBH binaries.

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Section: Gw Recoilmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fingerprints of Binary Black Hole Formation Channels Encoded in the Mass and Spin of Merger Remnants

Sedda¹,

Mapelli

Spera

et al. 2020

ApJ

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“…The binding energy, and therefore, the semi-major axis of escaping BH binaries depends on the central escape velocity (v esc ) of the cluster (see Rodriguez et al 2016), which is also proportional to M cl /r h . The condition for in-cluster BH binary mergers to be efficient can also be expressed in M cl and r h (see Antonini et al 2019). We therefore model the evolution of M cl and r h .…”

Section: Philosophy Of the Modelmentioning

confidence: 99%

Population synthesis of black hole binary mergers from star clusters

Antonini

Gieles

2020

Monthly Notices of the Royal Astronomical Society

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Black hole (BH) binary mergers formed through dynamical interactions in dense star clusters are believed to be one of the main sources of gravitational waves for Advanced LIGO and Virgo. Here we present a fast numerical method for simulating the evolution of star clusters with BHs, including a model for the dynamical formation and merger of BH binaries. Our method is based on Hénon's principle of balanced evolution, according to which the flow of energy within a cluster must be balanced by the energy production inside its core. Because the heat production in the core is powered by the BHs, one can then link the evolution of the cluster to the evolution of its BH population. This allows us to construct evolutionary tracks of the cluster properties including its BH population and its effect on the cluster and, at the same time, determine the merger rate of BH binaries as well as their eccentricity distributions. The model will be publicly available and includes the effects of a BH mass spectrum, massloss due to stellar evolution, the ejection of BHs due to natal and dynamical kicks, and relativistic corrections during binary-single encounters. We validate our method using direct N-body simulations, and find it to be in excellent agreement with results from recent Monte Carlo models of globular clusters. This establishes our new method as a robust tool for the study of BH dynamics in star clusters and the modelling of gravitational wave sources produced in these systems. Finally, we compute the rate and eccentricity distributions of merging BH binaries for a wide range of cluster initial conditions, spanning more than two orders of magnitude in mass and radius.In the dynamical formation scenario, the BH binaries are assembled through three body processes in the core of a star cluster, and subsequently harden and merge via dynamical binary-single interactions. Recent studies suggest that

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“…On the other hand, we can estimate the ejection velocity of a light star, vej, after an strong interaction with a BH binary in the cluster core by (Miller & Lauburg 2009;Antonini, Gieles, & Gualandris 2019):…”

Section: Light Starsmentioning

confidence: 99%

The survival of star clusters with black hole subsystems

Wang

2019

Monthly Notices of the Royal Astronomical Society

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Recent observations have detected top-heavy IMFs in dense star forming regions like the Arches cluster. Whether such IMFs also exist in old dense stellar systems like globular clusters is difficult to constrain, because massive stars already became black holes (BHs) and neutron stars (NSs). However, studies of stellar dynamics find that BHs/NSs influence the long-term evolution of star clusters. Following Breen & Heggie (2013) and by carrying out two-component N -body simulations, we demonstrate how this dynamical impact connects with the shape of IMFs. By investigating the energy balance between the BH subsystem and the global, we find that to properly describe the evolution of clusters, a corrected two-body relaxation time, T rh,p = T rh /ψ, is necessary. Because ψ depends on the total mass fraction of BHs, M 2 /M , and the mass ratio, m 2 /m 1 , the cluster dissolution time is sensitive to the property of BHs or IMFs. Especially, the escape rate of BHs via ejections from few-body encounters are linked to mass segregation. In strong tidal fields, top-heavy IMFs easily lead to the fast dissolution of star clusters and the formation of BH-dominant dark clusters, which suggests that the observed massive GCs with dense cores are unlikely to have extreme top-heavy IMFs. With the future observations of gravitational waves providing unique information of BHs/NSs, it is possible to combine the multi-message observations to have better constrains on the IMFs of old star clusters.

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Black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections

Cited by 225 publications

References 135 publications

Fingerprints of Binary Black Hole Formation Channels Encoded in the Mass and Spin of Merger Remnants

Fingerprints of Binary Black Hole Formation Channels Encoded in the Mass and Spin of Merger Remnants

Population synthesis of black hole binary mergers from star clusters

The survival of star clusters with black hole subsystems

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