Bondi–Hoyle–Lyttleton Accretion onto Star Clusters

Kaaz, Nicholas; Antoni, Andrea; Ramírez-Ruiz, E.

doi:10.3847/1538-4357/ab158b

Cited by 26 publications

(30 citation statements)

References 58 publications

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“…A recent study by Kaaz et al (2019) has shown that the BH accretion rate will depend on the characteristic accretion radius of the cluster 𝑅 acc and the mean separation between stars 𝑅 ⊥ , where 𝑅 ⊥ = 𝑅 cl 𝑁 −1/3 . The average accretion rate of an individual star is given as…”

Section: Gas Accretionmentioning

confidence: 99%

Formation of supermassive black hole seeds in nuclear star clusters via gas accretion and runaway collisions

Das,

Schleicher,

Leigh

et al. 2020

Preprint

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More than two hundred supermassive black holes (SMBHs) of masses 10 9 M have been discovered at 𝑧 6. One promising pathway for the formation of SMBHs is through the collapse of supermassive stars (SMSs) with masses ∼ 10 3−5 M into seed black holes which could grow upto few times 10 9 M SMBHs observed at 𝑧 ∼ 7. In this paper, we explore how SMSs with masses ∼ 10 3−5 M could be formed via gas accretion and runaway stellar collisions in high-redshift, metal-poor nuclear star clusters (NSCs). We explore physically motivated accretion scenarios, e.g. Bondi-Hoyle-Lyttleton accretion and Eddington accretion, as well as simplified scenarios such as constant accretions. While gas is present, the accretion timescale remains considerably shorter than the timescale for collisions with the most massive object (MMO). However, overall the timescale for collisions between any two stars in the cluster can become comparable or shorter than the accretion timescale, hence collisions still play a crucial role in determining the final mass of the SMSs. We find that the problem is highly sensitive to the initial conditions and our assumed recipe for the accretion, due to the highly chaotic nature of the problem. The key variables that determine the mass growth mechanism are the mass of the MMO and the gas reservoir that is available for the accretion. Depending on different conditions, massive objects of masses ∼ 10 3−5 M can form for all three accretion scenarios considered in this work.

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Section: Gas Accretionmentioning

confidence: 99%

Formation of supermassive black hole seeds in nuclear star clusters via gas accretion and runaway collisions

Das,

Schleicher,

Leigh

et al. 2020

Preprint

View full text Add to dashboard Cite

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“…Sufficiently compact PBH systems could begin accreting coherently which will lead to an enhanced accretion rate when compared to the case where the PBHs are treated as independent accretors. In particular, once their accretion radii start to overlap significantly, a system consisting of N PBHs might start to accrete as a coherent whole, leading to an enhancement by a factor of N compared to the situation with N independent accretors [37,38]. The investigation of this coherent boost factor is another task for this paper.…”

Section: Introductionmentioning

confidence: 99%

Small-scale structure of primordial black hole dark matter and its implications for accretion

2019

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Primordial black hole (PBH) dark matter (DM) non-linear small-scale structure formation begins before the epoch of recombination due to large Poisson density fluctuations. Those small-scale effects survive until today, distinguishing physics of PBH DM structure formation from the one involving WIMP DM. We construct an analytic model for the small-scale PBH velocities which reproduces the velocity floor seen in numerical simulations, and investigate how these motions impact PBH accretion bounds at different redshifts. We find that the effect is small at the time of recombination, leaving the CMB bounds on PBH abundance unchanged. However, already at z = 20 the PBH internal motion significantly reduces their accretion due to the additional 1/v 6 suppression, affecting the 21 cm bounds. Today the accretion bounds arising from dwarf galaxies or smaller PBH sub-structures are all reduced by the PBH velocity floor. We also investigate the feasibility for the PBH clusters to coherently accrete gas leading to a possible enhancement proportional to the cluster's occupation number but find this effect to be insignificant for PBH around 10M or lighter. Those results should be reconsidered if the initial PBH distribution is not Poisson, for example, in the case of large initial PBH clustering. arXiv:1907.06533v1 [astro-ph.CO]

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“…It's worth taking a moment to contextualize our wind tunnel framework in the landscape of other accretion flows. Our setup is similar to other local simulations of accretion flows, which have proven effective tools for understanding both single and binary BH accretion in a variety of environments, including the ISM (Antoni et al 2019;Kaaz et al 2019, 2020, Schrøder et al 2021 and common envelope evolution (MacLeod & Ramirez-Ruiz 2015a,b;MacLeod et al 2017;Murguia-Berthier et al 2017;De et al 2020;Everson et al 2020). This family of accretion flows essentially considers permutations of Bondi-Hoyle-Lyttleton accretion (for a review, see Edgar 2004) characterized by the gas properties of the surrounding medium.…”

Section: Defining Properties Of the Accretion Flowmentioning

confidence: 96%

The hydrodynamic evolution of binary black holes embedded within the vertically stratified disks of active galactic nuclei

Kaaz¹,

Schröder²,

Andrews³

et al. 2021

Preprint

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Stellar-mass black holes can become embedded within the gaseous disks of active galactic nuclei (AGNs). Afterwards, their interactions are mediated by their gaseous surroundings. In this work, we study the evolution of stellar-mass binary black holes (BBHs) embedded within AGN disks using a combination of three-dimensional hydrodynamic simulations and analytic methods, focusing on environments in which the AGN disk scale height H is the BBH sphere of influence. We model the local surroundings of the embedded BBHs using a wind tunnel formalism and characterize different accretion regimes based on the local properties of the disk, which range from wind-dominated to quasi-spherical. We use our simulations to develop prescriptions for mass accretion and drag for embedded BBHs. We use these prescriptions, along with AGN disk models that can represent the Toomre-unstable outer regions of AGN disks, to study the long-term evolution of the BBHs as they migrate through the disk. We find that BBHs typically merge within 5 − 30 Myr, increasing their mass significantly in the process, allowing BBHs to enter (or cross) the pair-instability supernova mass gap. The rate at which gas is supplied to these BBHs often exceeds the Eddington limit, sometimes by several orders of magnitude. We conclude that most embedded BBHs will merge before migrating significantly in the disk. Depending on the conditions of the ambient gas and the distance to the system, LISA can detect the transition between the gas-dominated and gravitational wave dominated regime for inspiraling BBHs that are formed sufficiently close to the AGN ( 0.1 pc). We also discuss possible electromagnetic signatures during and following the inspiral, finding that it is generally unlikely but not inconceivable for the bolometric luminosity of the BBH to exceed that of the host AGN.

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Bondi–Hoyle–Lyttleton Accretion onto Star Clusters

Cited by 26 publications

References 58 publications

Formation of supermassive black hole seeds in nuclear star clusters via gas accretion and runaway collisions

Formation of supermassive black hole seeds in nuclear star clusters via gas accretion and runaway collisions

Small-scale structure of primordial black hole dark matter and its implications for accretion

The hydrodynamic evolution of binary black holes embedded within the vertically stratified disks of active galactic nuclei

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