Black Hole dynamics in Young Star Clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 490-493
Author(s):  
Sara Rastello ◽  
Ugo N. di Carlo ◽  
Michela Mapelli ◽  
Nicola Giacobbo ◽  
Alessandro Ballone
Keyword(s):  
Black Hole ◽  
Binary Star ◽  
Star Clusters ◽  
Young Star ◽  
Population Synthesis ◽  
Massive Black Hole ◽  
Binary Black Holes ◽  
Black Hole Binaries ◽  
Low Mass ◽  
Young Star Clusters

AbstractYoung star clusters are a promising environment for forming binary black holes. Such binaries may form dynamically or via binary star evolution or through the interplay of these two channels. To study these formation pathways, we have performed high precision direct N-body simulations of low-mass (M < 1000 M⊙) young star clusters. The simulations were carried out with the code Nbody6++GPU coupled with the population synthesis code MOBSE. Our results highlight the importance of dynamics to form massive black hole binaries even in low-mass young star clusters.

scholarly journals Dynamics of black hole–neutron star binaries in young star clusters

2020 ◽  
Vol 497 (2) ◽  
pp. 1563-1570 ◽  
Author(s):  
Sara Rastello ◽  
Michela Mapelli ◽  
Ugo N Di Carlo ◽  
Nicola Giacobbo ◽  
Filippo Santoliquido ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Total Mass ◽  
Star Clusters ◽  
Cosmic Time ◽  
Young Star ◽  
Star Cluster ◽  
Population Synthesis ◽  
Compact Binaries ◽  
Young Star Clusters

ABSTRACT Young star clusters are likely the most common birthplace of massive stars across cosmic time and influence the formation of compact binaries in several ways. Here, we simulate the formation of black hole–neutron star binaries (BHNSs) in young star clusters, by means of the binary population synthesis code MOBSE interfaced with the N-body code NBODY6++GPU. BHNSs formed in young star clusters (dynamical BHNSs) are significantly more massive than BHNSs formed from isolated binaries (isolated BHNSs): ∼40 per cent of the dynamical BHNS mergers have a total mass of &gt;15 M⊙, while only ∼0.01 per cent of the isolated BHNS mergers have mass in excess of this value. Hence, our models strongly support a dynamical formation scenario for GW190814, given its total mass of ∼26 M⊙, if this event is a BHNS merger. All our dynamical BHNSs are ejected from their parent star cluster before they reach coalescence. Thus, a significant fraction of BHNS mergers occurring in the field might have originated in a young star cluster. The mass spectrum of BHNS mergers from gravitational-wave detections will provide a clue to differentiate between dynamical and isolated formation of BHNSs.

scholarly journals Hierarchical black hole triples in young star clusters: impact of Kozai–Lidov resonance on mergers

2016 ◽  
Vol 463 (3) ◽  
pp. 2443-2452 ◽  
Author(s):  
Thomas O. Kimpson ◽  
Mario Spera ◽  
Michela Mapelli ◽  
Brunetto M. Ziosi
Keyword(s):  
Black Hole ◽  
Star Clusters ◽  
Young Star ◽  
Young Star Clusters

scholarly journals How does a low-mass cut-off in the stellar IMF affect the evolution of young star clusters?

2014 ◽  
Vol 445 (3) ◽  
pp. 2256-2267 ◽  
Author(s):  
M. B. N. Kouwenhoven ◽  
S. P. Goodwin ◽  
R. de Grijs ◽  
M. Rose ◽  
Sungsoo S. Kim
Keyword(s):  
Star Clusters ◽  
Young Star ◽  
Low Mass ◽  
Young Star Clusters

scholarly journals Binary black holes in young star clusters: the impact of metallicity

2020 ◽  
Vol 498 (1) ◽  
pp. 495-506 ◽  
Author(s):  
Ugo N Di Carlo ◽  
Michela Mapelli ◽  
Nicola Giacobbo ◽  
Mario Spera ◽  
Yann Bouffanais ◽  
...  
Keyword(s):  
Black Holes ◽  
Initial Density ◽  
Star Clusters ◽  
Young Star ◽  
Binary Black Holes ◽  
Binary Evolution ◽  
Merger Rate ◽  
The Masses ◽  
The Impact ◽  
Young Star Clusters

ABSTRACT Young star clusters are the most common birthplace of massive stars and are dynamically active environments. Here, we study the formation of black holes (BHs) and binary black holes (BBHs) in young star clusters, by means of 6000 N-body simulations coupled with binary population synthesis. We probe three different stellar metallicities (Z = 0.02, 0.002, and 0.0002) and two initial-density regimes (density at the half-mass radius ρh ≥ 3.4 × 104 and ≥1.5 × 102 M⊙ pc−3 in dense and loose star clusters, respectively). Metal-poor clusters tend to form more massive BHs than metal-rich ones. We find ∼6, ∼2, and &lt;1 per cent of BHs with mass mBH &gt; 60 M⊙ at Z = 0.0002, 0.002, and 0.02, respectively. In metal-poor clusters, we form intermediate-mass BHs with mass up to ∼320 M⊙. BBH mergers born via dynamical exchanges (exchanged BBHs) can be more massive than BBH mergers formed from binary evolution: the former (latter) reach total mass up to ∼140 M⊙ (∼80 M⊙). The most massive BBH merger in our simulations has primary mass ∼88 M⊙, inside the pair-instability mass gap, and a mass ratio of ∼0.5. Only BBHs born in young star clusters from metal-poor progenitors can match the masses of GW 170729, the most massive event in first and second observing run (O1 and O2), and those of GW 190412, the first unequal-mass merger. We estimate a local BBH merger rate density ∼110 and ∼55 Gpc−3 yr−1, if we assume that all stars form in loose and dense star clusters, respectively.

scholarly journals Binary black holes in the pair instability mass gap

2020 ◽  
Vol 497 (1) ◽  
pp. 1043-1049 ◽  
Author(s):  
Ugo N Di Carlo ◽  
Michela Mapelli ◽  
Yann Bouffanais ◽  
Nicola Giacobbo ◽  
Filippo Santoliquido ◽  
...  
Keyword(s):  
Black Holes ◽  
Formation Rate ◽  
Star Clusters ◽  
Design Sensitivity ◽  
Young Star ◽  
Binary Black Holes ◽  
Single Star ◽  
Mass Gap ◽  
Young Star Clusters ◽  
Stellar Mergers

ABSTRACT Pair instability (PI) and pulsational PI prevent the formation of black holes (BHs) with mass ≳60 M⊙ from single star evolution. Here, we investigate the possibility that BHs with mass in the PI gap form via stellar mergers and multiple stellar mergers, facilitated by dynamical encounters in young star clusters. We analyse 104 simulations, run with the direct N-body code nbody6++gpu coupled with the population synthesis code mobse. We find that up to ∼6 per cent of all simulated BHs have mass in the PI gap, depending on progenitor’s metallicity. This formation channel is strongly suppressed in metal-rich (Z = 0.02) star clusters because of stellar winds. BHs with mass in the PI gap are initially single BHs but can efficiently acquire companions through dynamical exchanges. We find that ∼21 per cent, 10 per cent, and 0.5 per cent of all binary BHs have at least one component in the PI mass gap at metallicity Z = 0.0002, 0.002, and 0.02, respectively. Based on the evolution of the cosmic star formation rate and metallicity, and under the assumption that all stars form in young star clusters, we predict that ∼5 per cent of all binary BH mergers detectable by advanced LIGO and Virgo at their design sensitivity have at least one component in the PI mass gap.

scholarly journals New insights on binary black hole formation channels after GWTC-2: young star clusters versus isolated binaries

2021 ◽  
Author(s):  
Yann Bouffanais ◽  
Michela Mapelli ◽  
Filippo Santoliquido ◽  
Nicola Giacobbo ◽  
Ugo N Di Carlo ◽  
...  
Keyword(s):  
Black Hole ◽  
Gravitational Wave ◽  
Star Clusters ◽  
Credible Interval ◽  
Young Star ◽  
Compact Objects ◽  
Bayesian Hierarchical ◽  
Binary Black Hole ◽  
Higher Spin ◽  
Young Star Clusters

Abstract With the recent release of the second gravitational-wave transient catalogue (GWTC-2), which introduced dozens of new detections, we are at a turning point of gravitational wave astronomy, as we are now able to directly infer constraints on the astrophysical population of compact objects. Here, we tackle the burning issue of understanding the origin of binary black hole (BBH) mergers. To this effect, we make use of state-of-the-art population synthesis and N-body simulations, to represent two distinct formation channels: BBHs formed in the field (isolated channel) and in young star clusters (dynamical channel). We then use a Bayesian hierarchical approach to infer the distribution of the mixing fraction f, with f = 0 (f = 1) in the pure dynamical (isolated) channel. We explore the effects of additional hyper-parameters of the model, such as the spread in metallicity σZ and the parameter σsp, describing the distribution of spin magnitudes. We find that the dynamical model is slightly favoured with a median value of f = 0.26, when σsp = 0.1 and σZ = 0.4. Models with higher spin magnitudes tend to strongly favour dynamically formed BBHs (f ≤ 0.1 if σsp = 0.3). Furthermore, we show that hyper-parameters controlling the rates of the model, such as σZ, have a large impact on the inference of the mixing fraction, which rises from 0.18 to 0.43 when we increase σZ from 0.2 to 0.6, for a fixed value of σsp = 0.1. Finally, our current set of observations is better described by a combination of both formation channels, as a pure dynamical scenario is excluded at the $99{{\ \rm per\ cent}}$ credible interval, except when the spin magnitude is high.

scholarly journals Formation and Evolution of Massive Black Holes in Star Clusters

2005 ◽  
Vol 13 ◽  
pp. 350-353
Author(s):  
Holger Baumgardt ◽  
Junichiro Makino ◽  
Simon Portegies Zwart
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Initial Conditions ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Young Star ◽  
Cluster Center ◽  
Massive Black Hole ◽  
Massive Black Holes ◽  
Equilibrium Profile

AbstractWe present results of N-body simulations on the formation of massive black holes by run-away merging in young star clusters and the later dynamical evolution of star clusters containing massive black holes. We determine the initial conditions necessary for run-away merging to form a massive black hole and study the equilibrium profile that is established in the cluster center as a result of the interaction of stars with the central black hole. Our results show that star clusters which contain black holes have projected luminosity profiles that can be fitted by standard King models. The presence of massive black holes in (post-)core collapse clusters is therefore ruled out by our simulations.

scholarly journals GW190521 formation via three-body encounters in young massive star clusters

2021 ◽  
Author(s):  
Marco Dall’Amico ◽  
Michela Mapelli ◽  
Ugo N Di Carlo ◽  
Yann Bouffanais ◽  
Sara Rastello ◽  
...  
Keyword(s):  
Black Hole ◽  
First Generation ◽  
Massive Star ◽  
Second Generation ◽  
Star Clusters ◽  
Young Star ◽  
Mass Gap ◽  
Stellar Collisions ◽  
Three Body ◽  
Young Star Clusters

Abstract GW190521 is the most massive binary black hole (BBH) merger observed to date, and its primary component lies in the pair-instability (PI) mass gap. Here, we investigate the formation of GW190521-like systems via three-body encounters in young massive star clusters. We performed 2× 105 simulations of binary-single interactions between a BBH and a massive ≥60 M⊙ black hole (BH), including post-Newtonian terms up to the 2.5 order and a prescription for relativistic kicks. In our initial conditions, we take into account the possibility of forming BHs in the PI mass gap via stellar collisions. If we assume that first-generation BHs have low spins, $\sim {0.17}{{\ \rm per\ cent}}$ of all the simulated BBH mergers have component masses, effective and precessing spin, and remnant mass and spin inside the $90{{\ \rm per\ cent}}$ credible intervals of GW190521. Seven of these systems are first-generation exchanged binaries, while five are second-generation BBHs. We estimate a merger rate density $\mathcal {R}_{\rm GW190521}\sim {0.03}\,$Gpc−3 yr−1 for GW190521-like binaries formed via binary-single interactions in young star clusters. This rate is extremely sensitive to the spin distribution of first-generation BBHs. Stellar collisions, second-generation mergers and dynamical exchanges are the key ingredients to produce GW190521-like systems in young star clusters.

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