BIFROST: simulating compact subsystems in star clusters using a hierarchical fourth-order forward symplectic integrator code

Rantala, Antti; Naab, Thorsten; Rizzuto, Francesco Paolo; Mannerkoski, Matias; Partmann, Christian; Lautenschütz, Kristina

doi:10.48550/arxiv.2210.02472

Cited by 3 publications

(2 citation statements)

References 117 publications

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“…N-body models for dense stellar systems can now reach the million-body region with high accuracy (Wang et al 2016;Arca-Sedda and Gualandris 2018;Panamarev et al 2019;Mukherjee et al 2023). New N-body codes, such as petar (Wang et al 2020), bifrost (Rantala et al 2022), andtaichi (Mukherjee et al 2023), including accurate integrators for binaries, make it possible to model NSCs with ten million bodies, where individual stars and binaries can be resolved. With high-resolution simulations, physical processes such as two-body relaxations, resonant relaxations, and stellar evolution can be self-consistently simulated to provide realistic models of NSCs that contain massive BHs.…”

Section: Perspectivementioning

confidence: 99%

Stellar Mergers in Dense Stellar Systems and growth of supermassive black holes

Wang

2022

Proc. IAU

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The rapid formation of supermassive black holes (SMBHs) at high redshifts is still a puzzle. One hypothesis is that intermediate-mass black holes (IMBHs) serve as seeds for their formation, which could arise from hierarchical mergers in dense star clusters. There are two possible pathways for IMBH formation: 1) very massive stars may form in young star clusters, such as Pop3 clusters, and evolve into IMBHs within a few million years; 2) multiple stellar-mass black holes can merge into IMBHs in dense nuclear star clusters. Detailed insights into these scenarios can be obtained through high-resolution star-by-star simulations of dense star clusters. Furthermore, upcoming observations of faint quasars, nuclear star clusters, and Pop3 stars with the James Webb Space Telescope (JWST) will offer valuable data to constrain theoretical models and deepen our understanding of the rapid formation of SMBHs.

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Section: Perspectivementioning

confidence: 99%

Stellar Mergers in Dense Stellar Systems and growth of supermassive black holes

Wang

2022

Proc. IAU

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“…Pelupessy & Portegies Zwart (2012) also studied the Hamiltonian splitting method for the evolution of embedded clusters using 𝑁body/SPH. For further acceleration, these methods have actively been implemented for accelerators (Rantala et al 2021(Rantala et al , 2022.…”

Section: Introductionmentioning

confidence: 99%

3D-Spatiotemporal Forecasting the Expansion of Supernova Shells Using Deep Learning toward High-Resolution Galaxy Simulations

Hirashima¹,

Moriwaki²,

Fujii³

et al. 2023

Preprint

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Small integration timesteps for a small fraction of short-timescale regions are bottlenecks for high-resolution galaxy simulations using massively parallel computing. This is an urgent issue that needs to be resolved for future higher-resolution galaxy simulations. One possible solution is to use an (approximate) Hamiltonian splitting method, in which only regions requiring small timesteps are integrated with small timesteps, separated from the entire galaxy. In particular, gas affected by supernova (SN) explosions often requires the smallest timestep in such a simulation. To apply the Hamiltonian splitting method to the particles affected by SNe in a smoothed-particle hydrodynamics simulation, we need to identify the regions where such SN-affected particles reside during the subsequent global step (the integration timestep for the entire galaxy) in advance. In this paper, we developed a deep learning model to predict a shell expansion after a SN explosion and an image processing algorithm to identify SN-affected particles in the predicted regions. We found that we can identify more than 95 per cent of the target particles with our method, which is a better identification rate than using an analytic approach with the Sedov-Taylor solution. Combined with the Hamiltonian splitting method, our particle selection method using deep learning will improve the performance of galaxy simulations with extremely high resolution.

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The growth of intermediate mass black holes through tidal captures and tidal disruption events

Rizzuto

Naab

Rantala

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We present N-body simulations, including post-Newtonian dynamics, of dense clusters of low-mass stars harbouring central black holes (BHs) with initial masses of 50, 300, and 2000 M⊙. The models are evolved with the N-body code bifrost to investigate the possible formation and growth of massive BHs by the tidal capture of stars and tidal disruption events (TDEs). We model star-BH tidal interactions using a velocity-dependent drag force, which causes orbital energy and angular momentum loss near the BH. About ∼20 − 30 per cent of the stars within the spheres of influence of the black holes form Bahcall-Wolf cusps and prevent the systems from core collapse. Within the first 40 Myr of evolution, the systems experience 500–1300 TDEs, depending on the initial cluster structure. Most (>95 per cent) of the TDEs originate from stars in the Bahcall-Wolf cusp. We derive an analytical formula for the TDE rate as a function of the central BH mass, density and velocity dispersion of the clusters ($\dot{N}_{\mathrm{TDE}} \propto M\mathrm{_{BH}}\rho \sigma ^{-3}$). We find that TDEs can lead a 300 M⊙ BH to reach ∼7000 M⊙ within a Gyr. This indicates that TDEs can drive the formation and growth of massive BHs in sufficiently dense environments, which might be present in the central regions of nuclear star clusters.

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BIFROST: simulating compact subsystems in star clusters using a hierarchical fourth-order forward symplectic integrator code

Cited by 3 publications

References 117 publications

Stellar Mergers in Dense Stellar Systems and growth of supermassive black holes

Stellar Mergers in Dense Stellar Systems and growth of supermassive black holes

3D-Spatiotemporal Forecasting the Expansion of Supernova Shells Using Deep Learning toward High-Resolution Galaxy Simulations

The growth of intermediate mass black holes through tidal captures and tidal disruption events

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