The goal of this thesis is to study hierarchical mergers of binary black holes in evolving nuclear star clusters. Nuclear star clusters are dense and heavy objects located at the center of galaxies. Their mass and density can go up to a hundred million solar masses and a hundred thousand solar masses per parsec cube. Such conditions prove excellent to study hierarchical mergers. We begin by modeling a nuclear star cluster that is growing by star cluster infall through dynamical friction. Our goal is an expression for NSC mass that is growing with time. From this mass, we can infer the size of the NSC. These two quantities are sufficient to derive the necessary physical properties like escape velocity and density. We then implement this model into the FASTCLUSTER code, intensively updating the code in the process. To simulate the phenomenon, we also create a black hole library that is forming in the star clusters. We run 12 different simulations, varying the mass of galaxies, type of galaxies, and initial population of black holes. We find that not all nuclear star cluster are excellent for hierarchical mergers. Small escape velocity in lighter nuclear star clusters and long dynamical timescales in heavier nuclear star clusters stops hierarchical mergers. We also find that changing the initial mass population of black holes from local black holes produced in the nuclear star cluster to migratory black holes originating in star clusters heavily alter the binary black hole dynamics inside. We find that only a few NSCs are capable of producing black holes with mass greater than 1000 solar masses. Finally, we compare our results with gravitational wave events to understand if our simulations are able to reproduce those events.

The goal of this thesis is to study hierarchical mergers of binary black holes in evolving nuclear star clusters. Nuclear star clusters are dense and heavy objects located at the center of galaxies. Their mass and density can go up to a hundred million solar masses and a hundred thousand solar masses per parsec cube. Such conditions prove excellent to study hierarchical mergers. We begin by modeling a nuclear star cluster that is growing by star cluster infall through dynamical friction. Our goal is an expression for NSC mass that is growing with time. From this mass, we can infer the size of the NSC. These two quantities are sufficient to derive the necessary physical properties like escape velocity and density. We then implement this model into the FASTCLUSTER code, intensively updating the code in the process. To simulate the phenomenon, we also create a black hole library that is forming in the star clusters. We run 12 different simulations, varying the mass of galaxies, type of galaxies, and initial population of black holes. We find that not all nuclear star cluster are excellent for hierarchical mergers. Small escape velocity in lighter nuclear star clusters and long dynamical timescales in heavier nuclear star clusters stops hierarchical mergers. We also find that changing the initial mass population of black holes from local black holes produced in the nuclear star cluster to migratory black holes originating in star clusters heavily alter the binary black hole dynamics inside. We find that only a few NSCs are capable of producing black holes with mass greater than 1000 solar masses. Finally, we compare our results with gravitational wave events to understand if our simulations are able to reproduce those events.

Binary Black Holes in Nuclear Star Clusters: Dynamics and Time Evolution

MEHTA, DAXAL HEMENDRAKUMAR
2022/2023

Abstract

The goal of this thesis is to study hierarchical mergers of binary black holes in evolving nuclear star clusters. Nuclear star clusters are dense and heavy objects located at the center of galaxies. Their mass and density can go up to a hundred million solar masses and a hundred thousand solar masses per parsec cube. Such conditions prove excellent to study hierarchical mergers. We begin by modeling a nuclear star cluster that is growing by star cluster infall through dynamical friction. Our goal is an expression for NSC mass that is growing with time. From this mass, we can infer the size of the NSC. These two quantities are sufficient to derive the necessary physical properties like escape velocity and density. We then implement this model into the FASTCLUSTER code, intensively updating the code in the process. To simulate the phenomenon, we also create a black hole library that is forming in the star clusters. We run 12 different simulations, varying the mass of galaxies, type of galaxies, and initial population of black holes. We find that not all nuclear star cluster are excellent for hierarchical mergers. Small escape velocity in lighter nuclear star clusters and long dynamical timescales in heavier nuclear star clusters stops hierarchical mergers. We also find that changing the initial mass population of black holes from local black holes produced in the nuclear star cluster to migratory black holes originating in star clusters heavily alter the binary black hole dynamics inside. We find that only a few NSCs are capable of producing black holes with mass greater than 1000 solar masses. Finally, we compare our results with gravitational wave events to understand if our simulations are able to reproduce those events.
2022
Binary Black Holes in Nuclear Star Clusters: Dynamics and Time Evolution
The goal of this thesis is to study hierarchical mergers of binary black holes in evolving nuclear star clusters. Nuclear star clusters are dense and heavy objects located at the center of galaxies. Their mass and density can go up to a hundred million solar masses and a hundred thousand solar masses per parsec cube. Such conditions prove excellent to study hierarchical mergers. We begin by modeling a nuclear star cluster that is growing by star cluster infall through dynamical friction. Our goal is an expression for NSC mass that is growing with time. From this mass, we can infer the size of the NSC. These two quantities are sufficient to derive the necessary physical properties like escape velocity and density. We then implement this model into the FASTCLUSTER code, intensively updating the code in the process. To simulate the phenomenon, we also create a black hole library that is forming in the star clusters. We run 12 different simulations, varying the mass of galaxies, type of galaxies, and initial population of black holes. We find that not all nuclear star cluster are excellent for hierarchical mergers. Small escape velocity in lighter nuclear star clusters and long dynamical timescales in heavier nuclear star clusters stops hierarchical mergers. We also find that changing the initial mass population of black holes from local black holes produced in the nuclear star cluster to migratory black holes originating in star clusters heavily alter the binary black hole dynamics inside. We find that only a few NSCs are capable of producing black holes with mass greater than 1000 solar masses. Finally, we compare our results with gravitational wave events to understand if our simulations are able to reproduce those events.
dinamical formation
Hierarchical mergers
Coalescing black
Gravitational waves
star cluster
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12608/45472