Post-Newtonian Dynamical Modeling of Supermassive Black Holes in Galactic-scale Simulations

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http://hdl.handle.net/10138/214444

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Rantala , A , Pihajoki , P , Johansson , P H , Naab , T , Lahen , N & Sawala , T 2017 , ' Post-Newtonian Dynamical Modeling of Supermassive Black Holes in Galactic-scale Simulations ' , Astrophysical Journal , vol. 840 , no. 1 , 53 . https://doi.org/10.3847/1538-4357/aa6d65

Title: Post-Newtonian Dynamical Modeling of Supermassive Black Holes in Galactic-scale Simulations
Author: Rantala, Antti; Pihajoki, Pauli; Johansson, Peter H.; Naab, Thorsten; Lahen, Natalia; Sawala, Till
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2017-05-01
Language: eng
Number of pages: 25
Belongs to series: Astrophysical Journal
ISSN: 0004-637X
URI: http://hdl.handle.net/10138/214444
Abstract: We present KETJU, a new extension of the widely used smoothed particle hydrodynamics simulation code GADGET-3. The key feature of the code is the inclusion of algorithmically regularized regions around every supermassive black hole (SMBH). This allows for simultaneously following global galactic-scale dynamical and astrophysical processes, while solving the dynamics of SMBHs, SMBH binaries, and surrounding stellar systems at subparsec scales. The KETJU code includes post-Newtonian terms in the equations of motions of the SMBHs, which enables a new SMBH merger criterion based on the gravitational wave coalescence timescale, pushing the merger separation of SMBHs down to similar to 0.005 pc. We test the performance of our code by comparison to NBODY7 and rVINE. We set up dynamically stable multicomponent merger progenitor galaxies to study the SMBH binary evolution during galaxy mergers. In our simulation sample the SMBH binaries do not suffer from the final-parsec problem, which we attribute to the nonspherical shape of the merger remnants. For bulge-only models, the hardening rate decreases with increasing resolution, whereas for models that in addition include massive dark matter halos, the SMBH binary hardening rate becomes practically independent of the mass resolution of the stellar bulge. The SMBHs coalesce on average 200 Myr after the formation of the SMBH binary. However, small differences in the initial SMBH binary eccentricities can result in large differences in the SMBH coalescence times. Finally, we discuss the future prospects of KETJU, which allows for a straightforward inclusion of gas physics in the simulations.
Subject: black hole physics
galaxies: evolution
galaxies: nuclei
methods: numerical
stars: kinematics and dynamics
FINAL-PARSEC PROBLEM
LONG-TERM EVOLUTION
EARLY-TYPE GALAXIES
N-BODY SIMULATIONS
SPHERICAL STELLAR-SYSTEMS
DARK-MATTER HALOS
A NUMERICAL CODE
COSMOLOGICAL SIMULATIONS
ELLIPTIC GALAXIES
STAR-FORMATION
115 Astronomy, Space science
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