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Title page for ETD etd-03232015-173732

Type of Document Dissertation
Author Li, Baile
Author's Email Address baile.li@vanderbilt.edu
URN etd-03232015-173732
Title Supermassive black hole binary coalescence and orbital structure of the host galaxy
Degree PhD
Department Physics
Advisory Committee
Advisor Name Title
Dr. Kelly Holley-Bockelmann Committee Chair
Dr. Andreas A. Berlind Committee Member
Dr. David A. Weintraub Committee Member
Dr. Sait Umar Committee Member
Dr. Thomas J. Weiler Committee Member
  • orbital structure
  • supermassive black holes
  • galactic dynamics
  • n-body simulations
  • galactic nuclei
Date of Defense 2015-03-10
Availability unrestricted
When two galaxies coalesce, the supermassive black holes (SMBHs) at each galaxy center will

also coalesce. In spherical galaxies, there are not enough stars with centrophilic orbits to interact

with the black hole binary (BHB) to shrink the orbit enough to merge, and the binary stalls at

roughly 1 parsec. This is called the nal parsec problem". Previous investigations show that there

is no nal parsec problem in triaxial galaxies, since there are many centrophilic orbits in triaxial

galaxies that can easily interact with the BHB. However the question of whether black holes can

merge in an axisymmetric galaxy is still a matter of debate. Using N-body simulations, we classify

stellar orbits in an SMBH-embedded axisymmetric galaxy to probe the orbital types that could

interact with a BHB. We nd a rich variety of resonant orbits in the axisymmetric galaxy, which

do not exist in the spherical galaxy. The stellar mass in the loss cone is roughly 3 times of that of

the SMBH, which is sucient to make the SMBH binary merge. We also nd saucer and pyramid

orbits in our axisymmetric model, which are previously predicted in analytical potentials. Finally,

we nd that the shape of the nucleus is slightly triaxial.

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