Robyn Levine 1,2

1
Growing Supermassive Black Holes in
Cosmological AMR Simulations

• Robyn Levine 1,2
• Nick Gnedin 2,3
• Andrew Hamilton 1

1. JILA, University of Colorado 2. Fermilab
3. University of Chicago
2
Why use adaptive techniques?

• Small scale-physics
• (hydrodynamics, radiative transfer, etc)
• cosmological context
• (major evolutionary events)
• ? need a LARGE dynamic range!

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Hydrodynamic Adaptive Refinement Tree(a
cosmological hydrodynamic code)

• Includes
• dark matter, stars, gas dynamics
• star formation and feedback
• physics of the ISM
• radiative transfer
• gas cooling by heavy elements and dust under the
  assumption of collisional ionization equilibrium

(Kravtsov, Klypin, Khokhlov)
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Using the Zoom-in Approach

• Initial conditions 1,700 kpc cosmological
  simulation with a single milky way progenitor
  galaxy (resolution of 50 pc-- 9 refinement
  levels)
• 1.5 kpc region centered on galaxy allowed to
  refine further
• replace gas from densest region with a
  supermassive black hole
• measure accretion of matter and follow the
  transport of angular momentum on different scales
• repeat above process at different cosmological
  epochs, measuring accretion rates as a function
  of time
• Quite feasible to conduct parallel tests
  involving different physical processes!

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Zooming in
(similar to simulations of the 1st star by Abel,
Bryan, and Norman (2002))
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Density Profile
10 orders of magnitude!
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Questions about SBH growth

• Mass accretion rates?
• dark matter, stars, gas
• time, radial dependence
• Angular momentum?
• Feedback effects?
• opening angle
• efficiency
• Merger rate?

Drawing Credit A. Hobart, CXC
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• Average gas accretion rate over time from a very
  simple run
• Initial simulation z 4
• BH mass 3?107 M?
• maximum refinement level 15 (0.8 pc)
• no feedback!
• measurement of accretion rates non-trivial!

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Summary Future Direction

• The technique of AMR allows us to measure
  accretion rates on a computationally challenging
  wide range of scales at many different epochs,
  including realistic evolutionary events and
  small-scale physics.
• The approach is complimentary to observational,
  semi-analytic and other numerical methods of
  studying SBH growth, and will provide useful
  boundary conditions for simulations of accretion
  disks.
• The inclusion of feedback and eventually mergers,
  will soon give an even more realistic picture of
  SBH growth.