P1253553533cBXEt

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Radiation Hydrodynamic Simulations of
Super-Eddington Disk Accretion Flows 
(Ohsuga, Mori, Nakamoto, Mineshige 2005 Ohsuga
2006)
Ken OHSUGA Rikkyo University, Japan
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• Super-Eddington disk accretion flows
• The super-Eddington disk accretion (Mdot gt LE/c2
  LEEddington luminosity) is one of the
  important physics for formation of the SMBHs. The
  black holes can grow up rapidly.
• The super-Eddington accretion is thought to be an
  engine of the high L/LE objects, ULXs, GRBs,
  NLS1s, . .
• Also, mass outflow and radiation of the
  super-Eddington accretion flow would affect the
  evolution of the host galaxies.
• However, in the super-Eddington accretion, gas
  accretion might be prevented via the strong
  radiation pressure.
• We investigate the super-Eddington disk accretion
  flows by performing the 2D Radiation Hydrodynamic
  simulations.

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• Model Numerical Method
• Viscosity ?-viscosity (?0.1)
• Radiation Transfer Flux-limited-diffusion
  approximation
• Axisymmetry with respect to the rotation axis
• Explicit-implicit finite difference scheme on
  Eulerian grid (Spherical coordinates 96 x 96
  mesh)
• Size of computational domain 500rs
• Initial condition atmosphere (no disk)
• Free outer boundary
• absorbing inner boundary

• Matter (0.45 x Keplerian angular momentum) is
  continuously injected into the computational
  domain from the outer disk boundary.

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Radiation Energy Density
Gas Density
The quasi-steady structure of the super-Eddington
disk accretion flows is obtained by our
simulations.
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Quasi-steady Structure
Density Velocity fields
KH instability
Bubbles Circular Motion
Outflow
Mass-Accretion Rate
Mass-accretion rate decreases near the BH.
z/rs
BH
r/rs
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Radiation Energy Density
Radiation Pressure Gas Pressure
Quasi-steady Structure
Radiation Pressure-dominated Disk
Radiation Pressure-driven wind
Gas Temperature
High Temperature Outflow/Corona
Low Temperature Disk
Radial Velocity Escape Velocity
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Photon-Trapping
Transport of Radiation Energy in r-direction
z/rs
Viscous Heating
Radiation
Luminosity L/LE
Kinetic (Outflow)
2D RHD simulations
BH
r/rs
Mass-accretion rate
Radiation energy is transported towards the black
hole with accreting gas (photon-trapping).
We verify that the mass-accretion rate
considerably exceeds the Eddington rate and the
luminosity exceeds LE.
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Viewing-angle dependent Luminosity Image
Luminosity
L3.5LE
Density
Our simulations
4?D2F(?)/LE
Intensity Map
??
The observed luminosity is sensitive to the
viewing-angle. It is much larger than LE in the
face-on view.
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• Conclusions
• The mass accretion rate considerably exceeds the
  Eddington rate.
• ?The black hole can rapidly grow up due to the
  gas accretion.
• ?The growing timescale (M/Mdot) is around 106yr.
• The luminosity exceeds the Eddington luminosity.
  The apparent luminosity is more than 10 times
  larger than LE in the face-on view.
• ?The observed large luminosity of ULXs is
  explained by the super-Eddington accretion even
  if the IMBHs do not exist.
• The flow is geometrically optically thick and
  the radiation-pressure driven outflow is
  generated.
• We found that the photon-trapping plays an
  important role.

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Limit-cycle oscillations If the mass-accretion
rate moderately exceeds the Eddington rate, the
disk exhibits the quasar-periodic oscillations.
This phenomenon would occur at the end of the
super-Eddington growing phase.