Accretion%20Disks%20in%20AGNs

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Accretion Disks in AGNs
Omer Blaes University of California, Santa Barbara
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Collaborators

• Spectral Models Shane Davis, Ivan Hubeny
• Numerical Simulations Shigenobu Hirose, Neal
  Turner
• Simulation Analysis and Theory Julian Krolik

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AGNSPEC
-Hubeny Hubeny 1997, 1998 Hubeny et al. (2000,
2001)
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• The Good
• Models account for relativistic disk structure
  and relativistic
• Doppler shifts, gravitational redshifts, and
  light bending in
• a Kerr spacetime.
• Models include a detailed non-LTE treatment of
  abundant
• elements.
• Models include continuum opacities due to
  bound-free and
• free-free transitions, as well as
  Comptonization. (No lines
• at this stage, though.)

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• The Bad --- Ad Hoc Assumptions
• Stationary, with no torque inner boundary
  condition.
• ?R???Ptot with ? constant with radius -
  determines surface
• density.
• Vertical structure at each radius depends only
  on height
• and is symmetric about midplane.
• Vertical distribution of dissipation per unit
  mass assumed
• constant.
• Heat is transported radiatively (and not, say,
  by bulk
• motions, e.g. convection).
• Disk is supported vertically against tidal field
  of black
• hole by gas and radiation pressure only.

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LMC X-3 in the thermal dominant state
BeppoSAX
RXTE
-Davis, Done, Blaes (2005)
The same sort of accretion disk modeling that has
been attempted for AGN works pretty well for
black hole X-ray binaries (BHSPEC, Davis et al.
2005, Davis Hubeny 2006).
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Some Recent Observational Developments That Have
Direct Bearing on Our Understanding Of Accretion
Disks in AGN

• Spectropolarimetry has succeeded in removing BLR,
  NLR,
• and dust emission in the optical and
  infrared, revealing the
• underlying broadband continuum shape for the
  first time
• (Kishimotos talk later in this session).

Ton 202
-Kishimoto et al. (2004)
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(2) Microlensing observations have now placed
constraints on the physical size of the
optical continuum emitting region in many
QSOs.
0.33
0.1
-Pooley et al. (2006)
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-Dai et al. (2006)
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(3) Reverberation mapping leveraged by BLR
radius/continuum luminosity correlations has
given a method of getting approximate black
hole masses for the huge number of SDSS
quasars.
5100/4000
4000/2200
2200/1350
-Bonning et al. (2006)
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5100/1350
-Bonning et al. (2006)
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AGNSPEC
Blackbodies
-Davis et al. (2006)
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SDSS data
(4000-2200)
(2200-1450)
AGNSPEC
AGNSPEC With E(B-V)0.04
-Davis et al. (2006)
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? begone!!!
Thermodynamically consistent, radiation MHD
simulations of MRI turbulence in vertically
stratified shearing boxes are telling us a lot
about the likely vertical structure of accretion
disks.
Turner (2004) pradgtgtpgas Hirose et al. (2006)
pradltltpgas Krolik et al. (2006) pradpgas
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Radiation
Magnetic times 10
Gas
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(No Transcript)
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Expect strong (but marginally stable) thermal
fluctuations at low energy and stable (damped)
fluctuations at high energy.
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Gravity
Total
Magnetic
Radiation
Gas
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CVI K-edge
With magnetic fields
No magnetic fields
-Blaes et al. (2006)
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Complex Structure of Surface Layers
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Spectral Consequences

• Magnetically supported upper layers decrease
  density at
• effective photosphere, resulting in increased
  ionization and
• a hardening of the spectrum.
• Strong (up to factor 100) irregular density
  inhomogeneities
• exist well beneath photosphere of horizontally
  averaged
• structure. They will soften the spectrum.
• Actual photosphere is therefore complex and
  irregular,
• which will reduce intrinsic polarization of
  emerging photons
• (Coleman Shields 1990). Magnetic fields may
  also
• Faraday depolarize the photons (Gnedin
  Silantev 1978)

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Overall Vertical Structure of Disk with PradPgas
PmaggtPradPgas
PradPgasgtPmag
PmaggtPradPgas