AGN Outflows: Part II

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AGN Outflows Part II

• Outflow Generation Mechanisms
• Models and Observations
• Leah Simon
• May 4, 2006

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Review Unified Model
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Review Outflows exist

• BALs (Broad Absorption Lines)
• Large velocity widths V(FWHM) gt 3000 km/s
• Within 60,000km/s of quasar redshift (v 0.2c)
• Variability timescales of year(s)
• Caused by continuum source variability affecting
  photoionized clouds
• Or caused by cloud (outflow) motion across LOS
• Partial coverage
• Continuum source is small!
• Cloud must be nearby if some continuum source
  can pass around cloud to our eye

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Review Acceleration Mechanisms

• Radiation Pressure (Photoionization)
• Line Driving momentum from radiation field
  through line opacity
• Expect vtransverse small
• Require very high L/LEdd
• Thermal Pressure (Parker Wind)
• Not strong enough
• Requires Isothermal wind...
• Magnetic Pressure (Magnetocentrifugal Driving)
• 'Beads on a string'
• See John Everett (CITA)

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MHD vs LD

• MagnetoHydroDynamics
• Does not necessitate shielding (over-ionization
  unimportant)
• Expected from collimated radio jets
• Predicts high velocity flows, and can move
  high-density gas

• Line Driving
• Requires shield to protect wind from inner x-ray
  radiation
• UV flux and wind velocities correlate
• Radiative momentum lost from continuum found in
  BALs
• Can explain relative X-ray and UV flux well
• Predicts high velocity outflows, but maybe
  densities too low

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Probably a combination of the the two methods
(Everett 2005, Proga, 2003). Need to constrain
models to distinguish between them!
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Fluid angular-momentum-conservation Not
magneto-centrifugal wind Mass loss through LD
at inner disk (fast stream) through MHD at outer
disk (slow stream)
Proga 2003 simulates MHDLD using both poloidal
and toroidal B-fields Similar to LD, but with
faster (slow) dense wind at outer disk
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Observational Evidence General Results
What's all the buzz?

• CIV width relates to Lxray Proga 2005, Proga
  Kallman 2004
• Are UV and and X-ray radiatively coupled?
• X-ray absorption Gallagher et al. 2006
• Hardest X-ray spectra are also weakest
  intrinsic absorption?
• Shielding and/or Over-ionization Proga, Everett,
  Murray et al. 1995
• Line driving requires shielding to protect from
  over-ionization
• Hot corona?

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Using Gravitational Lensing

• Use multiple LOS to compare structural models for
  BLR
• Virialized clouds (Kaspi Netzer 1999)
• Continuously outflowing wind ( Murray et al.
  1995)
• How it works
• observe lensed BALQSOs
• compare 2 observations
• Infer geometry based on
• variation among LOS

D. Chelouche, ApJ 2003
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Gravitational Lensing Results

• Chelouche finds lensed troughs are similar to
  within S/N for all but 2 quasars
• Single Cloud Model
• lateral size of clouds must be smaller than RS -
  expected based on partial coverage
• For non-varying clouds, must have lateral to
  radial aspect ratio 10-3 - Would be destroyed
  on dynamical timescale no coherent acceleration
  --NO
• Tube model - many (n) identical clouds with
  aspect ratio also ltlt 1 - alignment of tube over
  numerous LOS unlikely --NO
• Clumpy Wind Model
• Cloudlets imply statistical isotropy different
  LOS views same distribution variation should
  follow Poissonian distribution
• similarities imply nv gtgt1 and ntotgtgt100
• changes imply change in cloud distribution
  function YES
• implies isotropy on few arcsec scale BAL
  Outflow probably one or many sheets or cones with
  large lateral size not time- dependent
  dynamical wind

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Evidence for Multiphase Flows

• de Kool et al. 2001 observe disparate ionization
  states at similar velocities-conclude shielded
  gas at large distances (1kpc)
• Everett et al. 2002 re-evaluate and conclude
  multiphase flow, with continuous low-density wind
  and embedded high density clouds at small
  distances (4pc)
• Inner continuous region acts as shield, driven by
  MHD or failed LD
• Outer region is LD outflow, with lower
  ionizations
• Lowest ionizations found in dense embedded clouds
  ? Centrifugally driven disk wind? Turbulence?
  Shocks?

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Multiphase Flow in NALs?

• Observe CIV and CII at same velocities
• Initial distance determinations locate SiII very
  far from source (150 kpc)
• Combine with partial coverage in CIV!
• Could multiphase flow be a solution?

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Variability Test
Approximate Variability Timescales Accretion disk
size .1pc Light crossing time .35
years Viscous time 200 years Dynamical time
0.3 days Using M108Msun, R2x1014 3RS(X-ray
source size)
Observation Separation PKS 2204 13 years Q 0401
7 years PKS 2044 17 years Q 0249 14 years Q
0334 14 years
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Thanks!