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outflow generation mechanisms models and observations leah simon may 4 2006 n.
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AGN Outflows: Part II

AGN Outflows: Part II

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AGN Outflows: Part II

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  1. Outflow Generation Mechanisms: Models and Observations Leah Simon May 4, 2006 AGN Outflows: Part II

  2. Review: Unified Model

  3. Review: Outflows exist • BALs (Broad Absorption Lines) • Large velocity widths: V(FWHM) > 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

  4. 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)

  5. 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 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

  6. Probably a combination of the the two methods (Everett 2005, Proga, 2003). Need to constrain models to distinguish between them!

  7. 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 MHD+LD using both poloidal and toroidal B-fields Similar to LD, but with faster (slow) dense wind at outer disk

  8. What's all the buzz? Observational Evidence: General Results • 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?

  9. 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

  10. 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 << 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 >>1 and ntot>>100 • 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

  11. 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?

  12. 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?

  13. Variability Test Approximate Variability Timescales Accretion disk size ~ .1pc Light crossing time ~ .35 years Viscous time ~ 200 years Dynamical time ~ 0.3 days Using M=108Msun, R=2x1014 ~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

  14. Thanks!