Accretion Disks in AGNs

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

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

3. AGNSPEC -Hubeny & Hubeny 1997, 1998; Hubeny et al. (2000, 2001)

4. 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.)

5. 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.

6. 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).

7. 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 (Kishimoto’s talk later in this session). Ton 202 -Kishimoto et al. (2004)

8. (2) Microlensing observations have now placed constraints on the physical size of the optical continuum emitting region in many QSO’s. 0.33 0.1 -Pooley et al. (2006)

9. -Dai et al. (2006)

10. (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)

11. 5100/1350 -Bonning et al. (2006)

12. AGNSPEC Blackbodies -Davis et al. (2006)

13. SDSS data (4000-2200) (2200-1450) AGNSPEC AGNSPEC With E(B-V)=0.04 -Davis et al. (2006)

14. 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): prad>>pgas Hirose et al. (2006): prad<<pgas Krolik et al. (2006): prad~pgas

15. Radiation Magnetic times 10 Gas

17. Expect strong (but marginally stable) thermal fluctuations at low energy and stable (damped) fluctuations at high energy.

18. Gravity Total Magnetic Radiation Gas

19. CVI K-edge With magnetic fields No magnetic fields -Blaes et al. (2006)

20. Photosphere Photon Bubble Shock Train??? Parker Complex Structure of Surface Layers

21. 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 & Silant’ev 1978):

22. Photosphere Parker Unstable Regions MRI - the source of accretion power Parker Unstable Regions Photosphere Overall Vertical Structure of Disk with Prad~Pgas Pmag>Prad~Pgas Prad~Pgas>Pmag Pmag>Prad~Pgas