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ACCRETION AND OUTFLOWS

ACCRETION AND OUTFLOWS

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ACCRETION AND OUTFLOWS

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  1. SUPERMASSIVE BLACK HOLES: ACCRETION AND OUTFLOWS Mitch Begelman JILA, University of Colorado

  2. COLLABORATORS: • Roger Blandford (KIPAC) • Mateusz Ruszkowski (JILA/MPA) • Marcus Brüggen (IU Bremen) • Eric Hallman (CASA, U. Colo.)

  3. WHY ARE OUTFLOWS INEVITABLE? • HOW DO SMBHs AFFECT THEIR SURROUNDINGS?

  4. WHY ARE OUTFLOWS INEVITABLE? • HOW DO SMBHs AFFECT THEIR SURROUNDINGS?

  5. DISKS PRODUCE JETS/WINDS BECAUSE THEY HAVE TROUBLE RADIATING AWAY ENOUGH OF THE LIBERATED ENERGY

  6. TWO KEY POINTS: • ENERGY, NOT ANGULAR MOMENTUM, IS THE CRUCIAL FACTOR • ENERGY ARGUMENT IS GENERIC, BUT THE DETAILS ARE DIVERSE AND SPECIFIC

  7. The role of angular momentum is that it must be transported outward – this can be done directly in a wind, or internally through torques

  8. Angular Momentum Flux: G Energy Flux: TORQUE TRANSPORTS ENERGY

  9. G IN A THIN ACCRETION DISK: Local rate of energy release: Local rate of dissipation: 2/3 of energy dissipated at R transported from <R by viscous torque

  10. Energy Transport: Bernoulli Function IN A RADIATIVELY INEFFICIENT ACCRETION FLOW (RIAF): G Energy transport from small R by torque unbinds gas at large R unless radiative efficiency > 2/3

  11. RIAFs areEXPLOSIVE ADIOS = 1 g of gas accreting at r ~ m can liberate 1 kg of gas at r ~ 1000 m* • Torque a “conveyor belt” for liberated energy • Flow must lose energy OR limit accretion • Mass loss or circulation • Small fraction of supplied mass reaches BH ADIABATIC INFLOW-OUTFLOW SOLUTION (Blandford & Begelman 99)

  12. 3 effects contribute to radiative inefficiency:

  13. 3 effects contribute to radiative inefficiency: • High accretion rate • gas highly opaque, radiates but photons can’t escape

  14. 3 effects contribute to radiative inefficiency: • High accretion rate • gas highly opaque, radiates but photons can’t escape • Low accretion rate • Dissipated energy goes mainly into protons • Protons-electron thermal coupling weak • gas is tenuous, falls into BH before radiating If:

  15. 3 effects contribute to radiative inefficiency: • High accretion rate • gas highly opaque, radiates but photons can’t escape • Low accretion rate • Dissipated energy goes mainly into protons • Protons-electron thermal coupling weak • gas is tenuous, falls into BH before radiating • Everything in-between? • Coronae are common, rad. eff. is a function of z

  16. Energy argument is generic… PHYSICALLY, WHAT DRIVES THE OUTFLOW or CIRCULATION? • Candidate mechanisms: • magnetic torques, flares - relativistic jets • radiation pressure - BALs, SS433 • radiative heating • Convection= “minimal” mechanism • all else being equal, adiabatic flows mustbe convectively unstable

  17. ADIOS behavior in MHD... Hawley & Balbus 02

  18. 2-D, adiabatic α-model Stone, Pringle & Begelman 99

  19. 2 complications to this picture…

  20. IF TORQUE IS EXTERNAL… HYDROMAGNETIC WINDremoves energy and angular momentum with no mass loss and negligible entropy generation. Blandford & Payne 82 -d EW = W dLW

  21. IF TORQUE IS EXTERNAL… HYDROMAGNETIC WINDremoves energy and angular momentum with no mass loss and negligibleentropy generation. Blandford & Payne 82 -d EW = W dLW …accreted close to supplied even larger wind power

  22. W W W BLACK HOLE SPIN: THE “OTHER” ENERGY SOURCE? • BH spin extractible magnetically • up to 0.29 M available • Field could connect ergosphere to disk, wind

  23. Amplification of B in plunge region Reynolds et al. 2006 h/r=0.1 ISCO

  24. 15 pc SgrA* Bipolar X-Ray Lobes Energy range 3.3 - 4.7 keV Adaptively smoothed, point-sources removed WEAK SOURCE: ADIOS? M. Morris et al. 2003

  25. Lobes are centered on the black hole, and perpendicular to the MW plane M. Morris et al. 2003

  26. ~ 1 pc There is also a Sgr A* Jet... F. Baganoff et al. 2003

  27. ~ 1 pc There is also a Sgr A* Jet... F. Baganoff et al. 2003

  28. M87 RADIO MONTAGE F. Owen (NRAO), J. Biretta (STScI), J. Eilek (NMIMT) 1999 Jet already exists at INTERMEDIATE POWER: JET POWERED BY BH SPIN OR INNER DISK? www.nrao.edu/~fowen/M87.html

  29. BAL Outflows in X-ray Absorption • NH ~ 1023 cm-2 • v ~ 0.2 c • W ~ 4p/10 ...driven by radiation pressure? QUASAR: POWERFUL OUTFLOW PG1115 Chartas et al. 2003

  30. WHY ARE OUTFLOWS INEVITABLE? • HOW DO SMBHs AFFECT THEIR SURROUNDINGS?

  31. Jets inject kinetic energy into their surroundings, but…

  32. …energy use depends on… • Rate of deposition • power vs. total output • intermittency? • Importance of cooling • Uniformity of gas • Clumpy: energy “goes around” the clumps • Gas in a disk may be immune • Directionality of outflow • Collimated jet vs. broad disk wind

  33. Why is “porosity” important? McKee & Ostriker 77 (ISM theory) Outflow only interacts with diffuse medium blasts out supersonically but has little effect on most of the mass Directionality: analogous effect – how can a powerful jet source continue to accrete?

  34. THE INTRACLUSTER MEDIUM • GAS RELATIVELY SMOOTH • COOLING TIME RELATIVELY LONG (COMPARED TO DYNAMICAL TIME) A CASE STUDY

  35. VIOLENT HEATING IS FAMILIAR… What does AGN heating look like? CYGNUS A in radio (VLA, 6cm) Energy injection concentrated into “hotspots” Elongated structure (momentum-dominated)

  36. undisturbed intergalactic gas “cocoon” (shocked jet gas) bow shock splash point backflow CYGNUS A – Exception rather than rule? Very powerful source in relatively tenuous ICM Most powerful RGs this age have: ~spherical cocoons subsonic expansion

  37. 3 STAGES of ENERGY INJECTION: • MOMENTUM-DRIVEN • ELONGATED COCOON • ENERGY-DRIVEN • SPHERICAL BLAST WAVE • BUOYANCY-DRIVEN • RISING BUBBLES SUPERSONIC, OVERPRESSURED SUBSONIC

  38. Cygnus A in X-rays (Chandra) – entering energy-driven phase

  39. 3 STAGES of ENERGY INJECTION: • MOMENTUM-DRIVEN • ENERGY-DRIVEN • BUOYANCY-DRIVEN SUPERSONIC, OVERPRESSURED LONGEST LASTING PHASE SUBSONIC MOST ENERGY

  40. MORPHOLOGICAL EVIDENCE OF GENTLE HEATING • Radio-filled bubbles and “ghost cavities” • Ripples • Plumes, eddies - connected to AGN

  41. 3C 84 and Perseus Cluster Fabian et al. 2000

  42. 3C 84 and Perseus Cluster Fabian et al. 2000 BUBBLES Radio emitting plasma fills holes Chandra image + radio

  43. Multiple “fossil” bubbles(?), not aligned with current radio jets 3C 84 and Perseus Cluster Fabian et al. 2000 Chandra image

  44. 3C 84 and Perseus Cluster Fabian et al. 2000 Cool rims Chandra image

  45. RIPPLES: PERSEUS CLUSTER Unsharp masked Chandra image X-ray temperatures 131 kpc Fabian et al. 2006

  46. RIPPLES: VIRGO CLUSTER Forman et al. 2004

  47. Two types of radio sources: FRI vs FRII PLUMES AND EDDIES M87 Cygnus A Carilli Cygnus A Young Forman

  48. M87 RADIO HALO Owen, Eilek & Kassim 1999 80 kpc VLA, 327 MHz www.nrao.edu/~fowen/M87.html

  49. M87 + core of Virgo cluster Chandra image + radio A. Young et al. 2002

  50. THE ICM NEEDS GENTLE, WIDESPREAD HEATING TO… • OFFSET “COOLING FLOWS” • EXPLAIN ENTROPY EXCESS IN CLUSTERS AND GROUPS