1. Does AGN “Feedback” in Galaxy Clusters Work? Dave De Young NOAO Girdwood AK May 2007

2. AGN Outflows (“Feedback”) • Relevant to Galaxy Formation and Evolution • Relevant to Evolution of the Intracluster Medium and BCGs • Can Provide Information on Unknown Parameters of AGN Formation and Evolution

3. Galaxy Formation and Evolution • Millennium Simulation 10 3 1 x 10 Particles; 500Mpc

4. Galaxy Formation and Evolution Bower et al. 2003

5. Galaxy Formation and Evolution • Effects of Radio AGN Croton et al. 2006

6. Evolution of The Intracluster Medium and BCGs • Central Cluster Galaxies Should Now be Accreting ICM, Forming Stars (CDM) • Not Seen • Massive Elliptical Galaxies in Clusters are Old and Red • No Evidence of Significant Star Formation in Central BCGs

7. Evolution of The Intracluster Medium and BCGs • ICM Cooling Times < Hubble Time in Cores • Inflow Rates Up 100 M(solar) /yr • Not Seen • “Cooling Flow” Problem • Reheating by Cluster AGN • Old Idea (~ 1970s) : Total Energies Suggestive

8. AGN Outflows • Key Issue: Coupling of AGN Outflow to Surrounding Medium • Requires Understanding of the Interaction of AGN Outflows with the Ambient Medium • Exchange of E, M, p • May Constrain Outflow Parameters (v, , ) ifAmbient Medium, Interaction Known

9. Radio Source Bubbles and Cooling “Flows” (cf. B. McNamara) • Total Radio Source Energies (pdV) Are a Significant Fraction of ICM Energy Budget • Need to Convert Kinetic and Particle Energy into Heat • Via Turbulent Mixingwith ICM • Via Advection and Mixing ofICM • Via Shocks in ICM • Is There Enough Time to Do This?

10. Models of Buoyant Radio Source Bubbles Density • 2-D Hydrodynamic • Abundant Mixing! X-Y High Resolution Brueggen & Kaiser 2002

11. Models of Buoyant Radio Source Bubbles • 3-D Hydrodynamic • Fragmentation, Mixing Ruszkowski, Bruggen, & Begelman 2004

12. Self Consistent Global Mixing Calculation Not yet Done. But It’s Suggestive… However…

13. Relic Sources in Clusters N1275 • Intact! • At Times >> t instab Fabian et al. 2002

14. Consequences of Relic Radio Sources • Role of Magnetic Fields: • Does Bubble Expansion Creates Stabilizing Sheath? • Linear Stability Analysis: • At r ~ 50 kpc, n = 0.01, B = 3 x 10 G: • R-T: l = 13 kpc, t = 7 x 10 yr • K-H: Stable for U ~ 0.1 c • Possible Suppression of Fragmentation or Mixing for a Significant Fraction of Buoyant Risetime -6 7 O O s

15. Current MHD Calculations ( With T. W. Jones, S. O’Niell) • Time Dependent Evolution of Buoyant Radio Relics in a Stratified ICM – Look At: • R – T Instability • Lifting and Mixing of Different Elements of the ICM • Destruction of Relic and Mixing with ICM • Includes Effects of Central Galaxy + Cluster • Includes Inflation of Radio Relic Bubble

16. Initial & Boundary Conditions • Gravitation – Includes Dark Matter • Central Galaxy • King Model; Mc = 3 kpc; M = 3.5 x 10(12) Mo at 20 kpc • Cluster • NFW Model; alpha = 0; M = 3.5 x 10(10) Mo at 10 kpc • Cluster Core = 400 kpc; M = 3.5 x 10(12) Mo at 50 kpc • ICM – Equilibrium Configuration • Isothermal – T = 3 keV = 3.5 x10(7) K • Density n = 0.1 at z = 5 kpc

17. Initial & Boundary Conditions • ICM – Equilibrium Configuration • Magnetic Field • Orientation: Phi = 0, 45, 90 • B = const or Beta = const (120 – 75K) • |B| = 0.2, 1, 5 MicroGauss (Beta = 7.5(4), 3(3), 120) • Bubble • R = 2 kpc • P = Pext at z = 15 kpc • n = 0.01n at z = 15 kpc • Inflation time ~ 10 Myr • dE/dt ~ 10 (42) erg/s

18. Relic Radio Bubble Evolution • Beta = 3000 • Bo = 1 Microgauss • Internal B Parallel at Top

19. Relic Radio Bubble Evolution • Beta = 120

20. Three Dimensional MHD Calculations •  = 3000 • Same Initial Conditions as 2D Cases Bubble Material Volume Rendered t = 12.5 Myr

21. Three Dimensional MHD Calculations •  = 3000 t = 75 Myr t = 150 Myr

22. Three Dimensional MHD Calculations •  = 3000

23. Three Dimensional MHD Calculations •  = 120 bubble only t = 150 Myr t = 75 Myr

24. Three Dimensional MHD Calculations •  = 120

25. Consistency with Observations  = 3000  = 120

26. Next … • Really Tangled Fields

27. Bubbles with Tangled Interior Fields • Beta = 120 • t = 75 Myr

28. Bubbles with Tangled Interior Fields • Beta = 120 • t = 75 Myr

29. Conclusions – AGN Outflows and Reheating of the Ambient Medium • Radio Lobe Interaction with a Magnetized ICM Indicates: • Delay of Onset of Destructive Instabilities • Longer Times for Mixing with the ICM • Bubbles Decelerated, Evolution Subsonic • Volume of Lifted ICM Limited to Wake Region • Repeated Outbursts and/or Additional Mixing Mechanisms May be Needed to Reheat the ICM

30. Conclusions – AGN Outflows and Reheating of the Ambient Medium • AGN Reheating Needed in CDM Galaxy Formation • Common FR-I Outflows May Show Strong Local Coupling • Self Consistent Heating Rates not Yet Calculated • AGN Outflows in Clusters – Stop Cooling Flows? • Hydro Calculations Suggestive • Relic Radio Source Cavities Intact and Suggest Interaction with a Magnetized ICM

31. Consequences of B Fields • For Cluster ICM Reheating • Onset of Instability and Mixing Delayed • Initial Scale Length Large: l ~ 10 kpc • Mixing Time to Reheat Will Be Long - • Time Required for Turbulent Cascade to Go From Energy Range to Dissipation Range • l /v ~ 3 x 10 yr o 7 o turb

32. Other Possible Heating Processes Due to Radio Sources • Sound Waves? • Shock Waves? P/P Fabian et al. 2005

33. Impact of Radio Source Cavities • Complex ICM Structure – Centaurus Cluster Fabian et al. 2005 0.4 – 7 keV + 1.4 GHz

34. Other Possible Heating Processes – Shock Waves • Shock Waves: • Must be Supersonic • Sound Speed ~ 10  T •  Bubble Expansion Speed > 10 cm/s • Likely to be Weak and Short Lived • T* /T  M, so T Not Large • Bubbles Currently Subsonic • Volume Heated Will be Small • Damped Shocks Become Sound Waves • Thus a Local Phenomenon 4 8

35. Other Possible Heating Processes – Dissipation of Sound Waves • Dissipation of Sound Waves • Some Models Assume pdV Energy Dissipated in Cluster Core • Others – Approximate Dissipation (no B, no Thermal Conductivity, Incompressible) • L  (3/8 ) c / ~ 100 kpc • Issue Not Yet Clear • How Much? • How Long? 2 2 Ruszkowski et al. 2004

36. Non-Linear R-T Instability t = 0 Beta = 1.3 M Beta = 1.3 K 130 ~ ICM 1 kpc slices T = 10M K t = 15 Myr

37. Prior MHD Calculations • 2-D MHD – Pre-formed Bubble • Tangential Field Inserted “By Hand” • Self Consistent MHD (Robinson et al. 2004) Breuggen & Kaiser 2001

38. Relic Radio Bubble Evolution • Bubble Deceleration

39. Lifting and Mixing Beta = 120K OptimallyCoupled Ambient ICM

40. Relic Radio Bubble Evolution • Beta = 3000 • Bo = 1 Microgauss; Internal B Antiparallel at Top 12.5 Myr 75 125

41. Relic Sources in Clusters • 200 kpc Cavities (McNamara et al. 2005) • MS0735 • Z = 0.22 • pdV ~ 10 erg 62

42. Initial Conditions

43. Properties of Radio Source Cavities and Shells • Morphology • Limb Brightened, “Relaxed” Structure • NOT Head-Tail or “Normal” FR-I • Small/No Jets, but t ~ 10 yr • Tens of kpc in Diameter • Inferred Properties • In Pressure Equilibrium • Moving Subsonically (no Shocks) • Shell and Surroundings Cool • Buoyant Bubbles 7 syn

44. Relic Radio Bubble Evolution • Beta = 3000 • Bo = 1 Microgauss • Internal B Anti-parallel at Top

45. Three Dimensional MHD Calculations •  = 75000 Bubble Only - Volume Rendered

46. Models of Buoyant Radio Source Bubbles • 3-D Hydrodynamic 10 x 10 x 30 kpc 8 Myr 25 Myr 41 Myr 59 Myr Density Brueggen et al. 2002

47. Evolution of The Intracluster Medium and BCGs • Related to Previous Problem in ΛCDM Cosmology Models • Large ΛCDM Halos Form Late, Correspond to Massive Clusters Z = 0, M/L = Const