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AGN and Cooling Flows

AGN and Cooling Flows. E.Churazov (MPA/IKI). H.B öhringer, M.Brüggen, T.Ensslin, W.Forman, S.Heinz, C.Jones, C.Kaiser, R.Sunyaev. Same power: large g small g Same g : low power high power. Possible working model. AGN inflates bubbles (large power)

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AGN and Cooling Flows

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  1. AGN and Cooling Flows E.Churazov (MPA/IKI) H.Böhringer, M.Brüggen, T.Ensslin, W.Forman, S.Heinz, C.Jones, C.Kaiser, R.Sunyaev Same power: large g small g Same g : low power high power

  2. Possible working model • AGN inflates bubbles (large power) • Bubbles deposit energy to ICM (efficient, distributed) • AGN activity is self-regulated (e.g. Bondi accretion) • Universal for all clusters? • The only source of heat (Lx=Ljet)? • What sets Tmin (gravitational potential)? • Quasi-steady / strongly variable? • Is Bondi accretion rate sufficient? • Actual dissipation process • Abundance gradients to be preserved • Accretion modes • Black hole / galaxy mass correlation (ellipticals)

  3. Owen, Eilek, Kassim, 2000 => <= Gull & Northover, 1973

  4. Self-regulation • SMBH is at the bottom of the potential • Lowest entropy gas sinks to the bottom If cooling dominates => entropy goes down => accretion rate goes up => heating increases => entropy goes down

  5. Bubbles energy losses • Supersonic expansion => strong shocks => heating • Subsonic expansion => PdV, but no heating • Excited during bubble rise • Trapped in the central region (Balbus & Soker, 90; Lufkin et al. 95) • Distribute energy over 4 • Losses occur when bubble rises • Depends on the nature of friction force • High viscosity => dissipation • Low viscosity => • turbulence • internal waves • sound waves • Efficiency is high (~50%)

  6. Resonant scattering: optical depth

  7. APEC and MEKAL spectra

  8. Impact of resonant scattering on the line flux Turbulence > broader lines > lower depth; M ~ 0.5

  9. Dissipation of turbulent motions If 10 kpc

  10. Fe 6.7 keV line: Equivalent width and abundance Abundance Equivalentwidth

  11. Abundance gradients, turbulent transport • Forced convection • Turbulence in stratified gas (collapses to 2D?) • Internal waves

  12. Radio power in galactic BHC Fender et al.

  13. Fender et al.

  14. Cooling rate Cooling rate Weak No BH growth QSO BH growth

  15. Conclusions • AGN may prevent gas from cooling • Main source of heat? In every cluster? • Self-regulation is possible • Efficient and distributed dissipation is possible • Many interesting implications • Low frequency radio observations are very important • Velocity field / spatial scales (ASTRO-E2)

  16. Time scales • Cooling time: few 100 Myr • Relativistic electrons • X-ray holes

  17. Radial dependence of the optical depth A426

  18. Fender et al. 2000

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