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Nuclear Star Clusters and SMBHs: competitive feedback

Nuclear Star Clusters and SMBHs: competitive feedback. Sergei Nayakshin A. King, C. Power, S-H. Cha, A. Hobbs, M. Wilkinson (University of Leicester, UK). SMBHs and NCs. Ferrarese et al 2006 (cf. also Wehner & Harris 06) Black -- SMBH Red -- nuclear star clusters M < 10^8 Msun

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Nuclear Star Clusters and SMBHs: competitive feedback

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  1. Nuclear Star Clusters and SMBHs:competitive feedback Sergei Nayakshin A. King, C. Power, S-H. Cha, A. Hobbs, M. Wilkinson (University of Leicester, UK)

  2. SMBHs and NCs Ferrarese et al 2006 (cf. also Wehner & Harris 06) Black -- SMBH Red -- nuclear star clusters M < 10^8 Msun R ~ 3-10 pc

  3. Momentum feedback model For massive stars & BH Momentum flux in radiation Radiation drives winds  momentum flux in wind • Observational fact for massive stars • Pounds & King 2003, Pounds + 09 present observational evidence for such winds in SMBH with v ~ 0.1 c

  4. Weight of gas in the bulge For a DM potential with velocity dispersion Grav force (weight) at radius R Force balance King 2003, 2005

  5. Feedback from SMBHs and NCs Ferrarese et al 2006 Black -- SMBH Red -- nuclear star clusters (NCs) M < 10^8 Msun R ~ 3-10 pc

  6. Feedback from star clusters For massive stars Just need to count massive star fraction. For a young cluster with “normal” IMF Matches the observed offset well. McLaughlin, King & Nayakshin 2006

  7. Feedback from SMBHs and NCs Ferrarese et al 2006 Black -- SMBH Red -- nuclear star clusters (NCs) M < 10^8 Msun R ~ 3-10 pc

  8. Why do larger bulges prefer BHs to clusters? Nayakshin, Wilkinson & King 2009: • Time scales are important too. • SMBH growth is limited by the Eddington accretion rate, whereas star formation is not. Whereas star clusters can form on time scales of ~ 0.1 – few Myrs

  9. Bulge dynamical time – sigma relation From observed effective radius vs L and sigma vs L relations • In small (sigma < 100 km/s) bulges SMBH can’t grow quickly enough  such bulges will have “underweight” black holes

  10. Numerical method Spherically symmetric wind test • Nayakshin, Hobbs & Cha 09 • Massless particles used to model photons in Monte Carlo schemes • Absorption-on-the-spot approach used to model rapidly cooling winds • Similar to Dale & Bonnell method.

  11. Simulations in a static isothermal potential • SMBH is at the centre of the potential, radiating at its Eddington limit • A shell of gas is infalling with

  12. Simulations of Momentum Feedback (Nayakshin & Power, submitted)

  13. Fixed BH mass

  14. Eddington limited BH growth

  15. Unsolved problems • Spherically symmetric models -- feedback works, feeding NOT • Disc models – feeding works, feedback does NOT

  16. Summary SMBH and NCs influence their hosts via momentum feedback NCs form when BH fails to catch up with growing bulge No self-consistent model for feedback and feeding yet.

  17. Feedback in cosmological simulations Springel and Di Matteo 2005+++ model Sijacki, Springel + 2007

  18. Thermal feedback • Sazonov, Ostriker, Ciotti & Sunyaev 05: • Radiative heating of gas in the bulge by photoionisation and inverse Compton effect. • T_comp ~ 2 x 10^7 K (Sazonov +04) • Gas can be heated above T_vir

  19. Momentum Feedback: numerical method Source in a constant pressure medium test.  Momentum of wind particles must be << SPH particle momentum

  20. Rotating and moving shell Same DM + BH setup, but the shell is rotating + const v_x

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