1. The cold component of cluster accretion Yuval Birnboim Jerusalem 2011

2. Clusters should be simple! Abell 1689 Composite: X-ray(Chandra) + Optical (HST)

3. The cooling flow Problem in Cool Core Clusters 1.No cool (<1keV) gas 2.Star formation in brightest central galaxy lower by 10-100 than expected from cooling 3.BCG smaller by a factor or a few than expected (“failure to thrive”) Allen & Ebeling

4. Cool Core Cluster properties Cavagnolo et al. 2009 Leccardi & Molendi 2008 Reiprich 2003 M(BCG) ≤ 10 12 M  SFR≤20 M  /yr Lx~10 44 -10 45 erg/sec S core ~20KeV cm 2

5. Overcooling. M vir =3X10 14 M ʘ

6. Immediate suspect: AGNs M87 – HST image Artist’s impression for supermassive black hole, NASA/JPL- Caltech

7. Criteria for cluster heat source 1) Enough energy 2) Smooth in time (t off <t cool ) 3) Smooth in space (<10kpc) 4) No explosions, please

8. Accretion and Gravitational heating in Clusters Dekel & Birnboim 2008 Dekel et al. 2009

9. Courtesy of Volker Springel Clusters are not smooth!

10. Clump physics Heating by baryonic cold (10^4K) clumps 1.Hydrodynamic drag:

11. Clump physics Heating by baryonic cold (10^4K) clumps 1.Hydrodynamic drag 2.Jeans mass (Bonnor-Ebert) 3.K-H/R-T instabilities and clump fragmentation 4.DF 5.Conduction/evaporation (Gnat et al. 2010) 1gr/cm^3 10 -3 gr/cm^3 Heating

12. Gravitational heating by clumps Murray & Lin 2004 Dekel & Birnboim 2008

13. Cold gas in Perseus Conselice et al. 2001 Mass of structures: 10 6 -10 8 M ⊙ (Fabian et al. 2008) HVCs in MW

14. Dynamic response Problems with static calculations: Cold mass is dumped near center Energy injection is not self regulated Timescale of clumps: many Gyrs Problems with full 3D hydro: Resolution Subgrid 1D model: clump shells interact with gas At clump destruction – cold mass added in situ

15. No clump simulation – Overcooling M vir =3X10 14 M ʘ

16. 5% of baryons in clumps of 10 8 M ⊙

17. Convection Stability Maximal convection (v bubbles =c s ) Mixing length theory (implicit scheme)

18. 5% of baryons in clumps of 10 8 M ⊙ Clumps + Convection

19. Birnboim and Dekel. 2011

20. Summary Gravitational infall is a powerful engine Clumps interact with gaseous haloes – and heat them The inherit instability drives convection