The cooling flow problem

1. The cooling flow problem AC Fabian With thanks to: Lisa Voigt, Jeremy Sanders, Carolin Crawford, Roderick Johnstone, Glenn Morris, Steve Allen

2. Evidence for cooling: tcool T OVI CO

3. Evidence for cooling: Allen et al 01 tcool Voigt & F 03

4. Evidence for cooling: tcool The centres of cooling flow clusters are special! T OVI CO

5. Evidence of a problem:XMM/RGS Sakelliou et al 02 Gas drops to Tmin~0.3Tvir Chandra spectra consistent (<Tmin)~(0.1-0.2) Peterson et al 01,02 McNamara et al ; David et al ; Allen et al; Blanton et al ; Buote et al………

6. Result not explained by just heating gas at Tmin or just rearranging gas • Since and at 1keV at constant P • The cooler the gas, the faster it cools • Why doesn’t it cool?

7. The cooling flow problem Why, and how, is the cooling of gas below Tvir/3 suppressed? Significance The stellar/gaseous parts of galaxies are due to the cooling of gas in their DM potential wells Cooling in clusters and groups should be an observable example of this process. The suppression of cooling in these objects may explain the upper mass cutoff of galaxies.

8. Possible solutions of the CFP • Absorption1,2 missing soft X-ray • Mixing3,4 luminosity ~ LUV • Inhomogeneous metallicity5,6 • Heating ─ from outside7-9 ─ from centre (AGN)10-15 ─ non-steady16-18 ─ combinations21,22 ─other

9. 1,2 Johnstone et al; White et al 93 3,4 Fabian et al 01,02; Soker et al 03 5,6 Fabian et al 01; Morris & Fabian 02 7-9 Narayan & Medvedev 01; Gruzinov 02; Voigt et al 02 10-20 Tucker & Rosner 83; Binney & Tabor 93; Churazov et al 00;01;Bohringer et al 02; Bruggen & Kaiser 01, 02; Reynolds et al 02; Begelman 01; Ruszkowski & Begelman 02; Brighenti & Mathews 03; Soker et al 01; Ciotti & Ostriker 01; Quilis et al 02; Kaiser & Binney 02; Buson & Alexander 03; De Young 03 Makishima et al 00

10. Heat must be distributed Voigt et al 03

11. Further data issues: Cool bubble rims smoothness smoothness Abundance gradients smooth tcool/entropy profile Faraday rotation

13. Energetics 1045 erg s-1 if continuous or 1046 if sporadically heated for 10% of the time Can a combination work over 104 in LX and 30 in kT? Wider issues of heating and cooling for clusters (LX, TX etc)

14. Conduction Works for some? eg if kT >5 keV eg A2029 What is κ? Voigt & Fabian 03

15. AGN/Radio source • Most CF have one, but no obvious correlation  non-steady? Voigt & F 03 • Extreme energies required for luminous clusters, eg A1835, RXJ1347

16. The Perseus bubbles

17. New clues from deep Chandra observations of Perseus Fabian et al 03a,b

18. Ripples and weak shocks • Bubbles make sound wave of long period (~107 years). Create weak shocks with some dissipation. • Further out, dissipation depends on viscosity. What is viscosity? ν~108T 5/2n -1 Weak shock to NE Viscous heating=rad. cooling in inner 50 kpc of Perseus

19. Conselice et al 01 WIYN telescope

20. Outer bubble in Perseus • Hα streamlines  flow laminar • Re<1000  viscosity > 4x1027 (cgs) Fabian et al 03b

21. Collisional viscosity • Has similar temperature dependence to conduction • But… MHD effects? • Viscous dissipation could be crucial • Turns sound energy from core and outer parts (refracted into core Pringle 89) into heat

22. Conclusions • Cooling flow problem is widespread and plays a significant role in massive galaxy formation • Many solutions proposed but all have drawbacks • Knowledge of transport processes in ICM may be crucial to the solution

25. Non X-ray evidence for cool gas and young stars Optical: Crawford et al 99 UV: Oergerle et al 01 CO: Edge 02 Dust: Edge et al 99

26. 75 kpc A2199: Johnstone et al 02

27. Brighenti & Mathews 03

28. M87 Wilson et al 02 Owen et al 99

29. Fabian et al 02

30. Radiative cooling times from Chandra 108yr 109yr Other clusters Perseus cluster