1. XMM-Newton and Galaxy Clusters: from Cooling Flows to Cool Cores Silvano Molendi (IASF-MI)

2. XMM-Newton and Galaxy Clusters Silvano Molendi (IASF-MI)

3. Introduction This is a rapidly evolving research field. This is a rapidly evolving research field. The new satellites are allowing us to make much progress. You may view this session as a sampler of the science we are now doing. The new satellites are allowing us to make much progress. You may view this session as a sampler of the science we are now doing. Radial characterization of individual systems temperature (Pratt) mass (Pointecouteau), implications for cosmology (Arnaud). Study objects at unconcievable redshifts (Jones, Vauclair) Approach physical phenomena with an unprecedented combination of spectral and spatial capabilities (A. Finoguenov), mergers (J.L Sauvageot, Sakelliou).

4. Conclusions This is a very exciting time to be working on Clusters!

5. From Cooling-Flows to Cool Cores From Cooling-Flows to Cool Cores Silvano Molendi (IASF-MI)

6. From Cooling-Flows to Cool Cores From Cooling-Flows to Cool Cores Silvano Molendi (IASF-MI) Your theory is crazy, but it’s not crazy enough to be true (N.Bohr)

7. Cooling Flows Cooling Flows t cool ≈ T g 1/2 n p -1 For large radii n p is small t cool »t Hubble In the core n p is large Э r cool t cool ~ t Hubble The gas within r cool will cool and flow inwards

8. Key Issue This has been explained in the context of multi-phase models (Nulsen 1986) Different phases T,ρ coexist at every r Multi-phase models require gas with T down to 0.1 keV The surface brightness is not as peaked as would be expected if all the cooling gas were to reach the center M≠const  M  r (Fabian, Nulsen & Canizares 1984) Most of the gas drops out the flow before reaching the center..

9. The (XMM)-Newtonian Revolution

10. A1795 Tamura et al. (2001a); A1835 Peterson et al. (2001); AS1101 Kaastra et al. (2001); A496 Tamura et al. (2001b); sample of 14 objects Peterson et al. (2003) There is a remarkable lack of emission lines expected from gas with temperatures smaller than 1-2 keV. The most straightforward interpretation is that there is no gas with temperatures smaller than 1-2 keV. Peterson et al. (2001) Standard CF model predicts gas with T down to at least 0.1 keV! The RGS Result

11. A1795 Tamura et al. (2001a); A1835 Peterson et al. (2001); AS1101 Kaastra et al. (2001); A496 Tamura et al. (2001b); sample of 14 objects Peterson et al. (2003) There is a remarkable lack of emission lines expected from gas with temperatures smaller than 1-3 keV. The most straightforward interpretation is that there is no gas with temperatures smaller than 1-3 keV. Standard CF model predicts gas with T down to at least 0.1 keV! The RGS Result

12. EPIC has a spectral resolution ~ 10 times worse than RGS. It cannot resolve individual lines. However it can discriminate between models with and without a minimum temperature The major discriminant is the Fe L Shell blend profile The EPIC Result

13. Spectra above ~1.3 keV are similar. Below we observe a prominent line-like feature: Fe-L shell line complex. In the spectrum with T min =0.1 keV we see a shoulder down to ~ 0.8, this is due to low ionization lines from gas colder than 0.9 keV. In the spectrum with T min =0.9 keV the shoulder is absent because the low ionization lines are missing Molendi & Pizzolato (2001) T min =0.9 keV T min =0.1 keV Model spectra degraded to the EPIC resolution Comparison between multi-temperature models

14. EPIC minimum temperatures are in good agreement with RGS minimum temperatures. The result on T min is a solid one! All cluster cores observed so far show a T min Values range between ~1 and ~3 keV Minimum Temperature

15. Spatially resolved spectroscopy of Cluster cores with EPIC Molendi (2002) M87 Temperature map 1. 1.In most of the core the gas is single temperature 2. 2.The only regions where we find evidence of more than 1 temperature are the SW and E radio arms which are cospatial with the radio emission 3. 3.No evidence of gas cooler than 1 keV

16. Gas is NOT multiphase, at least not in the sense required by the standard multi-phase CF modelGas is NOT multiphase, at least not in the sense required by.the standard multi-phase CF model Multiphaseness is or was a fundamental ingredient of the CF model, without it the model falls!Multiphaseness is or was a fundamental ingredient of the CF.model, without it the model falls! Implications for Cooling-Flow models Little evidence of gas cooler than 1-3 keVLittle evidence of gas cooler than 1-3 keV anywhere anywhere If gas does not cool below 1-3 keV it will not beIf gas does not cool below 1-3 keV it will not be deposited as cold gas deposited as cold gas Mass deposition, if there is any, must be much smaller thanMass deposition, if there is any, must be much smaller than previously thought previously thought Multiphaseness Mass deposition

17. Implications for Cooling-Flow models The name itself is missleading as it describes a phemoneon of little or no impact Cooling Flow Cool core

18. Now that we have brought the house down it is time to think about rebuilding!

19. Cool Cores What happens to the gas which should be cooling on very short timescales? Two classes of solutions have been proposed: The cooler gas is there but it is somehow hidden (Fabian et al. 2001) The gas is prevented from cooling below a certain temperature by some form of heating. Heating must be widespread as we do not observe accumulation of gas at a particular radius or temperature. Various mechanisms have been considered: thermal conduction (Narayan & Medvedev 2001, Fabian et al. 2002) Heating from the central AGN (e.g. Begelman 2002, Churazov et al. 2002) ✘

20. Heating Mechanisms: Conduction Determine the conduction coef. necessary to balance cooling and compare it to the Spitzer coefficent (Voigt et al. 2003, Ghizzardi et al. 2003)Determine the conduction coef. necessary to balance cooling and compare it to the Spitzer coefficent (Voigt et al. 2003, Ghizzardi et al. 2003) Heating from conduction is insufficent within the very core.Heating from conduction is insufficent within the very core. Extra heating is required to balance coolingExtra heating is required to balance cooling

21. Heating from the AGN Chandra finds what appear to be holes “cavities”. Radio lobes are conicident with X-ray cavities Radio lobes inflated by jets appear to be making their way pushing aside the X-ray emitting plasma Hydra A McNamara et al. (2001)

22. Heating from the AGN Abell 2052 Blanton et al. (2001) Radio lobes fill X-ray cavities Cavities are surrounded by denser & cooler gas. If the lobes are responsible for heating the flow why are they surrounded by cool gas? If the lobes are responsible for heating the flow why are they surrounded by cool gas?

23. Heating from the AGN Fabian et al. (2002) The total energy required to quench a flow can be consider- able. Take total cooling energy, determined from L(< r cool )t Hubble for a set of clusters and compare it with the total energy emitted by an AGN over t Hubble. The more luminous cores imply very large black-hole masses

24. From outside: The gas outside r cool is a huge heat reservoir, look for meachansim that tap this source (thermal conduction). From the AGN: 1)Interaction with Radio structures is localized 2)No evidence of heating at the site of the interaction (quite the contrary) 3)Heating could be episodic through outbursts of AGN activity, however we have various indicators that point to a gentle and non sporadic form of heating (e.g. Mathews & Brighenti 2003). 4)The overall energy available from the AGN may not be sufficent for the most massive systems. Do we have a credible mechanism?

25. Probably not Do we have a credible mechanism? The hunt is still on!

26. We need a form of widespread gentle heating. Something connected with subsonic gas motions would be nice. We do have evidence of widespread gas motions in the core of Perseus through the lack of Resonant Scattering (Gastaldello & Molendi 2003, Churazov et al. 2003) and detection of pressure waves (Fabian et al. 2003). Looking for something better

27. Summary Clusters are extremely interesting astrophys. objects. Amongst the most demanding from an instrumental point of view, it’s no wonder that innovative new satellites like Chandra and XMM-Newton are providing us with great new results Cooling Flows as we understood them in pre XMM-Newton days are dead! Currently we do not have a solid understanding of what keeps the gas from cooling, the answer may come in a week in a year or maybe 10 years from now