THE CORES OF TWO GALAXY GROUPS: WHAT ARE THEY TEACHING US ?

1. THE CORES OF TWO GALAXY GROUPS: WHAT ARE THEY TEACHING US ? FABIO GASTALDELLO UNIBO & UC IRVINE D. BUOTE UCI W. MATHEWS UCSC F. BRIGHENTI UNIBO S. ETTORI OABO

2. AWM 4 AWM 4 SIMPLE MODEL (DONAHUE ET AL. 05) OUTLINE COOLING FLOWS AGN FEEDBACK AGN FEEDBACK ? THE CASE OF NGC 5044 MERGERS

3. A.C. FABIAN CENTRAL (< 100 KPC) DENSITIES OF RELAXED CLUSTERS HIGH ENOUGH THAT RADIATIVE COOLING TIMES LESS THAN 1010 YR IN THE ABSENCE OF ANY BALANCING HEAT SOURCE, A COOLING FLOW DEVELOPS COOLING FLOWS VS. AGN FEEDBACK

4. A.C. FABIAN CENTRAL (< 100 KPC) DENSITIES OF RELAXED CLUSTERS HIGH ENOUGH THAT RADIATIVE COOLING TIMES LESS THAN 109 YR IN THE ABSENCE OF ANY BALANCING HEAT SOURCE, A COOLING FLOW DEVELOPS X-RAY OBSERVATIONS BEFORE CHANDRA AND XMM BROADLY CONSISTENTS BUT MASS SINK PROBLEM: INDICATION OF COLD GAS AND STAR FORMATION BUT 10 TO 100 TIMES LOWER THAN INFERRED FROM X-RAYS GALAXY FORMATION: MUCH OF THE GAS IN THE FORMATION OF MASSIVE GALAXIES BEHAVES AS IN A COOLING FLOW (WHITE & FRENK 91). IF WE CANNOT UNDERSTAND WHAT IS GOING ON IN CLUSTER CORES, THEN WHY SHOULD WE BELIEVE MODELS OF GALAXY FORMATION WHICH RELY ON A SIMILAR PROCESS ? COOLING FLOWS VS. AGN FEEDBACK

5. J. BINNEY FOR MORE THAN TWO DECADES THE THEORY OF STEADY STATE COOLING FLOWSHELD UP PROGRESS IN APPRECIATING THE ROLE THAT AGN PLAY IN STRUCTURING GALAXIES. THIS THEORY WAS FINALLY SWEPT AWAY BY DAMNING EVIDENCE FROM CHANDRA AND XMM, BUT ITS INTERNAL CONTRADICTIONS SHOULD HAVE LEFT IT WITHOUT PROPONENTS A DECADE AGO IT HAS LONG BEEN SUGGESTED THAT COOL CORE PHENOMENON IS FUNDAMENTAL FOR THE GALAXY FORMATION PROCESS. I AGREE, BUT I WANT TO PERSUADE YOU THAT COOL CORES DO NOT TELL US HOW GALAXIES FORMED, BUT WHY THEY CEASED FORMING. ALTHOUGH SOME LOOSE ENDS REMAIN, I AM IMPRESSED BY THE WAY IN WHICH DISPARATE STRANDS OF THEORY AND OBSERVATIONS ARE COMING TOGETHER TO FORM A COHERENT PICTURE OF GALAXY FORMATION AND THE SYMBIOSIS OF BHs WITH SPHEROIDS AND COOL CORE CLUSTERS COOLING FLOWS VS. AGN FEEDBACK

6. NO COOLING FLOWS Peterson et al. 03

7. AGN FEEDBACK A2052: Blanton+01,03 Hydra A: McNamara+00 Perseus: Fabian+03,04,05 “I’VE BEEN ESPECIALLY IMPRESSED BY THE CHANDRA X-RAY IMAGES OF GALAXY CLUSTERS. WE SEE HOW GAS IS COOLING DOWN AND HOW THE COOLING IS BEING BALANCED BY TREMENDOUS OUTBURSTS OF JETS AND BUBBLES. THIS IS SOMETHING THAT MOST PEOPLE DIDN’T SUSPECT WAS HAPPENING UNTIL THESE IMAGES REVEALED IT ” Martin Rees

8. AGN FEEDBACK Gas coolsdown and starts flowing in BH swallows matter Gas stops flowing in BH spins up, producing jets BH exhausts fuel; jets stop Jets dissipate, heating gas Tucker, Tananbaum & Fabian 07

9. AGN FEEDBACK “In this scenario there is a clear dichotomy between active and radio quiet clusters: one would expect the cluster population to bifurcate into systems with strong temperature gradients and feedback and those without either” Donahue et al. 2005

10. AWM4 AND AGN FEEDBACK GASTALDELLO ET AL. 2007

11. AWM4 AND AGN FEEDBACK GASTALDELLO ET AL. 2007

12. AWM4 AND AGN FEEDBACK GASTALDELLO ET AL. 2007

13. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS NGC 1275 (Perseus): Conselice+01 NGC 4696 (Centaurus): Crawford+05

14. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS OPTICAL FILAMENTS, INITIALLY THOUGHT TO HAVE THEIR ORIGIN IN THERMAL INSTABILITIES OF THE COOLING FLOW GAS, WERE TOO MUCH LUMINOUS,WITH SMALL SPATIAL EXTENT AND DUSTY (SHORT SPUTTERING TIME, 107 yr AT 1 KeV) A STRAIGHTFORWARD ALTERNATIVE IS THAT THEY WERE ACCRETED FROM ELSEWHERE, FROM A GAS RICH SPIRAL OR DWARF GALAXY (SPARKS+89) OR THEY ARE TRAILS OF SECONDARY GALAXIES PUNCHING THROUGH THE CENTRAL GALAXY MOLECULAR HYDROGEN RESERVOIR (WILMAN+06)

15. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS 2A 0335+096: Donahue+07

16. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS A2204: Wilman+06

17. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS “The small scale features of NGC 1275 support the idea that this galaxy experienced a merger with a galaxy that contained a nonnegligible stellar component but likely with a significant lower mass than NGC 1275 ” NGC1275(Perseus):Conselice+01

18. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS Perseus: Ettori et al. 98

19. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS “IN ORDER TO UNDERSTAND THE ORIGIN OF THIS FILAMENTARY STRUCTURE, WE HAVE INVESTIGATED TH EVOLUTION OF THE HOT ICM GAS PERTURBED BY THE AGN CENTRAL ACTIVITY IN A PERSEUS-LIKE CLUSTER. OUR SIMULATIONS SHOW THAT A FRACTION OF THE 1-2 KeV GAS PRESENT AT THE CENTER OF CLUSTERS IS TRAPPED AND ENTRAINED BY THE RISING BUOYANT BUBBLE TO HIGHER RADIUS WHERE THE AGN HEATING IS LESS EFFICIENT. THE RADIATIVE COOLING MAKES IT COOL IN A FEW TENS OF Myr BELOW 104 K FORMING COLD FILAMENTARY STRUCTURES IN THE WAKE AND IN THE RIM OF THE BUBBLES. THIS SCENARIO EXPLAINS THE Hα AND CO EMISSION WITHOUT CONTRADICTING THE OBSERVED LACK OF 1 KeV GAS.” REVAZ, COMBES & SALOME’ 07 (arXiv:07114051)

20. OPTICAL NEBULAE IN COOL CORES: AGN VS. MERGERS Fabian et al. 2003

21. THE CASE OF NGC 5044 Buote et al. 2002 • NGC 5044 IS A FOSSIL GROUP: ONLY ONE BIG ELLIPTICAL GALAXY SURROUNDED BY DWARFS (MERGER FREE ENVIRONMENT • IT IS NEARBY ~ 39 Mpc

22. THE CASE OF NGC 5044 • EVIDENCE OF FILAMENTRAY STRUCTURE AND X-RAY CAVITIES

23. DUST IN NGC 5044 TEMI, BRIGHENTI & MATHEWS 2007

24. NGC 5044

25. NGC 5044 BLACK : X-ray FILAMENT box #1 RED: X-ray FILAMENT box #3

26. CONCLUSIONS AGN FEEDBACK HAS ALL THE FEATURES OF THE RIGHT SOLUTION BUT WE ARE NOT CLOSE TO A CLEAR UNDERSTANDING AGN FEEDBACK IN GROUPS IS STILL POORLY INVESTIGATED AND THERE ARE SOME PUZZLES, LIKE AWM 4. THE FEEDBACK LOOP IS LIKELY DISTURBED BY MERGERS. THEY CAN BOTH CONTRIBUTE TO THE PHENOMENA IN CLUSTER CORES IN NGC 5044 WE HAVE EVIDENCE OF THE IMPORTANCE OF DUST IN COOLING THE X-RAY GAS (AND MAYBE BEING RESPONSIBLE OF THE PRODUCTION OF Hα)