Collaborators: - Brian McNamara (Waterloo University & Ohio University)

1. X-ray cavities in galaxy clusters Myriam Gitti (UniBO,INAF-OABo) Collaborators: -Brian McNamara(Waterloo University & Ohio University) -Paul Nulsen(Harvard-Smithsonian Center for Astrophysics)  Arcetri, 7 Maggio 2009 

2. Plan of the talk • Introduction • galaxy clusters • X-ray properties of the intracluster medium (ICM) • “cooling flow” (CF) and “cooling flow problem” • X-ray cavities and radio bubbles • AGN/ICM interaction, heating of CF • MS0735: the most powerful AGN outburst • XMM data analysis and results • do (super-)cavities affect the average cluster properties?

3. Introduction

4. Galaxy clusters X-ray visual 100 kpc • 100-1000 galaxies + intracluster medium (ICM) + dark matter (DM) • total mass ~ 1014 - 1015 M • size ~ some Mpc

5. Why do we study galaxy clusters? Millennium Run (Springel et al. 2005)  Galaxy clusters are key objects for cosmological studies • structure formation (standard CDM scenario) • gravitational collapse of the dark matter • baryon specific physics

6. Galaxy Clusters (total mass) ~2% ~13% ~85% dark matter galaxies ICM relativistic particles AGN radio loud thermal plasma magnetic fields Optical emission X-ray emission Radio emission Radio emission

7. Galaxy Clusters (total mass) ~2% ~13% The ICM is a hot, optically thin plasma enriched in heavy elements It emits in X-rays by thermal bemsstrahlung + lines Jbr  Z2 neniT-1/2 e–h/kT galaxies ICM AGN radio loud thermal plasma Radio emission X-ray emission

8. ICMtemperature~ 0.5–15 keV • ICMdensity~ 10-4 -10-2cm-3 • ICMmetallicity~ 0.3 solar • Luminosity ~ 1043-1046 ergs/s Extracting ICM physical info from X-rays • temperature: from the position of the exponential cut-off in the spectrum • density: from the normalization of the spectrum int(ne2 dV) • metallicity: from lines of heavy elements (e.g., Iron K line complex at ~ 6.7 keV)

9. Modern X-ray Observatories X-ray photons collected and focused by grazing incidence telescopes CCD cameras: measurement of position and energy of incoming photon Scheme of the two XMM telescopes equipped with EPIC-MOS and RGS. In the third, all the light is collected by EPIC-pn. • Chandraextremely good spatial resolution (~0.5’’) • XMM-Newtonexceptional collecting area and thus sensitivity, three telescopes, large field of view (30’  30’)

10. ICM density distribution: ICM(r) = ICM,0 [ 1+ (r/rcore)2 ]-3/2 cooling timetcool :characteristic time of energy radiated in X-rays cooling radiusrcool: radius at which tcool= age of the cluster»H0-1  Surface brightness profile: S(r) = S0 [ 1+ (r/rcore)2 ]1/2-3 Within rcool, tcool<H0-1the cooling gas flows inward -with a mass inflow rateM -and is compressed hydrostatic eq. ratio of energy per unit mass in galaxies to that in gas  kT =2  2/3 mH Compression density increases  X-ray emissivityincreases -model CF cluster non-CF cluster CF cluster  non-CF cluster (Cavaliere & Fusco Femiano 1976) Cooling Flow (CF)– standard model

11. CF– observations • short cooling time • high density • low temperature • H filaments • OVI • molecular gas  evidence of cooling

12. CF– observations Lack of very cold gas XMM/RGS does not see emission lines of gas at intermediate T (Fe XVII, OVII) Gas drops toTmin~0.3 Tvir Chandra spectra consistent   M(<Tmin)~(0.1-0.2)MX  CF problem: why, and how, is the cooling of gas below Tvir/3 suppressed?

13. Signature of cooling below 2 keV suppressed - absorption -mixing -inhomogeneous metallicity missing soft LX ~ LUV - central AGN - thermal conduction - subcluster merging - combinations/other... • Heating to balance cooling   M ~0.1MX CF problem - possible solutions

14. X-ray cavities and radio bubbles

15. Perseus A2052 RBS797 3C317 – A2052 Fabian et al. 2000 Blanton et al. 2001 Gitti et al. 2006 AGN / ICM interaction • most CF clusters contain powerful radio sources associated withcD • central ICM shows “holes” often coincident with radio lobes (Chandra) the radio“bubbles”displace the ICM, creating X-ray“cavities”

16. heating  dissipation of cavity enthalpy the kinetic energy created in the wake of the rising cavity is equal to the enthalpy lost by the cavity as it rises

17. Cavity energy direct measure of the total energy of AGN outburst • Study of radiosource properties  ratio is insignificant  age of radio-filled cavities assumpti jet synchrotron power r t = r/v total AGN power (Birzan et al. 2004) the kinetic energy created in the wake of the rising cavity is equal to the enthalpy lost by the cavity as it rises

18. Cavity properties • diameter  20-200 kpc • pV = 1055-1061 erg • ages = 107-108 yr • P = 1041-1046 erg/s trend:feedback (Birzan et al. 2004) quenching of CFs (Rafferty et al. 2006)

19. cooling and accretion onto a central BH Cooling Flow AGN outburst cooling is reestablished cooling is arrested system settles down Self-regulated feedback loop

20. The most powerful AGN outburst Supercavities (~100s kpc) found inMS0735+7421, Hercules A, and Hydra A McNamara & Nulsen ARA&A 2007 AGN injects >1061 erg into the ICM  heating up to cluster-wide scale

21. L T2.6 L-T relation Luminosity function of Galaxies L T2 gravity (Benson et al. 2003) (Markevitch 1998) Problems addressed • substantial contribution to the pre-heating problem ? • common solution to CF problem and galaxy formation ? • what gives support to the cavities ? • do cavities affect the general cluster properties ?

22. MS0735 MS0735+7421: the most powerful AGN outburst as seen by XMM

23. 1‘ = 210 kpc H0 = 70 km/s/Mpc M = 1- = 0.3 z = 0.216LX (2-10keV)~ 4.6 x 1044erg/s Cavities

24. deficit of emission in the Nsector Surface brightness profile N sector undisturbed cluster 60-180 kpc Undisturbed

25. strong excess in the centre when compared to the model Fit with a -model Single -model not a good description of entire profile fit Fit to outer region:  rcore = 195 kpc  = 0.77 Undisturbed

26. r line of sight Obs. spectrum (r) = spectra in shells  deprojection analysis Temperature profile

27. r line of sight Obs. spectrum (r) = spectra in shells  deprojection analysis Density profile

28. d P G M(<r) = -  d r r 2 d lnne d lnT -kTr Mtot(<r) = + Gmp d lnr d lnr Mass profile Eq. hydrostatic equilibrium:  P = -.... assumption of spherical symmetry  Total gravitational mass Mtot(<r) : ne(r) from -model or deprojection

29. kr2 3rT dT Mtot(<r) = Gmp r2+rc2 dr Mass profile: from -model Mass from beta From T(r) & ne(r) Total gravitational mass M(r) assumption of spherical symmetry assumption of hydrostatic eq. if density follows -model: ne(r) = ne,0 [ 1+ (r/rc)2 ]-3/2

30. 1 r2 dP Mtot(<r) = G nemp dr Mass profile: from deprojection From T(r) & ne(r) Total gravitational mass M(r) assumption of spherical symmetry assumption of hydrostatic eq. if density and pressure are measured from deprojection analysis

31. Chandra + VLA (McNamara et al. 2005) cavity N indication of 13 KeV component BUT poor photon statistics does not allow us to claim a detection What fills the cavities? Radio lobes  relativistic electrons Pext  10 Pradio,eq  also hot, dilute thermal plasma?

32. shock front pre-shocked gas shock front post-shocked gas ~ 10% temperature rise expected by shock model Mach number M 1.4 XMM data consistent with T jump across the shock, but not definitive Shock front

33. Discussion MS0735+7421: do (super-)cavities affect the average properties of galaxy clusters?

34. 3 Hz2 3 Mtot(<r) where c,z= Overdensity= 8 G 4 c,z r3 r (kpc) Mtot, (1014 M) fgas, (Mgas/Mtot)  200 2230  650 15.6  8.78 0.11  0.06 virial radius rvirr200 2500 465  160 1.77  0.82 0.16  0.08 Determination of r200 and r2500 we assume Mtot = MDM  fit with NFW profile (Navarro et al. 1996)...............................................to extrapolate M(r)

35. r2500 = 465 kpc T2500 = 5.2 keV MS0735 Scaled temperature profile (=2500) 6 relaxed clusters observed with Chandra T2500 = 5.5 - 16 keV (Allen et al. 2001)

36. MS0735 r2500 = 465 kpc <TX>= 4.7 keV Scaled temperature profile (=2500) • Clusters with supercavities: 3/30 (Rafferty et al. 2006) age ~ 108 yr • Outbursts active most of the time (Dunn et al. 2005)  as NO marked effect is observed, large outbursts are likely occurring ~10% of the time in a signficant fraction of all CF clusters 12 relaxed clusters observed with Chandra <TX> = 1.6 – 8.9 keV (Vikhlinin et al. 2004)

37. MS0735 Scaled metallicity profile (=180) 9 CF clusters observed with BeppoSAX H0 = 50 km/s/Mpc =1, =0 (De Grandi & Molendi 2001)

38. LT2.6 Excess Entropy, “preheating” 1-3 kev/particle (Wu et al. 2000) 1. early star formation ? 2. AGN (early / late) ? LT2gravity (Markevitch 1998) Luminosity vs. Temperature  General L-T effect: Steepening of L-T relation MS0735: Mass within 1 Mpc is being heated at the level of 1/4 keV/particle

39. MS0735 CF and cavities: 1. cool gas lifted by outburst 2. compression in the shells * WARNING! * Bias for flux-limited surveys Luminosity vs. Temperature  Anomalous L-T effect: MS0735 factor ~2 more luminous than expected from its temperature (Markevitch 1998)

40. Rin in depends on cavity radius & shell thickness  25 % for MS0735 Cavity expansion ICM compression in shells L L’ L LX boost by cavities

41. “cavity effect”  25 % * WARNING! * Overestimate fgas Luminosity vs. Temperature

42. MS0735 (Voigt & Fabian 2006) CMB :  b/ m=0.1750.023 MS0735: fgas,2500=0.1650.040 fgas,2500=0.1170.002 Allen et al. 2004 : fgas,2500=0.0910.002 Vikhlinin et al. 2005 : Gas mass fraction r/r2500

43. Conclusions • substantial contribution to the pre-heating problem ? yes,  1/4 - 1/3 keV per particlepossible (feedback) • what gives support to the cavities ? indications for a hot thermal component • do cavities affect the general cluster properties ? not strongly yes,  1/4 - 1/2 keV per particle indication of a hot thermal component T & Z profiles not strongly ; LX&fgas possibly Gitti et al. 2007, ApJ, 660, 1118

44. …in the future… • search for lines at levels of observed star formation rates XMM-RGS observations • calibration of radio synchrotron efficiency (low frequency) radio observations probe the history of feedback and heating • models for the fueling and triggering of AGN outbursts jet formation, dynamics, energetics, content, and radiative efficiency • “microphysics” of feedback process how cavity enthalpy is dissipated? efficiency of heating? where is heat deposited? • determine AGN heating rate and contribution of AGN outbursts to expected cluster scaling relations large, unbiased search for cavities in a flux- or volume-limited sample

46. Further explanations

47. Energetics SMBH Energy Output Milky Way1) 1 M87 100,000 Perseus Cluster 10,000,000 Hydra A Cluster 100,000,000 MS0735+7421 1,000,000,000 1) Milky Way = 1051 erg in 100 Myr

48. data Observation and data preparation • MS0735 observed by XMM-Newton in April 2005 for ~70 ks. • MOS1, MOS2, pn detectors in Full Frame Mode • Data analysis performed with SASv6.5.0 • Exposure time after data cleaning (flares, etc.)  ~ 50 ks • Masked point sources • Vignetting correction with task evigweight (weighted method by Arnaud et al. 2001 ) • Background from blank-sky observations (Lumb et al. 2002)

49. Metallicity Metallicity profile Projected Deprojected

50. CF analysis Parameter 1 isothcomp. (MEKAL) 2 isot comp. (MEKAL+MEKAL) kT (keV) 3.9(+0.1/-0.1) 6.1(+1.3/-0.6) CF (MEKAL+MKCFLOW) M (M/yr) - 0.73 Norm 7.6(+0.5/-1.3) 2.3(+0.4/-0.4) kTlow(keV) - 260(+30/-20) • Normlow 839/785 2/ dof 891/787 1.5(+0.2/-0.1) 839/785 Spectral analysis: Cooling Flow indication for a CF tcool kT / ne  +  Surface Brightness Temperature cooling radius:rcool ~ 80 kpc • in the CF model: existence of a minimum T • the extra emission comp. can be well modelled either as a CF or a second T comp.