A close look at M87

1. A close look at M87 Silvano Molendi & Simona Ghizzardi Molendi (2002), Ghizzardi et al. subm.

2. Introduction The temperature structure of M87 using data from Chandra, XMM-Newton and BeppoSAX: • Multi-phase gas • Cool Component • Radio Emission • Heating Models

3. Why M87 1 arcmin ~ 5 kpc: we can resolve very small structures Statistics is very good: we can divide the source in many small regions and perform a detailed study of the temperature structure One of the few objects that we can study in such detail

4. Temperature Structure Devided the Chandra and XMM-Newton FOV in ~100 regions for which we have performed spectral fits. In most regions a 1 T model describes the data adequately. In a few regions 2 temperature models provide a much better description of the data. F-test performed to see where 2T fits do better than 1T fits Results expressed in terms of an F-probability map

5. Temperature Structure F probability map from EPIC

6. Multi-phase Gas? For 2T regions 3T and 2T + CF models do not provide better fits. Detailed analysis of selected regions shows that: a third T component can contribute significantly (EI3T > 20% EIcool) only if its temperature differs by less than ~ 20% from Tcool. Emission from gas cooler than about 0.6 keV has an associted norm that is no more than a few % of EIcool

7. EI, and KT for hot and cool components from spectral fits ncool/nhot ~ ( EIcool Vhot / EIhot Vcool)1/2 from pressure equilibrium between hot and cool components: nhot kThot = ncool kTcool Vcool/Vhot ~ EIcool/ EIhot (KTcool / KThot)2 Values range between 10-3 and 10-2 More precise calculations based on actual deprojection of the data are in agreement within a factor of 2 Size of individual structures << size of regions for which spectra have been accumulated The cool component

8. Going to smaller scales Derive an EIcool / EIhot ratio map Soft band image, S, sensitive to cool component, hard band image, H ,to hot component Assuming fixed temperatures for Hot and Cool components EIcool / EIhot = f(S,H) Done both with XMM EPIC and Chandra ACIS-S data

9. Cool component and Radio emission EPIC 10’’ x 10’’ Owen et al. (2000)

10. EIcool/EIhot maps EPIC 10’’ x 10’’ ACIS-S 4’’ x 4’’ • EIcool/EIhot almost everywhere smaller than 0.4 • Vcool/Vhot smaller than ~ 0.2

11. Conduction • Cool blobs are not resolved by EPIC or ACIS • Typical size must be smaller than ~ 300 pc • Timescale for conduction to operate is a few 105 years Conduction must be heavily suppressed!

12. Conduction • Suppression in cold fronts operates across a discontinuity surface here the cool blobs are embedded in the hotter component • For many years it has been recognized that conduction might be suppressed and magnetic fields have been invoked as a possible means to achieve suppression • We find evidence of suppression only in those region where we see radio structure

13. The Radio Arms EIhot and nhot, inside and outside radio arms are very similar Filling factor of the radio plasma must be small. ACIS and EPIC H band images (cool component is very small) do not show evidence of cavities Size of individual radio structures is small

14. The Radio Arms If we assume equipartion between B field and particles and Pradio = Phot we estimate a filling factor for radio plasma of the order of 1% Radio emission is likely originating from small structures with filling factors similar to those of the cool X-ray emitting blobs

15. Models • Radio bubbles rise subsonically in cluster atmosphere, as the bubbles rise, they capture ambient gas, dragging it upwards. During the upward motion the gas is expected to cool adiabatically (Churazov et al. 2001) • Two observational tests: • The blobs should become colder as they rise • The entropy of the blobs should be similar to that of the ambient gas at the center

16. Models • Temperature of cool component does not vary with radius • Entropy of cool component is almost everywhere smaller than entropy of hot component

17. Models • Temperature problem is probably not too severe (Kaiser 2003) • Entropy problem is tougher. The blobs must have originated at radii smaller than ~ 20’’, however the amount of gas found at such small radii is only a fraction of the amount of gas in the cool blobs (4x109 Msol). • Implies that the density profile in the innermost 2 ~ 3 kpc has changed substantially over a few 107 years. • Soker et al. (2002) find similar results for A2052.

18. Heating Mechanisms Conduction • Performed analysis as in Voigt et al. (2002) • As for A2199 insufficent within the very core. • Extra heating is required to balance cooling

19. Heating Mechanisms AGN • Use prescription for heating term, H, provided by Ruszkowsky and Begelman (2002) and parameters: L Luminosity of the central source; ro scale radius where bubbles start rising buoyantly. • Efficency of thermal conduction fixed at 1/3 of Spitzer value

20. Heating Mechanisms We find an adequate fit for L=6x1042 erg/s, ro=4.4 kpc. Radius is comparable to the extension of the jet Total jet luminosity 3.7x1042erg/s (1% of total jet power; Owen et al. 2000) AGN conduction

21. Summary • 1T most regions, 2nd cooler comoponent cospatial with radio arms • Cool component has small filling factor and is organized in small structutres • Conduction between hot and cool component is suppressed • Radio emisson has small filling factor and is organized in small structures • Origin of the cool blobs is uncertain • Conduction is insufficent to balance cooling • Mixed heating model (AGN + Conduction) works.