1. Bremsstrahlung from CLUSTERS OF GALAXIES

2. Clusters of Galaxies: a short overview

3. Clusters of Galaxies X-ray Band Galaxies Gas DarkMatter 1000x10 10 M o 10 14 M o 10 15 M o

4. X-Ray Imaging X-rays and optical light show us a different picture

5. X-Ray Imaging X-rays and optical light show us a different picture

6. Structure Formation

7. 1000 galaxies within 1Mpc

8. Cluster Gas Density

9. Observables Relations T-M Virial Equilibrium Kinetic Energy for the gas Thermodynamic T-M relation

10. Status of The IGM Age of Clusters ~ few Gyr; R ~ 1-2 Mpc T ~ 1-10 keV; Gas highly ionized Electrons free mean path Gas may be treated as a fluid Timescale for Coulomb Collisions Electrons are in kinetic equilibrium Maxwellian velocity distribution Timescale for soundwave propagation Gas is in hydrostatic equilibrium

11. Intracluster Medium Hydrostatic equilibrium (spherical symmetry) We can measure the Cluster mass Dynamical Properties of the Galaxies Isothermal Cluster King profile Beta Profile

12. Emission Processes of Clusters of Galaxies in the X-ray Band The IGM is a PlasmaThe IGM is a Plasma Electrons are accelerated by the ionsElectrons are accelerated by the ions They emit for BremsstrahlungThey emit for Bremsstrahlung Electrons are in kinetic equilibrium (Maxwellian V distr. ) Cluster emission is mainly thermal Bremsstrahlung

13. Emission Processes of Clusters of Galaxies in the X-ray Band Beside IGM contains some metals (0.3 Solar) They produce line emission

14. X-ray Observations Gas densityGas density Gas TemperatureGas Temperature Gas chemical compositionGas chemical composition If assume hydrostatic equilibriumIf assume hydrostatic equilibrium Cluster Mass

15. Cooling Flows Observational evidences Observational evidences The homogeneous model: one ρ and T at each radius Observational evidence against homogeneous gas Observational evidence against homogeneous gas The inhomogeneous model: Δρ and ΔT at each radius The role of the magnetic fields in Cooling Flows The role of the magnetic fields in Cooling Flows Estimates of dM/dt from imaging & spectral data The fate of the cooling gas The fate of the cooling gas

16. Cooling in Clusters L X  n gas 2 T g 1/2 Volume E  n gas KT g Volume t cool  E/L X  T g 1/2 n -1

17. 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 t cool ~ t Hubble The gas within r cool will cool

18. Cooling Flows When the gas cools The pressure becomes lower The gas flows inwards, The gas flows inwards, The density increases in the center The gas cools even faster

19. Observational Evidences for Cooling Flows X-Ray Imaging X-Ray Imaging Surface brightness strongly peaked at the center Surface brightness strongly peaked at the center

20. X-ray Observatories After the rocket experiments during the 1960s, the first X-ray Earth-orbiting explorers were launched in the 1970s: Uhuru, SAS 3, Ariel5 followed in late 1970s early 1980s by larger missions: HEAO-1, Einstein, EXOSAT, and Ginga.

21. X-ray Observatories In the 1990s the ROSAT survey detected more than 100,000 X-ray objects the ASCA mission made the first sensitive measurements of the X-ray spectra from these objects BEPPOSAX contributed along this line

22. Current X-Ray Missions XMM-Newton Chandra

23. The X-ray Telescope Chandra

24. Chandra detectors

25. PSF

26. DISPERSIVE SPECTROMETERS DISPERSIVE SPECTROMETERS All convert into dispersion angle and hence into focal plane position in an X-ray imaging detector BRAGG CRYSTAL SECTROMETERS (EINSTEIN, SPECTRUM X-GAMMA): Resolving power up to 2700 but disadvantages of multiplicity of cristals, low throughput, no spatially resolved spectroscopy n x = 2d x sin  TRANSMISSION GRATINGS (EINSTEIN, EXOSAT, CHANDRA) m x = p x sin  where m is the order of diffraction and p the grating period REFLECTION GRATINGS (XMM) m x = p (cos  - cos  ) The resolving power for gratings is given by, assuming a focal lenght f and a position X relative to the optical axis in the focal plane X = f tan   f sin   X = f  so  is constant

27. Previous X-ray telescopes had either good spatial resolution or spectral resolution Rosat Good Spatial resolution Low or no Spectral resolution ASCA Low Spatial resolution Good Spectral resolution Chandra got both Chandra Versus Previous Generation X-ray Satellites

28. ASCA view of “the creation” of Michelangelo Rosat view of “the creation” of Michelangelo Chandra Versus Previous Generation X-ray Satellites An Imaginary Test Chandra view of “the Creation” of Michelangelo

29. The RGS Result 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 cooling below 1-2 keV. The most straightforward interpretation is that gas is cooling down to 2-3 keV but not further. Peterson et al. (2001) Standard CF model predicts gas with T down to at least 0.1 keV!

30. AGN in the central galaxy

31. Chandra X-ray Observatory Hydra A - X-ray X Ray Radio

32. Chandra Observation of A2052; Blanton et al. 2001 ApJ, 558, L15 Interaction between radio sources and X-ray gas Hydra A; McNamara et al 2000; David et al. 2001 Perseus; Fabian et al. 2000 Virgo; Young et al. 2002

33. Chandra Observations of Clusters A 133 Fujita et al. 2002 A 1795 Fabian et al 2001 1E0657 Markevitch et al 2001

34. Chandra OBSERVATION OF 2A0335 P. Mazzotta., A. Edge, Markevitch 2002, submitted

35. The Chandra View Abell 2052 Blanton et al. (2001) Radio lobes fill X-ray cavities Cavities are surrounded by denser & cooler gas

36. The Chandra View Abell 2052 Blanton et al. (2001) Hα emission is observed cospatially with the birght rims of the cavities

37. The Chandra View Centaurus, Sanders et al. (2001), Taylor et al. (2001) Radio X-ray interaction produces an unusual radio source with small bent lobes

38. The Chandra View Perseus, Fabian et al. (2000) Radio lobes fill X-ray cavities. Inner cavities surrounded by denser & cooler gas. Holes appear to be devoid of ICM, Schmidt et al. (2002) If we assume that the radio lobes are in pressure equilibrium with the surrounding ICM, this is reasonable as no shocks are observed, then it is easy to show that the lobes filled with B field and relativistc particles have a smaller specific weight than surrounding ICM and should therefore detach and rise buoyantly.

39. The Chandra View Abell 2597, McNamara et al. (2001) Cavities in Abell 2597 are not coincident with bright radio lobes. Instead, they are associated with faint extended radio emission seen in a deep Very Large Array radio map. Ghost cavities are likely buoyantly rising relics of a radio outburst that occurred between 50 and 100 Myr ago. Expanded view of the central region of Abell 2597 after subtracting a smooth background cluster model. The 8.44 GHz radio contours are superposed VLA 1.4 GHz image of Abell 2597 at 11’’×6’’ resolution

40. Cluster Merger Density Entropy

41. 1E0657 Markevitch et al 2001.