Bremsstrahlung from CLUSTERS OF GALAXIES Clusters of Galaxies

Bremsstrahlung from CLUSTERS OF GALAXIES

Clusters of Galaxies: a short overview

Clusters of Galaxies X-ray Band Galaxies Gas Dark. Matter 1000 x 1010 Mo 1014 Mo 1015 Mo

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

Structure Formation

Structure Formation 1000 galaxies within 1 Mpc

Cluster Gas Density

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

Status of The IGM Age of Clusters ~ few Gyr; R ~ 1 -2 Mpc T ~ 1 -10 ke. V; 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

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

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

Emission Processes of Clusters of Galaxies in the X-ray Band Beside IGM contains some metals (0. 3 Solar) They produce line emission

X-ray Observations • Gas density • Gas Temperature • Gas chemical composition • If assume hydrostatic equilibrium Cluster Mass

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

Cooling in Clusters LX ngas 2 Tg 1/2 Volume E ngas. KTg Volume tcool E/LX Tg 1/2 n-1

Cooling Flows tcool ≈ Tg 1/2 np-1 n For large radii np is small n In the core np is large tcool » t. Hubble tcool ~ t. Hubble The gas within rcool will cool

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

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

X-ray Observatories After the rocket experiments during the 1960 s, the first X-ray Earth-orbiting explorers were launched in the 1970 s: Uhuru, SAS 3, Ariel 5 n followed in late 1970 s early 1980 s by larger missions: HEAO-1, Einstein, EXOSAT, and Ginga. n

X-ray Observatories n n n In the 1990 s 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

Current X-Ray Missions Chandra XMM-Newton

The X-ray Telescope Chandra

Chandra detectors

PSF

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 = 2 d 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

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

The RGS Result A 1795 Tamura et al. (2001 a); A 1835 Peterson et al. (2001); AS 1101 Kaastra et al. (2001); A 496 Tamura et al. (2001 b); sample of 14 objects Peterson et al. (2003) There is a remarkable lack of emission lines expected from gas cooling below 1 -2 ke. V. Peterson et al. (2001) The most straightforward interpretation is that gas is cooling down to 2 -3 ke. V but not further. Standard CF model predicts gas with T down to at least 0. 1 ke. V!

AGN in the central galaxy

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

Interaction between radio sources and X-ray gas Chandra Observation of A 2052; Blanton et al. 2001 Ap. J, 558, L 15 Hydra A; Mc. Namara et al 2000; David et al. 2001 Perseus; Fabian et al. 2000 Virgo; Young et al. 2002

Chandra Observations of Clusters A 133 Fujita et al. 2002 1 E 0657 Markevitch et al 2001 A 1795 Fabian et al 2001

Chandra OBSERVATION OF 2 A 0335 P. Mazzotta. , A. Edge, Markevitch 2002, submitted

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

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

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.

The Chandra View Abell 2597, Mc. Namara et al. (2001) 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 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.

Density Cluster Merger Entropy

1 E 0657 Markevitch et al 2001.