Structural and scaling properties of galaxy clustersProbing the physics of structure formation

M.Arnaud, G.Pratt, E.Pointecouteau

(CEA-Sap Saclay)

• Dark matter distribution in clusters with XMM E.Pointecouteau

• Some insights into cluster gas physics with XMM G.Pratt

• Cluster evolution M.Arnaud

• Physical parameters

Lbol ~1041 - a few 1046 ergs/sMtot ~1013 - a few 1015 Mo

T ~ 0.3 - 15 keV

• Present at least since z ~ 1.5

• Morphology: regular (~50%) but some not

≠ dynamical state at all z

The cluster population: A large variety of objects

XMM

A1795 z=0.06 Coma z =0.02

XMM

XMM

RXJ1053 z =1.26

Chandra

RXJ0848 z=1.27

A 2657 T=3.7 keV A2319 T= 9.1 keV

[Mohr & Evrard 1997]

RI

kT

[Neumann & Arnaud 1999]

Sx profile

But all possible clusters do NOT exist

Correlations Some regularity in shape

(anal. spherical collapse; num simul) • ICM: evolving in the gravitational potential of the DM: fgas = cst• Clusters collapsed at z correspond to a fixed density contrast: GM/R3 = < c (z) ; • Are close to virial/hydrostatic equilibrium (between big mergers) kT GM/R • Have same internal DM (and thus gas) structureSelf Similarity of the cluster population expected

Universal profiles Simple scaling laws: Q T

M T3/2

Rv T1/2

LX T2

Z=0Z=0.5Z=1

log

/

c)

Comparison with observations test of formation physics

[NFW 1995]

[Bryan & Norman 1998]

Canonical model of cluster formation

From XMM observations to DM profiles

1 – Imaging surface brightness profile density profile

2 - Spectroscopy temperature profile

Chandra match XMM!

Spherical symmetry +

Hydrostatic Equilibrium

Total mass profile

Mass profile derived from the HE equation

Cusped profile as expected from num. Simu. (NFW profile preferred) Similarity observed in the shape of M(r)

- deprojection- PSF correction

• A1413 [Pratt & Arnaud 02]

z=0.143 ; kTX=6.49 keV

• A1983 [Pratt & Arnaud 03]

z=0.044 ; kTX=2.3 keV

• A478 [Pointecouteau et al. 03]

z=0.088 ; kTX=6.73 keV

- down to 0.01 virial radius- up to 0.7 virial radius

Chandra on 5 relaxed hot/lensing clusters : M T1.52±0. 36

The M-T relation from XMM/chandra

Modelling of DM collapse OK; Pb in gas modelling (distribution shape)

= 2500 (0.3 r200 )

XMM on 3 relaxed cooling flow clusters : M T1.49±0.2 

Normalisation offset at = 2500 (0.3 r200 )… and at all radii ()

At a given R corresponding to a density constrast : M = T3/2

depends on the (universal) gas and DM distribution, via HE

Conclusion

XMM-Newton Unpreecedent accuracy on kT(r) First detailed DM profiles for clusters (up to Rv)

Similarity in the dark matter shape of cluster Dark matter collapse seems to be well understood Better constraints needed to characterize the central region:

NFW preferred ideal world: XMM+Chandra

Departure from predicted M-T relation normalisation Modelling of the gas still not reproducing real clusters

Physics of the gas not well understood (G.Pratt) Evolution of scaling properties with z (M.Arnaud)