Evolution of clusters

M. ArnaudCEA - service d’astrophysique Saclay

Assuming favored cosmology =0.3 =0.7

The sample

RX J2237 z=0.30kT =3 ±0.5 keV

RX J0256 z=0.36kT =5 ±0.5 keV

RX J1120 z=0.6kT =5.3 ±0.5 keV

• Clusters from SHARC survey [Romer et al 00; Nichol et al 99; Burke et al 03]

• XMM follow up [Sharc/SSC/SOC/EPIC collaboration] in - GT time (P.I J. Bartlett) [Lumb et al 03] 7 clusters 0.45 < z < 0.62 - OT time (P.I MA) 7(6) clusters 0.3 < z < 0.4

==> Work in progress from combined set

Some Images:

[Arnaud et al, A&A, 02][Majerowicz et al, A&A, 03]

What do we expect ?

Abell 3158 z=0.06

XMM

2.6

M p

cRXJ 1120 z=0.6

ROSAT

• ICM: evolving in the gravitational potential of the DM: fgas = cst ; GMV /R kT

• Clusters collapsed at z correspond to a fixed density contrast: GMV /R3 = <DM c (z) ;

Evolution with z via c (z) h2(z)

Scaling laws: Q = A(z)T: Mgas MV h-1(z) T3/2 Rv h-1(z) T1/2 LX h(z) T2

For a given mass: at higher z: clusters are denser, smaller, brighter

The evolution of the Lx -T relation

There is evolution ! A bit larger than expected ? in agreement with Chandra [ Vikhlinin et al, 2002]

For standard DM model: Lx f2gas(T,z) < n2

gas >/<ngas>2 h(z) T2

Could indicate evolving: fgas(T) and/or shape

==> Look at gas density (EM) profiles (normalisation and shape)

• Scaled according to standard evolution:

EMsc = h(z)-3 T-1.38 EM

NB ‘ non standard ’ but cst EM-T slope

• Compared to local profile

• ~ agreement for individual profiles [ taken

into account local dispersion and errors]

• ~ Similar shape• BUT systematic discrepancies...

Most profiles above local curve [stronger effect for

higher z sample]

More evolution ? (as for Lx-T)

Sx EM = ∫ n2gas dl h(z)3 ?

Self -similar evolution of the the gas distribution ?

Prediction: clusters are denser: gas DM c (z) h(z)2 and smaller: Rv h(z)-1

[Arnaud et al, in prep]

Temperature profile

First (~ precise) measurement of temperature distribution at z=0.6

• XMM observation of RXJ 1120 [Arnaud et al A&A, 2002]

Flat kT profile up to 0.5 virial radius (as at z~0)

RXJ 1120

T =5.3 keV z=0.6

CONCLUSIONS

XMM results show:

Clusters do form a self-similar population down to kT~ 2keV and up to high kT and z• Self similarity of form beyond core• Scaling laws with z (and kT)• First evidence that numerical simulation predict the correct shape for the DM distribution up to virial radius

Self-similarity differs from purely gravitational model• Normalisation of the M-T relation ==> (universal) ICM structure not correct• Slopes : EM-T : steeper ; S-T shallower: likely due to overall gas content• Possible stronger evolution of ICM scaling laws

==> modelling of the DM collapse probably OK==> Gas physics still to be better understood Current pre-heating models failure

What is needed:• Larger local samples on wide kT range

==> e.g. M-T relation; c(M) ?; dispersion in ICM scaling laws and origin• Larger distant samples ==> e.g. evolution of both normalisation and slopes