Rachida Sadat

The evolution of clusters in the CLEF cosmological simulation: X-ray structural and scaling properties

We present results from a study of the X-ray cluster population that forms within the CLEF cosmological hydrodynamics simulation, a large N-body/SPH simulation of the Lambda cold dark matter cosmology with radiative cooling, star formation and feedback. With nearly 100 (kT > 2 keV) clusters at z = 0 and 60 at z = 1, our sample is one of the largest ever drawn from a single simulation and allows us to study variations within the X-ray cluster population both at low and high redshift. The scaled projected temperature and entropy profiles at z = 0 are in good agreement with recent high-quality observations of cool core clusters, suggesting that the simulation grossly follows the processes that structure the intracluster medium (ICM) in these objects. Cool cores are a ubiquitous phenomenon in the simulation at low and high redshift, regardless of a cluster’s dynamical state. This is at odds with the observations and so suggests there is still a heating mechanism missing from the simulation. The fraction of irregular (major merger) systems, based on an observable measure of substructure within X-ray surface brightness maps, increases with redshift, but always constitutes a minority population within the simulation. Using a simple, observable measure of the concentration of the ICM, which correlates with the apparent mass deposition rate in the cluster core, we find a large dispersion within regular clusters at low redshift, but this diminishes at higher redshift, where strong cooling-flow systems are absent in our simulation. Consequently, our results predict that the normalization and scatter of the luminosity‐temperature relation should decrease with redshift; if such behaviour turns out to be a correct representation of X-ray cluster evolution, it will have significant consequences for the number of clusters found at high redshift in X-ray flux-limited surveys.

The XMM-

The evolution with redshift of the temperature-luminosity relation of X-ray galaxy clusters is a key ingredient to break degeneracies in the interpretation of X-ray clusters redshift number counts. We therefore take advantage of the recent measurements of the temperature-luminosity relation of distant clusters observed with XMM-Newton and Chandra satellites to examine theoretical number counts expected for different available X-rays cluster samples, namely the RDCS, EMSS, SHARC, 160deg^2 and the MACS at redshift greater than 0.3. We derive these counts without any adjustment, using models previously normalized to the local temperature distribution function and to the high-z (z = 0.33) TDF. We find that these models having Omega_M in the range [0.85-1.] predict counts in remarkable agreement with the observed counts in the different samples. We illustrate that this conclusion is weakly sensitive to the various ingredients of the modeling. Therefore number counts provide a robust evidence of an evolving population. A realistic flat low density model (Omega_M = 0.3), normalized to the local abundance of clusters is found to overproduce cluster abundance at high redshift (above z = 0.5) by nearly an order of magnitude. This result is in conflict with the popular concordance model. The conflict could indicate a deviation from the expected scaling of the M-T relation with redshift.

\Omega

We study the gas mass fraction,

project - II. Cosmological implications from the high redshift L – T relation of X-ray clusters

f_{\rm gas},

XMM-Newton\Omega project: III. Gas mass fraction shape in high redshift clusters

behavior in

Data analysis method for XMM-Newton observations of extended sources and application to bright massive clusters of galaxies at z=0.2

XMM-Newton

Cosmological history of stars and metals

\Omega

Clusters of galaxies: new results from the CLEF hydrodynamics simulation

project. The typical

BAX: a dedicated X-rays galaxy clusters database

f_{\rm gas}