Mon.Not.Roy.Astron.Soc. 330 (2002) L48 It has become increasingly apparent that traditional hydrodynamical
simulations of galaxy clusters are unable to reproduce the observed properties
of galaxy ...clusters, in particular overpredicting the mass corresponding to a
given cluster temperature. Such overestimation may lead to systematic errors in
results using galaxy clusters as cosmological probes, such as constraints on
the density perturbation normalization sigma_8. In this paper we demonstrate
that inclusion of additional gas physics, namely radiative cooling and a
possible preheating of gas prior to cluster formation, is able to bring the
temperature-mass relation in the innermost parts of clusters into good
agreement with recent determinations by Allen, Schmidt & Fabian using Chandra
data.
The amplitude of density perturbations, for the currently-favoured LambdaCDM cosmology, is constrained using the observed properties of galaxy clusters. The catalogue used is that of Ikebe et al. ...(2002). The cluster temperature to mass relation is obtained via N-body/hydrodynamical simulations including radiative cooling and preheating of cluster gas, which we have previously shown to reproduce well the observed temperature--mass relation in the innermost parts of clusters (Thomas et al. 2002). We generate and compare mock catalogues via a Monte Carlo method, which allows us to constrain the relation between X-ray temperature and luminosity, including its scatter, simultaneously with cosmological parameters. We find a luminosity-temperature relation in good agreement with the results of Ikebe et al. (2002), while for the matter power spectrum normalization, we find \(\sigma_8 = 0.78_{-0.06}^{+0.30}\) at 95 per cent confidence for \(\Omega_0 = 0.35\). Scaling to WMAP's central value of \(\Omega_0 = 0.27\) would give a best-fit value of \(\sigma_8 \simeq 0.9\).
We calculate X-ray properties of present-day galaxy clusters from hydrodynamical cosmological simulations of the LCDM cosmology and compare these with recent X-ray observations. Results from three ...simulations are presented, each of which uses the same initial conditions: a standard adiabatic, Non-radiative model, a Radiative model that includes radiative cooling of the gas, and a Preheating model that also includes cooling but in addition impulsively heats the gas prior to cluster formation. At the end of the simulations, the global cooled baryon fractions in the latter two runs are 15 per cent and 0.4 per cent respectively which bracket the recent result from the K-band luminosity function. We construct cluster catalogues which consist of over 500 clusters and are complete in mass down to 1.18*10^{13} Msun/h. While clusters in the Non-radiative model behave in accord with the self-similar picture, those of the other two models reproduce key aspects of the observed X-ray properties: the core entropy, temperature-mass and luminosity-temperature relations are all in good agreement with recent observations. This agreement stems primarily from an increase in entropy with respect to the Non-radiative clusters. Although the physics affecting the intra-cluster medium is very different in the two models, the resulting cluster entropy profiles are very similar.
It has become increasingly apparent that traditional hydrodynamical simulations of galaxy clusters are unable to reproduce the observed properties of galaxy clusters, in particular overpredicting the ...mass corresponding to a given cluster temperature. Such overestimation may lead to systematic errors in results using galaxy clusters as cosmological probes, such as constraints on the density perturbation normalization sigma_8. In this paper we demonstrate that inclusion of additional gas physics, namely radiative cooling and a possible preheating of gas prior to cluster formation, is able to bring the temperature-mass relation in the innermost parts of clusters into good agreement with recent determinations by Allen, Schmidt & Fabian using Chandra data.
