Is WMAP3 normalization compatible with the X-Ray cluster abundance?

TL;DR

This study compares cosmological simulations with WMAP3 parameters to observed galaxy cluster X-ray temperatures, finding a significant discrepancy in normalization that challenges current models.

Contribution

It provides the first detailed comparison of WMAP3-based cosmological simulations with observed cluster X-ray temperature functions, highlighting a major normalization inconsistency.

Findings

WMAP3 normalization is barely compatible with observed cluster abundances

Simulations require a mass-temperature relation normalization 2.5-3 times lower

Discrepancy cannot be explained by star formation or cooling effects

Abstract

We present the mass and X-ray temperature functions derived from a sample of more than 15,000 galaxy clusters of the MareNostrum Universe cosmological SPH simulations. In these simulations, we follow structure formation in a cubic volume of 500/h Mpc on a side assuming cosmological parameters consistent with either the first or third year WMAP data and gaussian initial conditions. We compare our numerical predictions with the most recent observational estimates of the cluster X-ray temperature functions and find that the low normalization cosmological model inferred from the 3 year WMAP data results is barely compatible with the present epoch X-ray cluster abundances. We can only reconcile the simulations with the observational data if we assume a normalization of the Mass-Temperature relation which is a factor of 2.5--3 smaller than our non-radiative simulations predict. This deviation seems to be too large to be accounted by the effects of star formation or cooling in the ICM, not taken into account in these simulations.