We present results of N-body/gasdynamical simulations designed to investigate the evolution of X-ray clusters in a flat , low-density , \Lambda -dominated cold dark matter ( CDM ) cosmogony .
The simulations include self-gravity , pressure gradients and hydrodynamical shocks , but neglect radiative cooling .
The density profile of the dark matter component can be fitted accurately by the simple formula originally proposed by Navarro , Frenk & White to describe the structure of clusters in a CDM universe with \Omega = 1 .
In projection , the shape of the dark matter radial density profile and the corresponding line-of-sight velocity dispersion profile are in very good agreement with the observed profiles for galaxies in the CNOC sample of clusters .
This suggests that galaxies are not strongly segregated relative to the dark matter in X-ray luminous clusters .
The gas in our simulated clusters is less centrally concentrated than the dark matter , and its radial density profile is well described by the familiar \beta -model .
As a result , the average baryon fraction within the virial radius ( r _ { vir } ) is only 85 - 90 \% of the universal value and is lower nearer the center .
The total mass and velocity dispersion of our clusters can be accurately inferred ( with \sim 15 \% uncertainty ) from their X-ray emission-weighted temperature .
We generalize Kaiser ’ s scalefree scaling relations to arbitrary power spectra and low-density universes and show that simulated clusters generally follow these relations .
The agreement between the simulations and the analytical results provides a convincing demonstration of the soundness of our gasdynamical numerical techniques .
Although our simulated clusters resemble observed clusters in several respects , the slope of the luminosity-temperature relation implied by the scaling relations , and obeyed by the simulations , is in disagreement with observations .
This suggests that non-gravitational effects such as preheating or cooling must have played an important role in determining the properties of the observed X-ray emission from galaxy clusters .