  We present the analysis of a suite of simulations of a Virgo mass galaxy
cluster. Undertaken within the framework of standard cold dark matter
cosmology, these simulations were performed at differing resolutions and with
increasingly complex physical processes, with the goal of identifying the
effects of each on the evolution of the cluster. We focus on the cluster at the
present epoch and examine properties including the radial distributions of
density, temperature, entropy and velocity. We also map `observable' projected
properties such as the surface mass density, X-ray surface brightness and SZ
signature. We identify significant differences between the simulations, which
highlights the need for caution when comparing numerical simulations to
observations of galaxy clusters. While resolution affects the inner density
profile in dark matter simulations, the addition of a gaseous component,
especially one that cools and forms stars, affects the entire cluster. We
conclude that both resolution and included physical processes play an important
role in simulating the formation and evolution of galaxy clusters. Therefore,
physical inferences drawn from simulations that do not include a gaseous
component that can cool and form stars present a poor representation of
reality. (Abridged)

Astrophysics