The Santa Barbara Cluster Comparison Project: A Comparison of Cosmological Hydrodynamics Solutions
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abstract
We have simulated the formation of an X-ray cluster in a cold dark matter
universe using 12 different codes. The codes span the range of numerical
techniques and implementations currently in use, including SPH and grid methods
with fixed, deformable or multilevel meshes. The goal of this comparison is to
assess the reliability of cosmological gas dynamical simulations of clusters in
the simplest astrophysically relevant case, that in which the gas is assumed to
be non-radiative. We compare images of the cluster at different epochs, global
properties such as mass, temperature and X-ray luminosity, and radial profiles
of various dynamical and thermodynamical quantities. On the whole, the
agreement among the various simulations is gratifying although a number of
discrepancies exist. Agreement is best for properties of the dark matter and
worst for the total X-ray luminosity. Even in this case, simulations that
adequately resolve the core radius of the gas distribution predict total X-ray
luminosities that agree to within a factor of two. Other quantities are
reproduced to much higher accuracy. For example, the temperature and gas mass
fraction within the virial radius agree to about 10%, and the ratio of specific
kinetic to thermal energies of the gas agree to about 5%. Various factors
contribute to the spread in calculated cluster properties, including
differences in the internal timing of the simulations. Based on the overall
consistency of results, we discuss a number of general properties of the
cluster we have modelled.
