Zusammenfassung
We have simulated the formation of a galaxy cluster in a $Łambda$CDM
universe using twelve different codes modeling only gravity and non-radiative
hydrodynamics (\art, \arepo, \hydra\ and 9 incarnations of GADGET). This range
of codes includes particle based, moving and fixed mesh codes as well as both
Eulerian and Lagrangian fluid schemes. The various GADGET implementations span
traditional and advanced smoothed-particle hydrodynamics (SPH) schemes. The
goal of this comparison is to assess the reliability of cosmological
hydrodynamical 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 $z=0$, global properties such as mass, and radial profiles of
various dynamical and thermodynamical quantities. The underlying gravitational
framework can be aligned very accurately for all the codes allowing a detailed
investigation of the differences that develop due to the various gas physics
implementations employed. As expected, the mesh-based codes ART and AREPO form
extended entropy cores in the gas with rising central gas temperatures. Those
codes employing traditional SPH schemes show falling entropy profiles all the
way into the very centre with correspondingly rising density profiles and
central temperature inversions. We show that methods with modern SPH schemes
that allow entropy mixing span the range between these two extremes and the
latest SPH variants produce gas entropy profiles that are essentially
indistinguishable from those obtained with grid based methods.
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