The role of the artificial conductivity in SPH simulations of galaxy
  clusters: effects on the ICM properties
  We study the thermal structure of the intra-cluster medium (ICM) in a set of
cosmological hydrodynamical cluster simulations performed with an SPH numerical
scheme employing an artificial conductivity (AC) term. We explore the effects
of this term on the ICM temperature and entropy profiles, thermal distribution,
velocity field and expected X-ray emission. We find that in adiabatic runs the
artificial conductivity favours (i) the formation of an entropy core, raising
and flattening the central entropy profiles, in better agreement with findings
from Eulerian codes; and (ii) a systematic reduction of the cold gas component.
In fact, the cluster large-scale structure and dynamical state are preserved
across different runs, but the improved gas mixing enabled by the AC term
strongly increases the stripping rate of gas from the cold clumps moving
through the ICM. This in turn reduces the production of turbulence generated by
the instabilities which develop because of the interaction between clumps and
ambient ICM. We then find that turbulent motions, enhanced by the
time-dependent artificial viscosity scheme we use, are rather damped by the AC
term. The ICM synthetic X-ray emission substantially mirrors the changes in its
thermo-dynamical structure, stressing the robustness of the AC impact. All
these effects are softened by the introduction of radiative cooling but still
present, especially a partial suppression of cold gas. Therefore, not only the
physics accounted for, but also the numerical approach itself can have an
impact in shaping the ICM thermo-dynamical structure and ultimately in the use
of SPH cluster simulations for cosmological studies.
