Non-Radiative Test of a New SPH Scheme

We adapt new schemes of gravitational N-body dynamics and smoothed particle hydrodynamics (SPH) to the tree N-body/SPH galactic chemodynamics code GCD+. The applied new schemes include the adaptive softening suggested by Price & Monaghan (2007), to improve the self-gravity calculation, and artificial viscosity and thermal conductivity suggested by Rosswog & Price (2007) and Price (2008), to model discontinuities and Kelvin-Helmholtz instabilities more accurately. We first present non-radiative test simulations and contrast the results with those obtained with conventional hydrodynamical schemes. The new schemes lead to a significant improvement in the ability of TreeSPH codes, such as GCD+, to capture strong shocks and model Kelvin-Helmholtz instabilities. In light of the well-known discrepancy between entropy profiles predicted by SPH codes and those from adaptive mesh refinement (AMR) codes, we next explore the impact of these new hydrodynamical schemes upon cosmological simulations of galaxy cluster formation. We demonstrate that our new version of GCD+ leads to higher entropy in the cluster centre, with an associated entropy profile consistent with that obtained with AMR codes. We suggest that the newly-applied SPH scheme may ameliorate this classical discrepancy between SPH and AMR codes.