Santa Barbara Cluster Comparison Test with DISPH

TL;DR

This study applies the density independent SPH (DISPH) method to galaxy cluster simulations, demonstrating its ability to produce entropy cores and highlighting the limitations of traditional SPH and mesh codes in such simulations.

Contribution

The paper introduces the use of DISPH in galaxy cluster simulations, showing it can accurately handle contact discontinuities and produce more realistic entropy profiles.

Findings

DISPH produces entropy cores in galaxy cluster simulations.

Standard SPH and mesh codes have significant limitations in modeling entropy profiles.

DISPH results are comparable to quasi-Lagrangian schemes like moving mesh.

Abstract

The Santa Barbara cluster comparison project (Frenk et al. Frenk+1999) revealed that there is a systematic difference between entropy profiles of clusters of galaxies obtained by Eulerian mesh and Lagrangian smoothed particle hydrodynamics (SPH) codes: Mesh codes gave a core with a constant entropy whereas SPH codes did not. One possible reason for this difference is that mesh codes are not Galilean invariant. Another possible reason is the problem of the SPH method, which might give too much "protection" to cold clumps because of the unphysical surface tension induced at contact discontinuities. In this paper, we apply the density independent formulation of SPH (DISPH), which can handle contact discontinuities accurately, to simulations of a cluster of galaxies, and compare the results with those with the standard SPH. We obtained the entropy core when we adopt DISPH. The size of the core is, however, significantly smaller than those obtained with mesh simulations, and is comparable to those obtained with quasi-Lagrangian schemes such as "moving mesh" and "mesh free" schemes. We conclude that both the standard SPH without artificial conductivity and Eulerian mesh codes have serious problems even such an idealized simulation, while DISPH, SPH with artificial conductivity, and quasi-Lagrangian schemes have sufficient capability to deal with it.