Resolution dependence of cold CGM gas in SPH simulations

Determine whether increasing the resolution of Smoothed-Particle Hydrodynamics simulations produces the same changes in the amount of cold circumgalactic gas as increased resolution in grid-based and moving-mesh simulations.

Background

The study relies on a high-resolution cosmological simulation using Smoothed-Particle Hydrodynamics (SPH). Previous work with grid-based and moving-mesh simulations indicates that insufficient resolution can underestimate the amount of cold gas in the CGM, partly because small-scale structures and precipitation in filaments are unresolved.

The authors note that no comparable study has yet tested resolution convergence for the CGM in SPH simulations. Because SPH codes differ from grid-based and moving-mesh methods in their adaptive spatial resolution and treatment of fluid mixing, it is unresolved whether increasing resolution produces the same cold-gas behavior. This uncertainty directly affects the interpretation of the simulated environmental dependence of CGM covering fractions.

References

Currently, no work exists that examines the influence of increased resolution on the CGM using SPH similar to what has been done for grid based and moving mesh codes. Therefore, while we expect that SPH codes will show a similar behavior concerning the amount of cold gas in the CGM when increasing the resolution, it is not clear whether this is indeed the case.

— The environmental dependence of the circumgalactic medium in a high-resolution cosmological simulation  (2609.08654 - Herzog et al., 8 Sep 2026) in Section 3.2, Caveats, subsection “Resolution”