Intro

Illustris is a huge suite of simulations with the moving mesh code, AREPO. Illustris applies the FoF and Subfind algorithms to identify halos/subhalos and store particles accordingly. Therefore, we can easily load a subset of particles belonging to the same halo/subhalo. This method works for most cases but still fails when

1. two halos largely overlap,

2. there are too many “fuzz” particles which don’t belong to any halo,

3. we want to trace the evolution of a particle, but it “jumps” to another halo at some time, etc.

Therefore, we develope the mesh_illustris toolkit to enable loading Illustris like mesh-based simulations. mesh_illustris splits the entire volume into a 3D mesh and index each particle/cell according to its location in the mesh. This method allows us to quickly load a subset (e.g., a box or sphere) of particles/cells with minimal amount of memory.