The splashback radius of halos from particle dynamics: III. Halo catalogs, merger trees, and host-subhalo relations

Understand

Virtually any investigation involving dark matter halos relies on a definition of their radius, mass, and of whether they are a subhalo.

• The halo boundary is most commonly defined to include a spherical overdensity contrast (such as R200c, Rvir, and R200m), but different thresholds lead to significant differences in radius and mass.
• The splashback radius has recently been suggested as a more physically motivated (and generally larger) halo boundary, adding to the range of definitions.
• It is often difficult to assess the impact of a particular choice because most halo catalogs contain only one or a few definitions and generally only one set of host-subhalo relations.