Formation pathway of sub-filaments

Determine whether cosmic sub-filaments form independently and are later incorporated into larger filamentary structures, or instead emerge directly as secondary branches during the assembly of their parent filaments.

Background

The paper introduces sub-filaments as smaller filamentary structures embedded within larger parent filaments, identified using the hierarchical Skeletor reconstruction scheme. Because sub-filaments occupy stronger directional tidal fields and are affected by coherent mass transport along their parent filaments, their formation history may differ from that of isolated filaments.

The authors explicitly identify two unresolved formation scenarios: independent formation followed by incorporation into a parent structure, or direct emergence as secondary branches during parent-filament assembly. Resolving this distinction is necessary for understanding how the observed filamentary hierarchy develops over cosmic time.