Primordial mass and density segregation in a young molecular cloud

We analyse the geometry of the Pipe Nebula, drawn by the distribution (Q spatial parameter) and hierarchy (Λ spatial segregation) of column density peaks previously detected and catalogued. By analysing the mass and volume density of the cores, we determine that both variables show spatial segregation with a high degree of substructure. In view of the early evolutionary state of the Pipe Nebula, our results suggest that segregation both by mass and by volume density may be primordial, in the sense of appearing early in the chain of physical processes that lead to cluster formation. We propose that volume density, and not mass, is the parameter that most clearly determines the initial spatial distribution of pre-stellar cores.