S2D2: Small-scale Significant substructure DBSCAN Detection

The spatial and dynamical structure of star-forming regions can help provide insights on stellar formation patterns. amount data from current upcoming surveys calls for robust objective procedures to detect structure, so the results be statistically analysed different compared. We community with a tool able small scale significant above random expectation, in regions, which could imprint process. makes use one point correlation function nearest neighbour statistics determine parameters DBSCAN algorithm. procedure successfully detects substructures heterogeneous fulfilling goals it was designed for, providing very reliable structures. analysis close complete randomness ($Q \in [0.7,0.87]$) shows that, even when some is present recovered, hardly distinguishable spurious detection homogeneous due projection effects. Interpretation should thus done care. For concentrated we main surrounded by smaller ones, corresponding core plus Poisson fluctuations around it. argue that these structures do not correspond compact are looking for. In realistic cases, more hierarchical, multi-scale would needed capture complexity region. have developed implementations our procedure, catalogue NESTs (Nested Elementary STructures) detected four (Taurus, IC 348, Upper Scorpius, Carina), publicly available community. Implementations 3D, up 6D versions including proper movements progress, will provided as future work.