The close connection between spatial stellar distribution and interstellar structures in star forming regions

Spatial distribution of young stellar objects (YSOs) in star forming regions (SFRs) may be used as key tracers of their birth sites and their dynamical evolution. Focusing on early stages of star formation, YSOs spatial distribution is expected to follow the dense distribution of gas, and thus be characterised by a strong and clumpy stellar clustering. We have developed a framework based on DBSCAN algorithm to identify significant overdense spatial stellar substructures at small scales (the NESTs, for Nested Elementary Stellar sTructures). We first apply this methodology to Taurus and identify 20 NESTs mainly distributed along the gaseous filaments, spanning the 5-80kAU size range. We further assess the reliability of our method and applying it to almost 40 star forming regions (SFRs) uncovering more than 250 NESTs. The geometrical and physical properties of the NESTs in quiescent SFRs, such as in Taurus, suggest that these overdense stellar spatial structures may be seen as the discrete modes and pristine signatures of star formation process. % from their natal cloud. As a particular result, obtained in Taurus and more generally in almost 40 SFRs, we identify two trends in the "Number of stars-Size" NEST relation with a threshold around 10-15kAU as a turning point. We suggest that this two trends may be related to different fragmentation regimes of their molecular clump progenitors. To investigate the hypothesis that connects the cloud fragmentation to clumps of stars, we develop a multi-scale analysis based on a graph-theoretic representation of the hierarchical connection between massive dense cores (MDCs) extracted at different spatial resolution and the Class 0/I YSOs. We present preliminary results obtained for NGC~2264 SFR using the five bands Herschel emission maps covering the region. They highlight the connection between massive dense cores (MDCs) hierarchical fragmentation and the formation of local stellar groups, such as the NESTs.