A Multitracer Analysis of the Sh2-252 A-B Star-forming Region: Hub-filament System

We present a multitracer analysis of the Sh2-252 A-B (S252 A-B) star-forming molecular clump located between H ii regions S252A and S252B, using molecular line observations (CO isotopologues and NH₃) and far-infrared dust continuum data to study star formation mechanisms in S252 A-B. We find evidence for existence of a hub-filament system (HFS) in this area. Our observations reveal six filaments converging upon a main S252A-B and secondary S252A hubs. The region was previously suspected as a site of cloud–cloud collision (CCC). However, the only observed double-peaked spectra are located at the south-western edge of S252 A-B and show no associated young stellar objects (YSOs), suggesting that star formation in the S252 A-B region is not induced by CCC. The filaments have clear association with the YSOs and their clusters. Filaments remain cold (T _kin ≈ 15–18 K) until merging with the hub, demonstrating “shielded flow.” The virial parameter (α _vir ∼ 0.4–0.6) indicates that the hub is gravitationally bound. We conclude that S252 A-B possesses an active HFS and star formation in the region is driven by global hierarchical collapse. Two filaments located at the borders of the large H ii region S252 may be prone to the collect-and-collapse process, highlighting how feedback-driven compression and gravitational focusing work in accord to bring mass to the sites of active star formation.