Recently, international PhD student Serikbek Sailanbek from the Star Formation and Evolution Group at the Xinjiang Astronomical Observatory, Chinese Academy of Sciences, conducted a study of the star forming region Sh2-252 A-B using ammonia data obtained with the Nanshan 26-m radio telescope and many other data such as CO from PMO 14m telescope. The results of this research were published in the international peer-reviewed journal Research in Astronomy and Astrophysics.

The researchers present a concise summary of the study on the S252A-B star-forming region, which reveals an active hub-filament system (HFS) driven by global hierarchical collapse rather than cloud-cloud collision. Using multi-tracer molecular line observations (CO isotopologues, NH₃) and far-infrared dust continuum data, they examined high-resolution morphological, kinematic, thermal and dynamical properties of S252A-B.

Six distinct filament branchesF-NE (northeast), F-NW (northwest), F-W (west), F-N (north), F-SW (southwest), and F-SE (southeast)converge onto the main S252A-B hub and secondary S252A hub in a spoke-like structure (see Figure 1), showing hierarchical density from diffuse CO envelope to dense NH₃ cores. The filaments are coherent in space and velocity, remain cold at around Tₖᵢₙ ≈ 15–18 K with a “shielded flow” that sustains accretion, and the virial parameter (αᵥᵢᵣ ~ 0.4–0.6) confirms that the central hub is gravitationally bound and collapsing.

Double-peaked spectra are detected only toward the south-western edge of the region with no associated young stellar objects, which rules out cloud-cloud collision as the main trigger of star formation in S252A-B.

This work provides definitive evidence for an active hub-filament system and shows that feedback-driven compression and gravitational focusing work together to channel mass toward active star-forming sites. It also emphasizes the critical importance of high-resolution kinematic observations for distinguishing between different star formation mechanisms, while delivering key insights into interstellar gas dynamics, turbulence, and the physical processes that drive stellar birth.

Figure 1. C¹⁸O (J = 1–0) (left) and NH₃ (1,1) (right) integrated intensity (Moment 0) maps of the S252A-B star-forming region. Green solid curves trace the spines of the identified filamentary branches (labeled F-NE, F-N, F-NW, F-W, F-SW, and F-SE) converging upon the main “Hub” (marked by the large green ellipse). A secondary hub structure near S252A is indicated by the smaller green ellipse. White circles and ellipses label the positions of the H II regions S252A, S252B, S252C, and S252F. The yellow dashed curve traces the boundary of the ionization front from the main Sh2-252 H II region. The small red circle marks the position of water and methanol masers associated with the star-forming core inside the secondary hub structure. In the right panel, the white dashed polygon outlines the boundary of the NH3 mapping area. The filled white circle in the bottom-left corner of each panel represents the effective beam size