2025A&A...701A.155M

Aims. G53 is an active star formation region with approximately 300 young stellar object (YSO) candidates and exhibits a long filament in CO (V_LSR ∼ 23 km s^–1). To date, there has been no detailed study of its filament characteristics. We therefore explored the kinematics of the filament in the G53 region and the star formation activities triggered along it by combining data from various facilities.
Methods. We primarily utilized archival ¹³CO (1-0) data from the Galactic Ring Survey and NH₃(1,1) observations from the Nanshan 26-meter radio telescope. Additionally, we incorporated ¹²CO (3-2) data from the CO High-Resolution Survey, as well as infrared data from Spitzer and Herschel, to study the G53 region. NH₃ (1,1) was used to trace the ends of the molecular cloud G53 (G53W and G53E), while ¹³CO (1-0) was used to map the entire molecular cloud. We used CRISPY to identify the filament spine in the ¹³CO (1-0) position-position-velocity cube. Position-velocity diagrams along the filament spine were analyzed to extract kinematic information. Numerical simulations of a turbulent filament were conducted for comparison with the observed kinematics of G53. Additionally, YSOs in G53 were collected to evaluate the star formation activity.
Results. The velocity-integrated intensity map of ¹³CO (1-0) and the H₂ column density map indicate that the filament G53 appears to be undergoing an end-dominated collapse (EDC) process. Position-velocity diagrams of ¹³CO (1-0) show that in G53W, the clumps C2 and C4 are possibly moving toward each other while accreting surrounding material. Our numerical simulations of the EDC scenario indicate that an isothermal filament initially fragments into several clumps due to turbulence, which subsequently merge at the ends. This further adds to the credibility of our hypothesis regarding the approaching motion of C2 and C4 in G53W. NH₃ signals are detected only in the G53W and G53E regions, with significantly stronger signals in G53W. In G53W, the NH₃(14) data reveal a hub-filament system (HFS) centered around C2. The analysis of NH₃(1,1) shows a strong correlation between the magnitude of the velocity gradient and the velocity dispersion in the G53W region, suggesting that the accumulation of material in this area contributes to large-scale turbulence. Additionally, C2, located at the center of the HFS, exhibits a higher star formation efficiency than other regions in G53.