Kinematics and star formation of hub-filament systems in W49A

¹ XingJiang Astronomical Observatory, Chinese Academy of Sciences(CAS), Urumqi 830011, PR China
e-mail: zhangwenjun@xao.ac.cn; zhoujj@xao.ac.cn
² University of Chinese Academy of Sciences, Beijing 100049, PR China
³ Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Urumqi 830011, PR China
⁴ Xinjiang Key Laboratory of Radio Astrophysics, Urumqi 830011, PR China
⁵ Netherlands Institute for Radio Astronomy, ASTRON, 7991 PD Dwingeloo, The Netherlands
⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁷ Energetic Cosmos Laboratory, Nazarbayev University, Astana 010000, Kazakhstan
⁸ Faculty of Physics and Technology, Al-Farabi Kazakh National University, Almaty 050040, Kazakhstan

Received: 13 November 2023
Accepted: 30 May 2024

Abstract

Aims. W49A is a prominent giant molecular cloud (GMC) that exhibits strong star formation activities, yet its structural and kinematic properties remain uncertain. Our study aims to investigate the large-scale structure and kinematics of W49A, and elucidate the role of filaments and hub-filament systems (HFSs) in its star formation activity.

Methods. We utilized continuum data from Herschel and the James Clerk Maxwell Telescope (JCMT) as well as the molecular lines ¹²CO (3–2), ¹³CO (3–2), and C¹⁸O (3–2) to identify filaments and HFSs within W49A. Further analysis focused on the physical properties, kinematics, and mass transport within these structures. Additionally, recombination line emission from the H I/OH/Recombination (THOR) line survey was employed to trace the central H II region and ionized gas.

Results. Our findings reveal that W49A comprises one blue-shifted (B-S) HFS and one red-shifted (R-S) HFS, each with multiple filaments and dense hubs. Notably, significant velocity gradients were detected along these filaments, indicative of material transport toward the hubs. High mass accretion rates along the filaments facilitate the formation of massive stars in the HFSs. Furthermore, the presence of V-shaped structures around clumps in position-velocity diagrams suggests ongoing gravitational collapse and local star formation within the filaments.

Conclusions. Our results indicate that W49A consists of one R-S HFS and one B-S HFS, and that the material transport from filaments to the hub promotes the formation of massive stars in the hub. These findings underscore the significance of HFSs in shaping the star formation history of W49A.