Evidence for Core-Core Collision in Barnard 68
Li D. Henkel C. Kraus A. Tang X. Baan W. Esimbek J. Wang K. Wu G. Liu T. Sobolev A.M. Zhou J. He Y. Komesh T.
1 June 2025Institute of Physics
Astrophysical Journal
2025#985Issue 2
The prestellar core Barnard 68 (B68) is a prototypical source to study the initial conditions and chemical processes of star formation. A previous numerical simulation suggested the southeastern bullet is impacting on the main body of B68. In order to obtain more observational evidence, mapping observations of the ground state SO (10-01) emission line at 30 GHz were made with the Effelsberg 100 m telescope. Based on the velocity field and channel maps derived from SO, three velocity components were clearly detected. The velocity field of the main body indicates rotation and is well fitted by a solid-body rotation model. The measured radial velocity difference between the bullet and the main core is about 0.4 km s−1, which is almost equal to the velocity obtained by the previous numerical simulation. Therefore, the bullet is most likely impacting on the rotating main body of B68. A 1D spherical non-local thermodynamic equilibrium Monte Carlo radiation transfer RATRAN code is performed to derive the radial abundance profile of SO by analyzing the observed velocity-integrated intensity. SO is depleted inside a 60″ (0.02 pc) radius from the core. The abundance stays constant at 2.0 × 10−9 for radii larger than 60″ from the center of the main core. The abundance is enhanced at the interface of the bullet and the main core, indicating that shock waves were produced by the collision between the bullet and the main core. In conclusion, based on the kinematical and chemical analysis, our observational results support the previously proposed core-core collision scenario in B68.
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Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi, 830011, China
University of Chinese Academy of Sciences, Beijing, 100049, China
Xinjiang Key Laboratory of Radio Astrophysics, Urumqi, 830011, China
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, 53121, Germany
Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing, 100101, China
Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, 100871, China
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, China
Ural Federal University, 19 Mira Street, Ekaterinburg, 620002, Russian Federation
Energetic Cosmos Laboratory, Nazarbayev University, Astana, 010000, Kazakhstan
Institute of Experimental and Theoretical Physics, Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Xinjiang Astronomical Observatory
University of Chinese Academy of Sciences
Xinjiang Key Laboratory of Radio Astrophysics
Max-Planck-Institut für Radioastronomie
Key Laboratory of Radio Astronomy and Technology
Kavli Institute for Astronomy and Astrophysics
Shanghai Astronomical Observatory
Ural Federal University
Energetic Cosmos Laboratory
Institute of Experimental and Theoretical Physics
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