Possible collision-induced outflows and triggered star formation in the molecular complex G34
Sun M. Esimbek J. Henkel C. Zhou J. Wu G. He Y. Li D. Tang X. Komesh T. Berdikhan D. Ma Y. Tursun K. Zhou D. Sobolev A.M. Jandaolet Q. Sailanbek S. Turekhanova K. Gordon M.
1 February 2026Oxford University Press
Monthly Notices of the Royal Astronomical Society
2026#546Issue 2
G34 is an active star-forming region with complex velocity components. Within the 38–63kms-1 velocity range, we identify a possible cloud–cloud collision at a distance of ~3kpc. Using the 12CO (J= 1–0) line from the Purple Mountain Observatory 13.7-m millimeter telescope to trace the diffuse gas structures associated with the collision. The gas components at 38–50 and 53–63kms-1 exhibit a U-shaped complementary distribution and a bridge feature in the position–velocity diagram. At the collision interface, the velocity dispersion of 12CO is significantly enhanced, which may result from the impact of the collision. We analyse the spatial distributions of 6.7GHz CH3OH masers, APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) clumps, Hii regions, young stellar objects, and O-type stars, finding that most are concentrated near the collision interface. This supports a strong coupling between cloud–cloud collisions and star formation. In addition, we detect Hi self-absorption features and molecular outflows at the interface. Based on observations of 6 and 2cm H2CO lines from the Effelsberg 100m and Tianma Radio Telescope 64m telescopes, along with NH3 lines from the Nanshan 26m telescope, we derive an H2 volume density of 104–105cm-3 in the compressed region. Finally, we compare the collision time-scales (≳0.35Myr), the dynamical age of the Hii region G34.26+0.15 (≳0.33Myr), and the outflow time-scale (~7.5Myr). The results suggest that gas at the base of the U-shaped structure was compressed during the collision and driven into the outflow. After millions of years of evolution, the gas density increased, potentially triggering star formation.
ISM: clouds , ISM: individual objects: G34 , ISM: kinematics and dynamics , ISM: molecules , stars: formation
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State Key Laboratory of Radio Astronomy and Technology, Xinjiang Astronomical Observatory, CAS, 150 Science 1-Street, Xinjiang, Urumqi, 830011, China
University of the Chinese Academy of Sciences, Beijing, 100080, China
Xinjiang Key Laboratory of Radio Astrophysics, Urumqi, 830011, China
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, 53121, Germany
Energetic Cosmos Laboratory, Nazarbayev University, Astana, 010000, Kazakhstan
Institute of Experimental and Theoretical Physics, Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Ural Federal University, 19 Mira Street, Ekaterinburg, 620002, Russian Federation
Department of Electronics and Astrophysics, Faculty of Physics and Technology, Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
Hartebeesthoek Radio Astronomy Observatory, South Africa
Open University of Tanzania, Tanzania
State Key Laboratory of Radio Astronomy and Technology
University of the Chinese Academy of Sciences
Xinjiang Key Laboratory of Radio Astrophysics
Max-Planck-Institut für Radioastronomie
Energetic Cosmos Laboratory
Institute of Experimental and Theoretical Physics
Ural Federal University
Department of Electronics and Astrophysics
Hartebeesthoek Radio Astronomy Observatory
Open University of Tanzania
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