2026-10-12T03:08:03Z https://www.scidb.cn/oai

10.57760/sciencedb.39660 2026-06-10T18:46:41Z

2026-06-10 Possible collision-induced outflows and triggered star formation in the molecular complex G34 doi:10.57760/sciencedb.39660 en G34 is an active star-forming region with complex velocity components. Within the 38–63 km s|$^{-1}$| velocity range, we identify a possible cloud–cloud collision at a distance of |$\sim$|3 kpc. Using the |$\rm ^{12}CO$| (⁠|${\it J}$| = 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 53–63 km s|$^{-1}$| exhibit a U-shaped complementary distribution and a bridge feature in the position–velocity diagram. At the collision interface, the velocity dispersion of |$\rm ^{12}CO$| is significantly enhanced, which may result from the impact of the collision. We analyse the spatial distributions of 6.7 GHz CH|$_3$|OH masers, APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) clumps, H ii 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 H i self-absorption features and molecular outflows at the interface. Based on observations of 6 and 2 cm H|$_2$|CO lines from the Effelsberg 100 m and Tianma Radio Telescope 64 m telescopes, along with NH|$_3$| lines from the Nanshan 26 m telescope, we derive an H|$_2$| volume density of |$10^4$|–|$10^5$| cm|$^{-3}$| in the compressed region. Finally, we compare the collision time-scales (⁠|$\gtrsim$|0.35 Myr), the dynamical age of the H ii region G34.26+0.15 (⁠|$\gtrsim$|0.33 Myr), and the outflow time-scale (⁠|$\sim$|7.5 Myr). 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. stars: formation; ISM: clouds; ISM: kinematics and dynamics; ISM: molecules Mingke Sun PUBLIC https://creativecommons.org/licenses/by/4.0/ dataset http://www.doi.org/10.1093/mnras/staf2285 Science Data Bank