Recently, PhD student SUN Mingke from the star formation and evolution research group at the Xinjiang Astronomical Observatory (XAO) of the Chinese Academy of Sciences (CAS), along with his supervisor Prof. Jarken Esimbek and other collaborators, conducted a systematic study of the molecular cloud G34 using CO(J=1-0) data, as shown in the Figure. The study revealed cloud-cloud collision phenomena in this region and their impact on star formation.

The results have been published in Monthly Notices of the Royal Astronomical Society (2026, 546, 2285).

The researchers systematically analyzed the structure and dynamics of the molecular gas in G34, in which two molecular clouds at velocities of 38–40 km/s and 58–60 km/s exhibit a high degree of spatial overlap and share an identical distance of 3.03 kpc. The interaction interface between these two clouds shows a U-shaped structure, which is a typical observational signature of cloud-cloud collision. Furthermore, the velocity dispersion within the U-shaped structure is significantly enhanced, indicating that the cloud-cloud collision has substantially influenced the local gas dynamics.

They also examined the spatial distribution of various star formation tracers within G34 and found that approximately 80% of Class I young stellar objects, 78% of Class II young stellar objects, 92% of ATLASGAL clumps, 93% of 6.7 GHz methanol masers, and 83% of H ii regions are located within the potential collision region. These results strongly suggest that the star formation activity in G34 is highly correlated with the ongoing cloud-cloud collision process.

By combining H₂CO data at 6 and 2 cm observed with the Effelsberg 100-m telescope (Germany) and the Shanghai Tianma 65-m Radio Telescope (TMRT), as well as NH₃ data from the Nanshan 26-m telescope, the researchers performed a pixel-by-pixel modeling analysis of the physical conditions of the gas in the collision region using the non-Local Thermodynamic Equilibrium (LTE) radiative transfer code RADEX. The analysis revealed that in the collision region, the hydrogen molecular column density reaches 10⁴–10⁵ cm^-3, with an average kinetic temperature of 17 K. This aligns well with the dense post-shock conditions predicted by cloud-cloud collision simulations, providing an ideal setting for massive star formation.

This study provides new observational evidence for understanding the role of cloud-cloud collisions in triggering star formation, particularly massive star formation, and offers important clues for unraveling the dynamical evolution mechanisms within giant molecular clouds in the Milky Way.

                                             Red and white contours represent the integrated intensity of 12CO in the velocity intervals of 38–40 km s−1 and 58–63 km s−1, respectively.