H II regions and supernova remnants associated with molecular clouds: A pilot study with the SARAO MeerKAT Galactic Plane Survey

Massive stars (mass >8 M_⊙) release vast amounts of energy into the interstellar medium through their stellar winds, photoionizing radiation, and supernova explosions. These processes may compress nearby regions, triggering further star formation, but the significance of triggered star formation across the Galactic disc is not well understood. This pilot study combines 1.3GHz continuum data from the South African Radio Astronomy Observatory (SARAO) MeerKAT Galactic Plane Survey (SMGPS) with ¹³CO (2–1) data from the Structure, Excitation, and Dynamics of the Inner Galactic Interstellar Medium (SEDIGISM) survey to identify and examine molecular clouds associated with HII regions and supernovae remnants (SNRs). We focus on their physical properties and massive star formation potential. We identify 268 molecular clouds from the SEDIGISM tile covering the Galactic plane region 341^◦ ≤ ℓ ≤ 343^◦ and |b| ≤ 0.5^◦, of which 90 clouds (34 per cent) are associated with SMGPS extended sources. Compared to unassociated clouds, we find that associated clouds exhibit significantly higher mean mass (∼9600 M_⊙ versus ∼2500 M_⊙) and average gas surface density (∼104 M_⊙pc^-2 versus ∼67 M_⊙pc^-2), and slightly elevated but comparable virial parameters. We also find that the size–linewidth scaling relation is steeper for associated clouds compared to unassociated clouds. In addition, radio luminosity shows a positive correlation with total complex mass, and the ratio L_radio/ M_complex increases with source size, consistent with an evolutionary sequence where expanding HII regions progressively disrupt their natal molecular environment. These findings suggest an enhanced dynamical activity for the associated clouds and support the hypothesis that feedback from massive stars influences molecular cloud properties and may trigger star formation.