2024A&A...689A.140S

The feedback effect of massive stars can either accelerate or inhibit star formation activity within molecular clouds. Studying the morphology of molecular clouds near W5 offers an excellent opportunity to examine this feedback effect. We conducted a comprehensive survey of the W5 complex using the Purple Mountain Observatory 13.7 m millimeter telescope. This survey includes ¹²CO, ¹³CO, and C¹⁸O (J = 1 - 0), with a sky coverage of 6.6 deg² (136.0° < l < 138.75°, 0° < b < 2.4°). Furthermore, we performed simultaneous observations of the NH₃ (1,1) and NH₃ (2,2) lines in the four densest star-forming regions of W5, using the 26 m radio telescope of the Xinjiang Astronomy Observatory (XAO). Our analysis of the morphological distribution of the molecular clouds, distribution of high-mass young stellar objects (HMYSOs), ¹³CO/C¹⁸O abundance ratio, and the stacked average spectral line distribution at different 8 μm thresholds provide compelling evidence of triggering. Within the mapped region, we identified a total of 212 molecular clumps in the ¹³CO cube data using the astrodendro algorithm. Remarkably, approximately 26.4% (56) of these clumps demonstrate the potential to form massive stars and 42.9% (91) of them are gravitationally bound. Within clumps that are capable of forming high-mass stars, there is a distribution of class I YSOs, all located in dense regions near the boundaries of the HII regions. The detection of NH₃ near the most prominent cores reveals moderate kinetic temperatures and densities (as CO). Comparing the T_kin and T_ex values reveals a reversal in trends for AFGL 4029 (higher T_ex and lower T_kin) and W5-W1, indicating the inadequacy of optically thick CO for dense region parameter calculations. Moreover, a comparison of the intensity distributions between NH₃ (1,1) and C¹⁸O (1-0) in the four densest region reveals a notable depletion effect in AFGL 4029, characterised by a low T_kin (9 K) value and a relatively high NH₃ column density, 2.5 × 10¹⁴ cm^–2. By classifying the ¹³CO clumps as: “feedback,” “non-feedback,” “outflow,” or “non-outflow” clumps, we observe that the parameters of the “feedback” and “outflow” clumps exhibit variations based on the intensity of the internal 8 μm flux and the outflow energy, respectively. These changes demonstrate a clear linear correlation, which distinctly separate them from the parameter distributions of the “non-feedback” and “non-outflow” clumps, thus providing robust evidence to support a triggering scenario.