Extended CO(10) survey and ammonia measurements towards two bubble regions in W5: feedback on molecular gas and clumps

Abstract

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 12 CO, 13 CO, and C 18 O ( J = 1 − 0), with a sky coverage of 6.6 deg 2 (136.0° < l < 138.75°, 0° < b < 2.4°). Furthermore, we performed simultaneous observations of the NH 3 (1,1) and NH 3 (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), 13 CO/C 18 O 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 13 CO 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 H II regions. The detection of NH 3 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 NH 3 (1,1) and C 18 O (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 NH 3 column density, 2.5 × 10 14 cm −2 . By classifying the 13 CO 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.