We present a study of outflow, infall, and rotation in a ~105 L ☉ star-forming region, IRAS 18360-0537, with Submillimeter Array and IRAM 30?m observations. The 1.3?mm continuum map shows a 0.5?pc dust ridge, of which the central compact part has a mass of ~80 M ☉ and harbors two condensations, MM1 and MM2. The CO (2-1) and SiO (5-4) maps reveal a biconical outflow centered at MM1, which is a hot molecular core (HMC) with a gas temperature of 320 ± 50 K and a mass of ~13 M ☉. The outflow has a gas mass of 54 M ☉ and a dynamical timescale of 8 × 103 yr. The kinematics of the HMC are probed by high-excitation CH3OH and CH3CN lines, which are detected at subarcsecond resolution and unveil a velocity gradient perpendicular to the outflow axis, suggesting a disk-like rotation of the HMC. An infalling envelope around the HMC is evidenced by CN lines exhibiting a profound inverse P Cygni profile, and the estimated mass infall rate, 1.5 × 10–3 M ☉?yr–1, is well comparable to that inferred from the mass outflow rate. A more detailed investigation of the kinematics of the dense gas around the HMC is obtained from the 13CO and C18O (2-1) lines; the position-velocity diagrams of the two lines are consistent with the model of a free-falling and Keplerian-like rotating envelope. The observations suggest that the protostar of a current mass ~10 M ☉ embedded within MM1 will develop into an O star via disk accretion and envelope infall.
展开▼
