2012ApJ...756..170Q

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 8x10³ yr. The kinematics of the HMC are probed by high-excitation CH₃ OH 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, 1.5x10^–3 M_☉/yr, 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.