We present a study of outflow , infall , and rotation in a \sim 10 ^ { 5 } ~ { } L _ { \odot } star-forming region , IRAS 18360-0537 , with Submillimeter Array ( SMA ) and IRAM 30m observations .
The 1.3 mm continuum map shows a 0.5 pc dust ridge , of which the central compact part has a mass of \sim 80 M _ { \odot } 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 \pm 50 K and a mass of \sim 13 M _ { \odot } .
The outflow has a gas mass of 54 ~ { } M _ { \odot } and a dynamical timescale of 8 \times 10 ^ { 3 } yr .
The kinematics of the HMC is probed by high-excitation CH _ { 3 } OH and CH _ { 3 } CN lines , which are detected at sub-arcsecond 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 \times 10 ^ { -3 } ~ { } M _ { \odot } 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 ^ { 13 } CO and C ^ { 18 } O ( 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 \sim 10 M _ { \odot } embedded within MM1 will develop into an O star via disk accretion and envelope infall .