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We report molecular line observations of the massive protostellar sourceG339.88-1.26 with the Atacama Large Millimeter/Submillimeter Array. Theobservations reveal a highly collimated SiO jet extending from the 1.3 mmcontinuum source, which connects to a slightly wider but still highlycollimated CO outflow. Rotational features perpendicular to the outflow axisare detected in various molecular emissions, including SiO, SO2, H2S, CH3OH,and H2CO emissions. Based on their spatial distributions and kinematics, wefind that they trace different parts of the envelope-disk system. The SiOemission traces the disk and inner envelope in addition to the jet. The CH3OHand H2CO emissions mostly trace the infalling-rotating envelope, and areenhanced around the transition region between envelope and disk, i.e., thecentrifugal barrier. The SO2 and H2S emissions are enhanced around thecentrifugal barrier, and also trace the outer part of the disk. Envelopekinematics are consistent with rotating-infalling motion, while those of thedisk are consistent with Keplerian rotation. The radius and velocity of thecentrifugal barrier are estimated to be about 530 au and 6 km/s, leading to acentral mass of about 11 solar masses, consistent with estimates based onspectral energy distribution fitting. These results indicate that an orderedtransition from an infalling-rotating envelope to a Keplerian disk through acentrifugal barrier, accompanied by changes of types of molecular lineemissions, is a valid description of this massive protostellar source. Thisimplies that at least some massive stars form in a similar way as low-massstars via Core Accretion.

An Ordered Envelope-disk Transition in the Massive Protostellar Source G339.88-1.26