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Q. Zhang, T.R. Hunter, T.K. Sridharan, P.T.P. Ho (Harvard Smithsonian Center for Astrophysics)
We present observational studies of a high-mass star forming region AFGL 5142 in the \rm{NH3} (J,K)=(1,1), (2,2), (3,3) and (4,4) inversion transitions. We discover a compact structure of 1'' (or 1800AU) in \rm{NH3} emission toward the position of a high-mass young star. The star, with a spectral type of B2 if it is at the zero-age main-sequence, excites a weak centimeter continuum source and drives a well collimated SiO jet. The compact \rm{NH3} structure, with a temperature of 70 K, gives rise to a broad \rm{NH3} line emission of 6.4 km~s-1 (full width at half maximum). The small size of the \rm{NH3} feature, broad line emission and the association with a SiO jet indicate that the object is most likely an unresolved rotating disk. The compact disk is embedded in a flattened core of gas temperatures of about 20 K. The extended core delineates an `X' shape with the SiO jet located in the void of the dense and cold \rm{NH3} gas. A faint component of \rm{NH3} emission can be identified, especially in the highly excited \rm{NH3} (3,3) and (4,4) lines, tracing the SiO jet. This component, arising from hot gas of about 170 K, is likely heated by shocks in the outflow. The coincidence of a disk and a jet with the radio continuum source toward AFGL 5142 indicates that this high-mass star may have formed via a disk mediated accretion process.