A Disk/Jet System toward the High‐Mass Young Star in AFGL 5142

We present observational studies of a high-mass star-forming region AFGL 5142 in the NH 3 ( J , K ) = (1,1), (2,2), (3,3), and (4,4) inversion transitions. We discover a compact structure of 1'' (or 1800 AU) in NH 3 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 NH 3 structure, with a temperature of 70 K, gives rise to a broad NH 3 line emission of 6.4 km s -1 (FWHM). The small size of the NH 3 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 NH 3 gas. A faint component of NH 3 emission can be identified, especially in the highly excited NH 3 (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.