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.