1999ApJ...527L.117Z

We present the discovery of shock-excited NH₃ in a well-collimated jet associated with the extremely young high-mass star IRAS 20126+4104. The NH₃ (3, 3) and (4, 4) emission is dominated by three clumps along the SiO jet. At the end of the jet, there exists strong and broad (±10 km.s^–1) NH₃ (3, 3) emission. With typical brightness temperatures greater than 500 K, the overall emission indicates a weakly inverted population and appears in an arc, consistent with the excitation by bow shocks. There are two bright spots in the NH₃ (3, 3) emission with brightness temperatures of approximately 2000 K. The narrow line width (1.5 km.s^–1 FWHM), the small sizes (<0".3), and the unusually high brightness temperature of the features are indicative of maser emission. Our observations provide clear evidence that NH₃ (3, 3) masers are excited in shock regions in molecular outflows.