2001ApJ...553L.181R

We report the detection of the (1, 1) and (2, 2) metastable lines of ammonia (NH₃) in the molecular cloud associated with the Wolf-Rayet (W-R) nebula NGC 2359. Besides the CO and H₂, this is the first molecule detected in the environs of a W-R star. Width (ΔV_1/2=3 km.s^–1) and radial velocity (V_LSR∼54 km.s^–1) indicate that the NH₃ lines arise from the molecular cloud that is interacting with the W-R star. The rotational temperature derived from the (1, 1) and (2, 2) line intensity ratios is about 30 K, significantly larger than the typical kinetic temperature of the ambient gas of ∼10 K. The derived NH₃ abundance is ∼10^–8. Line width, abundance, and kinetic temperature can be explained if NH₃ is released from dust grain mantles to the gas phase by shocks produced by the expansion of the bubble created by the W-R stellar wind. We briefly discuss the implications of the detection of warm NH₃ associated with a W-R star in connection to the hot NH₃ emission detected in the Galactic center and in the nuclei of external galaxies.