2 00 1 Shocked ammonia in the WR nebula NGC 2359

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 (WR) nebula NGC2359. Besides the CO and H2, this is the first molecule detected in the environs of a WR star. Width (∆V1/2 = 3km s ) and radial velocity (VLSR ∼ 54 km s ) indicate that the NH3 lines arises from the molecular cloud which is interacting with the WR star. The rotational temperature derived from the (1,1) and (2,2) line intensity ratios is about 30K, significantly larger than the typical kinetic temperature of the ambient gas of ∼ 10K. The derived NH3 abundance is ∼ 10 . Linewidth, 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 WR stellar wind. We briefly discuss the implications of the detection of warm NH3 associated with a WR star in connection to the hot NH3 emission detected in the Galactic Center and in the nuclei of external galaxies. Subject headings: ISM: abundances — ISM: individual (NGC 2359) — ISM: molecules — Stars: individual (HD 56925) — Stars: Wolf-Rayet