2006ApJ...645L..41S

We report the first detection of ammonia in the Homunculus Nebula around η Carinae, which is also the first detection of emission from a polyatomic molecule in this or any other luminous blue variable (LBV) nebula. Observations of the NH₃(J,K)=(3,3) inversion transition made with the Australia Telescope Compact Array reveal emission at locations where infrared H₂emission had been detected previously, near the strongest dust emission in the core of the Homunculus. We also detect ammonia emission from the so-called strontium filament in the equatorial disk. The presence of NH₃around η Car hints that molecular shells around some Wolf-Rayet stars could have originated in prior LBV eruptions, rather than in cool red supergiant winds or the ambient interstellar medium. Combined with the lack of any CO detection, NH₃seems to suggest that the Homunculus is nitrogen-rich like the ionized ejecta around η Car. It also indicates that the Homunculus is a unique laboratory in which to study unusual molecule and dust chemistry, as well as their rapid formation in a nitrogen-rich environment around a hot star. We encourage future observations of other transitions like NH₃(1, 1) and (2, 2), related molecules like N₂H⁺, and renewed attempts to detect CO.