2011ApJ...739L..15H

We present the first interferometric observations at 18.5 GHz of IRS 1 in NGC 7538. These observations include images of the nonmetastable ¹⁴NH₃ (9, 6) masers with a synthesized beam of 2 arcsec and images of the continuum emission with a synthesized beam of 150 mas. Of the maser emission, the previously known feature near v_LSR= -60 km/s is spectrally resolved into at least two components and we observe several new maser emission features near v_LSR= -57 km/s. The new maser emission near -57 km/s lies 250 ±90 mas northwest of the maser emission near -60 km/s. All of the masers are angularly unresolved indicating brightness temperatures T_B> 2000 K. We are also able to conclusively associate the ammonia masers with the position of IRS 1. The excitation of these rare ammonia masers is discussed in the context of the rich maser environment of IRS 1.