New Maser Emission from Nonmetastable Ammonia in NGC 7538
Abstract
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 arcseconds and images of the continuum emission with a synthesized beam of 150 milliarcseconds. Of the maser emission, the previously known feature near vLSR = -60 km/s is spectrally resolved into at least two components and we observe several new maser emission features near vLSR = -57 km/s. The new maser emission near -57 km/s lies 250 +/- 90 milliarcseconds northwest of the maser emission near -60 km/s. All of the masers are angularly unresolved indicating brightness temperatures TB > 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.
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