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 ^{14}NH_3 (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 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 milliarcseconds 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.

5 pages, 2 figures, 1 table, accepted to ApJL EVLA Special Issue

References in corpus (3)

• The Expanded Very Large Array -- a New Telescope for New Science
• NGC7538 IRS1 - an ionized jet powered by accretion
• The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations

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• New Maser Emission from Nonmetastable Ammonia in NGC 7538. III. Detection of the (10,6) Transition and a Velocity Gradient
• New Maser Emission from Nonmetastable Ammonia in NGC 7538. II. Green Bank Telescope Observations Including Water Masers