First detection of the ground-state J_K = 1_0 → 0_0 submillimeter transition of interstellar ammonia

Creators: Keene, Jocelyn; Blake, Geoffrey A.; Phillips, T. G.

Abstract

The J_K = 1_0 → 0_0 transition of ammonia at 572.5 GHz has been detected in OMC-1 from NASA's Kuiper Airborne Observatory. The central velocity of the line (V_(LSR)≈ 9 km s^(-1)) indicates that it originates in the molecular cloud material, not in the hot core. The derived filling factor of ≳ 0.09 in a 2' beam implies a source diameter of ≳ 35" if it is a single clump. This clump area is much larger than that derived from observations of the 1_1 inversion transition. The larger optical depth in the 1_0 → 0_0 transition (75-350) can account for the increased source area and line width as compared with those seen in the 1_1 inversion transition.

Additional Information

© 1983 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1983 March 4; accepted 1983 April 13. We thank the staff of the KAO for their assistance in these observations. We are grateful to R. Genzel and P. Ho for their comments. This research has been supported by NASA grant NAG 2-1 to the California Institute of Technology.

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