AIRBORNE OBSERVATIONS OF THE 184 MICRON H_2~(18)O 2_(21) → 2_(12) TRANSITION IN THE SHOCKED REGION OF ORION BN-IRc2

摘要

We report the first far-IR detection of isotopic water in the Orion BN-IRc2 region from aboard the Kuiper Airborne Observatory. The observation of the 183.5290 μm H_2~(18)O 2_(21) → 2_(12) emission line indicates that it is likely to originate from shocked gas in the outflow around Orion BN-IRc2, rather than from warm gas of the Orion plateau, where the H_2O abundance is low ([H_2O]/[H] approx < 2.5 x 10~(-5)). Our observation infers a ratio of [H_2O]/[H] approx < 1.7 x 10~(-3,) which indicates that O is efficiently converted to H_2O in shocked gas.