Detection of Extended Hot Water in the Outflow from NGC 2071

We report the results of spectroscopic mapping observations carried out toward an ~1' × 1' region within the northern lobe of the outflow from NGC 2071 using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope . These observations covered the 5.2-37 μm spectral region and have led to the detection of a number of ionic, atomic, and molecular lines, including fine-structure emission of Si + , Fe + , S ++ , S, the S (0)- S (7) pure rotational lines of H 2 , the R (3) and R (4) transitions of HD, and at least eleven transitions of H 2 O. In addition, the 6.2, 7.4, 7.6, 7.9, 8.6, and 11.3 μm PAH emission bands were also observed and several transitions of OH were tentatively detected. Most of the detected line transitions were strong enough to map, including, for the first time, three transitions of hot H 2 O. We find that (1) the water emission is extended; (2) the extended emission is aligned with the outflow; and (3) the spatial distribution of the water emission generally follows that observed for H 2 . Based on the measured line intensities, we derive an HD abundance relative to H 2 of (1.1–1.8) × 10 −5 and an H 2 O number density of 12-29 cm −3 . The H 2 density in the water-emitting region is not well constrained by our observations, but is likely between 3 × 10 4 and 10 6 cm −3 , yielding an H 2 O abundance relative to H 2 of between 2 × 10 −5 and 6 × 10 −4 . Finally, we note a possible departure from the H 2 O ortho-to-para ratio of 3 : 1 expected for water formed in hot postshocked gas, suggesting that a significant fraction of the water vapor we detect may arise from H 2 O sputtered from cold dust grains.