2013ApJ...770..142N

Using a broadband, high spectral resolution survey toward the Orion Kleinmann-Low nebula acquired with Herschel/HIFI as part of the Herschel Observations of Extra-Ordinary Sources key program, we derive the abundances of H₂ O and HDO in the different spatial/velocity components associated with this massive star-forming region: the Hot Core, Compact Ridge, and Plateau. A total of 20 transitions of H₂¹⁸O, 14 of H₂¹⁷O, 37 of HD¹⁶O, 6 of HD¹⁸O, and 6 of D₂ O are used in the analysis, spanning from ground state transitions to over 1200 K in upper-state energy. Low-excitation lines are detected in multiple components, but the highest-excitation lines (E_u > 500 K) are well modeled as emitting from a small (∼2'') clump with a high abundance of H₂ O (χ = 6.5x10^–4 relative to H₂) and a HDO/H₂O ratio of 0.003. Using high spatial resolution (1.''5x1.''1) images of two transitions of HDO measured by the Atacama Large Millimeter/Submillimeter Array as part of its science verification phase, we identify this component as located near, but not directly coincident with, known continuum sources in the Hot Core region. Significant HDO/H₂ O fractionation is also seen in the Compact Ridge and Plateau components. The outflowing gas, observed with both emission and absorption components, has a lower HDO/H₂ O ratio than the compact components in Orion Kleinmann-Low, which we propose could be due to modification by gas-phase shock chemistry.