SIMBAD references

We report on a survey of NH₂D toward protostellar cores in low-mass star formation and quiescent regions in the Galaxy. Twenty-three out of thirty-two observed sources have significant (≳5 σ) NH₂D emission. Ion-molecule chemistry, which preferentially enhances deuterium in molecules above the local interstellar medium value value of 1.6x10^–5, sufficiently explains these abundances. NH₂D/NH₃ ratios toward class 0 sources yields information about the ``fossil remnants'' from the era prior to the onset of core collapse and star formation. We compare our observations with predictions of gas-phase chemical networks.