Deuterated ammonia in galactic protostellar cores

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 (greater than or similar to5 sigma) NH2D emission. Ion-molecule chemistry, which preferentially enhances deuterium in molecules above the local interstellar medium value value of 1.6 x 10(-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.