Letter to the Editor Observation of DCO+ in the Large Magellanic Cloud

We report on the detection of DCO+ and, tentatively, DCN in their rotational J=2–1 transitions towards the N159 region in the Large Magellanic Cloud (LMC). These detections of deuterated molecules in an extragalactic source complement those already published by Chin et al. (1996). The resulting estimate of theHCO+/DCO+ abundance ratio is 120+60 −60 (total 2σ uncertainties).Assuming aGalacticD/H ratio for theLMC leads to an estimate of the kinetic temperature of the molecular gas and an upper limit to the fractional electron abundance of 10– 27 K and a few×10−5, respectively. The temperature estimate is in accordance with excitation calculations using a number of othermolecules. TheHCO+/DCO+ abundance ratio inN159 is a factor of a few higher than in cores ofGalacticmolecular clouds. This is probably due to a somewhat higher gas temperature and possibly a considerably higher electron abundance in N159. The estimated HCN/DCN abundance ratio is 60+50 −35 (total 2σ uncertainties).