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Astron. Astrophys. 319, L21-L24 (1997)

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Letter to the Editor

Observation of DCO + in the Large Magellanic Cloud

A. Heikkilä 1, L.E.B. Johansson 1 and H. Olofsson 2

1 Onsala Space Observatory, S-439 92 Onsala, Sweden
2 Stockholm Observatory, S-133 36 Saltsjöbaden, Sweden

Received 30 July 1996 / Accepted 5 December 1996

Abstract

We report on the detection of DCO [FORMULA] 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 the HCO [FORMULA] /DCO [FORMULA] abundance ratio is 120 [FORMULA] (total 2 [FORMULA] uncertainties). Assuming a Galactic D/H ratio for the LMC 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 [FORMULA] 10-5, respectively. The temperature estimate is in accordance with excitation calculations using a number of other molecules. The HCO [FORMULA] /DCO [FORMULA] abundance ratio in N159 is a factor of a few higher than in cores of Galactic molecular 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 [FORMULA] (total 2 [FORMULA] uncertainties).

Key words: ISM:molecules – Galaxies:abundances – Galaxies:ISM – Magellanic Clouds – Radio lines:galaxies – Radio lines:ISM

Send offprint requests to: A. Heikkilä

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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