Detection of D2H+ in the dense interstellar medium

Abstract

The 692 GHz para ground-state line of D2H+ has been detected at the Caltech Submillimeter Obser-vatory towards the pre-stellar core 16293E (Vastel, Phillips & Yoshida, 2004). The derived D2H + abundance is comparable to that of H2D+, as determined by observations of the 372 GHz Ime of ortho-H2D +. This is an observational verification of recent theoretical predictions (Roberts, Herbst & Millar 2003), developed to explain the large deuteration ratios observed in cold, high-density regions of the interstellar medium associated with low mass pre-stellar cores and protostars. This detection confirms expectations that the multiply deuterated forms of H3+ were missing factors of earlier models. The inclusion of D 2H+ and D3+ in the models leads to predictions of higher values of the D/H ratio in the gas phase.