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Probable detection of H2D+ in the starless core Barnard 68

M. R. Hogerheijde·P. Caselli·M. Emprechtinger·F. F. S. van der Tak·J. Alves·A. Belloche·R. Guesten·A. A. Lundgren·L-A. Nyman·N. Volgenau·M. C. Wiedner
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Abstract

The presence of H2D+ in dense cloud cores underlies ion-molecule reactions that strongly enhance the deuterium fractionation of many molecular species. We determine the H2D+ abundance in one starless core, Barnard 68, that has a particularly well established physical, chemical, and dynamical structure. We observed the ortho-H2D+ ground-state line 1_10-1_11, the N2H+ J=4-3 line, and the H13CO+ 4-3 line with the APEX telescope. We report the probable detection of the o-H2D+ line at an intensity Tmb=0.22 +- 0.08 K and exclusively thermal line width, and find only upper limits to the N2H+ 4-3 and H13CO+ 4-3 intensities. Within the uncertainties in the chemical reaction rates and the collisional excitation rates, chemical model calculations and excitation simulations reproduce the observed intensities and that of o-H2D+ in particular.

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M. R. Hogerheijde, P. Caselli, M. Emprechtinger, F. F. S. van der Tak, J. Alves, A. Belloche, R. Guesten, A. A. Lundgren, L-A. Nyman, N. Volgenau, M. C. Wiedner. 2006-05-22. Probable detection of H2D+ in the starless core Barnard 68. https://doi.org/10.1051/0004-6361%3A20065104

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