Detection of DCO in a circumstellar disk
نویسندگان
چکیده
We report the first detection of DCO in a circumstellar disk. The DCO J=5–4 line at 360.169 GHz is observed with the 15m James Clerk Maxwell Telescope in the disk around the pre-main sequence star TW Hya. Together with measurements of the HCO and HCO J=4–3 lines, this allows an accurate determination of the DCO/HCO ratio in this disk. The inferred value of 0.035±0.015 is close to that found in cold pre-stellar cores and is somewhat higher than that measured in the envelope around the low-mass protostar IRAS 16293 -2422. It is also close to the DCN/HCN ratio obtained for pristine cometary material in the jet of comet Hale-Bopp. The observed DCO/HCO ratio for TW Hya is consistent with theoretical models of disks which consider gas-phase fractionation processes within a realistic 2-D temperature distribution and which include the effects of freeze-out onto grains.
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