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Abstract:
We present the study of deuteration of cyanoacetylene (HC3N) towards a sample of 28 high-mass star-forming cores divided into different evolutionary stages, from starless to evolved protostellar cores. We report for the first time the detection of DC3N towards 15 high-mass cores. The abundance ratios of DC3N with respect HC3N range in the interval 0.003–0.022, lower than those found in low-mas protostars and dark clouds. No significant trend with the evolutionary stage, or with the kinetic temperature of the region, has been found. We compare the level of deuteration of HC3N with those of other molecules towards the same sample, finding weak correlation with species formed only or predominantly in gas phase (N2H+ and HNC, respectively), and no correlation with species formed only or predominantly on dust grains (CH3OH and NH3, respectively). We also present a single-dish map of DC3N towards the protocluster IRAS 05358+3543, which shows that DC3N traces an extended envelope (∼0.37 pc) and peaks towards two cold condensations separated from the positions of the protostars and the dust continuum. The observations presented in this work suggest that deuteration of HC3N is produced in the gas of the cold outer parts of massive star-forming clumps, giving us an estimate of the deuteration factor prior to the formation of denser gas.
