2010A&A...517L...6B

The deuterium fractionation, D_frac, has been proposed as an evolutionary indicator in pre-protostellar and protostellar cores of low-mass star-forming regions. We investigate D_frac, with high angular resolution, in the cluster environment surrounding the UCHII region IRAS20293+3952.We performed high angular resolution observations with the IRAM Plateau de Bure Interferometer (PdBI) of the ortho-NH₂D1₁₁-1₀₁ line at 85.926GHz and compared them with previously reported VLA NH₃ data.We detected strong NH₂D emission toward the pre-protostellar cores identified in NH₃ and dust emission, all located in the vicinity of the UCHII region IRAS20293+3952. We found high values of D_frac≃0.1-0.8 in all the pre-protostellar cores and low values, D_frac<0.1, associated with young stellar objects.The high values of D_frac in pre-protostellar cores could be indicative of evolution, although outflow interactions and UV radiation could also play a role.