The NH2D/NH3 ratio toward pre-protostellar cores around the UC H(ii) region in IRAS 20293+3952

Abstract

Context. The deuterium fractionation, D(frac), has been proposed as an evolutionary indicator in pre-protostellar and protostellar cores of low-mass star-forming regions. Aims. We investigate D(frac), with high angular resolution, in the cluster environment surrounding the UC H(II) region IRAS 20293+3952. Methods. We performed high angular resolution observations with the IRAM Plateau de Bure Interferometer (PdBI) of the ortho-NH2D 111-101 line at 85.926 GHz and compared them with previously reported VLA NH3 data. Results. We detected strong NH2D emission toward the pre-protostellar cores identified in NH3 and dust emission, all located in the vicinity of the UCH(II) region IRAS 20293+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. Conclusions. 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. © 2010 ESO.