The NH2D/NH3 ratio toward pre-protostellar cores around the UC$ion{H}{ii}$?region in IRAS?20293+3952

摘要

Context. The deuterium fractionation, ,has been proposed as an evolutionary indicator in pre-protostellar and protostellar cores of low-mass star-forming regions. Aims. We investigate ,with high angular resolution, in the cluster environment surrounding the UCH II region IRAS20293+3952. Methods. 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. 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 IRAS20293+3952. We found high values of 0.1-0.8 in all the pre-protostellar cores and low values, <0.1, associated with young stellar objects. Conclusions. The high values of in pre-protostellar cores could be indicative of evolution, althoughoutflow interactions and UV radiation could also play a role. Key words: stars: formation - ISM: individual objects: IRAS20293+3952 - ISM: clouds- ISM: molecules