| Abstract
| - Context. The deuterium fractionation, $D_{\mathrm{frac}}$, has been proposed as an evolutionary indicator in pre-protostellar and protostellar cores of low-mass star-forming regions. Aims. We investigate $D_{\mathrm{frac}}$, with high angular resolution, in the cluster environment surrounding the UC $\ion{H}{ii}$ region IRAS 20293+3952. Methods. We performed high angular resolution observations with the IRAM Plateau de Bure Interferometer (PdBI) of the ortho-NH 2D 1 11-1 01 line at 85.926 GHz and compared them with previously reported VLA NH 3 data. Results. We detected strong NH 2D emission toward the pre-protostellar cores identified in NH 3 and dust emission, all located in the vicinity of the UC $\ion{H}{ii}$ region IRAS 20293+3952. We found high values of $D_{\mathrm{frac}}$ $\simeq$ 0.1-0.8 in all the pre-protostellar cores and low values, $D_{\mathrm{frac}}$ < 0.1, associated with young stellar objects. Conclusions. The high values of $D_{\mathrm{frac}}$ in pre-protostellar cores could be indicative of evolution, although outflow interactions and UV radiation could also play a role.
|
