Letter to the Editor

The NH₂D/NH₃ ratio toward pre-protostellar cores around the UC region in IRAS 20293+3952^*

¹ Departament d'Astronomia i Meteorologia (IEEC-UB), Institut de Ciències del Cosmos, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain e-mail: gbusquet@am.ub.es
² Institut de Ciències de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciències, Torre C-5 parell, 08193 Bellaterra, Spain
³ Department of Physics and Astronomy, University College London, Grower Street, London WC1E 6BT, UK
⁴ Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, 02138, USA
⁵ Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan

Received: 26 April 2010
Accepted: 16 June 2010

Abstract

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 UC 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 UC region IRAS 20293+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, although outflow interactions and UV radiation could also play a role.