Deuterium Fractionation as an Evolutionary Probe in the Infrared Dark Cloud G28.34+0.06
Abstract
We have observed the J = 3 - 2 transition of N2H+ and N2D+ to investigate the trend of deuterium fractionation with evolutionary stage in three selected regions in the infrared dark cloud (IRDC) G28.34+0.06 with the Submillimeter Telescope and the Submillimeter Array. A comprehensible enhancement of roughly 3 orders of magnitude in deuterium fractionation over the local interstellar D/H ratio is observed in all sources. In particular, our sample of massive star-forming cores in G28.34+0.06 shows a moderate decreasing trend over a factor of 3 in the N(N2D+)/N(N2H+) ratio with evolutionary stage, a behavior resembling that previously found in low-mass protostellar cores. This suggests a possible extension for the use of the N(N2D+)/N(N2H+) ratio as an evolutionary tracer to high-mass protostellar candidates. In the most evolved core, MM1, the N2H+(3-2) emission appears to avoid the warm region traced by dust continuum emission and emission of 13CO sublimated from grain mantles, indicating an instant release of gas-phase CO. The majority of the N2H+ and N2D+ emission is associated with extended structures larger than 8'' (~0.2 pc).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2010
- DOI:
- 10.1088/2041-8205/713/1/L50
- arXiv:
- arXiv:1003.1365
- Bibcode:
- 2010ApJ...713L..50C
- Keywords:
-
- ISM: abundances;
- ISM: clouds;
- ISM: individual objects: G28.34+0.06;
- stars: formation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 14 pages, 3 figures, and 2 tables, accepted by the Astrophysical Journal Letters