Deuteration as an evolutionary tracer in massive-star formation
Abstract
Context. Theory predicts, and observations confirm, that the column density ratio of a molecule containing D to its counterpart containing H can be used as an evolutionary tracer in the low-mass star formation process.
Aims: Since it remains unclear if the high-mass star formation process is a scaled-up version of the low-mass one, we investigated whether the relation between deuteration and evolution can be applied to the high-mass regime.
Methods: With the IRAM-30 m telescope, we observed rotational transitions of N2D+ and N2H+ and derived the deuterated fraction in 27 cores within massive star-forming regions understood to represent different evolutionary stages of the massive-star formation process.
Results: The abundance of N2D+ is higher at the pre-stellar/cluster stage, then drops during the formation of the protostellar object(s) as in the low-mass regime, remaining relatively constant during the ultra-compact HII region phase. The objects with the highest fractional abundance of N2D+ are starless cores with properties very similar to typical pre-stellar cores of lower mass. The abundance of N2D+ is lower in objects with higher gas temperatures as in the low-mass case but does not seem to depend on gas turbulence.
Conclusions: Our results indicate that the N2D+-to-N2H+ column density ratio can be used as an evolutionary indicator in both low- and high-mass star formation, and that the physical conditions influencing the abundance of deuterated species likely evolve similarly during the processes that lead to the formation of both low- and high-mass stars.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 2011
- DOI:
- 10.1051/0004-6361/201116631
- arXiv:
- arXiv:1103.5636
- Bibcode:
- 2011A&A...529L...7F
- Keywords:
-
- stars: formation;
- ISM: clouds;
- ISM: molecules;
- radio lines: ISM;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted by A&