Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.342s&link_type=abstract
The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole
Astronomy and Astrophysics
Astronomy
Scientific paper
In the early evolutionary stages of star formation process, sequential depletion of molecular species on grain mantles nurtures a peculiar low-temperature chemistry due to the removal of important gas-phase reactants. One example is the removal of the gas-phase CO, which promotes ion-molecular reactions and consequently induces a sharp increase in the abundance of deuterated molecules in dense cores. This chemical signature has profound implications as being an indicator of the thermal history and evolutionary stages of star forming cores. In the case of low-mass star-formation, studies have shown that the deuterium fractionation of N_2H^+, N(N_2D^+)/N(N_2H^+), exhibits an increasing trend with dynamical age in the prestellar phase but a decreasing trend in the protostellar phase, just as is anticipated by chemical models considering the variation of kinetic temperature as well as the gas-phase CO abundances in these objects. There is so far less evidence of a consistent behavior of this deuterium fractionation in the case of high-mass protostellar candidates. In this presentation, we show our recent investigation of deuterium fractionation over a sample of massive star-forming clumps in infrared dark clouds (IRDCs). Toward 14 clumps in three nearby IRDCs G28.34+0.06, G34.43+0.24, and IRAS 18151-1208, we discovered a decreasing trend in their N(N_2D^+)/N(N_2H^+) over a factor of 10 with evolutionary stage inferred from gas temperature. This behavior resembles what previously found in low-mass protostellar cores.
Chen H.-R. V.
Liu Shen-Ye
Su Yu-Nang
Zhang Qian
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