EPoS Contribution
EPoS Contribution
The evolution of deuterated molecules in high-mass star formation

Thomas Gerner
MPIA, Heidelberg, DE
The chemical evolution in high-mass star-forming regions is still poorly constrained. Characterizing the chemistry of high-mass star formation in different evolutionary stages in a statistical sample combined with a modeling approach is a promising approach to derive a full time-dependent chemical picture. Studying the evolution of deuterated molecules allows to differentiate between subsequent stages of high-mass star formation regions, due to the strong temperature dependence of deuterium isotopic fractionation. We observed a sample of 59 sources including 19 infrared dark clouds, 20 high-mass protostellar objects, 11 hot massive cores and 9 ultracompact H2 regions in the (3-2) transitions of the four deuterated molecules DCN, DNC, DCO+ and N2D+ as well as their non-deuterated counterpart. The overall detection fraction of DCN, DNC and DCO+ is high and exceeds for most of the stages 50%. N2D+ was only detected in a few infrared dark clouds and high-mass protostellar objects. Potential reasons are problems in the bandpass at the frequency of the transition and lower abundances in the more evolved, warmer stages. We find median D/H ratios of ~0.02 for DCN, ~0.002 for DNC, ~0.0009 for DCO+ and ~0.02 for N2D+. While the D/H ratios of DNC and DCO+ and N2D+ decrease with time, DCN/HCN peaks at the HMC stage. We found a tight correlation of the D/H ratios with the luminosity of the central source, but not with the H2 column density. In combination with a previously observed set of 14 other molecules we fitted the calculated column densities with an elaborate 1D physico-chemical model with time-dependent D-chemistry. Good overall fits to the observed data have been obtained.
Collaborators:
Y. L. Shirley, Steward Obs., USA
H. Beuther, MPIA, Germany
D. Semenov, MPIA, Germany
H. Linz, MPIA, Germany
Th. Henning, MPIA, Germany
Suggested Session: Chemistry