Protostars and Planets VI, Heidelberg, July 15-20, 2013
The chemical evolution in the early phases of massive star formation
Gerner, Thomas (Max Planck Institute for Astronomy)
Beuther, Henrik (Max Planck Institute for Astronomy)
Semenov, Dmitry (Max Planck Institute for Astronomy)
Linz, Hendrik (Max Planck Institute for Astronomy)
Vasyunina, Tatiana (Charlottesville, University of Virginia)
Dullemond, Cornelis (Heidelberg Universitšt, ZAH, ITA)
Bihr, Simon (Max Planck Institute for Astronomy)
Henning, Thomas (Max Planck Institute for Astronomy)
Understanding the chemical evolution of young (high-mass) star-forming regions is a central topic in star formation research. The chemistry is employed as a unique tool: 1) to investigate the underlying physical processes and 2) to characterize the evolution of the chemical composition. With these aims in mind, we observed a sample of 59 high-mass star-forming regions at different evolutionary stages varying from the early starless phase of Infrared Dark Clouds (IRDC) to High Mass Protostellar Objects (HMPO) to Hot Molecular Cores (HMC) and, finally, Ultra Compact HII regions (UCHII) at 1mm and 3mm with the IRAM 30m telescope. We determined their large-scale chemical abundances and column densities and found that the chemical composition evolves along with the evolutionary stages.
We modeled the chemical evolution in these environments, using a 1D physical model where density and temperature vary from stage to stage coupled with an advanced gas-grain chemical model. By varying the temperature and density structure the best-fit chi-square values of all the relevant parameters were derived. A satisfying overall agreement between observed and modeled column densities for most of the molecules in all evolutionary stages was obtained. In addition the best-fit model provided chemical ages for each phase.
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