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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 709856.0, MPI für Astronomie / Publikationen_mpia
Chemical evolution in the early phases of massive star formation. I
Authors:Gerner, T.; Beuther, H.; Semenov, D.; Linz, H.; Vasyunina, T.; Bihr, S.; Shirley, Y. L.; Henning, T.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:Astronomy and Astrophysics
Start Page:id. A97 (31 pp)
Audience:Not Specified
Abstract / Description:Understanding the chemical evolution of young (high-mass) star-forming regions is a central topic in star formation research. 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 to high-mass protostellar objects to hot molecular cores and, finally, ultra-compact Hii regions at 1 mm and 3 mm with the IRAM 30 m telescope. We determined their large-scale chemical abundances and found that the chemical composition evolves along with the evolutionary stages. On average, the molecular abundances increase with time. We modeled the chemical evolution, using a 1D physical model where density and temperature vary from stage to stage coupled with an advanced gas-grain chemical model and derived the best-fit chi2 values of all relevant parameters. A satisfying overall agreement between observed and modeled column densities for most of the molecules was obtained. With the best-fit model we also derived a chemical age for each stage, which gives the timescales for the transformation between two consecutive stages. The best-fit chemical ages are ~10 000 years for the IRDC stage, ~60 000 years for the HMPO stage, ~40 000 years for the HMC stage, and ~10 000 years for the UCHii stage. Thus, the total chemical timescale for the entire evolutionary sequence of the high-mass star formation process is on the order of 105 years, which is consistent with theoretical estimates. Furthermore, based on the approach of a multiple-line survey of unresolved data, we were able to constrain an intuitive and reasonable physical and chemical model. The results of this study can be used as chemical templates for the different evolutionary stages in high-mass star formation. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Appendix A and Table 1 are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201322541/olm">http://www.aanda.org</A>Reduced spectra as FITS files are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> ( or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A97">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A97</A>
Free Keywords:stars: formation; stars: early-type; ISM: molecules; evolution
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-6361 %R 10.1051/0004-6361/201322541
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