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Chemical Models of Collapsing Envelopes

Published online by Cambridge University Press:  25 May 2016

Edwin A. Bergin
Edwin A. Bergin*
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

Abstract

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We discuss recent models of chemical evolution in the developing and collapsing protostellar envelopes associated with low-mass star formation. In particular, the effects of depletion of gas-phase molecules onto grain surfaces is considered. We show that during the middle to late evolutionary stages, prior to the formation of a protostar, various species selectively deplete from the gas phase. The principal pattern of selective depletions is the depletion of sulfur-bearing molecules relative to nitrogen-bearing species: NH3 and N2H+. This pattern is shown to be insensitive to the details of the dynamics and marginally sensitive to whether the grain mantle is dominated by polar or non-polar molecules. Based on these results we suggest that molecular ions are good tracers of collapsing envelopes. The effects of coupling chemistry and dynamics on the resulting physical evolution are also examined. Particular attention is paid to comparisons between models and observations.

Type
Part 1. Chemistry in Pre-Stellar Cores and Low-Mass Star-Forming Regions
Information
Symposium - International Astronomical Union , Volume 197: Astrochemistry: From Molecular Clouds to Planetary Systems , 2000 , pp. 51 - 60
Copyright
Copyright © Astronomical Society of the Pacific 2000 

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