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Chemistry in the Envelopes around Massive Young Stars

Published online by Cambridge University Press:  30 March 2016

Ewine F. van Dishoeck  and
Floris F.S. van der Tak
Ewine F. van Dishoeck
Affiliation:
Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
Floris F.S. van der Tak
Affiliation:
Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands

Abstract

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Recent chemical studies of high-mass star-forming regions at submillimeter and infrared wavelengths reveal large variations in the abundances depending on evolutionary state. Such variations can be explained by freezing out of molecules onto grains in the cold collapse phase, followed by evaporation and high-temperature chemical reactions when the young star heats the envelope. Thus, the chemical composition can be a powerful diagnostic tool. A detailed study of a set of infrared-bright massive young stars reveals systematic increases in the gas/solid ratios and abundances of evaporated molecules with temperature. This ‘global heating’ plausibly results from the gradual dispersion of the envelopes. We argue that these objects form the earliest phase of massive star formation, before the ‘hot core’ and ultracompact H II region phase.

Type
II. Joint Discussions
Information
Highlights of Astronomy , Volume 12: Highlights of Astronomy. As presented at the XXIVth General Assembly of the IAU, 2000 , 2002 , pp. 146 - 148
Copyright
Copyright © Astronomical Society of Pacific 2002

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