van Dishoeck, Ewine F. and Blake, Geoffrey A. (1998) Chemical evolution of star-forming regions. Annual Review of Astronomy and Astrophysics, 36 . pp. 317-368. ISSN 0066-4146. http://resolver.caltech.edu/CaltechAUTHORS:20111214-110050597
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Recent advances in the understanding of the chemical processes that occur during all stages of the formation of stars, from the collapse of molecular clouds to the assemblage of icy planetesimals in protoplanetary accretion disks, are reviewed. Observational studies of the circumstellar material within 100–10,000 AU of the young star with (sub)millimeter single-dish telescopes, millimeter interferometers, and ground-based as well as space-borne infrared observatories have only become possible within the past few years. Results are compared with detailed chemical models that emphasize the coupling of gas-phase and grain-surface chemistry. Molecules that are particularly sensitive to different routes of formation and that may be useful in distinguishing between a variety of environments and histories are outlined. In the cold, low-density prestellar cores, radicals and long unsaturated carbon chains are enhanced. During the cold collapse phase, most species freeze out onto the grains in the high-density inner region. Once young stars ignite, their surroundings are heated through radiation and/or shocks, whereupon new chemical characteristics appear. Evaporation of ices drives a “hot core” chemistry rich in organic molecules, whereas shocks propagating through the dense envelope release both refractory and volatile grain material, resulting in prominent SiO, OH, and H_2O emission. The role of future instrumentation in further developing these chemical and temporal diagnostics is discussed.
|Additional Information:||© 1998 by Annual Reviews. The authors are grateful to all their astrochemical colleagues for sending preprints and reprints of their work and to the dedicated staff at telescopes around the world for making the observations possible. They thank JH Black, P Ehrenfreund, E Herbst, TJ Millar, WA Schutte, AGGM Tielens, and CM Walmsley for many stimulating discussions and comments on the manuscript. Astrochemistry in Leiden is supported by grant 781-76-015 from the Netherlands Foundation for Research in Astronomy and at Caltech by the National Science Foundation, grant AST96-13717, and the National Aeronautics and Space Administration Origins of Solar Systems and Exobiology Programs (grants NAG5-4383 and 3733).|
|Subject Keywords:||interstellar medium; astrochemistry; interstellar molecules; star formation; molecular processes|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||14 Dec 2011 19:38|
|Last Modified:||14 Dec 2011 19:38|
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