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Evidence for chemical processing of precometary icy grains in circumstellar environments of pre-main-sequence stars

Tegler, Stephen C. and Weintraub, David A. and Rettig, Terrence W. and Pendleton, Yvonne J. and Whittet, Douglas C. B. and Kulesa, Craig A. (1995) Evidence for chemical processing of precometary icy grains in circumstellar environments of pre-main-sequence stars. The Astrophysical Journal, 439 (1). pp. 279-287. ISSN 1538-4357

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Publisher’s or external URL: http://dx.doi.org/10.1086/175171

Abstract

We report the detection of a broad absorption feature near 2166/cm in the spectrum of the Taurus cloud cource Elias 18. This pre-main-sequence source is the second in Taurus, the third in our survey, and the fifth known in the sky to show the broad 2166/cm absorption feature. Of equal importance, this feature is not seen toward several other embedded sources in our survey, nor is it seen toward the source Elias 16, located behind the Taurus cloud. Laboratory experiments with interstellar ice analogs show that such a feature is associated with a complex C triple bonded to N containing compound (called X(C triple bonded to N)) that results from high-energy processing (ultraviolet irradiation or ion bombardment) of simple ice components into more complex, organic components. We find a nonlinear anticorrelation between the abundance of X(C triple bonded to N) and frozen CO components in nonpolar lattices. We find no correlation between the abundance of X(C triple bonded to N) and frozen CO in polar lattices. Because the abundances of frozen CO and H2O are strongly correlated with each other and with visual extinction toward sources embedded in and located behind the Taurus molecular cloud, these ice components usually are associated with intracloud material. Our results indicate that X(C triple bonded to N) molecules result from chemical processing of dust grains dominated by nonpolar icy mantles in the local environments of pre-main-sequence stars. Such processing of icy grains in the early solar system may be an important source of organic compounds observed in minor solar system bodies. The delivery of these organic compounds to the surface of the primitive Earth through comet impacts may have provided the raw materials for prebiotic chemistry.

Item Type: Article
Publisher’s Statement: © 1995 The American Astronomical Society. Published in The Astrophysical Journal.
ID number or DOI: 10.1086/175171
Keywords: Absorption spectra; abundance; carbon monoxide; chemical reactions; infrared spectra; organic compounds; Pre-Main Sequence Stars; spectrum analysis; statistical analysis; Stellar Envelopes
Subjects: Q Science > QB Astronomy
NAU Depositing Author Academic Status: Faculty/Staff
Department/Unit: College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited: 21 Dec 2015 17:11
URI: http://openknowledge.nau.edu/id/eprint/1848

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