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

Stephen C Tegler, David A. Weintraub, Terrence W. Rettig, Yvonne J. Pendleton, Douglas C B Whittet, Craig A. Kulesa

Research output: Contribution to journalArticle

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Abstract

We report the detection of a broad absorption feature near 2166 cm-1 in the spectrum of the Taurus cloud source 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-1 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≡N containing compound [called X(C≡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≡N) and frozen CO in non-polar lattices. We find no correlation between the abundance of X(C≡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≡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.

Original languageEnglish (US)
Pages (from-to)279-287
Number of pages9
JournalAstrophysical Journal
Volume439
Issue number1
StatePublished - Jan 20 1995
Externally publishedYes

Fingerprint

pre-main sequence stars
ice
solar system
organic compound
organic compounds
comet
irradiation
extinction
dust
mantle
ion
comets
molecular clouds
energy
sky
chemical
bombardment
delivery
Earth mantle
chemistry

Keywords

  • Circumstellar matter
  • Dust, extinction
  • Infrared: stars
  • ISM: individual (Taurus Dark Cloud)
  • ISM: molecules
  • Stars: pre-main-sequence

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Tegler, S. C., Weintraub, D. A., Rettig, T. W., Pendleton, Y. J., Whittet, D. C. B., & Kulesa, C. A. (1995). Evidence for chemical processing of precometary icy grains in circumstellar environments of pre-main-sequence stars. Astrophysical Journal, 439(1), 279-287.

Evidence for chemical processing of precometary icy grains in circumstellar environments of pre-main-sequence stars. / Tegler, Stephen C; Weintraub, David A.; Rettig, Terrence W.; Pendleton, Yvonne J.; Whittet, Douglas C B; Kulesa, Craig A.

In: Astrophysical Journal, Vol. 439, No. 1, 20.01.1995, p. 279-287.

Research output: Contribution to journalArticle

Tegler, SC, Weintraub, DA, Rettig, TW, Pendleton, YJ, Whittet, DCB & Kulesa, CA 1995, 'Evidence for chemical processing of precometary icy grains in circumstellar environments of pre-main-sequence stars', Astrophysical Journal, vol. 439, no. 1, pp. 279-287.
Tegler, Stephen C ; Weintraub, David A. ; Rettig, Terrence W. ; Pendleton, Yvonne J. ; Whittet, Douglas C B ; Kulesa, Craig A. / Evidence for chemical processing of precometary icy grains in circumstellar environments of pre-main-sequence stars. In: Astrophysical Journal. 1995 ; Vol. 439, No. 1. pp. 279-287.
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N2 - We report the detection of a broad absorption feature near 2166 cm-1 in the spectrum of the Taurus cloud source 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-1 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≡N containing compound [called X(C≡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≡N) and frozen CO in non-polar lattices. We find no correlation between the abundance of X(C≡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≡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.

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