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AKARI near-infrared spectroscopy: Detection of H2O and CO2 ices toward young stellar objects in the Large Magellanic Cloud

Published online by Cambridge University Press:  01 July 2008

Takashi Shimonishi ,
Takashi Onaka ,
Daisuke Kato ,
Itsuki Sakon ,
Yoshifusa Ita ,
Akiko Kawamura  and
Hidehiro Kaneda
Takashi Shimonishi
Affiliation:
Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0003, Japan, email: shimonishi@astron.s.u-tokyo.ac.jp
Takashi Onaka
Affiliation:
Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0003, Japan, email: shimonishi@astron.s.u-tokyo.ac.jp
Daisuke Kato
Affiliation:
Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0003, Japan, email: shimonishi@astron.s.u-tokyo.ac.jp
Itsuki Sakon
Affiliation:
Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0003, Japan, email: shimonishi@astron.s.u-tokyo.ac.jp
Yoshifusa Ita
Affiliation:
National Astronomical Observatory of Japan, Japan
Akiko Kawamura
Affiliation:
Department of Astrophysics, Nagoya University, Japan
Hidehiro Kaneda
Affiliation:
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
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Abstract

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We present the first results of the AKARI Infrared Camera near-infrared spectroscopic survey of the Large Magellanic Cloud (LMC). The circumstellar material of young stellar objects (YSOs) are affected by galactic environments such as a metallicity or radiation field. Ices control the chemical balance of circumstellar environments of embedded YSOs. We detected absorption features of the H2O ice 3.05 μm and the CO2 ice 4.27 μm stretching mode toward seven massive YSOs in the LMC. This is the first detection of the 4.27 μm CO2 ice feature toward extragalactic YSOs. The present samples are for the first time spectroscopically confirmed to be YSOs. We used a curve-of-growth method to evaluate the column densities of the ices and derived the CO2/H2O ratio to be 0.45±0.17. This is clearly higher than that seen in Galactic massive YSOs (0.17±0.03). We suggest that the strong ultraviolet radiation field and/or the high dust temperature in the LMC may be responsible for the observed high CO2 ice abundance.

Keywords

circumstellar matterstars: pre-main-sequenceISM: moleculesgalaxies: individual (LMC)Magellanic Clouds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S256: The Magellanic System: Stars, Gas, and Galaxies , July 2008 , pp. 233 - 238
Copyright
Copyright © International Astronomical Union 2009

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