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Modeling CO, CO2 and H2O Ice Abundances in the Envelopes of Young Stellar Objects in the Magellanic Clouds

Published online by Cambridge University Press:  04 September 2018

Tyler Pauly Open the ORCID record for Tyler Pauly [Opens in a new window]  and
Robin T. Garrod
Tyler Pauly
Affiliation:
Cornell Center for Astrophysics and Planetary Science and Department of Astronomy, Cornell University, Ithaca, NY 14853, USA email: tap74@cornell.edu
Robin T. Garrod
Affiliation:
Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, VA 22904-4319, USA
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Abstract

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Massive young stellar objects (MYSOs) in the Magellanic Clouds (MCs) show infrared absorption features corresponding to significant abundances of CO, CO2 and H2O ice along the line of sight, with the relative abundances of these ices varying between sources in the Magellanic Clouds and the Milky Way. We use our gas-grain chemical code MAGICKAL, with multiple grain sizes and grain temperatures, and further expand it with a treatment for increased interstellar radiation field intensity to model the elevated dust temperatures observed in the MCs. We also adjust the elemental abundances used in the chemical models, guided by observations of HII regions in these metal-poor satellite galaxies. With a grid of models, we are able to reproduce the relative ice fractions observed in MC MYSOs, indicating that metal depletion and elevated grain temperature are important drivers of the MYSO envelope ice composition. The observed shortfall in CO in the Small Magellanic Cloud can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances.

Keywords

astrochemistry—ISM: abundances—ISM: molecules—Magellanic Clouds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S332: Astrochemistry VII: Through the Cosmos from Galaxies to Planets , March 2017 , pp. 47 - 53
Copyright
Copyright © International Astronomical Union 2018 

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