Year: 2009
Type: article
Abstract: We present spectroscopic observations of a sample of 15 embedded young stellar objects (YSOs) in the Large Magellanic Cloud (LMC). These observations were obtained with the Spitzer Infrared Spectrograph (IRS) as part of the SAGE-Spec Legacy program. We analyze the two prominent ice bands in the IRS spectral range: the bending mode of CO 2 ice at 15.2 μm and the ice band between 5 and 7 μm that includes contributions from the bending mode of water ice at 6 μm among other ice species. The 5–7 μm band is difficult to identify in our LMC sample due to the conspicuous presence of polycyclic aromatic hydrocarbon emission superimposed onto the ice spectra. We identify water ice in the spectra of two sources; the spectrum of one of those sources also exhibits the 6.8 μm ice feature attributed in the literature to ammonium and methanol. We model the CO 2 band in detail, using the combination of laboratory ice profiles available in the literature. We find that a significant fraction (≳50%) of CO 2 ice is locked in a water-rich component, consistent with what is observed for Galactic sources. The majority of the sources in the LMC also require a pure-CO 2 contribution to the ice profile, evidence of thermal processing. There is a suggestion that CO 2 production might be enhanced in the LMC, but the size of the available sample precludes firmer conclusions. We place our results in the context of the star formation environment in the LMC.
Source: The Astrophysical Journal
Authors: J. M. Oliveira, J. Th. van Loon, C.-H. R. Chen, A. G. G. M. Tielens, G. C. Sloan, P. M. Woods, F. Kemper, R. Indebetouw, K. D. Gordon, M. L. Boyer, B. Shiao, S. Madden, A. K. Speck, M. Meixner, M. Marengo
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1968782641