Document Type

Article

Publication Date

7-1-2004

Publication Title

The Astrophysical Journal

Volume

610

Issue

2

Publisher

The American Astronomical Society

Abstract

We used high-resolution infrared spectra of the heavily embedded T Tauri star HL Tau to search for evidence of absorption due to the R0, R1, and R2 gas-phase CH4 ν3 lines near 3.3 μm. From this, we report a 3 σ upper limit of 1.3 × 1015 cm-2 for the CH4 gas column density toward HL Tau. Our results are compared to those found for CO gas toward this source and to the recent model for chemistry in the inner (10 AU) disks around T Tauri stars by Markwick et al. We find that the upper limit of methane ice+gas column density toward HL Tau, when compared to CO, is somewhat lower than but consistent with that measured toward other interstellar sources (~1%) but that it is much lower than that predicted in the Markwick et al. model and much less than the CH4/CO ratio (10%-80%) found in cometary volatiles. This has important implications for the processing of interstellar material and its incorporation into planetary bodies.

Comments

This manuscript has been published in the Astrophysical Journal. Please find the published version here (note that a subscription may be necessary to access this version):

http://iopscience.iop.org/1538-4357/610/2/L113

The American Astronomical Society holds the copyright in this article.

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