Document Type

Article

Publication Date

7-1-2006

Publication Title

The Astrophyical Journal

Volume

646

Issue

1

Publisher

The American Astronomical Society

Abstract

We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S, RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO, and C18O, as well as broad emission lines of gas-phase 12CO. The narrow absorption lines of CO are shown to originate from the colder circumstellar gas. We find that the line-of-sight gas column densities resulting from the CO absorption lines are much higher than expected for the measured extinction for each source and suggest the gas/dust ratio is measuring the dust settling and/or grain coagulation in these extended disks. We provide a model of turbulence, dust settling, and grain growth to explain the results.

Comments

This article 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/0004-637X/646/1/342

The American Astronomical Society holds the copyright in this article.

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