DPS 2001 meeting, November 2001
Session 23. Solar System Origins I
Oral, Chairs: G. Stewart, J. Chambers, Wednesday, November 28, 2001, 3:00-4:30pm, Regency GH

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[23.01] Chemistry in YSO accretion disks: Theory meets Observation

J.E. Kessler, G.A. Blake (Caltech), Chunhua Qi (Harvard-Smithsonian CfA), M.R. Hogerheijde (Steward Observatory, U. of Arizona), K. Willacy (JPL)

Circumstellar disks have now been found around many young stars and a significant fraction of 1-5 Myr old T Tauri stars have been shown to possess accretion disks with masses (~10-3-10-1 MSun) and sizes (~ 100AU) comparable to those inferred for the primitive solar nebula (Beckwith & Sargent 1996). Thus, models of the chemical composition at each radius of these disks will provide valuable information (i.e. density, thermal history and composition) about the initial condition of the solar nebula. In recent years, molecular emission studies of accretion disks have been shown to facilitate the quantification of gas-to-dust ratios and the timescales over which they are dissipated (important for the process of planet formation) as well as the description of the distribution of volatile species in its outer regions (necessary in the derivation of the evolution of comets and Kuiper Belt Objects). Extensive molecular modeling of the chemistry of accretion disks is clearly codependent upon the observational study of the disks through molecular line emission.

In this study, the molecular emission from four accretion disks around both low-mass TTauri stars (LkCa 15 and MWC 480) and moderate-mass Herbig Ae stars (HD 163296 and MWC 480) has been observed using the Owen's Valley Radio Observatory (OVRO) and the Caltech Submilimeter Observatory (CSO). These studies include emission from several predicted gas-phase C-,O-,S-,N-bearing molecules. The spectra obtained have been compared to those predicted through models produced via the couping of radiative transfer codes developed by Hogerheijde & van der Tak (2000) and models of circumstellar disk molecular abundances (Willacy & Langer 2000) in order to obtain optical depth and excitation information. In addition, the OVRO maps were also compared to maps produced by the model discussed above.

This work was supported by the NASA Graduate Student Researchers Program, NGT5-50231, and the National Science Foundation, AST 9981546.

The author(s) of this abstract have provided an email address for comments about the abstract: kessler@caltech.edu

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