H₂ emission from disks aroud T Tauri stars

W.F. Thi ¹, E.F. van Dishoeck ¹, G.A. Blake ², G.J. van Zadelhoff ¹, M.R. Hogerheijde ^1,3, A.I. Sargent ², & V.G. Mannings ⁴

¹ Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands

² California Institute of Technology, Pasadena, CA 91125, USA

³ Dept. of Astronomy, University of California, Berkeley, CA 94720, USA

⁴ Jet Propulsion Laboratory, California Institute of Technology, CA 91109, USA

We have obtained deep ISO-SWS observations of the low J pure-rotational H₂ emission lines towards several T Tauri and Herbig Ae stars with circumstellar disks. We present here the results for the sources GG Tau, MWC 480 and HD 163296, for which the circumstellar disks have been imaged with millimeter interferometers. The observations suggest the presence of ``warm'' gas at a kinetic temperature K. The mass contained in this warm gas is typically a few % of the dust mass derived from the continuum data. The H₂ observations are compared with CO 1-0 and 2-1 interferometer data and with CO 3-2 and 6-5 single-dish spectra obtained with the Caltech Submillimeter Observatory (CSO). The results are interpreted using radiative transfer models of the disks, and are compared with a variety of models in the literature.