SEARCH FOR H-2 EMISSION FROM DISKS AROUND T-TAURI AND HERBIG AE STARS

Preliminary results are presented of observations of the pure rotation al lines of H-2 toward T Tauri and Herbig Ae stars using the Short Wav elength Spectrometer (SWS) on the Infrared Space Observatory (ISO). Th e sources are selected to be isolated low- and intermediate-mass young stellar objects, for which the presence of a circumstellar disk has b een established by millimeter interferometry. The lowest H-2 S(0) and S(1) lines are detected in 3 out of 5 objects. The measured intensitie s indicate similar to 0.01 M. of warm (T approximate to 150 K) gas in the ISO beam. It is argued that for at least one case (HD 163296), the emission is probably dominated by the warm gas in the circumstellar d isk rather than by shocked- or photon-heated gas in the surrounding en velope. Such observations can provide important constraints on the rad ial and vertical temperature profiles in circumstellar disks.