Imaging the Small-Scale Circumstellar Gas Around T Tauri Stars

We have detected circumstellar molecular gas around a small sample of T Tauri stars through aperture synthesis imaging of CO(2→1) emission at ∼2"-3" resolution. RY Tauri, DL Tauri, DO Tauri, and AS 209 show resolved and elongated gaseous emission. For RY Tau, the deconvolved, half-maximum radius along the direction of elongation, P.A. ∼48°, is 110 AU. Corresponding radii and orientations for the other sources are: DL Tau-250 AU at P.A. ∼84°; DO Tau-350 AU at P.A. ∼160°; AS 209-290 AU at P.A. ∼138°. RY Tau, DL Tau, and AS 209 show velocity gradients parallel to the elongation, suggesting that the circumstellar material is rotating. RY Tan and AS 209 also exhibit double-peaked spectra characteristic of a rotating disk. Line emission from DO Tan is dominated by high-velocity blue shifted gas which complicates the interpretation. Nevertheless, there is in each case sufficient evidence to speculate that the circumstellar emission may arise from a protoplanetary disk similar to that from which our solar system formed.