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 Tau and AS 209 also exhibit double-peaked spectra characteristic of a rotating disk. Line emission from DO Tau is dominated by high-velocity blueshifted 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.