Rotation of Jets from Young Stars: New Clues from theHubble Space TelescopeImaging Spectrograph

We report findings from the first set of data in a current survey toestablish conclusively whether jets from young stars rotate. We observed thebi-polar jets from the T Tauri stars TH28 and RW Aur, and the blue-shifted jetfrom T Tauri star LkH$\alpha$321, using the Hubble Space Telescope ImagingSpectrograph (HST/STIS). Forbidden emission lines (FELs) show distinct andsystematic velocity asymmetries of 10 -- 25 (+/- 5) km/s at a distance of 0".3from the source, representing a (projected) distance of ~ 40 AU along the jetin the case of RW Aur, ~ 50 AU for TH28, and 165 AU in the case ofLkH$\alpha$321. These velocity asymmetries are interpreted as rotation in theinitial portion of the jet where it is accelerated and collimated. For thebi-polar jets, both lobes appear to rotate in the same direction. Valuesobtained were in agreement with the predictions of MHD disk-wind models(Bacciotti et al 2002, Anderson et al 2003, Dougados et al 2003, Pesenti et al2003). Finally, we determine, from derived toroidal and poloidal velocities,values for the distance from the central axis of the footpoint for the jet'slow velocity component of ~ 0.5 - 2 AU, consistent with the models ofmagneto-centrifugal launching (Anderson et al 2003).Comment: 17 pages, 10 figures, Accepted by Ap