Virtual Versus Real Jets: New Clues from the Hubble Space Telescope

During past years high angular (<1″) resolution imaging has provided useful information about the propagation of "real" jets. Recently, in addition, the spectrograph Hubble's Space Telescope Imaging spectrograph (STIS) on board the Hubble Space Telescope (HST) has finally allowed us to test the magneto-centrifugal paradigm for the jet launching. I present results from HST/STIS spectra at 0.″1 resolution of small-scale jets from T Tauri stars in their initial 140 AU (1″). The jet morphology, kinematics and excitation in different velocity intervals are derived, from which we calculate mass and momentum fluxes. Even more interestingly, we find indications for rotation around the symmetry axis in the peripheral regions of the flow. The investigated component of the wind appears to originate in the disk at a distance of 0.5-2 AU from the star, and it extracts at least 60% of the inner disk angular momentum. These results confirm for the first time the validity of the magneto-centrifugal approach for the jet launching, and constitute a benchmark to test models and simulations. In the near future, near-infrared (NIR) interferometry with AMBER/VLTI and with the LBTI will permit to observe the jet engine down to 0.1 AU from the source, where the acceleration of the jet takes place.