Sub-arcsecond [ FeII ] spectro-imaging of the DG Tau jet : Periodic bubbles and a dusty disk wind ?

s of recently accepted papers Sub-arcsecond [FeII] spectro-imaging of the DG Tau jet: Periodic bubbles and a dusty disk wind? V. Agra-Amboage, C. Dougados, S. Cabrit and J. Reunanen 1 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, F-38041, France 2 LERMA, Observatoire de Paris, UMR 8112 du CNRS, 61 Avenue de l’Observatoire, 75014 Paris, France 3 Tuorla Observatory, Dept. of Physics and Astronomy, University of Turku, Vaisalantie 20, 21500 Piikkio, Finland E-mail contact: vaa at fe.up.pt Context: The origin of protostellar jets as well as their impact on the regulation of angular momentum and the inner disk physics are still crucial open questions in star formation. Aims: We aim to test the different proposed ejection processes in T Tauri stars through high-angular resolution observations of forbidden-line emission from the inner DG Tauri microjet. Methods: We present spectro-imaging observations of the DG Tauri jet obtained with SINFONI/VLT in the lines of [Fe ii]λ1.64 μm, 1.53μm with 0. 15 angular resolution and R=3000 spectral resolution. We analyze the morphology and kinematics, derive electronic densities and mass-flux rates and discuss the implications for proposed jet launching models. Results: (1) We observe an onion-like velocity structure in [Fe ii] in the blueshifted jet, similar to that observed in optical lines. High-velocity (HV) gas at ≃ -200 km s is collimated inside a half-opening angle of 4 and mediumvelocity (MV) gas at ≃ -100 km sin a cone with an half-opening angle 14. (2) Two new axial jet knots are detected in the blue jet, as well as a more distant bubble with corresponding counter-bubble. The periodic knot ejection timescale is revised downward to 2.5 yrs. (3) The redshifted jet is detected only beyond 0. 7 from the star, yielding revised constraints on the disk surface density. (4) From comparison to [O i] data we infer iron depletion of a factor 3 at high velocities and a factor 10 at speeds below -100 km s. (5) The mass-fluxes in each of the medium and high-velocity components of the blueshifted lobe are ≃ 1.6 ± 0.8 × 10 M⊙ yr , representing 0.02–0.2 of the disk accretion rate. Conclusions: The medium-velocity conical [Fe ii] flow in the DG Tau jet is too fast and too narrow to trace photoevaporated matter from the disk atmosphere. Both its kinematics and collimation cannot be reproduced by the X-wind, nor can the ”conical magnetospheric wind”. The level of Fe gas phase depletion in the DG Tau mediumvelocity component also rules out a stellar wind and a cocoon ejected sideways from the high-velocity beam. A quasi-steady centrifugal MHD disk wind ejected over 0.25–1.5 AU and/or episodic magnetic tower cavities launched from the disk appear as the most plausible origins for the [Fe ii] medium velocity component in the DG Tau jet. The same disk wind model can also account for the properties of the high-velocity [Fe ii] flow, although alternative origins in magnetospheric and/or stellar winds cannot be excluded for this component. Accepted by A&A The First X-shooter Observations of Jets from Young Stars Francesca Bacciotti, Emma T. Whelan, Juan M. Alcalà, Brunella Nisini, Linda Podio, Sofia Randich, Beate Stelzer and Guido Cupani 1 INAF Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 2 Laboratoire d’Astrophysique de l’Observatoire de Grenoble, UMR 5521 du CNRS, 38041 Grenoble Cedex, France