1997A&A...327..671L

We present the first 3D spectro-imaging observations of the [O I]λ6300 line in an active T Tauri star: DG Tau. The morphological structure of the mass outflow is revealed with unprecedented spatial resolution (0.35''). It consists of an unresolved inner peak containing two thirds of the total line flux, followed by a collimated jet-like body extending out to ∼1.5" from the star, and two resolved knots at distances of 2.7" and 4''. One of the outer knots possesses a curved morphology and transverse velocity gradient strongly suggestive of a resolved bowshock. Time variability in the ejection velocity (with timescale {DELTA}t≃8.5yr) could explain the presence of such a bowshock, the spacing of knots at distances ≥1'' from the star, and the strong velocity gradients along the jet observed closer to the star. The unresolved inner peak, centered at ∼20AU of the star, is apparently stationary and possibly linked to the initial jet collimation. Our size limit and absolute photometry for this peak set new constraints on the jet mass loss rate (between 1.3x10^–8 and 6.5x10^–6M_☉/yr), lowering previous estimates by a factor 5 to 25. Finally, our high sensitivity combined with velocity information allows us to detect unambiguously the counterjet of the system (v≃+230km/s), and to establish the existence of a diffuse halo of low-velocity [O I] emission, which might trace a wider flow or an extended scattering nebula.