2000A&A...356L..41L

We present spectro-imaging observations of DG Tau at 0.5" resolution obtained with OASIS in [O I]λ6300, Hα, [N II]λ6583, and [S II]λλ6716,6731. The fast jet core appears wiggling and surrounded by a slower moving flow or cavity. Line ratios are compared with available predictions for heating mechanisms in T Tauri jets (shocks, ambipolar diffusion, turbulent mixing-layers). Shocks with speeds 50-100km/s increasing with flow velocity, and preshock densities 10⁵-10³cm^–3 decreasing away from the star, are best able to reproduce the high level of excitation for velocities >100km/s.