2004A&A...416..213T

We detect near-infrared H₂ emission in DG Tau using the Infrared Camera and Spectrograph (IRCS) on the 8.2-m SUBARU telescope. The spectra obtained along the jet axis show that the centroidal position of the 1-0S(1) emission is offset by 0.2'' from the star towards the jet, while those obtained perpendicular to the jet axis show a marginal extension, indicating that the emission line region has a typical width of ∼0.6''. Their line profiles show a peak velocity of ∼15km/s blueshifted from the systemic velocity. These results indicate that the emission originates from a warm molecular wind with a flow length and width of ∼40 and ∼80AU, respectively. The line flux ratios (I_1–0S(0)/I_1–0S(1) and an upper limit for I_2–1S(1)/I_1–0S(1)) suggest that the flow is thermalized at a temperature of ∼2000K, and is likely heated by shocks or ambipolar diffusion. The observed velocity and spatial extension suggest that the H₂ and forbidden line emission originate from different components of the same flow, i.e., a fast and partially ionised component near the axis and a slow molecular component surrounding it. Such a flow geometry agrees with model predictions of magneto-centrifugal driven winds.