Detection of a warm molecular wind in DG Tauri

We detect near-infrared H-2 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 1-0 S(l) 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 similar to0.6. Their line profiles show a peak velocity of similar to15 km s(-1) blueshifted from the systemic velocity. These results indicate that the emission originates from a warm molecular wind with a flow length and width of similar to40 and similar to80 AU, respectively. The line flux ratios (I1-0S(0)/I1-0S(1) and an upper limit for I2-1S(1)/I1-0S(1)) suggest that the flow is thermalized at a temperature of similar to2000 K, and is likely heated by shocks or ambipolar diffusion. The observed velocity and spatial extension suggest that the H-2 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.