Spatially Resolved Molecular Hydrogen Emission in the Inner 200 AU Environments of Classical T Tauri Stars

Abstract

We present 2.0-2.4 μm integral field spectroscopy at adaptive optics spatial resolution (~0.1 -->'') obtained with the Near-infrared Integral Field Spectrograph (NIFS) at Gemini North Observatory of six classical T Tauri stars: T Tau, DG Tau, XZ Tau, HL Tau, RW Aur, and HV Tau C. In all cases, the -->v = 1–0 S(1) (2.12 μm) emission is detected at spatially extended distances from the central stars. Moreover, HL Tau, T Tau, RW Aur, and HV Tau C have H2 that extends to projected distances of more than ~200 AU from the stars. Integrated over the IFU field, most of the H2 emission is not spatially coincident with the location of continuum flux. Multiple H2 transitions detected in the K-band spectra show that level populations are typical of gas in thermal equilibrium with excitation temperatures in the 1800-2300 K range. Three of the stars have H2 velocity profiles that are centered approximately at the stellar radial velocity, and three show velocity shifts with respect to the system. Each of the stars studied here exhibit H2 morphologies, spatial extents, excitation temperatures, and kinematics that are most consistent with shock-excited emission from the inner regions of the known Herbig-Haro energy flows or from spatially extended wide-angle winds encompassing the outflows rather than predominantly from H2 stimulated quiescently by UV or X-ray emission from the central stars. The data presented in this study highlights the sensitivity of adaptive-optics-fed integral field spectroscopy for spatially resolving emission line structures in the environments of bright young stars.