We present high spatial resolution maps of ro-vibrational molecular hydrogen emission from the environment of the GG Tau A binary component in the GG Tau quadruple system. The H2 v= 1-0 S(1) emission is spatially resolved and encompasses the inner bi
nary, with emission detected at locations that should be dynamically cleared on several hundred-year timescales. Extensions of H2 gas emission are seen to ~100 AU distances from the central stars. The v = 2-1 S(1) emission at 2.24 microns is also detected at ~30 AU from the central stars, with a line ratio of 0.05 +/- 0.01 with respect to the v = 1-0 S(1) emission. Assuming gas in LTE, this ratio corresponds to an emission environment at ~1700 K. We estimate that this temperature is too high for quiescent gas heated by X-ray or UV emission from the central stars. Surprisingly, we find that the brightest region of H2 emission arises from a spatial location that is exactly coincident with a recently revealed dust streamer which seems to be transferring material from the outer circumbinary ring around GG Tau A into the inner region. As a result, we identify a new excitation mechanism for ro-vibrational H2 stimulation in the environment of young stars. The H2 in the GG Tau A system appears to be stimulated by mass accretion infall as material in the circumbinary ring accretes onto the system to replenish the inner circumstellar disks. We postulate that H2 stimulated by accretion infall could be present in other systems, particularly binaries and transition disk systems which have dust cleared gaps in their circumstellar environments.
The majority of atomic hydrogen Br{gamma} emission detected in the spectra of young stellar objects (YSOs) is believed to arise from the recombination regions associated with the magnetospheric accretion of circumstellar disk material onto the formin
g star. In this paper, we present the results of a K-band IFU spectroscopic study of Br{gamma} emission in eight young protostars: CW Tau, DG Tau, Haro 6-10, HL Tau, HV Tau C, RW Aur, T Tau and XZ Tau. We spatially resolve Br{gamma} emission structures in half of these young stars and find that most of the extended emission is consistent with the location and velocities of the known Herbig-Haro flows associated with these systems. At some velocities through the Br{gamma} line profile, the spatially extended emission comprises 20% or more of the integrated flux in that spectral channel. However, the total spatially extended Br{gamma} is typically less than ~10% of the flux integrated over the full emission profile. For DG Tau and Haro 6-10 S, we estimate the mass outflow rate using simple assumptions about the hydrogen emission region, and compare this to the derived mass accretion rate. We detect extended Br{gamma} in the vicinity of the more obscured targets in our sample and conclude that spatially extended Br{gamma} emission may exist toward other stars, but unattenuated photospheric flux probably limits its detectability.
We present 2.0-2.4micron 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 micron) emission is detected at spatially extended distances from the central stars. The bulk of the H_2 emission is typically not spatially coincident with the location of continuum flux. Multiple transitions detected in the K-band spectra show that H_2 level populations are typical of gas in thermal equilibrium with excitation temperatures in the 1800K-2300 K range. Three of the stars have H_2 velocity profiles that are centered at the stellar radial velocity, and three show velocity shifts with respect to the system. Each of the stars studied here show observed excitation temperatures, spatial extents, and kinematics of the H_2 that are most consistent with shock excited emission from the inner regions of the known Herbig-Haro energy flows or from wide-angle winds encompassing the outflows rather than predominantly from UV or X-ray stimulated 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.
