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

Abstract

We present 2.0Y2.4 m integral field spectroscopy at adaptive optics spatial resolution (~0.1 00 ) 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 ¼ 1Y 0 S(1) (2.12 m) emission is detected at spatially extended distances from the central stars. Moreover, HL Tau, T Tau, RWAur, and HV Tau C have H 2 that extends to projected distances of more than~200 AU from the stars. Integrated over the IFU field, most of the H 2 emission is not spatially coincident with the location of continuum flux. Multiple H 2 transitions detected in the K-band spectra show that level populations are typical of gas in thermal equilibrium with excitation temperatures in the 1800Y 2300 K range. Three of the stars have H 2 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 H 2 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 H 2 stimulated quiescently by UV or X-ray emission from the central stars. The data presented in this study highlights the sensitivity of adaptive-opticsYfed integral field spectroscopy for spatially resolving emission line structures in the environments of bright young stars.

Spatially resolved H2emission from a very low-mass star

“…The reported gas temperatures and excitation properties of IRS54 are consistent with shock-heated material, as well. Similar values have also been found in low-mass Class I sources and CTTSs (Beck et al 2008;Davis et al 2011). The overall outflow structure can be interpreted as the sum of H 2 emission excited along a wide-angle cavity, plus the contribution from a jetlike structure.…”

“…In general, MHEL properties are consistent with shockheated gas from the inner regions of Herbig-Haro objects or from spatially extended wide-angle winds (Davis et al 2001;Caratti o Garatti et al 2006;Beck et al 2008;Davis et al 2011). The reported gas temperatures and excitation properties of IRS54 are consistent with shock-heated material, as well.…”

Origin of the wide-angle hot H2in DG Tauri

“…This work complements our detailed study of the atomic flow component and accretion rate in DG Tau based on [Fe II] lines in H-band and Brγ in K-band, observed at the same epoch with the same instrument (Agra-Amboage et al 2011, hereafter Paper I). Our analysis improves on that in Beck et al (2008) in several ways: We apply spatial deconvolution to obtain a sharper view of the brightness distribution, and perform careful correction for wavelength calibration and unevenslit illumination to retrieve radial velocities along and across the jet axis down to a precision of a few km s −1 . This allows us to conduct a detailed comparison with the spatio-kinematic structure of the atomic flow component and FUV H 2 emission in DG Tau, and to constrain both the proper motion and the 3D velocity field of warm H 2 , including rotation.…”

“…In particular, long-slit spectra of DG Tau provide evidence of a warm H 2 outflow at -20 km s −1 , shifted by 30 AU along the blue jet direction and with an estimated width 80 AU (Takami et al 2004;Schneider et al 2013b). Beck et al (2008) conducted a 2D spectro-imaging study of H 2 rovibrational lines in six CTTs known to be associated with large scale atomic jets, including DG Tau, and found spatially extended emission in all cases, with sizes up to 200 AU. While the data are not flux calibrated, relative level populations among K-band H 2 lines indicate excitation temperatures in the range 1800-2300 K. From various arguments, Takami et al (2004) and Beck et al (2008) argue that the H 2 properties are in general not well explained by FUV or X-ray irradiation and are most consistent with shock-excited emission from the inner regions of the atomic jets or from wider-angle winds encompassing these flows.…”

“…Beck et al (2008) conducted a 2D spectro-imaging study of H 2 rovibrational lines in six CTTs known to be associated with large scale atomic jets, including DG Tau, and found spatially extended emission in all cases, with sizes up to 200 AU. While the data are not flux calibrated, relative level populations among K-band H 2 lines indicate excitation temperatures in the range 1800-2300 K. From various arguments, Takami et al (2004) and Beck et al (2008) argue that the H 2 properties are in general not well explained by FUV or X-ray irradiation and are most consistent with shock-excited emission from the inner regions of the atomic jets or from wider-angle winds encompassing these flows. Takami et al (2004) also mention ambipolar diffusion on the outer molecular streamlines of an MHD disc wind as an alternative heating mechanism for the warm H 2 outflow in DG Tau.…”