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

TL;DR

This study uses high-resolution integral field spectroscopy to spatially resolve molecular hydrogen emission around six classical T Tauri stars, revealing shock excitation in their inner environments.

Contribution

First detailed spatially resolved analysis of H2 emission in T Tauri stars' inner regions using adaptive optics integral field spectroscopy.

Findings

H2 emission is spatially extended and often not coincident with continuum sources.

H2 level populations indicate thermal equilibrium at 1800-2300 K.

H2 kinematics suggest shock excitation from outflows or winds.

Abstract

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.