Spatially and Spectrally Resolved Hydrogen Gas within 0.1 AU of T Tauri and Herbig Ae/Be Stars

TL;DR

This study uses high-resolution near-infrared observations to spatially and spectrally resolve hydrogen gas in the inner regions of protoplanetary disks around young stars, revealing gas distributions and dynamics close to the star.

Contribution

It provides the first spatially and spectrally resolved measurements of hydrogen gas within 0.1 AU of T Tauri and Herbig Ae/Be stars, supporting magnetospheric accretion and outflow models.

Findings

Gaseous emission is more compact or similar in scale to dust emission.

Data favor infall/outflow models over simple disk models for gas distribution.

Presence of gas at ~0.01 AU supports magnetospheric accretion theories.

Abstract

We present near-infrared observations of T Tauri and Herbig Ae/Be stars with a spatial resolution of a few milli-arcseconds and a spectral resolution of ~2000. Our observations spatially resolve gas and dust in the inner regions of protoplanetary disks, and spectrally resolve broad-linewidth emission from the Brackett gamma transition of hydrogen gas. We use the technique of spectro-astrometry to determine centroids of different velocity components of this gaseous emission at a precision orders of magnitude better than the angular resolution. In all sources, we find the gaseous emission to be more compact than or distributed on similar spatial scales to the dust emission. We attempt to fit the data with models including both dust and Brackett gamma-emitting gas, and we consider both disk and infall/outflow morphologies for the gaseous matter. In most cases where we can distinguish between these two models, the data show a preference for infall/outflow models. In all cases, our data appear consistent with the presence of some gas at stellocentric radii of ~0.01 AU. Our findings support the hypothesis that Brackett gamma emission generally traces magnetospherically driven accretion and/or outflows in young star/disk systems.