A wealth of evidence has accumulated over the last decade or so proving
the existence of massive disks of dust and gas around some pre-main
sequence stars. However, the innermost regions of these disks, where
material accretes from the disk onto the star, remain poorly studied due
to the lack of high-angular resolution observations. Over the past several
years, I have been observing T Tauri and Herbig Ae/Be stars at milliarcsecond
resolution using near infrared interferometers. This work has helped
to elucidate the basic structure of inner disk regions.
In 2006 we commissioned a grism with a resolving power of 240 at the
Keck Interferometer and used it to constrain gas, as well, as dust around
young stars
(Eisner 2007); this work was also described in
this article.
A sketch of the inner disk regions from van Boekel (2007), intended to describe the observational data in Eisner (2007).
We have recently commissioned a grism with an order of magnitude higher dispersion, and are currently using it to spectrally and spatially resolve gaseous emission features at sub-AU radii around young stars. In a recent paper, we observed emission from hydrogen on scales smaller than 0.01 AU; these data provide direct constraints on the process by which gas is accretied onto the central stars (Eisner et al. 2010).
In addition to high spatial resolution, we probe inner disk gas using high dispersion spectroscopy. Spectra constrain gas compoasition and kinematics, while time-monitoring elucidates variable disk structure or accretion processes.