H_2 Mid-IR Pure Rotational Emission from Young Stars: The TEXES/IRTF Survey

Abstract

We describe the TEXES survey for mid-IR H_2 pure rotational emission from young stars and report early successes. H_2 emission is a potential tracer of warm gas in circumstellar disks. Three pure rotational lines are available from the ground: the J=3 ⇒ 1, J=4 ⇒ 2, and J=6 ⇒ 4, transitions at 17.035 μm, 12.279 μm, and 8.025 μm, respectively. Using TEXES at the NASA IRTF 3m, we are midway through a survey of roughly 30 pre-main-sequence stars. To date, detected lines are all resolved, generally with FWHM<10 km/s. Preliminary analysis suggests the gas temperatures are between 400 and 800 K. From the work so far, we conclude that high spectral and spatial resolution are critical to the investigation of H_2 in disks.