INFRARED CO EMISSION FROM YOUNG STARS - HIGH-RESOLUTION SPECTROSCOPY

We have detected the high-density, high-temperature, neutral material within 10-200 R. of five young stars through high-resolution (20-40 km s-1) spectroscopy of the first overtone bands of CO at 2.3 mum. We fi nd a remarkable diversity in the band head profiles toward these sourc es, ranging from distinctly double-peaked (DG Tau), through broad bump s with emission extending up to 200 km s-1 from the stellar velocity ( WL 16, NGC 2024 IRS 2, and S106 IRS 4), to narrow lines having a FWHM velocity of approximately 50 km s-1 (SVS 13). Both the profiles and th e fluxes of WL 16, NGC 2024 and S106 can be fitted by emission from Ke plerian accretion disks. DG Tau is well described by the superposition of emission from a Keplerian accretion disk and the diluted photosphe ric absorption features of an MO dwarf. SVS 13 requires either a disk rotating at velocities slower than Keplerian, or a nearly face-on Kepl erian disk plus an additional, broad velocity component, possibly the acceleration region of a neutral disk wind.