High-resolution spectroscopy of Br gamma emission in young stellar objects

We have obtained high-resolution spectra of the Br gamma emission line in a small sample of low-luminosity embedded young stellar objects (YSOs) and active T Tauri stars. We find line profiles whih possess broad wings (400-700 km s(-1) FWZI) but which conspicuously lack the blueshifted absorption components generally expected for emission from a wind. Even T Tauri stars that show strong wind absorption features in the H alpha and Na D lines show no obvious evidence of a wind origin for the Br gamma line. These results imply that the winds in these YSOs are likely cooler than previously estimated and that mass-loss rates derived from Br gamma line strengths require reexamination. We also find a tendency for the centroid of the emission to be blueshifted with respect to the stellar velocity, as is often observed in the higher Balmer lines of T Tauri stars. This tendency is generally consistent with emission from infalling rather than outflowing gas. We discuss the physical origin of the infalling gas and the origin of the broad line wings.