Spectroscopic Evidence for Infall around an Extraordinary IRAS Source in Ophiuchus

IRAS 16293-2422 is an extremely cold infrared source associated with a high velocity molecular outflow in the Rho Ophiuchi molecular cloud. The authors report millimeter-wave continuum (λ ≅ 1.3 mm) observations and spectral line observations of the J = 5-4 and J = 2-1 transitions of CS in both common and rare isotopic species toward this source. These observations indicate that the source is a dust-enshrouded object embedded in a dense elongated configuration of molecular gas whose major axis is roughly orthogonal to the direction of the double bipolar outflow. Moreover, the spectral line data appear to provide spectroscopic evidence for significant mass infall motions associated with a young stellar object and suggest that IRAS 16293-2422 is a true protostar.