Spectroscopic evidence of mass infall towards an embedded infrared source in the globule DC303.8-14.2

We present millimeter molecular line observations towards the embedded infrared source IRAS 13036-7644, located in the globule DC 303.8-14.2. The CS(J=2–1) lines show asymmetrical profiles characteristic of a cloud undergoing gravitational collapse, i.e. double-peaked profiles with a brighter blue-shifted component. In contrast the HCO+(J=1–0) line shows towards the IRAS source a double-peaked profile with a brighter red-shifted component, and a velocity gradient across the cloud. The hyperfine components of HCN(J=1–0) transition show both kinds of double-peaked profiles, and a velocity gradient. We interpret these results as a simultaneous infall of the dense gas in the core and a non-collapsing envelope. The IRAS source drives a bipolar molecular outflow detected in the 12CO(J=1–0) transition.