OD and the origin of water in protostellar cores

Principal Investigator

Paola Caselli

Proposal ID

06_0179

Category

ISM_AND_CIRCUMSTELLAR_MATTER

Keywords

• CHEMICAL ABUNDANCES
• YOUNG STARS AND PROTOSTELLAR OBJECTS
• SPECTROSCOPY
• ABSORPTION LINES

Abstract

We propose to observe with SOFIA the ground-state rotational lines of OD at 1.39 THz ( 216 micron) and of OH at 2.514 THz (119 micron) towards low-mass and intermediate-mass protostars with massive, cool envelopes. The lines are predicted to be detected in absorption against the strong far-infrared continuum from the central source. The OD data will be combined with HDO observations, with the goal of disentangling grain-surface and gas-phase production pathways of OH and H2O, which form in similar reactions as OD and HDO. Water and the hydroxyl radical are at the heart of the oxygen chemistry, and important for the production of complex organic molecules. Our chemistry model predicts that the OD/HDO abundance ratio obtains much smaller values on grain-surfaces than in the gas-phase. Therefore, the OD/HDO and OD/OH ratios can be used to infer the origin of OH and H2O detected in protostellar envelopes, i.e. whether they are primarily produced by gas-phase chemistry or by desorption from the icy mantles of grains.