Published in

Hans Publishers, Astronomy & Astrophysics, (528), p. L13

DOI: 10.1051/0004-6361/201016402

Links

Tools

Export citation

Search in Google Scholar

The puzzling deuteration of methanol in low-to high-mass protostars

Journal article published in 2011 by A. Ratajczak, V. Taquet, C. Kahane, C. Ceccarelli, A. Faure, E. Quirico ORCID
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

Full text: Download

Red circle
Preprint: archiving forbidden
Red circle
Postprint: archiving forbidden
Red circle
Published version: archiving forbidden
Data provided by SHERPA/RoMEO

Abstract

Context. The current theory of methanol deuteration on interstellar grains predicts that the abundance ratio of the singly deuterated isotopologues [CH 2 DOH]/[CH 3 OD] should always be ∼3. In warm regions where grain mantles have sublimated, gaseous methanol is detectable via its rotational transitions. In previous observational studies, the gas-phase [CH 2 DOH]/[CH 3 OD] ratio was measured and found to be significantly larger than 3 in low-mass protostars and close to 1 in the Orion IRc2 massive hot core. Aims. We present new measurements of the gas-phase [CH 2 DOH]/[CH 3 OD] ratio in two additional high-mass protostars, as well as in two intermediate-mass protostars, to either confirm or exclude the dependence of this ratio on the mass of the protostar. Methods. The observations were carried out using the IRAM-30 m telescope. Several rotational lines of each isotopologue were detected toward the intermediate-mass protostars, while only CH 3 OD lines were detected in the massive hot cores. The ratio [CH 2 DOH]/[CH 3 OD] (or its upper limit) was computed from both the averaged column densities and directly from line flux ratios. Results. Our results confirm that the [CH 2 DOH]/[CH 3 OD] ratio is substantially lower in massive hot cores than in (low-mass) hot-corinos, by typically one order of magnitude. Furthermore, they suggest that intermediate-mass protostars have similar properties to low-mass protostars. Conclusions. The measured [CH 2 DOH]/[CH 3 OD] ratios are inconsistent with the current theory of methanol deuteration, indepen-dently of the mass of the source. While the large ratios measured in low-and intermediate-mass sources can be explained qualitatively by various selective depletion mechanisms, the small ratios (<2) measured toward massive hot cores are puzzling. A revision of the deuterium chemistry in hot cores is suggested.