Interferometric observations of warm deuterated methanol in the inner regions of low-mass protostars
Journal article, 2019

Methanol is a key species in astrochemistry because it is the most abundant organic molecule in the interstellar medium and is thought to be the mother molecule of many complex organic species. Estimating the deuteration of methanol around young protostars is of crucial importance because it highly depends on its formation mechanisms and the physical conditions during its moment of formation. We analyse several dozen transitions from deuterated methanol isotopologues coming from various existing observational datasets obtained with the IRAM-PdBI and ALMA sub-millimeter interferometers to estimate the methanol deuteration surrounding three low-mass protostars on Solar System scales. A population diagram analysis allows us to derive a [CH2DOH]/[CH3OH] abundance ratio of 3-6% and a [CH3OD]/[CH3OH] ratio of 0.4-1.6%in the warm inner (≤100-200 AU) protostellar regions. These values are typically ten times lower than those derived with previous single-dish observations towards these sources, but they are one to two orders of magnitude higher than the methanol deuteration measured in massive hot cores. Dust temperature maps obtained from Herschel and Planck observations show that massive hot cores are located in warmer molecular clouds than low-mass sources, with temperature differences of ∼10 K. The comparison of our measured values with the predictions of the gas-grain astrochemical model GRAINOBLE shows that such a temperature difference is sufficient to explain the different deuteration observed in low- to high-mass sources. This suggests that the physical conditions of the molecular cloud at the origin of the protostars mostly govern the present-day observed deuteration of methanol and therefore of more complex organic molecules. Finally, the methanol deuteration measured towards young solar-type protostars on Solar System scales seems to be higher by a factor of ∼5 than the upper limit in methanol deuteration estimated in comet Hale-Bopp. If this result is confirmed by subsequent observations of other comets, it would imply that an important reprocessing of the organic material likely occurred in the solar nebula during the formation of the Solar System.

Submillimeter: ISM

Molecular processes

Stars: formation


ISM: abundances

ISM: molecules


V. Taquet

Arcetri Astrophysical Observatory

E. Bianchi

Université Grenoble Alpes

Arcetri Astrophysical Observatory

C. Codella

Arcetri Astrophysical Observatory

Université Grenoble Alpes

Magnus V. Persson

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

C. Ceccarelli

Université Grenoble Alpes

S. Cabrit

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

Jes K. Jørgensen

Niels Bohr Institute

C. Kahane

Université Grenoble Alpes

A. López-Sepulcre

Université Grenoble Alpes

Institut de RadioAstronomie Millimetrique (IRAM)

R. Neri

Institut de RadioAstronomie Millimetrique (IRAM)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 632 A19

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology




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