The ALMA-PILS survey: The first detection of doubly-deuterated methyl formate (CHD2OCHO) in the ISM
Journal article, 2019

Studies of deuterated isotopologues of complex organic molecules can provide important constraints on their origin in regions of star formation. In particular, the abundances of deuterated species are very sensitive to the physical conditions in the environment where they form. Due to the low temperatures in regions of star formation, these isotopologues are enhanced to significant levels, making detections of multiply-deuterated species possible. However, for complex organic species, only the multiply-deuterated variants of methanol and methyl cyanide have been reported so far. The aim of this paper is to initiate the characterisation of multiply-deuterated variants of complex organic species with the first detection of doubly-deuterated methyl formate, CHD2OCHO. We use ALMA observations from the Protostellar Interferometric Line Survey (PILS) of the protostellar binary IRAS 16293-2422, in the spectral range of 329.1 GHz to 362.9 GHz. We report the first detection of doubly-deuterated methyl formate CHD2OCHO in the ISM. The D/H ratio of CHD2OCHO is found to be 2-3 times higher than the D/H ratio of CH2DOCHO for both sources, similar to the results for formaldehyde from the same dataset. The observations are compared to a gas-grain chemical network coupled to a dynamical physical model, tracing the evolution of a molecular cloud until the end of the Class 0 protostellar stage. The overall D/H ratio enhancements found in the observations are of the same order of magnitude as the predictions from the model for the early stages of Class 0 protostars. However, the higher D/H ratio of CHD2OCHO compared to the D/H ratio of CH2DOCHO is still not predicted by the model. This suggests that a mechanism is enhancing the D/H ratio of singly- and doubly-deuterated methyl formate that is not in the model, e.g. mechanisms for H-D substitutions.

ISM: molecules


ISM: individual objects: IRAS 16293-2422

Stars: formation

Stars: protostars


S. Manigand

University of Copenhagen

Hannah Calcutt

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

J. K. Jørgensen

University of Copenhagen

V. Taquet

Istituto nazionale di astrofisica (INAF)

H. S. P. Muller

University of Cologne

A. Coutens

University of Bordeaux

S. F. Wampfler

University of Bern

N. F. W. Ligterink

University of Bern

M. N. Drozdovskaya

University of Bern

L. E. Kristensen

University of Copenhagen

M. H. D. van der Wiel

Netherlands Institute for Radio Astronomy (ASTRON)

T. L. Bourke

Jodrell Bank Observatory

Astronomy and Astrophysics

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

Protostellar Interferometric Line Survey (PILS)

European Research Council (ERC), 2019-10-30 -- .

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences



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