Linking interstellar and cometary O2: A deep search for 16O18O in the solar-Type protostar IRAS 16293b-2422
Journal article, 2018

Recent measurements carried out at comet 67P/Churyumov-Gerasimenko (67P) with the Rosetta probe revealed that molecular oxygen, O2, is the fourth most abundant molecule in comets. Models show that O2 is likely of primordial nature, coming from the interstellar cloud from which our solar system was formed. However, gaseous O2 is an elusive molecule in the interstellar medium with only one detection towards quiescent molecular clouds, in the ρ Oph A core. We perform a deep search for molecular oxygen, through the 21-01 rotational transition at 234 GHz of its 16O18O isotopologue, towards the warm compact gas surrounding the nearby Class 0 protostar IRAS 16293-2422 B with the ALMA interferometer. We also look for the chemical daughters of O2, HO2, and H2O2. Unfortunately, the H2O2 rotational transition is dominated by ethylene oxide c-C2H4O while HO2 is not detected. The targeted 16O18O transition is surrounded by two brighter transitions at ± 1 km s-1 relative to the expected 16O18O transition frequency. After subtraction of these two transitions, residual emission at a 3σ level remains, but with a velocity offset of 0.3-0.5 km s-1 relative to the source velocity, rendering the detection "tentative". We derive the O2 column density for two excitation temperatures Tex of 125 and 300 K, as indicated by other molecules, in order to compare the O2 abundance between IRAS 16293 and comet 67P. Assuming that 16O18O is not detected and using methanol CH3OH as a reference species, we obtain a [O2]/[CH3OH] abundance ratio lower than 2-5, depending on the assumed Tex, a three to four times lower abundance than the [O2]/[CH3OH] ratio of 5-15 found in comet 67P. Such a low O2 abundance could be explained by the lower temperature of the dense cloud precursor of IRAS 16293 with respect to the one at the origin of our solar system that prevented efficient formation of O2 in interstellar ices.

ISM: individual objects: IRAS 16293-2422

ISM: Abundances

Molecular processes

ISM: molecules

Stars: formation



V. Taquet

Leiden University

Arcetri Astrophysical Observatory

E. F. van Dishoeck

Leiden University

Max Planck Society

M. Swayne

Leiden University

D. Harsono

Leiden University

Jes K. Jørgensen

University of Copenhagen

Luke T. Maud

Leiden University

N. F W Ligterink

Leiden University

H. S.P. Müller

University of Cologne

C. Codella

Arcetri Astrophysical Observatory

Kathrin Altwegg

University of Bern

A. Bieler

University of Michigan

A. Coutens

Laboratoire d'Astrophysique de Bordeaux

M. N. Drozdovskaya

University of Bern

Kenji Furuya

University of Tsukuba

Magnus V. Persson

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Merel L.R. Van'T Hoff

Leiden University

C. Walsh

University of Leeds

S. F. Wampfler

University of Bern

Astronomy and Astrophysics

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

Vol. 618 A11

Subject Categories

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

Theoretical Chemistry



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