A major asymmetric ice trap in a planet-forming disk: III. First detection of dimethyl ether

Abstract

The complex organic molecules (COMs) detected in star-forming regions are the precursors of the prebiotic molecules that can lead to the emergence of life. By studying COMs in more evolved protoplanetary disks we can gain a better understanding of how they are incorporated into planets. This paper presents ALMA band 7 observations of the dust and ice trap in the protoplanetary disk around Oph IRS 48. We report the first detection of dimethyl ether (CH3OCH3) in a planet-forming disk and a tentative detection of methyl formate (CH3OCHO). We determined column densities for the detected molecules and upper limits on non-detected species using the CASSIS spectral analysis tool. The inferred column densities of CH3OCH3 and CH3OCHO with respect to methanol (CH3OH) are of order unity, indicating unusually high abundances of these species compared to other environments. Alternatively, the 12CH3OH emission is optically thick and beam diluted, implying a higher CH3OH column density and a smaller emitting area than originally thought. The presence of these complex molecules can be explained by thermal ice sublimation, where the dust cavity edge is heated by irradiation and the full volatile ice content is observable in the gas phase. This work confirms the presence of oxygen-bearing molecules more complex than CH3OH in protoplanetary disks for the first time. It also shows that it is indeed possible to trace the full interstellar journey of COMs across the different evolutionary stages of star, disk, and planet formation.

Accepted to A&A - 20th Jan 2022

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Cited by in corpus (12)

• LIDA - The Leiden Ice Database for Astrochemistry
• CoCCoA: Complex Chemistry in hot Cores with ALMA. Selected oxygen-bearing species
• Formation of S-bearing complex organic molecules in interstellar clouds via ice reactions with C2H2, HS, and atomic H
• FAUST XVII: Super deuteration in the planet forming system IRS 63 where the streamer strikes the disk
• A major asymmetric ice trap in a planet-forming disk IV. Nitric oxide gas and a lack of CN tracing sublimating ices and a C/O ratio $<1$
• The rapid formation of macromolecules in irradiated ice of protoplanetary disk dust traps
• The Molecular Composition of Shadowed Protosolar Disk Midplanes beyond the Water Snowline
• Conformational isomerism of methyl formate: new detections of the higher-energy trans conformer and theoretical insights
• Meteorite Parent Body Aqueous Alteration Simulations of Interstellar Residue Analogs
• An SMA Survey of Chemistry in Disks around Herbig AeBe Stars
• Complex Organic Molecules Formation in Cold Cores on Stochastically Heated Grains
• Protoplanetary Disk Chemistry