Nascent Chemical Complexity In Prestellar Core IRAS 16293E: Complex Organics And Deuterated Methanol

Prestellar cores represent early sites of low-mass (M ≤ few M_⊙) star and planet formation and provide insight into initial chemical conditions of complex organic molecules (COMs).

Deuterated COMs trace the degree of molecular inheritance and/or reprocessing, as high deuteration in protostellar systems suggests COMs forming during the prestellar stage when deuteration is enhanced.

Within the L1689N molecular cloud, the prestellar core IRAS 16293E sits 90″ eastward of the chemically-rich IRAS 16293-2422 A and B protostellar system. A unique view of star formation inside a common natal cloud, IRAS 16293A, B, and E all show some of the highest levels of deuteration in the ISM, with a number of D/H ratios 105 times higher than Solar.

We investigate for the first time the deuteration levels of the simplest COM, methanol (CH₃OH), in IRAS 16293E. Using the Arizona Radio Observatory (ARO) 12 m telescope, we target favorable transitions of CH₂DOH, CHD₂OH, ¹³CH₃OH, and several higher complexity COMs (including acetaldehyde, CH₃CHO, methyl formate, HCOOCH₃, and dimethyl ether, CH₃OCH₃) in the 3 mm band. Follow-up observations with the Yebes 40 m telescope provided additional transitions in the 7 mm (Q-band).

We report the first detections of these COMs and deuterated methanol in prestellar core IRAS 16293E and use our observations to calculate excitation temperatures, column densities, and relative abundance ratios. Striking similarities are found between relative molecular ratios and D/H values when comparing IRAS 16293E to the A and B protostars, as well as to a heterogeneous sample of other prestellar cores, protostars, and the comet 67P/Churyumov-Gerasimenko.

Our results support the idea that there is a limited amount of chemical reprocessing of COMs when prestellar cores collapse and heat-up during the protostellar phase.

Samantha Scibelli, Maria N. Drozdovskaya, Paola Caselli, Judit Ferrer Asensio, Beatrice Kulterer, Silvia Spezzano, Yuxin Lin, Yancy Shirley

Comments: 18 pages; Accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2508.04762 [astro-ph.GA] (or arXiv:2508.04762v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2508.04762
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Submission history
From: Samantha Scibelli
[v1] Wed, 6 Aug 2025 18:00:00 UTC (5,852 KB)
https://arxiv.org/abs/2508.04762
Astrobiology, Astrochemistry,