Ice Origins of OCS and Chemistry of CS2-bearing Ice Mantles
Understanding the formation of carbonyl sulfide (OCS) in interstellar ices is key to constrain the sulfur chemistry in the interstellar medium (ISM), since it is the only ice S-bearing molecule securely detected thus far.
Two general pathways for OCS formation have been proposed: sulfurization of CO (CO+S) and oxidation of CS (CS+O), but their relative contribution in interstellar ices remains unconstrained. We have evaluated the contribution of both pathways to OCS formation upon energetic processing in isotopically-labeled CO2:CS2 and CO:CS2 ice samples at 7-50 K.
Our results indicated that formation of OCS through the CS+O pathway was more favorable than through the CO+S pathway, as previously suggested by theoretical calculations. In addition, its relative contribution increased at higher temperatures. Therefore, this pathway could play a role in the ice formation of OCS, especially in warm regions where CO is expected to be preferentially in the gas phase.
At the same time, we have explored the chemistry of CS2-bearing, CO2-, CO-, and also H2O-rich ices, that could be relevant to the sulfur interstellar chemistry. We observed formation of a variety of S-bearing products in addition to OCS, including SO2, C3S2, and S2.
However, a significant fraction of sulfur was not detected at the end of the experiments, and could be locked in long, undetectable sulfur allotropes, one of the potential carriers of the missing sulfur in the dense ISM.
Rafael Martin-Domenech, Karin I. Öberg, Guillermo M. Muñoz Caro, Héctor Carrascosa de Lucas, Asunción Fuente, Mahesh Rajappan
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2410.07736 [astro-ph.GA] (or arXiv:2410.07736v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2410.07736
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Submission history
From: Rafael Martín-Doménech
[v1] Thu, 10 Oct 2024 09:13:23 UTC (991 KB)
https://arxiv.org/abs/2410.07736
Astrobiology, Astronomy, Astrochemistry,
