Laboratory Rotational Spectroscopy Leads to the First Interstellar Detection of Singly Deuterated Methyl Mercaptan (CH2DSH)

We report an extensive rotational spectroscopic analysis of singly deuterated methyl mercaptan (CH₂DSH) using both millimeter and far-infrared synchrotron spectra to achieve a global torsional analysis of the three lowest torsional substates (e0, e1, and o1) of this non-rigid species.

A fit including 3419 millimeter wave transitions along with 43 infrared torsional subband centers was performed with root mean square deviations of 0.233 MHz and 0.270 cm⁻¹, respectively, resulting in 68 fit parameters.

A spectroscopic catalogue built from this analysis for a temperature of 125 K has led to the first interstellar detection of CH₂DSH towards the Solar-like protostar IRAS 16293-2422 B. We report the identification of 46 transitions, including eight relatively unblended lines, resulting in a derived column density of (3.0±0.3)×1014 cm⁻². The column density ratio for HDCS/CH₂DSH compared to HDCO/CH₂DOH suggests a difference in the interstellar chemistry between the sulphur and oxygen complex organics, in particular a different link between H₂CO and CH₃OH and between H₂CS and CH₃SH.

This is the first interstellar detection of a deuterated sulphur-bearing COM and therefore an important step into understanding the chemical origin of sulphur-based prebiotics.

Hayley A. Bunn, Silvia Spezzano, Laurent H. Coudert, Jean-Claude Guillemin, Yuxin Lin, Christian P. Endres, Brant Billinghurst, Olivier Pirali, Jes Jørgensen, Valerio Lattanzi, Paola Caselli

Comments: Accepted for publication in Astrophysical Journal Letters (ApJL)
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2501.15944 [astro-ph.GA] (or arXiv:2501.15944v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2501.15944
Focus to learn more
Submission history
From: Hayley Bunn
[v1] Mon, 27 Jan 2025 10:44:15 UTC (573 KB)
https://arxiv.org/abs/2501.15944
Astrobiology, Astrochemistry