Determining the methanol deuteration in the disk around V883 Orionis with laboratory measured spectroscopy

TL;DR

This study measures methanol deuteration in the V883 Ori disk using laboratory spectroscopy and ALMA data, revealing low D/H ratios and highlighting the importance of accurate spectroscopic data for understanding chemical processes in star-forming regions.

Contribution

It provides new laboratory spectroscopic data for methanol isotopologues and applies them to ALMA observations, improving the accuracy of deuteration measurements in a protoplanetary disk.

Findings

Derived D/H ratios for CH$_2$DOH and CH$_3$OD in V883 Ori.

Found a low CH$_2$DOH/CH$_3$OD ratio of 1.22.

Highlighted the impact of spectroscopic data on molecular abundance estimates.

Abstract

Deuterium fractionation, as studied through mono-deuterated methanol, is frequently used as a diagnostic tool to trace the physical conditions and chemical evolution of interstellar sources. This study investigates methanol deuteration in the disk around V883 Ori, utilising recent laboratory spectroscopic data for CH$_2$DOH and CH$_3$OD along with ALMA observations. The derived column densities for CH$_2$DOH and CH$_3$OD are (5.14$\pm$0.08) $\times $10$^{16}$ cm$^{-2}$ and (4.22$\pm$0.06) $\times$ 10$^{16}$ cm$^{-2}$, respectively. The analysis demonstrates the influence of spectroscopic data on determining molecular column density, excitation temperature, and, most importantly, the inferred D/H ratio. The D/H ratio for CH$_2$DOH is calculated to be (7.3$\pm$1.5) $\times$ 10$^{-3}$ after applying a statistical correction, whilst the D/H ratio for CH$_3$OD is (1.79$\pm$0.36) $\times$ 10$^{-2}$. The discovery of an unexpectedly low CH$_2$DOH/CH$_3$OD ratio (1.22$\pm$0.02) in V883 Ori, however, raises further questions about the synthesis and chemical processes involved in CH$_3$OD formation. Overall, this study underscores the importance of accurate spectroscopic data for studies of isotopic fractionation and provides new insights into methanol deuteration chemistry in star-forming regions. Future research, combining updated spectroscopy and chemical modelling, will help further constrain these processes across different masses and evolutionary stages.