![Moment 0 maps of the transitions of CH3OH at 282213.3 MHz (Eup = 341 K, Aij = 9 × 10−7 s−1) and 281000.1 MHz (Eup = 191 K, Aij = 4 × 10−5 s−1), 13CH3OH at 283207.3 MHz (two transitions with Eup = 95 and 110 K, Aij = 7 × 10−5 s−1), CH18 3 OH at 309979.3 MHz (Eup = 77 K, Aij = 3 × 10−4 s−1 ), CH3OD at 291412.8 MHz (Eup = 161 K, Aij = 1 × 10−4 s−1 ), CH2DOH at 279335.7 MHz (Eup = 132 K, Aij = 3 × 10−5 s−1 ), CHD2OH at 296460.6 MHz (Eup = 108 K, Aij = 7 × 10−5 s−1 ), and CD3OH at 305957.8 MHz (Eup = 163 K, Aij = 2 × 10−4 s−1 ). The integration was done between -9 and 0 km s−1. The continuum peak (C) and the blueshifted (B) and the redshifted (R) positions are indicated with crosses. The directions of the blueshifted and redshifted outflows are indicated with cyan and orange arrows, respectively. The 0,0 position is the continuum peak position. [astro-ph.GA]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/11/complex.png?fit=1200%2C675&ssl=1)
[astro-ph.GA]. [Abridged] Methanol is a complex organic molecule detected in both ice and gas toward star-forming regions. Due to its high abundance, its rarer isotopologues, including the deuterated ones, are also commonly detected.
Our aim is to determine the column density and deuterium fractionation of methanol in the low-mass protostar BHR71-IRS1. We analyzed data from a large spectral survey of BHR71-IRS1 carried out as part of the ALMA Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS).
We used the CASSIS software to identify the lines of the methanol isotopologues and constrain their column densities under the assumption of local thermodynamic equilibrium. We detected CH3OH, 13CH3OH, CH318OH, CH3OD, CH2DOH, CHD2OH, and CD3OH at the continuum peak position.
In addition, CH317OH is tentatively detected, while CD3OD is not detected, although a few faint lines could be present toward a position redshifted from the continuum peak. The column densities of the main isotopologue obtained from 13CH3OH and CH318OH are consistent, assuming nominal 12C/13C and 16O/18O ratios of 68 and 557, respectively. The CH2DOH/CH3OD column density ratio is equal to 7±2.
The statistically corrected D/H ratio is higher for CH2DOH (1.9±0.6 %) than for CH3OD (0.8±0.2 %). The level of deuteration after statistical correction increases with the number of D atoms in the methyl group, reaching 23±5 % for CD3OH/CH3OH. These trends are similar to other low-mass protostars such as IRAS~16293–2422 and HOPS 373SW, but seem to differ from the eruptive young star V883-Ori.
Similar studies with comparable datasets will be carried out for the other COMPASS sources to determine if factors such as environmental conditions and evolutionary states impact the deuteration of methanol.
A. Coutens, F. Cruz-Sáenz de Miera, J. K. Jørgensen, M. N. Drozdovskaya, J.-E. Lee, A. L. Plunkett, D. Harsono, S. Maret, A. Belloche, J. Ferrer Asensio, M. L. R. van’t Hoff, J.-H. Jeong, Á. Kóspál, B. A. McGuire, P. Nazari, S. Spezzano, Z. Telkamp, Y.-L. Yang, H.-S. Yun, S. Zeng, A. Andreu, J. Bergner, C.-H. Kim, N. F. W. Ligterink, Y. Lin, S.-Y. Liu, M. Lützen, P. Marchand, M. Rao
Comments: Accepted in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2610.07463 [astro-ph.GA] (or arXiv:2610.07463v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2610.07463
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Related DOI:
https://doi.org/10.1051/0004-6361/202558733
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Submission history
From: Audrey Coutens
[v1] Mon, 5 Oct 2026 22:23:37 UTC (2,396 KB)
https://arxiv.org/abs/2610.07463
Astrobiology, Astrochemistry, Astronomy,
