Local constraints on alcohol--thioalcohol analogs in G35.2N
Abstract
The chemistry of sulfur-bearing complex organic molecules in dense star-forming environments remains uncertain, partly because the dominant sulfur reservoirs in dense gas and ices are poorly identified. Alcohol--thioalcohol pairs allow direct comparisons of structurally related O- and S-bearing molecules. We present ALMA Band 6 observations of CH3OH/CH3SH and C2H5OH/C2H5SH toward three spectral-extraction positions (MM3-pos, MM4-pos, and MM5-pos) in the MM3--MM5 region of G35.2N. Local thermodynamic equilibrium modeling yields column densities and abundance ratios. CH3OH column densities were inferred from 13CH3OH assuming 12C/13C = 50 to mitigate optical-depth effects. CH3OH, CH3SH, and C2H5OH are robustly constrained at all three positions; C2H5SH is robustly constrained at MM3-pos and MM5-pos but remains tentative at MM4-pos. The corresponding adopted column-density ranges are (1.8−2.7)×1018, (1.7−2.6)×1016, (5.7−8.5)×1016, and (2.4−4.6)×1015 cm−2. The CH3OH/C2H5OH and CH3OH/CH3SH ratios are consistent across the positions within uncertainties, with nominal values of 31--32 and 100--110, respectively. Comparisons with chemically rich sources and warm-up chemical models show that CH3OH/C2H5OH lies within the range measured elsewhere, whereas CH3OH/CH3SH exhibits greater source-to-source variation. The ethyl-level O/S comparison remains less certain because many literature C2H5SH measurements provide only lower limits. CH3OH/CH3SH is thus the best-constrained O/S alcohol--thioalcohol ratio in these data and provides an empirical probe of source-dependent sulfur-bearing organic chemistry. More sensitive C2H5SH observations are needed to test C2H5OH/C2H5SH.
Versions
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BibTeX
@misc{xu2026local,
title = {{Local constraints on alcohol--thioalcohol analogs in G35.2N}},
author = {Xuefang Xu and Shanghuo Li and Qian Gou and Chunguo Duan and Laurent Pagani and Di Li and Jun Kang and Jiaxin Du and Jiaxiang Jiao},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.20671},
eprint = {2609.20671},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20671},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Local constraints on alcohol--thioalcohol analogs in G35.2N
AU - Xuefang Xu
AU - Shanghuo Li
AU - Qian Gou
AU - Chunguo Duan
AU - Laurent Pagani
AU - Di Li
AU - Jun Kang
AU - Jiaxin Du
AU - Jiaxiang Jiao
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.20671
UR - https://arxiv.org/abs/2609.20671
AB - The chemistry of sulfur-bearing complex organic molecules in dense star-forming environments remains uncertain, partly because the dominant sulfur reservoirs in dense gas and ices are poorly identified. Alcohol--thioalcohol pairs allow direct comparisons of structurally related O- and S-bearing molecules. We present ALMA Band 6 observations of CH_3OH/CH_3SH and C_2H_5OH/C_2H_5SH toward three spectral-extraction positions (MM3-pos, MM4-pos, and MM5-pos) in the MM3--MM5 region of G35.2N. Local thermodynamic equilibrium modeling yields column densities and abundance ratios. CH_3OH column densities were inferred from ^13CH_3OH assuming ^12C/^13C = 50 to mitigate optical-depth effects. CH_3OH, CH_3SH, and C_2H_5OH are robustly constrained at all three positions; C_2H_5SH is robustly constrained at MM3-pos and MM5-pos but remains tentative at MM4-pos. The corresponding adopted column-density ranges are (1.8−2.7)×10^18, (1.7−2.6)×10^16, (5.7−8.5)×10^16, and (2.4−4.6)×10^15 cm^−2. The CH_3OH/C_2H_5OH and CH_3OH/CH_3SH ratios are consistent across the positions within uncertainties, with nominal values of 31--32 and 100--110, respectively. Comparisons with chemically rich sources and warm-up chemical models show that CH_3OH/C_2H_5OH lies within the range measured elsewhere, whereas CH_3OH/CH_3SH exhibits greater source-to-source variation. The ethyl-level O/S comparison remains less certain because many literature C_2H_5SH measurements provide only lower limits. CH_3OH/CH_3SH is thus the best-constrained O/S alcohol--thioalcohol ratio in these data and provides an empirical probe of source-dependent sulfur-bearing organic chemistry. More sensitive C_2H_5SH observations are needed to test C_2H_5OH/C_2H_5SH.
ER -