[astro-ph.GA] Chemical correlations between molecules provide powerful diagnostics to probe the physical conditions of protostellar outflows. In particular, the relationship between methanol (CH3OH) and methyl cyanide (CH3CN) offers a promising tool to investigate the chemistry and irradiation environment of shocked gas.
In this Letter, we use the CH3OH/CH3CN abundance ratio to constrain the physical properties of the outflow driven by the Class 0 protostar S68N using ALMA Band 3 and Band 6 observations. Assuming local thermodynamic equilibrium (LTE), we derive excitation temperatures of 50-60 K and column densities of 2-3×1013 cm−2 for CH3CN and 3-5×1015 cm−2 for CH3OH.
The resulting CH3OH/CH3CN abundance ratio is nearly constant along the outflow, with values of ∼100-200, similar to those found in other protostellar environments. Using an up-to-date astrochemical model, we test whether gas-phase formation of CH3CN can account for the observed ratios. We find that they are reproduced only by assuming enhanced cosmic-ray ionization rates ζCR up to ∼10−14 s−1.
These results suggest that the CH3OH-CH3CN correlation can be used as a probe of the irradiation conditions in protostellar outflows. Further studies are required to explore the possible contribution of grain-surface formation of CH3CN which could lead to a lower ζCR and to extend the analysis to a larger sample of sources.
L. Giani, D. Zaremba, M. De Simone, L. Tychoniec, L. Podio, C. Codella, A. Somigliana
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2606.26827 [astro-ph.GA] (or arXiv:2606.26827v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2606.26827
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Submission history
From: Lisa Giani
[v1] Thu, 25 Jun 2026 10:06:37 UTC (1,188 KB)
https://arxiv.org/abs/2606.26827
Astrobiology, Astrochemistry,
