Methyl cyanide (CH3CN) and propyne (CH3CCH) in the low mass protostar IRAS 16293-2422

Abstract

Methyl cyanide (CH3CN) and propyne (CH3CCH) are two molecules commonly used as gas thermometers for interstellar gas. They are detected in several astrophysical environments and in particular towards protostars. Using data of the low-mass protostar IRAS 16293-2422 obtained with the IRAM 30m single-dish telescope, we constrained the origin of these two molecules in the envelope of the source. The line shape comparison and the results of a radiative transfer analysis both indicate that the emission of CH3CN arises from a warmer and inner region of the envelope than the CH3CCH emission. We compare the observational results with the predictions of a gas-grain chemical model. Our model predicts a peak abundance of CH3CCH in the gas-phase in the outer part of the envelope, at around 2000 au from the central star, which is relatively close to the emission size derived from the observations. The predicted CH3CN abundance only rises at the radius where the grain mantle ices evaporate, with an abundance similar to the one derived from the observations.

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• The ALMA-PILS survey: First detection of nitrous acid (HONO) in the interstellar medium
• The ALMA-PILS survey: First detection of the unsaturated 3-carbon molecules Propenal (C${}_2$H${}_3$CHO) and Propylene (C${}_3$H${}_6$) towards IRAS 16293$-$2422 B
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• Gas-grain model of carbon fractionation in dense molecular clouds
• The ALMA-PILS survey: propyne (CH${}_3$CCH) in IRAS 16293$-$2422
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• A spectral survey of CH3CCH in the Hot Molecular Core G331.512-0.103
• Characterization of acetonitrile ice irradiated by X-rays employing the PROCODA code: II. Desorption processes
• Collisional excitation of propyne (CH${}_3$CCH) by He atoms
• Physicochemical models: source-tailored or generic?
• Study of Complex Nitrogen and Oxygen-bearing Molecules toward the High-mass Protostar IRAS 18089$-$1732
• Parsec scales of carbon chain and complex organic molecules in AFGL 2591 and IRAS 20126
• Looking for evidence of high-mass star formation at core scale in a massive molecular clump
• New constraints on the initial parameters of low-mass star formation from chemical modeling
• Modelling carbon chain and complex organic molecules in the DR21(OH) clump