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Methanol mapping in cold cores: testing model predictions*

Punanova, Anna, Vasyunin, Anton, Caselli, Paola, Howard, Alexander, Spezzano, Silvia, Shirley, Yancy, Scibelli, Samantha and Harju, Jorma 2022. Methanol mapping in cold cores: testing model predictions*. Astrophysical Journal 927 (2) , 213. 10.3847/1538-4357/ac4e7d

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Chemical models predict that in cold cores gas-phase methanol is expected to be abundant at the outer edge of the CO depletion zone, where CO is actively adsorbed. CO adsorption correlates with volume density in cold cores, and, in nearby molecular clouds, catastrophic CO freeze-out happens at volume densities above 104 cm−3. The methanol production rate is maximized there and its freeze-out rate does not overcome its production rate, while the molecules are shielded from UV destruction by gas and dust. Thus, in cold cores, methanol abundance should generally correlate with visual extinction, which depends on both volume and column density. In this work, we test the most basic model prediction that maximum methanol abundance is associated with a local AV ∼ 4 mag in dense cores and constrain the model parameters with the observational data. With the IRAM 30 m antenna, we mapped the CH3OH (2–1) and (3–2) transitions toward seven dense cores in the L1495 filament in Taurus to measure the methanol abundance. We use the Herschel/SPIRE maps to estimate visual extinction, and the C18O(2–1) maps from Tafalla & Hacar to estimate CO depletion. We explored the observed and modeled correlations between the methanol abundances, CO depletion, and visual extinction, varying the key model parameters. The modeling results show that hydrogen surface diffusion via tunneling is crucial to reproduce the observed methanol abundances, and the necessary reactive desorption efficiency matches the one deduced from laboratory experiments.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Additional Information: Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.
Publisher: American Astronomical Society
ISSN: 0004-637X
Date of First Compliant Deposit: 25 August 2022
Date of Acceptance: 8 December 2021
Last Modified: 23 May 2023 15:16

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