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A study of methanol and silicon monoxide production through episodic explosions of grain mantles in the Central Molecular Zone

Coutens, A; Rawlings, JMC; Viti, S; Williams, DA; (2017) A study of methanol and silicon monoxide production through episodic explosions of grain mantles in the Central Molecular Zone. Monthly Notices of the Royal Astronomical Society , 467 (1) pp. 737-746. 10.1093/mnras/stx119. Green open access

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Abstract

Methanol (CH3OH) is found to be abundant and widespread towards the Central Molecular Zone, the inner few hundred parsecs of our Galaxy. Its origin is, however, not fully understood. It was proposed that the high cosmic ray ionization rate in this region could lead to a more efficient non-thermal desorption of this species formed on grain surfaces, but it would also mean that this species is destroyed in a relatively short time-scale. In a first step, we run chemical models with a high cosmic ray ionization rate and find that this scenario can only reproduce the lowest abundances of methanol derived in this region (∼10−9–10−8). In a second step, we investigate another scenario based on episodic explosions of grain mantles. We find a good agreement between the predicted abundances of methanol and the observations. We find that the dominant route for the formation of methanol is through hydrogenation of CO on the grains, followed by the desorption due to the grain mantle explosion. The cyclic aspect of this model can explain the widespread presence of methanol without requiring any additional mechanism. We also model silicon monoxide (SiO), another species detected in several molecular clouds of the Galactic Centre. An agreement is found with observations for a high depletion of Si (Si/H ∼ 10−8) with respect to the solar abundance.

Type: Article
Title: A study of methanol and silicon monoxide production through episodic explosions of grain mantles in the Central Molecular Zone
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stx119
Publisher version: http://dx.doi.org/10.1093/mnras/stx119
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Astrochemistry; ISM: molecules; Galaxy: abundances; Galaxy: centre
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1536293
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