Van de Sande, M, Walsh, C orcid.org/0000-0001-6078-786X, Mangan, TP et al. (1 more author) (2019) Chemical modelling of dust–gas chemistry within AGB outflows – I. Effect on the gas-phase chemistry. Monthly Notices of the Royal Astronomical Society, 490 (2). pp. 2023-2041. ISSN 0035-8711
Abstract
Chemical modelling of asymptotic giant branch (AGB) outflows is typically focused on either non-thermodynamic equilibrium chemistry in the inner region or photon-driven chemistry in the outer region. We include, for the first time, a comprehensive dust–gas chemistry in our AGB outflow chemical kinetics model, including both dust–gas interactions and grain-surface chemistry. The dust is assumed to have formed in the inner region, and follows an interstellar-like dust-size distribution. Using radiative transfer modelling, we obtain dust temperature profiles for different dust types in an O-rich and a C-rich outflow. We calculate a grid of models, sampling different outflow densities, drift velocities between the dust and gas, and dust types. Dust–gas chemistry can significantly affect the gas-phase composition, depleting parent and daughter species and increasing the abundance of certain daughter species via grain-surface formation followed by desorption/sputtering. Its influence depends on four factors: outflow density, dust temperature, initial composition, and drift velocity. The largest effects are for higher density outflows with cold dust and O-rich parent species, as these species generally have a larger binding energy. At drift velocities larger than ∼10 km s−1, ice mantles undergo sputtering; however, they are not fully destroyed. Models with dust–gas chemistry can better reproduce the observed depletion of species in O-rich outflows. When including colder dust in the C-rich outflows and adjusting the binding energy of CS, the depletion in C-rich outflows is also better reproduced. To best interpret high-resolution molecular line observations from AGB outflows, dust–gas interactions are needed in chemical kinetics models.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2019 The Author(s). This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | molecular processes; stars: AGB and post-AGB; circumstellar matter; ISM: molecules |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Astrophysics (Leeds) |
Funding Information: | Funder Grant number Science & Technology Facilities Council (STFC) ST/R000549/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 01 Nov 2019 13:56 |
Last Modified: | 01 Nov 2019 13:56 |
Status: | Published |
Publisher: | Oxford University Press |
Identification Number: | 10.1093/mnras/stz2702 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:152923 |