Chemical modelling of dust-gas chemistry within AGB outflows -- II. Effect of the dust-grain size distribution

Abstract

AGB stars are, together with supernovae, the main contributors of stellar dust to the interstellar medium (ISM). Dust grains formed by AGB stars are thought to be large. However, as dust nucleation and growth within their outflows are still not understood, the dust-grain size distribution (GSD) is unknown. This is an important uncertainty regarding our knowledge of the chemical and physical history of interstellar dust, as AGB dust forms $\sim$ 70% of the starting point of its evolution. We expand on our chemical kinetics model, which uniquely includes a comprehensive dust-gas chemistry. The GSD is now allowed to deviate from the commonly assumed canonical Mathis et al. (1977) distribution. We find that the specific GSD can significantly influence the dust-gas chemistry within the outflow. Our results show that the level of depletion of gas-phase species depends on the average grain surface area of the GSD. Gas-phase abundance profiles and their possible depletions can be retrieved from observations of molecular emission lines when using a range of transitions. Due to degeneracies within the prescription of GSD, specific parameters cannot be retrieved, only (a lower limit to) the average grain surface area. Nonetheless, this can discriminate between dust composed of predominantly large or small grains. We show that when combined with other observables such as the spectral energy distribution and polarised light, depletion levels from molecular gas-phase abundance profiles can constrain the elusive GSD of the dust delivered to the ISM by AGB outflows.

17 pages, 10 figures, 6 tables. Accepted for publication in MNRAS

References in corpus (19)

• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point
• Radiative transfer in very optically thick circumstellar disks
• Binding energies: new values and impact on the efficiency of chemical desorption
• A close halo of large transparent grains around extreme red giant stars
• A Detailed Analysis of the Dust Formation Zone of IRC+10216 Derived from Mid-IR Bands of C2H2 and HCN
• Warm water vapour in the sooty outflow from a luminous carbon star
• The abundance of SiS in circumstellar envelopes around AGB stars
• SiO in C-rich circumstellar envelopes of AGB stars: effects of non-LTE chemistry and grain adsorption
• Two-size approximation: a simple way of treating the evolution of grain size distribution in galaxies
• The distribution of SiO in the circumstellar envelope around IRC+10216
• Estimating the dust production rate of carbon stars in the Small Magellanic Cloud
• Chemical content of the circumstellar envelope of the oxygen-rich AGB star R Dor: Non-LTE abundance analysis of CO, SiO, and HCN
• An edge-on translucent dust disk around the nearest AGB star L2 Puppis - VLT/NACO spectro-imaging from 1.04 to 4.05 microns and VLTI interferometry
• An ALMA view of CS and SiS around oxygen-rich AGB stars
• Inner dusty envelope of the AGB stars W~Hydrae, SW\,Virginis, and R~Crateris using SPHERE/ZIMPOL
• H2O vapor excitation in dusty AGB envelopes. A PACS view of OH 127.8+0.0
• Dust-gas chemistry in AGB outflows: Chemical modelling of dust-gas chemistry within AGB outflows I. Effect on the gas-phase chemistry
• Interferometric observations of SiO thermal emission in the inner wind of M-type AGB stars IK Tauri and IRC+10011

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• Evidence for episodic and patchy mass ejection in the circumstellar envelope of AGB star R Leonis
• Modeling extinction and reddening effects by circumstellar dust in the Betelgeuse envelope in the presence of radiative torque disruption
• In situ characterization of volatile and refractory hydrocarbons produced by UV photolysis of interstellar C${}_2$H${}_2$ ice
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