Chemical modelling of dust-gas chemistry within AGB outflows III. Photoprocessing of the ice and return to the ISM
arXiv:2011.11563 · doi:10.1093/mnras/staa3689
Abstract
To explain the properties of dust in the interstellar medium (ISM), the presence of a refractory organic mantle is necessary. The outflows of AGB stars are among the main contributors of stellar dust to the ISM. We present the first study of the refractory organic contribution of AGB stars to the ISM. Based on laboratory experiments, we included a new reaction in our extended chemical kinetics model: the photoprocessing of volatile complex ices into inert refractory organic material. The refractory organic feedback of AGB outflows to the ISM is estimated using observationally motivated parent species and grids of models of C-rich and O-rich outflows. Refractory organic material is mainly inherited from the gas phase through accretion onto the dust and subsequent photoprocessing. Grain-surface chemistry, initiated by photodissociation of ices, produces only a minor part and takes place in a sub-monolayer regime in almost all outflows. The formation of refractory organic material increases with outflow density and depends on the initial gas-phase composition. While O-rich dust is negligibly covered by refractory organics, C-rich dust has an average coverage of , but can be as high as . Although C-rich dust does not enter the ISM bare, its average coverage is too low to influence its evolution in the ISM or significantly contribute to the coverage of interstellar dust. This study opens up questions on the coverage of other dust-producing environments. It highlights the need for an improved understanding of dust formation and for models specific to density structures within the outflow.
18 pages, 16 figures, 6 tables, accepted for for publication in the Monthly Notices of the Royal Astronomical Society
References in corpus (19)
- Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
- The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point
- Radiative transfer in very optically thick circumstellar disks
- Complex organic molecules in protoplanetary disks
- Unexpectedly large mass loss during the thermal pulse cycle of the red giant R Sculptoris!
- Imaging the circumstellar envelopes of AGB stars
- (Sub)stellar companions shape the winds of evolved stars
- Chemical equilibrium in AGB atmospheres: Successes, failures, and prospects for small molecules, clusters, and condensates
- ALMA data suggest the presence of a spiral structure in the inner wind of CW Leo
- The wonderful complexity of the Mira AB system
- 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
- Evidence of surface catalytic effect on cosmic dust grain analogues: the ammonia and carbon dioxide surface reaction
- 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
- Reduction of the maximum mass-loss rate of OH/IR stars due to unnoticed binary interaction
- Sticky or not sticky? Measurements of the tensile strength of micro-granular organic materials
- The Role of Internal Photons on the Chemistry of the Circumstellar Envelopes of AGB Stars
- Dust-gas chemistry in AGB outflows: Chemical modelling of dust-gas chemistry within AGB outflows I. Effect on the gas-phase chemistry
- Chemical modelling of dust-gas chemistry within AGB outflows -- II. Effect of the dust-grain size distribution