Is acetylene essential for carbon dust formation?

Abstract

We have carried out an investigation of the chemical evolution of gas in different carbon-rich circumstellar environments. Previous studies have tended to invoke terrestrial flame chemistries, based on acetylene (C2H2) combustion to model the formation of carbon dust, via Polycyclic Aromatic Hydrocarbons (PAHs). In this work we pay careful attention to the accurate calculation of the molecular photoreaction rate coefficients to ascertain whether there is a universal formation mechanism for carbon dust in strongly irradiated astrophysical environments. A large number of possible chemical channels may exist for the formation of PAHs, so we have concentrated on the viability of the formation of the smallest building block species, C2H2, in a variety of carbon-rich stellar outflows. C2H2 is very sensitive to dissociation by UV radiation. This sensitivity is tested, using models of the time-dependent chemistry. We find that C2H2 formation is sensitive to some of the physical parameters and that in some known sources of dust-formation it can never attain appreciable abundances. Therefore multiple (and currently ill-defined) dust-formation channels must exist.

10 pages, 4 figures, 5 tables

References in corpus (3)

• The Evolution of Dust in the Early Universe with Applications to the Galaxy SDSS J1148+5251
• A Detailed Analysis of the Dust Formation Zone of IRC+10216 Derived from Mid-IR Bands of C2H2 and HCN
• Detection of Acetylene toward Cepheus A East with Spitzer

Cited by in corpus (8)

• ExoMol molecular line lists -- XXXVII: spectra of acetylene
• Marvel analysis of the measured high-resolution rovibrational spectra of H2S
• MARVEL analysis of the measured high-resolution rovibrational spectra of C2H2
• The Role of Acetylene in the Chemical Evolution of Carbon Complexity
• Optical and infrared emission of H II complexes as a clue to the PAH life cycle
• Smoke on the wind: dust nucleation in archetype colliding wind pinwheel WR104
• Carbon 'fluffy' aggregates produced by helium - hydrocarbon high pressure plasmas as analogs to interstellar dust
• In situ characterization of volatile and refractory hydrocarbons produced by UV photolysis of interstellar C${}_2$H${}_2$ ice