Speaker
Description
Most of the stars in the Universe will end their evolution by losing their envelope during the thermally pulsing asymptotic giant branch (TP-AGB) phase, enriching the interstellar medium of galaxies with heavy elements, partially condensed into dust grains formed in their extended envelopes. Among these stars, carbon-rich TP-AGB stars (C-stars) are particularly relevant for the chemical enrichment of the local and high-redshift galaxies.
We have investigated the role of the metallicity in the dust formation process from a theoretical viewpoint by coupling an up to date description of dust growth and dust-driven wind, including the time-averaged effect of shocks propagating into the circumstellar envelope, with the stellar evolutionary tracks computed with the FUNS code. We compare our predictions with observations of C-stars in our Galaxy, in the Magellanic Clouds and in the Galactic Halo, characterised by metallicity between solar and 1/10 of solar.
Our calculations explain the variation of acetylene molecules in the gas phase and dust content around C-stars derived from the IRS Spitzer spectra as a function of the metallicity. The wind speed of the C-stars observed at varying metallicity is fairly well reproduced by our description.
We predict the properties of the circumstellar envelope, including the wind speed, down to metallicities of 1/10 solar for different stellar masses, representative of diverse environments, including metal-poor star-forming dwarf galaxies. The model predictions can be tested with future observations performed by the Atacama Large Millimeter Array (ALMA) and the James Webb Space Telescope (JWST).
| Session | Dust and presolar grains |
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