Astro2020 Science White Paper: The fundamentals of outflows from evolved
  stars
  Models of the chemical evolution of the interstellar medium, galaxies, and
the Universe rely on our understanding of the amounts and chemical composition
of the material returned by stars and supernovae. Stellar yields are obtained
from stellar-evolution models, which currently lack predictive prescriptions of
stellar mass loss, although it significantly affects stellar lifetimes,
nucleosynthesis, and chemical ejecta. Galaxy properties are derived from
observations of the integrated light of bright member stars. Stars in the late
stages of their evolution are among the infrared-brightest objects in galaxies.
An unrealistic treatment of the mass-loss process introduces significant
uncertainties in galaxy properties derived from their integrated light. We
describe current efforts and future needs and opportunities to characterize AGB
outflows: driving mechanisms, outflow rates, underlying fundamental physical
and chemical processes such as dust grain formation, and dependency of these on
metallicity.
