Spitzer observations of molecules and dust in evolved stars in nearby
  galaxies
  Molecules and dust are formed in and around the asymptotic giant branch (AGB)
stars and supernovae (SNe), and are ejected into the interstellar medium (ISM)
through the stellar wind. The dust and gas contain elements newly synthesised
in stars, thus, dying stars play an important role on chemical enrichment of
the ISM of galaxies. However, quantitative analysis of molecules and dust in
these stars had been difficult beyond our Galaxy. The high sensitivity
instruments on board the Spitzer Space Telescope have enabled us to study dust
and molecules in these stars in nearby galaxies. Nearby galaxies have wide
range of metallicities, thus the impact of the metallicity on dust and gas
production can be studied. This study will be useful for chemical evolution of
galaxies from low to high metallicities.
