What can stellar metallicity tell about galactic outflow? I
will be talking about the stellar-phase mass - metallicity relation of
quiescent galaxies and its evolution with redshift. I will show how the
relation can be used to constrain mass-loading factor as a function
of mass. Other possible applications include: 1) to determine
whether quiescent galaxies evolve passively; and 2) to compare
stellar metallicity with gas-phase metallicity in star-forming galaxies
without directly measuring stellar metallicities in star-forming galaxies.