2.2. The Galactic Mass-Metallicity Relation
Studies of nearby galaxies reveal that higher metallicities occur in more massive systems (Faber 1973, Bender et al. 1993, Zaritsky et al. 1994). Massive galaxies reach higher Z's because they have deeper gravitational potentials and are better able to retain their gas against the building thermal pressures from supernovae (Larson 1974). Low-mass galaxies eject their gas before high Z's are attained. Quasar abundance estimates should therefore constrain the gravitational binding energy of the local star-forming regions and, perhaps, the total masses of the host galaxies.