Early-type galaxies
Post-starburst galaxies
E+A galaxies
E+A galaxies have strong Balmer absorption lines typical of young stars, but lack optical emission features (e.g. O III 5007) typical of star-forming regions and have metallic absorption lines (e.g. Ca H and K) indicative of an older population of dwarf stars. The presence of two distinct stellar populations and morphological observations suggest that E+A galaxies are the product of a gas-rich galaxy merger.