The Origin of E+A Galaxies

E+A galaxies are galaxies with strong Balmer absorption lines and with no significant emission in [OII] or H$\alpha$ lines. The existence of strong Balmer absorption lines shows that these galaxies have experienced a starburst within the last 1 Gyr. At the same time, these galaxies do not show any sign of on-going star formation as indicated by the lack of [OII] or H$\alpha$ emission lines. Therefore, E+A galaxies are interpreted as a post-starburst galaxy – a galaxy which truncated starburst suddenly. However, for more than 20 years, the origin of this post-starburst phenomena remained a mystery. Using the 100,000 galaxy spectra of the Sloan Digital Sky Survey Data Release 1, we tested three popular explanations to the E+A phenomenon.