The Chemical Evolution of Narrow Emission Line Galaxies: the Key to   their Formation Processes
  Using the largest sample of narrow emission line galaxies available so far, we show that their spectral characteristics are correlated with different physical parameters, like the chemical abundances, the morphologies, the masses of the bulge and the mean stellar age of the stellar populations of the host galaxies. It suggests that the spectral variations observed in standard spectroscopic diagnostic diagrams are not due solely to variations of ionization parameters or structures but reflect also the chemical evolution of the galaxies, which in turn can be explained by different galaxy formation processes. 
J. P. Torres-Papaqui, R. Coziol, and R. A. Ortega-Minakata
astro-ph.CO astro-ph.GA