The term emission line galaxy (ELG) is used for galaxies showing emission lines, one of a number of terms used for distant galaxies (i.e., with significant redshift) to characterize them by spectral features. Other such classification terms are absorption line galaxy and A+E galaxy (featuring both). Emission lines are indicative of star formation, e.g., a starburst galaxy. The emission lines can be useful in assisting with redshift determination, e.g., confirming the distance to some of the most-distant/oldest galaxies. Some typical emission lines are:
The term extreme emission line galaxy (EELG) is also used, for those with especially bright emission lines.