A low-ionization nuclear emission-line region (LINER) is a type of galactic nucleus that is defined by its spectral line emission. The spectra typically include line emission from weakly ionized or neutral atoms, such as O, O+, N+, and S+. Conversely, the spectral line emission from strongly ionized atoms, such as O++, Ne++, and He+, is relatively weak. The class of galactic nuclei was first identified by Timothy Heckman in the third of a series of papers on the spectra of galactic nuclei that were published in 1980.
Read more about Low-ionization Nuclear Emission-line Region: Demographics of LINER Galaxies, Scientific Debates: Energy Sources and Ionization Mechanisms, Star Formation in LINERs, Notable LINER Galaxies
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