The Ionization Mechanism of Low Ionization Nuclear
Emission Line Regions (LINERs) in Active Galaxies
Dr. Jack Gabel
The Catholic University of America and
NASA's Goddard Space Flight Center
Greenbelt, MD
Since the identification of low ionization nuclear emission line regions
(LINERs) as a distinct class of galactic nuclei by Heckman (1980), their
basic physical nature has been the subject of much study and debate.
While
the ionization mechanism in the majority of LINERs is presently unknown,
recent multi-wavelength observations and modeling results indicate that
at least a subset of LINERs are genuine low-luminosity AGNs. I will
begin with an overview of the properties of LINERs, comparing them with
other classes of emission line nuclei (AGNs and H II regions). Focusing
on LINERs that are now believed to be AGNs, I will explore the physical
differences between AGN LINERs and Seyferts that may lead to their distinct
spectra. As a case study, I will present results of a detailed analysis
of the prototypical LINER galaxy NGC 1052. Finally, I will review
recent theories that employ different accretion mechanisms for LINERs and
other low luminosity AGNs.