Published in "The Physics of LINERs
in View of Recent Observations", ed. M. Eracleous, A. P. Koratkar,
C. Leitherer, & L. C. Ho (San Francisco: ASP), 1996, p.103.
For a PDF version of the article, click
here.
OPTICAL SPECTROSCOPY OF LINERS AND LOW-LUMINOSITY SEYFERT
NUCLEI
Luis C. Ho
Harvard-Smithsonian Center for Astrophysics, 60
Garden St., MS-42, Cambridge, MA 02138, U.S.A.
ABSTRACT. An unprecedentedly large number of LINERs has been
discovered in a recently
completed optical spectroscopic survey of nearby galaxies, allowing several
statistical properties of the host galaxies and of the line-emitting
regions to be examined reliably for the first time. As a consequence of
the many detections and some revised classifications, the detailed
demographics of emission-line nuclei have been updated from those given in
older surveys. Consistent with previous studies, it is found that LINERs
are extremely common in the present
epoch, comprising approximately 1/3 of all galaxies with
BT 
12.5 mag.
If all LINERs are nonstellar in origin, then they are the dominant
constituents of the active galactic nucleus population. Many fundamental
characteristics of LINERs closely resemble those of low-luminosity
Seyfert nuclei, although several aspects of their narrow-line regions
appear to differ in a systematic
manner. These differences could hold important clues to the key parameters
controlling the ionization level in active nuclei. Lastly, a substantial
fraction of LINERs has been found to contain a broad-line region, yielding
direct evidence, at least in these objects, of a physical link between
LINERs and classical Seyfert 1 nuclei and QSOs.
Table of Contents
EMISSION