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[
Joint Center for Astrophysics]
The AGN Zoo
Active Galactic Nuclei (AGN)
come in a wide
variety of types (or classes) based primarily on their observational
characteristics, although in a number of cases the differences are rather
subtle, partial-overlapping and/or historical.
Index:
Blazars,
LINERs,
Quasars,
Radio Galaxies,
Seyfert Galaxies
A collective term for
BL Lacertae type Objects [BL Lacs]
and
Optically-Violent Variables [OVVs]
See also:
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Low-ionization Nuclear Emission-Line Region
See also:
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High-luminosity AGN.
Historically also referred to
as Quasi-stellar Objects [QSOs]
and Quasi-stellar Radio Sources [QSRS], but these
distinctions and usages have not commonly used now.
Since the relative strength of the radio emission appears
fairly bi-modal, usually divided into
Radio-loud Quasars
[RLQs]
(relatively strong radio emission)
and
Radio-quiet Quasars
[RQQs]
(relatively weak radio emission)
See also:
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Fanaroff-Riley type 1 [FR1s]
and
Fanaroff-Riley type 2 [FR2s]
.
Also
Broad-Line Radio Galaxies [BLRGs]
and
Narrow-Line Radio Galaxies [NLRGs]
See also:
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Named after Carl Seyfert who first published a list of 12
galaxies which showed bright, point-like nuclei and
strong, broad emission lines from high-excitation
species (Seyfert 1943). Primarily Spiral Galaxies.
Usually divided
into two main sub-classes based on the characteristics of
their optical emission lines:
Seyfert 1 Galaxies
(broad & narrow lines present),
and
Seyfert 2 Galaxies
(narrow lines only present).
However finer
sub-sub-classes are usually used
to distinguish the subtle differences.
See also:
An overview of Seyfert Galaxies,
X-ray Observations of Seyfert 1 Galaxies
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