Almost all Seyfert galaxies are
spiral galaxies and have been among the most intensively studied
objects in astronomy, primarily because they are thought to be nearby,
low-luminosity versions of the same phenomenon observed in quasars.
A massive black hole in the nucleus of a galaxy, accreting gas from
its surrounding environment, is thought to power all these objects.
Of course, we do not see the black hole itself, but the UV continuum
radiation is generally presumed to be thermal emission from the
hot gas that forms an accretion disk surrounding the black hole.
Seyfert galaxies, which amount to 10% of all galaxies, produce
nuclei spectral line emissions from highly ionized gas.
These galaxies are named after Carl Keenan Seyfert>, who identified
this galaxy class in 1943. Seyferts are a subclass of active galactic
nuclei and it is thought they contain extremely large black holes.
||Seyfert galaxies have been among the
most intensively studied objects in astronomy, primarily because they
are thought to be nearby, low-luminosity versions of the same phenomenon
observed in quasars.
||This montage uses ground-based wide-field
images to exhibit the variety of types and environments in which Seyfert
are found. Of these, IC 4329A, NGC 3516, and Markarian 279 are type
1 Seyferts, NGC 3786 is an intermediate "type 1.5" nucleus",
and NGC 5728 and NGC 7674 are type 2 objects.
Galaxy NGC 7742
||This might resemble a fried egg you've
had for breakfast, but it's actually much larger. In fact, ringed
by blue-tinted star forming regions and faintly visible spiral arms,
the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is
about 3,000 light-years across.
||Department of Radio and
Space Science with Onsala Space Observatory
Chalmers University of Technology, Göteborg, Sweden
of Seyfert galaxies
||Of the two types of Active
Galactic Nuclei (AGN) which emit gamma-rays, Seyfert galaxies are
the low-energy gamma sources.
Hubble telescope Seyfert
||The Hubble telescope
has taken a snapshot of a nearby active galaxy known as Circinus.
This active galaxy belongs to a class of mostly spiral galaxies called
galaxy on Free Dictionary
||Galaxy in which a small,
bright centre is caused by hot gas moving at high speed around a massive
central object, possibly a black hole.
galaxy encyclopedia of science
|| A galaxy with a small,
intensely bright nucleus which shows strong, broad emission lines.
galaxy encyclopedia britannica
|| any of a class of galaxies
known to have active nuclei.
Photometry of Seyfert Galaxies
||A subarcsecond resolution
near-infrared study of Seyfert and 'normal' galaxies.
se-'-), [key] Astron. one of a group of spiral galaxies with compact,
bright nuclei having characteristically broad emission lines suggestive
of very hot gases in violent motion at the center.
Astrophysical Journal Letters.
||The Close Environment
of Seyfert Galaxies and Its Implication for Unification Models
Selection of Seyfert Galaxies
||This montage uses ground-based
wide-field images to exhibit the variety of types and environments
in which Seyfert are found.
views of Seyfert nuclei from HST
||Seyfert galaxies were
originally noted as having unusually bright, compact (starlike) nuclei.
The surroundings of this brilliant nucleus can take a variety of forms,
perhaps carrying clues to how the central engine is fed or triggered.
emission-line spectrum of NGC 4151
||Seyfert galaxies were
originally noted for the strength and broadening of their emission
lines, and as a class were later characterized by the high ionization
states of many of the atomic and ionized species producing these lines.
1275 H-alpha filaments
||One of the most curious
of Seyfert's original sample of galaxies remains NGC 1275, which has
some of the properties associated with Seyfert nuclei, radio galaxies,
and even BL Lacertae objects.
HST view of the enigmatic spectacle NGC 1275
||What's going on here?
In fact, how many different things are going on here? NGC 1275 has
been called, at various times and not always by different astronomers,
a Seyfert galaxy, radio galaxy, and even blazar...
hidden AGN - infrared images of IC 5063
||While many active nuclei
announce their presence from a tiny, intense source of blue and ultraviolet
light, some are hidden from our view by intervening dust - either
surrounding the central engine or happening to lie somewhere else
in front of it.
interaction of jets and clouds in NGC 4151
||These images both depict
the same area - the region of ionized gas around the nucleus of the
bright Seyfert galaxy NGC 4151.
jet, and obscuring disk in NGC 1068
||Measurements of the polarization
of the light near the nucleus of NGC 1068, a nearby and prototypical
type 2 Seyfert, provided strong evidence that it actually contain
a type 1 nucleus which is blocked from our direct view by an obscuring
ring or torus of material
hidden nucleus of NGC 1068 revealed by polarization
||A crucial development
in understanding Seyfert galaxies came with the recognition that at
least some type 2 Seyfert nuclei are in fact type 1 objects for which
our view of the innermost region is blocked by a dust- and gas-rich
galaxy NGC 1068
||The well-known Seyfert
(and starburst) galaxy NGC 1068 (Messier 77) in Cetus, in a three-color
reconstruction from BVR CCD images taken with the 1.1-meter Hall telescope
at Lowell Observatory.
Galaxy NGC 5548 versus normal galaxy NGC 3277
||Seyfert galaxies (especially
type 1 Seyferts) can have nuclei which stand out, even at the eyepiece,
as unusually bright and compact.
Galaxies & Active Galaxies
||When examined spectroscopically,
galaxies are generally found to have absorption features similar to
those found in stars. This is what one would expect for the integrated
light of a population of normal stars. However, in 1943 Carl Seyfert
identified a class of spiral galaxies (later given the name ``Seyfert''
galaxies) which exhibit broad forbidden emission lines of [O II],
[O III], [N II], [Ne III], [S II], and [S III], coming from unusually
bright central regions.
Interactions in Seyfert Galaxies (PowerPoint)
||Case study of Seyfert
Galaxy : Mkn 78. Observations & data overview. Heuristic description
of JGI. Ionization analysis. Dynamical analysis. Active Galaxies ...
Galaxies - Department of Astronomy University of Maryland
||Seyfert Galaxies are
spiral galaxies with unusually bright, tiny cores that fluctuate in
brightness. They do not have radio lobes. Most are powerful sources
of infrared radiation.
ADS Astronomy Abstract Service
||The Seyfert galaxy population
- A radio survey; luminosity functions, related objects
Galaxies and the Hard X-ray Background: Artificial Chandra Observations
of z = 0.3 Active Galaxies
||Deep X-ray surveys have
resolved much of the X-ray background radiation below 2 keV into discrete
sources, but the background above 8 keV remains largely unresolved.
Local Seyfert Galaxies: (PDF)
||Results obtained from an X-ray survey of
sample of Seyfert galaxies using XMM-Newton and
Chandra are reported.
Interplay among Black Holes, Stars and ISM in Galactic Nuclei
||HI observations of nearby
southern Seyfert galaxies with the ATNF/Mopra radiotelescope
of scattered broad-line emission in Seyfert 2 galaxies
||Active galaxies are thought to be powered
by the accretion of gas onto a central massive black hole. Seyfert
galaxiesthe most common examples of nearby active galaxiesare
separated into two classes based on their emission line widths.
sequence of Seyfert galaxies
||We suggest that there exists an evolutionary
sequence from Seyfert 2 to Seyfert 1 galaxies. We review observations
which support this suggestion and the idea that the main parameter
is the dust content in and around the Broad Line Region (BLR).
Dispersion and Black Hole Mass in Seyfert 1 Galaxies (Adobe PostScript)
||Bulge stellar velocity
dispersions, , in Seyfert 1 galaxies are combined with the M relation
to validate reverberation mapping as a means of determining nuclear
black hole masses. Seyfert galaxies follow the same relation as non-active
galaxies, indicating that reverberation mapping is consistent with
contribution of narrow-line Seyfert 1 galaxies to the soft X-ray background
||The ROSAT Ultradeep HRI survey in the Lockman
Hole contains a complete sample of 91 X-ray sources with fluxes in
the 0.52 keV band larger than 1.2×10-15 erg cm-2 s-1,
where over 75% of the sources are quasars or Seyfert galaxies.
Emission-Line Spectra of Seyfert Galaxies and Radio Galaxies
||Abstract. Many radio galaxies have strong
emission lines in their optical spectra, similar to the emission lines
in the spectra of Seyfert galaxies
of California, San Diego
Center for Astrophysics & Space Sciences
|In 1943, astronomer Carl Seyfert noticed
that certain nearby spiral galaxies have very bright, pinpoint nuclei.
Spectra of these galaxies, now named Seyfert galaxies, showed that
they have unusual spectra with very strong, often broad, emission
Stirs Old Debate about Galaxies
||Using a technique that peeks over obscuring
rings of dust and gas and into the hearts of distant galaxies, a researcher
has found evidence suggesting that as many as half of the bright,
active galaxies known as Seyfert 2 galaxies may have significantly
less active central black holes.