Seyfert Galaxies

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.

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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 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.
Seyfert Galaxy Images 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.
Seyfert 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.
Seyfert Galaxies Review Department of Radio and Space Science with Onsala Space Observatory Chalmers University of Technology, Göteborg, Sweden
Observations of Seyfert galaxies Of the two types of Active Galactic Nuclei (AGN) which emit gamma-rays, Seyfert galaxies are the low-energy gamma sources.
The 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 Seyferts
Seyfert 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.
Seyfert galaxy encyclopedia of science A galaxy with a small, intensely bright nucleus which shows strong, broad emission lines.
Seyfert galaxy encyclopedia britannica any of a class of galaxies known to have active nuclei.
Surface Photometry of Seyfert Galaxies A subarcsecond resolution near-infrared study of Seyfert and 'normal' galaxies.
Sey'fert gal"axy Pronunciation: (si-'furt, 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.
The Astrophysical Journal Letters. The Close Environment of Seyfert Galaxies and Its Implication for Unification Models
A 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.
Closeup 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.
Composite 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.
NGC 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.
An 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...
A 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.
The 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.
Galaxy, 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
The 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 obscuring torus.
Seyfert 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.
Seyfert 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.
Seyfert 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.
Jet-Gas 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 ...
Seyfert 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.
Smithsonian/NASA ADS Astronomy Abstract Service The Seyfert galaxy population - A radio survey; luminosity functions, related objects
Seyfert 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.
Probing Local Seyfert Galaxies: (PDF) Results obtained from an X-ray survey of a complete
sample of Seyfert galaxies using XMM-Newton and
Chandra are reported.
The Interplay among Black Holes, Stars and ISM in Galactic Nuclei HI observations of nearby southern Seyfert galaxies with the ATNF/Mopra radiotelescope
Visibility 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 galaxies—the most common examples of nearby active galaxies—are separated into two classes based on their emission line widths.
Evolutionary 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).
Velocity 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 other methods.
The 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 0.5–2 keV band larger than 1.2×10-15 erg cm-2 s-1, where over 75% of the sources are quasars or Seyfert galaxies.
Optical 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
University 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 lines.
Study 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.

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J. Michael Seyfert