Active galactic nucleus - Knowledge (XXG)

633:. These objects show nuclear and extended radio emission. Their other AGN properties are heterogeneous. They can broadly be divided into low-excitation and high-excitation classes. Low-excitation objects show no strong narrow or broad emission lines, and the emission lines they do have may be excited by a different mechanism. Their optical and X-ray nuclear emission is consistent with originating purely in a jet. They may be the best current candidates for AGN with radiatively inefficient accretion. By contrast, high-excitation objects (narrow-line radio galaxies) have emission-line spectra similar to those of Seyfert 2s. The small class of broad-line radio galaxies, which show relatively strong nuclear optical continuum emission probably includes some objects that are simply low-luminosity radio-loud quasars. The host galaxies of radio galaxies, whatever their emission-line type, are essentially always ellipticals. 595:/QSOs. These are essentially more luminous versions of Seyfert 1s: the distinction is arbitrary and is usually expressed in terms of a limiting optical magnitude. Quasars were originally 'quasi-stellar' in optical images as they had optical luminosities that were greater than that of their host galaxy. They always show strong optical continuum emission, X-ray continuum emission, and broad and narrow optical emission lines. Some astronomers use the term QSO (Quasi-Stellar Object) for this class of AGN, reserving 'quasar' for radio-loud objects, while others talk about radio-quiet and radio-loud quasars. The host galaxies of quasars can be spirals, irregulars or ellipticals. There is a correlation between the quasar's luminosity and the mass of its host galaxy, in that the most luminous quasars inhabit the most massive galaxies (ellipticals). 627:) classes are distinguished by rapidly variable, polarized optical, radio and X-ray emission. BL Lac objects show no optical emission lines, broad or narrow, so that their redshifts can only be determined from features in the spectra of their host galaxies. The emission-line features may be intrinsically absent or simply swamped by the additional variable component. In the latter case, emission lines may become visible when the variable component is at a low level. OVV quasars behave more like standard radio-loud quasars with the addition of a rapidly variable component. In both classes of source, the variable emission is believed to originate in a relativistic jet oriented close to the line of sight. Relativistic effects amplify both the luminosity of the jet and the amplitude of variability. 1067:

narrow-line radio galaxies show no nuclear optical continuum or reflected X-ray component, although they do occasionally show polarized broad-line emission). The large-scale radio structures of these objects provide compelling evidence that the orientation-based unified models really are true. X-ray evidence, where available, supports the unified picture: radio galaxies show evidence of obscuration from a torus, while quasars do not, although care must be taken since radio-loud objects also have a soft unabsorbed jet-related component, and high resolution is necessary to separate out thermal emission from the sources' large-scale hot-gas environment. At very small angles to the line of sight, relativistic beaming dominates, and we see a blazar of some variety.

588:. Seyferts were the earliest distinct class of AGN to be identified. They show optical range nuclear continuum emission, narrow and occasionally broad emission lines, occasionally strong nuclear X-ray emission and sometimes a weak small-scale radio jet. Originally they were divided into two types known as Seyfert 1 and 2: Seyfert 1s show strong broad emission lines while Seyfert 2s do not, and Seyfert 1s are more likely to show strong low-energy X-ray emission. Various forms of elaboration on this scheme exist: for example, Seyfert 1s with relatively narrow broad lines are sometimes referred to as narrow-line Seyfert 1s. The host galaxies of Seyferts are usually spiral or irregular galaxies. 1096:

neighbours of hundreds to thousands of AGN have shown that the neighbours of Seyfert 2s are intrinsically dustier and more star-forming than Seyfert 1s and a connection between AGN type, host galaxy morphology and collision history. Moreover, angular clustering studies of the two AGN types confirm that they reside in different environments and show that they reside within dark matter halos of different masses. The AGN environment studies are in line with evolution-based unification models where Seyfert 2s transform into Seyfert 1s during merger, supporting earlier models of merger-driven activation of Seyfert 1 nuclei.

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purely from a jet, with no heavily absorbed nuclear component in general. These objects cannot be unified with quasars, even though they include some high-luminosity objects when looking at radio emission, since the torus can never hide the narrow-line region to the required extent, and since infrared studies show that they have no hidden nuclear component: in fact there is no evidence for a torus in these objects at all. Most likely, they form a separate class in which only jet-related emission is important. At small angles to the line of sight, they will appear as BL Lac objects.

504:, the accreting matter does not form a thin disc and consequently does not efficiently radiate away the energy that it acquired as it moved close to the black hole. Radiatively inefficient accretion has been used to explain the lack of strong AGN-type radiation from massive black holes at the centres of elliptical galaxies in clusters, where otherwise we might expect high accretion rates and correspondingly high luminosities. Radiatively inefficient AGN would be expected to lack many of the characteristic features of standard AGN with an accretion disc. 4813: 472:, and fast outflows that emerge in opposite directions from close to the disc. The direction of the jet ejection is determined either by the angular momentum axis of the accretion disc or the spin axis of the black hole. The jet production mechanism and indeed the jet composition on very small scales are not understood at present due to the resolution of astronomical instruments being too low. The jets have their most obvious observational effects in the radio waveband, where 1032: 5643: 4666: 4678: 582:(LINERs). As the name suggests, these systems show only weak nuclear emission-line regions, and no other signatures of AGN emission. It is debatable whether all such systems are true AGN (powered by accretion on to a supermassive black hole). If they are, they constitute the lowest-luminosity class of radio-quiet AGN. Some may be radio-quiet analogues of the low-excitation radio galaxies (see below). 5653: 3869: 1054:

some of the nuclear emission into our line of sight, allowing us to see some optical and X-ray continuum and, in some cases, broad emission lines—which are strongly polarized, showing that they have been scattered and proving that some Seyfert 2s really do contain hidden Seyfert 1s. Infrared observations of the nuclei of Seyfert 2s also support this picture.

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hidden broad-line region and thus split Seyfert 2 galaxies into two populations. The two classes of populations appear to differ by their luminosity, where the Seyfert 2s without a hidden broad-line region are generally less luminous. This suggests absence of broad-line region is connected to low Eddington ratio, and not to obscuration.

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availability of cold gas near the centre of galaxies than at present. It also implies that many objects that were once luminous quasars are now much less luminous, or entirely quiescent. The evolution of the low-luminosity AGN population is much less well understood due to the difficulty of observing these objects at high redshifts.

445: 310:, at a cosmological distance) then its large redshift of 0.158 implied that it was the nuclear region of a galaxy about 100 times more powerful than other radio galaxies that had been identified. Shortly afterward, optical spectra were used to measure the redshifts of a growing number of quasars including 1103:

While it still might be valid that an obscured Seyfert 1 can appear as a Seyfert 2, not all Seyfert 2s must host an obscured Seyfert 1. Understanding whether it is the same engine driving all Seyfert 2s, the connection to radio-loud AGN, the mechanisms of the variability of some AGN that vary between

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It is convenient to divide AGN into two classes, conventionally called radio-quiet and radio-loud. Radio-loud objects have emission contributions from both the jet(s) and the lobes that the jets inflate. These emission contributions dominate the luminosity of the AGN at radio wavelengths and possibly

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While studies of single AGN show important deviations from the expectations of the unified model, results from statistical tests have been contradictory. The most important short-coming of statistical tests by direct comparisons of statistical samples of Seyfert 1s and Seyfert 2s is the introduction

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Unified models propose that different observational classes of AGN are a single type of physical object observed under different conditions. The currently favoured unified models are 'orientation-based unified models' meaning that they propose that the apparent differences between different types of

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During the first half of the 20th century, photographic observations of nearby galaxies detected some characteristic signatures of AGN emission, although there was not yet a physical understanding of the nature of the AGN phenomenon. Some early observations included the first spectroscopic detection

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of obscuring material surrounding the accretion disc. It must be large enough to obscure the broad-line region but not large enough to obscure the narrow-line region, which is seen in both classes of object. Seyfert 2s are seen through the torus. Outside the torus there is material that can scatter

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Ananna, Tonima Tasnim; Weigel, Anna K.; Trakhtenbrot, Benny; Koss, Michael J.; Urry, C. Megan; Ricci, Claudio; Hickox, Ryan C.; Treister, Ezequiel; Bauer, Franz E.; Ueda, Yoshihiro; Mushotzky, Richard; Ricci, Federica; Oh, Kyuseok; Mejía-Restrepo, Julian E.; Brok, Jakob Den; Stern, Daniel; Powell,

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introduced Active Galactic Nuclei in the early 1950s. At the Solvay Conference on Physics in 1958, Ambartsumian presented a report arguing that "explosions in galactic nuclei cause large amounts of mass to be expelled. For these explosions to occur, galactic nuclei must contain bodies of huge mass

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Studying neighbour galaxies rather than the AGN themselves first suggested the numbers of neighbours were larger for Seyfert 2s than for Seyfert 1s, in contradiction with the Unified Model. Today, having overcome the previous limitations of small sample sizes and anisotropic selection, studies of

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The covering factor of the torus might play an important role. Some torus models predict how Seyfert 1s and Seyfert 2s can obtain different covering factors from a luminosity and accretion rate dependence of the torus covering factor, something supported by studies in the x-ray of AGN. The models

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At higher luminosities, quasars take the place of Seyfert 1s, but, as already mentioned, the corresponding 'quasar 2s' are elusive at present. If they do not have the scattering component of Seyfert 2s they would be hard to detect except through their luminous narrow-line and hard X-ray emission.

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A study of Swift/BAT AGN published in July 2022 adds support to the "radiation-regulated unification model" outlined in 2017. In this model, the relative accretion rate (termed the "Eddington ratio") of the black hole has a significant impact on the observed features of the AGN. Black Holes with

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Therefore, one cannot know whether the gas in all Seyfert 2 galaxies is ionized due to photoionization from a single, non-stellar continuum source in the center or due to shock-ionization from e.g. intense, nuclear starbursts. Spectropolarimetric studies reveal that only 50% of Seyfert 2s show a

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However, the population of radio galaxies is completely dominated by low-luminosity, low-excitation objects. These do not show strong nuclear emission lines—broad or narrow—they have optical continua which appear to be entirely jet-related, and their X-ray emission is also consistent with coming

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At low luminosities, the objects to be unified are Seyfert galaxies. The unification models propose that in Seyfert 1s the observer has a direct view of the active nucleus. In Seyfert 2s the nucleus is observed through an obscuring structure which prevents a direct view of the optical continuum,

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Most luminous classes of AGN (radio-loud and radio-quiet) seem to have been much more numerous in the early universe. This suggests that massive black holes formed early on and that the conditions for the formation of luminous AGN were more common in the early universe, such as a much higher

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Ricci, Claudio; Trakhtenbrot, Benny; Koss, Michael J.; Ueda, Yoshihiro; Schawinski, Kevin; Oh, Kyuseok; Lamperti, Isabella; Mushotzky, Richard; Treister, Ezequiel; Ho, Luis C.; Weigel, Anna; Bauer, Franz E.; Paltani, Stephane; Fabian, Andrew C.; Xie, Yanxia; Gehrels, Neil (2017). "The close

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Historically, work on radio-loud unification has concentrated on high-luminosity radio-loud quasars. These can be unified with narrow-line radio galaxies in a manner directly analogous to the Seyfert 1/2 unification (but without the complication of much in the way of a reflection component:

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also suggest an accretion-rate dependence of the broad-line region and provide a natural evolution from more active engines in Seyfert 1s to more "dead" Seyfert 2s and can explain the observed break-down of the unified model at low luminosities and the evolution of the broad-line region.

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In the recent literature on AGN, being subject to an intense debate, an increasing set of observations appear to be in conflict with some of the key predictions of the Unified Model, e.g. that each Seyfert 2 has an obscured Seyfert 1 nucleus (a hidden broad-line region).

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objects known either in the optical or the radio spectrum, because of their high luminosity. They still have a role to play in studies of the early universe, but it is now recognised that an AGN gives a highly biased picture of the "typical" high-redshift galaxy.

598:'Quasar 2s'. By analogy with Seyfert 2s, these are objects with quasar-like luminosities but without strong optical nuclear continuum emission or broad line emission. They are scarce in surveys, though a number of possible candidate quasar 2s have been identified. 611:

Radio-loud quasars behave exactly like radio-quiet quasars with the addition of emission from a jet. Thus they show strong optical continuum emission, broad and narrow emission lines, and strong X-ray emission, together with nuclear and often extended radio

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While controversy about the soundness of each individual study still prevails, they all agree on that the simplest viewing-angle based models of AGN Unification are incomplete. Seyfert-1 and Seyfert-2 seem to differ in star formation and AGN engine power.

407:. Dissipative processes in the accretion disc transport matter inwards and angular momentum outwards, while causing the accretion disc to heat up. The expected spectrum of an accretion disc peaks in the optical-ultraviolet waveband; in addition, a 333:

proposed that nearby galaxies contain supermassive black holes at their centers as relics of "dead" quasars, and that black hole accretion was the power source for the non-stellar emission in nearby Seyfert galaxies. In the 1960s and 1970s, early

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broad-line region or (soft) X-ray emission. The key insight of orientation-dependent accretion models is that the two types of object can be the same if only certain angles to the line of sight are observed. The standard picture is of a

349:. AGN research encompasses observational surveys to find AGN over broad ranges of luminosity and redshift, examination of the cosmic evolution and growth of black holes, studies of the physics of black hole accretion and the emission of 377:, and as a result, it can provide the observed high persistent luminosity. Supermassive black holes are now believed to exist in the centres of most if not all massive galaxies since the mass of the black hole correlates well with the 569:

AGN terminology is often confusing, since the distinctions between different types of AGN sometimes reflect historical differences in how the objects were discovered or initially classified, rather than real physical differences.

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Wang, J. M.; Du, P.; Baldwin, J. A.; Ge, J-Q.; Ferland, G. J.; Ferland, Gary J. (2012). "Star formation in self-gravitating disks in active galactic nuclei. II. Episodic formation of broad-line regions".

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the two types at very short time scales, and the connection of the AGN type to small and large-scale environment remain important issues to incorporate into any unified model of active galactic nuclei.

1576: 373:). AGN are both compact and persistently extremely luminous. Accretion can potentially give very efficient conversion of potential and kinetic energy to radiation, and a massive black hole has a high 208:

published a paper in which he described observations of nearby galaxies having bright nuclei that were sources of unusually broad emission lines. Galaxies observed as part of this study included

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The observed characteristics of an AGN depend on several properties such as the mass of the central black hole, the rate of gas accretion onto the black hole, the orientation of the

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Padovani, P.; Alexander, D. M.; Assef, R. J.; De Marco, B.; Giommi, P.; Hickox, R. C.; Richards, G. T.; Smolčić, V.; Hatziminaoglou, E.; Mainieri, V.; Salvato, M. (November 2017).

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and unknown nature. From this point forward Active Galactic Nuclei (AGN) became a key component in theories of galactic evolution." His idea was initially accepted skeptically.

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The enormous luminosities of these quasars as well as their unusual spectral properties indicated that their power source could not be ordinary stars. Accretion of gas onto a

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observations demonstrated that Seyfert galaxies and quasars are powerful sources of X-ray emission, which originates from the inner regions of black hole accretion disks.

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sources associated with the radio emission. In photographic images, some of these objects were nearly point-like or quasi-stellar in appearance, and were classified as

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There exists a class of "radiatively inefficient" solutions to the equations that govern accretion. Several theories exist, but the most widely known of these is the

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Garrington, S. T.; Leahy, J. P.; Conway, R. G.; Laing, R. A. (1988). "A systematic asymmetry in the polarization properties of double radio sources with one jet".

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Laing, R. A.; Jenkins, C. R.; Wall, J. V.; Unger, S. W. (1994). "Spectrophotometry of a Complete Sample of 3CR Radio Sources: Implications for Unified Models".

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in the universe and, as such, can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on

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up to X-ray energies. The radiation from the accretion disc excites cold atomic material close to the black hole and this in turn radiates at particular

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Donoso, E.; Yan, L.; Stern, D.; Assef, R. J. (2014). "The Angular Clustering of WISE-Selected AGN: Different Haloes for Obscured and Unobscured AGN".

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Baum, S. A.; Zirbel, E. L.; O'Dea, Christopher P. (1995). "Toward Understanding the Fanaroff-Riley Dichotomy in Radio Source Morphology and Power".

1657: 3395:; Krongold, Y.; Fuentes-Guridi, I.; Marziani, P. (1999). "The Close Environment of Seyfert Galaxies and Its Implication for Unification Models". 353:

from AGN, examination of the properties of jets and outflows of matter from AGN, and the impact of black hole accretion and quasar activity on

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Chiaberge, M.; Capetti, A.; Celotti, A. (2002). "Understanding the nature of FRII optical nuclei: a new diagnostic plane for radio galaxies".

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at some or all other wavelengths. Radio-quiet objects are simpler since jet and any jet-related emission can be neglected at all wavelengths.

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higher Eddington ratios appear to be more likely to be unobscured, having cleared away locally obscuring material in a very short timescale.

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close to the accretion disc, but (in a steady-state situation) this will be re-radiated at some other waveband, most likely the infrared.

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Vermeulen, R. C.; Ogle, P. M.; Tran, H. D.; Browne, I. W. A.; Cohen, M. H.; Readhead, A. C. S.; Taylor, G. B.; Goodrich, R. W. (1995).

5255: 4520: 497: 385:) or with bulge luminosity. Thus, AGN-like characteristics are expected whenever a supply of material for accretion comes within the 123:

Numerous subclasses of AGN have been defined on the basis of their observed characteristics; the most powerful AGN are classified as

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Ricci, C.; Walter, R.; Courvoisier, T. J-L.; Paltani, S. (2010). "Reflection in Seyfert galaxies and the unified model of AGN".

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of 3C 273 appears to the left of the bright quasar, and the four straight lines pointing outward from the central source are

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Ogle, P.; Whysong, D.; Antonucci, R. (2006). "Spitzer Reveals Hidden Quasar Nuclei in Some Powerful FR II Radio Galaxies".

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Baade, Walter; Minkowski, Rudolph (1954). "Identification of the Radio Sources in Cassiopeia, Cygnus A, and Puppis A.".

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Wu, Y-Z; et al. (2001). "The Different Nature in Seyfert 2 Galaxies With and Without Hidden Broad-line Regions".

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objects arise simply because of their different orientations to the observer. However, they are debated (see below).

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Marconi, A.; L. K. Hunt (2003). "The Relation between Black Hole Mass, Bulge Mass, and Near-Infrared Luminosity".

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Nicastro, F. (2000). "Broad Emission Line Regions in Active Galactic Nuclei: The Link with the Accretion Power".

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Meredith C.; Caglar, Turgay; Ichikawa, Kohei; Wong, O. Ivy; Harrison, Fiona A.; Schawinski, Kevin (2022-07-01).

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Villarroel, B.; Korn, A. J. (2014). "The different neighbours around Type-1 and Type-2 active galactic nuclei".

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Curtis, Heber D. (1918). "Descriptions of 762 Nebulae and Clusters Photographed with the Crossley Reflector".

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Laing, R. A. (1988). "The sidedness of jets and depolarization in powerful extragalactic radio sources".

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was a major catalyst to understanding AGN. Some of the earliest detected radio sources are nearby active

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Villarroel, B.; Nyholm, A.; Karlsson, T.; Comeron, S.; Korn, A.; Sollerman, J.; Zackrisson, E. (2017).

1134: 382: 3730:"BASS. XXX. Distribution Functions of DR2 Eddington Ratios, Black Hole Masses, and X-Ray Luminosities" 5646: 5354: 5326: 5209: 5137: 4949: 4757: 4702: 4641: 4591: 4426: 4338: 4074: 3958: 3894: 3815: 3751: 3691: 3634: 3577: 3524: 3471: 3414: 3374: 3347: 3294: 3239: 3182: 3129: 3075: 3014: 2961: 2908: 2855: 2808: 2761: 2706: 2657: 2614: 2571: 2528: 2483: 2448: 2403: 2343: 2295: 2268: 2231: 2190: 2141: 2033: 1974: 1921: 1868: 1825: 1782: 1729: 1684: 1510: 1465: 1426: 1389: 1340: 1299: 1268: 1241: 1196: 480:

scales. However, they radiate in all wavebands from the radio through to the gamma-ray range via the

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Antonucci, R. (2012). "A panchromatic review of thermal and nonthermal active galactic nuclei".

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is an AGN with a jet pointed toward the Earth, in which radiation from the jet is enhanced by

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process, and so AGN jets are a second potential source of any observed continuum radiation.

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Greenstein, J. L.; Matthews, T. A. (1963). "Red-Shift of the Unusual Radio Source: 3C 48".

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500:(ADAF). In this type of accretion, which is important for accretion rates well below the 5528: 3819: 3755: 3695: 3638: 3581: 3528: 3475: 3418: 3298: 3243: 3186: 3133: 3018: 2965: 2912: 2859: 2812: 2765: 2710: 2661: 2618: 2575: 2532: 2495: 2452: 2407: 2299: 2272: 2235: 2194: 2145: 2037: 1978: 1925: 1872: 1829: 1786: 1733: 1688: 1514: 1469: 1430: 1393: 1344: 1303: 1272: 1245: 1208: 1200: 1137: – Relationship between the mass of a galaxy bulge and the mass of the supermassive 5543: 5295: 5234: 5078: 4752: 4394: 4227: 4130: 4125: 4079: 4022: 3163:

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led to further progress in discovery of new radio sources as well as identifying the

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environments of accreting massive black holes are shaped by radiative feedback".

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Petrosian, Artashes R.; Harutyunian, Haik A.; Mickaelian, Areg M. (June 1997).

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can be used to study the synchrotron radiation they emit at resolutions of sub-

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Grandi, S. A.; Osterbrock, D. E. (1978). "Optical spectra of radio galaxies".

2244: 2219: 2096: 2046: 2009: 951: 624: 469: 457: 453: 370: 240: 185: 177: 46:, with characteristics indicating that this luminosity is not produced by the 3835: 3773: 2104: 1217: 204:

noted the presence of unusual emission lines in some galaxy nuclei. In 1943,

5623: 5270: 5173: 4961: 4956: 4358: 3252: 3217: 2154: 536: 307: 192:(published in 1918). Further spectroscopic studies by astronomers including 98: 75: 55: 3843: 3034: 1541:"Obituary: Victor Amazaspovich Ambartsumian, 1912 [i.e. 1908]–1996" 1454:"Positions of Three Discrete Sources of Galactic Radio-Frequency Radiation" 403:

In the standard model of AGN, cold material close to a black hole forms an

3868: 2010:"The accretion luminosity of a massive black hole in an elliptical galaxy" 5533: 5492: 5390: 3629: 3466: 3409: 3177: 3009: 2956: 2850: 2797:"Is it possible to turn an elliptical radio galaxy into a BL Lac object?" 2756: 2701: 2523: 2398: 2338: 2028: 1969: 1916: 1777: 1117: 291: 248: 221: 217: 213: 209: 173: 59: 3827: 1859:

Lynden-Bell, Donald (1969). "Galactic Nuclei as Collapsed Old Quasars".

1816:

Lynden-Bell, Donald (1969). "Galactic Nuclei as Collapsed Old Quasars".

1152: – Type of active galaxy that is very luminous at radio wavelengths 82:. The non-stellar radiation from an AGN is theorized to result from the 5573: 2509:

Urry, P.; Padovani, Paolo (1995). "Unified schemes for radioloud AGN".

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Since the late 1960s it has been argued that an AGN must be powered by

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For a long time, active galaxies held all the records for the highest-

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Elitzur, M. (2012). "On the Unification of Active Galactic Nuclei".

1763:

Shields, G. A. (1999). "A Brief History of Active Galactic Nuclei".

1146: – Active galactic nucleus containing a supermassive black hole 5690: 3810: 3746: 3686: 3646: 3483: 3426: 3194: 3026: 2973: 2867: 2773: 2669: 2540: 2460: 2307: 2203: 2178: 2136: 2087: 1986: 1933: 1794: 1522: 1438: 1353: 1328: 1312: 1287: 444: 93:

Active galactic nuclei are the most luminous persistent sources of

27:

Compact region at a galaxy's center with abnormally high luminosity

4268: 4263: 4258: 4215: 3572: 3519: 3342: 3289: 3234: 3124: 3070: 2903: 1288:"The Emission Spectrum of the Extra-Galactic Nebula N. G. C. 1275" 1050: 1030: 730: 443: 311: 142: 71: 607:

There are several subtypes of radio-loud active galactic nuclei.

1644:

Komberg, B. V. (1992). "Quasars and Active Galactic Nuclei". In

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Seyfert, Carl K. (1943). "Nuclear Emission in Spiral Nebulae".

50:. Such excess, non-stellar emissions have been observed in the 4694: 3218:"Evolution of broad-line emission from active galactic nuclei" 422:. A large fraction of the AGN's radiation may be obscured by 341:

Today, AGN are a major topic of astrophysical research, both

180:

by Edward Fath (published in 1909), and the discovery of the

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of selection biases due to anisotropic selection criteria.

321:

was suggested as the source of quasars' power in papers by

302:, published in 1963. Schmidt noted that if this object was 3804:(7673). Springer Science and Business Media LLC: 488–491. 2382:"The X-ray nuclei of intermediate-redshift radio sources" 512:

AGN are a candidate source of high and ultra-high energy

464:

contrasts with the yellow starlight from the host galaxy.

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Hardcastle, M. J.; Evans, D. A.; Croston, J. H. (2006).

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Belsole, E.; Worrall, D. M.; Hardcastle, M. J. (2006).

2511:

Publications of the Astronomical Society of the Pacific

1765:

Publications of the Astronomical Society of the Pacific

1673:"3C 273 : A Star-Like Object with Large Red-Shift" 1333:

Publications of the Astronomical Society of the Pacific

1292:

Publications of the Astronomical Society of the Pacific

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of hot material forms above the accretion disc and can

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of mass onto massive black holes (10 to 10 times the

42:

that emits a significant amount of energy across the

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Pages displaying wikidata descriptions as a fallback

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Among the many interesting characteristics of AGNs:

5511: 5363: 5325: 5304: 5243: 5202: 5151: 5017: 4910: 4820: 4745: 4559: 4474: 4367: 4326: 4236: 4171: 4062: 3917: 1452:Bolton, J. G.; Stanley, G. J.; Slee, O. B. (1949). 2648:Barthel, P. D. (1989). "Is every quasar beamed?". 542:small emitting regions, milli-parsecs in diameter, 468:Some accretion discs produce jets of twin, highly 3222:Monthly Notices of the Royal Astronomical Society 2801:Monthly Notices of the Royal Astronomical Society 2689:Monthly Notices of the Royal Astronomical Society 2386:Monthly Notices of the Royal Astronomical Society 2224:Monthly Notices of the Royal Astronomical Society 2124:Monthly Notices of the Royal Astronomical Society 2015:Monthly Notices of the Royal Astronomical Society 1650:Astrophysics on the Threshold of the 21st Century 290:A major breakthrough was the measurement of the 78:wavebands. A galaxy hosting an AGN is called an 535:very high luminosity, visible out to very high 259:as a tidally distorted galaxy with an unusual 4710: 4536:List of the most distant astronomical objects 3895: 3216:Elitzur, M.; Ho, L. C.; Trump, J. R. (2014). 2375: 2373: 1546:Bulletin of the American Astronomical Society 224:. Active galaxies such as these are known as 8: 3448:Koulouridis, E.; Plionis M.; Chavushyan V.; 2319: 2317: 1329:"The Spectrum of the Spiral Nebula NGC 4151" 580:Low-ionization nuclear emission-line regions 3734:The Astrophysical Journal Supplement Series 3330:Astronomical and Astrophysical Transactions 2476:Annual Review of Astronomy and Astrophysics 2071:"Active galactic nuclei: what's in a name?" 1582:Complete Dictionary of Scientific Biography 5276:Magnetospheric eternally collapsing object 4717: 4703: 4695: 3902: 3888: 3880: 3809: 3763: 3745: 3703: 3685: 3628: 3571: 3518: 3465: 3408: 3341: 3288: 3251: 3233: 3176: 3123: 3069: 3008: 2955: 2902: 2849: 2820: 2755: 2718: 2700: 2522: 2415: 2397: 2337: 2243: 2202: 2153: 2135: 2086: 2045: 2027: 1968: 1915: 1776: 1696: 1623: 1477: 1401: 1352: 1311: 1216: 38:) is a compact region at the center of a 2220:"Optical spectra of 3 CR radio galaxies" 1075:Criticism of the radio-quiet unification 638:Features of different types of galaxies 636: 5674: 3740:(1). American Astronomical Society: 9. 1179: 228:in honor of Seyfert's pioneering work. 2118:Belfiore, Francesco (September 2016). 552:detectable emission across the entire 314:, even more distant at redshift 0.37. 2075:The Astronomy and Astrophysics Review 519:Centrifugal mechanism of acceleration 267:of 16,700 kilometers per second. The 7: 5652: 2218:Hine, R. G.; Longair, M. S. (1979). 5724:Astronomical classification systems 2496:10.1146/annurev.aa.31.090193.002353 2008:Fabian, A. C.; Rees, M. J. (1995). 1577:"Ambartsumian, Viktor Amazaspovich" 1164: – Largest type of black hole 498:Advection Dominated Accretion Flow 456:-long jet ejected from the active 279:(later abbreviated as "quasars"). 90:at the center of its host galaxy. 25: 2183:The Astrophysical Journal Letters 474:very-long-baseline interferometry 5701: 5689: 5677: 5651: 5642: 5641: 4940:Tolman–Oppenheimer–Volkoff limit 4811: 4676: 4665: 4664: 3867: 2720:10.1111/j.1365-2966.2005.09882.x 2417:10.1111/j.1365-2966.2006.10615.x 1403:10.5479/ADS/bib/1939LicOB.19.33M 1234:Publications of Lick Observatory 5057:Innermost stable circular orbit 1209:10.5479/ADS/bib/1909LicOB.5.71F 1170: – Astrophysical technique 1112:Cosmological uses and evolution 282:Soviet Armenian astrophysicist 163:caused by the telescope optics. 5483:Timeline of black hole physics 4607:Galaxy formation and evolution 4602:Galaxy color–magnitude diagram 2179:"When Is BL Lac Not a BL Lac?" 1: 5251:Nonsingular black hole models 3397:Astrophysical Journal Letters 3277:Astrophysical Journal Letters 1606:"Victor Amazasp Ambartsumian" 527:Observational characteristics 116:, and presence or absence of 1376:Mayall, Nicholas U. (1939). 1327:Mayall, Nicholas U. (1934). 5473:Rossi X-ray Timing Explorer 5438:Hypercompact stellar system 5428:Gamma-ray burst progenitors 4489:Galaxies named after people 3307:10.1088/2041-8205/747/2/L33 3142:10.1088/0004-637X/746/2/137 3088:10.1051/0004-6361/201016409 2921:10.1088/0004-637X/730/2/121 1286:Humason, Milton L. (1932). 1261:Lowell Observatory Bulletin 492:Radiatively inefficient AGN 389:of the central black hole. 381:of the galactic bulge (the 277:quasi-stellar radio sources 5750: 5159:Black hole complementarity 5126:Bousso's holographic bound 5111:Quasi-periodic oscillation 4809: 4803:Malament–Hogarth spacetime 4622:Gravitational microlensing 4577:Galactic coordinate system 3590:10.1088/0004-637X/789/1/44 3367:Astronomy and Astrophysics 3058:Astronomy and Astrophysics 2356:10.1051/0004-6361:20021204 1027:Unification of AGN species 486:inverse-Compton scattering 437: 396: 5637: 5030:Gravitational singularity 4732: 4660: 3674:The Astrophysical Journal 3560:The Astrophysical Journal 3165:The Astrophysical Journal 3112:The Astrophysical Journal 2997:The Astrophysical Journal 2944:The Astrophysical Journal 2891:The Astrophysical Journal 2838:The Astrophysical Journal 2795:Browne, I. W. A. (1983). 2744:The Astrophysical Journal 2288:The Astrophysical Journal 2097:10.1007/s00159-017-0102-9 1904:The Astrophysical Journal 1671:Schmidt, Maarten (1963). 1503:The Astrophysical Journal 1419:The Astrophysical Journal 1382:Lick Observatory Bulletin 1189:Lick Observatory Bulletin 672: 669: 666: 660: 657: 654: 651: 645: 642: 351:electromagnetic radiation 95:electromagnetic radiation 5614:PSO J030947.49+271757.31 5539:SDSS J150243.09+111557.3 5072:Blandford–Znajek process 4587:Galactic magnetic fields 4400:Brightest cluster galaxy 4296:Luminous infrared galaxy 3765:10.3847/1538-4365/ac5b64 3705:10.3847/1538-4357/aa5d5a 554:electromagnetic spectrum 247:. Another radio source, 44:electromagnetic spectrum 4870:Active galactic nucleus 4582:Galactic habitable zone 4567:Extragalactic astronomy 4156:Supermassive black hole 4070:Active galactic nucleus 3379:1995A&A...293..683L 3352:2012A&AT...27..557A 3080:2011A&A...532A.102R 2822:10.1093/mnras/204.1.23p 2488:1993ARA&A..31..473A 2348:2002A&A...394..791C 2245:10.1093/mnras/188.1.111 2047:10.1093/mnras/277.1.L55 1162:Supermassive black hole 1044:Radio-quiet unification 413:inverse-Compton scatter 319:supermassive black hole 88:supermassive black hole 32:active galactic nucleus 5498:Tidal disruption event 5468:Supermassive dark star 5386:Black holes in fiction 5371:Outline of black holes 5004:Supermassive dark star 4923:Gravitational collapse 4334:Low surface brightness 4085:Central massive object 3874:Active galactic nuclei 1062:Radio-loud unification 1036: 561:Types of active galaxy 465: 450:Hubble Space Telescope 164: 153:Hubble Space Telescope 5734:Concepts in astronomy 5376:Black Hole Initiative 5189:Holographic principle 4612:Galaxy rotation curve 3617:Astrophysical Journal 3454:Astrophysical Journal 3253:10.1093/mnras/stt2445 2650:Astrophysical Journal 2441:Astrophysical Journal 2155:10.1093/mnras/stw1234 1573:McCutcheon, Robert A. 1168:Reverberation mapping 1034: 508:Particle acceleration 462:synchrotron radiation 447: 146: 5179:Final parsec problem 5138:Schwarzschild radius 4647:Population III stars 4642:Intergalactic travel 4592:Galactic orientation 4459:Voids and supervoids 3876:at Wikimedia Commons 1654:Taylor & Francis 962:stronger than BL Lac 547:luminosity functions 545:strong evolution of 375:Eddington luminosity 265:recessional velocity 251:, was identified by 133:relativistic beaming 99:models of the cosmos 5729:Active galaxy types 5478:Superluminal motion 5453:Population III star 5423:Gravitational waves 5381:Black hole starship 5164:Information paradox 4637:Intergalactic stars 4526:Large quasar groups 4521:Groups and clusters 4385:Groups and clusters 4244:Lyman-alpha emitter 4136:Interstellar medium 3828:10.1038/nature23906 3820:2017Natur.549..488R 3756:2022ApJS..261....9A 3696:2017ApJ...837..110V 3639:2002ApJ...572..169K 3582:2014ApJ...789...44D 3529:2014NatPh..10..417V 3476:2006ApJ...639...37K 3419:1999ApJ...513L.111D 3299:2012ApJ...747L..33E 3244:2014MNRAS.438.3340E 3187:2003ApJ...590...86L 3134:2012ApJ...746..137W 3019:2000ApJ...530L..65N 2966:2006ApJ...648L.101E 2913:2011ApJ...730..121W 2860:2001ApJ...554L..19T 2813:1983MNRAS.204P..23B 2766:2006ApJ...647..161O 2711:2006MNRAS.366..339B 2662:1989ApJ...336..606B 2619:1988Natur.331..147G 2576:1988Natur.331..149L 2533:1995PASP..107..803U 2453:1978ApJ...220..783G 2408:2006MNRAS.370.1893H 2300:1995ApJ...451...88B 2273:1994ASPC...54..201L 2236:1979MNRAS.188..111H 2195:1995ApJ...452L...5V 2146:2016MNRAS.461.3111B 2038:1995MNRAS.277L..55F 1979:1994ApJ...428L..13N 1926:2003ApJ...589L..21M 1873:1969Natur.223..690L 1830:1969Natur.223..690L 1787:1999PASP..111..661S 1734:1963Natur.197.1041G 1689:1963Natur.197.1040S 1593:on 3 December 2019. 1575:(1 November 2019). 1515:1954ApJ...119..206B 1470:1949Natur.164..101B 1431:1943ApJ....97...28S 1394:1939LicOB..19...33M 1345:1934PASP...46..134M 1304:1932PASP...44..267H 1273:1917LowOB...3...59S 1246:1918PLicO..13....9C 1201:1909LicOB...5...71F 639: 448:Image taken by the 387:sphere of influence 379:velocity dispersion 284:Viktor Ambartsumian 263:spectrum, having a 237:elliptical galaxies 231:The development of 172:from the nuclei of 5312:Optical black hole 5225:Reissner–Nordström 5184:Firewall (physics) 5089:Gravitational lens 4632:Intergalactic dust 4617:Gravitational lens 4572:Galactic astronomy 4541:Starburst galaxies 4281:blue compact dwarf 4237:Energetic galaxies 4201:BL Lacertae object 3613:Dultzin-Hacyan, D. 3393:Dultzin-Hacyan, D. 1037: 1035:Unified AGN models 637: 466: 331:Donald Lynden-Bell 165: 161:diffraction spikes 112:of the nucleus by 5665: 5664: 5458:Supermassive star 5448:Naked singularity 5443:Membrane paradigm 5169:Cosmic censorship 5143:Spaghettification 5131:Immirzi parameter 5084:Hawking radiation 5025:Astrophysical jet 4994:Supermassive star 4984:Binary black hole 4918:Stellar evolution 4860:Intermediate-mass 4692: 4691: 4652:Galaxy X (galaxy) 4627:Illustris project 4597:Galactic quadrant 4318:Wolf-Rayet galaxy 4308:Green bean galaxy 4303:Hot dust-obscured 4254:Luminous infrared 4018:Elliptical galaxy 3872:Media related to 3537:10.1038/nphys2951 3450:Dultzin-Hacyan D. 2613:(6152): 147–149. 2570:(6152): 149–151. 2326:Astron. Astrophys 1867:(5207): 690–694. 1742:10.1038/1971041a0 1698:10.1038/1971040a0 1218:2027/uc1.c2914873 1024: 1023: 695:Normal (non-AGN) 434:Relativistic jets 329:in 1964. In 1969 257:Rudolph Minkowski 18:Broad-line region 16:(Redirected from 5741: 5706: 5705: 5704: 5694: 5693: 5682: 5681: 5680: 5673: 5655: 5654: 5645: 5644: 5317:Sonic black hole 5266:Dark-energy star 5121:Bekenstein bound 5106:M–sigma relation 5035:Ring singularity 4815: 4719: 4712: 4705: 4696: 4680: 4668: 4667: 4313:Hanny's Voorwerp 4223:Relativistic jet 4097:Dark matter halo 3904: 3897: 3890: 3881: 3871: 3856: 3855: 3813: 3792: 3786: 3785: 3767: 3749: 3724: 3718: 3717: 3707: 3689: 3665: 3659: 3658: 3632: 3630:astro-ph/0202412 3608: 3602: 3601: 3575: 3555: 3549: 3548: 3522: 3502: 3496: 3495: 3469: 3467:astro-ph/0509843 3445: 3439: 3438: 3412: 3410:astro-ph/9901227 3403:(2): L111–L114. 3389: 3383: 3382: 3362: 3356: 3355: 3345: 3325: 3319: 3318: 3292: 3272: 3266: 3265: 3255: 3237: 3228:(4): 3340–3351. 3213: 3207: 3206: 3180: 3178:astro-ph/0302541 3160: 3154: 3153: 3127: 3106: 3100: 3099: 3073: 3053: 3047: 3046: 3012: 3010:astro-ph/9912524 3003:(2): L101–L104. 2992: 2986: 2985: 2959: 2957:astro-ph/0605686 2950:(2): L101–L104. 2939: 2933: 2932: 2906: 2886: 2880: 2879: 2853: 2851:astro-ph/0105462 2833: 2827: 2826: 2824: 2792: 2786: 2785: 2759: 2757:astro-ph/0601485 2739: 2733: 2732: 2722: 2704: 2702:astro-ph/0511606 2680: 2674: 2673: 2645: 2639: 2638: 2627:10.1038/331147a0 2602: 2596: 2595: 2584:10.1038/331149a0 2559: 2553: 2552: 2526: 2524:astro-ph/9506063 2506: 2500: 2499: 2471: 2465: 2464: 2436: 2430: 2429: 2419: 2401: 2399:astro-ph/0603090 2392:(4): 1893–1904. 2377: 2368: 2367: 2341: 2339:astro-ph/0207654 2321: 2312: 2311: 2283: 2277: 2276: 2256: 2250: 2249: 2247: 2215: 2209: 2208: 2206: 2174: 2168: 2167: 2157: 2139: 2115: 2109: 2108: 2090: 2066: 2060: 2059: 2049: 2031: 2029:astro-ph/9509096 2005: 1999: 1998: 1972: 1970:astro-ph/9403052 1952: 1946: 1945: 1919: 1917:astro-ph/0304274 1899: 1893: 1892: 1881:10.1038/223690a0 1856: 1850: 1849: 1838:10.1038/223690a0 1813: 1807: 1806: 1780: 1778:astro-ph/9903401 1760: 1754: 1753: 1717: 1711: 1710: 1700: 1668: 1662: 1661: 1646:Kardashev, N. S. 1641: 1635: 1629: 1627: 1625:10.1063/1.881754 1601: 1595: 1594: 1589:. Archived from 1587:Encyclopedia.com 1569: 1563: 1562: 1557:. Archived from 1537:Israelian, Garik 1533: 1527: 1526: 1498: 1492: 1491: 1481: 1479:10.1038/164101b0 1449: 1443: 1442: 1414: 1408: 1407: 1405: 1373: 1367: 1366: 1356: 1324: 1318: 1317: 1315: 1283: 1277: 1276: 1256: 1250: 1249: 1229: 1223: 1222: 1220: 1184: 1156:Relativistic jet 1140: 1135:M–sigma relation 640: 586:Seyfert galaxies 440:Relativistic jet 424:interstellar gas 383:M–sigma relation 355:galaxy evolution 226:Seyfert galaxies 157:relativistic jet 151:observed by the 108:, the degree of 21: 5749: 5748: 5744: 5743: 5742: 5740: 5739: 5738: 5714: 5713: 5712: 5702: 5700: 5688: 5678: 5676: 5668: 5666: 5661: 5633: 5609:ULAS J1342+0928 5569:SDSS J0849+1114 5554:Phoenix Cluster 5507: 5359: 5321: 5300: 5239: 5198: 5194:No-hair theorem 5147: 5101:Bondi accretion 5067:Penrose process 5013: 4979:Gamma-ray burst 4906: 4816: 4807: 4793:Direct collapse 4741: 4728: 4723: 4693: 4688: 4656: 4555: 4470: 4363: 4322: 4232: 4167: 4146:Galaxy filament 4090:Galactic Center 4058: 3913: 3908: 3864: 3859: 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1257: 1253: 1231: 1230: 1226: 1186: 1185: 1181: 1177: 1138: 1131: 1114: 1077: 1064: 1046: 1029: 652:Emission lines 605: 576: 574:Radio-quiet AGN 563: 529: 510: 502:Eddington limit 494: 442: 436: 401: 395: 363: 336:X-ray astronomy 327:Yakov Zeldovich 300:Maarten Schmidt 269:3C radio survey 233:radio astronomy 202:Nicholas Mayall 141: 86:of matter by a 28: 23: 22: 15: 12: 11: 5: 5747: 5745: 5737: 5736: 5731: 5726: 5716: 5715: 5711: 5710: 5698: 5686: 5663: 5662: 5660: 5659: 5649: 5638: 5635: 5634: 5632: 5631: 5629:Swift J1644+57 5626: 5621: 5616: 5611: 5606: 5601: 5596: 5591: 5586: 5581: 5579:MS 0735.6+7421 5576: 5571: 5566: 5561: 5556: 5551: 5546: 5544:Sagittarius A* 5541: 5536: 5531: 5526: 5521: 5515: 5513: 5509: 5508: 5506: 5505: 5500: 5495: 5490: 5485: 5480: 5475: 5470: 5465: 5460: 5455: 5450: 5445: 5440: 5435: 5430: 5425: 5420: 5419: 5418: 5413: 5403: 5398: 5393: 5388: 5383: 5378: 5373: 5367: 5365: 5361: 5360: 5358: 5357: 5352: 5347: 5342: 5337: 5331: 5329: 5323: 5322: 5320: 5319: 5314: 5308: 5306: 5302: 5301: 5299: 5298: 5293: 5288: 5283: 5278: 5273: 5268: 5263: 5258: 5253: 5247: 5245: 5241: 5240: 5238: 5237: 5232: 5227: 5222: 5217: 5206: 5204: 5200: 5199: 5197: 5196: 5191: 5186: 5181: 5176: 5171: 5166: 5161: 5155: 5153: 5149: 5148: 5146: 5145: 5140: 5135: 5134: 5133: 5123: 5118: 5116:Thermodynamics 5113: 5108: 5103: 5098: 5097: 5096: 5086: 5081: 5079:Accretion disk 5076: 5075: 5074: 5069: 5059: 5054: 5049: 5044: 5043: 5042: 5037: 5027: 5021: 5019: 5015: 5014: 5012: 5011: 5006: 5001: 4996: 4991: 4986: 4981: 4976: 4975: 4974: 4969: 4964: 4954: 4953: 4952: 4942: 4937: 4936: 4935: 4925: 4920: 4914: 4912: 4908: 4907: 4905: 4904: 4903: 4902: 4897: 4892: 4887: 4882: 4877: 4872: 4862: 4857: 4856: 4855: 4845: 4844: 4843: 4840: 4835: 4824: 4822: 4818: 4817: 4810: 4808: 4806: 4805: 4800: 4795: 4790: 4785: 4780: 4775: 4770: 4765: 4760: 4755: 4753:BTZ black hole 4749: 4747: 4743: 4742: 4740: 4739: 4733: 4730: 4729: 4724: 4722: 4721: 4714: 4707: 4699: 4690: 4689: 4687: 4686: 4674: 4661: 4658: 4657: 4655: 4654: 4649: 4644: 4639: 4634: 4629: 4624: 4619: 4614: 4609: 4604: 4599: 4594: 4589: 4584: 4579: 4574: 4569: 4563: 4561: 4557: 4556: 4554: 4553: 4548: 4543: 4538: 4533: 4528: 4523: 4518: 4517: 4516: 4511: 4506: 4501: 4496: 4491: 4480: 4478: 4472: 4471: 4469: 4468: 4467: 4466: 4456: 4451: 4446: 4444:Stellar stream 4441: 4436: 4431: 4430: 4429: 4424: 4419: 4409: 4408: 4407: 4402: 4397: 4392: 4382: 4377: 4371: 4369: 4365: 4364: 4362: 4361: 4356: 4351: 4346: 4341: 4336: 4330: 4328: 4324: 4323: 4321: 4320: 4315: 4310: 4305: 4300: 4299: 4298: 4293: 4288: 4283: 4273: 4272: 4271: 4266: 4261: 4251: 4246: 4240: 4238: 4234: 4233: 4231: 4230: 4225: 4220: 4219: 4218: 4213: 4203: 4198: 4193: 4188: 4183: 4177: 4175: 4169: 4168: 4166: 4165: 4164: 4163: 4153: 4148: 4143: 4138: 4133: 4131:Galactic ridge 4128: 4126:Galactic plane 4123: 4122: 4121: 4111: 4110: 4109: 4099: 4094: 4093: 4092: 4082: 4077: 4072: 4066: 4064: 4060: 4059: 4057: 4056: 4055: 4054: 4044: 4039: 4038: 4037: 4027: 4026: 4025: 4015: 4014: 4013: 4008: 4003: 3998: 3988: 3987: 3986: 3981: 3976: 3971: 3966: 3961: 3956: 3946: 3945: 3944: 3939: 3929: 3923: 3921: 3915: 3914: 3909: 3907: 3906: 3899: 3892: 3884: 3878: 3877: 3863: 3862:External links 3860: 3858: 3857: 3787: 3719: 3660: 3647:10.1086/340299 3623:(1): 169–177. 3611:Krongold, Y.; 3603: 3550: 3513:(6): 417–420. 3507:Nature Physics 3497: 3484:10.1086/498421 3440: 3427:10.1086/311925 3384: 3357: 3320: 3283:(2): L33–L35. 3267: 3208: 3195:10.1086/375008 3155: 3118:(2): 137–165. 3101: 3048: 3027:10.1086/312491 2987: 2974:10.1086/508158 2934: 2897:(2): 121–130. 2881: 2868:10.1086/320926 2844:(1): L19–L23. 2828: 2787: 2774:10.1086/505337 2750:(1): 161–171. 2734: 2695:(1): 339–352. 2675: 2670:10.1086/167038 2640: 2597: 2554: 2541:10.1086/133630 2501: 2482:(1): 473–521. 2466: 2461:10.1086/155966 2431: 2369: 2332:(3): 791–800. 2313: 2308:10.1086/176202 2278: 2251: 2210: 2204:10.1086/309716 2169: 2110: 2061: 2022:(2): L55–L58. 2000: 1987:10.1086/187381 1947: 1934:10.1086/375804 1910:(1): L21–L24. 1894: 1851: 1808: 1795:10.1086/316378 1755: 1728:(4872): 1041. 1712: 1683:(4872): 1040. 1663: 1636: 1596: 1564: 1561:on 2015-09-11. 1528: 1523:10.1086/145812 1493: 1444: 1439:10.1086/144488 1409: 1368: 1354:10.1086/124429 1319: 1313:10.1086/124242 1278: 1251: 1224: 1178: 1176: 1173: 1172: 1171: 1165: 1159: 1153: 1147: 1141: 1130: 1127: 1113: 1110: 1076: 1073: 1063: 1060: 1045: 1042: 1028: 1025: 1022: 1021: 1018: 1015: 1012: 1009: 1006: 1003: 1000: 997: 994: 991: 985: 984: 981: 978: 975: 972: 969: 966: 963: 960: 957: 954: 948: 947: 944: 941: 938: 935: 932: 929: 926: 923: 920: 917: 911: 910: 907: 904: 901: 898: 895: 892: 889: 886: 883: 880: 874: 873: 870: 867: 864: 861: 858: 855: 852: 849: 846: 843: 837: 836: 833: 830: 827: 824: 821: 818: 815: 812: 809: 806: 802: 801: 798: 795: 792: 789: 786: 783: 780: 777: 774: 771: 764: 763: 760: 757: 754: 751: 748: 745: 742: 739: 736: 733: 727: 726: 723: 720: 717: 714: 711: 708: 705: 702: 699: 696: 692: 691: 688: 685: 682: 678: 677: 671: 668: 665: 659: 656: 653: 650: 644: 635: 634: 631:Radio galaxies 628: 621:BL Lac objects 613: 604: 603:Radio-loud AGN 601: 600: 599: 596: 589: 583: 575: 572: 562: 559: 558: 557: 550: 543: 540: 528: 525: 509: 506: 493: 490: 438:Main article: 435: 432: 420:emission lines 405:accretion disc 399:Accretion disc 397:Main article: 394: 393:Accretion disc 391: 362: 359: 323:Edwin Salpeter 294:of the quasar 198:Milton Humason 170:emission lines 140: 137: 106:accretion disk 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 5746: 5735: 5732: 5730: 5727: 5725: 5722: 5721: 5719: 5709: 5699: 5697: 5692: 5687: 5685: 5675: 5671: 5658: 5650: 5648: 5640: 5639: 5636: 5630: 5627: 5625: 5622: 5620: 5617: 5615: 5612: 5610: 5607: 5605: 5604:Markarian 501 5602: 5600: 5597: 5595: 5592: 5590: 5587: 5585: 5582: 5580: 5577: 5575: 5572: 5570: 5567: 5565: 5562: 5560: 5557: 5555: 5552: 5550: 5547: 5545: 5542: 5540: 5537: 5535: 5532: 5530: 5529:XTE J1118+480 5527: 5525: 5524:XTE J1650-500 5522: 5520: 5517: 5516: 5514: 5510: 5504: 5501: 5499: 5496: 5494: 5491: 5489: 5486: 5484: 5481: 5479: 5476: 5474: 5471: 5469: 5466: 5464: 5461: 5459: 5456: 5454: 5451: 5449: 5446: 5444: 5441: 5439: 5436: 5434: 5431: 5429: 5426: 5424: 5421: 5417: 5414: 5412: 5409: 5408: 5407: 5404: 5402: 5399: 5397: 5394: 5392: 5389: 5387: 5384: 5382: 5379: 5377: 5374: 5372: 5369: 5368: 5366: 5362: 5356: 5353: 5351: 5348: 5346: 5343: 5341: 5338: 5336: 5333: 5332: 5330: 5328: 5324: 5318: 5315: 5313: 5310: 5309: 5307: 5303: 5297: 5294: 5292: 5289: 5287: 5284: 5282: 5279: 5277: 5274: 5272: 5269: 5267: 5264: 5262: 5259: 5257: 5254: 5252: 5249: 5248: 5246: 5242: 5236: 5233: 5231: 5228: 5226: 5223: 5221: 5218: 5215: 5211: 5210:Schwarzschild 5208: 5207: 5205: 5201: 5195: 5192: 5190: 5187: 5185: 5182: 5180: 5177: 5175: 5172: 5170: 5167: 5165: 5162: 5160: 5157: 5156: 5154: 5150: 5144: 5141: 5139: 5136: 5132: 5129: 5128: 5127: 5124: 5122: 5119: 5117: 5114: 5112: 5109: 5107: 5104: 5102: 5099: 5095: 5092: 5091: 5090: 5087: 5085: 5082: 5080: 5077: 5073: 5070: 5068: 5065: 5064: 5063: 5060: 5058: 5055: 5053: 5052:Photon sphere 5050: 5048: 5047:Event horizon 5045: 5041: 5038: 5036: 5033: 5032: 5031: 5028: 5026: 5023: 5022: 5020: 5016: 5010: 5007: 5005: 5002: 5000: 4997: 4995: 4992: 4990: 4987: 4985: 4982: 4980: 4977: 4973: 4972:Related links 4970: 4968: 4965: 4963: 4960: 4959: 4958: 4955: 4951: 4950:Related links 4948: 4947: 4946: 4943: 4941: 4938: 4934: 4933:Related links 4931: 4930: 4929: 4926: 4924: 4921: 4919: 4916: 4915: 4913: 4909: 4901: 4898: 4896: 4893: 4891: 4888: 4886: 4883: 4881: 4878: 4876: 4873: 4871: 4868: 4867: 4866: 4863: 4861: 4858: 4854: 4851: 4850: 4849: 4846: 4841: 4839: 4836: 4834: 4831: 4830: 4829: 4826: 4825: 4823: 4819: 4814: 4804: 4801: 4799: 4796: 4794: 4791: 4789: 4786: 4784: 4781: 4779: 4776: 4774: 4771: 4769: 4766: 4764: 4761: 4759: 4758:Schwarzschild 4756: 4754: 4751: 4750: 4748: 4744: 4738: 4735: 4734: 4731: 4727: 4720: 4715: 4713: 4708: 4706: 4701: 4700: 4697: 4685: 4684: 4679: 4675: 4673: 4672: 4663: 4662: 4659: 4653: 4650: 4648: 4645: 4643: 4640: 4638: 4635: 4633: 4630: 4628: 4625: 4623: 4620: 4618: 4615: 4613: 4610: 4608: 4605: 4603: 4600: 4598: 4595: 4593: 4590: 4588: 4585: 4583: 4580: 4578: 4575: 4573: 4570: 4568: 4565: 4564: 4562: 4558: 4552: 4549: 4547: 4546:Superclusters 4544: 4542: 4539: 4537: 4534: 4532: 4529: 4527: 4524: 4522: 4519: 4515: 4512: 4510: 4507: 4505: 4502: 4500: 4497: 4495: 4492: 4490: 4487: 4486: 4485: 4482: 4481: 4479: 4477: 4473: 4465: 4462: 4461: 4460: 4457: 4455: 4452: 4450: 4449:Superclusters 4447: 4445: 4442: 4440: 4437: 4435: 4432: 4428: 4425: 4423: 4420: 4418: 4415: 4414: 4413: 4410: 4406: 4403: 4401: 4398: 4396: 4393: 4391: 4388: 4387: 4386: 4383: 4381: 4380:Galactic tide 4378: 4376: 4373: 4372: 4370: 4366: 4360: 4357: 4355: 4352: 4350: 4347: 4345: 4342: 4340: 4339:Ultra diffuse 4337: 4335: 4332: 4331: 4329: 4325: 4319: 4316: 4314: 4311: 4309: 4306: 4304: 4301: 4297: 4294: 4292: 4289: 4287: 4284: 4282: 4279: 4278: 4277: 4274: 4270: 4267: 4265: 4262: 4260: 4257: 4256: 4255: 4252: 4250: 4247: 4245: 4242: 4241: 4239: 4235: 4229: 4226: 4224: 4221: 4217: 4214: 4212: 4209: 4208: 4207: 4204: 4202: 4199: 4197: 4194: 4192: 4189: 4187: 4184: 4182: 4179: 4178: 4176: 4174: 4173:Active nuclei 4170: 4162: 4159: 4158: 4157: 4154: 4152: 4149: 4147: 4144: 4142: 4139: 4137: 4134: 4132: 4129: 4127: 4124: 4120: 4117: 4116: 4115: 4112: 4108: 4105: 4104: 4103: 4100: 4098: 4095: 4091: 4088: 4087: 4086: 4083: 4081: 4078: 4076: 4073: 4071: 4068: 4067: 4065: 4061: 4053: 4050: 4049: 4048: 4045: 4043: 4040: 4036: 4033: 4032: 4031: 4028: 4024: 4021: 4020: 4019: 4016: 4012: 4009: 4007: 4004: 4002: 3999: 3997: 3994: 3993: 3992: 3989: 3985: 3982: 3980: 3977: 3975: 3972: 3970: 3967: 3965: 3962: 3960: 3957: 3955: 3952: 3951: 3950: 3947: 3943: 3940: 3938: 3935: 3934: 3933: 3930: 3928: 3925: 3924: 3922: 3920: 3916: 3912: 3905: 3900: 3898: 3893: 3891: 3886: 3885: 3882: 3875: 3870: 3866: 3865: 3861: 3853: 3849: 3845: 3841: 3837: 3833: 3829: 3825: 3821: 3817: 3812: 3807: 3803: 3799: 3791: 3788: 3783: 3779: 3775: 3771: 3766: 3761: 3757: 3753: 3748: 3743: 3739: 3735: 3731: 3723: 3720: 3715: 3711: 3706: 3701: 3697: 3693: 3688: 3683: 3679: 3675: 3671: 3664: 3661: 3656: 3652: 3648: 3644: 3640: 3636: 3631: 3626: 3622: 3618: 3614: 3607: 3604: 3599: 3595: 3591: 3587: 3583: 3579: 3574: 3569: 3565: 3561: 3554: 3551: 3546: 3542: 3538: 3534: 3530: 3526: 3521: 3516: 3512: 3508: 3501: 3498: 3493: 3489: 3485: 3481: 3477: 3473: 3468: 3463: 3459: 3455: 3451: 3444: 3441: 3436: 3432: 3428: 3424: 3420: 3416: 3411: 3406: 3402: 3398: 3394: 3388: 3385: 3380: 3376: 3372: 3368: 3361: 3358: 3353: 3349: 3344: 3339: 3335: 3331: 3324: 3321: 3316: 3312: 3308: 3304: 3300: 3296: 3291: 3286: 3282: 3278: 3271: 3268: 3263: 3259: 3254: 3249: 3245: 3241: 3236: 3231: 3227: 3223: 3219: 3212: 3209: 3204: 3200: 3196: 3192: 3188: 3184: 3179: 3174: 3170: 3166: 3159: 3156: 3151: 3147: 3143: 3139: 3135: 3131: 3126: 3121: 3117: 3113: 3105: 3102: 3097: 3093: 3089: 3085: 3081: 3077: 3072: 3067: 3063: 3059: 3052: 3049: 3044: 3040: 3036: 3032: 3028: 3024: 3020: 3016: 3011: 3006: 3002: 2998: 2991: 2988: 2983: 2979: 2975: 2971: 2967: 2963: 2958: 2953: 2949: 2945: 2938: 2935: 2930: 2926: 2922: 2918: 2914: 2910: 2905: 2900: 2896: 2892: 2885: 2882: 2877: 2873: 2869: 2865: 2861: 2857: 2852: 2847: 2843: 2839: 2832: 2829: 2823: 2818: 2814: 2810: 2806: 2802: 2798: 2791: 2788: 2783: 2779: 2775: 2771: 2767: 2763: 2758: 2753: 2749: 2745: 2738: 2735: 2730: 2726: 2721: 2716: 2712: 2708: 2703: 2698: 2694: 2690: 2686: 2679: 2676: 2671: 2667: 2663: 2659: 2655: 2651: 2644: 2641: 2636: 2632: 2628: 2624: 2620: 2616: 2612: 2608: 2601: 2598: 2593: 2589: 2585: 2581: 2577: 2573: 2569: 2565: 2558: 2555: 2550: 2546: 2542: 2538: 2534: 2530: 2525: 2520: 2516: 2512: 2505: 2502: 2497: 2493: 2489: 2485: 2481: 2477: 2470: 2467: 2462: 2458: 2454: 2450: 2446: 2442: 2435: 2432: 2427: 2423: 2418: 2413: 2409: 2405: 2400: 2395: 2391: 2387: 2383: 2376: 2374: 2370: 2365: 2361: 2357: 2353: 2349: 2345: 2340: 2335: 2331: 2327: 2320: 2318: 2314: 2309: 2305: 2301: 2297: 2293: 2289: 2282: 2279: 2274: 2270: 2266: 2262: 2255: 2252: 2246: 2241: 2237: 2233: 2229: 2225: 2221: 2214: 2211: 2205: 2200: 2196: 2192: 2188: 2184: 2180: 2173: 2170: 2165: 2161: 2156: 2151: 2147: 2143: 2138: 2133: 2129: 2125: 2121: 2114: 2111: 2106: 2102: 2098: 2094: 2089: 2084: 2080: 2076: 2072: 2065: 2062: 2057: 2053: 2048: 2043: 2039: 2035: 2030: 2025: 2021: 2017: 2016: 2011: 2004: 2001: 1996: 1992: 1988: 1984: 1980: 1976: 1971: 1966: 1962: 1958: 1951: 1948: 1943: 1939: 1935: 1931: 1927: 1923: 1918: 1913: 1909: 1905: 1898: 1895: 1890: 1886: 1882: 1878: 1874: 1870: 1866: 1862: 1855: 1852: 1847: 1843: 1839: 1835: 1831: 1827: 1824:(5207): 690. 1823: 1819: 1812: 1809: 1804: 1800: 1796: 1792: 1788: 1784: 1779: 1774: 1770: 1766: 1759: 1756: 1751: 1747: 1743: 1739: 1735: 1731: 1727: 1723: 1716: 1713: 1708: 1704: 1699: 1694: 1690: 1686: 1682: 1678: 1674: 1667: 1664: 1659: 1655: 1651: 1647: 1640: 1637: 1633: 1626: 1621: 1617: 1613: 1612: 1611:Physics Today 1607: 1600: 1597: 1592: 1588: 1584: 1583: 1578: 1574: 1568: 1565: 1560: 1556: 1552: 1548: 1547: 1542: 1538: 1532: 1529: 1524: 1520: 1516: 1512: 1508: 1504: 1497: 1494: 1489: 1485: 1480: 1475: 1471: 1467: 1464:(4159): 101. 1463: 1459: 1455: 1448: 1445: 1440: 1436: 1432: 1428: 1424: 1420: 1413: 1410: 1404: 1399: 1395: 1391: 1387: 1383: 1379: 1372: 1369: 1364: 1360: 1355: 1350: 1346: 1342: 1338: 1334: 1330: 1323: 1320: 1314: 1309: 1305: 1301: 1297: 1293: 1289: 1282: 1279: 1274: 1270: 1266: 1262: 1255: 1252: 1247: 1243: 1239: 1235: 1228: 1225: 1219: 1214: 1210: 1206: 1202: 1198: 1194: 1190: 1183: 1180: 1174: 1169: 1166: 1163: 1160: 1157: 1154: 1151: 1148: 1145: 1142: 1136: 1133: 1132: 1128: 1126: 1122: 1119: 1111: 1109: 1105: 1101: 1097: 1093: 1089: 1085: 1081: 1074: 1072: 1068: 1061: 1059: 1055: 1052: 1043: 1041: 1033: 1026: 1019: 1016: 1013: 1010: 1007: 1004: 1001: 998: 995: 992: 990: 987: 986: 982: 979: 976: 973: 970: 967: 964: 961: 958: 955: 953: 950: 949: 945: 942: 939: 936: 933: 930: 927: 924: 921: 918: 916: 913: 912: 908: 905: 902: 899: 896: 893: 890: 887: 884: 881: 879: 876: 875: 871: 868: 865: 862: 859: 856: 853: 850: 847: 844: 842: 839: 838: 834: 831: 828: 825: 822: 819: 816: 813: 810: 807: 804: 803: 799: 796: 793: 790: 787: 784: 781: 778: 775: 772: 769: 766: 765: 761: 758: 755: 752: 749: 746: 743: 740: 737: 734: 732: 729: 728: 724: 721: 718: 715: 712: 709: 706: 703: 700: 697: 694: 693: 689: 686: 683: 680: 679: 676: 664: 649: 641: 632: 629: 626: 622: 618: 614: 610: 609: 608: 602: 597: 594: 590: 587: 584: 581: 578: 577: 573: 571: 567: 560: 555: 551: 548: 544: 541: 538: 534: 533: 532: 526: 524: 522: 520: 515: 507: 505: 503: 499: 491: 489: 487: 483: 479: 475: 471: 463: 459: 455: 451: 446: 441: 433: 431: 429: 425: 421: 417: 414: 410: 406: 400: 392: 390: 388: 384: 380: 376: 372: 368: 360: 358: 356: 352: 348: 344: 343:observational 339: 337: 332: 328: 324: 320: 315: 313: 309: 306:(outside the 305: 304:extragalactic 301: 297: 293: 288: 285: 280: 278: 274: 273:visible-light 270: 266: 262: 261:emission-line 258: 254: 250: 246: 242: 238: 234: 229: 227: 223: 219: 215: 211: 207: 203: 199: 195: 194:Vesto Slipher 191: 187: 183: 179: 175: 171: 162: 158: 154: 150: 145: 138: 136: 134: 130: 126: 121: 119: 115: 111: 107: 102: 100: 96: 91: 89: 85: 81: 80:active galaxy 77: 73: 69: 65: 61: 57: 53: 49: 45: 41: 37: 33: 19: 5559:PKS 1302-102 5433:Gravity well 5401:Compact star 5355:Microquasars 5340:Most massive 5244:Alternatives 5009:X-ray binary 4928:Neutron star 4869: 4865:Supermassive 4842:Hawking star 4783:Supermassive 4682: 4670: 4405:fossil group 4327:Low activity 4172: 4161:Ultramassive 4069: 3991:Dwarf galaxy 3974:intermediate 3969:grand design 3801: 3797: 3790: 3737: 3733: 3722: 3677: 3673: 3663: 3620: 3616: 3606: 3563: 3559: 3553: 3510: 3506: 3500: 3460:(1): 37–45. 3457: 3453: 3443: 3400: 3396: 3387: 3370: 3366: 3360: 3333: 3329: 3323: 3280: 3276: 3270: 3225: 3221: 3211: 3171:(1): 86–94. 3168: 3164: 3158: 3115: 3111: 3104: 3061: 3057: 3051: 3000: 2996: 2990: 2947: 2943: 2937: 2894: 2890: 2884: 2841: 2837: 2831: 2804: 2800: 2790: 2747: 2743: 2737: 2692: 2688: 2678: 2653: 2649: 2643: 2610: 2606: 2600: 2567: 2563: 2557: 2514: 2510: 2504: 2479: 2475: 2469: 2444: 2440: 2434: 2389: 2385: 2329: 2325: 2291: 2287: 2281: 2264: 2260: 2254: 2227: 2223: 2213: 2186: 2182: 2172: 2127: 2123: 2113: 2078: 2074: 2064: 2019: 2013: 2003: 1960: 1957:Astrophys. J 1956: 1950: 1907: 1903: 1897: 1864: 1860: 1854: 1821: 1817: 1811: 1771:(760): 661. 1768: 1764: 1758: 1725: 1721: 1715: 1680: 1676: 1666: 1649: 1639: 1615: 1609: 1599: 1591:the original 1580: 1567: 1559:the original 1550: 1544: 1531: 1506: 1502: 1496: 1461: 1457: 1447: 1422: 1418: 1412: 1385: 1381: 1371: 1339:(271): 134. 1336: 1332: 1322: 1298:(260): 267. 1295: 1291: 1281: 1264: 1260: 1254: 1237: 1233: 1227: 1192: 1188: 1182: 1150:Radio galaxy 1123: 1115: 1106: 1102: 1098: 1094: 1090: 1086: 1082: 1078: 1069: 1065: 1056: 1047: 1038: 989:Radio galaxy 674: 662: 647: 643:Galaxy type 606: 591:Radio-quiet 568: 564: 530: 516: 511: 495: 467: 402: 364: 340: 316: 289: 281: 253:Walter Baade 230: 206:Carl Seyfert 190:Heber Curtis 166: 122: 103: 92: 79: 68:ultra-violet 35: 31: 29: 5708:Outer space 5549:Centaurus A 5503:Planet Nine 5406:Exotic star 5335:Black holes 5281:Planck star 5230:Kerr–Newman 4945:White dwarf 4895:Radio-Quiet 4853:Microquasar 4726:Black holes 4464:void galaxy 4427:cannibalism 4412:Interacting 4368:Interaction 4354:Blue Nugget 4344:Dark galaxy 4249:Lyman-break 4141:Protogalaxy 4107:Disc galaxy 3064:: A102–21. 2656:: 606–611. 2517:: 803–845. 2230:: 111–130. 2130:(3): 3111. 805:Seyfert II 625:OVV quasars 514:cosmic rays 482:synchrotron 460:. 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