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1.
Data on the dependences of the masses and bolometric luminosities of Active Galactic Nuclei on their cosmological redshifts are used to determine the redshift dependences of their X-ray luminosities and the kinetic powers of their relativistic jets. These results are used, in turn, to obtain the redshift dependence of the spins of the central supermassive black holes. 相似文献
2.
V. L. Afanas’ev N. V. Borisov Yu. N. Gnedin S. D. Buliga T. M. Natsvlishvili M. Yu. Piotrovich 《Astronomy Reports》2014,58(10):725-732
Spectropolarimetric observations of a number of Active Galactic Nuclei obtained using the SCORPIO-2 aperture focal reducer installed on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences are used to estimate physical parameters of these objects. The measured polarization and its wavelength dependence are consistent with the expectations of a standard accretion-disk model taking into account the effect of Faraday depolarization over the mean free path of the emitted photons. Estimates of the magnetic field in the accretion disk near the innermost stable orbit and the spin of the accreting central black hole are obtained. It is concluded that supermassive black holes with standard accretion disks and equal magnetic and radiative pressures are primarily Kerr black holes. 相似文献
3.
Mikhailov A. G. Piotrovich M. Yu. Buliga S. D. Natsvlishvili T. M. Gnedin Yu. N. 《Astronomy Reports》2019,63(6):433-444
Astronomy Reports - Hybrid models for the generation of relativistic jets are used to place constraints on the spins of supermassive black holes (SMBHs) in active galactic nuclei at redshifts z... 相似文献
4.
A. A. Kisselev Yu. N. Gnedin E. A. Grosheva N. A. Shakht D. L. Gorshanov M. Yu. Piotrovich 《Astronomy Reports》2007,51(2):100-108
We have used two astrometric methods developed at the Main Astronomical Observatory of the Russian Academy of Sciences—the method of apparent-motion parameters (AMP) and a direct geometrical method (DGM)—to derive the orbit of the star S2 around the Galactic center, and thereby the mass of the supermassive black hole at the Galactic center. The AMP method, which is based on measurements of the curvature of a fairly short orbital arc, is efficient if observational data on the relative radial velocity are available. The mass of the supermassive black hole was also estimated using astrophysical methods, based on the empirical relation between the masses of the supermassive black holes at the centers of galaxies and quasars and the radio and X-ray luminosities of these regions. We estimate the magnetic-field strength near the event horizon of the supermassive black hole at the Galactic center using a synchrotron self-absorption model. 相似文献
5.
The observed variety of types of Active Galactic Nuclei (AGN) in galaxies with various masses and morphologies is considered. It is proposed that this diversity is related to the evolutionary development of their host galaxies and central regions, including their bulges, massive black holes, and accretion disks. A possible evolutionary scenario explaining the relationship between various types of AGN is proposed, in which, in addition to differences in the accretion states of the circumnuclear disks, the type of host galaxy is also taken into consideration. Special attention is given to the qualitative similarity of the accretion and radiative processes occurring in active objects with stellar-mass black holes (microquasars) and in AGN, in spite of the huge differences in the masses of their black holes. Studies of variability of the emission of microquasars taking this similarity into account can be used to make predictions about the behavior of the emission of AGN (with scaling in accordance with the black-hole mass). 相似文献
6.
A. E. Vol’vach L. N. Vol’vach M. G. Larionov M. F. Aller H. D. Aller M. Villata K. M. Raiteri 《Astronomy Reports》2008,52(11):867-874
Radio and optical data are used to analyze the development of the flare in the blazar 3C 454.3 observed in 2004–2007. A detailed correspondance between the optical and radio flares is established, with a time delay that depends on the observing frequency. The variation of the delay of the radio flare relative to the optical flare is opposite to the dispersion delay expected for the propagation of radiation in the interstellar medium, testifying to an intrinsic origin for the observed outburst. Small-scale flux variations on time intervals of 5–10 days in the millimeter and optical are also correlated, with a time delay of about ten months. This may provide evidence for a single source generating the radiation at all wavelengths. Rapid flux fluctuations in the radio and optical that are correlated with the indicated time delays could be associated with inhomogeneities in the accretion disk. Detailed studies of the flux variations of Active Galactic Nuclei (AGN) can be used to analyze the structure of the accretion disk. A model for the energy release in AGN that is not associated purely with accretion onto supermassive black holes is proposed. As is the case for other active members of the AGN family, estimates of the lifetime of the binary black-hole system in 3C 454.3 suggest that this object is in a stage of its evolution that is fairly close to the coalescence of its black holes. The energy that is released as the companion of the central black hole loses orbital angular momentum is sufficient to explain the observed AGN phenomena. The source of primary energy release could be heating of the gas behind shock fronts that arise due to the friction between the companion black hole and the ambient gaseous medium. The orbit of the companion could be located at the periphery of the accretion disk of the central body at its apocenter and plunge more deeply into the accretion disk at its pericenter, inducing flares at all wavelengths. Energy-release parameters such as the temperature and density of the heated gas are estimated for 3C 454.3. The model considered assumes omnidirectional radiation of the medium in the presence of a magnetic field. The radiation corresponding to the minimum flux level (base level) could represent omnidirectional radiation due to the orbit of the moving companion. The fraction of the energy that is transferred to directed jets is small, comprising 1–2% of the total energy released due to the loss of orbital angular momentum by the companion. 相似文献
7.
This is the first paper in a project aimed at analyzing relations between the masses of supermassive black holes or nuclear
clusters in galaxies and the kinematic features of the host galaxies. We present long-slit spectroscopic observations of galaxies
obtained on the 6-m telescope of the Special Astrophysical Observatory using the SCORPIO focal reducer. Radial profiles of
the line-of-sight velocities and velocity dispersions of the stellar populations were obtained for seven galaxies with known
masses of their supermassive black holes (Mkn 79, Mkn 279, NGC 2787, NGC 3245, NGC 3516, NGC 7457, and NGC 7469), and also
for one galaxy with a nuclear cluster (NGC 428). Velocity profiles of the emitting gas were obtained for some of these galaxies
as well. We present preliminary galactic rotation curves derived from these data. 相似文献
8.
A. E. Vol’vach L. N. Vol’vach A. M. Kut’kin M. G. Larionov M. F. Aller H. D. Aller 《Astronomy Reports》2010,54(1):28-37
Long-term, multi-frequency monitoring of the radio fluxes of the four BL Lac objects 3C 120, OJ 287, 1308+326, and BL Lac
is considered. Harmonic components of the flux variability on scales from one year to decades are determined. The observational
data used were obtained at the Radio Astronomy Laboratory of the Crimean Astrophysical Observatory (Ukraine) and the University
of Michigan Radio Astronomy Observatory (USA). These data are used to construct kinematic models for active galactic nuclei
using values for the orbital and precessional periods of binary systems consisting of supermassive black holes. The derived
speeds of the companions in their orbits lie in the narrow range 3000–4000 km/s. The orbital radii for the binary supermassive
black holes also lie in a narrow range, 1017–1018 cm, providing evidence that observed prominent examples of active galactic nuclei are fairly close binary systems. The parameters
of the mediumin which the components of the binary systems are moving are estimated, as well as the rates at which the systems
are losing orbital angular momentum and their lifetimes to coalescence. 相似文献
9.
A. D. Dolgov 《Astronomy Reports》2017,61(4):275-280
Astronomical observations of last few years have presented a surprising evidence that the Universe at redshift of order 10 is densely populated by supermassive black holes (quasars), supernovae, and contains very large amount of dust. All these data are in conflict with the canonical theory of quasar and supernova formation. A model is discussed which in a simple and natural way solves all these problem. In addition it explains an existence of supermassive black holes in each large galaxy and even in small ones. An inverted picture of galaxy formation is suggested when primordial black holes serve as seeds of galaxy formation. Simultaneously the origin and properties of black hole binaries, sources of gravitational waves registered by LIGO are explained. As a by-product the model may lead to abundant cosmological antimatter even in the Galaxy. 相似文献
10.
The possible influence of galactic interaction on the formation and growth of supermassive black holes in their nuclei and
the dynamics of their circumnuclear regions are considered, based on new data from the updated Vorontsov-Velyaminov catalog
of interacting galaxies and modern estimates of the masses of supermassive black holes. A sample of interacting galaxies with
known black-hole masses is created, and the dependence of the masses of the central black holes on the absolute B magnitudes and central stellar velocity dispersions in the host galaxy derived for this sample. A statistical analysis of
the sample shows that the black-hole masses in interacting galaxies satisfy the same mass-velocity dispersion relation as
non-interacting galaxies. A higher mass dispersion is characteristic of merging pairs than for galaxies that interact in other
ways. The maximum masses of the central black holes are observed in radio galaxies. 相似文献
11.
The spins of supermassive black holes in FR I and FR II radio galaxies are estimated using two models for the generation of the relativisitic jets, based on the Blandford–Znajek and Blandford–Payne mechanisms: the hybrid model of Meier and a flux-trapping model. The magnetic field at the event horizon is estimated assuming equipartition between the energy densities of the magnetic field and the accreting material. The magnetic field near the inner edge of the accretion disk is estimated assuming equipartition between the magnetic pressure and the radiation pressure, and also assuming proportionality between the magnetic field and the spin. In the case of FR I objects, both mechanisms for the generation of the jets (the hybrid model of Meier and a flux-trapping model) are efficient. For the FR II objects, equipartition between the energy densities of the magnetic field and the accretion flow facilitates stronger retrograde rotation of the supermassive black hole. Plots of spin versus mass suggest a predominantly chaotic character for the accretion in both types of radio galaxies. 相似文献
12.
A model for the formation of supermassive black holes at the center of a cluster of primordial black holes is developed. It is assumed that ～10?3 of the mass of the Universe consists of compact clusters of primordial black holes that arose as a result of phase transitions in the early Universe. These clusters also serve as centers for the condensation of dark matter. The formation of protogalaxies with masses of the order of 2 × 108 M ⊙ at redshift z = 15 containing clusters of black holes is investigated. The nuclei of these protogalaxies contain central black holes with masses ～105 M ⊙, and the protogalaxies themselves resemble dwarf spherical galaxies with their maximum density at their centers. Subsequent merging of these induced protogalaxies with ordinary halos of dark matter leads to the standard picture for the formation of the large-scale structure of the Universe. The merging of the primordial black holes leads to the formation of supermassive black holes in galactic nuclei and produces the observed correlation between the mass of the central black hole and the bulge velocity dispersion. 相似文献
13.
A. M. Cherepashchuk 《Astronomy Reports》2017,61(4):265-274
After 50 years of observational studies of black holes, great progress has been achieved in this branch of astrophysics. Several dozen stellar-mass black holes have been discovered in X-ray binaries, and several hundred supermassive black holes in galactic nuclei. The remarkable recent discovery of gravitational waves from merging black holes in a binary system by LIGO marks the beginning of a new stage in black-hole research. It is quite possible that gravitational-wave studies will provide definitive evidence for the existence of event horizons in black holes in the near future. On the other hand, the development of methods for space and ground-based radio-interferometry observations provides hope that it will be possible to obtain images of “shadows” of supermassive black holes in galactic nuclei, and to observe directly processes occurring in the vicinities of the event horizons of supermassive black holes. This is important for tests of general relativity in extremely strong gravitational fields. 相似文献
14.
N. A. Silant’ev Yu. N. Gnedin M. Yu. Piotrovich S. D. Buliga T. M. Natsvlishvili 《Astronomy Reports》2014,58(2):63-70
Two mechanisms for the formation of polarized radiation in Active Galactic Nuclei and quasars are considered-synchrotron radiation from a jet and the emergence of radiation from a magnetized, optically thick accretion disk (the Milne problem in a magnetized atmosphere). These mechanisms are applied to the polarization of objects studied in [1]. We have shown that the polarization of some sources cannot be explained as synchrotron radiation. The second mechanism is more general and, in principle, can be applied to the polarized radiation of all the sources in [1]. 相似文献
15.
Two series of 22.2 and 36.8-GHz observations of 43 GHz-Peaked Spectrum (GPS) radio sources from the Planck survey have been carried out using the 22-m radio telescope of the Crimean Astrophysical Observatory in 2014–2015, with the aim of studying the variability of these sources. The interval between the two series of observations was about nine months. These data were analyzed together with the Planck data at frequencies from 20 to 143 GHz. The fraction of quasars among GPS sources grows to 90% at millimeter wavelengths, compared to 1.4% at decimeter wavelengths. The growth in the variability indices of Planck GPS sources is not as sharp as that observed at decimeter and centimeter wavelengths, and remains at a level of about 30% at millimeter wavelengths. This supports the view that GPS sources are not strongly variable, compared to other types of Active Galactic Nuclei (AGNs). A mean spectrumfor the GPS radio sources has been obtained, which is shallower at low frequencies and steeper at high frequencies atmillimeter wavelengths than at decimeter and centimeterwavelengths. These properties of the GPS spectra at millimeter wavelengths testify to the compactness of these sources and the dense, inhomogeneous nature of the medium in which they are located. This also indirectly suggests that these objects are young and that their active states have short lifetimes. 相似文献
16.
We describe and compare methods for reducing radio circular-polarization data for Active Galactic Nuclei on parsec (VLBI) scales, and present results derived by applying these methods to 15 GHz observations of 29 AGN obtained on the Very Long Baseline Array. Circular polarization was detected in six of these objects, with characteristic degrees of several tenths of a percent. According to results obtained in other studies and the new results presented here, the most probable mechanism for the formation of the circular polarization is Faraday conversion of linear polarization when the radio emission passes through a magnetized plasma. For the objects OJ 287, 1334-127, and 3C 279, which were observed at several epochs, we find a constant degree and sign of the circular polarization on time scales of several years, testifying to the presence of stable ordered magnetic fields in the corresponding regions. 相似文献
17.
Data from long-term multi-frequency monitoring of the Active Galactic Nucleus (AGN) and blazar 3C 454.3 are analyzed. An unusually prolonged outburst in 2013–2017 had a duration that was twice the possible orbital period of the companion of the supermassive black hole (SMBH) located at the center of the host galaxy. It is proposed that the shape and duration of this outburst in 3C 454.3 could be the result of a coincidence between the plane of the accretion disk (AD) and the orbital plane of the companion. As a consequence, a prolonged energy release with enhanced intensity can be observed as the companion passes through the dense medium of the AD of the central SMBH. The presence of a 1.55-year orbital period in the variations of the emission of 3C 454.3 during this outburst also supports this hypothesis, as opposed to the possibility that the outburst was due to variations in γ and the Doppler factor. Small-scale flux-density fluctuations can arise during the outburst due to matter inhomogeneities with characteristic scales of about 1015 cm or more in the AD of the central SMBH and surrounding areas. 相似文献
18.
We have estimated the masses of the central supermassive black holes of 2442 radio galaxies froma catalog compiled using data
from the NED, SDSS, and CATS databases. Mass estimates based on optical photometry and radio data are compared. Relationships
between the mass of the central black hole M
p
bh
and the redshift z
p
are constructed for both wavelength ranges. The distribution of the galaxies in these diagrams and systematic effects influencing
estimation of the black-hole parameters are discussed. Upperenvelope cubic regression fits are obtained using the maximum
estimates of the black-hole masses. The optical and radio upper envelopes show similar behavior, and have very similar peaks
in position, z
p
≅ 1.9, and amplitude, log M
p/bh
= 9.4. This is consistent with a model in which the growth of the supermassive black holes is self-regulating, with this
redshift corresponding to the epoch when the accretion-flow phase begins to end and the nuclear activity falls off. 相似文献
19.
A. E. Vol’vach A. M. Kutkin M. G. Larionov L. N. Vol’vach A. Lahteenmaki M. Tornikoski J. Tammi J. Léon-Tavares E. Järvelä M. F. Aller H. D. Aller 《Astronomy Reports》2013,57(1):46-51
We present an analysis of data from multi-frequency monitoring of the blazar 3C 454.3 in 2010–2012, when the source experienced an unusually prolonged flare with a duration of about two years. This corresponds to the orbital period of the companion in a scenario in which two supermassive black holes are present in the nucleus of 3C 454.3. The flare’s shape, duration, and amplitude can be explained as a result of precession, if the plane of the accretion disk and the orbital plane of the binary are coincident. We detected small-scale structure of the flare, on time scales of no more than a month. These features probably correspond to inhomogeneities in the accretion disk and surrounding regions, with sizes of the order of 1015 cm. We estimated the size of the accretion disk based on the dynamical and geometrical parameters of this binary system: its diameter is comparable to the size of the orbit of the supermassive binary black hole, and its thickness does not exceed the gravitational radius of the central black hole. The presence of characteristic small-scale features during the flare makes it possible to estimate the relative time delays of variations in different spectral ranges: from gamma-ray to millimeter wavelengths. 相似文献
20.
Motivated by currently available direct observations of occulting tori in Seyfert galaxies and ongoing discussions about tori as important structural components in Active Galactic Nuclei, we discuss the possibility that the “spinning up” of a torus by radiation or winds could transform it into a dipolar toroidal vortex. The vortex motion balances the torus’ self-gravitation, and can explain the existence of cool, thick tori inferred from observations. In turn, the toroidal vortex can be a source of matter to feed the accretion disk. The resulting instability could result in flares accompanied by the ejection of matter. Our numerical estimates of the model parameters for luminosities close to the Eddington limit are consistent with the observational data. 相似文献