2.9. Microlens mapping of disks in active galactic nuclei

1998 ◽  
Vol 184 ◽  
pp. 75-76 ◽  
Author(s):  
A. Yonehara ◽  
S. Mineshige ◽  
J. Fukue ◽  
M. Umemura ◽  
E.L. Turner
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Central Region ◽  
Galactic Nuclei ◽  
Direct Information ◽  
Supermassive Black Hole ◽  
Disk Size

Generally, it is believed that there is a supermassive black hole and a surrounding accretion disk in a central region of active galactic nuclei (AGN). However, it is quite difficult to obtain direct information about the center of AGN, because the accretion disk size is far too small to resolve.

Determination of supermassive black hole spins in active galactic nuclei

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040054
Author(s):  
M. Yu. Piotrovich ◽  
V. L. Afanasiev ◽  
S. D. Buliga ◽  
T. M. Natsvlishvili
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Disk Model ◽  
Supermassive Black Hole

Based on spectropolarimetry for a number of active galactic nuclei in Seyfert 1 type galaxies observed with the 6-m BTA telescope, we have estimated the spins of the supermassive black holes at the centers of these galaxies. We have determined the spins based on the standard Shakura-Sunyaev accretion disk model. More than 70% of the investigated active galactic nuclei are shown to have Kerr supermassive black holes with a dimensionless spin greater than 0.9.

scholarly journals Numerical Studies of Astrophysical Objects at Fesenkov Astrophysical Institute (FAI)

2018 ◽  
Vol 2 (1) ◽  
pp. 124-134
Author(s):  
Assylkhan Bibossinov ◽  
◽  
Denis Yurin ◽  
Chingis Omarov ◽  
◽  
...  
Keyword(s):  
Black Hole ◽  
Numerical Simulations ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Large Scale ◽  
International Workshop ◽  
Star Clusters ◽  
Galactic Nuclei ◽  
Numerical Studies ◽  
Astrophysical Objects

Numerical studies of astrophysical objects are a relatively new direction in Fesenkov Astrophysical Institute (FAI) and is mainly represented by the Laboratory of Cosmology, Stellar Dynamics and Computational Astrophysics. The lab seeks to understand the evolution of gravitating systems at various scales – from star clusters to galaxies to large-scale structure of the universe as a whole, and tackles these problems both through analytical methods and through numerical simulations. The particular focus is on numerical simulations of star clusters, especially those found in active galactic nuclei – this is a topic of oldestablished collaboration with colleagues from Astronomisches Rechen-Institut (Heidelberg) and National Astronomical Observatories of China (Beijing). The prominent example is STARDISK project dedicated to the numerical research of active galactic nuclei as multicomponent systems composed of compact stellar cluster, gaseous accretion disk and a supermassive black hole. It is demonstrated that an accretion disk can noticeably decelerate stars and thus enhance the accretion rate onto the black hole. In 2013 FAI hosted the MODEST-13 International Workshop dedicated to modeling of star clusters. Recently a new project has been approved aimed at construction of triaxial equilibrium N-body systems that can be of great help in various numerical experiments with disk galaxies. There are also long standing plans to perform cosmological simulations of large scale structures to test a new approach to dark matter and energy actively developed at FAI. For numerical calculations, FAI has a small, but growing computer cluster consisting of several high-performance computing servers equipped with computational GPU cards.

scholarly journals Dynamical Evolution of Accretion Flow onto a Black Hole

1998 ◽  
Vol 188 ◽  
pp. 455-456
Author(s):  
M. Yokosawa
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Event Horizon ◽  
Accretion Disk ◽  
Dynamical Evolution ◽  
Galactic Nuclei ◽  
Thick Disk ◽  
X Ray ◽  
General Relativistic ◽  
Inner Region

Active galactic nuclei(AGN) produce many type of active phenomena, powerful X-ray emission, UV hump, narrow beam ejection, gamma-ray emission. Energy of these phenomena is thought to be brought out binding energy between a black hole and surrounding matter. What condition around a black hole produces many type of active phenomena? We investigated dynamical evolution of accretion flow onto a black hole by using a general-relativistic, hydrodynamic code which contains a viscosity based on the alpha-model. We find three types of flow's pattern, depending on thickness of accretion disk. In a case of the thin disk with a thickness less than the radius of the event horizon at the vicinity of a marginally stable orbit, the accreting flow through a surface of the marginally stable orbit becomes thinner due to additional cooling caused by a general-relativistic Roche-lobe overflow and horizontal advection of heat. An accretion disk with a middle thickness, 2rh≤h≤ 3rh, divides into two flows: the upper region of the accreting flow expands into the atmosphere of the black hole, and the inner region of the flow becomes thinner, smoothly accreting onto the black hole. The expansion of the flow generates a dynamically violent structure around the event horizon. The kinetic energy of the violent motion becomes equivalent to the thermal energy of the accreting disk. The shock heating due to violent motion produces a thermally driven wind which flows through the atmosphere above the accretion disk. A very thick disk, 4rh≤h,forms a narrow beam whose energy is largely supplied from hot region generated by shock wave. The accretion flowing through the thick disk,h≥ 2rh, cannot only form a single, laminar flow falling into the black hole, but also produces turbulent-like structure above the event horizon. The middle disk may possibly emit the X-ray radiation observed in active galactic nuclei. The thin disk may produce UV hump of Seyfert galaxy. Thick disk may produce a jet observed in radio galaxy. The thickness of the disk is determined by accretion rate, such ashκ κes/cṁf(r) κ 10rhṁf(r), at the inner region of the disk where the radiation pressure dominates over the gas pressure. Here, Ṁ is the accretion rate and ṁ is the normarized one by the critical-mass flux of the Eddington limit. κesandcare the opacity by electron scattering and the velocity of light.f(r) is a function with a value of unity far from the hole.

scholarly journals Structure and Emission Line Spectrum of an X-ray Heated Accretion Disk in AGN

1994 ◽  
Vol 159 ◽  
pp. 484-484
Author(s):  
Yuan-Kuen Ko ◽  
Timothy R. Kallman
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Line Emission ◽  
Galactic Nuclei ◽  
X Ray ◽  
Disk Size ◽  
Emission Line Spectrum ◽  
Self Gravity ◽  
A Site

We investigate the structure of an X-ray heated accretion disk in active galactic nuclei. It is found that X-ray heating can prevent the disk to be disrupted by its self-gravity under sufficient X-ray heating. The disk size can be two orders of magnitute larger than that limited by self-gravity of the disk without X-ray heating. An accretion disk corona will be formed by X-ray heating and can be a site for line emission. We present such emission line spectra which range from optical to hard X-ray energies and compare with the observational data.

scholarly journals General Relativistic Simulation of Jet Formation from Magnetized Accretion Disk

1997 ◽  
Vol 163 ◽  
pp. 667-671
Author(s):  
Shinji Koide ◽  
Kazunari Shibata ◽  
Takahiro Kudoh
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Numerical Code ◽  
Jet Formation ◽  
Relativistic Jet ◽  
Relativistic Regime ◽  
General Relativistic

AbstractRecently, superluminal motions are observed not only from active galactic nuclei but also in our Galaxy. These phenomena are explained as relativistic jets propagating almost toward us with Lorentz factor more than 2. For the formation of such a relativistic jet, magnetically driven mechanism around a black hole is most promising. We have extended the 2.5D Newtonian MHD jet model (Shibata & Uchida 1986) to general relativistic regime. For this purpose, we have developed a general relativistic magnetohydrodynamic (GRMHD) numerical code and applied it to the simulation of the magnetized accretion disk around a black hole. We have found the formation of magnetically driven jets with 86 percent of light velocity (i.e. Lorentz factor ~ 2.0).

scholarly journals Estimating supermassive black hole masses in active galactic nuclei using polarization of broad Mg ii, H α, and H β lines

2020 ◽  
Vol 497 (3) ◽  
pp. 3047-3054
Author(s):  
Đorđe Savić ◽  
L Č Popović ◽  
E Shablovinskaya ◽  
V L Afanasiev
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Three Dimensional ◽  
Polarization Plane ◽  
Galactic Nuclei ◽  
Position Angle ◽  
Broad Line ◽  
Keplerian Motion ◽  
Supermassive Black Hole ◽  
Polarization Mechanism

ABSTRACT For type-1 active galactic nuclei (AGNs) for which the equatorial scattering is the dominant broad-line polarization mechanism, it is possible to measure the supermassive black hole (SMBH) mass by tracing the Keplerian motion across the polarization plane position angle φ. So far, this method has been used for 30 objects but only for H α emission line. We explore the possibilities of this method for determining SMBH masses using polarization in broad emission lines by applying it for the first time to Mg ii λ2798 Å spectral line. We use three-dimensional (3-D) Monte Carlo radiative transfer code stokes for simultaneous modelling of equatorial scattering of H α, H β, and Mg ii lines. We included vertical inflows and outflows in the Mg ii broad-line region (BLR). We find that polarization states of H α and H β lines are almost identical and SMBH-mass estimates differ by 7 per cent. For Mg ii line, we find that φ exhibits an additional ‘plateau’ with a constant φ, which deviates than the profiles expected for pure Keplerian motion. SMBH-mass estimates using Mg ii line are higher by up to 35 per cent than those obtained from H α and H β lines. Our model shows that for vertical inflows and outflows in the BLR that are higher or comparable to the Keplerian velocity, this method can be applied as a first approximation for obtaining SMBH mass.

Determination of supermassive black hole spins in local active galactic nuclei

2021 ◽  
Author(s):  
Mikhail Yu. Piotrovich ◽  
Stanislava D. Buliga ◽  
Tinatin M. Natsvlishvili
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Supermassive Black Hole
Sign in / Sign up

Export Citation Format

Share Document