Early Observations of Black Holes

2020 ◽  
pp. 58-71
Author(s):  
John W. Moffat
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Binary Systems ◽  
Theoretical Models ◽  
Supermassive Black Holes ◽  
Spectral Lines ◽  
Current Evidence ◽  
X Rays ◽  
Electromagnetic Processes

Early observations of black holes, before the LIGO/Virgo detection of gravitational waves, were made by observing electromagnetic processes involving atomic spectral lines. X-ray binary systems were observed consisting of a progenitor star such as a neutron star and a dark companion. X-rays emitted from the gas accreting the dark companion tells us whether it is a black hole. Evidence indicated supermassive black holes at the centers of galaxies. From observations of orbits of stars near the supermassive black holes, one could determine their masses, which proved they were black holes. Observations of quasars, among the brightest objects in the universe, showed they contain black holes. It is important to establish the existence of an event horizon with the black hole, as predicted by general relativity. The current evidence for the event horizon is circumstantial, based on controversial theoretical models about the accretion disks surrounding the collapsed dark objects.

scholarly journals The Multiwavelength AGN Population and the X-ray Background

2013 ◽  
Vol 9 (S304) ◽  
pp. 188-194
Author(s):  
Ezequiel Treister ◽  
Claudia M. Urry ◽  
Kevin Schawinski ◽  
Brooke D. Simmons ◽  
Priyamvada Natarajan ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mass Density ◽  
Large Fraction ◽  
Supermassive Black Holes ◽  
X Rays ◽  
X Ray ◽  
Black Hole Growth ◽  
Hole Growth ◽  
X Ray Background

AbstractIn order to fully understand galaxy formation we need to know when in the cosmic history are supermassive black holes (SMBHs) growing more intensively, in what type of galaxies this growth is happening and what fraction of these sources are invisible at most wavelengths due to obscuration. Active Galactic Nuclei (AGN) population synthesis models that can explain the spectral shape and intensity of the cosmic X-ray background (CXRB) indicate that most of the SMBH growth occurs in moderate-luminosity (LX~ 1044 erg/s) sources (Seyfert-type AGN), at z~ 0.5−1 and in heavily obscured but Compton-thin, NH~ 1023cm−2, systems. However, this is not the complete history, as a large fraction of black hole growth does not emit significantly in X-rays either due to obscuration, intrinsic low luminosities or large distances. The integrated intensity at high energies indicates that a significant fraction of the total black hole growth, 22%, occurs in heavily-obscured systems that are not individually detected in even the deepest X-ray observations. We further investigate the AGN triggering mechanism as a function of bolometric luminosity, finding evidence for a strong connection between significant black hole growth events and major galaxy mergers from z~ 0 to z~ 3, while less spectacular but longer accretion episodes are most likely due to other (stochastic) processes. AGN activity triggered by major galaxies is responsible for ~60% of the total black hole growth. Finally, we constrain the total accreted mass density in supermassive black holes at z > 6, inferred via the upper limit derived from the integrated X-ray emission from a sample of photometrically selected galaxy candidates. We estimate an accreted mass density <1000 M⊙Mpc−3 at z~ 6, significantly lower than the previous predictions from some existing models of early black hole growth and earlier prior observations.

scholarly journals Mass Functions of Supermassive Black Holes across Cosmic Time

2012 ◽  
Vol 2012 ◽  
pp. 1-21 ◽  
Author(s):  
Brandon C. Kelly ◽  
Andrea Merloni
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmic Time ◽  
Theoretical Models ◽  
Mass Function ◽  
Supermassive Black Holes ◽  
Future Research ◽  
Black Hole Mass ◽  
Advantages And Disadvantages ◽  
Mass Functions

The black hole mass function of supermassive black holes describes the evolution of the distribution of black hole mass. It is one of the primary empirical tools available for mapping the growth of supermassive black holes and for constraining theoretical models of their evolution. In this paper, we discuss methods for estimating the black hole mass function, including their advantages and disadvantages. We also review the results of using these methods for estimating the mass function of both active and inactive black holes. In addition, we review current theoretical models for the growth of supermassive black holes that predict the black hole mass function. We conclude with a discussion of directions for future research which will lead to improvement in both empirical and theoretical determinations of the mass function of supermassive black holes.

scholarly journals Inventory of black hole binaries

2003 ◽  
Vol 212 ◽  
pp. 365-371 ◽  
Author(s):  
Jerome A. Orosz
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Binary Systems ◽  
Compact Object ◽  
X Rays ◽  
Optical Studies ◽  
Dynamical Mass ◽  
X Ray ◽  
Black Hole Binaries ◽  
X Ray Binaries

A small group of X-ray binaries currently provides the best evidence for the existence of stellar-mass black holes. These objects are interacting binary systems where the X-rays arise from accretion of material onto a compact object (i.e., an object with a radius of less than a few hundred km). In some favourable cases, optical studies of the companion star lead to dynamical mass estimates for both components. In 17 cases, the mass of the compact object in an X-ray binary has been shown to exceed the maximum mass of a stable neutron star (about 3 M⊙), which leads to the conclusion that these objects are black holes. In this contribution I will review the basic properties of these black hole binaries.

Supermassive Black Holes

2019 ◽  
pp. 151-158
Author(s):  
Nicholas Mee
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Supermassive Black Holes ◽  
Radio Telescopes ◽  
Event Horizons ◽  
Supermassive Black Hole

The Event Horizon Telescope (EHT) is aiming to image the event horizon of the supermassive black hole at the centre of our galaxy. Andrea Ghez has mapped out the orbits of stars around this supermassive black hole and deduced it has a mass of four million Suns. An even bigger supermassive black hole of six billion solar masses lies at the centre of the M87 Galaxy. Shep Doeleman has marshalled several of the world’s radio telescopes to form the EHT with the aim of imaging the event horizons of these black holes.

scholarly journals Properties of Black Holes Relevant to their Observation

1974 ◽  
Vol 64 ◽  
pp. 132-144 ◽  
Author(s):  
James M. Bardeen
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Hot Spots ◽  
Binary Systems ◽  
X Rays ◽  
Circular Orbits ◽  
Spacetime Geometry ◽  
Inertial Frames ◽  
Physical Effects

Black holes are very small objects by astronomical standards, so in many circumstances they interact with their surroundings like a Newtonian mass point. However, if black holes are present in X-ray binary systems, the X-rays emitted in the inner part of the accretion disk probe the highly curved spacetime geometry near the horizon, particularly if the black hole is rapidly rotating. Some of the properties of circular orbits near the black hole are quite sensitive to the amount of angular momentum. The relativistic corrections remove a Newtonian degeneracy between several of the characteristic frequencies associated with perturbations of the circular orbits.Hot spots in the inner part of the disk can produce dramatic fluctuations in intensity, since the frequency shifts of photons emitted by a given point on the disk are strongly time-dependent. The bending of the photon trajectories by the strong gravitational field can drastically affect the energy balance of the disk; much of the radiation emitted by the inner part of the disk is reabsorbed. The dragging of inertial frames by the angular momentum of the black hole can have striking consequences for the structure of the disk at quite large radii if the angular momentum of the accreting matter is not in the same direction as the angular momentum of the black hole.Dynamic perturbations of black holes are now being intensively studied to see if there are any surprising physical effects associated with the rotation of the black hole. Unfortunately, though quite interesting methods of extracting energy from the black hole exist in principle most of them are unlikely to be realized to an important extent in the real astrophysical world.

scholarly journals Epicyclic Oscillations around Simpson–Visser Regular Black Holes and Wormholes

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 279
Author(s):  
Zdeněk Stuchlík ◽  
Jaroslav Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Observational Data ◽  
High Frequency ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Periodic Oscillations ◽  
High Length ◽  
Circular Geodesic

We study epicyclic oscillatory motion along circular geodesics of the Simpson–Visser meta-geometry describing in a unique way regular black-bounce black holes and reflection-symmetric wormholes by using a length parameter l. We give the frequencies of the orbital and epicyclic motion in a Keplerian disc with inner edge at the innermost circular geodesic located above the black hole outer horizon or on the our side of the wormhole. We use these frequencies in the epicyclic resonance version of the so-called geodesic models of high-frequency quasi-periodic oscillations (HF QPOs) observed in microquasars and around supermassive black holes in active galactic nuclei to test the ability of this meta-geometry to improve the fitting of HF QPOs observational data from the surrounding of supermassive black holes. We demonstrate that this is really possible for wormholes with sufficiently high length parameter l.

scholarly journals The ecology of the galactic centre: Nuclear stellar clusters and supermassive black holes

2019 ◽  
Vol 14 (S351) ◽  
pp. 80-83 ◽  
Author(s):  
Melvyn B. Davies ◽  
Abbas Askar ◽  
Ross P. Church
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Fraction ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Multiple Clusters

AbstractSupermassive black holes are found in most galactic nuclei. A large fraction of these nuclei also contain a nuclear stellar cluster surrounding the black hole. Here we consider the idea that the nuclear stellar cluster formed first and that the supermassive black hole grew later. In particular we consider the merger of three stellar clusters to form a nuclear stellar cluster, where some of these clusters contain a single intermediate-mass black hole (IMBH). In the cases where multiple clusters contain IMBHs, we discuss whether the black holes are likely to merge and whether such mergers are likely to result in the ejection of the merged black hole from the nuclear stellar cluster. In some cases, no supermassive black hole will form as any merger product is not retained. This is a natural pathway to explain those galactic nuclei that contain a nuclear stellar cluster but apparently lack a supermassive black hole; M33 being a nearby example. Alternatively, if an IMBH merger product is retained within the nuclear stellar cluster, it may subsequently grow, e.g. via the tidal disruption of stars, to form a supermassive black hole.

Numerical simulation of the disk dynamics around the black hole: Bondi–Hoyle accretion

2014 ◽  
Vol 29 (21) ◽  
pp. 1450115
Author(s):  
Fahrettin Koyuncu ◽  
Orhan Dönmez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mach Number ◽  
Initial Conditions ◽  
Outer Boundary ◽  
Compact Objects ◽  
Adiabatic Index ◽  
Computational Domain ◽  
X Rays ◽  
Flip Flop

We have solved the General Relativistic Hydrodynamic (GRH) equations using the high resolution shock capturing scheme (HRSCS) to find out the dependency of the disk dynamics to the Mach number, adiabatic index, the black hole rotation parameter and the outer boundary of the computational domain around the non-rotating and rotating black holes. We inject the gas to computational domain at upstream and downstream regions at the same time with different initial conditions. It is found that variety of the mass accretion rates and shock cone structures strongly depend on Mach number and adiabatic index of the gas. The shock cones on the accretion disk are important physical mechanisms to trap existing oscillation modes, thereupon these trapped modes may generate strong X-rays observed by different X-ray satellites. Besides, our numerical approach also show that the shock cones produces the flip–flop oscillation around the black holes. The flip–flop instabilities which are monitored in our simulations may explain the erratic spin behavior of the compact objects (the black holes and neutron stars) seen from observed data.

scholarly journals Supermassive black holes surrounded by dark matter modeled as anisotropic fluid: epicyclic oscillations and their fitting to observed QPOs

2021 ◽  
Vol 2021 (11) ◽  
pp. 059
Author(s):  
Z. Stuchlík ◽  
J. Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Black Hole Spacetimes ◽  
Test Particles

Abstract Recently introduced exact solution of the Einstein gravity coupled minimally to an anisotropic fluid representing dark matter can well represent supermassive black holes in galactic nuclei with realistic distribution of dark matter around the black hole, given by the Hernquist-like density distribution. For these fluid-hairy black hole spacetimes, properties of the gravitational radiation, quasinormal ringing, and optical phenomena were studied, giving interesting results. Here, using the range of physical parameters of these spacetimes allowing for their relevance in astrophysics, we study the epicyclic oscillatory motion of test particles in these spacetimes. The frequencies of the orbital and epicyclic motion are applied in the epicyclic resonance variant of the geodesic model of quasiperiodic oscillations (QPOs) observed in active galactic nuclei to demonstrate the possibility to solve the cases where the standard vacuum black hole spacetimes are not allowing for explanation of the observed data. We demonstrate that the geodesic model can explain the QPOs observed in most of the active galactic nuclei for the fluid-hairy black holes with reasonable halo parameters.

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