scholarly journals Towards a Truly Unified Model of AGN: Aspect, Accretion and Evolution

1997 ◽  
Vol 14 (3) ◽  
pp. 230-245 ◽  
Author(s):  
Michael A. Dopita
Keyword(s):  
Black Holes ◽  
Dominant Role ◽  
Unified Model ◽  
Evolutionary Status ◽  
Massive Black Holes ◽  
Radio Jets ◽  
Line Region ◽  
Nuclear Regions ◽  
Diagnostic Capabilities ◽  
The Universe

AbstractThe Unified Model holds that the aspect-dependent effects primarily determine the nature of the active galactic nucleus that we observe. In this paper, I argue that three parameters; aspect, accretion rate into the nuclear regions, and the evolutionary status of the central black hole hold the key to unification. The mystery of why the epoch of quasar formation occurred so early in the evolution of the Universe, why radio-loud QSOs represent only a small fraction of the general population of QSOs, and why ellipticals are invariably the hosts of radio-loud active galaxies could be explained if (a) the most rapid growth of black holes occurred in galactic merger events, and if (b) an excess in the rate of nuclear feeding was able to choke off the radio jets, producing radio quiet QSOs. In this paper, I develop the idea that rate of nuclear feeding plays a dominant role and that feeding at super-Eddington rates into the broad-line region (BLR) during merger events is the means whereby massive black holes are grown. In particular, I develop a toy model for the radio-loud, radio-quiet dichotomy based on the rate of nuclear feeding, suggest an electron scattering model for the ‘big blue bump’ and its relation to the BLR, and emphasise the important diagnostic capabilities offered by analyses of the narrow line regions based on shock excitation models.

scholarly journals Gaseous Disks in the Nuclei of Elliptical Galaxies

1997 ◽  
Vol 163 ◽  
pp. 620-625 ◽  
Author(s):  
H. Ford ◽  
Z. Tsvetanov ◽  
L. Ferrarese ◽  
G. Kriss ◽  
W. Jaffe ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Elliptical Galaxies ◽  
Central Mass ◽  
Massive Black Holes ◽  
Radio Jets

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.

Reionization of the Universe by Early-formed Massive Black Holes

1996 ◽  
Vol 462 ◽  
pp. 104 ◽  
Author(s):  
Shin Sasaki ◽  
Masayuki Umemura
Keyword(s):  
Black Holes ◽  
Massive Black Holes ◽  
The Universe

scholarly journals How a Star’s Death Can Reveal a Black Hole

2022 ◽  
Vol 9 ◽  
Author(s):  
Iair Arcavi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Massive Black Holes ◽  
Know How ◽  
The Universe

Studying invisible objects in space that are hundreds of millions of light years away may sound impossible. But, in recent years, astronomers have developed a new way to investigate a type of invisible and distant objects—super-massive black holes. Black holes are the most densely packed objects in the Universe. When stars get close to super-massive black holes they can be torn apart, which produces a relatively brief but informative flash of light. These star-destroying events can help us to discover the locations of the most massive black holes in the Universe, but only if we know how to find and interpret them. In this article, we will discuss different ways we can “see” black holes, and particularly what we do and do not yet understand about stars getting “tidally disrupted” by them. Light YearThe distance light travels in a year, which is 5,878,625,370,000 miles.

scholarly journals What Physics Drives the Unified Model?

1999 ◽  
Vol 194 ◽  
pp. 199-207
Author(s):  
Michael A. Dopita
Keyword(s):  
Black Hole ◽  
Active Galactic Nucleus ◽  
Accretion Rate ◽  
Unified Model ◽  
Grand Unification ◽  
Evolutionary Status ◽  
Central Black Hole ◽  
Nuclear Regions

The Unified Model holds that the aspect-dependent effects primarily determine the apperance of the active galactic nucleus that we observe. However, additional parameters will be needed to fully unify the different tribes of AGN. Three parameters; aspect, accretion rate into the nuclear regions, and the evolutionary status of the central black hole probably hold the key to “grand” unification schemes.

Local heating of the universe by the Higgs field

2018 ◽  
Vol 27 (06) ◽  
pp. 1841003
Author(s):  
K. M. Belotsky ◽  
A. V. Grobov ◽  
S. G. Rubin
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Chemical Composition ◽  
Scalar Field ◽  
Local Heating ◽  
Dynamical Behavior ◽  
Higgs Field ◽  
Hole Formation ◽  
Massive Black Holes ◽  
The Universe

It is shown that the creation of primordial massive black holes is accompanied by a local heating of the matter. The developed mechanism is based on the interaction of the Higgs field and a scalar field responsible for black hole formation. We also consider dynamical behavior of parameters such as a scale and chemical composition of such heating regions.

Conference Summary

2017 ◽  
Vol 13 (S336) ◽  
pp. 451-454
Author(s):  
Philip J. Diamond
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
Interstellar Medium ◽  
Massive Black Holes ◽  
Conference Summary ◽  
Evolved Stars ◽  
The Universe

AbstractIAU Symposium 336, Astrophysical Masers: Unlocking the Mysteries of the Universe, took place between 4 - 8 September, 2017 in Cagliari, on the beautiful island of Sardinia. The Symposium, the fifth focusing on masers as a tool for astrophysics, was dedicated to our friend and colleague Malcolm Walmsley, who sadly passed away shortly before the meeting. To quote Karl Menten: “Malcolm made numerous fundamental contributions to our understanding of the physics and chemistry of star formation and the interstellar medium. He was an exceptional scientist, a highly esteemed colleague and a true gentleman”. Vale Malcolm. The topics discussed at the symposium covered a huge range, from star-formation, evolved stars, galaxies and their constituents, super-massive black-holes to cosmology.

scholarly journals Formation and early evolution of massive black holes

2006 ◽  
Vol 2 (S238) ◽  
pp. 73-82
Author(s):  
Piero Madau
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Ionization State ◽  
First Stars ◽  
Massive Black Holes ◽  
X Ray ◽  
Hard Radiation ◽  
Low Mass ◽  
The Universe

AbstractThe astrophysical processes that led to the formation of the first seed black holes and to their growth into the supermassive variety that powers bright quasars at z ∼ 6 are poorly understood. In standard ΛCDM hierarchical cosmologies, the earliest massive holes (MBHs) likely formed at redshift z ≳ 15 at the centers of low-mass (M ≳ 5 × 105 M⊙) dark matter “minihalos”, and produced hard radiation by accretion. FUV/X-ray photons from such “miniquasars” may have permeated the universe more uniformly than EUV radiation, reduced gas clumping, and changed the chemistry of primordial gas. The role of accreting seed black holes in determining the thermal and ionization state of the intergalactic medium depends on the amount of cold and dense gas that forms and gets retained in protogalaxies after the formation of the first stars. The highest resolution N-body simulation to date of Galactic substructure shows that subhalos below the atomic cooling mass were very inefficient at forming stars.

scholarly journals Co-Evolution of Supermassive Black Holes and Their Host Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 34-39
Author(s):  
J. K. Kotilainen ◽  
R. Decarli ◽  
R. Falomo ◽  
A. Treves ◽  
M. Labita ◽  
...  
Keyword(s):  
Black Holes ◽  
Stellar Population ◽  
High Redshift ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Massive Black Holes ◽  
Galaxy Masses ◽  
Age Of The Universe ◽  
Black Hole Masses ◽  
The Universe

AbstractWe study the evolution of the MBH/Mhost relation up to z = 3 for a sample of 96 quasars with known host galaxy luminosities. Black hole masses are estimated assuming virial equilibrium in the broad-line regions, while the host galaxy masses are inferred from their luminosities. With this data, we are able to pin down the evolution of the MBH/Mhost relation over 85% of the age of the universe. While the MBH/Lhost relation remains nearly unchanged, taking into account the aging of the stellar population, we find that the MBH/Mhost ratio (Γ) increases by a factor ~ 7 from z = 0 to z = 3. We show that the evolution of Γ is independent of radio loudness and quasar luminosity. We propose that the most massive black holes, in their quasar phase at high-redshift, become extremely rare objects in host galaxies of similar mass in the local universe.

scholarly journals Observational Signatures of High-Redshift Quasars and Local Relics of Black Hole Seeds

2016 ◽  
Vol 33 ◽  
Author(s):  
Amy E. Reines ◽  
Andrea Comastri
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Observational Constraints ◽  
Solar Mass ◽  
Massive Black Holes ◽  
Eddington Limit ◽  
The Universe ◽  
Review Current

AbstractObservational constraints on the birth and early evolution of massive black holes come from two extreme regimes. At high redshift, quasars signal the rapid growth of billion-solar-mass black holes and indicate that these objects began remarkably heavy and/or accreted mass at rates above the Eddington limit. At low redshift, the smallest nuclear black holes known are found in dwarf galaxies and provide the most concrete limits on the mass of black hole seeds. Here, we review current observational work in these fields that together are critical for our understanding of the origin of massive black holes in the Universe.

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