scholarly journals Cosmological direct-collapse black hole formation sites hostile for their growth

2021 ◽  
Vol 502 (1) ◽  
pp. 700-713
Author(s):  
Sunmyon Chon ◽  
Takashi Hosokawa ◽  
Kazuyuki Omukai
Keyword(s):  
Black Hole ◽  
Relative Velocity ◽  
Accretion Rate ◽  
Galactic Centre ◽  
Analytic Estimate ◽  
The Galaxy ◽  
Enriched Environments ◽  
Supernova Feedback ◽  
Intense Star Formation

ABSTRACT The direct collapse (DC) is a promising mechanism that provides massive seed black holes (BHs) with ∼105 M⊙ in the early universe. To study a long-term accretion growth of a direct-collapse black hole (DCBH), we perform cosmological radiation-hydrodynamics simulations, extending our previous work where we investigated its formation stage. With a high spatial resolution down below the Bondi radius, we show that the accretion rate on to the BH is far below the Eddington value. Such slow mass growth is partly because of the strong radiative feedback from the accreting BH to the surrounding dense gas. Even after it falls into the first galaxy, the accretion rate is substantially suppressed due to the supernova feedback associated with the intense star formation. Moreover, the BH has a large velocity of ∼100 km s−1 relative to the gas, which further reduces the accretion rate. This large relative velocity stems from the fact that the DCBHs form in metal-free environments typically at ∼1 kpc from the galaxy. The BH accelerates as it approaches the galactic centre due to the gravity. The relative velocity never damps and the BH wanders around the outer galactic region. An analytic estimate predicts that the DCBH formation within ∼100 pc around the galactic centre is necessary to decelerate the BH with dynamical friction before z = 7. Since metal enrichment with Z ∼ 10−5−10−3 Z⊙ is expected there, the formation of DCBHs in the metal-enriched environments is preferable for the subsequent rapid growth.

scholarly journals Dark matter heating of gas accreting onto Sgr A*

2019 ◽  
Vol 490 (3) ◽  
pp. 3414-3425 ◽  
Author(s):  
Elizabeth R Bennewitz ◽  
Cristian Gaidau ◽  
Thomas W Baumgarte ◽  
Stuart L Shapiro
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Steady State ◽  
Cross Sections ◽  
Accretion Rate ◽  
Supermassive Black Holes ◽  
Galactic Centre ◽  
Appreciable Effect ◽  
Sgr A

ABSTRACT We study effects of heating by dark matter (DM) annihilation on black hole gas accretion. We observe that, for reasonable assumptions about DM densities in spikes around supermassive black holes, as well as DM masses and annihilation cross-sections within the standard WIMP model, heating by DM annihilation may have an appreciable effect on the accretion on to Sgr A* in the Galactic Centre. Motivated by this observation we study the effects of such heating on Bondi accretion, i.e. spherically symmetric, steady-state Newtonian accretion on to a black hole. We consider different adiabatic indices for the gas, and different power-law exponents for the DM density profile. We find that typical transonic solutions with heating have a significantly reduced accretion rate. However, for many plausible parameters, transonic solutions do not exist, suggesting a breakdown of the underlying assumptions of steady-state Bondi accretion. Our findings indicate that heating by DM annihilation may play an important role in the accretion onto supermassive black holes at the centre of galaxies, and may help explain the low accretion rate observed for Sgr A*.

scholarly journals Galaxy Formation, Evolution and Rotation as a 4D Relativistic Cloud-World Embedded in a 4D Conformal Bulk: From String to Cloud Theory

2021 ◽  
Author(s):  
Mohammed Al-Fadhli
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Early Universe ◽  
Galaxy Formation ◽  
Positive Curvature ◽  
Recent Observation ◽  
Galactic Centre ◽  
Field Equations ◽  
The Galaxy ◽  
Gas Cloud

The recent observation of the G2 gas cloud orbit around the galactic centre has challenged the model of a mere supermassive black hole that should have destroyed it. In addition, the Planck Legacy 2018 (PL18) release has preferred a positively curved early Universe with a confidence level exceeding 99%. In this study, the formation of a galaxy from the collapse of a supermassive gas cloud in the early Universe is modelled based on extended field equations as a 4D relativistic cloud-world that flows and spins through a 4D conformal bulk of an initial positive curvature considering the preference of the PL18 release. Owning to the curved background, this scenario of galaxy formation reveals that the core of the galaxy undergoes a forced vortex formation with a central event horizon leading to opposite vortices (traversable wormholes) that are spatially shrinking through evolving in the conformal time. It indicates that the galaxy and its core are formed at the same process where the surrounding gas clouds form the spiral arms due to the frame-dragging induced by the fast-rotating core. Further, the bulk conformal curvature evolution demonstrates the fast orbital speed of outer stars owing to external fields exerted on galaxies as they travel through conformally curved space-time. Accordingly, the G2 gas cloud that only faced the drag effects could be explained if its orbit is around the vortex but at a distance from the central event horizon. These findings could explain the fast orbital speed of outer stars where the galaxy formation and its core simultaneously could explain the formation of the supermassive compact galaxy cores with a mass of ~109 M⊙ at just 6% of the current Universe age and thus could resolve the black hole hierarchy problem.

scholarly journals Galaxy Formation and Rotation as a 4D Relativistic Cloud-World Embedded in a 4D Conformal Background: A Cloud Theory

2021 ◽  
Author(s):  
Mohammed Al-Fadhli
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Early Universe ◽  
Galaxy Formation ◽  
Positive Curvature ◽  
Recent Observation ◽  
Galactic Centre ◽  
Field Equations ◽  
The Galaxy ◽  
Gas Cloud

The recent observation of the G2 gas cloud orbit around the galactic centre has challenged the model of a mere supermassive black hole at the centre of our galaxy which should have destroyed it. In addition, the Planck Legacy 2018 (PL18) release has preferred a positively curved early Universe with a confidence level exceeding 99%. In this study, the collapse of a large gas cloud in the early Universe to form a galaxy is modelled based on extended field equations as a 4D relativistic CloudWorld that flows and spins through a 4D independent conformal background of an initial positive curvature considering the preference of the PL18 release. Owning to the curved background, this scenario of galaxy formation indicates that the core of the galaxy undergoes a forced vortex formation with a central event horizon leading to opposite traversable wormholes that are spatially shrinking through the conformal time. It reveals that the galaxy and its core are formed at the same process where the surrounding gas clouds form the spiral arms due to the frame-dragging induced by the fast-rotating core. Accordingly, the G2 gas cloud that only faced the drag effects could be explained if its orbit is around the wormhole but at a distance from the central event horizon. The formation of the galaxy and its core simultaneously could explain the formation of the supermassive compact galaxy cores with a mass of ~109 M⊙ at just 6% of the current Universe age and could resolve the black hole hierarchy problem.

scholarly journals Prediction of the Black-Hole Mass in 3C 273 by Multiband Observations

2003 ◽  
Vol 214 ◽  
pp. 281-286
Author(s):  
Zhen Guo Ma ◽  
Xi Zhen Zhang
Keyword(s):  
Black Hole ◽  
Accretion Rate ◽  
Line Emission ◽  
Data Fitting ◽  
Physical Parameters ◽  
Black Hole Mass ◽  
X Ray ◽  
The Galaxy ◽  
Radio Band

With the determined black-hole (BH) spin of 3C 273 by data-fitting to the detected iron Kα line emission in the soft X-ray band, the BH mass of the galaxy is predicted by formulations of both the observed disk-luminosity in the optical-UV band and the observed jet-precession in the radio band. The multiband synthesis suggests that the BH is supermassive, 2.4 × 109M⊙. Simultaneously, other physical parameters are self-consistently obtained at the precessing radius of 230.2rg: the accretion rate of the disk is 74.9M⊙ yr−1, the Shakura-Sunyaev viscosity α is 0.134, and the radial & orbital velocities of fluid elements are 4.3 × 10−8 and 6.6 × 10−2, respectively.

scholarly journals Black hole shadows in Verlinde’s emergent gravity

2021 ◽  
Vol 503 (1) ◽  
pp. 1310-1318
Author(s):  
Kimet Jusufi ◽  
Saurabh
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Power Law ◽  
Free Fall ◽  
Galactic Centre ◽  
Baryonic Matter ◽  
Emergent Gravity ◽  
The Galaxy ◽  
Matter Effect ◽  
Baryonic Mass

ABSTRACT We study the effect of baryonic matter and apparent dark matter on black hole (BH) shadow in Verlinde’s emergent gravity. To do so, we consider different baryonic mass profiles and an optically-thin disc region described by a gas in a radial free fall around the BH. Assuming that most of the baryonic matter in the galaxy is located near the Galactic Centre surrounding a supermassive BH, we use two models of power law mass profile for the baryonic matter to study the effect of apparent dark matter on the shadow and the corresponding intensity. We find that the effect of the surrounding matter on the shadow size using observational values is small; however, it becomes significant when the surrounding baryonic matter increases. To this end, we show that the effect of simple power law function in the limit of constant baryonic mass in Verlinde’s theory implies an apparent dark matter effect that is similar to the standard gravity having an isothermal dark matter profile. We also find the intensity of the electromagnetic flux radiation depending on the surrounding mass.

scholarly journals Search for isolated Galactic Centre stellar mass black holes in the IR and sub-mm range

2019 ◽  
Vol 489 (2) ◽  
pp. 2038-2048 ◽  
Author(s):  
P B Ivanov ◽  
V N Lukash ◽  
S V Pilipenko ◽  
M S Pshirkov
Keyword(s):  
Black Holes ◽  
Accretion Rate ◽  
Quantitative Model ◽  
Galactic Centre ◽  
Comparable Amount ◽  
James Webb Space Telescope ◽  
The Galaxy ◽  
Infrared Spectral ◽  
Efficiency Parameter ◽  
Complicated Model

ABSTRACT We investigate a possibility to find an accreting isolated black hole (IBH) with mass 1–100 M⊙ within Central Galactic Molecular Zone in the submillimetre and infrared spectral range with help of planned space observatories James Webb Space Telescope (JWST) and Millimetron (MM). We assume the spherical mode of accretion. We develop the simplest possible quantitative model of the formation of radiation spectrum in this range due to synchrotron emission and show that it fully agrees with the more complicated model of Ipser and Price (1982) for expected values of accretion rate. If a substantial fraction of the Laser Interferometer Gravitational-Wave Observatory (LIGO) events was caused by merger of primordial black holes, the JWST would be able to find them provided that there is a cusp in distribution of dark matter in the Galaxy and that the accretion efficiency parameter λ defined as the ratio of accretion rate on to IBH to its Bondi–Hoyle–Lyttleton value is larger than ∼10−2. A comparable amount of IBHs is also predicted by recent models of their formation due to stellar evolution. MM capabilities are hampered by the effect of confusion due to distant submillimetre galaxies, but it can also be used for such purposes if the confusion effect is properly dealt with. In case of efficient accretion with λ ∼ 1, both instruments could detect IBHs even when their number densities are as low as 10−6 pc−3.

A numerical study of Galactic Centre stars

2020 ◽  
Vol 501 (2) ◽  
pp. 2418-2423
Author(s):  
Oscar Salcido ◽  
Carlos Calcaneo-Roldan
Keyword(s):  
Black Hole ◽  
Numerical Study ◽  
Semimajor Axis ◽  
Galactic Centre ◽  
Central Black Hole ◽  
Central Object ◽  
Galactic Potential ◽  
The Galaxy ◽  
Inner Parts ◽  
Strong Agreement

ABSTRACT We present a simulation of the orbits of Galactic Centre stars, also known as ‘S-stars’, with the purpose of describing the motion of those bodies for which complete orbits are known with greater accuracy. The aim is to have a better understanding of the inner parts of the Galactic potential. The simulation assumes that the spacetime around the central black hole of the Galaxy may be modelled by the Schwarzschild metric, while stellar interactions are approximated classically. We model the central object as a black hole with mass 4.31 × 106 M⊙, fix the Galactic Centre distance at R = 8.33 kpc and include 37 orbiting stars, all of which have masses of 10 M⊙, except for S2, which has a mass of 20 M⊙. Our method allows us to predict the semimajor axis, a; eccentricity, ϵ; and period, T for these stars and predict their periastron shift, δΘ. In particular for S2, the most scrutinized star, we find δΘ = 11.9342 arcmin, in strong agreement with the observed value.

scholarly journals Hypervelocity stars from star clusters hosting intermediate-mass black holes

2019 ◽  
Vol 489 (4) ◽  
pp. 4543-4556 ◽  
Author(s):  
Giacomo Fragione ◽  
Alessia Gualandris
Keyword(s):  
Black Hole ◽  
High Velocity ◽  
Globular Clusters ◽  
Galactic Centre ◽  
Galactic Latitude ◽  
Dark Halo ◽  
Intermediate Mass ◽  
Galactocentric Distance ◽  
Galactic Potential ◽  
The Galaxy

ABSTRACT Hypervelocity stars (HVSs) represent a unique population of stars in the Galaxy reflecting properties of the whole Galactic potential. Determining their origin is of fundamental importance to constrain the shape and mass of the dark halo. The leading scenario for the ejection of HVSs is an encounter with the supermassive black hole in the Galactic centre. However, new proper motions from the Gaia mission indicate that only the fastest HVSs can be traced back to the Galactic centre and the remaining stars originate in the disc or halo. In this paper, we study HVSs generated by encounters of stellar binaries with an intermediate-mass black hole (IMBH) in the core of a star cluster. For the first time, we model the effect of the cluster orbit in the Galactic potential on the observable properties of the ejected population. HVSs generated by this mechanism do not travel on radial orbits consistent with a Galactic centre origin, but rather point back to their parent cluster, thus providing observational evidence for the presence of an IMBH. We also model the ejection of high-velocity stars from the Galactic population of globular clusters, assuming that they all contain an IMBH, including the effects of the cluster’s orbit and propagation of the star in the Galactic potential up to detection. We find that high-velocity stars ejected by IMBHs have distinctive distributions in velocity, Galactocentric distance and Galactic latitude, which can be used to distinguish them from runaway stars and stars ejected from the Galactic Centre.

scholarly journals Satellite infall and mass deposition on the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 168-170
Author(s):  
S. C. Gallego ◽  
J. Cuadra
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Accretion Rate ◽  
Young Stars ◽  
Small Satellite ◽  
Supermassive Black Hole ◽  
The Past ◽  
Satellite Galaxy ◽  
The Galaxy

AbstractWe modeled numerically the infall of a small satellite galaxy on to the inner 200 parsec of our Galaxy, to test whether such an event perturbs gas orbiting in the central molecular zone (CMZ), as recently proposed by Lang et al. (2013). This process could have driven a large gas inflow around 10 Myr ago, explaining the past high accretion rate onto the supermassive black hole, and the presence of young stars in the inner parsecs of the Galaxy. Our simulations show a very small inflow of gas, not sufficient to produce the aforementioned effects.

scholarly journals Observational manifestations of accretion onto isolated black holes of different masses

2006 ◽  
Vol 2 (S238) ◽  
pp. 391-392
Author(s):  
Sergey Karpov ◽  
Gregory Beskin
Keyword(s):  
Black Holes ◽  
Molecular Cloud ◽  
Relative Velocity ◽  
Accretion Rate ◽  
Spherically Symmetric ◽  
X Ray ◽  
Significant Variability ◽  
Dense Molecular Cloud ◽  
The Galaxy

AbstractThe process of accretion onto the isolated black holes under the various conditions of the ISM and its observational manifestations are discussed. For the majority of the Galaxy volume the accretion rate is as low as 10−6–10−9 of Eddington one, and the accretion is spherically-symmetric. Such objects manifest itself as a weak optical and x-ray sources with featureless spectra and the significant variability of the emission.For the BH located inside the dense molecular cloud the regime of accretion depends on its massand velocity. A massive (100–1000M⊙) BH born in the cloud or having low relative velocity, may manifest itself as a ultra-luminous x-ray source (ULX).

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